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✅Biology AS Unit 1 > ▪️C1.3 -cell Memebranes and transport > Flashcards

▪️C1.3 -cell Memebranes and transport Flashcards

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1
Q

Why are phospholipids a important component of the cell surface membrane?

A
  • they can form bilayers
  • inner layer of phospholipids has its hydrophilic head pointing in towards the cell, interacting with the water in cytoplasm
  • outer layer has its hydrophilic head pointing outwards, interacting with the water surrounding the cell
  • hydrophobic tails point towards each other, to the centre membrane
  • phospholipid component of a membrane allows lipid soluble molecules across but not water soluble molecules
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2
Q

Where are proteins in a cell membrane?

Name the 2 forms of protein present

A

Scattered throughout the phospholipid Bilayer of the membrane embedded as either extrinsic or intrinsic proteins

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3
Q

Describe extrinsic proteins and their purpose

A

On the surface of the bilayer.
Provide structural support
Form recognition sites by identifying cells and receptor sites for hormone attachment

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4
Q

Describe intrinsic proteins and their purpose

A

Extended across both layers of the phospholipid bilayer

Includes carrier and channel proteins

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5
Q

What do carrier proteins (intrinsic proteins) do?

A

They transport water soluble substances across the cell membranes

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6
Q

What do channel proteins (intrinsic proteins) do?

A

Allow active transport of ions across the membrane through forming channels

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7
Q

Why is the fluid mosaic structure called the fluid mosaic structure?

A
  • the individual phospholipid molecules can move within a layer relative to one another (fluid)
  • the proteins embedded into the bilayer vary shape and size and pattern (mosaic) lol
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8
Q

Where in the cell membrane is cholesterol found? What is it’s purpose?

A

In the membranes of animal cells, between the phospholipid molecules, making the membrane more rigid and stable

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9
Q

Where in the cell membrane are glycoproteins and glycolipids found?

A

In the outer layer of the membrane.

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10
Q

What is the outer layer around the cell membrane called? What is it’s role?

A

The glycocalyx

The molecules in the glycocalyx have roles as hormone receptors or in cell-to-cell recognition

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11
Q

What can diffuse across the membrane?

A

Lipid soluble substances such as vitamin A, small molecules like oxygen and carbon dioxide can dissolve in the phospholipid and diffuse across the membrane

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12
Q

How does the phospholipid layer being hydrophobic effect diffusion is different molecules

A

Lipid soluble molecules move through the cell membrane more easily than water soluble substances

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13
Q

Name molecules that struggle to diffuse through membrane

Why is this?

A

Glucose, polar molecules and jk s can’t readily diffuse through the phospholipids
This is because they are water soluble

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14
Q

How do water soluble substances pass through the cell membrane?

A

They pass through intrinsic protein molecules which form water filled channels across the membrane

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15
Q

What is the name for a membrane that picks what to diffuse in and out

A

Selectively permeable membrane

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16
Q

Define simple diffusion

A

The movement of molecules or ions from a region of high concentration to lower concentration down a concentration gradient until equilibrium is reached. It is a passive process it does not require atp

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17
Q

Name the factors affecting simple diffusion:

A
  • the concentration gradient (greater difference the more molecules diffuse in a given time)
  • thickness of the exchange surface/distance of travel where diffusion takes place (thinner=more molecules diffuse)
  • the surface area is the membrane
  • size of diffusing molecules (smaller diffuses faster)
  • temperature
  • nature of diffusing molecules (fats diffuse faster than water soluble molecules)
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18
Q

Name the rate of diffusion equation:

A

(Surface area x difference in concentration) divided by the length of diffusion pathway

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19
Q

Define facilitated diffusion.

A

The passive transfer of molecules or ions die. A concentration gradient, across a membrane by protein carrier molecules In the membrane

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20
Q

Where does facilitated diffusion occur?

