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AQA A level Biology > Transport Across Cell Membranes > Flashcards

Transport Across Cell Membranes Flashcards

1
Q

Fluid Mosaic model of membrane structure

A

Molecules within member and can move laterally (fluid) e.g. phospholipids

Mixture of phospholipids, proteins, glycoproteins and glycolipids

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2
Q

Phospholipid bilayer components

A

Hydrophilic phosphate heads - attracted to water (orientate to aqueous environment either side of membrane

Hydrophobic fatty acid tails - repel water (orientate to interior of membrane)

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3
Q

Embedded proteins (intrinsic or extrinsic)

A

Channel and carrier proteins (intrinsic)

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4
Q

Glycolipids

Glycoproteins

A

Glycolipid - (lipids with polysaccharide chain attached)

Glycoproteins - (proteins with polysaccharide chain attached)

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5
Q

Cholesterol

A

Binds to phospholipid hydrophobic fatty acid tails

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6
Q

Components of the cell membrane (4)

A

Phospholipid bilayer

Inverted proteins

Glycoproteins and glycolipids

Cholesterol

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7
Q

What does the fluid Mosaic model of membrane structure explain?

A

How molecules can enter and leave a cell

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8
Q

How does the phospholipid bilayer allow molecules to enter or leave a cell?

A

Allows simple diffusion of nonpolar small/lipid soluble molecules (e.g. water oxygen)

Restricts movement of larger/polar molecules

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9
Q

How do you channel proteins allow molecules to enter or leave a cell?

A

Allow movement of water soluble/polar molecules/ions down a concentration gradient (facilitated diffusion)

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10
Q

How do you carrier proteins allow molecules to enter or leave a cell?

A

Allow the movement of molecules against a concentration gradient using ATP (active transport)

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11
Q

Features of the plasma membrane that adapt for its other functions (4)

A

Phospholipid bilayer

Phospholipid bilayer is fluid

Surface proteins

Cholesterol

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12
Q

How does the cell membrane being a phospholipid bilayer adapt for another function?

A

Maintains a different environment on each side of the cell (compartmentalisation of the cell)

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13
Q

How does the phospholipid bilayer being fluid adapt it for another function?

A

Can bend into different shapes for phagocytosis/to form vesicles

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14
Q

How do the surface proteins (extrinsic glycoproteins/glycolipids) adapt the cell membrane for another function?

A

Cell recognition

Act as antigens/receptors

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15
Q

How does cholesterol adapt the phospholipid bilayer for another function?

A

Regulates fluidity

Increases stability

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16
Q

What is cholesterol not present in?

A

Bacterial cell membranes

17
Q

What is the role of cholesterol?

A

Makes the membrane more rigid/stable/less flexible

By restricting lateral movement of molecules making up the membrane (e.g. phospholipids)

Binds to fatty acid tails of phospholipids causing them to pack more closely together

18
Q

Simple diffusion across the membrane

A

Net movement of small, nonpolar molecules (e.g. oxygen and carbon dioxide) across a selectively permeable membrane comment down a concentration gradient

Passive, no ATP required

19
Q

Factors affecting rate of simple diffusion

SCD

A

Surface area

Concentration gradient

Diffusion distance (thickness of surface)

20
Q

Facilitated diffusion across cell membranes

A

Net movement of larger/polar molecules (e.g. glucose) across a selectively permeable membrane, down a concentration gradient

Through a channel or carrier protein

Passive, no ATP required

21
Q

Factors affecting rate of facilitated diffusion

A

Surface area

Concentration gradient (until the number of proteins is the limiting factor as all are and use/saturated)

Number of channel or carrier proteins

22
Q

Carrier proteins transport…

A

Transport large molecules, protein changes shape when the molecule attaches

23
Q

Channel proteins transport…

A

Large/polar molecules through its pore

Some are gates (open and close) eg. Voltage gated sodium ion channels

24
Q

Specificity associated with channel and carrier proteins

A

Different carrier on channel proteins facilitate the diffusion of different specific molecules

25
Q

Active transport across cell membranes

A

Net movement of molecules/ions against a concentration gradient

Using carrier proteins

Using energy from the hydrolysis of ATP to change the shape of the tertiary structure and push the substances through

26
Q

Factors affecting the rate of active transport

A

PH, Temperature (affect tertiary structure of carrier protein)

Speed of carrier protein

Number of carrier proteins

Rate of respiration (affects ATP production)

27
Q

Classic example of co-transport

A

Absorption of sodium ions and glucose by cells lining the mammalian ileum

28
Q

Explain the cotransport of sodium ions and glucose

A
  1. Sodium ions are actively transported out of epithelial cells lining the ileum, into the blood, by the sodium potassium pump. Creating a concentration gradient of sodium (high concentration of sodium in lumen than epithelial cell)
  2. Sodium ions and glucose move by facilitated diffusion into the epithelial cell from the lumen, via a co-transporter protein
  3. Creating a concentration gradient of glucose – high concentration of glucose in epithelial cell then blood
  4. Glucose moves out of the cell into the blood by facilitated diffusion through a protein channel
29
Q

Movement across membranes by osmosis

A

Net movement of water molecules across a selectively permeable membrane down in water potential gradient

Passive

30
Q

Factors affecting rate of osmosis

A

Surface area

Water potential gradient

Thickness of exchange surface (diffusion distance)

31
Q

How much cells be adapted for transport across that internal or external membranes?

A

Increase in surface Sarah

Increase the number of channel proteins or carrier proteins

32
Q

Water potential

A

Potential of water molecules to diffuse out of or into a solution

Pure water has highest water potential

Adding solutes to a solution low as water potential (becomes more negative)

AQA A level Biology (36 decks)

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