rp9

Question 1

how to use respirometer to measure rate of aerobic respiration

Answer 1

add set mass of single celled organisms eg yeast to set conc of substrate eg glucose
add buffer to keep ph constant
add them that absorbs co2 eg Naoh
place in water bath at set temp and allow time to equiblirate
measure
measure distance moved by coloured liquid in set time

Question 2

why does liquid move

Answer 2

organisms respire aerobically
take in 02
c02 given out but absorbed by naoh solution
so volume of gas and pressure in container decreases
So fluid in capillary tube moves down a pressure gradient towards
organism

Question 3

why is respirometer apparatus left open for 10 minutes

Answer 3

allow apparatus to equbilrate
allow for overall pressure expansion
allow respiration rate of organism to stabilise

Question 4

explain why apparatus is airtight

Answer 4

prevent air entering or leaving
would change volumes and pressure affecting movement of liquid

Question 5

a more accurate way to measure volume of gas is

Answer 5

a gas syringe

Question 6

describe how respirometer used to measure anaerobic respiration

Answer 6

measures co2 release
repeat experiment as for aerobic but remove chemical that absorbs co2
make conditions anaerobic
eg layer of oil above yeast to stop oxygen diffusing in
add chemical that absorbs o2
leave them for an hour to allow oxygen to be respired and used up

Question 7

explain why liquid moves in anaerobic

Answer 7

yeast anaerobically respires releasing co2
so volume of gas and pressure in container increases
so fluid in capillary tube moves down pressure gradient away from organism

Question 8

Explain why the apparatus is left for
an hour after the culture has
reached a constant temperature.

Answer 8

allow for time for oxygen to be used up and respired

Question 9

how is redox indicate eg methylene blue used to measure rate of respiration

Answer 9

change colour the they accept electrons becoming reduced
take up hydrogen and get reduced

Question 10

using methylene blue to measure rate of respiration method

Answer 10

add set volume of organism like yeast
add set volume of respiratory substrate eg glucose to tubes
add buffer to keep ph constant
place in water bath at set temp and allow it to equilibrate for 5 min
add set vol of methylene blue
shake for set time
record time for colour to disappear in tube

Question 11

examples of variables to control

Answer 11

ph
volume of redox indicator
temp with water bath
vol conc type of respiratory substrate
vol of single celled organisms

Question 12

descrobe control experiment for methylene blue

Answer 12

add methylene blue to inactive or dead yeast
all other conditions the same
shows change is due to respiration in organism

Question 13

why not shake solution tubes containing methylene blue

Answer 13

shaking mixes solution with oxygen
oxidises it causing it to lose electrons
and it would change back to its original blue colour

Question 14

glycosis

Answer 14

Glucose phosphorylated to glucose phosphate
○ Using inorganic phosphates from 2 ATP
2. Hydrolysed to 2 x triose phosphate
3. Oxidised to 2 pyruvate
○ 2 NAD reduced
○ 4 ATP regenerated (net gain of 2)

Question 15

link

Answer 15

Pyruvate oxidised to acetate
○ CO2 produced
○ Reduced NAD produced (picks up H)
2. Acetate combines with coenzyme A, forming Acetyl
Coenzyme

Question 16

krebs

Answer 16

Acetyl coenzyme A (2C) reacts with a
4C molecule
○ Releasing coenzyme A
○ Producing a 6C molecule that
enters the Krebs cycle
2. In a series of oxidation-reduction
reactions, the 4C molecule is
regenerated and:
○ 2 x CO2 lost
○ Coenzymes NAD & FAD reduced
○ Substrate level phosphorylation
(direct transfer of Pi from
intermediate compound to ADP)
→ ATP produced

Question 17

oxidative phosphorylation

Answer 17

1. Reduced NAD/FAD oxidised to release H atoms → split into protons and electrons
   Electrons transferred down electron transfer chain
   ○ By redox reactions
2. Energy released by electrons used in the production of ATP from ADP + Pi (chemiosmotic theory):
   ○ Energy used by electron carriers to actively pump protons from matrix → intermembrane space
   ○ Protons diffuse into matrix down an electrochemical gradient, via ATP synthase (embedded)
   ○ Releasing energy to synthesise ATP from ADP + Pi
3. In matrix at end of ETC, oxygen is final electron acceptor (electrons can’t pass along otherwise)
   ○ So protons, electrons and oxygen combine to form water