Topic 2 mistakes

Question 1

Use fixed law of diffusion to explain adaptations for effective gas exchange ?

Answer 1

rate of diffusion is proportional to surface area, alveoli in lungs have large surface area

Rate of diffusion is proportional to difference in concentration. Breathing maintains a difference in concentration as well as constant blood flow which maintains concentration gradient

rate of diffusion is inversely proportional to diffusion distance, walls of aveoli and capillaries are one cell thick

rate of diffusion is proportional to diffusion constant, cell membrane are relatively permeable to non polar molecules (?)

Question 2

if a solute does not enter a cell at that means it is what ?

Answer 2

membrane is impenetrable to solute

Question 3

why is the rate of osmosis different in a cell surface membrane and phospholipid bilayer - most basic answer 2 marks

Answer 3

water can move across a phospholipid bilayer Aswell a channel proteins ( simple and or facilitated diffusion )

cell surface membrane is more permeable to water than artificial phospholipid bilayer membrane

Question 4

compare and contrast active transport with diffusion ?

Answer 4

similarities - both molecules move through phospholipid bilayer
In both molecules can move through proteins

differences- active transport requires vesicles where as diffusions does not

Active transport requires energy form ATP where as diffusion is passive

diffuse occurs down the concentration gradient where as active transport is against the concentration gradient

Question 5

compare and contrast exocytosis with endocytosis

Answer 5

both requite vesicular transport

they both requite energy form ATP as active processes

Both transport substances that can’t enter by facilitated or simple diffusion

Differences-

exocytosis requires vesicles for Golgi apparatus fusing with cell surface where as exocytosis involves forming a vesicle

Question 6

use fixed law to explain the adaptations of mammalian gas exchange surfaces

Answer 6

rate of diffusion is proportional to surface area - alveoli have large surface area

rate of diffusions is proportional to difference in surface area/ concentration gradient - breathing and constant blood flow maintains a difference in gas concentrations

rate of diffusion is inversely proportional to diffusion distance - walls of alveoli and capillary are one cell thick

diffusion distance is reduced due to flattened cells forming alveoli and capillary walls

rate of diffusion is proportional to diffusion constant - cell membranes are relatively permeable to non polar gas molecules.

Question 7

using graph describe the effect of temperature on cell membrane permeability ?

Answer 7

increase in temp increase in permeability of cell membrane

is increase in permeability linear ? non linear ? (do not say faster or slower)

Question 8

now explain the effect of temperature on cell membranes

Answer 8

increased kenetic energy resulted in increase molecule movement
reference - phospholipid moving

membranes proteins may become denatured

betalanin/ pigment can escape form cell when cell surface disrupted

Question 9

what factors can make a beetroot practical more reliable

Answer 9

appropriate standardisation of source of beetroot tissue ( strong matches/ small source of beetroot)

washing/ rinsing beetroot thoroughly to remove excess beetroot pigment

water bath to maintain temp / change temperature)

use smaller interval temperatures

reference to calibration of colorimeter

reference to a control variable- time beetroot left in water bath

Question 10

What is the bond between phospholipid elements ?

Question 11

Explain the location of cholesterol in cell membranes ?

Answer 11

cholesterol is a non polar molecule, fatty acid tails are on polar, cholesterol located within the fatty acid walls of cholesterol

Question 12

explain the permeability of cell membranes to each chemical listed:

na+ cl- 10%
glucose 50%
steroid 75%
watr 90%

Answer 12

Ions are polar so pass through a protein channels by facilitated diffusion/ active transport

Glucose is polar (due to multiple hydroxide groups) so passes through protein channels/ carrier proteins by facilitated diffusion

Steroid is non polar can diffuse through membrane/ phospholipid

water is small enough to move by osmosis/ diffusion between phospholipids. it is polar so can also move through proteins

Question 13

Which cell transport mechanism moves small lipid-soluble molecules through the membrane ?

Answer 13

diffusion

Question 14

cells can repair damage to the cell membrane

this involves fusion of parts of the membrane around the edge of the damage

explain why parts of the membrane are able to fuse together to repair damage ?

Answer 14

because phospholipids and proxies can move (are fluid) there for phospholipids/ fatty acids can interact hydrophobically

Question 15

A student kept the ethanol solution at a constant temperature- state 2 other variables to control

Answer 15

variety/ type/ age/ colour of beetroot

length/ SA/ volume of beetroot piece

time taken to wash slices
volume (of samples) removed from solution

use same colorimeter filter