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A-level Biology > Cell Membranes And Transport 1.3 > Flashcards

Cell Membranes And Transport 1.3 Flashcards

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1
Q

What is a phospholipid?

A

A lipid made of glycerol, 2 fatty acids and one phosphate

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2
Q

What is phagocytosis?

A

The process of the cell membrane engulfing large particles bringing them into a cell in a vesicle.

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3
Q

What does hydrophobic mean

A

A molecule or ion which cannot react with water molecules as it is non polar so no charge

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4
Q

What is water potential?

A

The tendency for water to move in or out of a system.

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5
Q

What is the water potential of pure water?

A

Zero

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6
Q

What decreases water potential?

A

Addition of a solute

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7
Q

What does lipid soluable mean?

A

It can dissolve in lipids

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8
Q

What is a vesicle?

A

A temporary vacuole

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9
Q

What is ATP?

A

The molecule energy is converted into during respiration.

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10
Q

What is secretion?

A

The process of which a substance is released form a cell when a vesicle fused with the plasma membrane.

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11
Q

What is plasmolysis?

A

Plant cells in a hypertonic solution loose water by osmosis so the vacuole and cytoplasm shrinks away from the cell wall to become flaccid.

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12
Q

What is a solution?

A

A mixture of a solvent and solute

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13
Q

What is the fluid mosaic model?

A

The structure of biological membranes where proteins are studded through a phospholipid bilayer and fluid because they can move about.

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14
Q

What does selectively permeable mean?

A

Only some molecules can diffuse across

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15
Q

What is the water potential gradient?

A

High to low

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16
Q

What is diffusion?

A

The movement of particles from a high to low concentration down a concentration gradient until equally distributed.

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17
Q

What is pinocytosis

A

The active process of the cell membrane engulfing droplets of fluid bringing them into the cell through a vesicle.

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18
Q

What is facilitated diffusion?

A

When ions and molecules move down the concentration gradient across a membrane by a protein carrier molecule or channel protein in the membrane.

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19
Q

What is solute potential?

A

The measure of how easily molecules move about in solution.

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20
Q

What is active transport?

A

The movement of molecules or ions across a membrane against the concentration gradient until equally distributed. It is an active process so used ATP

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21
Q

What is osmosis?

A

The net movement of water molecules across a selectively permeable membrane down the concentration gradient until equally distributed.

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22
Q

What does water soluable mean?

A

The substance will dissolve in water.

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23
Q

What is exocytosis?

A

The process of which a substance leaves the cell when a vesicle fuses with the plasma membrane to release the substance.

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24
Q

What does isotonic mean?

A

The cell has the same water potential as the surrounding solution so there is not net water movement.

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25
Q

What is a solute?

A

Something that can dissolve

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26
Q

What does turgid mean?

A

The cell has absorbed as much water as it can so the contents push against the cell wall

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27
Q

What is hypertonic?

A

The external solution is more negative (water potential) than the solution inside the cell so water moves out of the cell.

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28
Q

What does hydrophilic mean?

A

It will react with water because it is a polar molecule and has a charge.

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29
Q

Where can phospholipids be found?

A

Cell surface membrane

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30
Q

Why are phospholipids used to make the cell surface membrane?

A
  • can form bilayers
  • inner layer and outer layer of hydrophilic heads which interact with water in and around the cell
  • hydrophobic heads both point inwards towards the centre of the membrane.
  • the phospholipid component allows lipid soluble molecules across
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31
Q

Where do you find protein on the cell surface membrane?

A

Scattered throughout the phospholipid bilayer

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32
Q

What are intrinsic proteins?

A

Extended across both layers of the bilayer. Some are carrier proteins to transport water soluble molecules and others are channel proteins to allow active transport of ions

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33
Q

What are extrinsic proteins?

A

A protein that only covers half of the bilayer

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34
Q

Why are extrinsic proteins helpful

A

They provide structural support and form recognition sites for hormone attachment.

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35
Q

Who proposed the fluid mosaic model?

A

Singer and Nicholson in 1972

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36
Q

What makes the fluid mosaic model of the membrane structure fluid?

A

The individual phospholipid molecules can move within a layer relative to one another.

37
Q

What makes the membrane structure like a mosaic?

A

The embedded proteins vary in shape and size and pattern

38
Q

What is found in a membrane?

A
  • cholesterol (animal cells) between phospholipid molecules to make it rigid and stable
  • glycoproteins and glycolipids on outer layer
  • carbohydrates around the membrane. (Glycocalyx) some molecules have roles as hormones receptors or recognition.
39
Q

In which two ways are membranes permeable?

A

Lipid soluble diffuse across the membrane.

Water soluble pass through intrinsic proteins.

40
Q

Give an example of a lipid soluble substance

A

Vitamin A

41
Q

How are lipid soluble substances transported through the cell membrane?

A

Dissolve in the phospholipid and diffuse across the membrane as they are often small molecules.

42
Q

Why can lipid soluble substances move across the membrane more easily than water soluble ones?

A

The phosphate head is hydrophobic

43
Q

Name water soluble substances

A 
Glucose 
Polar molecules (like ions)
44
Q

How do water soluble substances move across the cell membrane?

A

Through intrinsic proteins which form water channels across the membrane. This makes the cell surface membrane selectively permeable to water and some solutes.

45
Q

What is the definition of diffusion?

A

The movement of molecules or ions from a region of higher concentration to lower concentration down the concentration gradient until equally distributed.

