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AS- Biology > 2.5- Biological membranes > Flashcards

2.5- Biological membranes Flashcards

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1
Q

What is the role of membranes? (name 3)

A
  • To act as a partially a partially and sometimes selectively permeable membrane between cells and their environments
  • Site of Chemical reactions
  • Sites of cell communication and signalling
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2
Q

What is the function of phospholipids in a cell membrane

A

Phospholipids form the bilayer and are the main component of the surface area

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3
Q

What Is the function of Cholesterol in a cell mambrane?

A

It regulates membrane fluidity and flexibility

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4
Q

What is the function of proteins in cell membranes?

A

carrying out chemical reactions or regulating cross membrane transport

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5
Q

What are the 2 types of proteins in cell membranes?

A

Integral- span the entire membrane

Peripheral- embedded in half of a membrane

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6
Q

What is the function of glycoproteins and glycolipids in cell membranes?

A

can be antigens or receptor molecules

can bind with extracellular signalling molecules such as hormones

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7
Q

An increased temperature leads to the membrane increasing its……………..

A

Fluidity and permeability

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8
Q

Why does an increased temperature increase fluidity and permeability? (Phospholipids)

A

Phospholipids aquire more energy so they move around more

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9
Q

Why does an increased temperature increase fluidity and permeability? (Fatty acids)

A

fatty acids become less compressed

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10
Q

Why does an increased temperature increase fluidity and permeability? (Proteins)

A

proteins can denature at high temperatures reducing their ability to control transport across membranes

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11
Q

Which 3 factors can affect membrane permebility?

A

Increased temperature
Changes in PH - affect the function of proteins in the membrane
Organic solvents such as ethanol can damage a membrane by dissolving lipids held through it

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12
Q

Can you draw the fluid Mosic model?

A

Hmmmmmmmmm

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13
Q

What is the definition of diffusion?

A

The movement of molecules from a region of high concentration to a region of low concentration until the concentrations of the 2 regions are equal.

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14
Q

What 3 factors does the rate of diffusion depend on?

A

Surface area of cell
thickness of membrane
Temperature

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15
Q

i am a small non polar molecule. can i diffuse through a membrane?

A

yes, i can diffuse quickly

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16
Q

I am a small polar molecule. can i diffuse across a membrane?

A

yes, although it will be slower

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17
Q

I am an ion. Can i diffuse across a cell membrane?

A

Noooo, i have to be transported by other methods

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18
Q

I am a large polar molecule. Can i diffuse across a cell membrane??

A

nope, i have to be transported by other methods

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19
Q

Give 3 examples of molecules which can diffuse through a membrane.

A

Oxygen
CO2
Steroids
Fat soluble vitamins

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20
Q

What is the definition of osmosis?

A

the diffusion of water molecules from a region of high concentration to low concentration across a partially permeable membrane

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21
Q

Is osmosis a form of active transport

A

No, osmosis is a specialised form of diffusion.

22
Q

What molecules can facilitated diffusion transport that normal diffusion cant?

A

large and polar molecuses

23
Q

Give 4 examples of molecules that are transported by facilitated diffusion.

A

glucose
fructose
ions
urea

24
Q

is facilitated diffusion an active process?

A

No, it is passive

25
Q

What is needed for facilitated diffusion to occur?

A

Carrier proteins or Channel proteins

26
Q

What are the 3 steps for facilitated diffusion through a carrier protein?

A
  • Molecule binds with carrier proteins molecules on cell surface
  • Protein changes shape and transports molecule through
  • Molecule detaches and protein reverts to its original shape
27
Q

What does the rate of facilitated diffusion depend on?

A
  • Concentration gradient

- Number of channels or transporter proteins that are available

28
Q

What are 3 passive processes which move molecules across membranes?

A

Diffusion
Facilitated diffusion
Osmosis

29
Q

What are 3 active processes that are used to transport molecules across membranes?

A

Active transport
Endocytosis
Exocytosis

30
Q

Why do active processes require energy?

A

They move molecules against their concentration gradient

31
Q

What is endocytosis?

A

the bulk transport of substances into a cell

32
Q

What is exocytosis?

A

The bulk transport of substances out of a cell

33
Q

What to carrier proteins use to transport molecules across membranes?

A

ATP

34
Q

What is endocytosis of liquids called?

A

pinocytosis

35
Q

How does endocytosis work?

A

a vesicle forms around the molecules that have entered the cell, containing them

36
Q

How does exocytosis work?

A

a membrane bound vesicle moves towards the membrane and then fuses together to release the contents of the vesicle into the extracellular environment

37
Q

What is a hypotonic soloution?

A

A soloution where water potential outside the cell is higher than inside

38
Q

What is an isotonic soloution?

A

a soloution where water potential is equal inside and outside the cell

39
Q

What is a hypertonic soloution?

A

a soloution where water potential is higher on the inside of the cell than outside

40
Q

Can plant cells burst?

A

no, they have a cell wall

41
Q

What solution are animal cells put in to burst?

A

a hypotonic one

42
Q

jimmy says that “in an isotonic soloution and a cucumber, no water is moving”
Explain why jimmy is stupid

A

Water will flow in and out at an equal rate

there is no net change in concentrations but water is still moving

43
Q

When an animal cell shrinks, what is it called?

A

crenation

44
Q

When a plant cell shrinks, it becomes……………..

A

plasmolysed

45
Q

Why doesn’t a plant cell collapse when placed in a hyper tonic solution?

A

The cell wall keeps it rigid

46
Q

I am a turgid cell that hasnt burst. What am i?

A

A plant cell in a hypotonic solution

47
Q

How do membranes change when temperature is increased?

A
  • The phospholipids require more energy and move around more so fluidity and permeability increase
  • The way protiens are positioned may differ which can alter rates of reaction
48
Q

How does a temperature decrease affect membrane permeability?

A
  • Saturated fatty acids become compressed

- But unsaturated fatty acids become compressed and push adjacent phospholipid molecules away which maintains fluidity

49
Q

What is the effect of solvents on cell membranes?

A

they damage cell membranes and dissolve lipids

50
Q

What are the units of water potential?

A

kPa

51
Q

What is the highest water potential?

A

0 kPa

52
Q

What is a very low water potential example?

A

-100 kPa

AS- Biology (12 decks)

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