Chapter 3 - Summary Human Anatomy & Physiology PDF

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Chapter 3- The Cell (108-156) Introduction to Cells Basic Processes of Cells - Cell Metabolism o Anabolic Reactions- synthesis of polysaccharides, lipids, proteins, and nucleic acids o Catabolic Reactions- break down macromolecules such as carbohydrates and lipids o Oxidation-Reduction Reactions- converts energy of bonds into ATP - Transport of Substances - Communication - Cell reproduction Overview of Cell Structure - Plasma Membrane- structural support, communication with other cells, cell identification - Separates intracellular space/fluid from the extracellular space/fluid Cytoplasm - Cytosol- Intracellular fluid, mostly water o Stores materials and provides a site for critical reactions o Inclusions- store various necessary materials - Organelles- molecular machines that perform specific functions, compartmentalize the cell’s functions - Cytoskeleton- consists of a network of protein filaments o Supports cell, helps create and maintain shape, holds organelles in place - Nucleus o Surrounded by phospholipid bilayer (nuclear envelope), contains DNA and RNA Cell Size and Diversity - Composition of cell differs based on function (red blood cells vs. nerve cells vs. skeletal cells) Structure of the Plasma Membrane The Phospholipid Bilayer - To make an effective bilayer: o Molecules must have hydrophilic parts o Molecules must also have hydrophobic parts (phospholipids are both hydrophilic and hydrophobic)

- Bilayer- two layers of phospholipid with tails together and heads together Fluid Mosaic Model of the Plasma Membrane - Fluid mosaic model- plasma membrane contains a multitude of molecules (phospholipid, proteins, lipids, carbohydrates) - Membrane Proteins o Positioned so hydrophobic amino acids are in fatty acid tail of phospholipid bilayer, and their hydrophilic amino acids are facing the cytosol o Two main types- integral proteins span the whole membrane (can be transmembrane proteins); peripheral proteins are on only one side of the membrane or the other o Functions  Transporting substances (protein channels, carrier proteins)  Acting as receptors (binds to a ligand, aka a chemical messenger)  Acting as enzymes  Providing structural support  Linking adjacent cells - Other Membrane Components o Cholesterol- stabilizes structure of plasma membrane o Glycolipids o Glycoproteins- both consist of carbohydrate chains covalently attached to either membrane lipids or proteins, function in cell recognition Transport Across the Plasma Membrane - Selectively permeable - ECF (extracellular fluid) contains nutrients, water, ions, oxygen, vitamins, and other macromolecules - Passive Transport and Active Transport - Passive Transport: diffusion and osmosis o Basic driving force is concentration gradient (a form of potential energy) o Diffusion  Movement of solute molecules from an area of higher solute concentration to an area of lower solute concentration until equilibrium is reached  Smaller particles, gases, higher temperatures, greater concentration increase the rate of diffusion (increases particle’s kinetic energy)  Simple Diffusion- nonpolar solutes that pass straight through lipid bilayer without assistance from membrane proteins

Facilitated Diffusion- charged or polar solutes that cross the phospholipid bilayer with the help of a membrane protein. These need channels and carriers for their transport into and out of the cell o Osmosis  Movement of solvent across a membrane from a lower concentration to a higher concentration (aka THE WATER MOVES, not the solute -> change in volume)  Water can move through aquaporins in the plasma membrane  Driven by osmotic pressure o Tonicity  Comparison of osmotic pressure gradients between two solutionsisotonic is normal  Hypertonic- causes cell to lose water (concentration of solute in cell is less than outside)  Hypotonic- causes cell to gain water (solute in cell is greater than ECF) Active Transport o Primary Active Transport- protein pumps solute against concentration gradient, as well as catalyze the reaction that breaks down ATP (phosphate removed from turning ATP into ADP changes shape of pump, causing transport in or out of cell)  Three types of pumps: Uniport pump (drives a single substance in or out of cell), symport pump (drives 2+ substances in same direction across membrane), and antiport pump (drives 2+ substances in opposite directions  Main pump is sodium-potassium pump (3 sodium ions out of cell for every two potassium ion into cell) o Secondary Active Transport  Uses ATP to create concentration gradient by pumping one substance across plasma membrane, then uses that concentration gradient to passively pump another substance along with it  Moves the third sodium ion back into cell along with glucose, essential for absorption and secretion in intestines and kidneys 

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Consequences of Ion Transport across Plasma Membrane: Electrophysiology - Electrical Potential- separation of charges (e.g. cytosol and ECF)- creates electrical gradient

o Electrophysiology- study of membrane potential (electrical potential across membranes) o Resting membrane potential- when cell is not stimulated Active Transport via Vesicles - Vesicles- transport large particles in or out of cell- vesicular transport requires energy from ATP o Endocytosis and exocytosis - Endocytosis- large particles are taken into cell o Phagocytosis- reaches out to take in item o Pinocytosis- shrugs inward to take in item o Receptor-mediated endocytosis - Exocytosis- molecules released out of cell - Transcytosis- endocytosis, travel across cell, then immediate exocytosis Cytoplasmic Organelles - Mitochondria o Contains its own dna and enzymes for protein synthesis, as well as ribosomes o Cristae- folds in inner mitochondrial membrane o Intermembrane space, and matrix (inside main part of mitochondria) o Oxidative catabolism makes ATP - Peroxisomes- oxidizes hydrogen to make H2O2 o H2O2 oxidizes toxic substances, breaks down fatty acids, and synthesizes phospholipids - Ribosomes o Synthesize proteins o Free ribosomes are in cytosol, and bound ribosomes are in membranes of other organelles The Endomembrane System - Endoplasmic Reticulum o Continuous of the nuclear envelope o Membrane = ER Lumen o Rough ER  Forms proteins and folds them  Secretory protein leaves RER in a transport vesicle  Membrane factory o Smooth ER  Calcium ion storage  Detoxification reactions  Lipid synthesis - Golgi Apparatus o Proteins and lipids are modified, sorted, and packaged for export - Lysosomes o Contain enzymes- acid hydrolases which catalyze hydrolysis reactions

o Degrades units into subunits then releases into cytosol for disposal The Cytoskeleton -...