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Biology Paper 1 > Cells: Transport across cell membranes > Flashcards

Cells: Transport across cell membranes Flashcards

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1
Q

What is diffusion?

A

The movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient.

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2
Q

What are the four factors that affect simple diffusion?

A

Concentration gradient
Membrane thickness
Surface area
Temperature

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3
Q

What is the relationship between concentration gradient and the rate of simple diffusion?

A

The greater the concentration difference, the faster the rate of diffusion.

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4
Q

What is the relationship between membrane thickness and the rate of simple diffusion?

A

The thinner the membrane, the faster the rate of diffusion.

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5
Q

What is the relationship between surface area and the rate of simple diffusion?

A

The larger the surface area the faster the rate of diffusion.

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6
Q

What is the relationship between temperature and the rate of simple diffusion?

A

The higher the temperature the faster the rate of diffusion.

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7
Q

Explain how concentration gradient increases the rate of diffusion:

A

A good blood/air supply helps to maintain concentration gradients by transporting substances to and from the membrane.

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8
Q

Explain how membrane thickness increases the rate of diffusion:

A

Thin membranes reduce the distance the particles have to travel.

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9
Q

Explain how surface area increases the rate of diffusion:

A

Increasing the surface area of a membrane means more particles can be exchanged in the same amount of time.

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10
Q

Explain how temperature increases the rate of diffusion:

A

At higher temperatures particles will have more kinetic energy so they will be able to move around faster.

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11
Q

What do carrier proteins move across membranes?

A

Large molecules

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12
Q

What are the two types of proteins involved in facilitated diffusion?

A

Carrier proteins
Channel proteins

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13
Q

How do carrier proteins transport molecules across a membrane?

A
  • Large molecules attach to the carrier protein
  • Protein changes shape
  • Protein is released on the other side of the membrane.
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14
Q

What type of proteins transport charged particles through membranes?

A

Channel proteins

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15
Q

How do channel proteins transport charged particles across a membrane?

A

They have a tunnel shape which allows them to cross the membrane.

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16
Q

What are the two factors affecting the rate of facilitated diffusion?

A

Concentration gradient
Number of channel/carrier proteins

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17
Q

Explain the relationship between concentration gradient and the rate of facilitated diffusion:

A

The greater the concentration gradient the greater the rate of facilitated diffusion

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18
Q

Explain the relationship between number of channel/carrier proteins and the rate of facilitated diffusion:

A

The greater the number of channel/carrier proteins in the plasma membrane the greater the rate of facilitated diffusion.

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19
Q

Is diffusion an active or passive process? Why?

A

Passive process as it doesn’t require ATP energy.

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20
Q

An optical microscope cannot be used to see a plasma membrane. Explain why:

A

The optical microscope has a low resolution and magnification so detail (plasma membrane) cannot be seen.

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21
Q

What are the 4 properties of substances that are able to diffuse through a phospholipid bilayer membrane?

A

Small
Uncharged
Non-polar
Non-lipid soluble

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22
Q

What is facilitated diffusion?

A

Diffusion involving the presence of protein carrier molecules to allow the passive movement of substances across a plasma membrane.

23
Q

What is a glycolipid:

A

Lipids with a carbohydrate attached

24
Q

What is a glycoprotein:

A

Proteins with a carbohydrate attached

25
Q

What is the model called that shows the arrangement of the phospholipid bilayer?

A

Fluid-mosaic model

26
Q

What is cell sap?

A

The liquid found in the vacuole of plant cells, consisting of water and ions.

27
Q

Define dilute:

A

A solution with a low concentration

28
Q

What is an isotonic solution:

A

A solution which has the same water potential as the cell within it

29
Q

Define osmosis:

A

The passage of water from an area of higher water potential to an area of lower water potential through a semi-permeable membrane.

30
Q

What is a solute?

A

The dissolved substance in a solution.

31
Q

What is a solution?

A

A mixture formed by a solute and solvent

32
Q

What is a solvent?

A

The liquid in which the solute dissolved to form a solution.

33
Q

Define turgid:

A

Enlarged and swollen with water.

34
Q

What is water potential?

A

The pressure created by water molecules.

35
Q

What will happen to an animal cell in a hypertonic solution? Why?

A
  • Cell will shrivel
  • There is a higher water potential inside the cell than outside the cell
  • So water leaves the cell
36
Q

What is a hypertonic solution?

A

A solution which has a higher solute concentration and lower water concentration compared to the inside of a cell.

37
Q

What is an isotonic solution?

A

A solution which has the same solute and water concentration as inside a cell.

38
Q

What happens to an animal cell in an isotonic solution? Why?

A
  • Cells remain healthy
  • The water potential is equal in the solution and inside the cell
  • There is no net movement of water.
39
Q

What is a hypotonic solution?

A

A solution which has a lower solute concentration and higher water concentration compared to the inside of a cell.

40
Q

What happens to an animal cell in a hypotonic solution? Why?

A
  • Cell bursts
  • Water potential inside the cell is lower than outside the cell
  • Water moves into the cell
41
Q

What happens to a plant cell in a hypotonic solution?

A

Cell becomes turgid as the cell membrane pushes on the cell wall.

42
Q

What happens to a plant cell in a hypertonic solution?

A

Their vacuoles shrink and plasmolysis occurs.

43
Q

What is plasmolysis in plant cells?

A

The cell membranes pull away from the cell walls

44
Q

Why is active transport an active process?

A

It uses ATP from respiration to go against the concentration gradient.

45
Q

What are the 5 types of transport across cell membranes?

A
  • Simple diffusion
  • Facilitated diffusion
  • Osmosis
  • Active transport
  • Co-transport
46
Q

Why can the phospholipid bilayer be considered fluid?

A

The phospholipids are constantly moving.

47
Q

Define diffusion:

A

The movement of a substance from an area of a high substance concentration to an area of low substance concentration along a concentration gradient.

48
Q

What is simple diffusion?

A

When molecules diffuse directly through a cell membrane.

49
Q

Why are carbon and oxygen atoms able to use simple diffusion across a membrane?

A

They are small and non-polar

50
Q

The higher the concentration gradient, the ____ the rate of diffusion.

A

Faster

51
Q

The thinner the exchange surface, the ____ the rate of diffusion.

A

Faster

52
Q

The larger the surface area, the _____ the rate of diffusion.

A

Faster

53
Q

Define osmosis:

A

The movement of water from an area of a higher water potential to an area of a lower water potential across a semi-permeable membrane along a concentration gradient.

54
Q

Explain the absorption of glucose through co-transport:

A

1) Sodium ions are actively transported out of the epithelial cells in the ileum into the blood by the sodium-potassium pump. This creates a concentration gradient as there is a higher concentration of sodium ions in the ileum lumen than inside the cell.
2) This causes sodium ions to diffuse from the ileum lumen into the epithelial cell, down their concentration gradient through transport proteins. Glucose and sodium enter the cell, so the concentration of glucose inside the cell increases.
3) Glucose diffuses out of the cell into the blood down its concentration gradient through a protein channel by facilitated diffusion.

Biology Paper 1 (32 decks)

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