transport across cell membranes Flashcards

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1
Q

function of the cell membrane

A

controls which substances pass into + out of cell

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2
Q

3 functions of internal membranes

A

compartmentalisation
site for biochemical reactions
controls which substances pass into and out of organelles

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3
Q

5 main molecular components of a membrane

A

phospholipids
proteins
glycoproteins
glycolipids
cholesterol

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4
Q

3 functions of phospholipids

A

allow lipid soluble substances to enter and leave cell
prevent water soluble substances entering or leaving cell
makes membrane flexible and self sealing

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5
Q

2 functions of extrinsic proteins

A

provide mechanical support/adhesion
act as receptors for molecules

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6
Q

2 functions of intrinsic proteins

A

form protein channels
form carrier proteins

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7
Q

3 functions of cholesterol

A

reduces lateral movement of molecules
makes the membrane less fluid
prevents leakage from cell

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8
Q

3 functions of glycolipids

A

act as recognition site
helps maintain membrane stability
helps attach cells together to form tissues

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9
Q

3 functions of glycoproteins

A

act as recognition sites
help cells attach to each other to form tissues
used in cell recognition

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10
Q

define diffusion

A

the net movement of molecules or ions from a region of high concentration to an area of low concentration, until at equilibrium.

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11
Q

3 factors affecting rate of diffusion

A

surface area
difference in concentration
thickness of membrane

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12
Q

define osmosis

A

the passage of water molecules from a solution of high water potential to a solution of low water potential through a selectively permeable membrane.

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13
Q

define hypotonic

A

less concentrated

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14
Q

define hypertonic

A

more concentrated

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15
Q

define isotonic

A

at equilibrium

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16
Q

define water potential

A

the pressure created by water molecules trying to diffuse out of a solution down a gradient from a higher water potential to a lower water potential.

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17
Q

what has high water potential

A

a dilute solution as it has many free water molecules so water is more likely to move

18
Q

what is the water potential to f pure water

A

0

19
Q

what is a protoplast

A

the entire cell is excluding the cell wall

20
Q

what is incipient plasmolysis

A

the point where plasmolysis takes place and half the cells are plasmolysed, half are not

21
Q

what happens when an animal cell is in a solution of high water potential

A

cell bursts open

22
Q

what happens when animal cell is in a solution of low water potential

A

cell shrinks and shrivels

23
Q

what happens when a plant cell is in a solution of high water potential

A

protoplast is pushed tight against cell wall

24
Q

what happens when a plant cell is in a solution with low water potential

A

protoplast shrinks away from cell wall
(plasmolysed)

25
Q

what particles does a channel protein transport

A

small charges substances (usually ions)

26
Q

what do channel proteins form

A

water filled pores lined with polar groups (so hydrophilic)

27
Q

how do cells use channel proteins to control entry and exit

A

most channels are gated

28
Q

what do carrier proteins transport

A

larger molecules such as glucose and amino acids are taken across

29
Q

how does a carrier protein work

A

is able to bind with a specific shaped molecule
the carrier changes shape to release the molecules the other side of the membrane

30
Q

define active transport

A

the movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins.

31
Q

4 ways that active transport differs from passive transport

A

requires energy in the form of ATP
goes against the concentration gradient
only uses carrier proteins
process is very selective

32
Q

what is co transport

A

where 2 substances are simultaneously transported across a membrane by 1 protein

33
Q

define symport

A

2 molecules moved together from one area to another

34
Q

define anti port

A

1 substance going in one direction, 1 in another

35
Q

example of anti port

A

sodium potassium pump

36
Q

2 adaptations of the ileum absorption

A
  • large surface area for co transport proteins to fit on the membrane
  • lots of mitochondria to produce ATP to provide energy for absorption
37
Q

what is cotransported in the ileum

A

glucose molecules with sodium ions

38
Q

what happens during co transport in the ileum

A

Na+ diffuses down the concentration gradient into the epithelial cell. This pulls glucose molecules into the epithelial cell against the concentration gradient.
To maintain a low Na+ concentration inside cells Na+ pumped into blood using sodium potassium pumps.
Glucose moves into blood down the concentration gradient by facilitated diffusion.

39
Q

what does the sodium potassium pump require

A

ATP

40
Q

does the sodium potassium pump go with or against concentration gradient

A

both potassium and sodium go against their concentration gradient

41
Q

what direction does potassium go in the pump

A

into the cell from the blood

42
Q

which direction does sodium go in the pump

A

goes from the cell into the blood