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Year 1 biology > 2.1.5 biological membranes > Flashcards

2.1.5 biological membranes Flashcards

1
Q

what is a cell membrane
2.1.5(a)

A

A cell membrane is a membrane anywhere in or around a cell

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2
Q

what is a cell surface membrane or plasma membrane
2.1.5(a)

A

The plasma membrane, also known as the cell surface membrane, is the membrane around the outside of a cell

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3
Q

what are the 3 roles of membranes
2.1.5(a)

A

compartmentalisation
chemical reactions
cell signaling

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4
Q

what is compartmentalization
2.1.5(a)

A

a cell is physically separated from its environment
it allows different areas inside the cell to maintain different internal conditions
this allows different reactions to take place in different structures

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5
Q

how do chemical reactions take place in cell membranes
2.1.5(a)

A

Some chemical reactions take place using enzymes that are embedded in cell membranes

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6
Q

how do cells communicate with each other-cell signaling
2.1.5(a)

A

The cell surface membrane contains receptors that allow cells to communicate with each other. Cells communicate with each other by releasing chemical signals These will only have an effect on cells that have the complementary receptor embedded in their cell surface membrane.

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7
Q

why is the fluid mosaic structure known as a fluid
2.1.5(b)

A

as the phospholipids are free to move from side to side

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8
Q

why is the fluid mosaic structure known as a mosaic
2.1.5(b)

A

as it contains a variety of different structures
eg-phospholipids, cholesterol and proteins

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9
Q

phospholipid part of fluid mosaic structure
2.1.5(b)

A

hydrophilic heads point outwards
hydrophobic tails point inwards

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10
Q

role of cholesterol
2.1.5(b)

A

for stability/flexibility

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11
Q

what is a glycolipid
2.1.5(b)

A

carbohydrate chain attached to a lipid

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12
Q

what is a glycoprotein
2.1.5(b)

A

carbohydrate chain attached to a protein

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13
Q

what is the role of glycolipid/protein
2.1.5(b)

A

cell signalling
act as antigens
receptors
cell adhesion(where cells bind to each other to create new structures)

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14
Q

what is the role of glycolipid/protein in identifying an unknown hormone
2.1.5(b)

A

since they act as receptors so are complementary and specific to that hormone

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15
Q

what are intrinsic proteins + examples
2.1.5(b)

A

embedded throughout both layers of a membrane. They have amino acids with hydrophobic r groups on the outside
eg-glycoprotein + glycolipid

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16
Q

what are extrinsic proteins + examples
2.1.5(b)

A

present in one side of the bilayer. They have amino acids with hydrophillic r groups on the outside
eg-cholestrol

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17
Q

what happens to the cell membrane when temperature decreases
2.1.5(c)

A

-membrane fluidity decreases as phospholipids move closer together
-each phospholipid has one unsaturated fatty acid tail which helps lower the temperature so that the membrane becomes solid
-cholesterol helps maintain the fluidity by pushing phospholipids apart

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18
Q

what happens if the cell freezes
2.1.5(c)

A

ice crystals form in the cytoplasm and piece the plasma membrane so fluidity increases

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19
Q

what happens when the temperature of the cell increases
2.1.5(c)

A

-phospholipids gain kinetic energy and move around more which causes gaps to appear in the phospholipids
-permeability of the membrane increases
-cholesterol helps maintain the fluidity in animal cell membrane by pulling the phospholipids together
-proteins in the membrane will denature

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20
Q

what is the effect of a non-polar solvent on the permeability of cell membranes
2.1.5(c)

A

non-polar solvents dissolve the phospholipids so as the concentration of non-polar solvent increase so does the permeability of the membrane

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21
Q

why cant the pigment betalain not leave the beetroot cell
2.1.5(c)

A

as it is too large so cannot leave the cell
it will leak out into the surrounding solution where the plasma membrane is disrupted

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22
Q

what type of process is diffusion
2.1.5(d)

A

passive as it does not require ATP

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23
Q

what is diffusion
2.1.5(d)

A

net movement of molecules down a concentration gradient
(from high to low)

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24
Q

what happens when a dynamic equilibrium is reached
2.1.5(d)

A

Eventually a dynamic equilibrium will be reached, where the molecules are still moving all the time, but there is no concentration gradient so there is no net movement of particles

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25
Q

which molecules can cross the cell membrane by simple diffusion
2.1.5(d)

A

small
non-polar
eg-co2 or o2

26
Q

why can these molecules cross by simple diffusion
2.1.5(d)

A

as they can dissolve in the phospholipid bilayer so diffuse directly across it

27
Q

what is facilitated diffusion
2.1.5(d)

A

Facilitated diffusion is the diffusion of molecules across a membrane using a transport protein. (Both carrier and channel proteins can carry out facilitated diffusion). No ATP is required

28
Q

which molecules cross the membrane by facilitated diffusion and why
2.1.5(d)

A

Any molecule that is polar or charged will not be soluble in the phospholipid bilayer because they cannot interact with the fatty acid tails of the phospholipids.
However, some of these molecules are essential for the function of a cell e.g. many inorganic ions such as Ca2+ or NO3-, or molecules like glucose which are both polar and also too large to cross the membrane by simple diffusion.

29
Q

what are channel proteins
2.1.5(d)

A

Channel proteins are intrinsic proteins that span the membrane.

30
Q

how do channel proteins allow polar or charged molecules to diffuse through them
2.1.5(d)

A

They have a pore running through the middle, which is lined with hydrophilic amino acids. This allows the pore to have an aqueous environment that polar and charged molecules can diffuse through.

