Cells and Tissues Exam Prep PDF

**CELLS AND TISSUES -- Cell structure** - State that the structure of an organism and the way in which it functions result from the activities of all of its cells: - All living organisms are made up of cells and the materials produced by cells. - The structure of an orga...

**CELLS AND TISSUES -- Cell structure** - State that the structure of an organism and the way in which it functions result from the activities of all of its cells: - All living organisms are made up of cells and the materials produced by cells. - The structure of an organism and the way in which it functions result from the activities of all its cells - Define "organelle" - Structures within the cytoplasm of the cell, each with specific functions. - Identify, name and give the basic function of the following parts of a cell; cell membrane, cytoplasm, nucleus, nuclear membrane, mitochondria, ribosomes, smooth & rough endoplasmic reticulum, Golgi body, lysosomes, centrioles, cilia, flagellum, vesicles - Cell Membrane: - A membrane is basically a barrier. - Separates the cell from neighboring cells, creating a differential between internal and external environment. - Contains the organelles within the cell - **Selectively permeable -** Only certain substances can pass through (controls movement) - Cytoplasm: - A jelly-like material which fills all the space between the nucleus and the cell membrane. - Organelles are suspended within. - Allows chemical reactions to occur and provides shape to the cell. - Liquid part of cytoplasm is called **cytosol** and is mostly water but does contain substances, such as salts and carbohydrates dissolved within it. - Proteins and fats do not dissolve in the cytosol but are suspended within. - Nucleus - Contains the genetic material (DNA) of the cell. - Separated from the cytoplasm by its own double membrane (**nuclear membrane**) - Nuclear membrane contains holes, known as **nuclear pores**. Large molecules can enter and exit through these. - Inside the nucleus is the nucleolus. This contains RNA. - The DNA & Nucleolus are suspended in a jelly-like substance called **nucleoplasm.** - Ribosomes - Small, spherical organelles. - Amino acids are joined together to make proteins. - Can be freely suspended in cytoplasm or may be attached to endoplasmic reticulum. - Endoplasmic Reticulum - Parallel membranes that extend from cell membrane to nuclear membrane. - Provide a surface for chemical reactions. - The channels they form can be used for storage or transportation of molecules. - **Smooth ER** = No ribosomes attached - **Rough ER** = Ribosomes attached to membrane. - Golgi Body - Several flattened membranes stacked upon each other. - Usually found near the nucleus. - Modifies proteins (made at ribosomes) and packages them for secretion from the cell. - Packages proteins in little membrane surrounded bubbles, called vesicles. - Mitochondria - Sausage-shaped structures spread throughout the cytoplasm. - The chemical reactions for **cellular respiration** occur here. - Made from a **double membrane.** - Outer membrane is smooth and surrounds the mitochondrion. - Inner membrane folds to increase surface area for cellular respiration to occur. - Lysosomes - Small spheres formed from the Golgi body. - Contain digestive enzymes, able to break down large molecules. - Can join with vesicles within the cytoplasm and digest materials within. - Can also digest worn out organelles. - Vesicles - Small membrane bound sacs. - Transport material in, out, and within the cell. - Cilia & Flagella - Fine projections which can move the cell, or move substances over the surface of the cell. - If they are short, abundant, and like fine hairs, they are cilia. Found in lining of SI and Oesophagus. - If they are longer and there are only a few, they are flagella. Found on sperm cells. - Cytoskeleton - Cytoskeleton consists of microfilaments and microtubules that give the cell its shape. - Also assist with movement of materials within the cell, and movement of the cell itself. - **Centrioles** are pairs of cylindrical structures involved in the reproduction of the cell. - List the requirements of a cell including oxygen, carbohydrates, proteins, lipids, vitamins and minerals - All cells need a supply of: - Oxygen for cellular respiration (making energy) - Glucose for cellular respiration - Lipids - Vitamins & minerals - Carbohydrates - Proteins - All cells need removal of - Carbon dioxide - Water - Other wastes - Identify the fluid compartments within the body; intracellular fluid and extracellular fluids - The fluids that surround a cell are collectively called **extracellular fluid/tissue fluid.** - It is separated from the **intracellular fluid** by the cell membrane - **Homeostasis** is the maintenance of a constant environment. This is maintained in the extracellular fluid. - **CELLS AND TISSUES - Cell Transport** - List the functions of the cell membrane with an emphasis on transport of materials in/out of the cell - *[Physical Barrier -]* Between extracellular and intracellular fluid because both are composed of different concentration of substances - *[Regulation of movement of materials -]* Both into and out of the cell. - *[Sensitivity -]* Contains receptors that can respond to changes in the extracellular fluid very quickly. - *[Support -]* Internal part of cell membrane is attached to microfilaments of cytoskeleton. Membranes are also attached to membranes of adjacent cells supporting the tissue the cells are a part of. - Describe the structure of the cell membrane, in terms of the fluid mosaic model, phospholipid bilayer, membrane proteins (channel, carrier, recognition and receptor) and cholesterol - Main structure are **phospholipid** molecules. - Phospholipids are arranged in two layers known as a **bilayer** - Head that is **hydrophilic** - The tail is **hydrophobic** - Embedded in the cell membrane are cholesterol and protein molecules. - Cholesterol molecules are wedged between phospholipids. They make the membrane less permeable to very small water-soluble molecules that would otherwise freely cross. - Some protein molecules pass through membrane, while others are just bound to the surface. - Cell membrane proteins: - Receptor proteins: Respond to changes in extracellular fluid - Channel proteins: Water soluble substances are free to pass\ through - Carrier proteins: Bind to particular molecules allowing them\ passage through the membrane - Cell identity markers: Allow cells to recognise cells of the same tissue, Allow cells to recognise foreign invaders - State examples of cell inputs and outputs that enter/exit through the cell membrane and outline their importance to the cell. - Define what is meant by passive and active transport processes - [Passive] transport [does not] require energy and substances move [with] the concentration gradient - [Active] transport [does] require energy and substances move [against] the concentration gradient - Explain what 'differentially permeable' and 'concentration gradient' means - The cell membrane is differentially permeable (aka selectively permeable, semipermeable). - Permeable = allowing substances to pass through it. - Selectively permeable = allows certain substances through it, restricts movement of others. - The difference in concentration that brings about diffusion is known as a concentration gradient (diffusion gradient). - The greater the difference between the two concentrations, the faster the rate of diffusion. - Define simple diffusion and outline how it occurs across the cell membrane, either across the phospholipidbilayer or through channel proteins - Define metabolism. - the sum total of all the chemical reactions that occur in the cell. - Distinguish between catabolism and anabolism, and provide at least one example of each. - Catabolism - reactions where large molecules are broken down into smaller molecules. - Release energy - Cellular resp. - Anabolism - reactions where small molecules are joined together to form larger molecules. - Required energy - Protein synth. - Define and give examples of inorganic and organic molecules. - [Organic Molecules:] - Relatively larger molecules that are carbon-based, - sugars (glucose), proteins (amino acids), and fats (lipids). - [Inorganic Molecules:] - Relatively smaller molecules that are not carbon-based - water, carbon dioxide, oxygen, and ions (K+ & Na+). - Describe what affect enzymes have on a chemical reaction's activation energy. - Enzymes are biological catalysts. It lowers the activation energy. - Use the lock-and-key model (including the terms substrate, active site, enzyme-substrate complex, products) to explain how enzymes catalyse reactions. - The action of an enzyme is [specific], which means that they are involved in one specific chemical reaction, and the enzyme remains [unchanged] at the end of the reaction. - The molecules in which enzymes act on are called the [substrate]. As enzymes are specific, this also means that each enzyme will only combine with one particular substrate. - Hence, we use the lock-and-key model to explain how enzymes catalyse reactions. - List the factors that affect enzyme activity, and outline their effect - Concentration of enzyme - A higher concentration of enzymes mean that there will enzyme molecules that will come into contact with the reactants, which will increase the rate of reaction. - However, if the substate is limited, the rate of reaction will not change after reaching the highest possible point - Substrate concentration - there are more substrate molecules in the reaction that will come into contact with the enzyme molecules. - Rate of removal of products of the reaction - The products of the reaction must be continually removed to maintain the rate of reaction. - The build up of products will slow down the rate of reaction, as it becomes more difficult for the substrate molecules to be able to come into contact with the enzyme molecules. - Temperature - The rate of most chemical reactions increases as temperature increases, until an optimal temperature is reached. - When