membrane transport active

Question 1

dual role of a lipid bilayer:

Answer 1

a 2-D liquid that allows lateral movement of proteins and lipids

a permeability brrier

Question 2

hydrophobic molecules that pass easily through a membrane

Answer 2

O₂

CO₂

N₂

steroid hormones

Question 3

small uncharged polar molecules (little permeability)

Answer 3

H₂O

urea

glycerol

NH₃

Question 4

large uncharged polar molecules (little permeability)

Answer 4

glucose

sucrose

Question 5

ions (no permeability)

Answer 5

H⁺ Na⁺

HCO₃^-

K⁺ Ca²⁺

Cl^- Mg²⁺

Question 6

methods to cross a membrane:

Passive transport:

Active transport:

• *

Answer 6

passive transport:

• no energy needed
• solute travels down concentration gradient

active transport:

• coupled to ATP hydrolysis
• solute travels against concentration gradient

Question 7

3 general modes of transport

Answer 7

antiporter: A and B in opposite direction
symporter: A and B in same direction
uniporter: moves only 1 particle but in both direction

Question 8

3 genera categories of transporters:

Answer 8

1. pumps: perform primary active transport
   
   1. a water pump fights gravity and actively pulls water to the house*
2. carriers: traverse the membrane without needing (extra) energy
   
   1. carrying a stowawy along for the ride* (2º active)
3. channels: are used in passive transport
   
   1. the channel opened and allowed your ship to float gently out of the gridlock from behind the dam

Question 9

characterstics of P-type pumps: P-Type ATPases

Answer 9

phosphorylates self

• transmembrane domain spans the lipid bilayer
• A/Actuator domain links the cytosolic domains to the transmembrane domain
• N/Nucleotide binding domain binds ATP
• P/Phosphorylation domain accepts the phosphate from ATP

Question 10

general mechanism for P-Type ATPases

Answer 10

1. E1 (open to cytosol) + bind moleculeA
2. bind and hydrolyze ATP = phosphorylate self
3. E2 (open to outside) + release moleculeA + bind moleculeB
4. reset to E1 + release moleculeB

Question 11

P-Type ATPase example: Ca²⁺

1. ____porter (Ca²⁺ movement ____ of cytosol)
2. name describes membrane crossed:
   
   1. ____ = sarcoplasmic/endoplasmic reticulum (in muscle cells)
   2. ____ = plasma membrane
   3. ____ = golgi (secretion pathway)
3. mechanism:
   
   1. E1 , 2 Ca²⁺ bound on ____ side
   2. ATP binds, Ca²⁺ ions ____
   3. ATP hydrolysis, self ____
   4. eversion to E2 , Ca²⁺ ions ____
   5. release of ____
   6. eversion to ____

Answer 11

1. uni
2. 1. SERCA
   2. PMCA
   3. SPCA
3. 1. cytosolic
   2. trapped
   3. phosphorylation
   4. released
   5. P_i
   6. E1

Question 12

P-Type ATPase example: Na/K pump

1. ____porter across cell membrane
2. role in cell
   
   1. ____ excitation in neurons and muscle cells
   2. ____ driving other active transports
3. mechanism
   
   1. E1, ____ ions bound, ATP bound
   2. Na⁺ ions are ____
   3. ATP hydrolysis, self ____
   4. eversion to E2, Na⁺ ions ____
   5. binding of ____
   6. K⁺ ions ____ , release of P_i, ATP rebinding
   7. eversion to ____
   8. release of ____

Answer 12

1. anti
2. 1. electrical
   2. gradient
3. 1. Na⁺
   2. trapped
   3. phosphorylation
   4. released
   5. K⁺
   6. trapped
   7. E1
   8. K⁺

Question 13

P-Type ATPases: flippases

1. ____ (flipping) motion within plasma membrane
   
   1. on cell membrane - internalize ____
   2. on golgi - recycle ____
2. phosphatidylserine (PS) is ____
   
   1. phospholipid ____
   2. activates ____ ____ ____
   3. essential for proper ____ function
   4. externzlized PS signals ____

Answer 13

1. transverse
   
   1. lipids
   2. endosome
2. internalized
   
   1. nutrient
   2. protein kinase C
   3. neuron function
   4. apoptosis

Question 14

other notabile families of P-type ATPases:

