patho/phys exam 1 Flashcards

Question

MEMBRANE TRANSPORT

Answer 1

unassisted: no channels or carriers involved - diffusion - osmosis - movement along an electrical gradient assisted - vesicular transport - carrier mediated vesicular transport - endocytosis - exocytosis carrier mediated - facilitated diffusion - active transport active transport - primary active transport - secondary active transport caveolae: membrane transport and signal transduction - sphingolipids rafts found in caveolae

Answer 2

occurs from side A to B until there is equal concentrations on both side and reaches equilibrium no net diffusion if a substance can permeate the membrane if the membrane is impermeable to a substance diffusion continues until sides A & B have the same concentrations this process is dynamic so if 1 molecule moves from A to B, one molecule moves from B to A

Answer 3

Rules/Properties of Diffusion – Occurs only if substances can cross the membrane – Always occurs from the area of high to low concentration – No energy required, a passive mechanism, e.g.O2-CO2 - concentration gradient of substance: increase rate - surface area of membrane: increase - lipid solubility: increase rate - molecular weight of substance: decreased rate - distance (thickness): decrease rate

Answer 4

EG: charge difference between adjacent areas * Promotes movement towards the opposite charge * Electrical and concentration gradient = electrochemical gradient Opposite charges attract

Answer 5

Net diffusion of water down its own concentration gradient separated by the semi-permeable membrane pure water: 100% water concentration, 0% solute concentration solution: 90% water concentration, 10% solute concentration area with higher H2O concentration lower solute concentration flows to area with lower H2O concentration higher solute concentration similar to diffusion but now movement of H2O

Answer 6

Membrane (permeable to both water and solute) - Water concentrations equal * Solute concentrations equal * No further net diffusion * Steady-state exists Membrane (permeable to H2O but impermeable to solute) - Water concentrations equal * Solute concentrations equal * No further net diffusion * Steady-state exists - there was more solute on one side so water moved to make both sides equal but the solute did not move! Membrane (permeable to H2O but impermeable to solute) - Water concentration not equal * Solute concentration not equal * Osmosis ceases when osmotic pressure is exactly balanced by opposing hydrostatic pressure

Answer 7

Important for water movement in/out of cells – Intravenous administration, eye drops, etc. * Tonicity: conc. of non-penetrating solutes * Osmolarity: concentration of non-penetrating and penetrating solutes normal cell conditions: 300 mOsm 0.9% NaCl hypotonic solution <300 mOsm <0.9% NaCl hypertonic solution >300 mOsm >0.9% NaCl tonicity is much higher

Answer 8

Utilize carriers: membrane-spanning proteins - so these are integral proteins not extrinsic proteins Able to flip-flop, a reversible change in shape Binding sites of substance on carriers exposed alternatively to either side of the membrane on binding with molecules to be transported, the carrier changes its conformation

Answer 9

desmosomes aka adhering junctions tight jxns aka impermeable junctions gap jxn aka communicating junction

Answer 10

aka adhering junctions each cell has a plaque and the cells connect by glycoprotein filaments that are attached to the plaque of each cell these form spot rivets rivets mean joining sheets together desmosomes form spot rivets and hold cells together keratin is also within the cells and is attached to the plaques on the edges of the cells you will find desmosomes in tissues that have to stretch like the heart and uterus. Desmosomes make sure that the cells will not rupture and make sure that the cells split apart

Answer 11

aka impermeable junctions these are found in epithelial cells to prevent substances from the blood from moving directly to the ECM rather than going into the cells and being absorbed which is what we want! they are made of claudins claudins mean to close the tight function fuse together at the kiss sites of the cell

Answer 12

needed for cell-to-cell communication these proteins are connexons connexons have 6 sections and have a small diameter 2 connexons link together two cells ions flow thru this due to speed and efficiency gap jxns allow all the cells to be stimulated simultaneously when is needed for uterus contraction for example

Answer 13

A. desmosomes - these prevent cells from coming apart so they are the strongest kind of specialized cell junction - adhering junctions

Answer 14

A. simple diffusion B. facilitated diffusion

Answer 15

C. primary active transport

Answer 16

A. simple diffusion

Answer 17

osmotic pressure

Answer 18

passive because opposite charges attract

Answer 19

transported molecule cotransported ion uniport: transport 1 substance symport: transport 2 substances in the same direction antiport: transport 2 substances in opposite directions

Answer 20

Specificity and selectivity: – One carrier for one (or closely related) substance – Different cells may have different carriers. if can transport glycine the can transport alanine but not glucose. iodine is in thyroid gland – Dysfunction leads to diseases: such as cystinuria which is cysteine in urine and can lead to urinary stones * Saturation: – Finite number of carriers, affinity/number can be regulated – Tm = transport maximum (rate-limiting factor in transport) - as [ ] increases, once all the carriers are saturated then Tm is reached. This determines how much substance gets transported with time -> rate limiting step insulin can affect amount of glucose in cell * Competition: – Occurs when carrier transfers closely related substances – Reduces the rate of transfer of each substance transported – Does not affect the total amount of transfer, so no matter what the total number transported is the same!

