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1. Cell Biology > Endomembrane System > Flashcards

Endomembrane System Flashcards

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
Write a note on phospholipids. | 3
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
26
What are the phospholipid heads?
These are hydrophilic phosphate groups
27
What are the phospholipid tails?
2 hydrophobic strings of carbon and hydrogen atoms
28
Describe the movement of phospholipids. | 2
Can move sideways/laterally Can flip move vertically (rotate with bottom part of membrane)
29
How often do phospholipids move laterally?
Multiply times per second
30
How often do phospholipids rotate with the bottom part?
Once per month
31
Write a note on cholesterol. | 3
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
Where does the polar head of cholesterol attach?
It attaches to the polar part of phospholipids
33
How does cholesterol strengthen the cell membrane?
Cholesterol prevents some small molecules from crossing it
34
How do phospholipids benefit from cholesterol?
Cholesterol molecules also prevent the phospholipid tails from coming into contact and solidifying
35
Cholesterol prevents the phospholipid tails from solidifying, what affect does this have on the overall cell membrane?
This ensures the cell membrane stays fluid and flexible
36
What are glycolipids?
They are molecules which have a fatty acid tail and a carbohydrate head (chain of sugars)
37
What is the function of glycolipids?
Cell to cell recognition and communication They contribute to a human's blood type
38
Describe the carbohydrate chain which is found in glycolipids.
The short carbohydrate chain is covalently attached It is exposed on the outer surface of the cell
39
What do the short carbohydrate chains of a glycolipid do? | 2
They provide stability for the cell They help cells join to to other cells to form tissues
40
How do glycolipids contribute to a person's blood type? | 2
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
What are integral proteins?
Proteins with one or more hydrophobic regions with an affinity for the hydrophobic interior of the lipid bilayer
42
Where are integral proteins found?
They are embedded in the membrane and cannot be easily removed
43
What are integral proteins generally?
They are generally transport proteins
44
Name two types of transport proteins?
Channel proteins Carrier proteins
45
What are peripheral proteins? | 2
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
How do peripheral proteins associate with the membrane surfaces? (2)
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
What are the two classes of transport proteins?
Carrier proteins Channel proteins (Ion channels)
48
What are carrier proteins? | 2
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
What are channel proteins (ion channels)?
They form hydrophilic pores in the membrane through which solutes (mainly ions) can diffuse (trapdoor)
50
What are the two ways of cell membrane transport?
Passive transport Active transport
51
What is passive transport? | 2
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
What are the two different types of passive transport?
Simple diffusion Facilitated diffusion
53
What is simple diffusion?
Diffusion whereby molecules move from a region of higher concentration to a region of lower concentration
54
What is facilitated diffusion?
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
What is active transport? | 4
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
Give an example of a protein pump.
Sodium-potassium pump
57
How does a sodium-potassium pump work?
It exchanges sodium (Na+) out of the cell for potassium (K+) inside the cell
58
What is coupled transport?
ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes across the membrane
59
What are the two types of co-transport?
Symport coupled transport Antiport coupled transport
60
What is symport coupled transport?
Molecules move in the same direction across the membrane
61
What is antiport coupled transport?
Molecules move in opposite directions across the membrane
62
Give an example of symport coupled transport.
Glucose and sodium from outside to inside the cell
63
Give an example of antiport coupled transport.
Sodium potassium pump to pump sodium outside the cell and pump potassium into the cell
64
What is the function of membranes?
They provide compartmentalisation, which allows different places in the cell to have different environments

1. Cell Biology (6 decks)

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