Animal Physiology Lec 1 PDF

Biology Department Third Stage Animal physiology lec.1 Cellular physiology Assistant Lecture Sleman Y Omar [email protected] 2024-2025 Google classroom code: Physiology is the science of life. The branch of biology aims to understand the mechanism...

Biology Department Third Stage Animal physiology lec.1 Cellular physiology Assistant Lecture Sleman Y Omar [email protected] 2024-2025 Google classroom code: Physiology is the science of life. The branch of biology aims to understand the mechanisms of living things, from the basis of cell function at the ionic and molecular level to the integrated behavior of the whole body and the influence of the external environment. Research in physiology helps us to understand how the body works in health and how it responds and adapts to the challenges of everyday life; it also allows us to determine what goes wrong in disease, facilitating the development of new treatments and guidelines for maintaining human and animal health.  Cell Structure and Function Cell Structure and Function There are about 200 different kinds of specialized cells in the human body. When many identical cells are organized together it is called a tissue (such as muscle tissue, nervous tissue, etc). Various tissues organized together for a common purpose are called organs (e.g. the stomach is an organ, and so is the skin, the brain, and the uterus). Specialized Cells of the Human Body Although there are specialized cells - both in structure and function - within the body, all cells have similarities in their structural organization and metabolic needs. Some of the different types of specialized cells within the human body.  Specialized Cells of the Human Body 1-Nerve Cells (Neurons): These are found in the nervous system and function to process and transmit information. They use chemical and electrical synapses to relay signals throughout the body. 2-Epithelial cells: Functions of epithelial cells include secretion, absorption, protection, transcellular transport, sensation detection, and selective permeability. Epithelium lines both the outside (skin) and the inside cavities and lumen of bodies. 3-Exocrine cells: These cells secrete products through ducts, such as mucus, sweat, or digestive enzymes. The products of these cells go directly to the target organ through the ducts.  Specialized Cells of the Human Body 4-Endocrine cells: These cells are similar to exocrine cells, but secrete their products directly into the bloodstream instead of through a duct, are found throughout the body but are concentrated in hormone-secreting glands such as the pituitary. 5-Blood Cells: Red blood cells (erythrocytes). The main function of red blood cells is to collect oxygen in the lungs and deliver it through the blood to the body tissues. White blood cells (leukocytes). They help the body to fight infectious diseases and foreign objects in the immune system.  Cellular Organization 1-Cell Membranes (plasma membrane) 2- Cytoplasm 3- Nucleus 1- Cell Membranes (plasma membrane) Separates internal metabolic events from the external environment and controls the movement of materials into and out of the cell. This membrane is selective permeability. The plasma membrane is a double phospholipid membrane, or a lipid bilayer, with the nonpolar hydrophobic tails pointing toward the inside of the membrane and the polar hydrophilic heads forming the inner and outer surfaces of the membrane. Proteins and cholesterol molecules are scattered throughout the flexible phospholipid membrane. Proteins are either peripheral proteins that attach loosely to the inner or outer surface of the plasma membrane or may be integral proteins that lie across the membrane, extending from inside to outside. Cell Membranes (plasma membrane)  Types of membrane proteins 1--Channel proteins: Proteins that provide passageways through the membranes for certain hydrophilic or water-soluble substances such as polar and charged molecules. No energy is used during transport, hence this type of movement is called facilitated diffusion. 2-Transport proteins: Proteins that spend energy (ATP) to transfer materials across the membrane. The process is called active transport when energy is used to provide a passageway for materials. 3-Recognition proteins: Proteins that distinguish the identity of neighboring cells. These proteins have oligosaccharide or short polysaccharide chains extending out from their cell surface. 4-Adhesion proteins: Proteins that attach cells to neighboring cells or provide anchors for the internal filaments and tubules that give stability to the cell. 5-Receptor proteins: Proteins that initiate specific cell responses once hormones or other trigger molecules bind to them. 6-Electron transfer proteins: Proteins that are involved in moving electrons from one molecule to another during chemical reactions.  Transport across the Cell Membrane 1st: Passive Transport: Mean movement of substances down a concentration gradient and does not require energy use, passive transport include following modes: 1-Bulk flow is the collective movement of substances in the same direction in response to a force, such as pressure. 2-Simple diffusion, or diffusion, is the net movement of substances from an area of higher concentration to an area of lower concentration. 3-Facilitated diffusion is the diffusion of solutes through channel proteins in the plasma membrane without use of energy. 4-Osmosis is the diffusion of water molecules across a selectively permeable membrane. 6-Dialysis: is the diffusion of solutes across a selectively permeable membrane.  Transport across the Cell Membrane 2nd Active Transport across the Cell Membrane Active transport is the movement of solutes against a gradient and requires the expenditure of energy, usually in the form of ATP. Active transport is achieved through one of these two mechanisms: 1-Protein Pumps: Protein pumps in the plasma membrane transfer solutes such as small ions (Na+, K+, Cl-, H+), amino acids, and monosaccharides. The protein binds to a molecule of the substance to be transported on one side of the membrane, then it uses the released energy (ATP) to change its shape and release it on the other side. The protein pumps are specific, there is a different pump for each molecule to be transported. Protein pumps are catalysts in the splitting of ATP to ADP + phosphate, so they are called ATPase enzymes.  