Anatomy Ch 3

• structural model of the plasma membrane
• the molecular arrangement of the plasma membrane resembles an ever-moving sea of fluids and a mosaic of many different proteins
• some proteins float freely, some are anchored

• made of
• 1. phospholipids (75%) - amphipathic
• 2. cholesterol - (20%) - slightly amphipathic - stay in the nonpolar tail region
• 3. glycolipids - (5%) - carbohydrate/lipids - ONLY in membrane layer that faces the EXTRACELLULAR liquid - make the two layers asymetric (different)
• 

• parts of plasma membrane that are fully embedded in it - removing them will destroy the membrane
• integral proteins are amphipathic
• peripheral proteins are not firmly embedded - attached to one side or the other - can be removed without hurting the membrane
• 

• span the entire lipid bilayer and protrude into the cytosol and extracellular fluid
• many integral proteins are transmembrane proteins

• proteins with carb groups attached to the end that protrude into the extracellular fluid
• glycocalyx is a glycoprotein "signature" that allows cells to recognize one another - hydrophillic and attracts a thin layer of fluid to the surface of many cells - red blood cells slippery
• 

• Ion channels
• Transporter
• Receptor
• Cell Identity marker
• Linker
• Enzyme

• integral protein
• water filled pores that move specific ions through the plasma membrane
• selective - diff levels of specifity - cation channel - moves all cations through - sodium channel - moves only sodium
• most plasma membranes have specific channels for several common ions
• most numerous ion channels - K⁺ or Cl ^- - fewer for Na⁺ and Ca²⁺

• integral protein
• moves ions and polar substances across the membrane by changing shape
• 

• integral protein - not necessarily transmembrane
• each receptor recognizes and binds a specific ligand that alters cells function in some way
• ligand - a specific molecule that binds to a receptor

• glycoprotein & glycolipids - distinguished your cells from anyone else's
• enable cell to recognize other cells of the same type during tissue formation
• 

• Integral or peripheral
• anchor proteins in the plasma membrane of neighboring proteins to one another - anchors filaments inside and outside the plasma membrane providing structural stability and shape for the cell

• integral or peripheral
• catalyze specific chemical reactions at the inside or outside surface of the cell (depends on which direction active site faces)
• substrate in - product out

• FLUID AND DYNAMIC
• phospholipids and membrane proteins are not rigidly fastened - move around - spaces open and close so water and materials can move through
• proteins are not constant - numbers change - increased or decreased upon needs of the cell

• selective permiable
• 1. non-polar, uncharged particles can cross membrane anywhere (O₂, CO₂, steroids)
• 2. slightly permiable to water and urea(waste product from breakdown of amino acids) travel through small gaps that open and close
• 3. other molecules need help to cross

• difference in concentration of a chemical from one place to another
• Extracellular fluid - higher concentration of O₂ and Na⁺ (sodium ions)
• Intracellular fluid - higher concentrations of CO₂ and K⁺ (potassium ions)

• difference in electrical charges inside and outside the plasma membrane
• at rest:
• + postive = extracellular
• - negative = intracellular
• electrical gradient is the difference in electrical charges of two regions - membrane potential is difference across a membrane

combines influence of concentration and electrical charge gradient on the movement of an ion

diffusion across a membrane - substance moves down its concentration gradient using only kinetic energy - no input of energy from the cell

ATP used to drive substances up the concentration gradient

• 1. Steepness of the concentration gradient (steep moves faster)
• 2. Temperature
• 3. Mass of the diffusing substance (large particles move slow)
• 4. Surface area
• 5. diffusion distance (greater distance takes longer)

• movement of water across a membrane - move from high to low to reach equalibrium
• Tonicity - measure of the solutions ability to change the volume of a cell by altering their water content
• Isotonic - concentration same on both sides - no flow of water
• Hypotonic solututuin - less solute in solution so water moves into cell
• Hypertonic - more solute in solution so water moves into cell

• RBC in a hypertonic solution - water enters cell and causes it to burst
• Crenation - cells in a hypertonic solution - water leaves cell and cell shrivles

plasma membrane proteins that allow water to move through quickly

• pressure exerted by the weight of water - U tube - weight will cause water to move back across membrane - equilibrium is reached when the hydrostatic pressure and the osmosis move at the same rate
• osmotic pressure - the amount of pressure needed to stop osmosis - U tube - amount of pressure needed to force both tubes to have equal water

excess interstitial fluid in the brain - given a hypertonic solution so water leaves interstitial fluid and enters blood where is can be extracted by the kidneys

non-polar, hydrophobic molecules can move through without use of ATP

• Ion-specific channels - may be gated or permanently open
• 

• substances bind to carrier proteins embedded in plasma membrane
• carrier proteins change shape and release them on the other side
• REQUIRES NO ATP
• Transport occurs DOWN a concentration gradient
• TRANSPORT MAXIMUM - the number of transporters in the plasma membrane places an upper limit on the rate that facilitated diffusion can occur - at that point it cant go faster even if solute concentration is increased - the process becomes saturated

