respiration Flashcards
why is respiration important?
Glucose contains energy stored in the bonds but glucose is not suitable as an immediate energy source in
cells.
Respiration is the process by which the energy in glucose is used to form ATP which is the immediate energy
source.
chemical equation of respiration
C6H12O6 + 6O2–> 6CO2 + 6H2O
name the 2 ways ATP is generated in respiration
substrate level phosphorylation- ATP generated directly through respiration – occurs in glycolysis and Krebs
cycle.
oxidative phosphorylation- ATP generated from the chemical energy released from a reduced coenzyme –
occurs in electron transport chain.
describe glycolysis + where it happens
occurs in cytoplasm
1. Glucose is phosphorylated to GP to make it more reactive via the hydrolysis of 2ATP to provide the 2 phosphates. The GP then split into two triose phosphates
2. Triose phosphates are then oxidised to pyruvate, involving the loss of H which reduces the coenzyme NAD to NADH.
3. 2 ATP are produced by substrate level phosphorylation for each molecule of triose phosphate, so overall glycolysis gives a net gain of 2ATP.
Products for each glucose molecule: Net gain of 2 ATP,
* 2 reduced NAD (NADH)
* 2 molecules of pyruvate
Exam tip: Coenzymes are NOT enzymes or proteins. They just help out enzymes
describe the link reaction and where it occurs
occurs in the mitochondrial matrix after pyruvate is actively transported thru the inner and outer membranes.
1. Pyruvate (3C) is decarboxylated causing it to lose a C in the form of CO2.
2. Pyruvate is oxidised, and the removed H is added to NAD to form NADH.
3. These reactions forms acetate (2C).
4. Coenzyme A reacts with the acetate to form acetyl coenzymeA (2C)
Products: 2 CO2, 2 NADH, 2 acetyl coenzyme A
describe the krebs cycle and where it happens
occurs in the mitochondrial matrix
1. 2C acetyl coenzymeA reacts with a 4C compound to form a 6C compound, which becomes a 5C compound as it loses a CO2 by decarboxylation and is oxidised to produce NADH from NAD.
2. 5C compound becomes a 4C compound as it loses another CO2 by decarboxylation and is oxidised to produce 2 reduced NAD from 2 NAD and reduced FAD from FAD. ATP is formed from
ADP + Pi by substrate level phosphorylation.
4. The 4C compound reacts again with acetyl Coenzyme A and the cycle starts again- happens twice for each glucose molecule.
Products: 2 CO2, ATP, 3 NADH + 1 FADH
describe oxidative phosphorylation + where it happens
occurs on inner mitochondrial membrane
1. The reduced coenzymes NADH and FADH are oxidised losing hydrogen which dissociates
into a H+ and an e-
2. The electrons pass down a series of electron carriers on the inner mitochondrial membrane in a series
of redox reactions.
3. As the electrons pass along the electron transport chain they lose energy, which is used to pump the
protons through the inner membrane into the intermembrane space, forming a proton gradient. Some energy is also lost as heat.
4. The protons diffuse back through the inner membrane, down their electrochemical gradient, via ATP synthase enzymes embedded in the inner membrane- This is chemiosmosis.
5. As the protons pass through, they release energy to form ATP from condensation of ADP + Pi.
6. The electrons and H+ combine with oxygen to form water. Oxygen is the terminal electron acceptor.
overall ATP production in aerobic respiration
38 ATP- 34 from oxidative phosphorylation, 2 each from glycolysis + krebs cycle
how can lipids be respired to release energy for ATP production?
- Lipids are hydrolysed to fatty acids and glycerol- the glycerol being phosphorylated and converted to Triose phosphate which enters glycolysis.
- The fatty acids are hydrolysed into 2C fragments which are converted to acetyl coenzyme A which enter
the Krebs cycle. - The oxidation of these lipid products yields many NADH and FADH molecules which can be fed into the electron transport chain to produce large amounts of ATP.
how can proteins be respired to release energy for ATP production?
- The protein is hydrolysed to amino acids.
- The amine group is removed from the amino acids (deamination) and products enter respiration at
different points:
a. 3C molecules are converted
to pyruvate
b. 4C and 5C molecules are
converted to Krebs cycle
intermediates.
why does anaerobic respiration only use glycolysis?
no oxygen so Link reaction, Krebs cycle and oxidative phosphorylation stop as there is no oxygen to act as the terminal electron acceptor.
* Glycolysis does not require oxygen but NAD must be regenerated from reduced NAD for glycolysis to
continue.
how does anaerobic respiration occur in animals?
glycolysis occurs as usual, forming pyruvate and 2 ATP net gain, and the H from the reduced NAD reduces pyruvate to form lactic acid
how does anaerobic respiration occur in plants + fungi?
glycolysis occurs as usual, forming pyruvate + 2 ATP net gain, and the H from reduced NAD reduces pyruvate to form ethanol and carbon
dioxide.
how can lactic acid be removed from muscles?
Oxygen can be used to oxidise the lactic acid back to pyruvate which can enter the
link reaction and continue aerobic respiration (in the presence of oxygen).
why is aerobic respiration much preferred over anaerobic in terms of ATP producton?
aerobic produces 38 ATP from 1 glucose, anaerobic produces 2 ATP.
draw apparatus + describe how rate of ANAEROBIC respiration can be measured
draw apparatus + describe how rate of AEROBIC respiration can be measured
uses a manometer
1. As the seeds aerobically respire they take in
O2 and produce CO2
2. The CO2 is absorbed by the potassium
hydroxide, reducing the pressure and volume in
the flask causing the coloured liquid to move
towards the seeds.
3. The distance the liquid moves in a set time determines the rate- by measuring the radius of the tube, the volume of gas used can be calculated (πr2 x distance).
6. By measuring the mass of the seeds this can work out the rate per gram.