A

At a specific sit on the plasma membrane wher there are transport protein molecules (intrinsic carrier/channel proteins)

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21
Q

Define channel proteins in detail

A

Molecules with pores lines with polar groups. As the channels are hydrophilic, water soluble ions can pass through. The channels open and close according to the needs of the cell

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22
Q

Define carrier proteins in detail

A

Allow diffusion of larger polar molecules such as sugar and amino acids across the membrane. A molecule attaches to its binding site, on the carrier protein. The carrier protein changes shape and released the molecule on the other side of the membrane

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23
Q

Describe how larger molecules e.g amino acids diffuse through a cell membrane

A

A molecule attaches to the binding site, on the carrier protein. The carrier protein changes shape and releases the molecule on the other side of the membrane

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24
Q

Does the use of carrier proteins use ATP

A

No, carrier and channel proteins increase the rate of diffusion down a concentration gradient without energy in the form of ATP

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25
Q

Define active transport

A

A process in which ions and molecules move from an area of low concentration to high concentration against a concentration gradient through a semi permeable membrane, it is an active process it requires ATP

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26
Q

Name some features of active transport

A

1- ions/molecules are moved from a lower to higher concentration against a concentration gradient
2- requires energy in the form ATP. Anything that affects respiration will effect active transport
3- process occurs through intrinsic carrier proteins spanning the membrane
4-rate is limited by the number and availability of carrier proteins

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27
Q

Name some processes involving active transport

A

Muscle contraction, nerve impulse transmission, reabsorption of glucose in the kidney nephron and mineral uptake into plant root hair cells

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28
Q

Describe the process of ATP

A

1) Molecule or ion combines with a specific carrier protein on the outside of the membrane
2) ATP transfers a phosphate group to the Carrie protein on the inside of the membrane
3) carrier protein changes shape and carried the molecule across the membrane, to the inside of the cell
4) molecule is realised into cytoplasm
5) phosphate ion is released from the carrier molecule back to the cytoplasm and recombined with ADP to form ATP
6) carrier protein returns to its original shape

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29
Q

What happens when an active transport graph Levels off?

A

The carrier proteins are saturated

30
Q

Name something that can stop active transport

Why?

A

A respiratory inhibitor such as cyanide can stop active transport
This is because they prevent aerobic respiration and the production of ATP in the mitochondria

31
Q

Define co-transport

A

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

32
Q

Name an example of co-transport

A

Sodium-glucose co-transport is significant In absorbing glucose and sodium ions across cell membranes and into the blood in the kidney nephron

33
Q

Describe how co-transport occurs

A

1- a glucose molecule and two sodium ions outside the cell attach to a carrier protein In the cell membrane
2- the carrier protein changes shape and deposits the glucose molecule and the sodium ions inside the cell
3-the glucose molecule and sodium ion separately diffuse through the cell to the opposite membrane

34
Q

What is the water potential of pure water

A

0

35
Q

What happens to the value of water potential when you add a solute

A

Addition of solute to pure water lowers the water potential making it a negative value

36
Q

Define osmosis

A

The net movement of water molecules from an area of High water potential to low water potential down a concentration gradient through a semi permeable membrane, it is a passive process it does not require ATP

37
Q

Define water potential

A

The tendency for water to move into a system, from an area of higher water potential to lower water potential. Water potential is decreased by the addition of a solute. Pure water has a water potential of 0

38
Q

What does solute potential measure?

A

Measures how easily water molecules move out of a solution

39
Q

Define turgid

A

A plant cell that holds as much water as possible, preventing further entry of water as the cell can’t expand further

40
Q

Name the 2 opposing forces in a plant cell

A

1) solute potential, due to diluted in the vacuole and cytoplasm, pulls water in to the cell meaning water is less likely to move out
2) pressure potential, a force which increases chance of water moving out

41
Q

Name the osmosis pressure equation

A

Water potential of cell= pressure potential + solute potential

42
Q

Describe when a hypotonic situation occurs

A

If the water potential of the external solution is less negative (greater) than the solution inside the cell.
Water would flow into the cell

43
Q

Describe when a hypertonic situation occurs

A

If the water potential of the external solution is more negative (less) than the solution inside the cell
Water flows out of the cell

44
Q

Describe how a isotonic situation occurs

A

If the cell has the same water potential as the external solution
No net water movement

45
Q

Define the process of plasmolysis

What happens when complete?

