Human Anatomy - Cell Structure PDF

HUMAN ANATOMY CYTOLOGY I. INTRODUCTION TO CELLS II. CELL CHEMISTRY III. CELL STRUCTURE I. INTRODUCTION TO CELLS * Anatomy = study of the structure of parts The cell provides basic unit of structural organization Proper functioning of body depends on cells Knowledge o...

HUMAN ANATOMY CYTOLOGY I. INTRODUCTION TO CELLS II. CELL CHEMISTRY III. CELL STRUCTURE I. INTRODUCTION TO CELLS * Anatomy = study of the structure of parts The cell provides basic unit of structural organization Proper functioning of body depends on cells Knowledge of cells needed to understand higher functions Ex. Respiration & protein synthesis & mitosis & meiosis Diseases originate in cells Organizational hierarchy Atoms  molecules  organelles  cells  tissues  organs  organ systems  organism * First observation = Robert Hooke (17th century) Microscopic view of cork  showed network of walls & cavities Named them cells after cubicles in monastery * Cell theory = Schleiden & Schwaan All living things are composed of cells -- the cell is the basic unit of structure for all organisms Axiom = all cells come from cells * All 60-100 trillion cells in human come from cell = fertilized egg Cells vary in shape & size Largest = ovum Others = flat & oval & elongate & stellate & columnar & cuboidal ! Shape often indicates function Ex. RBC has thin walls to transport gases * Cells primary function = metabolism Utilization of nutrients (O2, proteins, lipids, CHO, vitamins, minerals, water) & removal of wastes Maintenance of homeostasis (stable conditions) Generate products (Ex. hormones) II. CELL CHEMISTRY * Water  Most abundant compound in cells – and - in extracellular environment ~ Universal solvent = nearly all chemical compounds dissolve in it Transport media = used to move substances through membranes & cell ! Dehydration = fluid loss exceeds intake  intra- & extracellular fluid levels decrease Source = vomiting & diarrhea & excessive sweating Result = metabolic problems Infants can die within hours (have small fluid volume) * Electrolytes Inorganic compounds (lack carbon) - that form ions in water Ions = atoms or molecules capable of conducting electricity classes = acids & bases & salts All are important for cell function Functions = water movement & pH control & nerve/muscle function & enzyme activity Low levels = muscle cramps & heart attack & brittle bones * Proteins Nitrogen containing organic compounds Organic compounds are defined as having C & H & 0 Amino acid = has amino group (-NH2) and carboxyl group (-C00H) 20+ different amino acids Connect together to form proteins Types Structural = supportive function Ex. collagen in connective tissue Ex. keratin in epidermis Functional = influence metabolism Ex. hormones Ex. enzymes * Carbohydrates 2:1 ratio of H to O Types Monosaccharides = single sugar molecules Disaccharides = 2 sugar molecules connected together Polysaccharides = long-chains of sugar molecules Function = energy source & fuel reserve Too much? Stored as fat or glycogen (storage form of glucose) * Lipids (fats) Lipids = fats & fat related substances (ex. cholesterol)  Structure = primarily long chains of carbon atoms Function = build cell membranes, supply energy, build hormones, & provide insulation Insoluble in water III. CELL STRUCTURE * Structures common to all cells Plasma membrane Outer cell boundary Common name = Plasmalemma (or) plasma membrane Structure = lipid bi-layer Electron microscope view = TRI (3) laminar appearance Called "unit membrane" for years = common structure in nearly all membrane systems Modern view = "fluid mosaic model" = two layers (bi-layer) of lipid molecules Outer layer = hydrophillic area of molecules Water loving Inner layer = hydrophobic area of molecules Water hating Termed “fluid mosaic” because of the large number of proteins Proteins differ in structure & mobility within the membrane Characteristics Selectively permeable barrier = small uncharged molecules & lipid soluble molecules are the only things that pass thru Passage via diffusion = move from high  low concentration Osmosis = tendency of fluid molecules to move across a membrane to equalize the ‘osmotic’ pressure Move from low  high concentration of solutes Instant integrity (sealing) Functions Transport Cell-cell attachment Intra- intercell communication Enzymatic reactions Nutrition Fatty acids – used to build all membranes (eg., plasmalemma, ER, Golgi) Types = ~40 important fatty acids Names based on number of double bonds & where they are positioned  Foundational Omega-3 fatty acids = from cold-water fish, flaxseed oil Omega-6 fatty acids = vegetable oils, nuts Non-foundational Omega-9 fatty acids = olive oil ! Cell metabolism set up to manufacture all needed fatty acids from just a few essential omega-3 and omega- 6 fatty acids Cholesterol Helps determine membrane fluidity Nucleus Largest single membrane bound structure Nuclear envelope = adjacent membranes surrounding nucleus Pores = thru both membranes & connect nucleus to cytosol Selectively permeable Holds DNA & directs cell activities Holds the nucleolus Region that assembles large & small ribosome subunits Holds parts of several different chromosomes Nuclear skeleton = dense mesh of protein filaments Nutrition = Folic Acid (folate) is very important in supporting DNA synthesis & repair Cytoplasm Also called the Cytosol Cell material between nucleus and plasmalemma (mostly fluid) Components Protein synthesis system Protein degradation system Carbohydrate metabolism system Ribosomes = sites of protein synthesis Cytoskeleton Protein scaffold Labile = continuous state of assembly and disassembly Functions = anchoring organelles, anchoring cells together, transporting molecules thru cytosol Nutrition = Water & Amino Acids * Organelles Membrane bound structures within cytoplasm Mitochondria In ALL cells… BUT RBC’s & terminal keratinocytes  Produce energy (ATP molecules) membranes Outer membrane = smooth Lipid synthesis Fatty acid metabolism Inner membrane = folded Cristae = folds of inner membrane. Holds respiratory chain enzymes - manufacture ATP Matrix = material between membranes Hold several enzyme systems - manufacture ATP Nutrition = Carnitine (similar in structure to B vitamins) – helps transport long-chain fatty acids to mitochondria (especially in muscles)- where they are converted to energy (ATP) ! Prevents fatty buildup in heart, liver, skeletal muscles ! Useful in treating CFS (chronic fatigue syndrome) !! All mitochondrion in embryo = maternal origin (from ovum)  replicate themselves during development Problems Heteroplasmy = large numbers of abnormal M inherited Ex. Leber’s hereditary optic neuropathy = rare cause of blindness  extraocular muscle weakness Endoplasmic reticulum Group of tubules Involved in synthesis/transport of proteins Rough ER (rER) “Rough” = ribosomes attached to surface of tubules Manufactures ALL proteins secreted by cell Proteins assembled on ribosomes  moved into tubules for further processing Smooth ER (sER) NO ribosomes on surface of tubules Processes proteins manufactured in rER Lipid synthesis (eg., membrane phospholipids) Detoxifies lipid soluble drugs Membrane bound vesicles holding processing proteins & lipids pinch off  move to Golgi ! Repeated use causes proliferation of sER Explains drug tolerance (alcohol & valium & viagra) Golgi Stack of 3-10 sac-like structures – as a group called cisternae Cis = convex face of stack Function = phosphorylation of proteins  Trans = concave face of stack Function = sorts products (received from ER) into vesicles & adds sugar residues to many Vesicles pinch off surface  move to cell membrane Cilia & Flagella Cytoplasmic projections originating INSIDE cell Cilia = short projections All move in concert = move material to outside of body Flagella = longer Move in whiplike fashion ONLY example in humans = sperm cell = locomotion