Biology Year 10 Revision - PDF

BIOLOGY YEAR TEN REVISION Topic 1: the movement into and out of cells DIFFUSION Diffusion is the net overall movement of particles from an area of high concentration to an area of low concentration Diffusion can occur in solids, liquids, and gases Time tells us how long it takes for something t...

BIOLOGY YEAR TEN REVISION Topic 1: the movement into and out of cells DIFFUSION Diffusion is the net overall movement of particles from an area of high concentration to an area of low concentration Diffusion can occur in solids, liquids, and gases Time tells us how long it takes for something to happen Rate tells us how quickly something is happening The longer the time the slower the rate, The shorter the time the quicker the rate. The rate of diffusion is how quickly diffusion occurs. It is the number of particles that move at a particular time. Diffusion can be affected by: Temperature Distance Surface area Concentration gradient As temperature increases the rate of diffusion increases →this is because as particles are heated they have more kinetic energy which allows them to move faster As distance increases the rate of diffusion decreases →it takes longer for the particles to move a greater distance than a shorter distance As surface area increases the rate of diffusion increases →if the surface area is larger more particles are able to move at the same time As the concentration gradient increases the rate of diffusion increases →if the concentration difference is greater, there will be more particles to move from the region of higher concentration to the region of lower concentration. The difference in the concentration of a substance between two areas is called the concentration gradient. The bigger the difference, the steeper the concentration gradient and the faster the molecules of a substance will diffuse. Molecules diffuse down a concentration gradient. MODELLING DIFFUSION Cell membranes control what enters and leaves the cell. It is described as partially permeable. It allows small molecules to pass through it. Starch for example is too big to pass through a cell membrane but after it is digested and turns into glucose it can. Moving down the concentration gradient means that a molecule moves from a high concentration to a low concentration Practise question Two gases are kept separate, as shown below. If they are allowed to mix, in which direction will each of the gases diffuse? Explain your answer. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ __________________________________________ Living organisms obtain many of their requirements by diffusion. They also get rid of many of their waste products this way. Diffusion is important in gas exchange for respiration in animals and plants. Some products of digestion are absorbed from the ileum by diffusion. OSMOSIS Osmosis is the net movement of water molecules from an area of higher water potential to an area of lower water potential across a partially permeable membrane If a plant cell is put into pure water or a dilute solution, the contents of the cell has a lower water potential than the external solution, so the cell will absorb water by osmosis. The vacuole will get bigger so the cell swells up and the cytoplasm and cell membrane pushes against the cell wall. A plant cell that has developed an internal pressure like this is called turgid. If an animal cell was to become too swollen they would burst because they do not have a cell wall supporting them. Turgor (the start the plant is in when its cells are turgid) is very important to plants. Turgor supports the non-woody parts of the plant, such as stems. and leaves so that the leaves can carry out photosynthesis. If a plant loses so much water from its cells that it becomes shrunken it will make the plant wilt. On the other hand, if the cell is placed in a concentrated sucrose solution that has a lower water potential than the cell contents, it will lose water by osmosis. The cell decreases in volume and the cytoplasm no longer pushes against the cell wall. In this state, the cell is called flaccid. Eventually the cell contents shrink so much that the membrane and cytoplasm split away from the cell wall and gaps appear between the wall and the membrane. A cell like this is called plasmolysed. Comparing diffusion and osmosis ​ In diffusion and osmosis molecules move from a higher concentration to a lower concentration down a concentration gradient ​ Osmosis requires a partially permeable membrane whilst diffusion does not ​ Osmosis is the movement of water molecules, whilst diffusion is the movement of any molecules or ions. OSMOSIS IN RED BLOOD CELLS Red blood cell in Red blood cell in same Red blood cell in dilute concentrated solution water potential (high water potential) (low water potential ) solution Water molecules will There will be no net Water will enter the red leave.. the red blood cell movement of water blood cell by osmosis by osmosis as there is a molecules in or out of because water lower water potential the red blood cell as the molecules will move inside the cell and a water potentials are from the higher water higher water potential similar inside and potential outside the cell surrounding it. The outside the cell. The red to the lower water water molecules cross blood cell will remain in potential inside the cell the partially permeable its normal biconcave to access the partially cell membrane of the shape. permeable cell red blood cell as they membrane. leave ACTIVE TRANSPORT In diffusion and osmosis, particles move from an area of high concentration to an area of low concentration until an equilibrium is formed. At this point, there's no more net movement of molecules or ions because there's no concentration difference driving their movement. This means that no useful ions or molecules can be absorbed. Active transport is the movement of molecules into or out of a cell through the cell membrane, from a region of low concentration to a region of high concentration. The molecules move against the concentration gradient , using energy released during respiration. Active transport requires a protein carrier present in the cell membrane. A SOLUTE molecule binds to a protein CARRIER that is located in the MEMBRANE of a cell that will carry out active transport. For example magnesium ION bind to a protein carrier in the cell membrane of a ROOT HAIR cell of a plant. Once bound to the protein carrier, the protein carrier changes SHAPE and moves the solute molecule from a region of LOW concentration (outside the cell) to a region of high concentration (inside the cell). To change the shape of the carrier protein energy is required. The energy comes from a small molecule called atp (adenosine triphosphate). When ATP is split into ADP (adenosine diphosphate) and P (phosphate), a small quantity of energy is released- this causes the shape of the carrier PROTEIN to change. Once the solute has been moved ACROSS its concentration GRADIENT the protein carrier changes back to its original shape and can bind to another molecule. Mitochondria is more prevalent in cells where active transport occurs more frequently. Mitochondria is the site of respiration in cells, therefore more energy will be released. This is a positive correlation because as the rate of respiration increases so does the rate of active transport. As the rate of respiration increases more energy is released (ATP produced). ATP is needed to move molecules against their concentration gradient/ for active transport. If more energy ( ATP) is available then the rate of active transport will increase. SURFACE AREA TO VOLUME RATIO Step 1 Surface area= length X height X 6 Surface area= 2 X 2 X 6 Surface area = 24 cm2 Step 2 Volume = length X height X depth Volume= 2 X 2 X 2 Volume = 8 cm3 Step 3 24 : 8 24/8 : 8/8 3:1 Cube size / cm Surface area / Volume / cm3 Surface area: cm2 volume 1 6 1 6:1 2 24 8 3:1 3 54 27 2:1 4 96 64 1.5 : 1 5 150 125 