there is an increase in temperature, there is more kinetic energy, increasing the rate of reaction, but only within a limited temperature range. - When the temperature is beyond the optimum, the rate of reaction decreases as the enzymes become denatured and change shape. - pH - enzymes are sensitive to the pH of the medium in which a reaction is taking place. Outside of its pH tolerance an enzyme will denature and its active site will no longer be able to bind to substrates - Presence of cofactors and coenzymes - Description - cofactors and coenzymes change the shape of the active site, so that the enzyme can bind to the substrate. - Explanation - the binding of the cofactors and coenzymes help the enzyme build up or break down the substrates into products. Without the presence of cofactors and coenzymes, the enzyme molecule will still be intact but cannot function. - Cofactors - generally ions or inorganic molecules. - Coenzymes - generally vitamins or non-protein organic molecules. - Enzyme inhibitors - Competitive inhibitors: they join to the active site preventing the substrate from binding to the enzyme. - Non-competitive inhibitors - they bind to another area of the enzyme (allosteric site) other than the active site, which can cause the enzyme to change shape and affect the functioning of the active site - Define cellular respiration - cellular respiration is a chemical process in which molecules from food is broken down to release energy (ATP), that is stored in the chemical bonds. - Describe the role played by adenosine triphosphate (ATP) and adenosine diphosphate (ADP) in cellular respiration - - Recall the % of energy released during cellular respiration that forms ATP and is released as heat energy - 60% - Describe anaerobic respiration, in terms of its role within cellular respiration, where it occurs in the cell, when it occurs and the chemical steps that occur - Anaerobic process that does not require oxygen and occurs in the cytosol/cytoplasm of the cell. - Releases enough energy to convert 2 molecules of ADP to ATP. - If no oxygen becomes available, that pyruvic acid is converted into lactic acid in the cytosol. - Give the word equation for anaerobic respiration - Glucoselactic acid + 2ATP - Describe aerobic respiration, in terms of its role within cellular respiration, where it occurs in the cell, when it occurs and the chemical steps that occur - - Give the word and chemical equations for aerobic respiration - List examples of cell activities that require ATP - Describe the five main functions of the skeleton - - Define the term 'articulation' - The connection between 2 bones - Recall the five main types of bone and their functions - - State the functions of the axial skeleton, and name the bones of - The axial skeleton consists of the bones that lie around the central axis of the body. - It provides the main support for erect posture and protection of the central nervous system and the organs contained within the thorax. - The bones that form the skull, vertebral column, ribs and sternum (breastbone) make up the axial skeleton. - State the function of the appendicular skeleton, and name the bones of - The appendicular skeleton consists of the bones of the upper and lower limbs, the pectoral girdle (shoulder) and pelvic (hip) girdle. - These two girdles allow for the articulation of the limbs with the axial skeleton. - Identify the macroscopic parts of a long bone, including the diaphysis, epiphyses, yellow bone marrow, red bone marrow, periosteum, articular cartilage - - Distinguish between spongy bone tissue and compact bone tissue in terms of structure, location found in long bone and function - Describe the microscopic structure of compact bone tissue including osteon, osteocyte, Haversian/central canal, lamellae, lacunae, canaliculi - Describe the microscopic structure of spongy bone tissue including trabeculae - Describe the microscopic structure of cartilage tissue including chondrin, chondroblasts, chondrocytes - **Chondroblasts** -- immature cartilage cells that grow new cartilage by producing matrix. - **Chondrocytes**-- mature cartilage cells, typically found in small groups within cavities called lacunae. - Name, and describe the structure of, the three types of cartilage tissue and provide at least two examples where each is located in the body - Hyaline cartilage - Matrix contains many [closely packed] collagenous fibres. - Collagen fibres are so [fine] they are not distinguishable under the microscope - Provides support with flexibility. - Articular cartilage on the ends of long bones, costal cartilage, respiratory cartilage (larynx) and nasal cartilage of the external nose. - Elastic - Contains fine collagenous fibres (similar to those in hyaline cartilage), but not as closely packed - Also has conspicuous elastic fibres. - Resemble hyaline cartilage but they contain more stretchy elastic fibres and so are better able to stand up to repeated bending. - Found in only two skeletal locations -- the external ear and the epiglottis. - Fibrocartilage - Has a coarse appearance due to [parallel] bundles of [thick] collagenous fibres. - Fibres [not as compacted] as in hyaline cartilage. - Highly compressible and has great tensile strength. - Occur in sites that are subjected to both pressure and stretch such as: - the menisci in the knee - the discs between the vertebrate (intervertebral disc) - the tissue joining the two sides of the pelvis (pubic symphysis). - Explain why damaged cartilage tissue is slow to repair - Damaged cartilage tissue is slow to repair primarily due to its avascular nature, which means it lacks blood vessels necessary for delivering nutrients and oxygen essential for healing. - Define the term 'joint' - Classify joints structurally (fibrous, cartilaginous or synovial) or functionally (immoveable, slightly moveable, freely moveable) - - Describe the general structure and function of fibrous, cartilaginous and synovial joints, giving an example of each - - Name, describe the arrangement of bones and give examples of the different types of synovial joints (ball-and-socket, hinge, pivot, gliding, saddle, condyloid) - Non axial (no plane) = gliding joints - Uniaxial (one plane) = hinge, pivot - Biaxial (two planes) = condyloid, saddle - Multiaxial (three planes) = ball and socket - Identify the major structures of a synovial joint (articular capsule, fibrous capsule, synovial membrane, synovial fluid, articular cartilage) and outline the functions of these structures - articular capsule - fibrous capsule - synovial membrane - synovial fluid - articular cartilage - Describe the role of the menisci, bursae and cruciate ligaments in the knee - - Define each of the types of movements flexion, extension, abduction, adduction, rotation - - State the range of movements permitted for each of the synovial joints - - Describe the changes that occur in bone tissue with osteoporosis and the possible treatments for this condition - Osteoporosis is characterized by a decrease in bone density and mass, resulting in porous, fragile bones that are prone to fractures - Treatments for osteoporosis include medications to slow bone loss or promote bone formation. - List ways that osteoporosis can be prevented - maintaining a diet rich in calcium and vitamin D - Describe the changes to joints associated with osteoarthritis and the possible treatments for this condition including joint replacement surgery - Osteoarthritis is a degenerative joint disease where the cartilage that cushions the ends of bones gradually wears down. - pain relievers, anti-inflammatory medications, physical therapy, and lifestyle modifications such as weight management to reduce stress on joints. - damaged joint with an artificial one, often in the hip or knee, to restore mobility and reduce pain. - List the properties shared by all types of muscle tissue - **Contractibility**: all muscle fibres can contract and shorten. - **Extensibility**: the ability to be stretched. - **Elasticity**: the ability to return to the original length after being stretched. - Give the structural and functional differences between cardiac, smooth and skeletal muscle tissue - - Describe the macroscopic structure of skeletal muscle, using the following terms: tendon; connective tissue; bundles - Skeletal muscle fibres are **huge cells** -- their diameter is up to 10 times that of an average body cell and their length is up to 30cm. - Their size and multiple nuclei are not surprising once you learn that hundreds of embryonic cells fuse to produce each fibre! - Describe the microscopic structure of muscle tissue, using the following terms: muscle fibre; sarcolemma; sarcoplasm; myofibril; myofilament; myosin; actin; A band; I band; Z line; H zone; sarcomere - Skeletal muscle is made up of bundles of muscle fibres each of which contains many myofibrils which contain myofilaments of two types actin and myosin - Use the sliding filament theory to explain how a muscle contracts - A nervous signal causes myosin heads to attach to actin binding-sites forming cross-bridges. - Each myosin head pivots and bends, pulls on an actin filament, causing the actin to slide over the myosin. - As the actin filaments slide over the myosin filaments, the Z lines are drawn closer together, and thus the sarcomere shortens. - Explain why skeletal muscles that move parts of the skeleton are always grouped in pairs - Muscles can only contract. - They can pull bones together, but they cannot push them apart. - If muscles contract, pulling a bone in one direction, another set of muscles must contract to pull the bone in the other direction. Thus, the muscles that move parts of the skeleton are always grouped in pairs. - Define each of the following terms: origin, insertion, agonist, antagonist, extensor, flexor - The end of the muscle fixed to the stationary bone is called the **origin** - The end of the muscle fixed to the movable bone is called the **insertion** - A muscle that causes a desired action is called the **agonist**. - A muscle that yields to the movement of the agonist is called