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FLC > Membrane Function > Flashcards

Membrane Function Flashcards

1
Q

What is the major function of the plasma membrane?

A

Acts as a barrier
Transport
Signal Transduction

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2
Q

Which functional proteins are present at the lysosomal membrane ?

A

Hydrolytic enzymes

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3
Q

Which molecules are able to pass through the membranes passively?

A

Lipid soluble molecules
Hydrophobic molecules - N2, O2 etc.
Small uncharged polar molecules - H20, Urea, glycerol, CO2

these can all move either way through the membrane

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4
Q

What are the functions of the mitochondrial membranes?

A

Inner membrane
- Energy transduction

Outer membrane
- Acts as a barrier

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5
Q

What is Co transport?

A

The transport of 2 molecules simultaneously by one protein

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6
Q

What is the advantage of carrier mediated diffusion ?

A

Carrier mediated facilitated diffusion is more efficient than simple facilitated diffusion

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7
Q

What parallels can be drawn between enzyme kinetics and membrane transports?

A
  • Saturable - both have a maximum no. of molecules/substrate that are carried at a given time
  • Specificity - Transporters/enzymes are specific to their substrate/molecule
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8
Q

What are the 2 types of membrane transport?

A
  1. Passive

2. Active

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9
Q

What occurs at the peroxisomal membranes?

A

Fatty acid oxidation

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10
Q

What is Kt (AKA Km)?

A

The measure of affinity for transport of a transporters substrate

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11
Q

What are carrier mediated uniports?

A

Integral membrane proteins that transport a Single type of molecule across a cell membrane

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12
Q

How permeable are the membranes in the body?

A

Partially permeable

- certain molecules are able to pass through

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13
Q

What is an antiporter?

A

A co transporter integral membrane protein that transports 2 molecules in opposite directions

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14
Q

What does the GLUT2 transporter regulate in the pancreatic Β cells?

A

Regulates insulin levels

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15
Q

What is active membrane transport?

A

Transport requiring energy (ATP)

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16
Q

Why is blood glucose not taken up by the liver at low [glucose]?

A

Other organs require glucose at lower concentrations e.g. brain (always requires glucose)

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17
Q

Where is the GLUT4 transporter located in the body?

A

Muscle and fat cells

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18
Q

Describe the structural features of a glucose transporter

A
  • large molecule
  • amino terminus
  • carboxyl terminus
  • 12 transporter domains (can vary)
  • N linked glycosylation
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19
Q

What molecule does the GLUT5 transporter carry?

A

Fructose

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20
Q

What is passive transport?

A

All non mediated processes
small no. of molecules pass through pores
driven by concentration gradient

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21
Q

How can no. of GLUT4 receptors in muscles be increased?

A

Through endurance training, no. of GLUT4 receptors in the plasma membrane can increase

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22
Q

What does a low Kt mean for glucose transporters?

A

Glucose transporters are saturated at a low [glucose]

  • has a high affinity
  • active at low [glucose]
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23
Q

Which two glucose receptors are found in all mammalian tissues?

A

GLUT1 and GLUT3 involved in basal glucose uptake

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24
Q

What are the major functions of the various types of endoplasmic reticulum membranes?

A

RER
- Translation protein processing

SER
- Complex lipid synthesis

25
Q

How do large uncharged polar molecules pass through the membrane?

A

e.g. Glucose

movement of these molecules depends on their concentration

26
Q

What is the function of the nuclear membrane ?

A

Chromatin attachment

27
Q

What Kt value do the brains glucose transporters have?

A

Low Kt values for glucose transporters in brain
- high affinity
Therefore brains energy needs always met

28
Q

What type of transport is carried out by carrier mediated uniports?

A

Passive as still driven by concentration gradients

29
Q

What is meant by a symporter?

A

Integral membrane protein involved in the co transport of molecules in the same direction

30
Q

What is membrane function dependent on?

A

The membranes structure

31
Q

What is a similarity between facilitative diffusion and active transport?

A

Both are selective and require integral membrane proteins

32
Q

How is the concentration gradient of glucose maintained?