1.2:1 6 216 216 1:1 7 294 343 0.9 : 1 Larger organisms have a bigger surface area to volume ratio whilst smaller organisms have a smaller surface area to volume ratio. Topic 2: Gas Exchange STRUCTURE OF THE THORAX The thorax is the space enclosed by the ribcage and the diaphragm. The gas exchange system responsible for allowing oxygen to enter the body and the waste gas carbon dioxide to be removed. The lungs are enclosed in the chest or thorax. By the ribcage and a muscular sheet called the diaphragm. As you will see in future lessons, the actions of these two structures bring about movements of air into and out of the lungs. Joining each rib to the next are two sets of muscles called intercostal muscles. The diaphragm separates the contents of the thorax from the abdomen. When we breathe in, air enters our nose or mouth and passes down the windpipe in the trachea. The trachea splits into two tubes called bronchi (singular bronchus), one leading to each lung. Each bronchus divides into smaller and smaller tubes called bronchioles , eventually ending at the microscopic air sacs called alveoli. It is here that gas exchange with the blood takes place. The inside of the thorax is separated from the lungs by two, moist membranes called the pleural membrane. They make up a continuous envelope around the lungs, forming an airtight seal. Between the two membranes is the pleural cavity, filled with a thin layer of liquid called pleural fluid. This acts as a lubrication, so that the surfaces of the lungs don't stick to the inside of the chest wall when we breathe in. The trachea has C- shaped rings of cartilage along its length to keep the airway open when you bend your neck and to keep the trachea open when you breathe in. CELLS IN THE THORAX The tissue lining the inner surface of an organ is called the epithelium. There are three types (shapes) of epithelial tissues, two of which are located in the lungs. Shape of epithelial cells Where can these epithelial How are they adapted for shown cells be found in the their function? lungs? Squamous --thin and flat Alveoli Short pathway for diffusion of gases Columnar ​ Goblet cells of ​ Goblet cells make trachea and bronchi mucus to trap ​ Ciliated cells of microorganisms trachea and bronchi ​ Ciliated cells have cilia to move mucus out of trachea The trachea contains two types of specialised cells. These are called goblet cells and ciliated cells. Goblet cells produce mucus.; a sticky substance made from protein and carbohydrates. Mucus helps to trap dust and pathogens before they can get deep into the alveoli. Cilia are tiny hairs that can move the mucus up and out of the trachea. A diagram of these cells is shown: Air moves down the trachea, through the bronchus. and bronchioles, and finally into the alveoli. These are small air sacs that allow oxygen from the air to diffuse into the blood and enter the red blood cells. The oxygen is needed for aerobic respiration The gas carbon dioxide produced inside cells during respiration passes from the blood plasma into the alveoli The movement of oxygen into the blood from the alveoli and the movement of carbon dioxide into the alveoli from the blood is called gas exchange. THE MECHANISM OF BREATHING The purpose of ventilation is to get oxygen into the red blood cells so that it can be carried to all the cells of the body for aerobic respiration. Breathing also removes the carbon dioxide that is produced in aerobic respiration. This is important because carbon dioxide is an acidic gas and would make the pH of the body fluids very low. Ventilation means moving air in and out of the lungs. This requires a difference in air pressure - the air moves from a place where the pressure is high to one where the pressure is low. Ventilation depends on the fact that the thorax is an airtight cavity. When we breathe, we change the volume of the thorax, which alters the pressure inside it. This causes air to move in or out of the lungs. Gas particles in a small container collide with each other and the surface of the container which causes them to gain kinetic energy. And as they gain energy the faster they move which causes pressure to build as they have nowhere to go so pressure can’t be released. As volume increases the pressure decreases, provided the number of particles remains constant. Particles move to equalise the pressure. Air particles move from higher to lower pressure until the pressure is equal. The unit for pressure is the pascal (Pa) Ventilation in the lungs Action during inhalation Action during exhalation External intercostal contract relax muscles Internal intercostal relax contract muscles ribs Move up and out Move down and in Diaphragm Diaphragm muscles contract and Diaphragm muscles relax and diaphragm flattens diaphragm dome shaped Volume of thorax Increases Decreases Pressure in thorax decreases increases Volume of air in the Increases Decreases lungs When we breathe in, the volume of the thorax increases. The pressure inside the lungs is now lower than the air (or atmospheric) pressure. Air moves into the lungs to equalise the pressure. LUNG VOLUMES A machine called a spirometer is used to measure the volume of air breathed in and out: A graph is produced from the spirometer called a spirometer trace. On the trace above, the subject took a deep breath in. This is to find out the Vital capacity which is the maximum volume of air that can be breathed out after breathing in as much air as possible. Taking part in regular aerobic exercise has been shown to increase a person's vital capacity. 1.​ Work out the tidal volume in dm3: 10/15→0.67 dm3 2.​ Work out the vital capacity in dm3: 45/15→3 dm3 3.​ Assuming the person kept breathing at the same rate as for the first 3 breaths, what would their breathing rate per minute be? 12 breaths per minute 4.​ Work out the ventilation rate for the person (the equation to work this out is given above): 0.67 x 12 = 8.04 During exercises the demand for oxygen increases and so the breathing rate increases as more oxygen is needed by the muscle cells, the oxygen is needed for a higher rate of aerobic respiration so more energy is released and energy is needed for muscle contraction THE EFFECTS OF SMOKING ON THE LUNGS Smoking is associated with lung cancer, bronchitis and emphysema. It is also a major contributing factor to other conditions, such as coronary heart disease and ulcers in the stomach and intestine Bronchitis -​ In order for the lungs to exchange gases properly, the air passages need to be clear, the alveoli need to be free from dirt particles and bacteria, and they must have as large a surface area as possible in contact with the blood. -​ The lungs are kept free from particles of dirt and bacteria by the action of mucus and cilia. In the trachea and bronchi of a smoker, the cilia are destroyed by the chemical in the cigarette smoke. The reduction in the number of cilia means that mucus is not moved away from the lungs. -​ This is made worse by the fact that the smoke irritates the lining of the airways, stimulating cells to secrete more mucus. The sticky mucus blocking the airways is the source of the ‘smoker’s cough’ -​ Irritation of the bronchial tree, along with infections from bacteria in the mucus, can cause the lung disease bronchitis. Bronchitis blocks normal air flow, so the sufferer has difficulty breathing.