the **antagonist**. - Using the example of the biceps and triceps, describe how skeletal muscles work in antagonist pairs to produce movement about a joint - Give the role of synergistic muscles and fixator muscles - **Synergists** are muscles that help indirectly in steadying a joint during a particular movement. - When a synergist immobilises a joint it is called a **fixator** - Describe the role of muscle tone in maintaining posture - - Describe the structure and give the basic function of the key parts of the respiratory system - Nasal cavity - Bone divided into two chambers (left and right) - Each chamber has 3 shelves called conchae (large surface area) - Lined by mucous membrane that is highly vascular (lots of blood vessels) - Upper membrane has olfactory (smell) receptors - Lower membrane has ciliated cells - - Pharynx - Larynx - Epiglottis - Trachea - Bronchi - Bronchioles - Alveoli - Lungs (pleura & pleural fluid) - Intercostal muscles - Ribs (costa) - Diaphragm - - Outline the difference between breathing and cellular respiration - Define ventilation, inspiration (inhalation) and expiration (exhalation) - Describe, in terms of lung volume and air pressure gradients, how ventilation is achieved - Describe the changes that occur to the structures in the respiratory system during breathing for both inspiration and expiration - Give the oxygen and carbon dioxide concentrations in inspired and expired air and explain these differences - Describe, in terms of concentration gradients, how gas exchange between the alveoli and blood capillaries is achieved - Describe how the lungs, and the alveoli, are well-suited to their roles in gas exchange - Explain how the concentration gradients for oxygen and carbon dioxide are maintained in the alveoli - Describe the changes which occur within the lungs and airways with emphysema, asthma and lung cancer - Link lifestyle factors to the development of respiratory disease such as emphysema and lung cancer - Outline treatment options for people with respiratory diseases such as emphysema and asthma, including drugs (puffers) - State the general function of the circulatory system - Blood is the transport link between the cells of all the body systems: - Transporting oxygen and nutrients to all cells of the body - Transporting carbon dioxide and other waste products away from the cells - Transporting chemical messengers (hormones) to the cells - Maintaining the pH of body fluids - Distributing heat and maintaining body temperature - Maintaining water content and ion concentration of body fluids - Protecting against disease-causing micro-organisms - Clotting when blood vessels are damaged, preventing blood loss - Label the parts of the heart and give their function - - Give the functions of the pericardium - Structure - a membrane that completely enclosing the heart. - Function - holds the heart in place, as well as allowing the heart to move as it beats. It also prevents the heart from overstretching and is made up of cardiac muscle. - Indicate the direction of blood flow through the heart - The heart is referred to as a 'double pump', as the right side of the heart pumps blood to the lungs, whilst the left side of the heart pumps blood to the body. - Describe how the AV valves and semilunar valves control the direction of blood flow through the heart - Valves in the heart ensure that blood can only flow in **one direction**. - **Between atria and ventricles** are the atrioventricular valves (AV valves) - Where arteries leave the heart there are a **second set of valves**, **stopping blood from flowing back into the ventricles** when they relax - semilunar valves. - Describe the direction of blood flow through arteries, veins and capillaries - Arteries - Arterioles - Capillaries - Veins - Venules - Identify the structures in a tissue /capillary bed - A network of capillaries in tissues that surround organs, supplying them with the nutrients they need and carrying away the wastes products. - Explain why blood pressure decreases across a capillary bed - very thin walls that are one cell thick. Very narrow lumen - Describe the structure of arteries, veins and capillaries and relate structure to function - - Define the terms cardiac cycle, diastole and systole - - Outline the events occurring during the main phases of the cardiac cycle (diastole, atrial systole and ventricular systole), including how the AV valves and semilunar valves control the flow of blood during these phases - Diastole (relaxation) - Atrial systole (contraction) - Ventricular systole (contraction) - Identify lifestyle factors that can contribute to coronary heart disease - Distinguish between angina, heart attack and cardiac arrest - Outline what happens during a heart attack, as well as the treatment options available (coronary angioplasty and stents, aspirin) - Describe hypertension and the lifestyle factors that can increase/decrease chances of hypertension, as well as the treatment options available - List the functions of blood - Transport oxygen and nutrients to cells - Transport carbon dioxide and other wastes away from cells - Transport chemical messengers (hormones) - Maintain pH of body fluids - Distribute heat and maintain body temperature - Maintain water content and ion concentration of body fluids - Protection against disease-causing micro-organisms - Identify the four main components of blood - Plasma (55%) - Formed elements (45%) - Red blood cells/Erythrocytes (RBC's) - White blood cells/Leucocytes - Granulocytes - Monocytes & Lymphocytes - Platelets/Thrombocytes - State the pH of blood - 7-8 - List the materials that form the blood plasma and state the general function of this fluid - 91% of plasma is water - Glucose - Amino acids - Lipids - Ions - Oxygen & carbon dioxide gas - Hormones - Wastes - Function: transport the components of blood throughout the body. - Describe how oxygen is transported in the blood and explain how red blood cells are well-suited to their function - Biconcave discs- thinner in the middle then in the edges. - No nucleus- this allows for more room for a substance called haemoglobin. - Biconcave discs- thinner in the middle then in the edges. - Because there is no nucleus, it allows for more surface area to have haemoglobin carry oxygen. - Flexible to fit through capillaries. - Give the word equation for the reaction of oxygen with haemoglobin in red blood cells and explain why this reaction is reversible - Oxyhaemoglobin breaks down to haemoglobin and oxygen when the concentration of oxygen is relatively low in the cells. - Hb+O2HbO2 - Give the proportion of oxygen that is carried as oxyhaemoglobin and dissolved in the plasma - Bound to haemoglobin on red blood cells -- 97% - Dissolved in blood plasma -- 3% - Describe how carbon dioxide is transported in the blood - Plasma- 8% - Haemoglobin on RBC's- 22% - Bicarbonate ions (HCO3-) in plasma- 70% - Give the word and chemical equations for the reaction of carbon dioxide with water in red blood cells to form bicarbonate ions and explain why this reaction is reversible - CO2 is able to chemically bind to the globin part of haemoglobin. - Therefore, it doesn't compete with oxygen transport (binds to the heme part). - When it does this it forms a compound called carbaminohaemoglobin. - Give the proportion of carbon dioxide that is transported as carbaminohaemoglobin, dissolved in blood plasma and as bicarbonate ions - Plasma- 8% - Haemoglobin on RBC's- 22% - Bicarbonate ions (HCO3-) in plasma- 70% - Define the terms 'oxygenated' and 'deoxygenated' blood - The blood that has higher concentration of oxygen is known as oxygenated blood. T - he blood that has higher concentration of carbon dioxide is known as deoxygenated blood - Describe the role played by white blood cells, including phagocytes, in protecting the body from microorganisms - White Blood Cells (WBCs): These are a key part of the immune system, working to identify, target, and neutralize foreign pathogens like bacteria, viruses, and fungi. - Phagocytes: A type of WBC that engulfs and digests microorganisms and debris through a process called phagocytosis. Types of phagocytes include neutrophils and macrophages. They patrol the body and respond to infections by recognizing pathogens, engulfing them, and breaking them down with enzymes. - Identify the blood component/s responsible for blood clotting - **Platelets**: Small cell fragments in the blood that are crucial for blood clotting. - **Clotting Factors**: Proteins in the blood plasma that work together in a cascade to form clots. - Describe the process of blood clotting - Blood vessels constrict to reduce blood flow to the injured area. - Platelets adhere to the site of injury, forming a temporary plug - Clotting factors are activated in a series, leading to the conversion of fibrinogen to fibrin. - Fibrin threads form a stable mesh over the wound, trapping blood cells and platelets, which solidifies into a clot. - Explain how blood clotting protects against infection by microorganisms - Define the terms 'antigen', 'antibody' and 'agglutination' - Any cell or substance that has potential to cause the white blood cells to attack it is called an antigen. - One type of lymphocyte (called B cells) respond by producing a special protein called an antibody. - This will then bring many antigens together into one location -- 'clumping' lots of antigens (the bad guys) together. This process is called agglutination. - Outline the relationship between antigens and antibodies - Explain, in terms of antigens, what makes each blood type different to the others in the ABO system and Rhesus system - Outline how an individual's blood type is determined - Define blood transfusion - State the types of blood transfusion and outline the circumstances of when each would be used - Outline what is meant by the terms 'universal donor' and 'universal recipient' - Explain why blood transfusion requires careful matching of blood types - State the two major functions of the lymphatic system - Identify the major structures of the lymphatic system, i.e., lymph, lymph capillaries, lymph vessels & lymph nodes - Compare the structure of lymph capillaries to blood capillaries, and lymph vessels to veins - Describe how lymph forms in the tissue bed and relate this to how micro-organisms can end up in the lymph - Describe how lymph flows through the lymphatic system to be emptied into the circulatory system via the thoracic duct and right lymphatic duct into the subclavian vein - Describe the structure of a lymph node and identify 'pockets' of these nodes in the human body - Explain how lymph nodes function to protect against infection by microorganisms - TERM 2/3 **DIGESTIVE SYSTEM-** **The digestive system is essential to life because it converts foods into the raw materials that build and fuel our body's cells.