1. in plants and fungi, the Na/K pump is replaced by a plasma membrane ____
2. ____ in gastric cells maintain the pH of the stomach lumen
3. ____ ____ ____ maintain proper levels of trace metals while preventing toxicity

Answer 14

1. H+ ATPase
2. H⁺/K⁺ ATPase
3. heavy metal ATPases

Question 15

ABC transporters important features

Answer 15

2 transmembrane domains span the lipid bilayer

2 nucleotide binding domains bind ATP = ATP Binding Cassette

importers requires a substrate binding protein

can be a single protein or a dimer

Question 16

general mechanism of ABC transporters

Answer 16

1. bind molecule
2. bind ATP + dimerize ABCs
3. eversion
4. release of molecule/ATP/P_i + reset

Question 17

ABC transporters: example: MDR (multiple drug resistant) proteins

1. exporters of ____ , ____ , ____ ____ , and ____
2. expression is proportionate to ____ resistance of chemotherapy
   
   1. P-glycoprotin
   2. MDR-assocated protein 1
   3. ____ cancer resistance protein

Answer 17

1. lipids, sterols, foreign peptides, and toxin
2. tumor
   
   1. 2. 3. breast

Question 18

ABC transporters: CFTR example

1. ____ exporter
2. can bind ATP = sensor of cellular ____ content
3. ATP hydrolysis is ____ → acts like a ligand-gated channel
4. altered ion movement results in increased ____ pressure
5. increased osmotic pressure allows for secreted ____ to interact

Answer 18

1. Cl^-
2. nucleotide
3. inefficient
4. osmotic
5. mucins

Question 19

ABC transporters: peroxisomal ABC transporter example:

1. peroxisomes are involved in ____ ____ synthesis and breakdown, in particular for:
   
   1. very ____ chain fatty acids
   2. ____ salts
2. peroxisomal ABC transporters are all ____ , and therefor also called: half - ABC transporters

Answer 19

1. fatty acid
   
   1. long
   2. bile
2. homodimers

Question 20

other notable functions of ABC transporters:

• efflux of ____ into HDLs
• transport of ____
• ____ transport, including transport of Fe/S clusters
• ABC importers are primarly found in ____ , and never in ____

Answer 20

• cholesterol
• nucleotides
• Iron
• bacteria humans

Question 21

secondary active transport general mechanism

Answer 21

1. gradient of moleculeA made by primary active transport
2. release of molecule A gradient powers movement of moleculeB against its concentration gradient

Question 22

secondary active transport is considered active transport because

Answer 22

energy is used to establish a gradient and stowaway moves against its gradient

Question 23

all glucose transport is

Answer 23

passive

Question 24

secondary active transport: Na-glucose cotransport mechanism

Answer 24

1. primary active transport creates a gradient
2. passive channel or carrier allows ions/molecules to fall back down the gradient with a high value stowaway

Question 25

secondary active transport: Na⁺/Ca²⁺ exchanger:

1. primary active transport keeps:
   
   1. ____ and ____ out of the cell
   2. ____ inside the cell
2. Na/Ca exchanger releases ____ gradient to externalize even more ____

Answer 25

1. 1. Na⁺ and Ca²⁺
   2. K⁺
2. Na⁺ Ca²⁺

Question 26

secondary active transport:

1. another notable symport system:
   
   1. ____ ____ cotransport
   2. found in the ____ and ____
2. anther notable antiport system:
   
   1. ____ exchange
   2. found in the ____

Answer 26

1. 1. Na-amino acid
   2. intestines and kidneys
2. 1. Na+ - H+
   2. kidneys

Question 27

active transport in context:

1. digitalis and ouabain share a binding site in the transmembrane domain of the ____ pump
2. when the binding site is occupied by either molecule, the Na/K pump becomes locked in the ____ conformation
   
   1. this keeps ____ inside the cell
   2. excess Na+ is removed by exchanging with ____
   3. extra Ca²⁺ in cell makes heart ____

Answer 27

1. Na/K
2. E2
   
   1. Na+
   2. Ca²⁺
   3. contract