​ Emphysema -​ Smoke damages the walls of the alveoli, which break down and fuse together again from large , irregular air spaces. This greatly reduces the surface area for gas exchange. -​ The blood of a person with emphysema has a low oxygen concentration. In serious cases this leads the sufferer to be unable to carry out even mild exercise, such as walking. Emphysema patients often have to have a supply of oxygen nearby at all times. There is no cure for emphysema. Carbon monoxide in smoke -​ One of the harmful chemicals in cigarette smoke is carbon monoxide. When the gas is breathed in with smoke it enters the bloodstream and integers with the ability of the blood to carry oxygen. -​ Oxygen is carried around the blood in red blood cells attached to a chemical called haemoglobin. Carbon monoxide can combine with haemoglobin to form a compound called carboxyhemoglobin. The carbon monoxide binds more strongly to the haemoglobin than oxygen, limiting the oxygen carrying capacity of the blood *If a pregnant woman smokes, she will be depriving her unborn foetus of oxygen. This affects the growth and development and leads to the mass of the baby being lower, on average, than the mass of babies born to non- smoking mothers.* BREATHING RATE AND EXERCISE The word and symbol equation for aerobic respiration is glucose + oxygen → carbon dioxide + water / C6H12O6 + 6O2 → 6CO2 + 6H2O The word equation for anaerobic respiration is glucose → lactic acid -​ Aerobic respiration occurs in the mitochondria -​ Anaerobic respiration occurs in the cytoplasm During anaerobic respiration, lactic acid is formed which is what causes your muscles to ‘burn’ The term ‘lactate threshold’ is when the blood lactate accumulates, anaerobic respiration becomes the predominant process and it starts to get more and more difficult to keep doing the activity. The breathing rate remains increased for a few minutes after you have exercised to pay back the oxygen debt. The lactic acid produced by anaerobic respiration needs to be broken down requiring oxygen. During exercise the muscle needs energy to contract The muscle cells therefore respire more than they do at rest. Several changes happen in the body to enable this increase in the rate of respiration. -​ The breathing rate and the volume of each breath increases to maximise the diffusion of oxygen into the blood and the removal of carbon dioxide from the blood. -​ The heart rate increases so that glucose and oxygen can be delivered to the cells more quickly and to remove the carbon dioxide produced. -​ If insufficient oxygen is available to the muscles, for instance the exercise is vigorous and/or prolonged, the heart and lungs are unable to supply sufficient oxygen. Muscles begin to respire anaerobically. Lactate(also known as lactic acid) is produced from glucose, instead of carbon dioxide and water. Muscles continue to contract, but less efficiently. -​ When you stop exercising there is lactic acid. in your muscles and your blood. This lactic acid needs to be broken down by combining it with oxygen So your breathing rate is still high even after you have finished exercising. You are taking in oxygen to break down the lactic acid into carbon dioxide and water. Not until all the lactic acid has been used up, does your breathing rate and heart rate return to normal (resting rate) -​ HOW A LEAF IS ADAPTED FOR GAS EXCHANGE Name of part of leaf Structure Function Waxy cuticle A thin layer of waxy material. It reduces water loss by evaporation and acts as a barrier to the entry of microorganisms that can cause disease. Upper epidermis A tissue made from a single layer of Allows light to the palisade mesophyll transparent cells that contain no below and produces the waxy layer. chloroplasts. Palisade mesophyll A tissue made from elongated cells, Where the majority of photosynthesis each containing hundreds of occurs. Light is absorbed by chlorophyll in chloroplasts. the chloroplasts - produces glucose! Spongy mesophyll A tissue made from moist, rounded These cells form the main gas exchange loosely packed cells with air spaces. surface of a leaf. The moisture allows the gases to dissolve and enter the cells. The air spaces allow the gases to diffuse to all of the cells in the mesophyll layers. Lower epidermis This is a tissue at the bottom of a leaf and The pores allow carbon dioxide to diffuse it contains small pores called stomata. into the leaf to reach the photosynthetic tissues. They also allow oxygen and water vapour to diffuse out. Guard cells Highly specialised cells located mainly in To open and close the stomata. the lower epidermis. These cells form the stomata. Xylem A tissue consisting of dead-cells arranged Carries water and minerals to the leaf. end-to-end and strengthened with a waterproof substance called lignin. Phloem A tissue consisting of living cells joined Carries sugars and amino acids to and from end to end with perforations between the the leaves to other parts of the plant. cells to allow the movement of substances between them. Large surface area More light can be absorbed by Allows space for stomata on the underside chlorophyll in the chloroplasts as there is of the leaf for carbon dioxide to enter the a larger SA of the leaf for light to hit. leaf. Thin Light can travel through to all the Short diffusion distance for carbon photosynthesising cells dioxide to diffuse from the stomata on the underside of the leaf to the palisade mesophyll cells at the top of the leaf where the most photosynthesis occurs. STOMATA Gases enter plants via the leaves. The underside of a leaf (the lower epidermis) and has tiny pores (holes) called stomata that allow gas exchange. The upper epidermis may also contain stomata. Each stoma (hole) is made when two specialised cells called guard cells fill with water and become turgid. When water enters these cells they curve apart to make the stoma. The stomatal pore is the gap between the guard cells when the stomata open allowing carbon dioxide to diffuse into the leaf Light causes the stomata to open. This is useful because photosynthesis occurs during the light so that is when a supply of the reactant carbon dioxide is required. In the dark when photosynthesis is not occurring the stomata close to limit the loss of water vapour by transpiration. Stomata open in the light and close in the dark In the light the stomata open This occurs by water entering the guard cells by osmosis. (This happens because potassium ions enter the guard cells decreasing the water potential). Because the inner wall of each guard cell is thicker they form a curved shape when turgid, resulting in a stomatal pore / stoma forming between them. When open carbon dioxide can diffuse into the leaf through the stomata down its concentration gradient. Oxygen diffuses out down its concentration gradient as does water vapour. In the dark the stomata close. This is to limit the loss of water vapour. as carbon dioxide is not required as photosynthesis cannot occur in the dark. They close by water leaving the guard cells by osmosis and becoming flaccid. When the guard cells are flaccid they are positioned side by side closing the stomatal pore. Topic 3: The variety of living organisms PROTOCTISTS, BACTERIA AND VIRUSES AND PLANTS Protoctists Protoctists are microscopic single-celled organisms. Some, like Ameoba, that live in pond water, have features like an animal cell, whilst others, like Chlorella, have chloroplasts and are more like plants. A pathogenic example is Plasmodium, responsible for causing malaria. Bacteria These are microscopic single-celled organisms; they have a cell wall, cell membrane, cytoplasm and plasmids*; they lack a nucleus but contain a circular chromosome of DNA; some bacteria can carry out photosynthesis but most feed off other living or dead organisms. Examples include Lactobacillus bulgaricus, a rod-shaped bacterium used in the production of yoghurt from milk, and Pneumococcus, a spherical bacterium that acts as the pathogen causing pneumonia. *Plasmids - A plasmid is a small, circular DNA molecule found in some bacteria and other organisms. Viruses These are not living organisms. They are small particles, smaller than bacteria; they are parasitic and can reproduce only inside living cells; they infect every type of living organism. They have a wide variety of shapes and sizes; they have no cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA. Examples include the tobacco mosaic virus that causes discolouring of the leaves of tobacco plants by preventing the formation of chloroplasts, the