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Biology > Biological Membranes > Flashcards

Biological Membranes Flashcards

1
Q

describe a method using a colorimeter to investigate effect of ethanol conc on permeability of cell membrane

A

-cut 5 small equal beetroot pieces
-prepare 5 solutions of ethanol with conc of 0%, 0.13%, 0.25%, 0.5%, 1%
-place 1 piece of beetroot in each test tube at the same time, start timer
-once timer done, remove beetroot, shake each TT 3 times and take sample from each
-measure absorbance with colorimeter and blue filter
-repeat experiment each time with fresh beetroot pieces and calculate mean absorbance for each conc

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2
Q

describe a method using a colorimeter to investigate effect of temperature on permeability of cell membrane

A

-cut 5 equal beetroot samples
-wash with 100ml DW in WB
-increase T of WB by 10 degrees
-take samples of water 5 mins after reached T
-measure absorbance on colorimeter using blue filter
-repeat experiment 3 times, each with fresh beetroot and calc mean

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3
Q

explain effect of changing solvent conc on permeability of cell membranes

A

effect of water
-water required for bilayer to be maintained
-non polar tails of PL are orientated away from water, forming bilayer with hydrophobic core
-charged phosphate heads interact with water keeping bilayer intact
-when PL can’t interact with water the bilayer can no longer exist (polar heads aren’t attracted to NP)
Effect of organic solvent
-as conc increases around bilayer, its ability to interact with water decreases and bilayer starts to disperse

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4
Q

describe effect of solvent conc on membrane permeability

A

water= polar solvent required to maintain PLB
organic solvents= increase permeability as you increase conc

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5
Q

explain effect of increase T on permeability of cell membranes

A

-Ke increases
-PL vibrate more
-increases average PL separation
-increased permeability as more gaps

-PLB may melt completely
-proteins may denature, leaving gaps in membrane
-therefore permeability will increase

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6
Q

describe effect of increasing T on mebrane permeability

A

increasing T increases membrane permeability

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7
Q

explain how binding of a molecule to a glycoprotein can cause effects within a cell

A

cell signalling
-chemical messenger molecule moves around body, if able to fit the protein receptor binding site, it will bind
-chem reaction is caused- signal transduction which causes a chem reaction within a cell, altering activity

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8
Q

explain importance of membrane bound proteins in chem reactions

A

-enzymes can be held in correct location by attachment to membrane
-kept in place where optimum conditions are
-positioned so they can access substrates

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9
Q

explain effect of cholesterol on fluidity and stability of membranes

A

-chol positioned between PL in bilayer, preventing aligning too closely & solidifying
-hydrophillic end interacts with heads and hydrophobic end interacts with tails, pulling them together & stabilising bilayer

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10
Q

cell adhesion definition

A

cells join together to form tight junctions in certain tissues

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11
Q

state roles of different proteins in membrane

A

-receptors in cell signalling (glycoproteins)
-cell adhesion (glycoproteins)
-enzymes being kept in place attached to membrane
-transport proteins (carrier/channel)

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12
Q

state role of glycolipids in membrane

A

cell recognition- act as antigens, often related to immune system

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13
Q

state role of glycoproteins in membrane

A

cell adhesion
cell signalling (receptors)

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14
Q

state role of cholesterol in membrane

A

maintain membrane fluidity
stabilising bilayer

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15
Q

role of phospholipids in membrane

A

-main component of cell surface membranes (membrane formation)
-act as a barrier between contents of cell and exterior (hydrophobic barrier)

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16
Q

receptor protein/glycoprotein definition

A

proteins that bind to a specific molecule, triggering a chemical reaction

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17
Q

extrinsic protein definition

A

peripheral proteins that are present in one side of the bilayer

-amino acids with hydrophilic R groups on outer surfaces and interact with polar heads of the membrane or with intrinsic proteins

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18
Q

intrinsic protein definition

A

transmembrane proteins that are embedded through both layers of a membrane
-amino acids with hydrophobic R groups on external surfaces which interact with hydrophobic core of membrane

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19
Q

carrier protein definition

A

specific and reversible protein that acts as an enzyme with a region that binds to a molecule to aid transport by facilitated diffusion

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20
Q

channel protein definition

A

hydrophilic channel that allows passive movement of polar molecules and ions down a conc gradient through membranes

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21
Q

glycolipid definition

A

cell surface membrane lipids with attached carb molecules of varying lengths and shapes

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22
Q

cholesterol definition

A

lipid consisting of 4 carbon rings (hydrophobic) with a hydroxyl group (hydrophilic end)

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23
Q

phospholipid definition

A

lipids consisting of 2 fatty acids, a glycerol unit, and phosphate group

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24
Q

glycoprotein definition

A

membrane proteins with attached carbohydrate molecules of varying lengths and shapes

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25
Q

fluid meaning in FMM

A

membranes aren’t solid (molecules=weakly held in place)
-because PL are weakly attracted and can change places

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26
Q

mosaic meaning in FMM

A

phosphates and embedded proteins form a tile pattern when viewed from above

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27
Q

phospholipid bilayer definition

A

arrangement of PL found in cell membranes
-hydrophilic phosphate heads from both inner & outer surface of a membrane sandwich the fatty acid tails to form a hydrophobic core

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28
Q

cell signalling definition

A

complex system of intercellular communication

29
Q

partially permeable definition

A

membrane that allows some substances to cross but not others

29
Q

partially permeable definition

A

membrane that allows some substances to cross but not others

30
Q

define compartmentalisation and explain useful

A

formation of separate membrane-bound areas in a cell
-metabolism inc many different & often incompatible reactions
-containing reactions in separate parts of cell allows the specific optimum conditions to be met and maintained for each compartment allowing for different reactions to occur.