2nd Active Transport across the Cell Membrane 2-The sodium-potassium pump (also called the Na+/K+-ATPase enzyme), actively moves sodium to out of the cell and potassium into the cell. These pumps are found in the membrane of virtually every cell and are essential in the transmission of nerve impulses and in muscular contractions. 3rd -Vesicular Transport Is transport as vesicles in the cytoplasm that move macromolecules or large particles across the plasma membrane? Types of vesicular transport include: 1-Exocytosis: This is the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell. 2-Endocytosis: This is the capture of a substance outside the cell when the plasma membrane merges to engulf it.  Kinds of endocytosis: 1 Phagocytosis or cellular eating, in Phagocytosis, the plasma membrane engulfs the solid material, forming a phagocytic vesicle. 2 Pinocytosis or cellular drinking occurs when the plasma membrane folds inward to form a channel allowing dissolved substances to enter the cell. When the channel is closed, the liquid is encircled within a pinocytic vesicle. 3 Receptor-mediated endocytosis: is a form of endocytosis in which receptor proteins on the cell surface are used to capture a specific target molecule. 2-Cytoplasm:- It is a fluid matrix, the cytosol, which consists of 80% to 90% water, salts, organic molecules and many enzymes that catalyze reactions, along with dissolved substances such as proteins and nutrients. 1-Cytoskeleton:- are threadlike proteins inside cells that make the cytoskeleton, its functions? 1- It helps cells to maintain their shape and allows cells and their contents to move. 2-The cytoskeleton allows certain cells such as neutrophils and macrophages to make amoeboid movements. The cytoskeleton: is composed of (A- microtubules and B- microfilaments). A- Microtubules: They are long hollow cylinders, composed of protein subunits, called tubulin. Mts. functions as the framework along which organelles and vesicles move within a cell. They are the thickest of the cytoskeleton structures. B-Microfilaments: Microfilaments provide mechanical support for the cell, determine the cell shape, and in some cases enable cell movements. They have an arrow-like appearance. They are found in almost every cell but are predominant in muscle cells and in the cells that move by changing shape, such as phagocytes. 3-Nucleus Controls the cell activities, and is bounded by the nuclear envelope, a phospholipid bilayer similar to the plasma membrane. The space between these two layers is the nucleolemma cisterna. Chromosomes, Centrioles, Ribosomes, Mitochondria, Endoplasmic Reticulum  Cell Junctions The plasma membranes of adjacent cells are usually separated by extracellular fluids that allow the transport of nutrients and wastes to and from the bloodstream. Three kinds of cell junctions are recognized: 1-Desmosomes: Desmosomes are intercellular junctions that provide strong adhesion between cells. Because they also link intracellular to the intermediate filament cytoskeleton they form the adhesive bonds in a network that gives mechanical strength to tissues. 2-Tight junctions: Tight junction refers to a specialized connection of two adjacent animal cell membranes, Preventing passage of ions and molecules between cells 3-Gap junctions: are protein channels that connect the cytoplasm of 2 cells to allow for molecular passage. Are narrow tunnels between cells that consist of proteins called Connexins? Cell Junctions  Cell Metabolism Cell Metabolism Cell metabolism is the total energy released and consumed by a cell. Metabolism describes all of the chemical reactions that are happening in the body. Catabolism: The energy releasing process in which a chemical or food is used (broken down) by degradation or decomposition, into smaller pieces. Anabolism: Anabolism is just the opposite of catabolism. In this portion of metabolism, the cell consumes energy to produce larger molecules via smaller ones.  Energy Rich Molecules Adenosine Triphosphate (ATP) Is an energy-carrying molecule found in the cells of all living things? ATP captures chemical energy obtained from the breakdown of food molecules and releases it to fuel other cellular processes. The energy used by human cells requires the hydrolysis of 200 to 300 moles of ATP daily. This means that each ATP molecule is recycled 2000 to 3000 times during a single day. ATP cannot be stored, hence its consumption must closely follow its synthesis. Flavin Adenine Dinucleotide (FAD) It is a type of nucleotide distinguished by being comprised of two monomers. Each monomer, in turn, is made up of a nucleobase, a pentose, and a phosphate group. (FAD) is a cofactor for cytochrome-b5 reductase, the enzyme that maintains hemoglobin in its functional reduced state, and glutathione reductase, an enzyme that also protects erythrocytes from oxidative damage. Nicotinamide Adenine Dinucleotide (NADH) Is an important pyridine nucleotide that functions as an oxidative cofactor in eukaryotic cells? NADH plays a key role in the production of energy through redox reactions.  Cellular Respiration Cellular Respiration Cellular respiration is the energy-releasing process by which sugar molecules are broken down by a series of reactions and the chemical energy gets converted to energy stored in ATP molecules. Glycolysis The glycolytic pathway (glycolysis) is where glucose, the smallest molecule that a carbohydrate can be broken into during digestion, gets oxidized and broken into two 3-carbon molecules (pyruvates), which are then fed into the Krebs Cycle. Krebs cycle Two molecules of pyruvate enter the Krebs cycle, which is called the aerobic pathway because it requires the presence of oxygen in order to occur.  Krebs cycle Step 1: The acetic acid subunit of acetyl CoA is combined with oxaloacetate to form a molecule of citrate. Step 2: The citric acid molecule undergoes an isomerization. Step 3: In this step, the isocitrate molecule is oxidized by a NAD molecule. Step 4: In this step, our friend, coenzyme A, returns to oxidize the alpha-ketoglutarate molecule. Step 5: A water molecule sheds its hydrogen atoms to coenzyme A. Step 6: In this step, succinate is oxidized by a molecule of FAD (Flavin adenine dinucleotide). Step 7: An enzyme adds water to the fumarate molecule to form malate. Step 8: In this final step, the malate molecule is oxidized by a NAD molecule.  Isomerization Oxidize with CoA Oxidize Water, Hydrogen, CoA Enzyme add water guanosine diphosphate