influenza virus that causes ‘flu’ and the HIV virus that causes AIDS. All viruses are pathogens and are parasitic. A parasite is something that lives off another organism and causes it harm. A pathogen is a microorganism that causes disease. Viruses have a wide variety of sizes and shapes, but they all have in common a protein coat and one type of nucleic acid, which is either DNA or RNA, but not both. Plants These are multicellular organisms; their cells contain chloroplasts and are able to carry out photosynthesis; their cells have cellulose cell walls; they store carbohydrates as starch or sucrose. Eukaryotic and prokaryotic cells  Biologists classify cells and organisms as either prokaryotic or eukaryotic. Prokaryotic cells are bacterial cells. Plants, animals, fungi and protoctists are eukaryotic. Viruses are neither prokaryotic or eukaryotic because they are not made of cells and are not living. Prokaryotic cells are simpler cells that do not have a proper nucleus like eukaryotic cells do; that means they do not have chromosomes, but they have a circular loop of DNA (which is sometimes called a circular chromosome of DNA). They also have smaller circular loops of DNA called plasmids, that often contain the genes for antibiotic resistance. Prokaryotic and eukaryotic cells have some features in common: a cytoplasm, a cell membrane, ribosomes and, if present in eukaryotic cells, a cell wall. Cell 1 Cell 2 Diagram Prokaryotic or Prokaryotic eukaryotic eukaryotic? Example of bacteria animal cell, plant cells, fungus cell - e.g. plant, bacteria, fungus or protoctist FUNGUS  These are organisms that are not able to carry out photosynthesis; their body is usually organised into a mycelium made from thread-like structures called hyphae, which contain many nuclei; some examples are single-celled; their cells have walls made of chitin; they feed by extracellular secretion of digestive enzymes onto food material and absorption of the organic products; this is known as saprotrophic nutrition; they may store carbohydrate as glycogen. Examples include Mucor, which has the typical fungal hyphal structure, and yeast, which is single-celled. Saprotrophic nutrition - The organisms, e.g fungi and bacteria, that feed on the dead and decaying organisms are called saprotrophs. These organisms perform external digestion where they break down the complex nutrients in the dead organism by releasing enzymes outside. Letter Name Function - complete the sentence if needed. A cell wall Made from chitin Provide strength for the cell B cytoplasm Chemical reactions happen here. C Nucleus There are many of this organelle inside fungal cells, they are therefore called multinucleate. D vacuole Stores many biological molecules for the cell. Practise questions How would a fungus digest a peach The fungus is digesting the peach by releasing extracellular enzymes Protease: protein digested to amino acids Amylase: starch digested to maltose Maltase: Maltose digested to glucose lipase: lipids digested to fatty acid and glycerol Compare and contrast the structure of a plant cell and the structure of a fungal cell. Both plant and animal cells have a cell wall. Plant cells have a cell wall made of cellulose, fungal cells have a cell wall made of chitin. Plants cells have chloroplasts whereas fungal cells do not A plants cell has one nucleus whereas fungal cells have many nuclei Decomposition is faster when it is warmer As the temperature increases the enzyme and the substrate have more kinetic energy. There will be more frequent successful collisions. More enzyme substrate complexes. Decomposition will occur at a faster rate. Up until the optimum temperature. After the optimum temperature the enzyme will denature. The substrate can no longer bind to the active site.. The rate of decomposition will decrease DECOMPOSITION  Decomposition is an important process in the carbon and nitrogen cycle. It is the way in which microorganisms (bacteria and fungi) break down dead organisms using extracellular digestion. Decomposers secrete enzymes onto the surface of the dead organism and digest it outside of their cells. This is known as saprotrophic nutrition. The products of these extracellular digestion reactions are absorbed back into the microorganisms by diffusion and are used for respiration, growth and reproduction. Terminology Definition Saprotrophic It is where fungi secrete extracellular enzymes into the area outside their body (on to dead organic matter) to digest their food and absorb the soluble products. Extracellular This is where the digestion occurs outside of cells. digestion In the carbon cycle decomposers digest complex carbon compounds and use the absorbed products for respiration. Respiration releases carbon dioxide into the atmosphere. How does mucor affect a piece of bread The hyphae secrete enzymes that digest the bread. The products from this digestion are then absorbed by the fungus. Saprotrophic figures such as mould obtain their food by releasing enzymes that feed on dead or decaying organisms. They then absorb the digested food. Organism Structure Chloroplast Cytoplasm Cell wall Nucleus Fungus x ✓ ✓ ✓ Bacteria X ✓ ✓ X Virus x X X x  Topic 4: Transport in humans THE NEED FOR A TRANSPORT SYSTEM Cut three different sized agar jelly cubes. The cubes are coloured due to the presence of universal indicator, which is green in neutral conditions. You will place the different sized cubes in acid and time how long it takes for the cubes to become red. 1.​ Why were the cubes green at the start of the experiment? They are dipped in a universal indicator which is green in neutral pH. 2.​ Why did the cubes turn red when placed in the acid? Use these terms in your answer: Diffused, acid, concentration gradient. The hydrochloric acid diffused into the cube from a higher concentration outside to a lower concentration inside(down the concentration gradient). The acid caused the pH to decrease and so the universal indicator turned pink. 3.​ What is the relationship between the SA:V and the time taken for the cube to turn entirely pink (all the green to disappear)? The larger the surface area to volume ratio the shorter the time taken for all the green colour to disappear. 4.​ Imagine the cubes were organisms and the acid was oxygen. a)​ Which process inside all cells requires oxygen? Aerobic respiration. b)​ Where in a cell does this process occur? Mitochondria c)​ Which of the cubes (organisms) would get oxygen to all its cells the fastest? Smallest one (has the largest SA:V) d)​ What evidence in your results table supports your answer to part c? It has the shortest time for the green colour to disappear and become pink. e)​ If cells do not receive sufficient oxygen what will happen to them? Switch to anaerobic respiration but this provides less energy to the cell so if still no oxygen They would die. f)​ In which of the organisms might the cells die before sufficient oxygen reaches them? Refer to SA:V in your answer. Larger organisms would die if they relied solely on diffusion as they have the smallest SA:V. The diffusion distance would be too long for all of their cells to get oxygen and to remove CO2 fast enough; this is why they require a gas exchange system and a circulatory system. g) Complete this paragraphs by filling in the missing words. Small organisms have a large SA:V. They can obtain the materials e.g. oxygen they need by diffusion. Larger organisms have a small SA:V. Diffusion is too slow for materials to reach all the cells by this mechanism. For this reason they require a way to transport substances to all cells. In humans this transport system consists of the heart, blood vessels and blood STRUCTURE AND FUNCTION OF THE HEART The heart is a pump.It pumps blood around the body. It is made of a special type of muscle called cardiac muscle. The two upper chambers are called the atria. The two lower chambers are called the ventricles. The chambers on the left - hand side are completely