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Bio Mod 2 > cell membranes > Flashcards

cell membranes Flashcards

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1
Q

where can membranes be found

A

they cover the surface of every cell and also surround most organelles in the cell

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2
Q

what is the function of a cell membrane

A
  • keep all the Cell components inside
  • Allow selected molecules to move in and out of the cell (Partially permeable)
  • isolate cytoplasm from extracellular environmemt
  • Isolate organelles from the rest of the cytoplasm allowing cellular processes to occur separately eg respiration
  • site for biochemical reactions eg respiration
  • Allows a cell to change shape
  • allows communication and recognition From other cells
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3
Q

what are phospholipids

A
  • the main component of cell membrane
  • made of a polar hydrophilic phosphate group an glycerol heads and 2 non-polar hydrophobic fatty acid tails
  • They act as a barrier to control what enters and exits the cell
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4
Q

when in water, what are the two structures the phospholipids form

A

micelle (enclosed circle)
bilayer (rectangle shape with a hydrophobic core)

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5
Q

how thick is the Phospholipid bilayer

A

7nm

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6
Q

What is the fluid mosaic model

A

Model describing the arrangement of molecules in the membrane,
It is fluid because it is constantly moving,
It contains protein molecules scattered throughout like tiles in a mosaic
Cholesterol fits, making it less fluid, more rigid

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7
Q

what can Diffuse across a membrane

A

Oxygen & Carbon dioxide
water & urea (are polar but can dissolve Slowly as they are very small)

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8
Q

Why can water soluble molecules not pass through the bilayer

A

Because the centre of the bilayer is hydrophobic Repels the water soluble molecules

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9
Q

What can disrupt the hydrophobic bilayer

A

Fat soluble substances EG alcoholic nicotine and caffeine

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10
Q

why do phospholipids form a bilayer in water

A

The layer is formed as the hydrophilic phosphate heads are facing the water because they are polar and hydrophobic core don’t Because they are nonpolar and they try to avoid the water.
Both tissue fluid and cytoplasm has water in it so the phospholipids form 2 layers with the tails facing inwards and phosphate groups outwards interacting with the aqueous environment

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11
Q

What are other components that can be found making up a cell membrane

A

Glycolipid
protiens
glycoprotein
cholesterol
Channel proteins
carrier proteins

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12
Q

What is the difference between intrinsic and extrinsic proteins

A

Intrinsic proteins span the whole width of the membrane (both layers)
Extrinsic proteins are confined to the inner or outer surface of the membrane

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13
Q

What is the function glycoproteins

A

Intrinsic Proteins with attached carbohydrate chains,
cell signalling (Indicates self cells)
Binds cells together to form tissues
Hormone receptors

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14
Q

what is the function of glycolipids in membranes

A

Lipid with a carbohydrate chain
Hormone receptors
Cell signalling (Indicate self-cell)

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15
Q

What is the general purpose of Intrinsic proteins

A

Involved in facilitated diffusion - transport substances like ions and amino acids that cannot diffuse across the membrane but are still vital to a cells functioning

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16
Q

how do intrinsic proteins stay in place?

A

amino acids with hydrophobic R groups which interact with the hydrophobic core of the membrane keeping them in place

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17
Q

function of Channel proteins in membranes

A

It provides a hydrophilic channel that allows diffusion of water soluble polar substances and ions Through the membranes

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18
Q

function of Carrier proteins

A

Transport of specific and often large substances which cannot pass directly across the membrane eg glucose

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19
Q

what happens at Receptor sites on membranes

A

hormones bind with Specific shaped receptors for specific hormones

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20
Q

What is the function of aquaporins

A

channel proteins which Allow water to pass through The membrane much faster

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21
Q

What are the three ways substances can move across the plasma membrane

A

Osmosis, active transport and diffusion

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22
Q

How does the membrane assist the processes of mitochondria

A

The substances needed for respiration are kept together inside by the mitochondria’s outer membrane
The inner membrane of mitochondria contains enzyme needed for respiration, it has a large surface area which increases the number of enzymes present making the rate of respiration faster and more efficient

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23
Q

How is the plasma membrane used in protein synthesis

A

Membranes form vehicles to transport the proteins between different areas of the cell (EG from RER to Golgi Apparatus) and out of the cell

