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Cell Biology Exam 2 > Membrane transport Part 1 > Flashcards

Membrane transport Part 1 Flashcards

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1
Q

Rate of diffusion is affected by

A

hydrophobicity and size

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2
Q

Hydrophobic molecules and synthetic lipid bilayer

A

moves fast

ATP O2 CO2 N2 steroid hormones

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3
Q

small uncharged polar molecules and synthetic lipid bilayer

A

at slower rate

H2O urea glycerol NH3

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4
Q

Large uncharged polar molecules and synthetic lipid bilayer

A

v slow rate

glucose sucrose

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5
Q

ions and synthetic lipid bilayer

A

hydration schell - impermiable to membrane

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6
Q

two main classes of transport proteins

A

Transporters and Channels

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7
Q

difference between enzymes/substrate and transport cycle (transporter and solute)

A

solute is not altered/changed

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8
Q

Transporters

A

carriers, permeases

possess solute binding sites: Solute binds to binding site

Conformational change is transporter after solute binds

same still apply from enzime substrate - Vmax max rate of transport, rate when fully saturated - Km, binding affinity, solute and solute binding

open and close randomly but concentration gradient makes solute more likely to bind and cause change

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9
Q

Channels

A

interact with solutes more weakly
no energy requirement
no binding site
all channels alow solutes to cross the membrane passivly downhill
formation of pores do not exibit solute binding sites

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10
Q

which has fater rate of tansport, chanel or transporters

A

chanel because does not have to change conformations

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11
Q

Passive transport

A

Movement of solutes “down” their concentration gradient (High concentration to Low concentration)

If solute is charged, movement also dependent on electrical gradient (membrane potential).

Concentration + charge=“electrochemical gradient”

no energy requirement

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12
Q

Active transport

A

Movement of solutes “against” their concentration gradient. Always mediated by transporters

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13
Q

Primary Active transport

A

Free energy of ATP hydrolysis used to drive “uphill” movement of solutes.

direct energy reqirement - from ATP hydrolosis

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14
Q

Secondary Active transport

A

Ion gradient generated by ATPase elsewhere (indirect requirement of ATP).

Secondary active transport harnesses energy released from ion gradient by one molecule going down its electrochemical gradient to drive a different molecule against its gradient

indirect energy requirement - stored energy in gradent - used in second active transport

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15
Q

Gradients across the membrane (with and without charge_

A

without charge difference - move across gradient

with charge opposite - move faster

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16
Q

Uniports

A

unidirectional
one solute movement

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17
Q

Symports

A

simultaneous movement of more than one solute in one direction

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18
Q

Antiports

A

simultaneous movement of more than one solute in opposite directions

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19
Q

GLUT

A

glucose transporter - passive, facilitated - when concentration gradients change - moves opposite ways

Glc fits into GLUT binding site.

Glc binding drives conformational change.

Dissociation driven by low [Glc].

GLUT bounces back to original conformation.

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20
Q

Classes of ATP-driven pumps

A
  1. P type pumps
  2. ABC (ATP binding cassette) transporters
  3. V type pumps

all use ATP - bind to transporter (hydrolized-> energy)

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21
Q

P-type pumps

A

Formation, maintenance of

Na+, H+, and Ca2+ gradients.

Self-phosphorylate during cycle.

Mantain order in body, maintaion ion gradents, mediate cellular processes

22
Q

ABC (ATP-Binding Cassette) transporters

A

Transport variety of nutrients, toxins, ions.

most abundant
medical relevance - drug resistance - involve in removing drugs

23
Q

V-type pumps

A

Acifigy vaculoar compartments

use engery from ATP hydroslos - move H across - more acific enviorment (ex/ use in digestion)

24
Q

Ca2+ pump

in eukaryotic cells

A

(P-type ATPase)

Eurcharylotic cells - (invest a lot of energy to) maintain very low concentrations of Ca2+ in their cytosol and very high extracellular Ca2+

Steep gradient maintained (Ca2+pumped out by Ca2+ pump and Na+Ca2+ Exchanger) at plasma membrane

25
Q

When action potential depolarizes the muscle cell plasma membrane __

A

Ca2+ is released into cytosol from the sarcoplasmic reticulum through Ca2+ release channels, which stimulates muscle to contract

26
Q

Sarcoplasmic Reticulum

A

Specialized Endoplasmic reticulum in muscle cell cytoplasm, intracellular storage of Calcium ions

27
Q

Ca2+ pump in the Sarcoplasmic Reticulum

A

moves Ca2+ from cytosol back to sarcoplasmic reticulum, end of muscle contraction