separated from the ones on the right- hand side by the septum. The function of the heart is to pump deoxygenated blood to the lungs to be oxygenated and then to pump the oxygenated blood around the body. The heart is located in the centre of the chest (slightly to the left of your breastbone) The function of the vena cava is to return deoxygenated blood from the body to the heart where it enters the right atrium. The blood passes from the atria to the ventricle through the atrioventricular valves (tricuspid valve on the right and the bicuspid valve on the left). The atria contracts pushing the blood through to the ventricle The pulmonary artery goes to the lungs The function of the semilunar valves is to shut, preventing blood from flowing backwards from the arteries leaving the heart (aorta and pulmonary artery) back into the ventricles The blood become oxygenated in the lungs (alveoli) The pulmonary vein returns oxygenated blood from the lungs to the left atrium. The left ventricle has the thickest wall (more muscle). This is because it has to generate the highest pressure in order to push the blood the greatest distance around the body (systemic circulation). The function of the ‘heart strings’ is to hold the atrioventricular valves in place and prevent them from inverting. Through the aorta, oxygenated blood leaves the heart Our cells need oxygen for aerobic respiration. BLOOD FLOW THROUGH THE HEART Blood is moved through the heart by a series of contractions and relaxations of the muscle in the walls of the four chambers. The left side of the heart pumps blood to the body (systemic circulation). To provide the cells throughout the body with oxygen (and glucose) for aerobic respiration. The left side of the heart pumps blood to the lungs (pulmonary circulation. So that the blood becomes oxygenated (oxygen binds to haemoglobin in red blood cells becoming oxyhaemoglobin). Valves prevent blood from flowing backwards in the wrong direction. Valves close when the pressure after the valve exceeds the pressure before it. The path for blood from the vena cava to the aorta is vena cava - right atrium - right ventricle - pulmonary artery - lungs - pulmonary vein - left atrium - left ventricle - aorta.  HEART DISEASE The coronary arteries branch off of the aorta, they are there to supply oxygen and glucose to the cells in the heart for aerobic respiration. The coronary arteries becoming blocked is what causes a heart attack as it restricts blood flow to the heart muscle. This deprives the heart of oxygen and nutrients, leading to damage or death of heart tissue. The lack of oxygen-rich blood triggers a cascade of events, including inflammation and the formation of blood clots, which can ultimately result in a heart attack. The blockage of coronary arteries involves the buildup of fatty material in the walls of arteries narrowing the lumen (space in the middle of the) artery and reducing blood flow along the artery. Coronary heart disease One of the main causes of coronary heart disease is atherosclerosis. This is the thickening of the inner layer of the arterial walls with deposits of cholesterol. These deposits are referred to as atheroma and often become calcified and hardened, this causes the arteries to lose elasticity. As the atheroma enlarges, it bulges into the lumen of the artery, causing it to narrow and so reduces the rate of blood flow (atherosclerosis). Atherosclerosis is where fatty material builds up in the wall of an artery narrowing the lumen. This can occur in the coronary arteries leading to insufficient blood and therefore oxygen and glucose reaching the cardiac muscle cells of the heart. The muscle cells need the oxygen for aerobic respiration to allow them to contract. Without sufficient oxygen muscle cells in the heart may die affecting how the blood pumps blood. It may be that the atherosclerosis caused narrowing of an artery outside the heart and a thrombus (blood clot) occurred there which then got dislodged and moved to block the lumen of a coronary artery. Cigarette smoke Cigarette smoke weakens the lining of the blood vessel. Nicotine increases heart rate and blood pressure, and constricts (narrows) blood vessels. Carbon monoxide in smoke reduces the oxygen- carrying capacity of the blood. These factors combined put a stress on the heart, accelerate the development of atherosclerosis and increase blood pressure  THE EFFECT OF EXERCISE ON HEART RATE There are only certain places on the body where it is possible to feel a pulse. This is because the artery needs to be close to the surface of the skin and easily compressed against a hard structure below (eg a bone). The reason you feel a pulse is the blood travelling through the artery you are pressing on. The pulse rate equals the heart rate as each contraction of the left ventricle results in the surge of blood travelling through the arteries. Resting pulse rate - The pulse rate when an individual is not exercising, sitting down calmly. The reason heart rate increases when you exercise is Blood must be delivered more quickly to muscles The demand for oxygen/glucose increases For more aerobic respiration To release more energy Required for increased muscle contraction The graph shows the heart rate of a fit person and of an unfit person at rest, during exercise and after exercise. (a) (i) Compare the heart rate of the fit person with the heart rate of the unfit person from 5 to 15 minutes. The unfit persons heart rate is faster, however both the fit and the unfit persons heart rate peaked after 10 minutes, however the unfit person peaked at 140 bpm and the fit person peaked at 110 bpm. (ii) The recovery period is the time it takes for the heart rate to return to its rate at rest after exercise. Explain why the recovery period for the fit person was different from the recovery period for the unfit person. -​ A fit person's heart and circulatory system are more efficient. Their heart can pump more blood with each beat, delivering oxygen and nutrients to the muscles more effectively. This means their body can clear out waste products like carbon dioxide and lactic acid faster, leading to a quicker recovery. -​ -​ Fit people usually have a lower resting heart rate because their heart is stronger and more efficient. When they exercise, their heart rate doesn't need to increase as much as that of an unfit person. After exercise, it returns to the lower resting rate more quickly. -​ -​ The muscles of fit people are better conditioned. They experience less damage and produce fewer waste products during exercise, leading to a shorter recovery period. ADRENALINE​ When you are frightened, excited or angry your adrenal glands secretes the hormone adrenaline. Adrenaline acts at a number of different target organs and tissues, preparing the body for action. If an animal’s body is going to be prepared for action, the muscles need a good supply of oxygen and glucose for aerobic respiration. Adrenaline produces several changes in the body that might make this happen as well as other changes to prepare for fight and flight. Organ Effect Lungs Breathing rate increases and volume of each breath increases. Heart Heart rate increases Intestines Blood is diverted away from the intestines and into the muscles Liver Stored glycogen is changed into glucose and released into the blood. Eye The pupils dilate, increasing visual sensitivity for movement. Brain Mental awareness is increased, so reactions happen faster Skin Body hair stands upright, making the animal look larger to an enemy. Adrenaline is dissolved in the blood plasma to be carried to the target organs Adrenaline is released during exercise and it causes an increase in breathing rate and heart rate. Meaning there is more oxygen in the blood, so therefore is delivered more quickly to muscles for aerobic respiration so they can contract COMPONENTS OF THE BLOOD Blood carries oxygen and nutrients to living cells and takes away their waste products. It