• ATP USED
• primary - pumps ions AGAINST concentration gradient
• sodium/potassium pump - Na⁺/ K⁺/ ATPase
• cells expend 40 % of ATP on sodium/ potassium pumps - pumps Na+ out and K+ in against concentration gradient
• Secondary - indirectly uses energy from primary transport - high concentration of Na+ outside so some diffuses back into cell - carries with it other substances against their concentration gradient

• In secondary active transport - if transporters move two substances in the same direction they are symporters
• Antiporters move two substances in opposide directions against their concentration gradient

• Process that brings bulky substances into the cell - uses vessicles
• Receptor-mediated endocytosis - receptors in plasma membrane catch ligands - for vessicle
• Phagocytosis - eating - engulfs particle to break it down - non-specific
• Pinocytosis - drinking - takes droplets of extracellular fluid into cell

• vessicle - small, spherical sac made of plasma membrane
• Exocytosis - process that takes bulky substances out of the cell - secretory cells, nerve cells (neurotransmitters)

• specific cells that are able to carry out phagocytosis
• macrophages - located in body tissues
• neutrophils - type of white blood cell

false feet - projections of the cells plasma membrane and cytoplasm

vessicle move substance into, across, and out of the cell

• cytosol - cytoplasm that surrounds organelles 55% of cell volume
• cytoplasm refers to cytosol and all organelles except nucleus
• mostly water 75 - 90% with ions, nutrients, ATP, and wastes

• network of protein filaments that extent throughout the cytosol
• give support, shapes, and movement to the cell

• 1. Microfilaments - small - around edge of cell - give shape and support
• 2. Intermediate Filaments - thicker than micro - strong - attached to cell membrane and project into cells - help attach cells to one another
• 3. Microtubules - tubes - grow out form centrosome - give cell shape - involved in movement (flagella & celia) - mitotic spindle

fingerlike projections of the plasma membrane - increase surface area of membrane - increases places for transport across the membrane - abundant on cells involved in absorption

• critical for cell division
• composed of two centrioles (tubes 9 triplets) at right angles
• microtubule processing plant

• hair-like projections on cell surface - microtubules
• function to propell fluid over surface of the cell

• microtubules
• single whip-like extenstion
• moves entire cell - only human cell is sperm

• site of protein synthesis
• made of protein and RNA
• can be free or attached

• attached ribosomes - makes plasma membrane for cell
• makes phospholipids and secretes proteins make by attached ribosomes

• 1. synthesizes steroids, fatty acids
• 2. detoxifies drugs in liver cells
• 3. stores calcium in muscle cells

• flattened membrane sacs
• processes & ships proteins make by RER
• cis - in - faces RER
• trans - out - faces plasma membrane

• vesicle forms by golgi complex
• contains digestive enzymes - digest food, worn out organelles, entire cells
• autophagy - lysosome digest a worn out organelle and releases the components into the cytosol to be resued
• autolysis - lysosome destroys entire cell - tissue deterioration just after death

• double membrane
• can self replicate
• more mitochondira in tissue that expends more energy (muscles)
• cristae inner membrane - lots of folds- site of ATP production
• matrix - large inner fluid filled cavity

• most cells have one - some blood cells have none and skeletal muscle cells can have more than one
• Nuclear Envelope - double membrane
• nuclear pores - openings in the nuclear envelope - control movement of substances between the cytoplasm and nucleus
• nucleoli - produce ribosomes - made of protein, DNA, RNA
• chromatin - mass of DNA, protein, and RNA - when cell is in interphase chromatin is a granular mass - during - when getting ready to divide the chromatin coils up into the double helix of DNA

• genes - cell's hereditary units
• chromosomes - genes are arranged along chromosomes (human somatic cells have 46 chromosomes)
• chromatin - inside the nucleus - complex of DNA, proteins, and RNA
• genome - total genetic information carried in a cell

replicated DNA that is still attached at the centromere

• nucleosome - double- stranded DNA (double helix) wrapped twice around a core of histones
• histones - a core of 8 proteins that DNA wraps around
• Linker DNA - holds adjacent nucleosomes together
• chromatin fiber - in cells that arent dividing, histone promotes coiling of nucleosomes into larger fiber