A

Glucose phosphorylated to G6P when it enters cell
There are no G6P transporters in cells
- G6P can’t leave cell
- [Glucose] always higher outside cell - eqb. never reached

33
Q

Give an example of co transport in the body?

A

Glucose absorption by epithelial cells

34
Q

Which transport process is required for continuous transport?

A

Both active and passive are required for continuous transport across cell membranes

35
Q

Where is GLUT5 transporter found?

A

In the small intestine

36
Q

What functions does the golgi membrane stacks carry out?

A

Post translational modifications occur on the Golgi membrane
processing for secretions into the secretory pathway

37
Q

How are ions able to move through the membrane?

A

By simple diffusion from a high to low concentration

38
Q

What is foxglove digitalis?

A

Is a genus of herbacus (plant) used to produce transport inhibiting drugs
Known as cardiotonic steroids

39
Q

What is the function of the GLUT2 receptor in the liver?

A

Removes excess glucose from blood

40
Q

Name the 5 different glucose transporters and their transport affinities (Kt)

A 
GLUT1 - 1mM 
GLUT2 - 15-20mM 
GLUT3 - 1mM 
GLUT4 - 5mM 
GLUT5 - N/A
41
Q

What is the major function of the liver?

A

Regulating blood glucose levels

42
Q

What happens to excess blood glucose in the body?

A

Taken up by Liver

43
Q

What is the role of Digitalis?

A

Specifically inhibits the Na+/K+ pump

44
Q

Where are GLUT2 transporters found in the body?

A

Located in liver and pancreatic Β cells

45
Q

Explain how the co transport of glucose and Na+ occurs in the epithelial cells in the gut.

A
  1. High [Na+] outside epithelial cells
  2. Na+ diffuse in to cell taking glucose in by co transport through SGLUT1 and SGLUT2 receptors
    • Glucose taken in against conc. gradient
  3. Glucose passes into blood by facilitated diffusion
  4. Na+ enters blood by active transport using ATP
  5. Na+ exchanged for
46
Q

Why is energy required for active transport?

A

Energy required as molecules are pumped against their concentration gradient
[low} -> [high]

47
Q

How are proteins targeted specifically to organelles?

A

Proteins have specific signal sequences targeting them to specific organelles

48
Q

How does the Digitalis antiport system function to inhibit Na+/K+ pump?

A

Na+ is pumped out and Ca2+ is pumped in

49
Q

Explain how re-hydration therapy works?

A

Targets co transport for glucose and sodium to treat diarrhoea

50
Q

How can glucose uptake be increased?

A

Increasing number of glucose transporters

Increasing insulin

51
Q

How is digitalis used to treat heart conditions?

A

Digitalis increases force of contraction of the heart

  • Na+/K+ pump inhibition leads to increased Na+
  • slower Ca2+ removal by Na+/Ca2+ pump
  • increased contraction
52
Q

What is the significance of compartmentalisation?

A
  • Separates reactions
  • Enables regulation of local environments
  • Brings reactants together
53
Q

What are the key features of glucose transport?

A
  • carrier mediated
  • different tissues have different glucose transporters
  • transport depends on cell type
54
Q

How is cystic fibrosis caused?

A

Mutation of CFTR gene causes faulty Cl- channel
Build up of Cl- causes increase in water absorption in blood
Mucus in airways becomes thicker

55
Q

What is Digitalis used to treat?

A

Congestive Heart disease since 1780s

56
Q

Explain how the glucose transporter is able to carry glucose across the membrane

A
  1. Glucose binds to transporter
  2. Conformational changes occur
  3. Results in transport across membrane down concentration gradient
  4. Bidirectional transport can occur
  5. Gradient maintained by phosphorylation
57
Q

How are plasma membranes able to respond to their environment?

A

They have receptors allowing interaction with the environment

58
Q

How are lysosomal enzymes targeted differently?

A

“Not targeted by their amino acid sequence

Targeted by the Mannose-6-Phosphate pathway instead

FLC (34 decks)

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