also delivers immune cells to fight infections and contains platelets that can form a plug in a damaged blood vessel and prevent blood loss. Adaptation Purpose Biconcave  Increases the surface area to volume ratio. This provides a proportionally larger surface area for diffusion of oxygen into and out of the cell. This speeds up diffusion. No nucleus Therefore more space for haemoglobin and more oxygen can be carried. Haemoglobin An iron containing protein that binds to oxygen in the lungs where the oxygen concentration is high and releases it to the tissues where the oxygen concentration is low. Haemoglobin + oxygen oxyhaemoglobin Thin Thin so that there is a short diffusion distance to the centre of the cell AND a thin cell surface membrane which allows oxygen to diffuse through rapidly. So increases the rate of diffusion of oxygen into and out of the cell. There are two types of white blood cell ​ Lymphocytes which produce antibodies ​ Phagocytes which engulf and digest bacteria It consists of about 90% water and about 10% of a wide variety of dissolved substances. including, digested food molecules (glucose and amino acids), wastes such as dissolved carbon dioxide and urea, salts and hormones. It is fluid as it is the transport medium for the cells. Platelets are fragments of cells and are involved in the process of blood clotting. Blood clotting is important because it prevents an organism losing large volumes of blood if it is injured and the clot formed prevents the entry of microorganisms. Platelets are shaped like a flattened disc and they do not have a nucleus. When platelets detect damage they change from smooth flattened discs into tiny spheres with many long thin arms. Their surface becomes sticky and they adhere to cut surfaces of tissue. The platelet also releases chemicals that cause a protein called fibrin to form a web of threads over the cut surface. ARTERIES ​ The artery has much thicker walls than the vein which has thinner walls. ​ The vein has a wider lumen than the artery which has a narrower one. ​ There is more smooth muscle and elastic fibres in  the wall of arteries than veins. ​ Veins have valves to prevent the backflow of blood whereas arteries do not (except in the heart). ARTERIES CAPILLARIES VEINS Function is to carry blood from Function is to allow Function is to carry blood from the heart to the tissues. exchange of materials tissues to the heart. between the blood and the tissues. Thick walls Very thin, permeable walls, Thin walls, mainly collagen, Elastic layers to maintain the only one cell thick to allow since blood pressure is lower. pressure , and muscle tissue to exchange of materials. change lumen size, changing blood flow to organs. narrow lumen. Very small lumen, blood Wide lumen to reduce the cells must distort to resistance of blood flow. squeeze through. No valves (except in the heart). No valves. Many valves to prevent back_flow. Blood at high pressure. Blood pressure falls in Blood at low pressure. capillaries. Blood is usually oxygenated Blood changes from Blood is usually deoxygenated (except in pulmonary arteries ). oxygenated to (except in the pulmonary vein). deoxygenated (except in the lungs). The arteries' walls stretch due to the contraction of ventricles, allowing blood to enter. The elastic tissue in the arteries allows them to re-stitch, a process called elastic recoil. This allows blood to push back and maintain blood pressure, crucial for reaching the body's extremities MOVEMENT OF BLOOD​ ​ (Left) ventricle wall contracts which causes the blood to enter the arteries at high pressure Elastic fibres in the wall of arteries recoil giving the blood another push to maintain the pressure.  To push the blood back to the heart, the blood needs to be put under pressure. Most veins are situated between skeletal muscles (muscles that move the skeleton). When the skeletal muscles contract they squeeze on the vein that reduces its volume. The decrease in volume increases the blood pressure, forcing the blood from a region of high to a region of low pressure. The blood can only travel in one direction i.e. upwards because valves stop it travelling backwards. Deep vein thrombosis Thrombosis is blood clotting.Deep vein thrombosis involves a clot forming in a vein in the leg but it might dislodge and get moved to the heart. If a clot gets stuck in an artery and blocks the lumen it will limit the flow of blood through. Deep vein thrombosis is more likely to occur on a long aeroplane flight due to the lack of movement, meaning there is a less skeletal muscle contraction which is what helps to move blood through the veins, when the blood isn't moving it makes it more likely to clot Passengers are told to touch their toes, lift their knees, stand up and move, so skeletal muscles can contract more. Blood clotting usually occurs in the legs, the main danger is that part of the clot may break off and travel up to the lung, blocking small blood vessels and causing death. It could also travel to the heart and block an artery, blocking the lumen and therefore limiting blood flow. TISSUE AND LYMPH FLUID​ ​ Tissue fluid, formed from blood plasma, is the fluid which surrounds the cells in tissues. It is used to exchange nutrients and gases between cells of the body and the blood in the circulatory system. Because the pressure is so high in the capillaries, it pushes some of the liquid part of the blood (blood plasma) out of the capillaries and into the surrounding cells. Blood cells and proteins are too big to leave the capillary. The reason that the blood plasma and the tissue fluid are different is because plasma contains protein and the tissue fluid does not because proteins are too big to leave the capillaries. The tissue fluid re enters the capillary where the pressure is lower, at this point glucose, oxygen, minerals, vitamins, fatty acids glycerol, amino acids have dissolved in the tissue fluid More water leaves the capillaries into the tissue than can re-enter the capillary at the end of the capillary bed. If this extra fluid is not removed it results in swelling of the tissues. Excess tissue fluid is drained into another type of vessel called lymph vessels. These are part of the lymphatic system. The lymphatic system is like our body's 'sewerage system' Whilst it flows around the body, the lymph nodes monitor the lymph fluid flowing into them and produce cells and antibodies which protect our body from infection and disease. The lymph nodes act as ‘filters’, removing all the harmful substances and micro-organisms from the lymph fluid before it re-enters the bloodstream at the subclavian veins under the collar bone. Topic 5: Coordination and response NEURONS Receptors are specialised cells that detect and stimulate electrical impulses in response to stimuli. They are found in sense organs like the eye, while effectors are cells found in glands like the pancreas. The human nervous system consists of two things: -​ The central nervous system, this is the brain and spinal cord -​ The peripheral nervous system, extending from the spinal cord, consists of sensory and motor neurons that transmit electrical impulses from sense organs to the central nervous system. Sensory nerves carry electrical impulses from receptors in sense organs to the CNS. Motor nerves carry electrical impulses from the CNS to effectors. -​ They are long to cover large distances and thin so they do not take up much space. Sensory neurons begin with a receptor that detects a stimulus, converting it into electrical impulses received by dendrites. These dendrites form a dendron, with the cell body containing a nucleus and organelles. The electrical impulse is carried down the axon, wrapped in a myelin sheath, and divided into synaptic knobs at the terminal end. Motor neurons have a cell body in the CNS, with dendrites carrying impulses and an axon carrying electrical impulses. The axon's terminal end divides into synaptic bulbs, which transmit impulses to an effector like a muscle, causing muscle fibres to contract. SYNAPSES​ Synapses are gaps between motor, sensory, and relay neurons, where hundreds of tiny vesicles (sacs) contain neurotransmitters. When an electrical impulse travels along an axon, these vesicles empty into the gap between the two neurons, the synapse, allowing neurotransmitters to diffuse across the gap and attach to receptors on the next neuron's membrane, triggering an action potential. Synapses ensure that nerve impulses can only go in one direction along neurones, with the vesicles released on one side and receptors on the other side. If one neuron has synapses with several others, electrical impulses can pass to multiple areas of the body simultaneously. At a neuromuscular junction, neurotransmitters stimulate muscle contraction, while at a gland cell, they stimulate hormone release. 