31
Q

what are carrier proteins
2.1.5(d)

A

are also intrinsic proteins

32
Q

how to carrier proteins transport molecules
2.1.5(d)

A

When the molecule to be transported binds to them, they undergo a conformational change in shape, which moves the molecule from one side of the membrane to the other

33
Q

what is active transport
2.1.5(d)

A

movement of molecules or ions into or out of a cell from a low to high concentration

34
Q

what type of proteins does active transport involve
2.1.5(d)

A

carrier proteins

35
Q

how do you get the energy from active transport
2.1.5(d)

A

To do this, energy from the hydrolysis of ATP is needed. This type of transport is active, rather than passive, and so it is called active transport

36
Q

how are molecules transported from one side to another in active transport
2.1.5(d)

A

· The molecule to be transported binds to its carrier protein

· A molecule of ATP also binds to the carrier protein

· The carrier protein hydrolyses ATP to ADP + Pi and energy is released

· The energy causes a conformational change to the shape of the carrier protein

· This transports the molecule from one side of the membrane to the other

37
Q

what is bulk transport
2.1.5(d)

A

its another form of active transport
they involve the movement of large molecules too large to be moved through channel and carrier proteins so they are moved into and out of cells by bulk transport

38
Q

what are the two types of bulk transport
2.1.5(d)

A

endocytosis
exocytosis
-requires ATP

39
Q

how does exocytosis occur
2.1.5(d)

A
  1. the molecule to be transported is packaged into secretory vesicles
  2. these bind to motor proteins on the microtubule and are taken via the microtubule track to the plasma membrane
  3. the movement of vesicles along the membrane requires ATP
  4. the vesicle membrane fuses with the plasma membrane and the contents are released to the outside
40
Q

how does endocytosis occur
2.1.5(d)

A
  1. a section of the plasma membrane extends and surrounds the particle bringing it inside the cell enclosed in a vesicle
  2. the change in the cell membrane involves microfilaments
    the movement of the cell once its inside the vesicle involves microtubules
41
Q

what is visking tubing
2.1.5(d)

A

It is an artificial partially permeable membrane that allows small molecules to pass through by simple diffusion but not large ones.

42
Q

what cant you use visking tubing to model
2.1.5(d)

A

Obviously Visking tubing isn’t alive so doesn’t contain any transport proteins, so you can’t use it to model facilitated diffusion of large molecules, active transport, or bulk transport.

43
Q

what is osmosis
2.1.5(e)

A

osmosis is the diffusion of water molecules across a partially permeable membrane from a high water potential to a low water potential

44
Q

what is water potential and what is it measured in
2.1.5(e)

A

water potential is the measure of the potential energy of water
Kpa

45
Q

what happens if water molecules are hydrogen bonded to solutes
2.1.5(e)

A

if water molecules are hydrogen bonded to solutes they cant move about as easily so have lower water potential

46
Q

what is the water potential of pure distilled water
2.1.5(e)

A

it has the highest possible water potential of 0

47
Q

what does it mean if a solution is more concentrated
2.1.5(e)

A

more concentrated=more solutes=more negative water potential
so lower water potential

48
Q

what happens when animal cells are placed in a solution with a more negative water potential than the cytoplasm
2.1.5(e)

A

water moves out of the cell by osmosis and the cell becomes crenated

49
Q

what happens when animal cells are placed in a solution with a less negative value than the cytoplasm
2.1.5(e)

A

water moves into the cell by osmosis and the cell will eventually lyse (burst) a process known as cytolysis

50
Q

what happens when plant cells are placed in a solution with a more negative water potential than the cytoplasm
2.1.5(e)

A

water moves out of the cell and the plant cell has became plasmolysed
during plasmolysis the plasma membrane peels away from the cell wall
the cell hasn’t burst yet

51
Q

what happens when plant cells are placed in a solution with a less negative value than the cytoplasm
2.1.5(e)

A

water moves into the plant eg-vacuole and turgor pressure is exerted against the cell wall. turgid cells help support the plant

52
Q

what happens when plant cells are placed in a solution with a equal water potential
2.1.5(e)

A

there is no net movement of water
the cell if flaccid and is in a state called incipient plasmolysis
this is where plasmolysis is just starting and is reversible

53
Q

how can you observe crenation and plasmolysis
2.1.5(e)

A

using cells that naturally contain pigment

54
Q

experiment for calculating change in mass
2.1.5(e)

A
  1. cut pieces of plant tissue with equal surface area and shape and soak them in different solute concentrations and record final mass
    2.water moving out=mass decreased
    water moves in=mass increased
  2. do many repeats and calculate a mean
  3. the mean solute concentration is the one that gave a 0% change in mass
55
Q

what is the equation for percentage change
2.1.5(e)

A

(final/initial)-1)) x 100

56
Q

what is uncertainty
2.1.5(e)

A

the resolution of the equipment used

57
Q

what is the equation for percentage uncertainty
2.1.5(e)

A

maximum error x number of readings/measurement taken x 100
Max
Never
made
takos

58
Q

what is the maximum error for digital equipment
2.1.5(e)

A

resolution

59
Q

what is the maximum error for analogue equipment
2.1.5(e)

A

resolution/2

60
Q

what is hypertonic point
isotonic point
hypotonic point
2.1.5(c)

A

hypertonic-when more water moves out than in
isotonic-when the same amount of water moves out than in
hypotonic-when more water moves in that out

Year 1 biology (25 decks)

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