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A-level Biology > Cell membranes and Transport > Flashcards

Cell membranes and Transport Flashcards

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1
Q

what is the width of the cell membrane

A

7-8 nm

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2
Q

what is the cell membrane made up of

A

phospholipids
proteins
carbohydrates
cholesterol

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3
Q

phospholipid heads are

A

hydrophilic (polar)

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4
Q

what are collectively know as glycocalyx and are formed through glycosylation

A

glycoproteins and glycolipids

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5
Q

where is cholesterol present in cell membrane and what does it control

A

present between phospholipids and helps control membrane fluidity

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6
Q

name the two proteins in cell membranes

A

extrinsic and intrinsic

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7
Q

name the functions of cell membranes

A 
structural support
control of substances
cell-cell recognition
isolate organelles from cyctoplasm 
bio chemical reactions
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8
Q

phospholipids function in cell membranes

A

form a selective bilayer that allows non polar molecules through but prevents passage of charged molecules (polar)

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9
Q

extrinsic protein function

A

associated with one layer only

may act as receptors for hormones

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10
Q

intrinsic proteins function

A

act as channels to allow passage of polar molecules like glucose

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11
Q

carbohydrate side chain function

A

cell to cell recognition
cell adhesion
cell to pathogen interactions

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12
Q

cholesterol function

A

controls membrane fluidity

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13
Q

why is it called the fluid mosaic model

A

fluid - proteins and lipids are able to move around within the membrane

mosaic - made up of lots of component with different size and shape all arranged in a random pattern

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14
Q

which substance moves through cell membranes easier

A

lipid soluble uncharged, non polar substances

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15
Q

how do lipid soluble small uncharged molecules and non polar substances move across a membrane

A

dissolve in hydrophobic phospholipid tails and diffuse across the membrane
eg- oxygen, CO2, vitamin A

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16
Q

how do water soluble polar molecules and charged ions move across a membrane

A

cannot easily diffuse through phospholipids so pass through intrinsic proteins
eg- glucose, amino acids, Na+

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17
Q

what factors affect membrane permeability

A

temperature

organic solvent eg- ethanol/ acetone

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18
Q

which two methods of transport are an active process requiring ATP

A

active transport

bulk transport

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19
Q

rate of diffusion equation

A

surface area x difference in concentration / length of diffusion path

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20
Q

why does temperature increase permeability

A

molecules have more kinetic energy so diffuse more quickly

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21
Q

how do organic solvents affect permeability

A

emulsifies the phospholipids and denature protein making gaps in the membrane meaning it is more porous

22
Q

diffusion

A

the passive movement of a molecule or ion down a concentration gradient from a region of high concentration to a region of low concetration.
The random net movement due to particles kinetic energy

23
Q

rate of diffusion equation

A

surface area x difference in concentration / length of diffusion path

24
Q

what are the 6 factors affecting diffusion rate

A 
Concentration gradient
thickness of surface
surface area
size of molecule 
nature of molcule
temperature
25
Q

facilitated diffusion

A

the passive transfer of polar molecules or charged ions down a concentration gradient, and across the membrane by channel or carrier proteins

26
Q

channel proteins

A

protein molecules with water filled hydrophilic pores. They open depending on the needs of the cell. Ions can pass through these as they are water soluble

27
Q

carrier proteins

A

allow diffusion of larger molecules. A polar molecule attaches to a binding site and changes shape then released into the cell

28
Q

co-transport

A

a type of facilitated diffusion that brings molecules and ions into cells together on the same protein transport molecule.

29
Q

what is an example of a process that involves the uptake of sodium ions and glucose by co-transport

A

absorption in the small intestine (ileum)

30
Q

active transport

A

transport of ions and molecules against the concentration gradient. Uses energy from the hydrolysis of ATP made by the cell in respiration. A carrier protein acts as a pump against the concentration gradient

31
Q

exocytosis

A

large substances leave the cell after being transported through the cyctoplasm in a vesicle from the golgi body which then fuses with the cell membrane to secreate the substance.

32
Q

endocytosis

A

the cell membrane folds around the particle. The folding closes off the link to the outside of the cell. The particle becomes fully trapped in the cell.

33
Q

which type of bulk transport decreases surface area

A

endocytosis

34
Q

osmosis

A

the diffuison of water from an area of high water potential to and area of low water potential across a selectively permeable memebrane.

35
Q

what is the highest value of water potential

A

0kpa

36
Q

hypotonic

A

if water potential of a solution is higher than the solution inside the cell then the water will flow into the cell by osmosis

37
Q

hypertonic

A

if water potential of a solution is lower than the solution inside of the cell then the water will leave the cell by osmosis

38
Q

isotonic

A

if water potential of a solution is the same as a solution inside the cell then there will be no net movement of water

39
Q

water potential

A

the tendency for water to leave a solution or cell by osmosis, measured in kpa

40
Q

what does a solute do to the water potential

A

lowers water potential due to presence of solute molecules

41
Q

explain pressure potential in a plant cell

A

water enters the plant cell by osmosis causing the cytoplasm and vacuole to swell making the cell turgid. The cell wall is ineleastic so outward pressure builds up as the cyctoplams pushes against the cell wall.

42
Q

which value is more negative (lower water potential)

-50 or -100

A

-100

43
Q

water potential equation

A

water potential = solute potential + pressure potential

44
Q

water potential equation in incipient plasmolysis

A

water potential = solute potential

45
Q

incipient plasmolysis

A

when 50% of cells in an experimental sample are plasmolysed

46
Q

explain the process of co-transport

A

there is a concentration gradient for sodium ions to move into the cell
sodium ions and glucose bind to the carrier protein
the carrier protein changes shape and the sodium and glucose are transported to the other side of the membrane
the process moves glucose against its concentration gradient without the use of ATP - this is known as secondary active transport

47
Q

explain the process of active transport

A

the molecule or ion binds to the carrier protein on the outside of the cell membrane
ATP transfers a phosphate group to the carrier protein
the carrier protein changes shape and carries the ion or molecule across the membrane
the molecule or ion is released into the cytoplasm
the carrier protein returns to its original shape

48
Q

why are cells that perform active transport packed with mitochondria

A

active transport uses energy from the hydrolysis of ATP, made by the cell in respiration which takes place in the mitochondria

49
Q

examples of processes involving active transport

A

reabsorption of glucose in kidneys
muscle contraction
nerve impulse transmission
mineral ion uptake in plants

50
Q

examples of processes involving co-transport

A

absorption in the small intestine (ileum)

selective reabsorption of solutes in the proximal convoluted tubule

A-level Biology (9 decks)

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