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Molecules to Medicine > Cell Surface > Flashcards

Cell Surface Flashcards

1
Q

What are the functions of the cell surface membrane

A
  • Barrier between the cell and its environment
  • Maintaining different intracellular and extracellular environments
  • Site of chemical reaction
  • Protect vital components
  • Allow cell communication
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2
Q

What are the predominant phospholipids in biological membranes

A
  • phosphatidylcholine
  • phosphatidylserine
  • phosphatidylethanolamine
  • sphingomyelin
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3
Q

What effect does cholesterol have on the fluidity of the membrane and how does it do this

A
  • Makes the membrane less fluid and more rigid.
  • Intercalates between the phospholipids, a tighter packed bilayer
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4
Q

What 3 processes does the fluidity of biological membranes allow

A
  • Signalling - lipids and membrane proteins are able to diffuse rapidly to interact.
  • Ensure membranes are shared equally between daughter cells
  • Allows membranes to fuse together (endo and exocytosis)
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5
Q

What do transmembrane regions of integral proteins contain and what is their significance

A
  • Mainly contain hydrophobic amino acids.
  • These amino acids interact with phospholipid tails
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6
Q

What are the 6 functions of membrane proteins

A
  • Transport
  • Catalysis (enzymes)
  • Signal transduction
  • Cell recognition
  • Intercellular joining
  • Attachment (to cytoskeleton or intracellular matrix)
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7
Q

List the 4 Intracellular signal transduction lipids

A
  • Phosphatidylinositol
  • Diacylglycerol
  • Ceramide
  • Sphingosine-1-phosphate
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8
Q

Where do Intracellular signal transduction lipids come from and what proportion of phospholipids do they make up

A
  • Derived from lipids in the plasma membrane.
  • Minor proportion of phospholipid content
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9
Q

Give some features of Intracellular signal transduction lipids due to their specificity

A
  • Rapidly generated and destroyed by enzymes
  • Spatially and temporally generated depending on when and where they are needed
  • Bind to specific regions
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10
Q

What drives passive transport across biological membranes

A
  • Concentration gradients
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11
Q

What is the difference between facilitated and simple diffusion

A
  • Facilitated involves membrane proteins, simple does not
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12
Q

What 3 factors affect the ability of a solute to cross the membrane in simple diffusion

A
  • Hydrophobicity
  • Size - Large uncharged polar molecules cannot pass through whereas smaller ones can
  • Charged - Ions are too polar to pass through
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13
Q

What are the 2 classes of proteins involved in facilitated diffusion

A
  • Channel proteins-
  • Uniporter carrier proteins
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14
Q

What factors do channel proteins discriminate based on

A
  • Size
  • Charge
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15
Q

What are channels (proteins)

A
  • Hydrophilic pores through the membrane
  • Non-directional ion channels
  • Gated channels (more control than simple pore)
  • Fast
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16
Q

What factors do uniporter proteins discriminate based on

A
  • Solute must be complimentary to the binding site. Highly selective
17
Q

How do uniporter carrier proteins work

A

-Substrate binds and induces conformational shape change.
- The shape change moves the substrate across membrane and releases into the cell
- Slow

18
Q

Why do cells maintain electrochemical gradients

A
  • Drive transport across membranes
  • Maintains osmotic balance
  • Electrical forces inside and outside the cell must be balanced)
19
Q

Why is ATP required in active transport

A
  • Solutes are moved against their electrochemical gradients, this requires energy
20
Q

What are the 3 ways that active transport occurs

A
  • ATP- driven pumps - Couples hydrolysis of ATP with the transport of solute
  • Coupled transporters - Couples movement of a solute with the concentration with the movement of a solute against it
  • Light-driven pumps - Couples transport of solute against gradient with the input of energy from light
21
Q

What are the 2 types of ATP- driven pumps active transport

A
  • Symport- When both solutes move in the same direction
  • Antiport - When the solutes move in opposite directions
22
Q

Describe the Na+ and K+ example of ATP driven active transport

A
  • 3Na+ moves out of the cell while 2K+ moves in
  • Na+ binds to the catalytic unit to activate ATPase, and hydrolysis of ATPase causes a conformational change
  • Na+ is released out of the cell and K+ bind extracellularly, dephosphorylation of the subunit causes conformational change.
  • K+ released into the cell
23
Q

Describe the Na+/ glucose example of symporter active transport

A
  • Na+ is in high concentration inside the gut whereas glucose concentration is low.
  • Binding of glucose is dependent on the binding of Na+
  • Glucose becomes more likely to bind to symporter as concentration of Na+ is higher outside the cell
24
Q

Describe the Na+/ Ca2+ example of antiporter active transport (CARDIAC)

A
  • Concentration of Na+ and Ca2+ outside the cell is higher
  • Antiporter moves 3Na+ outside the cell (along its gradient), for every 1Ca2+ out (against its gradient).

Molecules to Medicine (6 decks)

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