Respiration Flashcards
Why does respiration occur?
To produce ATP for energy
Required in metabolic processes and for the organism to survive
Give examples of biological processes where ATP is required
Active Transport Endocytosis Exocytosis Protein synthesis DNA Replication Cell division Movement Anabolic and Catabolic reactions
Describe the structure of ATP
Pentose sugar (Ribose)
Adenine base
3 phosphates joined to sugar by phosphodiester bond
Describe the process of Glycolysis
Phosphorylation of Glucose to Hexose biphosphate
Lysis of Hexose biphosphate to Triose phosphate
Oxidation of Triose phosphate to Pyruvate
What are the 4 stages of aerobic respiration?
Glycolysis
Link Reaction
Krebs Cycle
Oxidative Phosphorylation
What are the products of Glycolysis?
2 ATP (4 were made by 2 were used at start)
2 reduced NAD (NADH)
2 Pyruvate
In What organelle does respiration occur?
Mitochondrion
Outline the key structures in the mitochondria
Double membrane (inter-membrane space)
Matrix
Cristae
ATP Synthase channels
What does the matrix contain?
Enzymes NAD and FAD molecules Oxaloacetate mitochondrial DNA mitochondrial ribosomes
Why is the inner membrane folded into cristae?
To provide a large surface area for the electron carriers and ATP synthase enzymes
Where does the link reaction occur?
Mitochondrial matrix
What enzyme catalyses the link reaction?
Pyruvate dehydrogenase
What is the main products of the link reaction?
Acetyl CoA and NADH
What is the bi-product of the Link reaction
CO2
How many molecules of each product are formed per 1 molecule of pyruvate in the link reaction?
1 Acetyl CoA
1 NADH
1 CO2
Where does the Krebs cycle occur?
Mitochondrial matrix
What is substrate-level phosphorylation?
the formation of ATP from ADP by donation of a phosphate from a substrate.
Low yield of ATP
Outline the main stages of the Krebs cycle
Acetyl (2C) group released from Acetyl CoA and combines with Oxaloacetate (4C) to form Citrate (6C)
2 stages of oxidative (aka dehydrogenation) decarboxylation occur forming a 4C compound releasing 2CO2 and 2 NADH
4C compound further dehydrogenated releasing FADH
4C compound is rearranged by isomerase enzymes and dehydrogenated (releasing NADH) to form oxaloacetate
What is the Krebs cycle designed to make lots of?
NADH (reduced NAD)
Outline the process by which energy is produced from the ETC
NADH releases a H atom, this then splits into H+ and e-
H+ accumulate in the matrix
e- picked up by a carrier protein which causes it to become reduced and pass it on to the next carrier protein in the chain (series of redox reactions)
at the end of the chain:
4H+ + 4e- + O2 = 2H2O
How is the energy released from the ETC used to create ATP?
the energy released is used to actively transport the H+ from the matrix into the inter-membrane (IM) space
H+ accumulate in IM space (as the membrane is impermeable to H+) forming an electrochemical gradient.
H+ move back through protein channels coupled to ATP Synthase enzymes
Causes a conformational change in ATP Synthase driving the production of ATP
Where does oxidative phosphorylation occur?
Cristae
Why will the process of oxidative phosphorylation not occur in anaerobic conditions?
No O2 as final acceptor of ETC Build up of e- in the matrix Electrochemical gradient doesn't form ATP Synthase isn't activated No ATP produced
Why must NADH be reoxidised for respiration to continue?
Because it is needed for the link reaction and Krebs cycle to occur
What are the 2 anaerobic pathways to reoxidise NADH?
Ethanol fermentation
Lactate fermentation
What organisms use alcohol fermentation?
Fungi such as yeast
What organisms use lactate fermentaion?
Mammals
Outline the stages of ethanol fermentation?
Pyruvate is decarboxylated to form Ethanal + CO2
Ethanal accepts H+ from NADH which reduces it to Ethanol + NAD
This means the NADH has been reoxidised allowing glycolysis to continue.
What enzyme catalyses Pyruvate to Ethanal?
Pyruvate Decarboxylase
What enzyme catalyses Ethanal to Ethanol?
Ethanol Dehydrogenase
Outline the Lactate fermentation pathway
Pyruvate accepts H+ from NADH, reducing it to lactate
This means the NADH has been reoxidised allowing glycolysis to continue.
What happens to the lactate molecules when they are produced?
Transported to the liver
When more O2 becomes available it is:
Converted back to pyruvate
Recycled into glucose and glycogen
Describe the yield of ATP from anaerobic respiration compared to aerobic respiration
Neither ethanol nor lactate fermentation produce any ATP
However, they allow glycolysis to continue which means a small amount of ATP per molecule is still made
Glycolysis happens a lot more frequently in anaerobic respiration than aerobic respiration so the yield of ATP is still high.
How are different carbohydrates converted to glucose for respiration?
Disaccharides are hydrolysed into monosaccharides
Monosaccharides such as fructose and galactose are rearranged by isomerase enzymes
Why do lipids have a higher energy value than other respiratory substrates?
Because the long fatty acid chains contain lots of hydrogens that can be snipped off at any length.
The are broken down into Acetate (2C) which combines with CoA in the link reaction
more h+ = more energy
What is the name of the process where excess amino acids are converted to pyruvate?
Deamniation
Where does Deamination occur?
Kidneys
What is the equation for respiratory quotient?
RQ = CO2 produced / O2 consumed
What are the RQ values for the different respiratory substrates?
Glucose = 1
Fatty acid = 0.7
Amino acid= 0.8 - 0.9
What would a respiratory quotient value of >1 indicate?
Aerobic respiration
because the amount of CO2 produced is greater than O2 consumed.
