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1. Cell Biology > Endomembrane System > Flashcards

Endomembrane System Flashcards

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1
Q

List the seven functions of the cell membrane.

A

Transport processes

Protective barrier/boundary

Cell-cell communication

Cellular signalling

Signal conduction

Cell to cell recognition

Cell shape

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2
Q

Explain the transport processes of the cell membrane.

3

A

Membranes control what information is received from other cells or the external environment

Membranes control the import and export of signals from other cells or the external environment

Membranes are flexible and have a capacity for movement and expansion

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3
Q

What property of the cell membrane allows it to expand?

A

The membrane is flexible

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4
Q

The cell membrane is flexible what does this allow for?

2

A

Movement

Expansion

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5
Q

Explain the protective barrier/boundary function of the cell membrane.

A

Membranes define boundaries of cells and the boundaries of organelles

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6
Q

Explain the cell-cell communication function of the cell membrane.

A

Specific plasma membrane gap junction proteins (desmosomes, tight junctions) of adjacent cells lines up and forms pipelines between two cells

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7
Q

What do desmosomes and tight junctions form between cells?

A

These form pipelines between cells

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8
Q

Explain the cellular signalling function of the cell membrane.
(2)

A

Membrane proteins serve as receptors that recognise and bind specific molecules in the extracellular environment

This triggers a series of molecular events in the cell which can lead to a cellular response e.g. hormones

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9
Q

What do membrane proteins do?

A

They bind specific molecules in the extracellular environment

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10
Q

What happens when a membrane protein binds to a molecule?

2

A

It triggers a series of molecular events in the cell

This may lead to a cellular response e.g. hormones

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11
Q

Explain the signal conduction function of the cell membrane.

A

Membranes have electrical properties which can serve as a mechanism of signal conduction when a cell receives an electrical, chemical or mechanical stimulus e.g. Neurons and muscle cells

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12
Q

What properties of the cell membrane allow for signal conduction?

A

The membranes electrical properties allow for this

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13
Q

What type of signal can be conducted through a cell membrane?
(3)

A

An electrical stimulus e.g. neurons

A chemical stimulus

A mechanical stimulus e.g. muscle cells

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14
Q

Explain the cell to cell recognition function of the cell membrane.

A

Some glycoproteins in the plasma membrane act as identification tags that are specifically recognised by membrane proteins to other cells

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15
Q

What act as identification tags as part of the cell membrane?

A

Glycoproteins

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16
Q

What is the function of glycoproteins?

A

They can be specifically recognised by membrane proteins on other cells

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17
Q

Explain the cell shape function of the cell membrane.

2

A

Cytoskeletal may be noncovalently bound to membrane proteins

This helps maintain cell shape and stabilises the location of certain membrane proteins

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18
Q

What can bind to the membrane proteins of the cell membrane?

A

The cytoskelton

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19
Q

Explain the fluid-mosaic model.

A

Fluid = individual phospholipids and proteins which can move side to side within the layer, like its a liquid

Mosaic = the pattern produced by the scattered protein molecules when the membrane is viewed from above

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20
Q

What type of substances can pass through the cell membrane easily?
(3)

A

Substances that are lipid soluble

Small molecules

Larger hydrophobic molecules

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21
Q

What molecules cannot pass through the cell membrane on their own?
(3)

A

Ions

Hydrophilic molecules larger than water

Large molecules such as proteins

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22
Q

What two types of molecules make up the cell membrane?

A

Lipids

Proteins

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23
Q

What three types of lipids make up the cell membrane?

A

Phospholipids

Cholesterol

Glyolipids

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24
Q

What two types of proteins make up the cell membrane?

A

Integral proteins

Peripheral proteins

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25
Q

Write a note on phospholipids.

3

A

Individual units which make up the membrane

Have a head (hydrophilic) and a tail (hydrophobic)

Tails are organised in a manner which keeps them away from water

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26
Q

What are the phospholipid heads?

A

These are hydrophilic phosphate groups

27
Q

What are the phospholipid tails?

A

2 hydrophobic strings of carbon and hydrogen atoms

28
Q

Describe the movement of phospholipids.

2

A

Can move sideways/laterally

Can flip move vertically (rotate with bottom part of membrane)

29
Q

How often do phospholipids move laterally?

A

Multiply times per second

30
Q

How often do phospholipids rotate with the bottom part?

A

Once per month

31
Q

Write a note on cholesterol.