A

Occurs when plants in s hypertonic solution lose water by osmosis and the vacuole shrinks
and cytoplasm draws away from cell wall

When complete the cell is flaccid and plant wilts

46
Q

Define the process of incipient plasmolysis

A

Occurs when the external concentration is High enough so just enough water is lost do the membrane begins to pull away from the cell wall

47
Q

What is the pressure potential of a cell in incipient plasmolysis?
Why?

A

0

Because the cell wall does not exert any pressure on the cytoplasm

48
Q

What is the pressure equation of a cell in incipient plasmolysis

A

Water potential =solute potential

49
Q

What is the value of water potential in a fully turgid cell?

A

0

50
Q

What is the pressure equation in a fully turgid cell?

A

Pressure potential = - solute potential

51
Q

Why is turgor important to plants

A

Provides support, maintains their shape and holds them upright

52
Q

Name the water potential equation in an animal cell

A

Water potential = solute potential

53
Q

Describe the process of haemolysis

A

If red blood cells are in distilled water, water enters by osmosis and they burst as they don’t have a cell wall

54
Q

Describe the process of crenation

A

When red blood cells are placed in concentrated salt solution, water leaves the cells and they shrink

55
Q

Name the 2 methods of bulk transport

A

Endocytosis

Exocytosis

56
Q

When does endocytosis occur?

A

When material is engulfed by extensions of the plasma membrane and cytoplasm, forming a vesicles

57
Q

Name the 2 types of endocytosis

A

Phagocytosis

Pinocytosis

58
Q

Define phagocytosis

A

The Uptake of solid material that is too large to be taken in by diffusion or active transport

59
Q

Describe the process of phagocytosis

A

When granulocytes engulf Bactria, a lysosomes fuses with the vesicle formed and enzymes digest the cells, products are absorbed into cytoplasm

60
Q

Define exocytosis

A

Process where substances leave the cell, having been transported trough the cytoplasm in a vesicle, which fuses with the cell membrane.

61
Q

Give an example of something that is secreted by exocytosis

A

Digestive enzymes

62
Q

Why is endocytosis and exocytosis active processes

A

The cell membrane has to change shape which requires energy is the form of ATP, generated by the cells respiration

63
Q

Why is the cell membrane being fluid vital to the cell?

A

Because the cell membrane flows with endocytosis decreasing the overall are of the cell membrane and exocytosis increasing it

64
Q

Suggest two reasons why transport across the membrane is vital to the cell

A
  • Maintains water potential in cells
  • obtain oxygen/remove CO2
  • obtain minerals/nutrients e.g glucose
65
Q

Describe the role of the cell wall in generating pressure potential

A

Cell wall is inelatic/won’t stretch
Water passes into the cell via osmosis and the protoplast swells/expands
This pushes against cell wall and due to its resistance generate a pressure potential

66
Q

Suggest 2 functions of membrane proteins

A
  1. Acts as recognition sites for cell-to-cell recognition of individual cells
  2. transport proteins allow water soluble/ polar substances to penetrate the membrane
67
Q

How does oxygen enter the cell

A

-by simple diffusion, through the phospholipid bilayer

68
Q

Describe how phosphate ions enter the cell

A

Phosphate ions travel by facilitated diffusion/active transport through carrier proteins

69
Q

Describe how the solubility in lipid affects the rate of diffusion through a membrane

A

As lipid solubility increases, the rate of diffusion increases as membrane contains double layer of phospholipids :: lipids can diffuse through the membrane more easily

70
Q

Describe how molecular size affects the rate of diffusion

A

The larger the molecule the slower the rate of diffusion as they are more difficult to pass between phospholipid molecules

✅Biology AS Unit 1 (10 decks)

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