Lecture 3: Transporters and Pumps Flashcards

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1
Q

What is selective permeability?

A

It is the ability of the membrane to differentiate between different types of molecules, allowing some molecules while blocking others

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2
Q

List the types of molecules & if they are able to pass through the membrane

A

Pass: Hydrophobic molecules, small uncharged polar molecules
May pass or not: Large uncharged polar molecules
Will not pass: Ions

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3
Q

What is GDS?

A

GLUT1 Deficiency Syndrome

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4
Q

Name the mechanism of GDS

A

it is a genetic disorder that impairs brain metabolism. specifically, the brain is not supplied with sufficient glucose

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5
Q

Name symptoms of GDS

A

symptoms include: seizures, developmental delay, motor disorders

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6
Q

What is treatment of GDS?

A

ketogenic (high fat) diet

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7
Q

What does GLUT1 facilitate?

A

Facilitates the transport of glucose across the membranes of mammalian cells

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8
Q

T/F: GLUT1 is a uniporter

A

True

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9
Q

What does a uniporter do?

A

It has one or more specific binding sites for a solute (substrate), and will transport it across the membrane in a clothes pin fashion (if that makes sense)

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10
Q

The binding of solute induces a irreversible conformational
change in the transporter, GLUT1

(this is also specific to uniporters)

A

False, induces a reversible change

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11
Q

For a uniport, how is the direction of transport inversed?

A

Direction of transport is inversed if the direction of the

concentration gradient is changed

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12
Q

What is protein conformation determined by?

2 things

A
  1. Amino acid sequence of the protein

2. Interactions between individual amino acids

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13
Q

What bonds are involved in protein conformational change?

A

Via hydrogen bonds, salt bridges, disulfide bonds,

hydrophobic interactions

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14
Q

Name three ways that conformational changes are induced?

3 things

A
  1. binding of a ligand
  2. posttranslational modification of the protein
  3. change in the pH, voltage or temperature
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15
Q

Transporter-mediated transport reaches

a maximal transport rate known as ____.

A

Vmax

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16
Q

What does Vmax indicate?

A

each transporter in a cell is working at its maximal rate, ie. all binding sites are filled (which requires a steep concentration/electrochemical gradient)

17
Q

What does Km measure?

A

measures the affinity of the transporter for the solute

18
Q

Name the 3 distinct transport systems in a biological membrane

A
  1. Transporters (uniporter)
  2. ATP - powered pumps
  3. Ion channels
19
Q

Name an example of each of the three transport systems

A
  1. transporters-GLUT1, Na+/Glc
  2. ATP powered pumps- Na+/K+
  3. Ion Channels- SCN1A - Nav1.1
20
Q

How can we experimentally test if a mutation in GLUT1 affects glucose transport?

Problem: GLUT1 is a transmembrane protein - how can it be removed from the membrane?

A

We need to isolate wt. and mutant GLUT1 and examine ability to transport glucose into a liposome

  1. Extract protein from membrane
  2. Reconstitute into liposomes
  3. Perform functional activity assays
21
Q

T/F: Passive transport does not require direct energy input

A

True

22
Q

Define the energy standpoint of active transport

A

AT is an energy-dependent transport against an electrochemical gradient

23
Q

How exactly does energy input assist with transport?

A

Electrochemical gradient for one molecule drives transport of the other

eg, ATP

24
Q

Name the 3 types of ATP Driven Pumps

A
  1. P-type pump
  2. ABC transporter
  3. V-type proton pump
25
Q

What types of molecules does P-type pump move?

A

ions; H+, K+, Na+, Ca2+

26
Q

What types of molecules does ABC transporter move across?

A

small molecules

27
Q

What does V-type proton pumps move across?

A

H+

28
Q

P-type pumps transport molecules ____ their electrochemical gradient

A

against

29
Q

Name the most famous type of Ptype pumps?

A

Na+/K+ pump
Na+: low inside, high outside
K+: high inside, low outside

30
Q

What is the result of the Na+/K+ pump?

A

Transport of 3 Na+ out of the cell, and 2 K+ into the cell/ATP

31
Q

T/F: Transporters (carriers such as GLUT1) are highly specific for molecule to be transported, and are insaturable

A

False; they are saturable

32
Q

Active (____ or___) and passive (______) transport is possible

A
  1. sym
  2. or anti-porter
  3. uniporter
33
Q

With regards to pumps/ATPases, energy from ATP hydrolysis is converted into ___________ ______ , such as ion transport against their electrochemical gradient

A

mechanical work

34
Q

T/F: Transport down the electrochemical gradient is passive and does not require energy

A

True

35
Q

Transport against the electrochemical gradient requires energy
• _____ ________ (Na+/K+ pump), light-driven)
• “_____ ______” (sym- and antiport) taking advantage of the steep electrochemical gradient of other molecules

A
  1. ATP Hydrolysis

2. Ride Along

36
Q
  1. Which of the following statements is most correct for an ion transporter?
    A. It contains a selectivity filter
    B. It transports ions only down their electrochemical gradient
    C. It contains specific binding sites for the ion to be transported
    D. It transports ions faster than ion channels
    E. It contains 3 transmembrane domains
A

C?

37
Q

What do you conclude from this experiment?
You are measuring Glc uptake into liposomes into which you have reconstituted wt or mutant forms of GLUT1
a.) The mutation increases the number of Glc binding sites
b.) the mutation increases the affinity of the Glc binding sites
c.) The mutation decreases the affinity of the Glc binding sites
c.) The mutation has no effect on Glc transport
d.) The mutation blocks Glc transport

A

C

38
Q

CFTR is a protein with 12 transmembrane domains that is mutated in many cystic fibrosis patients. Its molecular analysis led
to some surprises. CFTR is homologous to a transporter of the family of ABC transporters, which use ATP hydrolysis to pump
solutes in or out of the cell. However, CFTR shows an unusual behavior. Which of the following statements would suggest that
CFTR functions differently from the ABC transporter family?
A: CFTR binds to Cl- to move the ions across membranes
B: CFTR can move Cl- against a concentration gradient
C: CFTR produces a robust Cl- current across membranes
D: CFTR requires ATP to move Cl- across membranes

A

A?