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24
Q

Function of cholesterol in the plasma membrane

A

It gives the membrane stability
it is a type of lipid present in all cell membranes except bacterial cell membranes
cholesterol molecules fit between the Phospholipids, they bind to the hydrophobic tails causing them to pack more closely together this makes the membrane less fluid and more rigid, cholesterol also has hydrophobic regions so it is able to create a further barrier to polar substances moving through the membrane

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25
Q

What are the functions of extrinsic proteins

A

They may be free on the cell membrane or bound to an intrinsic protein

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26
Q

what are the functions of extrinsic protein in cell membrane

A

They have hydrophilic all groups and interact with the polar hydrophilic heads of the phosphor lipids or with other intrinsic proteins
On the exterior side they act as receptors or for hormones or neurotransmitters or are involved in cell recognition (Many of these are Glycoproteins)
On the interior side they are involved in cell signalling or chemical reactions they can dissociate from the membrane and move into the cytoplasm

27
Q

What is the function of the membrane surrounding chloroplast

A

Thylakoid membrane keeps the components needed for light dependent reactions of photosynthesis together

28
Q

what is the function of the membrane surrounding a bacterial cell

A

To control what goes in and out of the cell
to allow cell communication
to allow cell recognition

29
Q

Other than as carrier proteins what are two other functions of proteins in cell membrane

A

Receptors/enzymes/structural

30
Q

What does compartmentalization mean

A

Isolating each area from its external environment eg membranes form cells and separate areas within cells

31
Q

Why do alcohol, caffeine and nicotine (lipid soluble molecules) have an instant and widespread effect on the body

A

lipid soluble molecules can pass through membranes by simple diffusion so they go through the whole body

32
Q

Suggest the advantage to a highly folded membrane eg in Mitochondria

A

Processes on membranes are enzyme controlled, folding increases surface area, which means there are more enzymes, which increases the rate of respiration and therefore increases rate of atp produce Which is needed for cellular activities to survive

33
Q

How do ions pass through the membrane

A

Channel or carrier proteins

34
Q

Why are there more proteins in energy releasing organelles like mitochondria

A

Energy releasing organelles need lots of substances (like nutrients, enzymes, ATP) to travel across their membranes, some of these substances will require help from proteins to get through the membrane, so they will have a higher protein content

35
Q

Why is it important that a cell membrane maintains its fluidity

A

It is necessary for the diffusion of substances across the membrane
For the membrane diffuse through the recycle during Exocytosis
For cells to move and change shape eg like phagocytes when they engulf foreign objects

36
Q

State two features of a gas exchange surface

A

Large surface area and thin lining

37
Q

What is the effect of High temperature on the cell membrane

A

As temperature increases, the kinetic energy of the phospholipid increases,
creating gaps between the bilayer Making the layer more loosely packed, which molecules can pass through.
Channel protein and carrier proteins have denatured So they can’t control what enters and exits
Water inside the cell puts pressure on the membranes
therefore the permeability of the membrane has increased

38
Q

What happens to the Cell membrane at temperatures below freezing

A

The phospholipids don’t have much energy so they don’t move very much.
they are packed closely to form a Rigid layer.
channel proteins and carrier proteins denature.
ice crystals pierce the membranes increasing permeability significantly

39
Q

What is the effect of water on the cell membrane

A

it is polar, so it is important in creating membrane stability with the phospholipids,
phospholipids dissolve in non-polar solvents
so it doesn’t disrupt the cell membrane and can actually diffuse through slowly

40
Q

What molecules disrupt the bilayer

A

Alcohols caffeine nicotine

41
Q

what is the effect of alcohol on the body

A

When you drink alcohol, the water soluble ethanol it contains, has a free pass through your body. it enters the digestive system, rides in your bloodstream, passes through the cell membrane, Strolls through the heart.
It mainly goes to the brain where it becomes a central nervous system depressant, it causes feel good dopamine to be released

42
Q

How does alcohol slow down the brain

A

Binds to glutamate, a neurotransmitter that exceeds your neurons, And causes it to become unactive so your responses is are slower
Binds to gamma aminobutyric acid (GABA) It activates them so they release receptors which makes a person feel calm and sleepy so the brains function slows even further

