Topic 2 Flashcards
Cell membrane composed of
- phospholipid bilayer
- membrane proteins
- membrane carbohydrates
Phospholipid bilayer
barrier to water soluble substances, NOT to any small molecules and lipid soluble molecules
5 types of membrane proteins
- transport Proteins
- receptor proteins
- enzymes
- joining proteins
- identifying proteins
2 types of transport proteins
- channels
- carrier porteins
Channels on cell membrane
form pore in membrane, selectively permit channel/medicated facilitated diffusion of water and specific ions
Channels on cell membrane can be..
- gated: can open or close when singled
- non gated (leakage channels) always open
Receptor proteins
can bind specific ligands
Ligands
extracellular molecules (ex: hormones, neurotransmitters)
Carrier proteins
bind solute and carry it across membrane, allow protein carrier mediated facilitated transport OR active transport
Example of receptor proteins
- glucose uptake results in insulin binds to receptor on skel. muscle/adipose tissue.
- triggers movement of more glucose transporters to cell membrane.
- increase glucose movement from blood into cells
Enzymes
control chemical reactions on outer or inner surface, CAN BE A PROTEIN
Identifying proteins
identify cell as “self” (part of body) not foreign
Example of identifying proteins
major histocompatibility complex (MHC) proteins on surface of all cells except rbc
Membrane carbohydrates
glycoproteins and glycolipids. differ for every cell type, allows cells to recognize other cells
Example of membrane carbohydrate
sperm recognizing a an egg
Membrane transport
movement of material between intra and extra cellular fluids`
Solute
substance dissolved in a solution
Solvent
substance solute is dissolved in
2 types of transport
- active processes
- passive transport
Passive transport
no NRG required (no ATP).
Diffusion
movement from a high to low concentration
The greater the difference in concentration =
the more molecules want to move
Types of passive transport
- simple diffusion
- facilitated fissuion
- facilitated transport
- osmosis
- bulk flow
Simple diffusion
solute diffuses through cell membrane bilayer (small, lipid soluble) ex: O2, CO2
Facilitated diffusion
ions diffuse through membrane via protein channels
Facilitated transport
large, charged or water soluble molecules diffuse across membrane using specific carrier proteins
Carrier proteins must …
bind to protein to be transported
3 types of solute movement
- simple diffusion
- facilitated diffusion
- facilitated transport
Osmosis
movement of H2O across a semipermeable membrane due to H2O difference via pores or across membrane bilayer
High H2O =
low solute (dilute solution)
Low H2O =
high solute (concentrated solution)
Solute depends on the..
number of ions or molecules not the type
Osmotic pressure
pressure must be applied to prevent movement of H2O from a pure H2O solution (S1) across a semipermeable membrane into another solution (S2)
If S2 has high salt, low H2O the more..
H2O wil move into it which requires pressure to stop H2O moving into S2
S1 and S2 = pure H2O results in
no pressure required to prevent H2O movement (no gradient) so OP=0
OP is used as a ..
measure of the solute of a solution
High OP = ____ _____
Low OP = _____ _____
high solute; low solute
Tonicity
response of a cell immersed in a solution
Tonicity depends on..
solute and permeability of cell membrane to solute
3 types of tonicity
- hypertonic
- hypotonic
- isotonic
Hypotonic solution
ECF has lower OP (high H2O) than ICF, cell swells and may burst
Lysis
swelling causing rupture of cell (ex: hemolysis for rbc)
Hypertonic solution
ECF has higher OP (lower H2O) than OCF, cell shrinks
Isotonic
ECF and ICF have equal OP
Example of isotonic solution
rbc, all solutes within equals 0.9% saline solution
Uses of tonicity
injecting 10% sucrose solution (hypertonic) will move water to blood stream (used to lower brain edema/swelling)
Osmosis role in solute regulation
concentration of solutes in body fluids must be maintained w/in narrow limits or cells will die
Major body fluids
- extracellular fluids
- intracellular fluids
2 examples of extracellular fluids
- blood plasma
- interstitial fluid (ISF)
Example of osmosis role in body regulation
if body loses H2O (Sweat) then increase blood/blood OP then fluid moves from tissues to blood, response = thirst6 and decrease renal H2O loss (less peeing)
Bulk flow
movement of fluid and solutes due to a pressure gradient (high to low pressure)
Hydrostatic pressure
pressure of a fluid pressing against a surface
Example of bulk flow
capillary; if blood has higher pressure than ISF fluid slow out of the capillary
Active processes
require energy (ATP)
2 types of active processes
- active transport
- vesicular transport
Active transport
substances move against concentration gradient (low to high). ALWAYS protein carrier-mediated
2 types of active transport
- primary (1°) active transport
- secondary (2°) active transport
Primary active transport
molecular pumps, ATP breakdown is directly part of transport process (ex: Na/L ATPase pump)
Secondary active transport
cotransport (use of ATP is indirect)
Example of secondary active transport
glucose entry at small intestine 2 steps:
- Na gradient established by Na/K ATPase
- glucose and Na both must bind to carrier and are cotransported into the cell so Na moving down its concentration gradient drives in glucose against its conc. gradient
Vesicular transport
substance is surrounded by a membrane w/ in a cell (vesicle)
2 types of vesicular transport
- endocytosis
- exocytosis
Endocytosis
movement into a cell
2 types of endocytosis
- phagocytosis
- pinocytosis
Phagocytosis
large items into a cell, cell eating (ex: bacteria)
Pinocytosis
fluids and dissolved substances, cell drinking
Exocytosis
movement out of cell, vesicles containing hormones, enzymes, nt fuse. fuse will cell membrane releasing contents into ECF
Joiner/linker proteins
anchor to membrane of cytoskeleton or an adjacent cell
2 types of joiner proteins
- junctional proteins between cell forming: desmosomes, tight junctions, gap junctions
- extracellular fibres (glycoproteins)
