7. Respiration Flashcards
How do living organisms respire?
It releases the energy stored in organic molecules such as glucose.
The energy is used to synthesise molecules of ATP.
ATP can by hydrolysed to release energy needed to drive biological processes.
What biological processes need respiration to occur?
active transport, endocytosis, exocytosis, synthesis of large molecules, DNA replication, cell division and movement
What are anabolic reactions?
Metabolic reactions where large molecules are synthesised from smaller ones.
What are catabolic reactions?
Metabolic reactions involving the hydrolysis of large molecules into smaller ones.
What is the structure of ATP?
It is a phosphorylated nucleotide.
Consists of one ribose molecule attached to three phosphate groups and an adenine.
The three phosphates are bonded by phosphoanhydride bonds
It is relatively stable when in solution in cells but readily hydrolysed by enzyme catalysis.
What is the role of ATP?
ATP is hydrolysed to ADP and P.
A small quantity of energy is released for use in the cells.
Some energy is released as heat to help keep organisms warm and allow enzyme-catalysed reactions to proceed at their optimum rate.
Why is ATP referred as the universal energy currency?
Because it occurs in all living cells and is a source of energy that can be used in small amounts.
What are the 4 stages of aerobic respiration?
Glycolysis (in the cytoplasm)
The link reaction (in the mitochondrial matrix)
The kreb’s cycle (in the mitochondrial matrix)
Oxidative phosphorylation (in the cristae of mitochondria)
What is glycolysis?
A biochemical pathway that occurs in the cytoplasm of all living organisms that respire.
It is not an aerobic process.
4 ATP molecules are produced for each glucose molecule during glycolysis.
What are the three main stages of Glycolysis?
1) Phosphorylation of glucose.
2) Splitting hexose bisphosphate molecule into two triose phosphate molecules.
3) Oxidation of triose phosphate to pyruvate.
Each step is enzyme catalysed
How is glucose phosphorylated?
Two ATP molecules are hydrolysed to form two ADP + P. The phosphate (P) molecules are added to the glucose to form hexose bisphosphate which is more reactive.
How many carbons does each molecule in glycolysis contain?
Glucose and hexose bisphosphate= 6
Triose phosphate and pyruvate= 3
How is triose phosphate oxidised into pyruvate?
2 NAD molecules take the hydrogen from each triose phosphate to form 2 pyruvate.
The 2 reduced NAD produced are needed later on in oxidative phosphorylation.
Enough energy is released in these reactions to produce 2 ATP molecules for each pyruvate formed (so 4 ATP molecules are produced overall).
What is NAD?
It is a coenzyme that assists enzymes in redox reactions.
They accept the hydrogen atoms removed during oxidation.
After it has carried out its function where it is reduced, it can be re-oxidised by giving up the hydrogen that it has accepted and be reused.
Why is NAD described as a nucleotide derivative?
Because it has the same sub-units as nucleotides.
It contains 2 five-carbon sugars, 2 phosphate groups and an adenine nitrogenous base.
However, it also contains a nicotinamide unit.
What are the products of glycolysis?
2 molecules of ATP per glucose,
4 molecules of ATP are made overall, two were used up, so the net gain is 2.
2 molecules of reduced NAD- these are actively transported into the mitochondria.
Two molecules of pyruvate- these are actively transported into the mitochondrial matrix as they are used in the link reaction.
What is the structure of mitochondria?
They have an inner and outer phospholipid membrane making up the envelope.
Between the membranes is the intermembrane space.
The inner membrane is folded into cristae.
It is embedded with proteins and protein channels.
The mitochondrial matrix contains ribosomes, looped DNA and enzymes.
The matrix is where the link reaction and Krebs cycle occurs, what structures does it contain to carry out these functions?
Molecules of the coenzyme NAD and FAD.
Oxaloacetate which accept the acetyl group from the link reaction.
Mitochondrial DNA codes for enzymes involved in the reactions.
Mitochondrial ribosomes are the sites for assembling proteins.
