cell physiology 1 Flashcards
the cell membrane: phospholipid bilayer
- continuous layer around the cell
- barrier to water soluble substances - not to small molecules and/or lipid soluble molecules
the cell membrane: membrane proteins
a) transport proteins
- channels( like tunnels that go across the cell membrane letting certain material in)
- form pore in membrane
- selectively permit channel-mediated facilitated diffusion of water or specific ions depending on the channel. ( there are specific channels for salt or sugars)
- can be: gated which can open or close in response to stimuli. or non gated (leakage channels) always open, not always closed because it is useless
- carrier proteins
- bind solute + carry it across membrane
- allow protein carrier-mediated facilitated transport OR active transport e.g. glucose transporters (transported by both)
b) receptor proteins
- can bind specific extracellular molecules (as a group called ligands)
-e.g. glucose uptake:
I) nsulin binds to receptor on skeletal muscle or adipose tissue
ii) triggers movement of more glucose transporters to cell membranes
iii) increase glucose movement from blood in cells
c) enzymes
- control chemical reactions on outer or inner surface
-e.g. acetylcholinesterase
- e.g. Na/K - ATPase - all cells have this
d) joining proteins
I) anchor cell membrane to cytoskeleton or an adjacent cell
II) junctional proteins: between cells forming:
- desmosomes, tight junctions and gap junctions
iii)extracellular fibres (usually glycoproteins)
e.g. major histocompatibility complex (MHC) proteins which are on the surface of all cells except RBC and identifies the cell as “self”
membrane carbohydrates
- glycoproteins and glycolipids
- differ for every cell type - allow cells to recognize type. e.g. sperm recognize the egg. the egg has the right kind of carbs for the sperm and can realize that everything around it doesn’t.
membrane transport: passive transport
- going downhill, not putting any energy into it (no ATP)
- movement from a high concentration to a low concentration = the more & faster the molecules will move. e.g. if you tape two boxes together with a hole between them, if you had 1000 molecules in one box and 2 in the other, it is more likely for the 1000 molecules hitting the hole than the 2 molecules going through the hole. making the number even out in each box.
membrane transport: active transport
- going uphill, takes energy
membrane transport
movement of material between the intra and extra cellular fluids, in and out of the cell
solute
substance dissolved in a solution
- solute concentration depends on the number of ions or molecules, not the type
solvent
substance solute is dissolved in e.g. water
what are the types of passive transport
a) simple diffusion (solute movement)
- solute crosses through cell membrane bilayer which is a small lipid soluble. can hit any channel and will pass through
b) facilitated (needs help) diffusion (solute movement)
- ions diffuse through membrane via protein channels. has to have a protein channel to get across
c) facilitated transport (solute movement)
- large, charged or water soluble molecules, must bind to a protein to be transported
- move across membrane using a specific carrier protein
- e.g. glucose into liver cells or skeletal muscle cells
d) osmosis (SOLVENT movement)
- if you have high concentration of solute you have a low concentration of solvent
- movement of water across a semipermeable membrane (permeable to water) due to water concentration difference (water moves down its concentration gradient) through pores (channels) or across the membrane bilayer
- note high concentration of water =low solute concentration (dilute solution) vis versa ( solute concentration)
osmotic pressure (OP)
- pressure that must be applied to prevent movement of water from a pure water solution (S1) across a semipermeable membrane into another solution (S2)
- the greater salt concentration in S2 the great OP and lower water concentration the more water will move in (down gradient) equals the more OP to stop its moving.
- OP is used as a measure of the solute concentration in a solution, using osmosis to find this.
- high OP= high concentration solute ( low water concentration) + visa versa
tonicity
related to osmotic pressure.
response of a cell immersed in a solution which depends on the concentration solute
what are the three classifications of tonicity
- isotonic solution: doesn’t lose or gain water. cell neither swells or shrinks (what it should look like)
- ECF and ICF have equal OP ( cytosol is the same as water)
2.hypotonic solution: cell swells (takes in water)
- has less water than the solution it is in going into the cell, making it swell.
ECF is higher (H20) lower OP than IC. - hypertonic solution: cytoskeleton sticks out. cell shrinks (losses H20 (has more water inside of it than outside so it moves out)
ECF has lower H20 than ICF which draws water out, deals with the solvent
lysis
caused by the rupture of the cell
if in a RBC=hemolysis
tonicity uses
- body uses it to monitor water concentration.
- injecting 10% sucrose solution (hypertonic). will draw water into blood from tissues, if someone has a brain injury and is swelling, it cant go anywhere because of the skull, draws the blood out of the brain to decrease the swelling.
osmosis role in regulation of concentration of solute
concentration of solutes in body fluids must be maintained within narrow limits or cells will die.
what are the major body fluids
- extracellular fluid (ECFs)
- blood plasma: in blood vessels
- cerebospinal fluid
- interstitial fluid (ISF) - around liver cells and any other cells besides RBC - intracellular fluid: inside any cells
what happens if the body loses H20 than solute
sweat is created and blood concentration goes up, making your cheeks go red.
- blood OP goes up making fluid move from the interstitial fluid from tissues into blood.
- drink water to replace the what you have lost from sweating.
- response: thirst and decrease renal H20 loss which leads to lower urine production.
bulk flow
movement of fluid (+ solutes) due to a pressure gradient (high pressure to low pressure) like poking a tiny hole into a hose.
hydrostatic pressure
high P of a fluid pressing against a surface e.g. cell membrane, blood vessel wall. extracellular membrane pushing against the cell membrane.
example of hydrostatic pressure
if blood has a higher pressure than ISF, fluid flows out of capillary which is filtration.
if ISF has a higher pressure than blood, fluid flows from ISF into capillary which is absorption
what are the 2 active processes
1) active transport
2) vesicular transport
active transport
substances move against concentration gradient (low to high) walking from a bottom of a hill to the top
- always protein carrier-mediated or you cannot use the energy
types of active transport
primary active transport
- has ATP in its name