Answer 21

1 - carrier protein takes conformation in which solute binding site is exposed to region of higher concentration 2 - solute molecules bind to a carrier protein 3 - carrier protein changes conformation so that the binding site is exposed to regions of lower concentration 4 - transported solute is released and carrier protein returns to conformations in step 1 molecules go from an area of high concentration to an area of low concentration this continues until the [ ] gradient is at equilibrium

Answer 22

Example: transport of glucose into the cell * Movement of a substance from high to low concentration * Does not require energy graph: line A: steadily increases - this is simple diffusion, transport will occur as long there is a [ ] gradient line B: steadily increases, then plateaus: this is facilitated diffusion, increases then reaches saturation which happens when a finite number of carriers is reached

Answer 23

Movement of a substance from low to high concentration – Example: uptake of iodine in thyroid gland cells Two types: – Primary active transport: * ATP required directly; carrier splits ATP (has ATPase activity) * Requires energy (ATP) to change the shape of the carrier * AKA “pumps” (hydrogen ion pump, Na-K-ATPase pump) – Secondary active transport: * ATP not required directly; carrier lacks ATPase activity ATPase splits ATP into ADP, Pi and energy

Answer 24

1 - pump has 3 high-affinity sites for Na+ and 2 low-affinity sites for K+ when exposed to ICF - normal Na+ concentration gradient: out to in - normal K+ concentration gradient: in to out 2 - when 2 Na+ from ICF (where Na+ concentration is low) binds to the pump, it splits ATP into ADP plus phosphate; the phosphate group binds to the pump 3 - phosphorylation causes the pump to change conformation so that Na+ binding sites are exposed to the opposite sides of the membrane and 3 Na+ are released to ECF (where Na+ concentration is high) as the affinity of Na+ binding sites greatly decreases 4 - The change in shape also exposes the pump's binding sites for K+ to ECF and greatly increases the affinity of K+ sites 5 - when 2 K+. from ECF (where K+ concentration is low) binds to the pump, it releases the phosphate group. Dephosphorylation causes the pump to revert to its original conformation 6 - 2 K+ are released to ICF (where K+ concentration is high) as the affinity of K+ binding sites markedly decreases during a change in shape. At the same time, the affinity of Na+ binding sites greatly increases, returning the process to step 1 uses carrier molecule to transport from low [ ] to high [ ] normal conditions: [Na+] higher outside, lower inside [K] higher inside, lower outside but now: we want as few Na+ inside as possible so Na+ is pumped from [low] which is inside the cell to [high] which is outside the cell and now we also want to pump the K+ inside the cell

Answer 25

Establishes Na+ and K+ concentration gradients: electrical signals * Regulates cell volume by controlling tonicity - if it stops then the Na+ will build up in cell and draw H2O in and cause cell to burst * Energy (ATP) used also serves as secondary active transport of the Na+/Glucose symporter

Answer 26

primary active transport: - establishes Na+ concentration gradient from lumen to cell which drives the.... secondary active transport - creating glucose concentration gradient from cell to blood used for facilitated diffusion. Increase affinity fro glucose in detail: lumen of the intestine: - Na+ is high on the outiside - [Na+] is low on the inside - the Na+/K+ ATPase moves Na+ outside from the area of low [ ] to high - SGLT moves glucose and Na+ from outside of the cell to inside in the same direction (symporter). This is the secondary active transport - then glucose moves from inside the cell to the outside the cell when glucose is low in the blood

Answer 27

Co-transport of glucose and amino acids * found in Intestinal and kidney cells, against concentration gradients * Energy not expended directly, mediated by co-transport carriers * Contain two binding sites, one for Na other for nutrient molecule * Na binding  affinity for glucose binding * Transported out in blood by facilitated diffusion SGLT2 - absorbs sugar from the urine so some diabetic drugs inhibits this carrier

Answer 28

Large polar molecules (hormones) and multi-molecular materials (bacteria) - cannot fit carrier protein * Wrapped up in a membrane-enclosed vesicle * Requires energy - active process * Materials inside do not mix with cytosol, fuse with target membrane for transfer *Two types: endocytosis and exocytosis

Answer 29

Endocytosis: substances transported into the cell, can fuse with lysosome or be released on the other side of the cell – Pinocytosis (non-selective uptake of ECF) – Receptor-mediated endocytosis (selective uptake of large molecule) – Phagocytosis (selective uptake of multimolecular particle) * Exocytosis: substances transported out of the cell, accomplish two major purposes – Provides a mechanism for secreting hormones/enzymes (large polar molecules) – Enables cell to add specific membrane components: carriers, channels, receptors * Rate of endocytosis = rate of exocytosis

Answer 30

exocytosis: a secretory vesicle fuses with the plasma membrane, releasing the vesicle contents to the cell exterior. The vesicle membrane becomes part of the plasma membrane endocytosis: materials from the cell exterior are enclosed in a segment of the plasma membrane that pockets inward and pinches off as an endocytic vesicle

Answer 31

pinocytosis 1 - solute molecules and water molecules are outside the plasma membrane 2 - membrane pockets inward enclosing solute molecules and water molecules 3 - pocket pinches off as endocytic vesicle containing a sample of ECF receptor-mediated endocytosis 1 - substances attach to membrane receptors 2 - membrane pockets inward 3 - pocket pinches off as endocytic vesicle containing the target molecule phagocytosis 1 - pseudopods begin to surround prey 2 - pseudopods close around prey 3 - prey is enclosed in an endocytic vesicle (phagosome) that sinks into the cytoplasm 4 - lysosome fuses with vesicle, releasing enzymes that attack material inside the vesicle

Answer 32

ion channels

Answer 33

true - the Na+/K+ pump

Answer 34

true - facilitate diffusion and 1 or 2 active transport

Answer 35

I, II, III

Answer 36

false - you can have facilitated diffusion which is via assistance from carrier proteins