** - **List the 6 basic activities of digestion.** - **INGESTION** - **MECHANICAL- Mechanical digestion is when the food is broken down into smaller pieces. Increases the surface area of ingested food, physically preparing it for digestion by enzymes.** - **CHEMICAL- In chemical digestion the large, complex substances in the food are broken down into simpler chemicals. This is a catabolic process.** - **MOVEMENT- Moving of food through the alimentary canal.** - **ABSORPTION-The passage of digested end from the lumen of the alimentary canal, through the cells that line the inner layer of the canal by active or passive transport, into the blood or lymph.** - **ELIMINATION- Defecation removes from the body indigestible substances.** - Define digestion - **Digestion is defined as: the process in which carbohydrate, protein and fat molecules are broken down to products small enough to be absorbed into the blood and into the cells.** - **Distinguish between mechanical and chemical digestion** - **Define the term 'alimentary canal' and describe its basic structure including the role played by circular and longitudinal muscles** - **The alimentary canal is a continuous muscular tube that winds through the body from the mouth to the anus. The alimentary canal is approximately 9m long, but in a living person it is considerably shorter because of its muscle tone.** - **An outer layer of tough connective tissue.** - **A layer of smooth muscle** - **there are usually 2 layers of smooth muscle = a layer of circular muscle and longitudinal muscle.** - **In certain regions throughout the alimentary canal, the layer of circular smooth muscle thickens to form a sphincter. *When this muscle contracts it will close of the tube.*** - **A layer of connective tissue that contains blood vessels, lymph vessels and nerves** - **An inner layer of tissue -- this layer has secretory (releases digestive fluids from glands) and absorptive (where nutrients are moved across the wall of the alimentary canal into the blood stream) roles. These inner layers highly folded to increase the surface area.** - List the key nutrients in food and give the basic function of each- - A **nutrient** is any substance in our food that is used for growth, repair or maintaining the body; that is, any substance required for metabolism. - Carbohydrates (sugars) - Lipids (fats) - Proteins - Minerals eg iron, calcium - Vitamins eg vitamin C - Water - Classify each of the key nutrients as inorganic or organic molecules - Organic molecules are defined as relatively large, carbon-based molecules. - They include: - Carbohydrates (sugars) - Lipids (fats) - Proteins - Inorganic molecules are defined as relatively small, non-carbon-based molecules. - Water (H~2~O) - Minerals eg Fe, Ca, Mg - Vitamins eg A, B, C, D, E, K - Name the major chemical elements that form carbohydrates, proteins and lipids - Carbohydrates - Elements present: carbon, hydrogen, oxygen - Usually twice as many hydrogen as oxygen atoms eg C~6~H~12~O~6~ - Monomer = **monosaccharide**. - Short term energy source for cellular respiration. - Proteins - Elements present: carbon, hydrogen, oxygen, nitrogen - Monomer = amino acid - 20 different types of amino acids - Form cellular structures, for example, haemoglobin, actin, myosin - Control cellular activities (enzymes, hormones) - Lipids (fats) - Elements present: carbon, hydrogen, oxygen - Monomer = fatty acids & glycerol - Long term energy storage - Form some cellular structures eg cell membrane, internal membranes - MOUTH - Ingestion- aided by the teeth, cheeks and tongue - The tongue mixes the food around with the saliva - The cheeks store food whilst chewing - Type of teeth: - Incisors: bite and tear - Canines: tear - Premolar: chew and grind - Premolars: chew and grind - Molars: crush and chew - Mastication - Chemical- salivary amylase - The salivary gland secretes saliva with salivary amylase with the pH 8, water, mucus and lysosome. - Polysaccharide is broken down is disaccharide. - OESOPHAGUS - Movement call peristalsis. - The food is call bolus at this point. - It involves muscular contractions in the wall of the oesophagus and intestines to move food along. The muscular walls of the oesophagus have two layers -- circular and longitudinal muscles. - STOMACH - Contains: - HCL - Protect from bacteria - Mucus - Protect the lining of the stomach - Pepsinogen - When the pepsinogen comes in contact I\'ve HCL, it becomes pepsin - The stomach has 3 layer of smooth muscle: allows the stomach to squeen ythe foo in all directions and enhance chemical digestion - Longitudinal - Circular - Oblique - Stays in there for up to 6 hours - Small intestines - Complete the digestion of macromolecules. - Absorption of the nutrients into the blood and the lymph from across the wall - The liver produces bile, gall bladder store and concentrate bile - After breaking down the fats into smaller pieces, the fats clump back together, hence losing the large SA - Bile breaks down large fat molecule into droplet of fat molecule. This is call emulsification. - Segmentation - Pancreatic amylase breaks down polysaccharides to disaccharide. - Pancreatic lipase breaks down fats from lipids to fatty acid and glycerol - Pancreatic protease breaks down peptide to amino acids. - Intestinal amylase- di to mono - Absorption: the intake of nutrient molecule across the intestinal wall into the blood or lymph - The intestinal walls are highly folded with a structure all villi - The intestine walls have: - Large SA - Thin surface - Large blood supply - Continuous movement - Fat goes into lymph - Everything else is in the blood - Define 'excretion' - **Excretion** is defined as the removal from the body the wastes of metabolism. - These wastes of metabolism include: - Water - Carbon dioxide - Lactic acid - Salts - Bile pigments - Nitrogenous wastes -- ammonia, urea, uric acid, creatinine - Distinguish between elimination and excretion - Elimination is the removal of indigestible waste. - Outline the general excretory functions of the lungs, liver, sweat glands, alimentary canal and kidneys - Lungs - Remove from the body the two major cellular waste products of cellular respiration -- carbon dioxide and water. - Liver - Liver processes excess amino acids to form nitrogenous wastes like urea (deamination). - Breaks down haemoglobin. - Detoxifies alcohol and other drugs like antibiotics. - Deactivates many hormones. - Sweat glands - Sweat contains metabolic wastes: water, salt, urea, lactic acid - Alimentary canal - Removal of bile pigments in faeces. - These pigments are the breakdown products of haemoglobin from red blood cells. - Kidneys - The main organs of excretion - produces urine. - Urine contains: - Water - Salts - Nitrogenous wastes -- urea, ammonia, uric acid, creatinine - Hormones - Medications like antibiotics - State why excess amino acids need to be converted to urea - Amino acids are absorbed into the blood in the small intestine. - Nutrient rich blood first goes to the liver: - Liver cells use some of these amino acids for its own metabolic processes. - Unlike sugars and fats, [amino acids cannot be stored in the body]. So, the liver must break down any [excess] amino acids to remove them from the blood. - Explain how the liver excretes excess amino acids in the form of urea via deamination - An amino acid reacts with oxygen to form a **carbohydrate** molecule when the **amino group** (-NH~2~) is removed from the amino acid - This amino group (-NH~2~) is then converted into **ammonia** (NH~3~). - Ammonia is a toxic substance, so the liver then converts this molecule into a non-toxic molecule called **urea**. - This process is controlled by enzymes. - Give the word equation for deamination - Amino acid + oxygencarbohydrates + ammonia - CO2+ammoniaurea + water - State the three main functions of the kidneys - Regulating body fluids by controlling the total volume of water in the body and the total concentration of solutes in that water. - Ensuring long-term acid-base balance of the [blood] by maintaining the pH of the blood (pH 7.4). - Excreting metabolic wastes, including nitrogenous wastes, and foreign substances such as drugs and toxins from the [blood]. - Identify the macroscopic structures of the kidneys, including the renal cortex, renal medulla, renal pyramids, renal pelvis, ureters, renal arteries and renal veins - Identify the microscopic structures of the nephron, including the blood supply (afferent arteriole, glomerulus, efferent arteriole, peritubular capillaries) and tubule structures (glomerular capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct) - - Recall the structures of the nephron that form the renal corpuscle - The functional unit of the kidney is called a nephron. - Identify the location of microscopic structures relative to macroscopic structures in the kidneys - - Describe how high blood pressure is maintained in the glomerulus and the importance of this high blood pressure - The efferent arteriole has an narrower diameter than the afferent arteriole hence increase the resistance to blood flow and high BP. - Describe the process of glomerular filtration, and give examples of materials that are filtered out of the blood into the filtrate - A process by which high blood pressure forces fluids and solute through a filtering membrane。 - List the materials in blood that are not filtered into the glomerular capsule and say why this occurs - Blood cells and large protein molecules are not filtered by the glomerulus - Describe what happens in the process of selective reabsorption - Selective reabsorption is a passive or active process in which substances in the filtrate are moved into the blood. - List the materials that are selectively reabsorbed and say why this occurs - Proximal convoluted tubule - Water - osmosis - Glucose - 100% - Amino acid - 100% - Sodium ions - Urea - Distal convoluted tubule - Controlled by hormones - Fine tuned - Loop of henle - Water can leave the descending limb of the loop of Henle but not the ascending limb as the channel proteins for water are absent in the cells forming the ascending limb. - The opposite happens for sodium, potassium and chloride ions which are both actively and passively transported in the ascending limb. - Describe what happens in the process of tubular secretion and list materials that can be secreted into the filtrate - Controlling blood pH: when blood pH drops slightly, the renal tubules will actively secrete more H^+^ into the filtrate. - Urea, uric acid, ammonium ions -- passive transport. - Metabolites like drugs, hormones - active transport. - Ridding the body of excess potassium ions -- active transport (controlled by aldosterone). - Describe the ways in which the structure of the kidneys, in particular the nephron, maximises the formation of urine - There are millions of nephrons in the kidney - Single cell thickness - State the role of the ureters, bladder and urethra in the removal of urine from the body - - List the major components of urine - - Give similarities and differences between the composition of blood plasma and urine, including pH - Describe the changes which occur within the kidneys with kidney disease and kidney failure - Link lifestyle factors to the development of kidney disease and subsequent kidney failure - Describe the treatment options for people with kidney failure, including dialysis (peritoneal and haemodialysis) and kidney transplant - Explain how dialysis replaces the function of the kidney - TERM 3 - Recognise nucleic acids as a type of organic compound, including the elements present and the basic structure of a nucleotide (monomer) - General function: to store biological information or energy - Elements present: carbon, hydrogen, oxygen, nitrogen and phosphorus - Monomer: the base unit of a nucleic acid is called a nucleotide - A nucleotide is composed of three parts: - A phosphate group - A sugar - A nitrogenous base - Recall the three types of nucleic acids (DNA, RNA, ATP/ADP) - Outline the role of DNA in the cell - Store the genetic instructions for making a protein. - Describe the structure of DNA, using the terms double helix, nucleotide, deoxyribose, phosphate group, nitrogenous base, cytosine, guanine, adenine, thymine, complementary base pairing, hydrogen bond, 5' and 3' - The two strands of DNA run in opposite directions to each other and are thus **anti-parallel**. - The nucleotides form the basis of a **ladder-like molecule**, where the sugar/phosphate forms the uprights, and the joined nitrogenous base pairs form the rungs of the ladder that twists up in a spiral shape to form a **double helix structure**. - Describe how DNA is found within the nucleus of cells, in terms of histones, chromatin and chromosomes. - Molecules of DNA are in the form of **long strands in the nucleus.** - The DNA strands are coiled around eight special protein molecules called **histones** to form a nucleosome. - In a non-dividing cell, the DNA molecule and the histones together form a structure called **chromatin**. - In a dividing cell the chromatin become densely coiled strands called **chromosomes**. - There are 46 chromosomes or 23 pairs of chromosomes - Describe structure, location and function of mitochondrial DNA - Small, circular rings of DNA - No histones - 5-10 mtDNA in each mitochondrion - 37 genes - 24 genes = codes for making tRNA - 13 genes = enzymes necessary for the reactions of cellular respiration - Compare nuclear DNA and mitochondrial DNA - DNA has histones, mtDNA has no histones - Only 37 genes compared to 20000-25000 - Define the terms 'gene', 'genetic code' and 'protein synthesis' - A gene is a section of a chromosome that codes for making a protein. - The order of the bases along the DNA strand is called the genetic code. - List examples of proteins produced in human cells - Enzymes - Recall the basic structure of proteins - CHONP - Describe the structure of RNA - Ribonucleic acid. - Single-stranded polymer. - Nucleotides -- guanine, cytosine, adenine and uracil - Compare DNA and RNA in terms of number of strands, type of sugar and nitrogenous bases - The name of the sugar in RNA is ribose. - In DNA the sugar is called deoxyribose. - DNA lacks an oxygen in 2' - Give the role of mRNA, rRNA and tRNA in the cell - mRNA: - Made in the nucleus (transcription) - Takes the genetic code for making a protein to the ribosomes. - **The role of messenger RNA is to carry the instructions for making the protein from the nucleus to the ribosome.** - rRNA: - The rRNA ensures the correct alignment of mRNA, tRNA and ribosome. - It also has an enzymatic role in the formation of peptide bonds between amino acids. - tRNA - Folded 'clover-leaf' structure. - Able to transfer a [specific] amino acid from the cytoplasm to the ribosome. - **The role of transfer RNA is to retrieve the correct amino acid from the cytoplasm to the ribosome.** - Distinguish between a triplet, a codon and an anticodon - DNA - A sequence of [three bases in DNA] codes for one amino acid. - This sequence of three bases in DNA is called a triplet. - RNA - A sequence of [three bases on mRNA] codes for one amino acid - A sequence of three bases in mRNA is called a codon - tRNA - A sequence of [three bases on tRNA] codes for one amino acid. - A sequence of three bases in tRNA is called an anti-codon. - **[Describe the process of transcription in the nucleus of the cell, including the role of RNA polymerase ]** - RNA polymerase attaches to the start of the gene. - As the RNA polymerase moves along the DNA, it unwinds and unzips the DNA. - As this is happening the RNA polymerase builds mRNA by joining together free RNA nucleotides, i.e., A, U, C and G, that are complimentary to the DNA template sequence. - mRNA synthesis stops when the RNA polymerase reaches the end sequence on the gene. - mRNA molecule is released and moves out of nucleus through nuclear pores. - Describe the process of translation at the ribosomes - Ribosome forms a complex around the mRNA. - Ribosome reads the three bases forming each codon in the mRNA one at a time. - AUG codon is the start codon and is the signal for the ribosome to begin translation. - Specific tRNA molecules bring each of the required amino acids to the ribosome from the cytoplasm, where the anticodon on the tRNA binds to the complimentary codon on the mRNA. - Two amino acids are momentarily held in position to allow for the formation of peptide bonds between the amino acids, which eventually will eventually allow for the formation of a polypeptide chain. This process requires ATP. - The process of translation continues until the stop codon is reached. - Outline the role of the nucleus, ribosomes, endoplasmic reticulum and Golgi body in protein synthesis - ROUGH ER - Ribosomes can attach to and detach from the endoplasmic reticulum. - Once the ribosome attaches to the rough ER, the growing polypeptide chain snakes through the ER membrane pores into the ER. - The polypeptide chain undergoes folding in the rough ER. - The polypeptide chain is enclosed within a transport vesicle, which will then make its way to the Golgi body. - GOLGI BODY - Vesicles from the RER migrate to the Golgi body. - Proteins are modified inside the Golgi and packaged into vesicles: - Proteins for secretion = exocytosis. - Proteins destined for membranes = fuse with the cell membrane. - Digestive enzymes = eventually become lysosomes (or fuse with lysosomes) - Define 'gene expression', 'epigenetics', 'genome' and 'epigenome' - A **genome** is the complete set of genetic information of an organism. - The process of copying information from DNA to mRNA and then translating the message into a series of amino acids to form a protein, is called **gene expression**. - **Epigenetics** can be defined as altering the expression of a gene [without changing the gene structure.] - **Epigenome**: The **epigenome** is a set of instructions that determine when, where and which genes are 'switched on' or expressed, some of which can be passed onto offspring. - Outline how the chemical processes of acetylation and methylation can alter how genes are expressed - **Histone Modification: Acetylation** **Involves the: addition of an acetyl group, to the histone proteins** - This causes the histones to tighten / loosen how the DNA molecule is coiled. - This will block / expose the gene for transcription. - This inhibits / enhances transcription ie. gene expression. - **Histone Modification: Methylation** - Addition of a **methyl group** (CH~3~) to cytosine bases of the **DNA** molecule**.** - Usually occurs at sites where cytosine is adjacent to guanine, which is called as **CpG site.