Respiration Flashcards
What is respiration?
A set of metabolic reactions that take place in organisms and break down respiratory substances like glucose into smaller inorganic molecules, like water and carbon dioxide.
It is linked to the synthesis of ATP.
Why is respiration described as a catabolic process?
Because complex molecules are broken down into smaller, simpler molecules.
Why do organisms need to respire?
-It produces ATP for a variety of processes
-Releases heat energy for thermoregulation
Define aerobic respiration
Cellular respiration that takes place in the presence of oxygen and produces CO2, water and ATP.
Name the 4 main stages of aerobic respiration
glycolysis, link reaction, Krebs cycle, electron transport chain.
What is substrate level phosphorylation?
Reactions which involve the direct generation of ATP from ADP without using the respiratory chain. This involves the enzyme-catalyzed transfer of a phosphate group from an organic molecule to ATP.
Outline the stages of glycolysis.
- Glucose is phosphorylated to hexose diphosphate by 2 ATP molecules.
- Hexose biphosphate splits into two 3-carbon sugars
- Each of these molecules is oxidized to 2 pyruvate.
Net gain of 2 reduced NAD and 2 ATP per glucose molecule.
Where does glycolysis occur?
In the cytoplasm
How does pyruvate from glycolysis enter the mitochondria?
Via active transport.
What molecule is produced during anaerobic glycolysis from the reduction of pyruvate?
lactate
What is the link reaction?
The process which forms Acetyl CoA from pyruvate for use in the citric acid cycle.
Describe the link reaction
- one molecule of pyruvate is oxidatively decarboxylated and dehydrogenated to make acetate.
- this is then combined with Coenzyme A to produce acetyl CoA
Write an equation to summarize the link reaction
pyruvate + NAD + CoA - acetyl CoA + reduced NAD + CO2
where does the link reaction occur?
In the mitochondrial matrix
What is the Krebs cycle?
A series of oxidation-reduction reactions in the matrix of the mitochondria in which acetyl coenzyme A is oxidised, generating reduced NAD, reduced FAD, ATP and carbon dioxide
What is the function of the Krebs cycle?
It is a means of releasing energy from carbon bonds to provide ATP, reduced NAD and reduced FAD (with the release of CO2)
Where does the Krebs cycle occur?
In the mitochondrial matrix
What is a decarboxylation reaction?
A reaction which removes one carbon and 2 oxygen atoms from a molecule in the form of a molecule of CO2
Briefly outline the process of the Krebs cycle
A series of enzyme catalysed reactions that oxidize Acetyl CoA and produce many reduced cofactors through dehydrogenation reactions.
What is a dehydrogenation reaction?
A reaction where hydrogen is removed from a molecule.
What are the products of the Krebs cycle?
1 ATP (produced by substrate level phosphorylation)
3 reduced NAD
1 reduced FAD
2 CO2
What is the electron transport chain?
A series of electron carrier proteins that transfer electrons in a chain of oxidation-reduction reactions, releasing energy in the form of ATP.
What is ATP synthase?
Enzyme found in the inner mitochondrial membrane which catalyses the formation of ATP from ADP and inorganic phosphate, using energy from chemiosmosis H+ ions.
Define chemiosmosis
The passive diffusion of protons down a concentration gradient across a partially permeable membrane used in oxidative phosphorylation.
How does chemiosmosis produce ATP during aerobic respiration?
-Protons flow down their concentration gradient into the mitochondrial matrix via ATP synthase
-ATP synthase phosphorylates ADP to form ATP as protons flow through it.
Why is oxygen known as the terminal electron acceptor?
Oxygen accepts the electrons at the end of the electron transport chain to form water.
Describe the role of reduced NAD and reduced FAD in the electron transport chain
They are a source of electrons and protons.
How many ATP are produced per oxidized NAD in aerobic respiration?
3
How many ATP are produced per oxidized FAD in aerobic respiration?
2
What happens to lactate after a period of anaerobic exercise?
It is transported in the blood to the liver where it’s converted (under aerobic conditions) back to pyruvate and then to glucose.
What is the respiratory quotient QR?
A ratio of the CO2 production and the oxygen uptake of an organism. It can be used to determine what class of biomolecule is being used as the primary respiratory substrate.
How is the respiratory quotient (RQ) calculated?
RQ= CO2 produced / O2 consumed