ANAT 7390 Lecture Notes - Lecture 1: Tight Junction, Adipose Tissue, Cholinesterase
17 Jun 2018
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TOPIC II: CELL PHYSIOLOGY I
A) The Cell Membrane
1) Phospholipid Bilayer
- continuous layer around cell
- barrier to water soluble substances – NOT to small molecules and/or
lipid soluble molecules (e.g. O2 & CO2)
2) Membrane Proteins
a) transport proteins
i) channels
- form pore in membrane
- selectively permit channel-mediated facilitated diffusion of
specific ions
- can be:
① gated: can open or close – in response to stimuli
② non-gated (= leakage channels): always open
ii) carrier proteins
- bind solute + carry it across membrane
- allow protein carrier-mediated facilitated transport OR active
transport
- e.g. glucose transporters
b) receptor proteins
- can bind specific extracellular molecules (= ligands) e.g. hormones,
neurotransmitters (nt)
- e.g. glucose uptake:
i) insulin binds to receptor on skel. muscle or adipose tissue
ii) triggers movement of more glucose transporters to cell
membrane
iii) ↑ glucose movement from blood into cells
c) enzymes
- control chemical reactions on outer or inner surface
- e.g. 1: acetylcholinesterase
- e.g. 2: Na+/K+- ATPase - all cells have this
d) joining proteins
- anchor cell membrane to cytoskeleton or an adjacent cell
i) junctional proteins between cells forming:
- desmosomes, tight junctions, gap junctions
2
ii) extracellular fibres (usually glycoproteins)
e) identifying proteins
- e.g. Major Histocompatibility Complex (MHC) proteins
- on surface of all cells except rbc
- identify cell as “self” (part of the body) - not foreign
3) Membrane Carbohydrates
- glycoproteins and glycolipids
- differ for every cell type - allow cells to recognize type e.g. sperm recognizes
egg
B) Membrane Transport
- movement of material between the intra- and extracellular fluids
- terms:
- solute – substance dissolved in a solution
- solvent – substance solute is dissolved in e.g. water
- types of transport:
1) Passive Transport
- no energy required (no ATP)
- movement from a high to low concentration (i.e. down its
concentration gradient)
- the greater the difference in concentration = the more & faster the
molecules will move
- types:
a) Simple diffusion (solute movement)
- solute crosses through cell membrane bilayer ∴ small,
lipid soluble (O2, CO2, etc)
b) Facilitated diffusion (solute movement)
- ions diffuse through membrane via protein channels
c) Facilitated transport (solute movement)
- large, charged or water-soluble molecules
- move across membrane using a specific carrier protein
- must bind to protein to be transported
- e.g. glucose into liver or skel. muscle cells
d) Osmosis (solvent movement)
- movement of H2O across a semipermeable membrane
(permeable to H2O) due to [H2O] difference (H2O moves
down its concentration gradient) via pores
(channels) or across the membrane bilayer
- note:
- high [H2O] = low [solute]- dilute solution
Document Summary
Topic ii: cell physiology i: the cell membrane, phospholipid bilayer. Barrier to water soluble substances not to small molecules and/or lipid soluble molecules (e. g. o2 & co2: membrane proteins, transport proteins, channels, carrier proteins specific ions. Can be: (cid:3843) gated: can open or close in response to stimuli (cid:3844) non-gated (= leakage channels): always open. Bind solute + carry it across membrane. Allow protein carrier-mediated facilitated transport or active. E. g. glucose transporters transport: receptor proteins neurotransmitters (nt) Can bind specific extracellular molecules (= ligands) e. g. hormones, E. g. glucose uptake: insulin binds to receptor on skel. muscle or adipose tissue, triggers movement of more glucose transporters to cell, glucose movement from blood into cells membrane, enzymes. Control chemical reactions on outer or inner surface. E. g. 2: na+/k+- atpase - all cells have this: joining proteins. Anchor cell membrane to cytoskeleton or an adjacent cell: junctional proteins between cells forming: 2: extracellular fibres (usually glycoproteins, identifying proteins.
