Module 5: Respiration Flashcards
State the function of mitochondria
Site of aerobic respiration
What is structure and function of different parts of the mitochondria
Outer membrane: compartmentalisation
Inner membrane: contains proteins for electron transport chain
Cristae: folded to increase surface area for oxidative phosphorylation
Inter membrane Space: helps with storing protons for ATP synthesis
Matrix: contains enzymes for link and Krebs reactions and mitochondrial DNA
- What is an co enzyme
2. What are the co enzymes used in respiration
Co enzyme: molecule that aids the function of an enzyme by transferring chemical group from one molecule to another
- NAD, FAD, coenzyme A
State the 4 stages of aerobic respiration
- Glycosis
- Link reaction
- Krebs cycle
- Oxidative phosphorylation
Describe the first stage of aerobic respiration (glycolysis)
-Happens in cytoplasm
- Glucose has two phosphate groups added to it from 2 ATP molecules which males hexose bisphosphate
- Splits into two so it becomes triosr phosphate
- Another phosphate group is added to make triose bisphophate
- Then triose bisphosphate is oxidised and is converted into pyruvate, NAD becomes reduced NAD
And ADP is phosphorylated and becomes ATP
What is substrate level phosphorylation
When ATP is produced without use of electron transport chain and ATP synthase. ADP is is phosphorylated by an unstable intermediate to form ATP
What happens to the products of glycosis
Products
2x pyruvate-> link and Krebs reaction
2 reduced NAD -> to oxidative phosphorylation
2 ATP (net gain) because we use to at the start (used for energy)
Describe what happens in the link reaction
- Pyruvate transported into matrix of mitochondria
- Pyruvate is decarboyliated (one Carbon atom is removed in the form of CO2
- NAD is reduced to reduced NAD as it gains a hydrogen from pyruvate
- This changes pyruvate into acetate
- Acetate is combined with co enzyme A to form acetyl co enzyme A
What happens to the products of the link reaction
2x Acetyl CoA- Krebs cycle
2x Carbon dioxide - released as waste product
2 reduced NAD- to oxidative phosphorylation
Describe what happens in the Krebs cycle
- acetyl CoA (2 carbon) from link reaction combines with oxaloacetate (4 carbon) to form citrate (6 carbon) this is catalysed by citrate synthese
- Citrate (6) is converted into a 5c by the removal of Carbon dioxide through carbon dioxide decarboxylation
- Dehyrodegination also occurs and hydrogen produced reduced NAD
- This converts the 5c molecule into a 4c molecule
- which creates reduced FAD, 2x reduced NAD, and ATP which is produced by substrate level phosphorylation
What happens to the products in the Krebs cycle
Co enzyme A- reused in next link reaction
Oxaloacetate: regenerated for next Krebs cycle
4 Carbon dioxide: released as waste
6 reduced NAD: to oxidative phosphorylation
2 reduced FAD to oxidative phosphorylation
This is for both Krebs cycles because we have how acetyl CoA, for one it would be half
Describe what happens in oxidative phosphorylation
- Hydrogen atoms are realesed from reduced NAD and reduced FAD
- Hydrogen then splits into hydrogen ions and electrons
- Electrons move along electron transport chain- losing energy
- Energy lost Is used so proton pumps can pump H+ ions into inter membrane space, so conc of H+ ions is higher in inter membrane space than in mitochondrial matrix
- Hydrogen ions move down electrochemical gradient through ATP synthase (chemosomis) back into mitochondrial matrix which increases ATP production,
- In matrix the electrons join onto their final acceptor oxygen to make water
When does anaerobic respiration occur
Happens when there is an absence of oxygen
Less ATP is produced through anaerobic respiration so it’s is a temporary measure
What are obligate anaerobes
Organism that cannot survive in presence of oxygen
What are facultative anaerobes
Organism that mostly use aerobic respiration but can switch to anaerobic if conditions dictate this should happen
What are obligate aerobes
Can only synthasise ATP in presence of oxygen
What is fermentation
Process by which complex organic compounds like glucose are broken down into simpler inorganic compounds without using oxygen as final electron acceptor
Describe how lactate fermentation
- reduced NAD donates hydrogen (and electrons) to pyruvate, producing lactate and NAD.
- This uses lactate dehydrogenase
- Lactate reacts with oxygen in liver to make glucose through gluconeogenesis
(More NAD being regenerated means more for glycolysis. This enables anaerobic respiration to continue and ensures that small amounts of energy can still be made in the absence of oxygen)
Describe how alcoholic fermentation happens
- Pyruvate turns into ethanal by Pyruvate decarboxylate, which realises carbon dioxide
- Which then turns into ethanol ad reduced NAD from glycolysis transfers hydrogen to ethanol to form ethanol and NAD
Why is a small amount of ATP produced during anaerobic respiration
In a mark scheme
1. Anaerobic respiration only goes through glycolysis, which produces 2ATP molecules per glucose molecule
2. Both Krebs and oxidative phosphorylation need oxygen, so if there is no oxygen there is no final electron acceptors
3. Only substrate level phosphorylation occurs
4. pyruvate / ethanol , used
5. Krebs cycle and)
electron transport chain / chemiosmosis /
oxidative phosphorylation , do not occur ;
Extra in book
to regenerate NAD for glycolysis (to continue)
3. This means electrons are still in electron transport chain and reduced NAD and FAD cannot be oxidised as there is no where for electrons to go
4. So no NAD or FAD is recycled
5. So decarboxylation and dehydrogenation cannot occur in Krebs
6. Glycolysis would come to a halt due to lack of NAD
What are examples of respiratory substrates
- Lipids: which can be broken down to
- glycerol which is converted into Pyruvate(enters link reaction)
- fatty acids go onto make 50 acetyl CoA which goes into make 500 ATP - Proteins: breaks down into amino acids
- remove amino group in liver through deamination which makes Pyruvate
Why do we avoid proteins as a respiratory substrate
Deamination uses ATP which decreases net ATP production
Also proteins comes from muscles which is broken down
What is the equation for the respiratory quittent
CO2 produced/ o2 absorbed
Why does lipids have a lower respiratory quotient compared to carbohydrates
More oxygen is needed to break lipids down
How much ATP is produced in aerobic respiration
Glycolysis: make 2 ATP and 2 Red NAD
Link: 1 red NAD x2 because there are two Pyruvate
Krebs: make 1 ATP, 3 red NAD and 1 FAD
So we made 8ATP from stage 1, 6 ATP from link reaction and 24 from Krebs
1 glucose makes- 38 ATP
But other sources say 32 because FAD makes 1.5 ATP and and NAD makes 2.5 ATP
How much ATP is produced from
1 reduced NAD
1 reduced FAD
1 Red NAD: 3 ATP
1 Red FAD: 2ATP
Compare NAD and FAD
1- NAD takes part in all stages but FAD only involved in Krebs
2- NAD accepts 1 proton but FAD accepts 2 protons
3- Reduced NAD oxidised at start of, whereas reduced FAD oxidised further along cycle
4- 1 reduced NAD makes 3 ATP whereas 1 reduced FAD makes 2 ATP
