VPHY101 Topic 5.a - Cellular Physiology SY 22-23 PDF

(VPhy 101) VETERINARY GENERAL Topic 5: PHYSIOLOGY üCellular Physiology Shiela N. Romero-Rabe Doctor of Veterinary Medicine (VSU) Master of Science...

(VPhy 101) VETERINARY GENERAL Topic 5: PHYSIOLOGY üCellular Physiology Shiela N. Romero-Rabe Doctor of Veterinary Medicine (VSU) Master of Science in Veterinary Medicine candidate (UPLB) Learning Outcomes: üDescribe the organization of the cell üName the chemical substances of the protoplasm of the cell and describe the function/s of each üGive the form and function of cell organelles Learning Outcomes: üDescribe and appreciate functional systems of the cell that contribute to cell life including: endocytosis, pinocytosis and phagocytosis; synthetic functions; extraction of energy from nutrients; and cellular movements. Learning Outcomes: üUnderstand genetic control of protein synthesis in the cell  Cellular PHYSIOLOGY: Cells are distinct from inanimate constituents: 1)Ability to Grow 2)Replicate 3)Perform Complex Metabolic Reaction 4) Respond to environmental stimuli  Cellular PHYSIOLOGY: Cells have: 1) Ability to grow  Cellular PHYSIOLOGY: Cells can: 2) Replicate Cellular PHYSIOLOGY: Cells can: 3) Perform complex metabolic reaction Cellular PHYSIOLOGY: Cells can: 4) Respond to environmental stimuli Cellular PHYSIOLOGY: Figure 1. A diagram of all cell structures visible in an electron microscope. © Cengage Learning, 2013 Cellular PHYSIOLOGY: All cells has two major subdivisions: Plasma membrane Cytoplasm Eukaryotic cells: Nucleus: houses the DNA Cellular PHYSIOLOGY: Plasma membrane Cellular PHYSIOLOGY: Plasma membrane Intracellular Fluid (ICF) -very thin oily barrier that encloses the Extracellular Fluid (ECF) cell, separating the cell content from the surrounding environment -do not serve only as a mechanical barrier to hold in contents of the cell but selectively control movement of many molecules Cellular PHYSIOLOGY: Plasma membrane Hydrophilic Hydrophobic -composed of phospholipids, cholesterol, proteins and glycoproteins - water, CO2 and small hydrophobic molecules can easily diffuse Cellular PHYSIOLOGY: Plasma membrane Hydrophilic Hydrophobic Cellular PHYSIOLOGY: Cytoplasm Cellular PHYSIOLOGY: Cytoplasm -portion of the cell interior not occupied by the nucleus - contains number of discrete, specialized organelles and cytoskeletons dispersed within the cytosol Cellular PHYSIOLOGY: Cytoplasm cytosol Cellular PHYSIOLOGY: Cytoplasm and its Organelles Cellular PHYSIOLOGY: Cytoplasm and its Organelles Cellular PHYSIOLOGY: Cytoplasm and its Organelles Cellular PHYSIOLOGY: Nucleus Cellular PHYSIOLOGY: Nucleus – Largest single organized cell component usually located near the center of the cell Cellular PHYSIOLOGY: Nucleus – Surrounded by a double –layered membrane with many pores Cellular PHYSIOLOGY: Nucleus Ø contains the materials for genetic instructions and inheritance ØIn-houses the DNA - packaged with proteins called histones in the nucleus to form complexes called chromosomes Cellular PHYSIOLOGY: Nucleus ØDNA- has two important functions: 1)providing a code of information for RNA and protein synthesis and; 2) serving as a genetic blueprint during cell replication (for genetic inheritance) Cellular PHYSIOLOGY: Nucleus Øthe nucleus indirectly governs most cell activities Øserves as the cell’s control center Cellular PHYSIOLOGY: Nucleus 1. Transcription - Gene in a DNA - RNA polymerase - Pre-mRNA - Mature-mRNA 2. Translation -rRNA -ribosome - tRNA Cellular PHYSIOLOGY: – All cells in the body has same set of genetic material – Different cell types transcribe different sets of genes Cellular PHYSIOLOGY: How is this differential gene expression accomplished? Epigenetics: switching genes on and off 1. Regulation of individual genes with promoters and transcription factors 2. Regulation of transcription factors in different tissues and at different stages. Cellular PHYSIOLOGY: Ribosomes Ø ribosomal RNA–protein complexes that synthesize proteins, indirectly under the direction of nuclear DNA Cellular PHYSIOLOGY: Ribosomes Ø Has two locations: 1)Unattached or “free” ribosomes are dispersed throughout the cytosol 2)Bound ribosomes are found on membranes of a major organelle, the endoplasmic reticulum (ER) Cellular PHYSIOLOGY: Endoplasmic Reticulum Ø an elaborate, fluid filled membranous system distributed extensively throughout the cytosol, where it is primarily a protein- manufacturing factory. Ø Two distinct types of ER— rough and smooth—can be distinguished. Cellular PHYSIOLOGY: Endoplasmic Reticulum Cellular PHYSIOLOGY: Endoplasmic Reticulum Cellular PHYSIOLOGY: Endoplasmic Reticulum Øthe ER is thought to be one continuous organelle with many interconnected channels. The relative amount of smooth and rough ER varies between cells, depending on the activity of the cell. Cellular PHYSIOLOGY: Endoplasmic Reticulum ØSpecialized ER’s Liver-SER -contains enzymes specialized for detoxifying toxic compounds produced within the body by the metabolism of substances that enter from the outside (such as drugs and plant toxins) Muscle-Sarcoplasmic reticulum Cellular PHYSIOLOGY: Golgi Complex Øconsists of sets of flattened, slightly curved, membrane-enclosed sacs, or cisternae, stacked in layers which closely associated with ER. Cellular PHYSIOLOGY: Golgi Complex ØTwo major functions: 1)Processing the raw materials into finished products. 