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AS BIOLOGY > 3 - Cell Membranes and Transport > Flashcards

3 - Cell Membranes and Transport Flashcards

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1
Q

What are the 2 types of endocytosis?

A

Phagocytosis and pinocytosis

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2
Q

What is phagocytosis?

A

The process where the cell obtains solid materials that are too large to enter by diffusion or active transport

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3
Q

What is pinocytosis?

A

The entry of liquid into the cell by the same mechanism as phagocytosis except that the vesicles are smaller

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4
Q

What is exocytosis?

A

The exit of substances from the cell after being transported through the cytoplasm in a vesicle

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5
Q

What is the definition of water potential?

A

The tendency of free water molecules to move into/out of a system/cell

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6
Q

What is the definition of osmosis?

A

The movement of water from an area of high water potential to an area of low water potential down a water potential gradient, across a partially permeable membrane

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7
Q

What is water potential measured in?

A

Kilopascals (kPa)

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8
Q

What are hypertonic solutions?

A

Solutions with a lower WP and higher concentration of solutes than the cell cytoplasm

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9
Q

What are isotonic solutions?

A

Solutions with the same WP and concentration of solutes as the cell cytoplasm

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10
Q

What are hypotonic solutions?

A

Solutions with a higher WP and lower concentration of solutes than the cell cytoplasm

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11
Q

What is the affect of hypotonic solutions on animal cells?

A

~ Cell undergoes lysis and bursts

~ The WP of the solution is higher than the cell so water moves into the cell down a WP gradient by osmosis

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12
Q

What is the affect of hypertonic solutions on animal cells?

A

~ Cell crenates and shrivels up

~ The WP of the cell is higher than the solution. Water moves out of the cell down a WP gradient by osmosis

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13
Q

What is incipient plasmolysis of a tissue?

A

~ When 50% of cells are plasmolysed and 50% are turgid

~ The solution is isotonic to the tissue and would therefore have the same WP

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14
Q

Why do cells react differently in incipient plasmolysis?

A

Because each cells cytoplasm would have a different solute concentration and therefore different WP

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15
Q

What are the 4 methods of transport through the cell membrane?

A

Diffusion
Facilitated diffusion
Active transport
Osmosis

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16
Q

What is the definition of diffusion?

A

Movement of molecules from an area of high conc to an area of low conc down a conc gradient

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17
Q

What is the definition of facilitated diffusion?

A

Movement of molecules from an area of high conc to an area of low conc down a conc gradient via a channel / carrier protein

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18
Q

What is the definition of active transport?

A

Movement of molecules from an area of low conc to an area of high conc against a conc gradient, using energy made from the hydrolysis of ATP

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19
Q

What is the definition of osmosis?

A

Movement of water from an area of high WP to an area of low WP down a WP gradient across a semi-permeable membrane

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20
Q

What molecules use diffusion to pass through the cell membrane?

A

~ Non polar molecules e.g O2 and CO2

~ Lipid soluble/based molecules e.g steroids and lipid soluble vitamins

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21
Q

What molecules use facilitated diffusion to pass through the cell membrane?

A

~ Small polar molecules e.g ions (via channel protein)

~ Large polar molecules e.g amino acids, glucose

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22
Q

What molecules use active transport to pass through the cell membrane?

A

Anything polar (charged) e.g ions, amino acids, glucose

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23
Q

What molecules use osmosis to pass through the cell membrane?

A

Water ONLY

24
Q

What area of the membrane is diffusion used?

A

Phospholipid bilayer

25
Q

What area of the membrane is facilitated diffusion used?

A

Channel and carrier proteins

26
Q

What area of the membrane is active transport used?

A

Carrier proteins

27
Q

What area of the membrane is osmosis used?

A

~ Aquaporin (specific type of hydrophilic channel protein)

~ A small volume can move through the phospholipid bilayer

28
Q

How do carrier proteins allow molecules to enter the membrane?

A

~ Gated carrier protein prevents molecules from facilitated diffusing out of the cell
~ Molecule enters the protein and ATP is used to change the shape of the protein. Molecule enters cell
~ Protein flips back to start shape

29
Q

What energy is required for diffusion, facilitated diffusion and osmosis?

A

Kinetic energy of molecules

30
Q

What energy is required for active transport?

A

Energy from ATP from aerobic respiration (cells will have lots of mitochondria)

31
Q

What is the rate of diffusion affected by?

A 
~ Concentration gradient
~ Diffusion distance across cell
~ S.A of membrane
~ Temperature
~ Size of molecule
~ Lipid solubility
32
Q

What is the rate of facilitated diffusion affected by?

A

~ Concentration gradient
~ Temperature
~ Number of specific proteins (channel + carrier) in the membrane

33
Q

What is the rate of active transport affected by?

A

Number of specific carrier proteins

34
Q

What can stop active transport through the membrane?

A

The addition of potassium cyanide, a respiratory inhibitor

35
Q

What is the rate of osmosis affected by?

A

~ Concentration gradient
~ Temperature
~ Number of aquaporins in the membrane

36
Q

How wide is the phospholipid bilayer?

A

7-8nm

37
Q

What does the fluid mosaic model of membranes have?

A

~ Phospholipid bilayer
~ Intrinsic proteins (span the bilayer)
~ Extrinsic proteins (on one side of the bilayer)

38
Q

Why is the cell membrane model called the fluid mosaic model?

A

~ Fluid because the phospholipids and proteins move around each other
~ Mosaic because proteins are arranged between the phospholipids

39
Q

What are phospholipids a barrier to?

A

~ Water soluble molecules

~ Ions and polar molecules

40
Q

What do phospholipids allow the diffusion of?

A

~ Small non-polar molecules e.g O2 and CO2

~ Lipid soluble/based molecules e.g steroids / lipid soluble vitamins

41
Q

What structure are extrinsic proteins in?

A

Tertiary structure

42
Q

What is the function of extrinsic proteins?

A

Receptor for cell signalling e.g insulin

43
Q

What are the 2 types of channel proteins?

A

~ Hydrophilic pore

~ Aquaporin

44
Q

What do channel proteins transport?

A

Small polar molecules (water soluble) e.g ions by facilitated diffusion, water by osmosis

45
Q

What do carrier proteins transport?

A

Large polar molecules e.g glucose and amino acids

46
Q

What is the function of cholesterol in the cell membrane?

A

Provides the membrane with stability and fluidity by fitting between the fatty acid tails

47
Q

What are polysaccharides that are attached to a protein called?

A

Glycoprotein

48
Q

What are polysaccharides that are attached to a lipid called?

A

Glycolipid

49
Q

What is the function of glycoproteins / glycolipids?

A

~ Cell to cell communication

~ They act as an antigen for cell recognition

50
Q

Why can’t ions and molecules such as glucose pass through the cell membrane by diffusion rather than FD?

A

As they are relatively insoluble in the phopholipid bilayer

51
Q

What do intrinsic proteins do?

A
  • Some transport water-soluble substances

- Some allow active transport of ions across, by forming channels

52
Q

What is co-transport?

A

A type of facilitated diffusion that brings molecules and ions into cells together on the same transport protein molecule

53
Q

What does it mean when a plant cell is turgid?

A

It is holding as much water as possible. Further entry of water is prevented as the cell wall can’t expand further

54
Q

What is the pressure potential? (Yp)

A
  • The pressure exerted by the cell contents on the cell wall

- Always +ve

55
Q

What is the solute potential? (Ys)

A

A measure of the osmotic strength of a solution

56
Q

What do both endocytosis and exocytosis require and why?

A

ATP. as the membrane has to change shape for these processes which requires energy

AS BIOLOGY (13 decks)

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