Biology (F/R-009) Course Notes PDF

Types of cells and some cellular organelles of eukaryotes Prof. Hossam El-Din M. Omar Learning Objectives By the end of the course, you will be able to: ✓ Distinguish between the prokarocyte and eupkarocyte. ✓ List the structure and function of the cellular organelles. ✓ Explain the how t...

Types of cells and some cellular organelles of eukaryotes Prof. Hossam El-Din M. Omar Learning Objectives By the end of the course, you will be able to: ✓ Distinguish between the prokarocyte and eupkarocyte. ✓ List the structure and function of the cellular organelles. ✓ Explain the how the mitochondria play an important role in metabolism. ✓ Describe the different functions of cell membranes. ✓ Studying the types and examples for animal cells in different tissues. ✓ Explain the role of nucleic acid in genetics and cellular communication.  Characteristics of Life 1. Composed of Cells 2. Reproduction 3. Growth & Development 4. Obtain & Use Energy…METABOLISM 5. Respond to environment 6. Homeostasis 7. DNA is the ‘Universal Genetic Code 8. Evolution and Adaptation Levels of Organization…Continued Organs Organ Systems Organism Levels of Organization  A cell is the basic unit of life…All cells come from preexisting cells  Unicellular Multicellular  Organisms composed Organisms composed of many cells…diversity and of a single cell specialization of function (over 85 types of cells in the human body) Complex Tissue Structure: As multicellular organisms, most animals develop specialized cells that group together into tissues with specialized functions. A tissue is a collection of similar cells that had a common embryonic origin. There are four main types of animal tissues: nervous, muscle, connective, and epithelial. Nervous tissue contains neurons, or nerve cells, which transmit nerve impulses. Muscle tissue contracts to cause all types of body movement. Animals also have specialized connective tissues that provide many functions, including transport (Blood) and structural support (bone).  Reproduction Asexual Reproduction:  Sexual Reproduction: – Single parent copies its  Two different parent DNA and then divides cells unite to produce or ‘buds’ to produce the first cells of a new GENETICALLY organism. IDENTICAL OFFSPRING.  Offspring are – This can mean ‘rapid- GENETICALLY UNIQUE fire’ reproduction of leading to greater great numbers of genetic diversity and identical organisms speciation on Earth.  All organisms grow and develop  Multicellular organisms Single celled  undergo extensive organisms (like development from a single bacteria) growth fertilized egg dividing many, is mostly a many times to produce the simple increase multitude of cells in mature in size organisms  Differentiation is the changing of shape and structure to perform different functions.  Obtain and Use Energy All living things obtain energy from their environment or surroundings and use it for growth, development, reproduction, and excretion – these processes occur at different rates… METABOLISM = Anabolism (synthesizing compounds – expends energy) + Catabolism (breaking compounds into simple components – releases energy) = Combination of chemical reactions (total activity) that build and break down materials as organisms carry out their life processes.  Living organisms respond to the environment  Organisms detect and respond to a STIMULUS (signal) or anything in the environment that causes a response whether internal or external. Internal stimuli are External stimuli include things like blood light, touch, sound, glucose level (low heat, smell, sight… levels make you feel hungry, possibly weak, tired, head-achy, etc)  Homeostasis The autonomic (self-controlled) processes by which organisms respond to stimuli such that conditions in the body are kept suitable to sustain life for example respond of body to bleeding and heat stress ▪ All life is based on a UNIVERSAL GENETIC CODE…DNA, determining the inherited traits of all organisms! DNA is a type of biomolecule known as a Nucleic Acid that had a three dimensional shape called a double helix. The shape of DNA allows for duplication and ‘reading’ or expressions of the genes it encodes.  EVOLUTION is ability of a group of organisms to change over time. This invaluable for survival in constantly changing environments… ADAPTATION is a trait of a living thing that helps it compete and survive to reproduce in its environment.  The Cell The cell is the lowest level of organization that can perform all activities required for life. All cells are enclosed by a membrane and use DNA as their genetic information. A eukaryotic cell has membrane-enclosed organelles, the largest of which is usually the nucleus By comparison, a prokaryotic cell is simpler and usually smaller, and does not contain a nucleus or other membrane-enclosed organelles  The Cell Theory 1. Cells” were named by Englishman Robert Hooke in 1665. 2. The cell is the basic unit of structure and function. 3. All organisms are made of one or more cells. 4. All cells come from pre-existing cells.  Types of Cells Prokaryotic Cells Eukaryotic Cells The first and most primitive Most organisms have cells eukaryotic cells (ex: all plant Lack a nucleus and other and animal cells!) membrane bound organelles All genetic material is (mitochondria, etc) contained in a nucleus Bacteria are the ONLY Have many membrane prokaryotes bound organelles Functions of the Plasma Membrane 1- Physical Barrier Protects all the components of the cell from the outside environment and allows separate activities to occur inside and outside the cell. The plasma membrane provides structural support to the cell. 2- Selective Permeability Plasma membranes are selectively permeable, meaning that only certain molecules can pass through them. 3- Endocytosis and Exocytosis Endocytosis is ingestion of relatively larger molecules that pass through channels. Exocytosis is when the cell releases these materials. 