** - DNA methylation **tightens** the how the DNA coils around the histone - This will **block** the gene (DNA) which will prevent the RNA polymerase accessing the gene, and thus not allow transcription to occur. - The attachment of the methyl group will therefore **inhibit** gene expression - Define and outline the stages of the cell cycle - The cell cycle is: The events that take place from one cell division to the next. - Define and give the purpose of DNA replication - new cells are constantly needed for growth and to replace cells that have died or been damaged. - Outline the process of DNA replication including the role of helicase, DNA polymerase and DNA ligase - S phase - An enzyme called helicase unzips the DNA molecule at the weak hydrogen bond between the two complimentary bases to separate the two strands. - The unzipped DNA molecule now has the nitrogenous bases exposed. These exposed bases serve as a template to copy the new DNA strands. - DNA polymerase attaches complimentary free nucleotides to form the new strands of DNA. - DNA ligase joins together the phosphate-sugar backbone of the newly formed DNA strands. - Distinguish between haploid and diploid cells. - Diploid cells contain two of each type of chromosome. - The diploid number is defined as [two complete sets of chromosomes]. - Define mitosis, give its purpose and location that it occurs - Mitosis the process of making new cells from existing cells. - The purpose of a mitotic cell division is to make new cells for [growth] and [repair.] - Mitosis occurs when body cells, called somatic cells, divide in body tissues. - At the end of a mitotic cell division, the two daughter cells are genetically identical to the original parent cell. - List the stages of mitosis, in order, and describe the events occurring in each stage - Prophase - Centrioles migrate to the poles of the cell and produce spindle fibres. - Nuclear membrane breaks down. - Chromosomes condense and become visible in the cytoplasm of the cell. - Chromosomes begin migrating to the equator of the cell. - Metaphase - Chromosomes line up of the equator of the cell head-to-toe. - Spindle fibers attach to the centromere of each chromosome - Anaphase - Spindle fibers contract towards the centrioles. - The chromosomes are separated at the centromere and the [chromatids] are pulled towards opposite poles of the cell. - Telophase - Two nuclear membranes form around each group of chromosomes. - Spindle fibers break down. - Define cytokinesis - The cell membrane and cytoplasm splits into two cells. - These daughter cells are genetically identical to the original parent cell. - Give the similarities between the parent cell and the daughter cells formed via mitosis - They are both diploid cells.\] - Distinguish between stem cells and specialised cells - A **specialized cell** has a particular function. - Its structures are modified to allow the cell to carry out this function. - A **stem cell** is defined as an unspecialised cell. - Stem cells undergo cell division. - They have the ability to continue to cycle through the cell cycle. - Define and outline the process of differentiation - **Differentiation**: the [process] of making specialised cells. - Differentiation is triggered by chemicals signals in the **microenvironment** around the cell. - These chemical signals **activate certain genes** and cause gene expression of particular genes in each cell type. - Explain what a stem cell is - The number of different types of cells that they can form - (potency) - Where they originate (their source) - (embryonic, somatic) - Give two key properties of stem cells , i.e., proliferation and differentiation - Outline the basis on which stem cells can be classified - Potency - Origination - Distinguish between totipotent, pluripotent and multipotent stem cells - Totipotent - Can become ANY cell of the BODY and/or the embryonic MEMBRANES - Pluripotent - Can become ANY cell of the body but NOT the embryonic membranes - Multipotent - Can become SOME cells of the body ONLY - Define cancer as an uncontrolled division of cells - A disease in which abnormal cells divide uncontrollably and destroy body tissue. - These cells may form a mass called a tumour. - A tumour can be cancerous or benign. - Describe a tumour and differentiate between a malignant and a benign tumour - A cancerous tumour is malignant, meaning it can grow and spread to other parts of the body. - As a cancerous tumour grows, the blood or lymph may carry cancer cells to other parts of the body. This is known as metastasis. - A benign tumour means the tumour can grow but will not spread to other parts of the body. - Outline some known environmental causes of cancers, i.e. carcinogens, including UV radiation, X-rays, ionising radiation, viruses, chemical carcinogens - Cancer is caused by changes (mutations) to the DNA within cells. - Outline ways to reduce your risk of developing cancer, i.e. through lifestyle changes - Eating healthily - Having regular checkup - Discuss the importance of early detection for the success of cancer treatment - Describe the technologies available to detect cervical cancer, breast cancer, bowel cancer and prostate cancer - Breast cancer - Bowel cancer - Cervix cancer - Prostate cancer - Explain what homologous chromosomes are. - Homologous chromosomes are pairs of chromosomes that are identical in size and shape, and they have the same genes located in the same position. - distinguish between haploid and diploid cells. - Gametes are haploid cells which can combine at [fertilisation] to produce a new individual. - A haploid cell is defined as having one complete set of chromosomes. - Define meiosis, give its purpose and location that it occurs. - Meiosis is the process of cell division to make gametes (sex cells) for sexual reproduction. - Meiosis occurs in specialized tissue called the gonads: - In males, the gonads are called the testes. - In females, the gonads are called the ovaries. - List the stages of meiosis, in order, and describe the events occurring in each stage of meiosis. - Prophase 1 - Same as mitosis - Metaphase 1 - Chromosomes line up on the equator of the cell in homologous pairs. - Spindle fibres attach to the centromeres of each chromosome. - Anaphase 1 - Homologous chromosomes separate and move to opposite poles of the cell. - Telophase 1 - Two nuclear membranes form around each group of chromosomes. - Spindle fibres break down. - Cytokinesis - Cytokinesis occurs, forming two haploid daughter cells. - Prophase 2 - Same as prophase 1 - Metaphase 2 - Same as metaphase mitosis - Anaphase 2 - Same as mitosis - Telophase 2 - Same as mitosis - Cytokinesis - Give the similarities between the parent cell and the daughter cells formed via meiosis. - Outline the similarities and differences between mitosis and meiosis. - In both mitosis and meiosis, the parent cell has 46 chromosomes and is a diploid cell. - In both mitosis and meiosis DNA replication occurs during the S phase of interphase. This doubles the amount of DNA, but the chromosome number does not change. - During metaphase in mitosis and metaphase II in meiosis the chromosomes line up on the equator of the cell head-to-toe. - During anaphase in mitosis and anaphase II in meiosis the chromosomes are separated by the spindle fibres at the centromere and the chromatids are pulled towards the poles of the cell. - Explain why mitosis cannot be the process that results in the formation of gametes. - Mitosis cannot be the process that results in the formation of gametes because it produces genetically identical daughter cells with a diploid (2n) chromosome number, meaning they have the full set of chromosomes (46 in humans). Gametes, however, require only half the number of chromosomes---a haploid (n) set---so that when fertilization occurs, the resulting zygote has the correct diploid number. - Define the term 'variation' - **Variations** are the differences in traits, or phenotype, that occur between individuals of the same species. - Explain in terms of their function, why it is important for the daughter cells formed via meiosis to be genetically different from the original parent cell. - Genetic diversity in daughter cells formed via meiosis is crucial for a species\' survival and adaptability. This diversity enhances the chances that some offspring will inherit advantageous traits, such as disease resistance or better adaptability to environmental changes, which improves their likelihood of survival and successful reproduction. - Describe crossing over, using the terms homologous pair, chiasma, recombination of alleles - During prophase I in meiosis, the chromatids of the homologous chromosomes tangle together. This is called crossing over. - The point that the chromatids of homologous chromosomes cross over is called the chiasma - These overlapping chromatids may exchange segments of their DNA with each other. This process of exchange is called recombination. - The resultant chromatids now consist mainly of the DNA from the original chromatid but also partly that of the other chromatid. This results in new combinations of alleles. - Explain how crossing over contributes to the differences between gametes produced by meiosis - Describe the process of random assortment of chromosomes during meiosis - During anaphase I in meiosis I, the homologous pairs of chromosomes (paternal and maternal) separate. - One member of each pair moves to one pole of the cell, and the other moves in the opposite direction. - All homologous pairs of chromosomes separate independently - Explain how random assortment contributes to the differences between gametes produced by meiosis - - Explain how non-disjunction, either in meiosis I or II, can result in aneuploid daughter cells - Random mistakes can occur during the assortment of chromosomes in meiosis I: - During metaphase I homologous chromosomes pair on the equator of the cell and are then separated during anaphase I. - Sometimes one or more of the [homologous pairs of chromosome] pairs may fail to separate. - This results in aneuploidy, where some of the daughter cells receiving an extra chromosome and some receiving one less chromosome. - This results in aneuploidy, where some of the daughter cells receiving an extra chromosome and some receiving one less chromosome. - **A condition of having an abnormal number of chromosomes in a haploid set.