3

A

It’s an amphiphatic molecule

It has an a polar head which attaches to the polar part of phospholipids

Made up of four rings of hydrogen and carbon atoms

32
Q

Where does the polar head of cholesterol attach?

A

It attaches to the polar part of phospholipids

33
Q

How does cholesterol strengthen the cell membrane?

A

Cholesterol prevents some small molecules from crossing it

34
Q

How do phospholipids benefit from cholesterol?

A

Cholesterol molecules also prevent the phospholipid tails from coming into contact and solidifying

35
Q

Cholesterol prevents the phospholipid tails from solidifying, what affect does this have on the overall cell membrane?

A

This ensures the cell membrane stays fluid and flexible

36
Q

What are glycolipids?

A

They are molecules which have a fatty acid tail and a carbohydrate head (chain of sugars)

37
Q

What is the function of glycolipids?

A

Cell to cell recognition and communication

They contribute to a human’s blood type

38
Q

Describe the carbohydrate chain which is found in glycolipids.

A

The short carbohydrate chain is covalently attached

It is exposed on the outer surface of the cell

39
Q

What do the short carbohydrate chains of a glycolipid do?

2

A

They provide stability for the cell

They help cells join to to other cells to form tissues

40
Q

How do glycolipids contribute to a person’s blood type?

2

A

There are four main blood types: A, B, AB and O

This variation stems from the different glycolipids present on the surface of erythrocytes

41
Q

What are integral proteins?

A

Proteins with one or more hydrophobic regions with an affinity for the hydrophobic interior of the lipid bilayer

42
Q

Where are integral proteins found?

A

They are embedded in the membrane and cannot be easily removed

43
Q

What are integral proteins generally?

A

They are generally transport proteins

44
Q

Name two types of transport proteins?

A

Channel proteins

Carrier proteins

45
Q

What are peripheral proteins?

2

A

Proteins which lack a hydrophobic sequence and therefore do not penetrate the lipid bilayer

Instead they associate with the membrane surfaces and through weak electrostatic forces

46
Q

How do peripheral proteins associate with the membrane surfaces?
(2)

A

They bind either to the polar heads of the membrane lipids

Or they bind to the hydrophilic portions of the integral proteins which extend out of the membrane

47
Q

What are the two classes of transport proteins?

A

Carrier proteins

Channel proteins (Ion channels)

48
Q

What are carrier proteins?

2

A

They bind the solute on one side of the membrane

They then deliver it to the other side of the membrane by conformational change in protein (turnstile) - rotating so they can release the solute on the other side

49
Q

What are channel proteins (ion channels)?

A

They form hydrophilic pores in the membrane through which solutes (mainly ions) can diffuse (trapdoor)

50
Q

What are the two ways of cell membrane transport?

A

Passive transport

Active transport

51
Q

What is passive transport?

2

A

Passive transport does not require energy

It occurs because of the tendency for dissolved molecules to move or diffuse from higher to lower concentrations

52
Q

What are the two different types of passive transport?

A

Simple diffusion

Facilitated diffusion

53
Q

What is simple diffusion?

A

Diffusion whereby molecules move from a region of higher concentration to a region of lower concentration

54
Q

What is facilitated diffusion?

A

Diffusion whereby molecules depend on specialised membrane proteins to aid the passage of ions or polar molecules across the hydrophobic interior of the membrane

55
Q

What is active transport?

4

A

Transport which required the input of energy

It moves solutes against their concentration gradient which require work

It requires special membrane proteins (pumps)

Can result in the generation of a concentration gradient across the membrane

56
Q

Give an example of a protein pump.

A

Sodium-potassium pump

57
Q

How does a sodium-potassium pump work?

A

It exchanges sodium (Na+) out of the cell for potassium (K+) inside the cell

58
Q

What is coupled transport?

A

ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes across the membrane

59
Q

What are the two types of co-transport?

A

Symport coupled transport

Antiport coupled transport

60
Q

What is symport coupled transport?

A

Molecules move in the same direction across the membrane

61
Q

What is antiport coupled transport?

A

Molecules move in opposite directions across the membrane

62
Q

Give an example of symport coupled transport.

A

Glucose and sodium from outside to inside the cell

63
Q

Give an example of antiport coupled transport.

A

Sodium potassium pump to pump sodium outside the cell and pump potassium into the cell

64
Q

What is the function of membranes?

A

They provide compartmentalisation, which allows different places in the cell to have different environments

1. Cell Biology (6 decks)

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