1 - An electrical impulse travels along the first axon. 2 - This triggers the nerve-ending of a neuron to release chemical messengers called neurotransmitters 3 - These chemicals diffuse across the synapse (the gap) and bind with receptor molecules on the membrane of the second neuron. 4 - The receptor molecules on the second neuron bind only to the specific neurotransmitters released from the first neuron. This stimulates the second neuron to transmit the electrical impulse. Drug 1: Curare Acetylcholine, a neurotransmitter, causes muscle contraction across synapses. Curare, a poison, prevents muscle contraction and can cause death if it enters the bloodstream. Drug 2: Prozac Blocks serotonin reuptake receptors, preventing low serotonin concentration in the synapse. Keeps serotonin concentration high enough to trigger an electrical impulse in the postsynaptic neuron. Drug 3: Nicotine Stimulants mimic neurotransmitters normally released into synapses, triggering electrical impulses. Bind to receptors on the postsynaptic membrane, triggering electrical impulses. Drug 4: Alcohol Reduces nervous transmission activity by inhibiting neurotransmitter binding to postsynaptic membrane receptors. Acts on synapses in the brain, affecting areas involved in worry, anxiety, balance, and conscious thought. REFLEXES​ ​ A reflex action is a response to a stimulus which is rapid and involuntary. Reflex actions produce a rapid response, which is important as many reflexes prevent damage to the body. Reflexes are rapid because only two or three neurons are involved in the pathway, reducing the number of synapses, which slow down nervous conduction. Reflexes also ensure essential body functions can continue eg digestion and breathing. Reflex actions follow a sequence through the nervous system, called the reflex arc, which does not involve the conscious brain, making them quicker and reducing body damage. Neurones are involved in the reflex arc that helps humans respond to stimuli. The diagram shows a reflex arc with p arts labelled A, B, C, D and E. The arrows show the direction of the nerve impulse. A - the receptor (detects the stimuli) B - sensory neuron (carries electrical impulse to the CNS) C - relay neuron D - motor neuron E - effector (causes either a muscle to contract or a gland to release an enzyme) IMPORTANT CALCULATION - % change = (final reaction time – initial reaction time)/initial reaction time Variables During an investigation, one variable is altered (independent variable); and the effect on another variable (dependent variable) is measured. Other variables which may affect the results of the investigation are kept constant or controlled, these variables are called the control variables. THE STRUCTURE OF THE EYE​ 1 cornea 2 iris 3 pupil 4 lens  5 retina 6 blind spot 7 optic nerve 8 sclera https://quizlet.com/gb/918639031/ PUPIL REFLEX Light enters the eye through the pupil and focuses onto the retina, where receptors are found. The retina contains rod and cone cells, which detect colour and black and white at different light intensities. This is what you would observe when you shine a bright light in the eye. The pupil is restricted so the eye can adjust the amount of light reaching the retina and therefore it can’t be damaged by too much light reaching it. When in dim light, the pupil dilate, allowing the eye to take in more light. It prevents the damage of the retina where there is too bright light and allows more light to reach the retina when there is dim light. In dim light the circular muscles relax and the radial muscles contract This causes the pupil to dilate and so more light reaches the retina. In bright light the circular muscles contract and the radial muscles relax. This causes the pupil to constrict and so less light reaches the retina. The effectors that change the size of your pupil are located in the iris and the receptors that detect the light change are in the retina The muscles work agonistically, thai means while one contracts the other relaxes and visa versa ACCOMODATION​ ​ Accommodation - is the name for focusing light when objects are different distances away The cornea and the lens are responsible for focusing light onto the retina -they do this by refractioning the light (make it change direction). The lens can change shape to focus objects that are close and far away.  When looking a near object the lens is more convex (fatter/thicker) and the suspensory ligaments are slack When looking at a distant object the lens become less convex (thinner) and the suspensory ligaments are taut The fovea and blind spot are both parts of the retina. The blind spot is the part of the retina that doesn’t have any light sensitive cells as this is where the optic nerve is. If light is focused here, you can’t see anythig. The fovea is the part of the eye that has the most light sensitive cells and so if light is focused here, you get the clearest image. The choroid is a layer of black tissue behind the retina and it absorbs any light not absorbed by the retina, thereby stopping light passing through the retina twice. SKIN AND THERMOREGULATION Part Name A Hair B Sebaceous gland (oil gland) C Hair erector muscle D Adipose tissue (fat layer) E Arterial  F Sweat gland G Dermis H Epidermis I pore J Hair follicle The human body cools down when too hot, triggered by changes detected by receptors and processed by the brain, with effectors being the parts causing the response. Core body temperature is maintained by vital organs like heart, lungs, brain, and liver, while extremities (for example hands or feet) can be slightly lower. The hypothalamus detects changes in blood temperature and sends nerve impulses to effectors like muscles or glands. Arterioles, small arteries, contract due to vasoconstriction,reducing the size of the lumen and therefore reducing blood flow through the skin's capillary network and reducing heat loss from radiation. Vasodilation is where the muscles relax, increasing the blood flow to the skin surface this way heat energy is lost from radiation, cooling the blood and therefore you Stimulus Increase in core body temperature Decrease in core body temperature Effector – muscle in Muscles relax allowing more blood to Muscles contract allowing less blood to arteriole in the skin flow into capillaries (vasodilation), so flow into the capillaries, meaning less more heat is lost by radiation. blood flows to the surface of the skin (vasoconstriction). Effector –sweat gland Release more sweat, which Release less sweat in the skin evaporates, taking heat away from the skin. Effector –skeletal Muscle relax Muscles contract and relax muscle -shivering-reflex. Respiration releases heat energy, increasing the body temperature. Effector –hair erector Hair lies flat as erector muscle relaxes, Hair erector muscle contracts- hairs are muscle in the skin pulled upright. Air is trapped between hairs and skin as thermal insulation. GLUCOSE HOMEOSTASIS The endocrine system refers to the glands that produce hormones that regulate body activities, secreted into the blood plasma and directed to target organs with receptors.  