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Biology > Cell Membranes > Flashcards

Cell Membranes Flashcards

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1
Q

What does it mean by partially permeable

A

Allows some molecules to enter/exit but not all

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2
Q

Why is the phospholipid bilayer fluid mosaic

A

Phospholipids constantly moving
Cholesterol, transport and receptor proteins scattered through phospholipids
Some proteins can move sideways
Proteins to polysaccharides = glycoproteins
Lipids attached to lipid = glycolipids

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3
Q

Why does the bilayer not allow polar substances through

A

Polar molecules are water soluble

And the fatty acid tails are hydrophobic so repel water

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4
Q

What is the function of cholesterol in the cell membrane

A

Helps maintain shape of cells of animal cells without - especially red blood cells not supported by other cells

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5
Q

How does cholesterol work

A

Fits between phospholipids by binding to the fatty acid tails
Making phospholipids pack more closely together
Restricting the movement = more rigid

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6
Q

What is the permeability like at 0 and why

A

Highly permeable

Phospholipids don’t have much energy = packed closely together = rigid
Channel proteins and carrier proteins deform = allow anything through
Ice crystals pierce membrane leaving holes when it thaws

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7
Q

What is the permeability at 0-45 and why

A

Partially permeable

Phospholipids aren’t packed as close together
And have more energy so move more

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8
Q

What is the permeability like at 45+ and why

A

Highly permeable

Bilayer breaks down
Water inside cell expands putting p on memebran s
Channel and carrier proteins deform

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9
Q

Is facilitated diffusion passive

A

Yes

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10
Q

Why do large molecules need transport proteins

A

Too large

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11
Q

What type of protein do large molecules use

A

Carrier proteins

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12
Q

What type of protein do polar molecules use

A

Channel proteins

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13
Q

How do carrier proteins work

A
  1. Large molecule attatches
  2. Protein changes shape releasing the molecule on the other side
    Down conc grad
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14
Q

How do channel proteins work

A

Pores for charged particles of move through down conc grad

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15
Q

What are 3 factors affecting simple diffusion

A

Conc grad
Thickness of exchange surface
Surface area

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16
Q

How does conc grad affect simple diffusion

A

High cg = higher rate

As diffusion happens the cg decreases until uqm reached (both sides the same concentration) so diffusion slows over time

17
Q

How does thickness affect simple diffusion

A

Thin = rate increases

Shorter diffusion pathway

18
Q

How does sa affect simple diffusion

A

Increase sa = rate

More particles can be exchanged in the same amount of time

19
Q

How does microvilli increase rate of diffusion in small intestine

A

Microvilli = projections of plasma membrane folding up on itself
Increases sa

20
Q

What are 2 things that facilitated diffusion depend on

A

Conc grad

No of transport proteins

21
Q

How does no of transport proteins affect rate of facilitated diffusion

A

If all proteins are being used then no more can get through even in conc grad increases

22
Q

How has the kidney adapted for more facilitée diffusion

A

Lots of aquaporins (water channel proteins) to speed of water réabsorption

23
Q

If a solution has a high water potential what does that mean

A

High water conc

Low solute conc

24
Q

What 3 things does osomosis rats dépend on

A

Water potential gradient
Thickness of exchange surface
Surface area

25
Q

What proteins are used in active transport

A

Carrier

26
Q

What direction do molecules move in active transport

A

From low conc to high

27
Q

What does actual transport need

A

Energy (from atp hydrolysis)

28
Q

What is co transport

A

Bind to 2 molecules At once

Use the conc grad of one molecule to transport the other against theirs

29
Q

What 3 factors affect the rate of active transport

A

Speed of carrier proteins
Number of carrier proteins
Rate of respiration/availability of atp

30
Q

Why is co transport needed In the ileum

A

The conc of glucose is too low to diffuse down its conc grad by diffusion

Biology (13 decks)

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