28
Q

Structure of Ca2+ Pump

A
29
Q

Ca2+ cycle

A
  1. ATP bound Ca2+ (two) can bind
  2. binding causes conformational change, passage way is closed
  3. ATP is hydrolyzed (ATP to ADT and P) Phosphate transfer reaction
  4. ADP excanged for ATP - conformational change - passage is opened to lumen
  5. proton (two) is picked up (also with water) to stabalize empty binding site - passage is closed to lumen
  6. hydrolosis of phosphate, pack to orional conformation, so Ca2+ can be transpoted again (and again)
30
Q

Why are the maximum rates of transport by transporters and channels thought to be so different.

A

because transportors binding of solvent on specific site (with weak ineractions) - slower

31
Q

The permeability of a protein-free lipid bilayer to various molecules depends on their properties. Sort the following in order of low to high permeability from left to right.

A. O2
B. ATP
C. Na+
D. Glucose

A

B
C
D
A

32
Q

Na+K+ Pump, concentration of K+ ions and Na+ ions

A

Concentration of K+ ions higher inside cells than outside, reverse is true of Na+ ions

33
Q

Na+ gradient (in Na+K+ pump) drives

A

transport of most nutrients into animal cells (1/3 animal cells energy devoted to this pump)

34
Q

Na+K+ pump is ___

A

electrogenic- volated difference across membrane (membrane potental) - when charges do not balansse out.

also antiporter

35
Q

Na+K+ pump cycle

A
  1. Na binds to pump
  2. pump phosporilates itself (ATP to ADP and P)
  3. phosporlation triggers conformational change, Na is ejected
  4. K binds
  5. pump is dephosporlated
  6. pump returned to orional conformation, K is ejected
36
Q

ABC Transporter family

A

Largest family of Membrane Transport Proteins

37
Q

ABC transporter bacterial vs eukaryotic

A

bacterial - import process - to inside cell
eukaryotic - export - to out of cell

38
Q

ABC transporter steps

A

2 ATP added (each own domain), small soluble molecule binds
hydrolized (2ATP to 2ADP and phospate) - opens

39
Q

Clinical importance of ABC transporters in Eukaryotic cells

A

Multi-drug resistance (MDR) protein, also called P-glycoprotein: high levels in cancer cells, makes cells resistant to cytotoxic drugs (chemo).

Plasmodium falciparum (causes Malaria): transporter pumps out Chloroquine (drug resistance)

40
Q

V type Pump

A

Present in vacuolar compartments.
(Lysosomes, endosomes, Golgi.)

Uses deltaG of ATP hydrolysis to make H+ gradient.

41
Q

F type ATPases

A

Structurally related to V type pumps (exact opposite, protein gradient to make ATP)

Instead of using ATP hydrolysis to drive H+ transport, they use the H+ gradient across the membrane to drive the synthesis of ATP

is still considered primary active transport

42
Q

Uncouplers

A

collapse proton gradient by equalizing proton concentrations on both sides of the membrane

43
Q

Dinitrophenol (DNP)
Caused ___

A

Diet pill in 1920s

Caused increased oxygen consumption and an increased metabolic rate, but a decline in ATP production

Can be fatal, liver failure

lipid soluble picked up proton and diffuse to other side.

UNCOUPLER - collapse protein gradient

44
Q

why was DNP effective for weight loss

A

not generated from carbohydrate metabolism,
get from fat (energy)

45
Q

How did DNP cause hyperthremia

A

(rapid increase in body temp)

energy was released as heat (what not used)

46
Q

Symporter cooperative binding

A

because ion gradient, favorable for Na to bind, promoting glucose to bind (what drives glucose against gradient) - called cooperative binding

47
Q

Symporter occluded

A

not open to either side
either completely empty or full

48
Q

Symporter steps

A

secondary active transport

49
Q

___ facilitates the uptake of nutrients (in intestinal epithelial cells)

A

Asymmetric distribution of Transporters in plasma membrane

50
Q

Transcellular Transport in Intestinal Epithelial Cells

A

intestinal lumen (atypical domain) - Na driven glucose symport (Na in and glucose into cell)

extracellular fluid (basal domain) - facilitate diffusion (no energy requirement) - carrier protein mediating

Na out- keeps gradient going (Na+K+ pump)

51
Q

structural polarity in Transcellular Transport in Intestinal Epithelial Cells

A

two sides are different - distribution of transporters

Cell Biology Exam 2 (6 decks)

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