12: Respiration Flashcards
What does aerobic respiration require and produce?
Requires oxygen
Produces CO2, water and a lot of ATP
When does anaerobic respiration occur and what does it produce?
Takes place in absence of oxygen
Lactate produced in animals
Ethanol and CO2 in plants and fungi
Little ATP produced
What are the stages of aerobic respiration?
Glycolysis
Link Reaction
Krebs Cycle
Oxidative phosphorylation
What are the stages of anaerobic respiration?
Glycolysis
Fermentation
Where does glycolysis occur?
Cytoplasm of the cell
What are the stages of glycolysis?
Glucose is phosphorylated twice, hydrolysing 2ATP -> 2ADP + 2Pi
Phosphorylated glucose broken down to 2x triose phosphate
Each triose phosphate reduces NAD -> NADH and produces synthesises 2ATP
2 Pyruvate molecule leave
What are the products of glycolysis from 1 glucose and their uses?
2 reduced NAD - used in oxidative phosphorylation
2 ATP (net) - used for energy
2 Pyruvate - used to input to link reaction
Where does the link reaction take place?
The matrix of the mitochondria
How are the products of glycolysis transported for the link reaction?
Products actively transported into the mitochondrial matrix
What are the stages of the link reaction?
Pyruvate oxidised to acetate, reducing NAD -> NADH and losing CO2
Acetate combines with coenzyme A to produce acetylcoenzyme A (2C)
What are the products of the link reaction from 1 glucose and what are they used for?
2 acetyl coenzyme A - used in Krebs cycle
2 reduced NAD - used in oxidative phosphorylation
2 CO2 - released as waste product
Where does the Krebs cycle occur?
Mitochondrial matrix
What are the stages of the Krebs cycle?
acetyl CoA (2C) combines with 4C to form a 6C molecule, CoA removed
6C reduces NAD, and loses CO2 producing 5C
5C reduces NAD, and loses CO2 producing 4C
4C then provides energy for ADP + Pi -> ATP
4C reduces FAD and then NAD
4C can then combine with new acetyl CoA
Happens 2 times from 1 glucose
What are the products of the Krebs cycle from 1 glucose and their uses?
6 NADH & 2 FADH - used in oxidative phosphorylation
2 ATP - used for energy
4CO2 - released as a waste product
How many ATP are produced in aerobic respiration?
~38 ATP produced
Why is the Krebs cycle important?
Breaks down macro-molecules to smaller ones (pyruvate -> CO2)
Produces H atoms carried by coenzymes and to provide energy for oxidative phosphorylation leading to producing ATP
Regenerates 4C that combines with acetyl CoA
Intermediate compounds used by cells for manufacture of other important substances (fatty acids, amino acids, chlorophyll)
What are coenzymes?
Molecules that enzymes require to function
Used to carry hydrogen atoms from one molecule to another
Where does oxidative phosphorylation occur?
Cristae of the mitochondria
Enzymes are found within the inner membrane
How are mitochondria adapted in more metabolically active cells?
Cristae are more densely packed
More mitochondria present
What is the electron transport chain (ETC)?
A series of electron carrier molecule
What are the stages of oxidative phosphorylation?
First part occurs in the matrix
Reduced NAD and FAD donate electrons from H atoms they are carrying to 1st molecule in ETC
Electrons pass along ETC molecules in redox reactions
Energy produced from this actively transports protons from coenzymes into inner-membranal space
Protons accumulate and diffuse back into matrix through ATP synthase channels, causing ATP production
At the end of the chain, the electrons combine with these protons and oxygen to form water
Why is oxygen important in oxidative phosphorylation?
Acts as the final acceptor of electrons and protons produced in Krebs and glycolysis
Without it, coenzymes stay reduced so can’t be used in Krebs and glycolysis, no oxidative phosphorylation
Why is it important that the electron transport chain happens in stages?
Little at a time means energy can be used for processes
If released at once more would be released as heat
What substances other than sugars can be oxidised to release energy?
Lipids
Proteins
How are lipids respired?
Lipids hydrolysed to glycerol and fatty acids
Glycerol phosphorylated and converted to triose phosphate and enters glycolysis pathway
Fatty acid broken down to 2C fragments and converted to acetyl CoA which enters Krebs
Why do lipids produce more energy than the same amount of carbohydrate?
Produces many 2C fragments and many H atoms
H atoms used to make ATP in oxidative phosphorylation
How are proteins respired?
Protein hydrolysed to amino acids
Amino groups removed in deamination process before entering at different points
3C converted to pyruvate
4 and 5C converted to Krebs intermediates
Which stages cannot occur in the absence of oxygen and why?