Letter Endocrine gland A Pituitary gland B Pancreas C Adrenal glands D Ovaries E Testes Endocrine control of blood glucose concentration Why is it a problem if your blood sugar gets too high? - This could cause water to move out of cells into the blood by osmosis causing the cells to shrink. What happens if the blood glucose is too high - e.g. after the digestion and absorption of a carbohydrate meal ​ The hormone insulin is released from the islets of Langerhans in the pancreas. ​ Insulin travels in the blood plasma to the liver and muscle cells ​ Insulin causes cells to take up more glucose. ​ Insulin causes cells in the liver and the muscles to convert the glucose to glycogen. Why is it a problem if blood sugar falls too low? - glucose is required for respiration in order to release energy, so cells will not be able to release sufficient energy by respiration. What happens if the blood glucose is too low - e.g. After fasting ​ The hormone glucagon is released from the islets of Langerhans in the pancreas ​ Glucagon travels in the blood plasma to the liver ​ Glucagon causes glycogen in the liver to be broken down into glucose and released into the blood plasma. Topic 7: Immunology PHAGOCYTOSIS -​ Pathogens are microorganisms that cause disease -​ Not all microorganisms cause disease, there are some non-pathogenic organisms. About 70% of your white blood cells can ingest (take in) and then digest and kill microorganisms such as bacteria. This process is called phagocytosis, and the cells that can do this are called phagocytes. Phagocytes have the same basic structure as all cells, except they have a nucleus that is lobed, rather than spherical Phagocytosis is called a non-specific immune response because it will kill all types of microorganisms that enter the body. The adaptation that phagocytes have for phagocytosis is that they are able to easily change their shape by changing the shape of their cell membrane and cytoplasm. To ingest a pathogen, they produce extensions of their cytoplasm called pseudopodia. The pseudopodia surround and enclose the micro-organism, engulfing it and placing it inside a vacuole, that is called a phagosome. Steps of phagocytosis 1.​ The pathogen is engulfed by the phagocyte by extensions of the cytoplasm called pseudopodia 2.​ The pathogen is enclosed by a vesicle called a phagosome 3.​ Enzymes are released into the phagosome that digest the pathogen 4.​ The products of the digestion are released from the cell LYMPHOCYTES AND ANTIBODIES​ ​ Specific immune responses are coordinated by white blood cells called lymphocytes. In a specific immune response the lymphocytes kill just one type of pathogen by producing chemicals called antibodies. Lymphocytes are able to respond to specific pathogens because pathogens have unique shaped proteins on their outer surface. These proteins are called antigens. Antibodies are proteins produced by lymphocytes which can attach to pathogens and help neutralise or destroy them. Antibodies consist of several chains of protein joined together to make a ‘Y’ shape structure. At the top of every antibody is a binding site. The binding site of an antibody is complementary to a specific antigen on the surface of each different pathogens. An antigen is a protein on the surface of a pathogen that lymphocytes can detect. The antibody is a Y shaped protein that, once bound to a pathogen, can have several effects: ​ Cause pathogens to stick together so phagocytes can ingest them more easily ​ Act as a label on the pathogen so it is more easily recognised by a phagocyte. When a lymphocyte recognises the antigen of a pathogen it starts to divide by a process called mitosis. This creates many genetically identical copies (clones) of the same lymphocyte. These cells then differentiate (specialise) into two types of cell. These cells are called plasma cells that produce identical antibodies, and memory cells. The memory cells remain in the body for many years. If you become infected with the same pathogen again, the memory cells produce antibodies faster and in a greater quantity than after the first exposure to the pathogen - this is called the secondary immune response and it means you remove the pathogen from the body before it causes the symptoms of the disease. 1.​ When pathogens enter our bodies, white blood cells called phagocytes rush to the site of entry, causing inflammation / swelling. 2.​ The phagocytes ingest pathogens and use enzymes to digest them. This is called phagocytosis. 3.​ Some pathogens escape into the body and reproduce very quickly, making you feel ill. Your body recognises the uniquely shaped antigens on the membrane of the pathogen as foreign. 4.​ A second type of white blood cell called a lymphocyte produces a protein called an antibody which has a complementary shape to the pathogen’s antigens. 5.​ The antibodies attach to the pathogen’s antigens, making the pathogens clump together. This makes it easier for phagocytes to engulf and destroy the pathogens. 6.​ Once your body has destroyed all the pathogens, you feel better. Hooray! 7.​ Once you feel better, your body produces some memory cells to ensure that next time you are infected with the same pathogen, you will be able to fight it off before you feel ill - this is immunity! Double hooray!! VACCINATIONS Vaccination is a method of giving someone artificial immunity to a disease without ever having contracted the disease.  Type of vaccine What is in it? Live attenuated vaccine They contain a weakened form of the pathogen. They are modified so that they cannot cause disease, but are still able to activate the immune system. Inactivated vaccine Use the killed version of the pathogen that causes a disease. This weaker version of the pathogen stimulates white blood cells to produce the correct antibodies, but without risk of an infection. The immune response causes the vaccinated person’s white blood cells to produce specific antibodies which fight the infection. If the person then catches the virus, their white blood cells can make these antibodies faster and often stop them becoming severely ill. At this point, a vaccinated person now has increased immunity to infection. ANTIBIOTIC RESISTANCE Alexandra Fleming discovered penicillin in 1929, a fungus-made antibiotic used to treat bacterial infections. Since then, natural and chemical antibiotics have been discovered, but increased use has led to bacterial resistance, making doctors reluctant to prescribe antibiotics, fearing their widespread use. Due to the very quick reproduction of the bacteria there can be an accidental mutation caused from a mistake in the dna has led to the creation of a bacterium which is not affected by the antibiotic All of the normal bacterium has been killed by the antibiotic but the resistant bacterium is not The mutated bacteria which was resistant has multiplied and are now resistant to the antibiotic All of the bacteria is now resistant and so cannot be killed by the antibiotic One way that antibiotics work is by preventing the synthesis of a strong bacterial cell wall. Bacteria live in environments where the water potential in the environment is higher than the water potential of their cytoplasm. Why do some antibiotics cause bacterial cell lysis? The water enters the cell via osmosis because the water is moving from an area of high water potential (outside the bacterium) to an area of a low water potential (inside the bacterium) through a partially permeable membrane. It can enter when in contact with the antibiotic as it breaks down there cell wall meaning water can enter and the cell will burst Some types of antibiotics bind to the bacterial ribosomes. Explain how these antibiotics can kill bacteria. The antibiotic binding to the ribosomes of the bacteria will stop the bacteria proteins producing protein. Ribosomes are the site of protein synthesis, if a bacterium cannot produce protein, it cannot reproduce