4- Cell Signaling Facilitate communication and signaling between cells. Proteins on the cell “mark” that cell so that other cells can identify it. The membrane also has receptors that allow it to carry out certain tasks when molecules such as hormones bind to those receptors. Passive transport across cell membranes 1. Diffusion: Molecules and ions move freely in gases and liquids, each type of these particles tends to spread out evenly within the space available. Diffusion is the net movement of molecules from a region of its higher concentration to a region of its lower concentration with no energy is used. Facilitated diffusion: is the movement of specific molecules down a concentration gradient with the aid of special channel or carrier protein and no energy is used. Ions or electrically charged molecules are not able to diffuse through the phospholipid bilayer because they are repelled from the hydrophobic tails. Large molecules are also unable to move through the phospholipid bilayer freely. However, the cell membrane contains special channel protein that provide hydrophilic passageways for these special ions and molecules. Diffusion through these channel proteins is called facilitated diffusion. Phagocytosis = “cellular eating” via lysosome Pinocytosis = “cellular drinking” Receptor-mediated endocytosis → triggered by ligand signal  Exocytosis Using a secretory vesicle to remove food, wastes from cell  Construction of Cell Membranes Membrane proteins provide a variety of cell functions  Passive Transport - Osmosis Direction of osmosis is determined by comparing total solute concentrations – Hypertonic = more solute, less water – Hypotonic = less solute, more water – Isotonic = equal solute, equal water Erythrocyte equilibrium No osmotic pressure - cell is in an isotonic solution - Water does not cross membrane Increased [Osmotic] in cytoplasm - cell is in an hypotonic solution - Water enters cell, swelling Decreased [Osmotic] in cytoplasm - cell is in an hypotonic solution - Water leaves cell, shrinking  Cell Lysis Using hypotonic solution Or interfering with Na+ equilibrium causes cells to burst This can be used to researchers’ advantage when isolating cells What are Mitochondria? Popularly known as the “Powerhouse of the cell,” mitochondria (singular: mitochondrion) are a double membrane-bound organelle found in most eukaryotic organisms. They are found inside the cytoplasm. They play a major role in breaking down nutrients and generating energy-rich molecules for the cell. Many of the biochemical reactions involved in cellular respiration take place within the mitochondria. Structure of Mitochondria: The mitochondrion is a double-membraned, rod- shaped structure. Its size ranges from 0.5 to 1.0 micrometre in diameter. The structure comprises an outer membrane, an inner membrane, and a gel- like material called the matrix. The outer membrane and the inner membrane are made of proteins and phospholipid layers separated by the intermembrane space. The outer membrane covers the surface of the mitochondrion and has a large number of special proteins known as porins. Cristae: The inner membrane of mitochondria is rather complex in structure. It has many folds that form a layered structure called cristae, and this helps in increasing the surface area inside the organelle. The cristae and the proteins of the inner membrane aid in the production of ATP molecules. The inner mitochondrial membrane is strictly permeable only to oxygen and ATP molecules. A number of chemical reactions take place within the inner membrane of mitochondria. Mitochondrial Matrix: is a viscous fluid that contains a mixture of enzymes and proteins. It also comprises ribosomes, inorganic ions, mitochondrial DNA, nucleotide cofactors, and organic molecules. The enzymes present in the matrix play an important role in the synthesis of ATP molecules. Functions of Mitochondria 1-The most important function of mitochondria is to produce energy through the process of oxidative phosphorylation. 2- Regulates the metabolic activity of the cell 3- Promotes the growth of new cells and cell multiplication 4- Helps in detoxifying ammonia in the liver cells 5- Plays an important role in apoptosis or programmed cell death 6- Helps in maintaining an adequate concentration of calcium ions within the compartments of the cell 7- It is also involved in various cellular activities like cellular differentiation and cell signalling 8- Controlling the cell cycle and in cell growth. Mitochondrial DNA ❖ Although most of our DNA is kept in the nucleus of each cell, mitochondria have their own set of DNA. Interestingly, mitochondrial DNA (mtDNA) is more similar to bacterial DNA. ❖ The mtDNA holds the instructions for a number of proteinsTrusted Source and other cellular support equipment across 37 genes. ❖ The human genome stored in the nuclei of our cells contains around 3.3 billion base pairs, whereas mtDNA consists of less than 17,000Trusted Source. ❖ During reproduction, half of a child’s DNA comes from their father and half from their mother. However, the child always receives their mtDNA from their mother. Because of this, mtDNA has proven very useful for tracing genetic lines Producing energy ATP, is often referred to as the molecular unit of currency because it powers metabolic processes. Most ATP is produced in mitochondria through a series of reactions, known as the citric acid cycle or the Krebs cycle. Energy production mostly takes place on the folds or cristae of the inner membrane. Mitochondria convert chemical energy from the food we eat into an energy form that the cell can use (oxidative phosphorylation). The Krebs cycle produces a chemical called NADH. NADH is used by enzymes embedded in the cristae to produce ATP. Cell death ▪ Cell death (apoptosis) is an essential part of life. As cells become old or broken, they are cleared away and destroyed. Mitochondria help decide which cells are destroyed. ▪ Mitochondria release cytochrome C, which activates caspase, one of the chief enzymes involved in destroying cells during apoptosis. Because certain diseases, such as cancer, involve a breakdown in normal apoptosis, mitochondria are thought to play a role in the disease. Storing calcium ▪ Because calcium is critical, the cell regulates it tightly. Mitochondria play a part in this by quickly absorbing calcium ions and holding them until they are needed. ▪ Calcium is vital for the release of a neurotransmitter from a nerve cell or hormones from endocrine cells, muscle function, and blood clotting. Symptoms of mitochondrial diseases can include: ▪ Poor growth. ▪ Muscle weakness, muscle pain, low muscle tone, exercise intolerance. ▪ Vision and/or hearing problems. ▪ Learning disabilities, delays in development. ▪ Heart, liver or kidney diseases. ▪ swallowing difficulties, diarrhea or constipation, unexplained vomiting. ▪ Increased risk of infection. ▪ Neurological problems. ▪ Movement disorders. ▪ Thyroid problems. ▪ Respiratory (breathing) problems. Thanks