Ch 2 Molecules and cells - Animal Physiology .txt

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Ch 2 Molecules and cells - Animal Physiology .txt
2014-03-01 16:31:25
animal phys cell molecules

animal phys cell and molecules
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  1. ch 2
  2. Ampipathic
    • molecule consisting of a POLAR and NON-POLAR part
    • ie: phospholipids have a POLAR head and 2 NON-polar tails
  3. fluidity
    the ease of motion of phospholipid molecules in a membrane leaflet (inner membrane non-polar tails)
  4. What determines fluidity
    • degree of Saturation: greater UNSATURATION = more fluid (less tightly bound)
    • temperature: colder then phospholipids become more STIFF (less fluid)
    • if fish have to adapt to cold climate, they are more likely to have more unsaturated (double cc) bonds to protect against the coldness…less likely to become more stiff since they're already unsat
  5. 5 types of membrane proteins and fxnal roles (CH SUMMARY#9)
    • 1. Channels: permits simple diffusion of solutes or h20 thru a membrane
    • 2. Transporter: BINDS non-covalently with molecules to move them thru membrane (if energy used active transport, otherwise fac. diffus.)
    • 3. Enzyme: CATALYZES a chemical reaction in which bonds are made or broken
    • 4. Receptor: BINDS with specific molecules to initiate Change in Membrane PERMEABILITY or metabolism (mediates responses of cell to chemical messages coming from outside cell)
    • 5. Structural protein: Attaches to other structures to ANCHOR INTRACELLULAR elements to cell membrane, or create JUNCTIONS btw cells
  6. Carbohyrates role in membranes
    • They can COVALENTLY bond with lipids and or proteins
    • ie: Glycolipids, proteoglycans and glycoproteins
    • Carb groups are POLAR and therefore are branch outwards from membrane surface in order to ATTACH to proteins or for recog sites
  7. Single epithelium
    single LAYER of epithelial cells, each with TIGHT junctions sealing space b/w cells
  8. APICAL surface:
    • faces outwards, sometimes containing MICROVILLI (collectively BRUSH border)
    • Consists of 3 types: squamous, columnar and cuboidal
  9. BASAL surface and membrane:
    • faces towards attached underlying tissue, contains BASOlateral region b/w two epithelial cells
    • BASEMENT membrane: area where it rests on (glycoproteins and collagen)
    • Occluding junctions: TIGHT or septate junctions that block space b/w ep cells
    • DESMOSOMES: glycoprotein filaments adhering b/w ep cells, STRENGTHEN and stabilize contacts b/w cells
    • GAP JXN:
    • Have CONNEXIN proteins that act to allow SMALL MOLECULES to PASS thru
  11. Epithelial cell transport paths
    • TRANScellular: nutrients, ions etc pass THROUGH cells (2 cell membranes)
    • PARAcellular: pass b/w ep cells…if tight jxns then prevent this movement, unless LEAKY
  12. Metabolic pathways
    • Enzyme catalyzed reactions determined by
    • 1. Types and amts of enzymes present, some pathways only fxn if ALL enzymes present
    • 2. Catalytic activity of enzyme can be modulated to control pathway: if CONSTITUTIVE then enzyme present highly and regardless of conditions, but INDUCIBLE only at high levels if inducing agents increase enzyme levels
  13. Cytochrome P450 enzymes
    • Activity: INducible enzyme
    • Role: DETOXIFY foreign compounds
    • Inducing agents: the Foreign compounds
  14. HAH in relation to P450
    • HAH are hydrocarbon pollutants and once they are released, they activate INTRACELLULAR receptors, which act as TRANSCRIPTION FACTORS for P450 genes, causing P450 levels to RISE!
    • This aids in better detoxification with second exposure to HAHs
  15. Fast Regulation with enzymes
    • Rate limiting rxns: there's a rate limiting step that determines the rate of rxn
    • Branch pt rxns: one reactant produces more than 1 products for multiple pathways
  16. Allosteric modulation
    NON-Covalent Binding of a modulator to an enzyme to UPREGULATE or DOWNREGULATE catalytic activity
  17. Covalent modulation
    • Make or Break covalent bonds b/w modulators and enzymes
    • Ie: De/Phosphorylation
    • Phosphorylation CATALYZED by Protein Kinases: Bond to phosphate using ATP
  18. Amplification
    • Involves multiple protein kinases
    • Each molecule of protein kinase can catalyze activation of many molecules of the enzyme following it…so multiple protein kinases have an amplification effect
  19. Four types of receptors
    • 1. Ligand-gated channels
    • 2. G-protein coupled receptors (GPCRs)
    • 3. Enzyme/enzyme-linked channels
    • 4. Intracellular receptors
  20. Ligand gated channels
    • Acts as RECEPTOR and Channel
    • Fxn in transmission of NERVE impulses across synapses
    • ie: ACh released to bind to ACh receptors on muscle cell surface (ligand-gated) allowing Na and K to flow
  21. Toxin affecting ligand gated channel (Ch 2 SUMMARY #11)
    • Alpha-conotoxin: BInds to RECEPTOR sites on muscle cell ACh receptors
    • Used by cone snails and some snakes as it is a FAST mechanism to paralyze prey to kill
  22. GPCRs
    • Mediate response to HORMONES and Neurotransmitters by acting via MESSENGERS (NOT allowing chemicals or ions to pass thru)
    • Activates a G protein, which can activate intracellular fxns or further act with membrane protein enzymes
    • ie: Epinephrine acts on GPCR which leads to activation of G proteins (can activate many). These then exchanGDP for GTP, and bind to adenylyl cyclase, catalyzing synth of cAMP from ATP and this activates protein kinases (amplified response) which phosphorylate proteins…all in response epinephrine signal
  23. Enzyme/Enzyme linked receptors
    • these receptors activate formation of 2nd messengers
    • ie: receptor protein which is an ENZYME, catalyzes formation of cGMP when hormone (atrial natriuretic peptide ANP) binds to receptor of the membrane enzyme. cGMP is generated similarly to cAMP
  24. G protein systems rely on membrane fluidity (Ch2 SUMMARY #5)
    Fluidity will aid in the ability for G proteins, once activated by GPCRs, to move along the membrane in order to bind with adenlyl cyclase, aiding in a faster response if more fluidity exists (more fluid if UNsaturated non-polar tails…MORE double carbon bonds to DISRUPT tight packaging)
  25. Fxn of second messengers
    Aid in amplification of the enzyme effects
  26. Intracellular receptors
    • Activated by binding with LIGANDS
    • Interact with DNA, causing activation of primary response genes, which then can activate other genes
    • ie: steroid & thryroid hormones, retinoic acid, vitamin D and NO
    • Steroid hormones can act as transcription factors with the receptor to aid in transcription