2. cell physiology 1 Flashcards
the cell membrane has
phospholipid bilayer
membrane proteins
membrane carbohydrates
phospholipid bilayer
*continuous layer around the cell
*barrier to water soluble substances – NOT to small molecules (O2 & CO2) and lipid
soluble molecules
membrane proteins are:
- transport proteins
- receptor proteins
- enzymes
- joining proteins
- identifying proteins
transport protein types:
channels
carrier proteins
channels
- form pore in membrane
- selectively permit channelCmediated facilitated diffusion of water &
specific ions - Can be:
1 gated: can open or close – when signaled
2 nonCgated (= leakage channels): always open
carrier proteins
- bind solute + carry it across membrane
- allow protein carrierCmediated facilitated transport OR active
transport - e.g. glucose transporters
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
enzymes
- control chemical reactions on outer or inner surface
- e.g. acetylcholinesterase
- e.g.2: Na+/K+C ATPase C all cells have these
joining proteins
- control anchor cell membrane to cytoskeleton or an adjacent cell
i. junctional proteins between cells forming: - —- desmosomes, tight junctions, and gap junctions
ii. extracellular fibers (usually glycoproteins)
identifying proteins
- e.g. Major Histocompatibility Complex (MHC) proteins
o on surface of all cells except rbc
o identify cell as “self” (part of the body) – not foreign
membrane carbohydrates
- glycoproteins and glycolipids
* differs for every cell type C allow cells to recognize type e.g. sperm recognizes egg
membrane transport
movement of material between the intra and extra cellular fluids
solute
substance dissolved in a solution
solvent
substance solute is dissolved in e.g. water
types of transport
passive
active
passive transport
- no energy required (no ATP)
- movement from a high to low concentration (i.e. down its conc. gradient) * the greater the difference in concentration = the more molecules want to move
passive transport types
simple diffusion facilitated diffusion facilitated transport osmosis bulk flow
simple diffusion
solute movement
*solute diffuses directly through cell membrane bilayer therefore small, lipid soluble (O2, CO2, etc.)
facilitated diffusion
solute movement
*ions diffuse through membrane by protein channels
facilitated transport
solute movement
- large, charged or water soluble molecules
- diffuse across membrane using a specific carrier protein - must bind to protein to be transported
- eg, glucose into liver or skeletal muscle
osmosis
solvent movement
- movement of H2O across a semipermeable membrane (permeable to H2O) due to [H2O] difference (H2O moves down it’s concentration gradient ) by pores (channels) or across the membrane bilayer
- NOTE-
- high [H2O] = low [solute] (dilute solution)
- low [H2O] = high [solute] (concentrated solution)
- [solute] depends on the number of ions of molecules not the type
high solute and low solvent
high osmotic pressure
low solute and high solvent
low osmotic pressure
osmotic pressure
- pressure that must be applied to prevent movement
of H2O from a pure H2O solution (S1) across a semipermeable membrane into another solution (S2)
i. if S2 has high [salt] (low [H2O]) then more H2O will move into it ⇒ requires pressure to stop H20 moving into S2
——————- Therefore the greater [salt] in solution the greater OP and lower [H2O] ⇒ water will want to move in (down gradient)
ii. S1 & S2 = pure H2O ⇒ no P required to prevent H2O movement (no gradient) ∴ S1, S2 OP = 0 - OP is used as a measure of the [solute] of a solution o high OP = high [solute] (low [H2O]) + vice
versa
tonicity
o response of a cell immersed in a solution
* depends on [solute] (and permeability of cell membrane to solute)
o uses:
* injecting 10% sucrose solution (hypertonic)
will move water to blood stream
* e.g. use to ⇓ brain edema (swelling)
tonicity classificatinons
hypotonic solution
hypertonic solutions
isotonic solution
hypotonic solution
- ECF has lower OP (higher [H2O]) than ICF (cytosol)
- cell swells (takes in water) + may burst
- swelling can rupture cell = lysis
- ——- if rbc = hemolysis
hypertonic solution
- ECF has higher OP (lower
[H2O]) than ICF (cytosol) * cell shrinks (loses H2O)
isotonic solution
- ECF and ICF have equal OP
- cell neither swells nor shrinks
- rbc C all [solutes] within equals
a 0.9% saline solution (= normal saline)
osmosis role in solute regulation:
o Concentration of solutes in body fluids must be
maintained within narrow limits or cells will die
*major body fluids:
-extracellular fluids (ECFs)
-intracellular fluid (ICF)
extracellular fluids
bood plasma interstitital fluid (ISF)
osmosis eg e.g. If body loses H2O (e.g. sweat) ⇒ ⇑ [blood] blood OP ⇑ ⇒ fluid moves from tissues to blood
response = thirst and ⇓ renal H2O loss which leads to ⇓ urine production
bulk flow
- movement of fluid (+ solutes) due to a pressure gradient
(high pressure to low pressure) - hydrostatic pressure = P of a fluid pressing against a surface
o e.g. cell membrane, blood vessel wall (= blood pressure)
o e.g. Capillary – if blood has higher pressure than ISF, fluid flows out of the capillary (= filtration)
active process require
Require energy (ATP)
active processes types
active transport and vesicular transport
ative transport types
primary active transport
secondary active transport
primary active transport
- molecular pumps C ATP breakdown is directly
part of transport process - e.g. Na+/K+CATPase Pump – 3 Na+ out of cell
and 2 K+ in per ATP
secondary active trasport
- cotransport (use of ATP is indirect)
- e.g. glucose entry at small intestine – 2 steps:
1. Na+ gradient established by Na+/K+C ATPase (ATP use step)
2. glucose & Na+ both must bind to carrier and are cotransported into the cell ⇒ Na+ moving down its concentration gradient drives in glucose against its concentration gradient (transport step)
vesicular transport
substance is surrounded by a membrane within a cell (vesicle)
active transport
- substance move against conc. gradient (low to high)
- always protein carrier-mediated
vesicular transport types
endocytosis
exocytosis
endocytosis
movement into a cell
- phagocytosis
- pinocytosis
phagocytosis
- large items into cell (e.g. bacteria)
- =”cell eating”`
pinocytosis
- fluids (+dissolved substances)
- =”cell drinking”
exocytosis
– movement out of cell
* vesicles containing hormones, enzymes,
neurotransmitters, etc.
* fuse with cell membrane releasing contents
into ECF (triggered by a rise in cytosolic Ca++)