Krebs cycle - coenzymes not oxidised so cannot take protons
ETC in oxidative phosphorylation - no final acceptor so process halts and no more ATP can be synthesised
What is the source of energy in anaerobic respiration?
2 ATP produced from glycolysis
What is the process of anaerobic respiration in yeast?
Glycolysis produces pyruvate, ATP and reduced NAD
pyruvate + reduced NAD -> ethanol + CO2 + NAD
Why is a step after glycolysis required in anaerobic respiration?
Reduced NAD must be converted back into NAD to allow glycolysis to happen again
What is the process of anaerobic respiration in animals?
Pyruvate + reduced NAD -> lactate + NAD
What is the problem with anaerobic respiration in animals?
Lactate / lactic acid requires oxidation or could significantly lower pH which could effect enzymes
Causes oxygen debt to form to remove it
What are the methods for lactate removal?
Oxidation back into pyruvate
Removed by blood, taken to liver and converted to glycogen
How is energy from respiration derived?
Substrate-level phosphorylation in glycolysis and Krebs
Oxidative phosphorylation - this produces significantly more
How much energy is produced in anaerobic and aerobic respiration?
Aerobic - ~38 ATP per glucose
Anaerobic - 2 ATP per glucose
What is the respiratory quotient (RQ)?
RQ = Amount of CO2 produced / Amount of O2 used
What is the RQ value of glucose?
1
6CO2 / 6O2
What is the set up of a respirometer?
Two test tubes connected using a tube with coloured dye and a scale
Both have sodium hydroxide
One has respiring organism and tap, other has syringe and no organism
Why should the respirometer be left for some time with the tap open when placed in a water bath?
Allows organism to acclimatise to temperature
Allows pressure of air to change in the system
Why is sodium hydroxide present in the respirometer?
Absorbs CO2 produced
How does a respirometer work?
Respiring organism uses O2 and CO2 produced is absorbed
Negative pressure in test tube with organism
Coloured dye moves to the tube with the organism inside it
How do you describe CO2 and O2 use/production n respirometer questions?
O2 - consumed
CO2 - released by organism
What is the control of a respirometer experiment?
Repeat the experiment without the organism
Shows effect is due to the organism
Why is ATP so useful? (PPQ)
Energy released in small amounts
Broken down in one step
Immediate energy release so available rapidly
Adds phosphate to molecule making them more reactive
Can be reformed
How is ATP made in mitochondria? (PPQ)
Substrate level phosphorylation in Krebs
Krebs cycle produces reduced NAD and FAD
Electrons released from reduced NAD and FAD
Electrons pass through ETC
This releases energy used to actively transport protons into inter-membrane space
Protons pass through ATP synthase and allow for ADP + Pi -> ATP
Why is it important for respiration in plants as well as photosynthesis? (PPQ)
In the dark no photosynthesis and no ATP production
Some tissue cannot photosynthesise
ATP cannot be moved cell to cell
Plants use more ATP than produced in photosynthesis
ATP used for active transport and for synthesis
How does anaerobic respiration change with differing oxygen uptake?
Ethanol produced by anaerobic respiration
Ethanol increases as oxygen decreases
Then ethanol decreases as it is a toxin
What occurs to oxygen uptake and ethanol production if the ETC is inhibited? (PPQ)
Oxygen uptake stops
As oxygen is final electron acceptor as combines with electrons and protons
A large amount of ethanol produced
Why are respirometers set at the same temperature in a water bath?
Affects enzymes
Affects respiration and therefore volume of gases
Affects readings
What would occur if anaerobic organisms were put in the respirometer?
No change would occur
No oxygen uptake
All CO2 absorbed by sodium hydroxide
Why does aerobic respiration produce more ATP?
Oxygen is final electron acceptor, combines with e- and protons
Oxidative phosphorylation produces ATP
Only glycolysis occurs without oxygen
Why does anaerobic respiration produce more CO2 than aerobic?
Less ATP produced
More anaerobic respiration as more glucose must be respired for same amount of ATP
So more CO2 produced
What are the effects of preventing a proton gradient?
No proton movement so no ATP produced
Energy from electron transport not used for ATP released as heat
Oxygen used as final acceptor combines with electrons and protons so uptake remains constant
What is the function of the inner mitochondrial membrane in ATP production? (PPQ)
ETC in membrane, transfers electrons
Provides energy for active transport into intermembranal space
Protons pass back into matrix
Energy used to combine ADP + Pi -> ATP
Why is ATP an appropriate source of energy?
Energy released in small amounts
Soluble
Involves a simple reaction
Why does the human body produce a large amount of ATP?
ATP is unstable
Cannot be stored and immediate source of energy
Used for active transport
ATP only releases small amounts of energy