2)Sorting and directing the finished products to their final destinations. Exocytosis Cellular PHYSIOLOGY: Lysosomes and Proteasomes ØFunctions: important for breaking down unwanted materials Enzyme types: – Glycosidases – Proteases – Sulfatases Cellular PHYSIOLOGY: Lysosomes: Functions Øare small organelles that break down organic molecules (lys means “breakdown”; some means “body”) Ølysosomes vary in size and shape, depending on the contents they are digesting Cellular PHYSIOLOGY: Lysosomes: Functions Ø Most commonly, lysosomes are small (0.2 to 0.5 mm in diameter) oval or spherical membrane-bound bodies. ØOn average, a cell contains about 300 lysosomes Cellular PHYSIOLOGY: Lysosomes: Functions Ø Each lysosome contains more than 30 different hydrolases synthesized in the ER Golgi complex for packaging into the budding lysosome. ØLysosomal enzymes are similar to the hydrolytic enzymes that the digestive system secretes to digest food. Thus, lysosomes serve as the intracellular “digestive system.” Cellular PHYSIOLOGY: Lysosomes: Functions ØLysosomes digest extracellular material brought into the cell by phagocytosis Endocytosis - the internalization of extracellular material within a cell (endo means “within”). - can be accomplished in three ways—pinocytosis, receptor mediated endocytosis, and phagocytosis— depending on the contents of the internalized material and the cell type Endocytosis - Most body cells perform pinocytosis, many carry out receptor-mediated endocytosis, but only a few specialized cells are capable of phagocytosis. - cell drinking - A droplet of extracellular fluid are taken up non-selectively - Dynamin facilitates the pinching off of endocytic vesicle/s - a highly selective process that enables cells to import specific large molecules that the cell needs from its environment - triggered by the binding of a molecule such as a protein to a specific surface membrane receptor site - Clathrin facilitates pouch forming (coated pit) - Cholesterol complexes, vitamin B12, the hormone insulin, and iron are examples of substances selectively taken into cells by receptor- mediated endocytosis - Unfortunately, some viruses can sneak into cells by exploiting this mechanism. For instance, flu viruses and HIV/ FIV (helper T cells), the viruses that cause human and feline AIDS respectively, gain entry to cells via receptor-mediated endocytosis. They do so by binding with membrane receptor sites normally designed to trigger internalization of a needed molecule. - During phagocytosis (“cell eating”), large multimolecular particles are internalized - only a few specialized cells are capable of phagocytosis known as “professional” phagocytes, the most notable being the immune cells that are crucial defense mechanisms in all animals (neutrophils and monocytes/macrophages) - Pseudopods are used to engulf worn out materials/foreign invaders - lysosome fuses with the membrane of the internalized vesicle and releases its hydrolytic enzymes into the vesicle, where they attack the trapped material without damaging the rest of the cell Cellular PHYSIOLOGY: Lysosomes: Functions ØLysosomes remove worn out organelles - can also fuse with aged or damaged organelles to remove parts of the cell. This selective self-digestion makes way for new replacement parts. Cellular PHYSIOLOGY: Lysosomes: Functions ØCan rupture to kill a whole cell when that cell is severely damaged ØCauses intentional self destruction of healthy cells. This happens as a normal part of embryonic development when certain unwanted tissues that form are programmed for destruction. Cellular PHYSIOLOGY: Proteasomes Øa large tunnel-like structure made of numerous proteins ØProteasomes destroy internal proteins ØCells has thousands of it Cellular PHYSIOLOGY: Proteasomes ØSpecialized enzymes can detect worn out/to be destroyed proteins and “tag” them with a tiny protein called ubiquitin. Øubiquitin-tagged protein is then recognized by the proteasome and drawn in to its disassembly tunnel Cellular PHYSIOLOGY: Peroxisomes Øseveral hundred small peroxisomes that are about one third to one half the average size of lysosomes are present in a cell Øhouse several powerful oxidative enzymes and contain most of the cell’s catalase Cellular PHYSIOLOGY: Peroxisomes ØOxidative enzymes, as the name implies, use oxygen (O2), to strip hydrogen from certain organic molecules. This reaction helps detoxify various wastes produced within the cell or foreign toxic compounds that have entered the cell, such as ethanol that is consumed in alcoholic beverages. Cellular PHYSIOLOGY: Peroxisomes ØHydrogen peroxide (H2O2), is formed by molecular oxygen and the hydrogen atoms stripped from the toxic molecule. ØHydrogen peroxide is potentially destructive if allowed to accumulate or escape from the confines of the peroxisome. Cellular PHYSIOLOGY: Peroxisomes ØHowever, peroxisomes also contain an abundance of catalase, an enzyme that decomposes potent H2O2 into harmless H2O and O2. ØThis latter reaction is an important safety mechanism that destroys the potentially deadly peroxide at the site of its production, thereby preventing its possible devastating escape into the cytosol.