** - Identify a monosomy, a partial monosomy or a trisomy from a karyotype - - Describe the consequences of trisomy 21 - Trisomy 21, or Down syndrome, occurs when there is an extra copy of chromosome 21 in a person's cells. This results in developmental and intellectual delays, characteristic facial features, and various health issues, including heart defects, respiratory problems, and increased susceptibility to certain diseases. Trisomy 21 affects physical growth and cognitive development, with the severity of symptoms varying widely among individuals. - Define gametogenesis, oogenesis and spermatogenesis  - Gametogenesis: The production of gametes, which includes the process of meiosis and the maturation of the daughter cells produced. - Spermatogenesis -- formation of spermatozoa in the testes. - Oogenesis -- formation of ova in the ovaries. - Outline the process of spermatogenesis in the seminiferous tubules of the testes, including the timing of events, using terms such as spermatogonium, primary spermatocyte, secondary spermatocyte, spermatozoa - Describe the structure of a mature spermatozoan - Head: contains haploid nucleus with genetic material and a large vesicle called the acrosome (contains enzymes). - Midpiece: tightly packed mitochondria fill this section (provide the energy to power the flagellum) - Tail: one long, elongated flagellum which contain protein microtubules to propel the sperm - Outline process of oogenesis in the ovaries, including the timing of events, using terms such as oogonium, primary oocyte, secondary oocyte, polar bodies, ovum - Oogonia cells will then differentiate into primary oocytes -- the diploid parent cells that will undergo meiosis. - The first meiotic division will begin in the early foetal period and remains arrested in prophase I. - They will remain in prophase I in the ovaries until puberty. - Explain why polar bodies are formed  - Polar bodies are formed during oogenesis as a way to discard excess genetic material while ensuring that the resulting ovum (egg cell) retains as much cytoplasm and nutrients as possible. - Recognise that a fully mature ovum does not form unless fertilisation occurs. - Define the terms 'endocrine gland' and 'hormone' - A **hormone** is a **chemical messenger produced by specialized cells** that form **endocrine glands**. - Their role is to allow cells to communicate with each and coordinate body processes. - Briefly outline how hormones are transported around the body and the role of target cells - The secreting cell makes the hormone and is located in an endocrine gland. - The secreting cell releases the hormone into the tissue fluid, and it then diffuses into the blood - The hormone travels around the whole body in the blood. - Hormones are chemical messengers that can cause a change in the activity of target cells. A target cell has the specific protein receptors located in their cell membrane. - Identify the endocrine gland, target organs and effects of the following hormones in the male reproductive system: follicle stimulating hormone, luteinizing hormone and testosterone in the male reproductive system - - Identify the endocrine gland, target organs and effects of the following hormones in the female reproductive system: follicle stimulating hormone, luteinizing hormone, oestrogen, progesterone, human chorionic gonadotropin, oxytocin and prolactin in the female reproductive system - - Describe the events of the follicular phase and luteal phase in the ovarian cycle - Ovarian cycle -- occurs in the ovaries. - Follicular phase - If the cycle is 28 days on average, the follicular phase occurs over the first 14 days of the ovarian cycle. - This phase involves the maturation of the ovarian follicle; from the primary follicle, to the secondary follicle, to the mature follicle. - The follicular phase ends with ovulation on day 14 of the ovarian cycle. - The corpus luteum is an endocrine gland and produces and releases two hormones. - If pregnancy does not occur, the corpus luteum starts degenerating after about 10 days and its hormonal output ends. - All that ultimately remains is a scar called the corpus albicans. - Ovulation - Ovulation occurs when the ballooning ovary wall ruptures and expels the secondary oocyte into the peritoneal cavity. - This secondary oocyte is then swept up into the Fallopian tube by the fimbriae. - Menstrual cycle -- occurs in the uterus and involves the shedding and build up of the inner lining of the uterus, the endometrium. - Menstruation - Shedding of the uterine lining. - The thick, functional layer of the endometrium detaches from the uterine wall, a process accompanied by bleeding. - The detached tissue and blood pass out through the vagina as the menstrual flow. - On average 5 days. - Proliferative Phase - The endometrium rebuilds itself. - New layer grows and thickens, its glands enlarge, and its spiral arteries increase in number. - Becomes velvety, thick and vascularised. - From the end of menstruation until approximately day 14. - Secretory Phase - The endometrium prepares for an embryo to implant. - Endometrial glands enlarge, coil and begin secreting nutrients into the uterine cavity. - These nutrients will sustain the embryo until it has implanted in the blood-rich endometrial lining. - Days 14-28. - Describe the role of the pituitary hormones FSH and LH on follicular phase of the ovarian cycle - Describe the role of the ovarian hormones, oestrogen and progesterone (both increased and decreased levels) on the endometrium during the menstrual cycle - State how levels of oestrogen and progesterone in the blood influence the release of the pituitary hormones and vice versa - Explain how the release of the four reproductive hormones (FSH, LH, oestrogen and progesterone) are timed to control the events of the menstrual and ovarian cycles - Define 'embryo' and 'embryonic period'; 'foetus' and 'foetal period' - An embryo is the early stage of development of an organism. - The embryonic period in humans is from fertilization to the end of the eighth week of pregnancy. - A foetus is the developing individual after the second month (after 8 weeks) of pregnancy. - The foetal period is from the second month of pregnancy until birth. - Define 'zygote' - A zygote is the diploid cell created when a sperm fertilizes an egg, containing a complete set of chromosomes from both parents. - Describe how the fertilised egg is moved from the fallopian tube to the uterus- day 0 (end of week 2) - Takes place in the top 1/3 of the Fallopian tube Results in the formation of the zygote. - Takes place in the Fallopian tube while the cilia and smooth muscle contractions move the early embryo towards the uterine cavity. - Describe how the process of cleavage results in the formation of the morula -- day 1-4 - Cleavage is cell division that results in two daughter cells, but there is no new cytoplasm, i.e., the cells get smaller. - Eventually form a tightly packed ball of cells called the morula. - Describe the blastocyst, including the importance of the inner cell mass- day 5 - By the end of day 5, the cells of the morula will rearrange themselves into a structure called a blastocyst. - A blastocyst is a hollow ball of cells. - Outline the process of implantation of the blastocyst - By the end of day 5 the blastocyst has formed and has reached the uterine cavity. - In the uterine cavity the blastocyst floats free for a day or so and is nourished by secretions from the endometrium. - One week after fertilisation, on day 7-8, the blastocyst will embed in the endometrium in the uterus, in a process called implantation. - Implantation involves the blastocyst sinking into the soft endometrial tissue, and then a little later, becoming firmly attached - The blastocyst is still enclosed in the zona pellucida, and for it to be able to implant into the uterine wall the zona pellucida is shed. - Contact is made between the blastocyst and the endometrium. The blastocyst orients itself so that the inner cell mass is aligned closest to the endometrium. - The cells of the outer layer of the blastocyst adhere to the endometrium. - The cells of the outer layer of the blastocyst continue to divide (proliferate) and secrete enzymes allowing the whole structure to penetrate the endometrium. - The blastocyst obtains nourishment for growth and development by absorbing nutrients from glandular secretions and blood vessels of the endometrium. - Successful implantation takes about 5 days. - The cells, as they divide, rearrange themselves to form two layers: the outer layer (E1) which eventually form the chorion (embryonic membrane) and becomes the placenta. - The inner layer called the inner cell mass (E3) Eventually will become the developing embryo. E2 is a fluid filled cavity. - Define primary germ layer. - 3 layers of cells that form the 3 layered embryo and will go on to form all the organs and tissues. - Name the three primary germ layers in the embryo. - Ectoderm ('outer skin') - Mesoderm ('middle skin') - Endoderm ('inner skin') - Give three structures formed by each primary germ layer. - Ectoderm ('outer skin') - nervous system - skin epidermis - brain - spinal cord - hair - nail - Mesoderm ('middle skin') - other tissues- connective tissue, muscular tissue. - Smooth - Cardiac - Skeletal - blood - Endoderm ('inner skin') - Epithetical lining of the different systems - Glands - Liver - Pancreas - Thyroid - kidneys - Name the four embryonic membranes. - Amnion - Yolk sac - Allantois - Chorion - Describe the structure and function of the amnion and amniotic fluid. - Following the implantation, the inner cell mass of the blastocyst proliferates and a cavity forms that separate these cells from the outer layer of the cell. - Protects the embryo from physical injury - Help maintain the consistency temperature - Allow embryo to move more free - Provides a buoyant environment - Identify the chorion and give its function. - Formed from the outer cells of the blastocyst together with a layer of mesodermal cells. - Eventually the chorion becomes the main part of the foetal portion of the placenta. - Describe the influence of hCG on the ovary - Human chorionic gonadotropin (hCG) - Endocrine gland: chorion (embryonic membrane) - Target cell/organ: corpus luteum in the ovary - Effect on target organ: maintains the corpus luteum during early pregnancy. - Progesterone: - Endocrine gland: corpus luteum (early) and placenta - Target cell/organ: endometrium in the uterus - Effect on target organ maintains the endometrium, thickens cervical mucus and stimulates breast