membranes

Question 1

give evidence for actie transport (2)

( transprot of dye into yeast cells

Answer 1

state the obvious

at high temperature stain not held in cells ;

at high temperature enzymes denatured so no ATP for active transport (of stain

Question 2

suggest why some cells did not stain blue at 20 degres

Answer 2

no, (metabolic) energy / ATP, to take up stain ;

Question 3

higher temp =

Answer 3

more fluid membrane, membrane structure disrupted so no fluid taken up

Question 4

Explain why the stained yeast cells lost their colour at higher temperatures.

Answer 4

membrane permeable (to stain) ; methylene blue, leaked out of cells / released to solution

; by diffusion / down concentration gradient

Question 5

how to increase reliability and accuracy (2)

Answer 5

accuracy take readings at intermediate temperatures (between 50 °C – 70 °C) ;

reliability take more, readings at each temperature / repetitions ;

Question 6

function of glycoproteins (4)

Answer 6

(acting as) antigens ;

identification / recognition, (of cells) as, self / non-self / AW ; 3 cell signalling / described

receptor / binding site, for, hormone / (chemical) signal /(medicinal / named) drugs ;#

ref. to receptor / binding site / trigger, on transport proteins / 6 cell adhesion / to hold cells together (in a tissue) ;#

attach to water molecules (to stabilise membrane / cell) ;

Question 7

note: things stuck between the inside of the membrane are…

Answer 7

cholestrol

Question 8

function of glycoprotein + bilayer respectively

Answer 8

allow communication across membrane OR allow, polar / charged, particles to pass through membrane

; to act as a barrier (to, polar / charged, particles) / select what enters or leaves cell ;

Question 9

Explain what is meant by the term cell signalling

Answer 9

communication between cells / AW ;

cell, recognition / identification ;

Question 10

Explain how a glycoprotein can act as a receptor.

Answer 10

(receptor) specific shape / described ;

complementary to (shape of), trigger

Question 11

betroot is placed in water of vaarying temperatures, higher temperature causesd more pigment to leak out, why ? (2 )

Answer 11

cell surface / plasma, membrane damaged

; pigment, released / leaks out

Question 12

beetroot experiment, what couldve been improved? (3)

Answer 12

more samples at each temperature

; same / fixed, volume of water ;

all samples same, size / surface area ; ref to further cutting to increase surface area ;

pieces, rinsed / blotted, after cutting

; more (intermediate) temperatures ;

same beetroot used / same part of beetroot used ;

Question 13

note : when a plant is placed in sugar solution (3)

Answer 13

its membrane pulls away fro mteh cell wall

state the OBVIOUS

water moves out of cell ; by osmosis

; cell has, higher / greater / less negative, water potential (than surrounding solution) /

(water moves) down water potential gradient/from high to low water potential ;

Question 14

How do large substances and polar substances enter the cell membrane ?

Answer 14

large substances (using), transport / carrier, proteins ; endocytosis / phagocytosis / described ;

polar substances through, pore / channel, proteins ; (using), transport / carrier, proteins ;

Question 15

suggest why there are tiny holes in bark but not in animals (2)

Answer 15

allow oxygen to reach, cells / tissues (under bark)

; for (aerobic) respiration ;

animals transport oxygen in, blood / circulation / transport system ;

plants do not transport (much) oxygen in transport system ;