46
Q

What does passive process mean and give examples

A

No energy required

Osmosis. Simple diffusion. Facilitated diffusion

47
Q

What affects the rate of diffusion?

A
  • concentration gradient
  • thickness of exchange surface and distance
  • surface area of the membrane
  • temperature.
  • size of diffusing molecule.
  • nature if the molecule( lipid soluble/water soluble)
48
Q

What is the formula for rate of diffusion.

A

Rate of diffusion =

(Surface area X difference in conc) / length of diffusion path

49
Q

What type of molecules move through diffusion?

A

Small and non polar molecules.

50
Q

What is facilitated diffusion?

A

The movement of water soluble molecules through a transport protein molecule (carrier or channel protein) as they cannot pass through the phospholipid bilayer.

51
Q

What limits the rate of facilitated diffusion?

A

The number and availability of transport protein molecules.

52
Q

How does the channel protein allow molecules to diffuse?

A

The channel proteins are molecules with pores lined with polar groups so they are hydrophilic, allowing water soluble ions to dissolve and pass through.
The channels can open and close according to the cells needs.

53
Q

Describe what a carrier protein does to allow the diffusion if particles.

A
  • it allows the diffusion of larger polar molecules like sugars and amino acids.
  • a molecule attaches to its binding site on carrier protein which changes shape and releases the molecule on the other side of the membrane.
54
Q

What factors affect the permeability of the cell membrane?

A

Heat
Ethanol
PH

55
Q

What is co-transport?

A

A type of facilitated diffusion by which two substances are simultaneously transported across a membrane by a carrier protein

56
Q

What tells you that co-transport is an active process?

A
  • protein pump
  • ATP supplied
  • ions move from low to higher concentration.
57
Q

Describe the process of co-transport.

A

Proton pump transports ions from low to higher concentration using ATP as an energy source. Some ions and other molecules like sucrose can diffuse back across the membrane through and symport carrier at the same time.

58
Q

What is the use of ATP during co-transport?

A

ATP is hydrolysed time ADP to release energy for the process. The ADP binds to the protein which then changes shape.

59
Q

What does hypotonic mean?

A

The solution has a higher water potential (less negative/ less concentrated)

60
Q

What does hypertonic mean?

A

The solution has a lower water potential (more negative and more concentrated)

61
Q

What does isotonic mean?

A

Solutions have equal water potential so no net water movement.

62
Q

What does it mean if a cell is plasmolysed?

A

The membrane and contents have peaked away from the cell wall.

63
Q

In what situation would a cell become plasmolysed?

A

If the plant cell was in a hypertonic solution, water leaves cell by osmosis making the cell wilted/ flaccid because the cytoplasm and vacuole shrink.

64
Q

What is incipient plasmolysis?

A

A plant cell where the cell membrane is just about to pull away from the cell wall in an isotonic solution.

65
Q

What is the definition of osmosis?

A

The net movement of water through a selectively permeable membrane from higher to lower water potential down the concentration gradient.

66
Q

Is osmosis passive or active

A

Passive

67
Q

What reduces the number of water molecules available to diffuse?

A

Particles of dissolved substances like sugars and salts

68
Q

What is water potential?

A

The ability for water to leave a system

69
Q

What is water potential measured in?

A

Kilopascals (kPa)

70
Q

What is the water potential of pure water?

A

Zero

71
Q

What decreases water potential and why?

A

The addition of solutes because there is less water available to move around freely

72
Q

How does water move in terms of water potential?

A

Higher to lower

water molecules are attracted to the dissolved substances

73
Q

What causes animal cells to burst when in hypotonic solution?

A

Water is drawn into the cell, but there is not cell wall to apply pressure to (low pressure potential) so the cell bursts.

74
Q

What is solute potential?

A

The effect of solutes lowering the water potential of the cell sap, always a negative value.

Measures how easily molecules move about in solution.

75
Q

What is pressure potential?

A

It’s usually positive and is when the cell contents pushes against the cell wall, which then pushes back in.

Plant cells only.

76
Q

What is the equation for water potential?

A

Solute potential+pressure potential = water potential.

77
Q

What does turgid mean?

A

The cell has absorbed as much water as it can

78
Q

What is the equation for water potential of an animal cell?

A

Water potential=solute potential

79
Q

What does crenated mean?

A

Water has left the animal cell to make it shrink.

80
Q

What does lysis mean?

A

The cell has taken in too much water and burst.

81
Q

What is cytosis?

A

Transport of materials in or out of cells as a mechanism for bulk transport across a cell membrane.

82
Q

Is cytosis active or passive?

A

Active transport

83
Q

What is phagocytosis?

A

The uptake if solid materials too large to be diffused. The material is engulfed in a vesicle

84
Q

What’s pinocytosis?

A

The uptake of liquid through small vesicles.

85
Q

What is exocytosis?

A

When substances leave the cell having been transported through the cytoplasm in a vesicle which then fuses with the membrane.
*secretion from the cell.

86
Q

What is cyanide?

A

A strong poison which can work as a respiratory inhibitor. The enzyme cytochrome oxidase catalyses the reaction:
ADP+P=> ATP
If the enzyme is inhibited, ATP cannot be produced so the organism quickly dies.

87
Q

What is active transport?

A

It is the movement of substances up the concentration gradient from a low to high concentration with the use of ATP as an energy source

88
Q

What is ATP broken down into after its use in active processes?

A

ADP + P

89
Q

What does the ATP do to the protein pump during active transport?

A

It supplies energy to the protein pump to allow it to change shape and release the substance on the other side of the membrane

A-level Biology (13 decks)

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