Topic II- Cell Physiology I Flashcards
phospholipid bilayer
- continuous layer around cell
- barrier to water soluble substances- NOT to small molecules (O2, CO2) and lipid soluble molecules
Membrane Proteins
a) transport proteins
i. channels
ii. carrier proteins
b) receptor proteins
c) enzymes
d) joining proteins
e) identifying proteins
Transport Proteins
channels
i. gated
ii. non-gated
carrier proteins
channels
- form pore in membrane
- selectively permit channel-mediated facilitated diffusion of water/ specific ions
- can be gated or non-gated
gated channels
can open or close- in response to stimuli
non-gated channels
(= leakage channels)
always open
carrier proteins
- bind solute + carry it across membrane
- allow protein carrier-mediated facilitated transport OR active transport
- e.g. glucose transporters
receptor proteins
- can bind specific extracellular molecules (=ligands) e.g. hormones, neurotransmitters
- e.g. glucose uptake:
i. insulin binds to receptor on skeletal muscle or adipose tissue
ii. triggers movement of more glucose transporters to cell membrane
iii. increases glucose movement from blood into cells
enzymes
- control chemical reactions on outer or inner surface
- i.e. 1: acetylcholinesterase
- i.e. 2: Na+/K+-ATPase all cells have these
joining proteins
- anchor cell membrane to cytoskeleton or an adjacent cell
i. junctional proteins between cells forming: - desmosomes, tight junctions, gap junctions
ii. extracellular fibres (usually glycoproteins)
identifying proteins
i. e. Major Histocompatibility Complex (MHC) proteins
- on surface of all cells except rbi
- identify cell as self (part of the body)- not foreign
Membrane Carbohydrates
- glycoproteins and glycolipids
- differ for every cell type- allow cells to recognize type i.e. sperm recognizes egg