growth. - Oestrogen: - Endocrine gland: corpus luteum (early) and placenta - Target cell/organ: endometrium in the uterus - Effect on target organ: builds the uterus and uterine lining by increasing blood flow to the uterus, helps foetal organs grow, stimulates breast growth - Outline how the chorion develops into the foetal portion of the placenta, including the role of the chorionic villi - The placenta is formed gradually during the first three months of pregnancy. - After the 4^th^ month, it grows parallel to the development of the uterus. - Once completed, it is a spongy disc about 20cm in diameter and 3cm thick. - it is a temporary organ. - The placenta is made up of: - The foetal portion, which is made up of foetal tissue. - The maternal portion, which is made up of maternal tissue. - The extraembryonic mesodermal cells give rise to blood cells and blood vessels, forming the network of foetal blood vessels that are in the chorionic villi and connect to the foetal heart. - Describe the structure of the placenta in terms of foetal and maternal circulation - The extraembryonic mesodermal cells give rise to blood cells and blood vessels, forming the network of foetal blood vessels that are in the chorionic villi and connect to the foetal heart. - Endometrial arteries, called spiral arteries, reside inside the maternal portion of the placenta. - They release maternal blood into the intervillous space to bathe the chorionic villi. - Endometrial veins then drain the blood. - *This allows for maternal blood to provide oxygen and other nutrients to transport across into the foetal blood and remove wastes from the foetal blood.* - Describe the major functions of the placenta. - The general function of the placenta is to supply nutrients to and remove wastes from the [foetal blood]. - Oxygen [diffuses] from mother's blood to foetal blood. This is considered a respiratory function. - Carbon dioxide [diffuses] from foetal blood to the mother's blood. This is considered a respiratory function. - Nutrients, such as glucose, are transported from the maternal blood into the foetal blood. This is considered a nutritional function. - Wastes, including nitrogenous wastes such as urea, uric acid, ammonia and creatinine, are transported from the foetal blood into the maternal blood. This is considered an excretory function. - Progesterone: - support of the endometrium - inhibit secretion of FSH and LH - Oestrogen - increases late in pregnancy - ready the woman's body for labour, stimulates glandular tissue development in the breast - Antibodies are transported from the mother's blood into the foetal blood supply to provide some immunity to the developing baby. - Describe the structure and function of the umbilical cord. - The role of the umbilical cord is to transport deoxygenated [foetal blood] to the placenta and return oxygenated [foetal blood] to the foetus. The umbilical cord has two arteries and a single vein. - The umbilical cord has two arteries and a single vein. - The umbilical arteries carries deoxygenated blood from the foetus to the placenta. - The umbilical vein carries oxygenated blood from the placenta to the foetus. - Define parturition and labour - Gestation is the time that the embryo or foetus is carried in the uterus as a pregnancy. - This growth and development takes about 280 days and is measured from the beginning of the last menstrual period. - Parturition, or birth, is the process by which the foetus is expelled from the mother's body at the end of gestation. - Labour is the sequence of events that precedes parturition. - Describe the role of the hormone oxytocin during labour - - Outline the key events that occur during the first stage of labour, including the formation of the birth canal - Waves of smooth muscle contractions make the uterus shorten, pulling on the cervix. - The cervix dilates to 10cm. - The birth canal is now formed, consisting of the uterus, cervix and vagina. - Outline the key events that occur during the second stage of labour, including contractions, crowning and expulsion of the foetus - Usually begins with the rupturing of the amniotic sac to release amniotic fluid. - As the foetus moves through the fully dilated cervix, it stretches the vagina stimulating the woman to use both abdominal muscles and uterine muscles to contract to push. - The baby's head emerges, the baby turns sideways allowing the shoulders and the rest of the body to move through the birth canal. - Outline the key events that occur during the third stage of labour - Involves: the expulsion of the placenta, other membranes and the remains of the umbilical cord. - Duration: 5 minutes - Describe how and why the foetal liver is bypassed via the ductus venosus - The ductus venosus is a [vascular shunt] that connects the umbilical vein to the inferior vena cava, therefore allowing blood to bypass the inactive liver. - Describe how and why the foetal lungs are bypassed via the ductus arteriosus - The ductus arteriosus is a small [vascular shunt] that connects the pulmonary artery to the aorta, therefore allowing blood to bypass the inactive lungs. - Describe how and why the foetal blood can flow directly from the right atrium to the left atrium via the foramen ovale - The foramen ovale creates a [vascular shunt] between the right atrium and the left atrium, allowing oxygenated blood to pass through to the left ventricle and into the aorta, bypassing the lungs. - List the life functions that a newborn must take over (from the mother) at birth - Beath - Remove waste - Describe the changes that occur in the circulation of the newborn with respect to the ductus venosus and ductus arteriosus - As the lungs expand, they no longer resists blood flow from the heart. - This means that blood flow through the ductus arteriosus decreases. - By a few weeks after birth this tissue become fibrous (and non-functional). - Explain why the clamping of the umbilical cord may trigger the above change - Describe the changes that occur in the circulation of the newborn with respect to the foramen ovale - As larger amounts of blood return to the heart from the lungs, blood pressure in the left atrium increases. - This increased blood pressure in the left atrium forces the flap of tissue of the foramen ovale against the wall of the atrium, closing off this opening. - Explain why the commencement of breathing may trigger the above change - Explain what a 'hole-in-the-heart' is - In up to 20% of healthy adults, the foramen ovale will not completely close. This I scalled a 'patent foramen ovale' (PFO). - Recall how the processes of meiosis results in variation between gametes - - Outline the importance of Mendel's experiments - Explain what is meant by the principle of segregation - Distinguish between dominant and recessive traits - Distinguish between a gene and an allele - A gene is a section of chromosome that code for a protein. - Allele is an alternative form of a gene that occurs at a given point in a chromosome. - Distinguish between phenotype and genotype - Genotype is the genetic constitution of an individual - Phenotype is the appearance of an individual as determined by their genetic constitution. - Explain what is meant by homozygous and heterozygous genotypes - An organism is said to be homozygous for a gene if it has two identical alleles. - An organism is considered heterozygous for a gene if it has two different alleles. - Determine the **mode of inheritance** for a trait (autosomal or X-linked, dominant or recessive) from the pattern of inheritance in a pedigree - Is the trait dominant or recessive? - Look for two parents who both have the trait, and their child does not, or vice versa. - Is the trait autosomal or X-linked? - Look for any man with the trait and see if you can find any examples where his daughters do not have the trait. If you find this, then the trait must be autosomal. - Distinguish between autosomes and sex chromosomes - An autosomal trait is one where the alleles for that trait or condition is located on a non-sex chromosome. - A sex-linked (or X-linked) trait is one where the alleles for that trait or condition are located on the X-chromosome. - Define single-gene disorder - Caused by variations (or mutations) in the DNA sequence of a specific gene. - The DNA changes affect the product that the gene codes for -- usually a protein -- causing the protein to be altered structurally, or not produced at all, or too much. - Explain what is meant by an autosomal trait and give two examples (Huntington's disease; PKU) - Autosomal single-gene disorders are those conditions that occur due to changes in the DNA sequence on a single gene found on an autosome. - Give the mode of inheritance of Huntington's disease and list the symptoms - Autosomal dominate. - A neurodegenerative disease that causes involuntary muscle movements, cognitive decline and behavioural changes. - Explain why the allele for Huntington's disease has persisted in the population - As HD is controlled by a dominant allele, the condition is likely to be passed from one generation to the next. - As the condition does not become apparent until later in life, the children of a person with the condition may not be aware that they themselves have inherited the disorder until after they have had children of their own. - Outline what is meant by the term 'carrier' - A carrier is a person who is heterozygous for a condition, but do not show the recessive phenotype. - Explain why severe recessive disorders are rarely passed on to the next generation except in a consanguineous mating - The incidence of severe recessive disorders is low, because it is unlikely that a carrier from one family will mate with another carrier of the same recessive condition. - A particular condition could suddenly appear where there has been no family history of the disease. - In a consanguineous mating, where a couple are close relatives, e.g. cousins, the chance of them both being a carrier for a recessive allele is greater. - Give the mode of inheritance, characteristics and symptoms of phenylketonuria (PKU) - Autosoma