31
Q

state 5/6 roles of membranes

A

-partially permeable barrier, only allows select substances through (compartmentalisation)
-cell signalling
-anchoring the cytoskeletal framework
-cell to cell recognition
-endocytosis and exocytosis

32
Q

equation for straight line

A

y=mx+c

33
Q

define relative uncertainty

A

ratio of absolute uncertainty to reported value

34
Q

define absolute uncertainty

A

number which when combined with the reported value gives the range of true values

35
Q

haemolysis definition

A

rupture and destruction of red blood cells

36
Q

cytolysis definition

A

when a cell bursts and releases contents due to the great influx of water into cell
in hypotonic sol

37
Q

define turgid

A

plant cell swollen from water uptake, cell wall prevents bursting

38
Q

define crenation

A

contraction of a cell after exposure to a hypertonic sol

39
Q

define protoplast

A

contents of a cell within the cell membrane

40
Q

define plasmolysis

A

when the plant cell membrane is pulled away from cell wall
occurs when cell is in a too hypertonic sol

41
Q

state water potential of pure water

A

0 kPa (at standard T P)

42
Q

why can’t water potential have a pos value

A

presents of solute in water lowers water potential below 0
-more solute=more negative

43
Q

define water potential

A

pressure exerted by water molecules as they collide with a membrane or container

Pa or kPa

44
Q

define solution

A

liquid mixture in which the solute is distributed evenly within the solvent

45
Q

define solution

A

liquid mixture in which the solute is distributed evenly within the solvent

46
Q

results expected in an investigation rate of diffusion affected by T

A

RoD increase as T increases
greater Ke
higher average speed of particles
diffuse faster

47
Q

results expected in an investigation rate of diffusion affected by SA

A

RoD increase as you increase SA
greater surface for particles to collide and enter/exit

48
Q

results expected in an investigation rate of diffusion affected by SA

A

RoD increase as you increase SA
greater surface for particles to collide and enter/exit

49
Q

why can steroid hormones easily cross membrane by simple diffusion

A

lipid soluble=hydrophobic
not repelled by hydrophobic interior therefore don’t need carrier proteins

50
Q

why is it easier for oxygen molecule to diffuse across membrane rather than water

A

D across membranes involves particles passing through PLB
oxygen is small and NP, won’t be repelled by hydrophobic interior and pass through easily

51
Q

which transport mechanisms require an input of energy from ATP

A

AT (by carrier proteins)
Cytosis (bulk transport, exocytosis, endocytosis)

52
Q

which transport mechanisms require an input of energy from ATP

A

AT (by carrier proteins)
Cytosis (bulk transport, exocytosis, endocytosis)

53
Q

list factors affecting rate of diffusion of a molecule

A

SA
Conc difference
Distance
T
Permeability

54
Q

which types of molecues can move across membrane by facilitated diffusion

A

carrier proteins= large molecules e.g glucose

channel proteins= charged/polar particles (hydrophilic/water soluble)e.g sodium ions

55
Q

which types of molecules can move across membrane by simple diffusion

A

small, NP and uncharged molecules
lipid soluble

56
Q

phagocytosis definition

A

endocytosis of solids

57
Q

pinocytosis definition

A

endocytosis of liquids

58
Q

define exocytosis

A

bulk transport of materials out of cells where vesicles containing the material fuse with the cell surface membrane and contents released outside of cell

59
Q

define endocytosis

A

bulk transport of materials into cells via invagination of the cell surface membrane forming a vesicle

60
Q

define endocytosis

A

bulk transport of materials into cells via invagination of the cell surface membrane forming a vesicle

61
Q

define active transport

A

movement of particles across a plasma membrane against a conc gradient. ATP required

62
Q

define active transport

A

movement of particles across a plasma membrane against a conc gradient. ATP required

63
Q

define passive transport

A

not require ATP

64
Q

osmosis definition

A

net movement of water from a sol of higher to lower water potential through a PPM
example of passive transport (no ATP)

65
Q

define facilitated diffusion

A

diffusion across a PPM with the assistance of membrane proteins (carrier/channel)
passive process (no ATP)

66
Q

define simple diffusion

A

diffusion across a PPM without assistance of membrane proteins
passive process (no ATP)

67
Q

define simple diffusion

A

diffusion across a PPM without assistance of membrane proteins
passive process (no ATP)

68
Q

define diffusion

A

net movement of particles from region of high conc to lower conc (down conc gradient) without ATP

Biology (13 decks)

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