43
Q

What does the effect of ethanol have on the permeability of the membrane

A

Ethanol is a non polar solvent so dissolves non polar substances like lipids (Phospholipids).
The membrane becomes permeable and allows substances to leak in and out of the cell.
As ethanol conk increases membrane permeability increases,
If ethanol is high enough it can disintegrate the membrane and completely kill the cell
(Causing the graph to level off)

44
Q

Effect of cholesterol on membrane fluidity

A

In high temperatures cholesterol decreases the fluidity of the membrane
in low temperatures cholesterol increases from membrane fluidity

45
Q

What increases fluidity of membrane

A

shorter phospholipid tails
Unsaturated tails/more double bonds
Less cholesterol
Less packed together
High temperatures

46
Q

Why is liquid seen to come out of frozen fruit after defrosted

A

The membrane (which would have holes from the piercing of the ice crystals Making it highly permeable) Allows the pigment to leak through

47
Q

How can water get through the cell membrane

A

Facilitated diffusion through channel protein aquaporin or simple diffusion through phosphorylated bilayer

48
Q

What is cell signalling

A

Processes that lead to communication and coordination between cells
One cell releases a messenger molecule eg a hormone, this travels to another cell in the blood and is detected by the cell because it binds to a receptor (A protein) on its cell membrane. the binding triggers a change in the cell ag a chemical signal is set of

49
Q

why might sell signalling be important

A

To control processes inside the body,
When responding to environmental changes

50
Q

What are membrane-bound receptors

A

Sensors on the outer cell surface membrane
often Protein molecules or glycoproteins
complementary in shape to signal molecule

51
Q

What are examples of signal/ Messenger molecules

A

hormones EG adrenaline insulin glucagon
Neurotransmitters eg noradrenaline
Cytokines - role in immune response

52
Q

What are drugs

A

Drugs have been developed that mimic the shape of Messenger molecules, they can trigger a response in the cell or block the Receptor and prevent it from working

53
Q

What is the function of the messenger molecule glucagon

A

glucagon is released when there isn’t enough glucose in the blood, it binds to receptors on the liver cells causing the liver to break down stores of glucagon to glucose

54
Q

What is the function of the messenger molecule FSH

A

Fsh is released by the pituitary gland during the menstrual cycle, it binds to the receptors on the cells in the ovaries causing an egg to mature ready for ovulation

55
Q

What is the function of the drug morphine

A

The body produces chemicals called Endorphins to relieve pain. endorphins bind to opioid receptors (Which stop vehicles containing neurotransmitters moving to and fusing with signups membrane therefore less neurotransmitters are released in this case pain signals) in the brain and reduce the transmission of pain signals. morphine is a drug used to relieve pain, it works by binding to the same opioid receptors as endorphins and also triggering a reduction in pain signals

56
Q

What is the function of the drug antihistamines

A

Cell damage causes the release of a chemical called histamines, these bind to receptors on the surface of other cells and cause Inflammation. antihistamines work by blocking histamine receptors on cell surfaces. this prevents histamines from binding to the cell and stops inflammation

57
Q

Function of clostridium botulinum (botox)

A

This is a poison which binds to receptors on muscle cells causing paralysis

58
Q

What does partially permeable mean

A

Allow some molecules through but not others

59
Q

What is the difference between hydrophobic and hydrophilic

A

Hydrophobic repels water hydrophilic attracts water

60
Q

How do drugs work

A

the drug is a complementary shape to the receptor so this means it will bind to the receptor blocking the messenger molecule from doing so preventing the messenger molecule from triggering a response in the cell

61
Q

Why can mutated versions of the receptor not respond to messenger molecules

A

The complementary shape of the site has changed meaning the messenger molecules can no longer bind and are unable to trigger a response in the target cells

62
Q

Why can this specific messenger molecule only produce a response in liver cells

A

The messenger molecule can only bind to receptors with a complementary shape, different cells have different membrane bound receptors, liver cells have the correct receptor for this specific messenger so only liver cells can respond

63
Q

Give an example of what the process of exocytosis Transports

A

Digestive enzymes, hormone, lipid

Bio Mod 2 (10 decks)

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