3.3 Respiration 4 Flashcards
What is respiration?
A set of metabolic reactions that take place in organisms and break down organic compounds such as glucose into smaller inorganic molecules like water and carbon dioxide
Linked to the synthesis of ATP
Why is respiration described as a catabolic process?
Complex organic molecules are broken down into smaller simpler molecules
Why do organisms need to respire?
Produces chemical energy in ATP for a variety of processes include active transport, metabolic reactions and muscle contraction
Releases heat energy for thermoregulation
Define aerobic respiration
A form of cellular respiration that takes place in the presence of oxygen and produces carbon dioxide, water and ATP C6H12O6 + 6O2 -> 6CO2 + 6H2O
Name the four main stages of aerobic respiration and state where they occur
Glycolysis - cytoplasm
Link reaction - mitochondrial matrix
Krebs cycle - mitochondrial matrix
Electron transport chain - inner mitochondrial membrane
Outline the stages of glycolysis
- Glucose phosphorylated to hexose biphosphate by 2x ATP
- Hexose biphosphate splits into 2x triose phosphate (TP)
- 2 molecules of TP oxidised to 2x pyruvate
Net gain of 2x reduced NAD and 2x ATP per glucose
Equation to summarise glycolysis
Glucose + 2NAD + 2ADP + 2Pi -> 2 pyruvate + 2 reduced NAD + 2ATP + heat
How does pyruvate from glycolysis enter the mitochondria?
via active transport
Outline the link reaction
- Oxidative decarboxylation and dehydrogenation of pyruvate to form acetate
Net gain of CO2 and 2x reduced NAD - Acetate combines with coenzyme A (CoA) to form acetyl coenzyme A
Equation to summarise the link reaction
pyruvate + NAD + CoA -> acetyl CoA + reduced NAD + CO2
What is the Krebs cycle?
A series of oxidarion-reduction reactions in the mitochondrial matrix in which acetyk coenzyme A is oxidised generating reduced NAD, reduced FAD, ATP and CO2
Outline the stages of the Krebs cycle
What is the function of the Krebs cycle?
releasing energy from carbon bonds to provide ATP, reduced NAD and reduced FAD with release of CO2
How many NAD and FAD does complete oxidation of one glucose molecule yield?
10 reduced NAD
2 reduced FAD
What is the electron transport chain?
A series of electron carrier proteins that transfer electrons in a chain of oxidation-reduction, releasing energy
What happens in the electron transport chain?
- electrons released from reduced NAD and FAD undergo successive redox reactions
- the energy released is coupled to maintaining the proton gradient or is released as heat
- oxygen acts as the final electron acceptor
Describe the role of reduced NAD and reduced FAD in the electron transport chain
They are the source of electrons and protons
How does chemiosmosis produce ATP during aerobic respiration?
Protons flow down their conc gradient from the intermembrane space into the mitochondrial matrix via ATP Synthase
ATP Synthase phosphorylates ADP to form ATP as protons flow through it
State the role of oxygen in the electron transport chain.
Final electron acceptor
How many ATP are produced per oxidised NAD in aerobic respiration?
3 ATP
How many ATP are produced per oxidised FAD in aerobic respiration?
2 ATP
Define anaerobic respiration
A form of cellular respiration that takes place in the absence of oxygen. Less ATP is formed than in aerobic respiration.
State the product of anaerobic respiration in animals
Lactic acid
Outline anaerobic respiration in animals
Only glycolysis continues
Reduced NAD (product of glycolysis) transfers the H to pyruvate, forming lactic acid
State the products of anaerobic respiration in plants and microorganisms
Ethanol and CO2
Outlibe anaerobic respiration in plants and microorganisms
Only glycolysis continues
Pyruvate is decarboxylated to form ethanal
Ethanal is reduced to ethanol using reduced NAD producing oxidised NAD for further glycolysis
Compare the yield of ATP in aerobic and anaerobic respiration
Aerobic - 30 to 32 ATP
Anaerobic - 2 ATP
Why is the maximum yield of ATP in aerobic respiration never achieved?
ATP lost due to leaky membranes
Energy required to move pyruvate and ADP into the mitochondrial matrix
Name two types of molecules that can be used as alternative respiratory substrates
(amino acids from) proteins
(glycerol and fatty acids from) lipids
Explain how lipids are used in respiration
- Hydrolyed to glycerol and fatty acids
- Glycerol converted to a 3C sugar and enters glycolysis
- Fatty acids broken down into 2C acetate fragments whihc enter the Krebs cycle as acetyl coenzyme A
Explain how proteins are used in respiration
- Hydrolysed to amino acids
- Amino acids deaminated in the liver forming keto acids and ammonis
- Keto acids enter glycolysis and the Krebs cycle
