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biology module 2 > biological membranes > Flashcards

biological membranes Flashcards

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1
Q

describe the structure of a phospholipid

A

phosphate head- soluble in water, hydrophilic and polar
fatty acid tails- insoluble, hydrophobic and non-polar

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2
Q

give 3 roles of cell membranes

A

barrier between internal and external environment
location of chemical reactions
protection

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3
Q

why hydrophobic molecules (e.g. steroids) pass through the membrane easily

A

phospholipid bilayer is hydrophobic

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4
Q

why can water molecules pass through easily even though they are polar

A

they are extremely small

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5
Q

why does cholesterol increase the strength of the cell surface membrane

A

polar, hydrophilic group attracts polar phosphate heads in the phospholipids
non-polar, hydrophobic groups attracts non-polar fatty acid tails in the phospholipids

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6
Q

give 2 advantages of cholesterol

A

maintains fluidity of membrane
maintains strength
reduces the movement of water soluble chemicals

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7
Q

why is it called the fluid mosaic model

A

fluid- phospholipids can move around (flexible and can change shape)
mosaic- arrangements of proteins vary

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8
Q

what are intrinsic proteins

A

embedded in the membrane from one side to the other

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9
Q

how are intrinsic proteins hydrophobic

A

they have hydrophobic amino acid groups on the outside surface of the protein which interact with the hydrophobic fatty acid tails

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10
Q

what are the 2 types of intrinsic proteins

A

channel proteins
carrier proteins

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11
Q

what is the role of channel proteins

A

allow water soluble molecules and ions to diffuse through

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12
Q

why do channel proteins allow water soluble molecules to diffuse through

A

the central pore is lined with hydrophilic amino acids

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13
Q

what is the role of carrier proteins

A

they change tertiary shape or position to transfer ions or molecules from one side of the membrane to another side

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14
Q

give 3 roles of extrinsic proteins

A

structural role
act as enzymes
receptors (e.g. hormones)

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15
Q

how are extrinsic proteins different to intrinsic proteins

A

extrinsic don’t span the membrane whereas intrinsic proteins do

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16
Q

what are glycoproteins

A

carbohydrate molecule attached to the protein

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17
Q

give 3 roles of glycoproteins

A

allow cells to attach to each other (to make tissues)
present antigens
receptors for hormones

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18
Q

what are glycolipids

A

carbohydrate molecule attached to the phospholipid

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19
Q

give 3 roles of glycolipids

A

antigens
recognition

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20
Q

define diffusion

A

the net movement of molecules from a region of higher concentration to a region of lower concentration down a concentration gradient

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21
Q

why is diffusion a passive process

A

no metabolic energy is required to take place

22
Q

give 6 factors that affect the rate of diffusion

A

concentration gradient
particle size/charge
temperature
surface area
distance
presence of carrier/channel proteins

23
Q

why does particle charge affect the rate of diffusion

A

ions with a charge will not pass through the membrane due to the hydrophobic core

24
Q

why does temperature affect the rate of diffusion

A

particles have more kinetic energy

25
Q

what happens in facilitated diffusion

A

hydrophilic substances pass through the cell membrane through intrinsic proteins (carrier and channel proteins)

26
Q

give 2 key facts about protein channel

A

they are selective of the chemical it passes through
some are constantly open and others open via a trigger

27
Q

is facilitated diffusion passive?

A

yes

28
Q

what protein is used in active transport

A

carrier proteins

29
Q

define active transport

A

the net movement of molecules from a region of low concentration to a region of high concentration against a concentration gradient

30
Q

is active transport passive

A

no

31
Q

how is metabolic energy is required

A

ATP

32
Q

how does active transport work

A

molecule attaches to a receptor site on a carrier protein
ATP undergoes hydrolysis creating ADP and phosphate ATP binds to the carrier protein causing it to change shape
the changing of shape causes it to transport the molecule so it can leave via the other end of the membrane where it is released

33
Q

what are product after ATP is hydrolysed

A

ADP and phosphate

34
Q

why do we find a lot of mitochondria in cells that perform a lot of active transport

A

active transport uses a lot of ATP

35
Q

define osmosis

A

the movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane

36
Q

what water potential is pure water

A

0

37
Q

what is the unit of water potential

A

kPa

38
Q

what is water potential a measure of

A

pressure

39
Q

what is the highest possible water potential

A

0

40
Q

define hypertonic

A

lower solute concentration in the inside than on the outside, causing water to leave the cell to a higher concentration of water

41
Q

what can hypertonic lead to

A

plasmolysis (shrivelled up)

42
Q

define hypotonic

A

higher solute concentration in the inside than the outside, water enters cells where there is a higher concentration of water

43
Q

what can hypotonic lead to

A

cytolysis

44
Q

define isotonic

A

equilibrium

45
Q

what do both endocytosis and exocytosis transfer

A

large quantity of material (bulk transport)

46
Q

what is phagocytosis

A

when solid materials are taken in by endocytosis

47
Q

what is pinocytosis

A

when liquid materials are taken in by endocytosis

48
Q

what is endocytosis

A

material into the cell

49
Q

what is exocytosis

A

material out of a cell

50
Q

are endocytosis and exocytosis passive

A

no- they require energy

biology module 2 (10 decks)

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