3.3 Respiration Flashcards
What is respiration
Catabolic process involving a series of enzyme-catalysed reactions in cells, where energy rich respiratory substrates eg gluclose and fatty acids are broken down to release energy; some is trapped as chemical energy in ATP and some is released as heat energy.
Define aerobic respiration
Aerobic respiration is when a glucose molecule is completely broken down to carbon dioxide and water in a series of reactions.
What are the 4 stages in aerobic resiration
There are four stages:
glycolysis
link reaction
Krebs cycle
electron transport chain.
Define anaerobic respiration
Involves the incomplete breakdown of glucose in the absence of oxygen, releasing little energy and small numbers of ATP by substrate level phosphorylation
What happens during respiration
High energy C-C, C-H and C-OH bonds are broken, lower energy bonds are formed and the difference is released and used to attach Pi to ADP to made ATP.
Where does glycolysis occur
cytoplasm or cytosol
What are the end products of glycolysis
a net yield of 2 ATP produced by substrate level phosphorylation
2 molecules of reduced NAD (also written as NADH2 and NADH + H+)
2 pyruvates.
Describe the glycolysis reaction
There are 3 main stages :
1. Phosphorylation of glucose.
2. Splitting of 6c hexose phosphate into two 3C Triose phosphate molecules
3. the oxidation of each of these to 3C pyruvate with a small yield of ATP and reduced NAD.
Describe the link reaction
- Oxidation of pyruvate to acetate. (3C->2C) through loss of co2.
- carbon dioxide is produced through the action of a decarboxylase enzyme
- hydrogen is lost through the action of a dehydrogenase enzyme
- NAD is reduced by the hydrogen to NADH2
- acetate combines with co-enzyme A to produce acetyl co-enzyme A.
What are the final products of link reaction
Each molecule of glucose produces two molecules of pyruvate, so the link reaction takes place twice for each glucose molecule.
Where does link reaction take place
Mitochondrial matrix
What is the Krebs cycle
A series of enzyme controlled reactions including 2 decarboxylation reactions and 4 dehydrogenation reactions.
Where does Krebs cycle take place
mitochondrial matrix
How many Krebs cycles per glucose?
two because each molecule of glucose produces 2 pyruvate
What are the kreb cycle products
2CoA
2 4C molecules
4 CO2
2ATP
6 Reduced NAD
2 reduced FA
What are the key steps in Krebs cycle.
- Acetyl-CoA (2C) + 4C compound → 6C compound
• Coenzyme A is regenerated. - 6C → 5C → 4C (Regenerating the 4C compound)
• 2 CO₂ molecules are lost (from water).
• This is called oxidative decarboxylation. - Hydrogen atoms removed → NAD & FAD reduced
• 3 NADH and 1 FADH₂ are made per cycle. - 1 ATP is made by substrate-level phosphorylation.
What is the written equation for glycolysis
Glucose + 2 NAD(oxidised) + 2ATP +2Pi —> 2NAD(reduced) +2ATP+ Heat Energy
What is the written equation of link reaction
Pyruvate + CoA +NAD ——> acetyl CoA + CO2 + reduced NAD.
Where does the electron transport chain occur?
Inner mitochondrial membrane
What’s the role of oxygen in ETC
Final electron acceptor and formation of water.
What are the end products of anaerobic respiration in muscle cells
Lactic acid and net gain of 2 ATP molecules per gluclose molecule.
What cant occur during anaerobic respiration
Krebs cycle and link reaction because without oxygen as the final electron acceptor reduced NAD and FAD cannot be reoxidised and used again, therefore made avaliable to pick up more hydrogen
Why does glycolysis continue in anaerobic respiration
Glycolysis doesn’t require oxygen.
Reduced NAD formed in glycolysis transfers hydrogen to pyruvate to form lactic acid in animals and ethanol + co2 in plants.
Allows glycolysis to product small yield of ATP.
During aerobic respiration how many ATP is produced
38 ATP per gluclose molecule.
2 ATP - GLYCOLYSIS
2 ATP - KREBS
34 ATP - oxidative phosphorylation from 10 reduced NAD and 2 reduced FAD.
Why is there no maximum yield achieve during respiration
Losses due to leaky membranes as well as the cost of moving pyruvate and ADP into mitochondrial matrix.
Estimated 30-32 ATP per glucose lost.
How many ATP produced in anaerobic respiration
Net 2 ATP in glycolysis.
How is glycerol from lipids used in respiration
Glycerol is converted into a 3 carbon sugar (TRIOSE PHOSPHATE) an intermediate of glycolysis.
How are fatty acids used in respiration
Fatty aids undergo oxidation to form acetate fragments which are converted into acetyl co-A and fed into Krebs cycle.
What happens to proteins before they can be used in respiration
Proteins are hydrolysed into their constituent amino acids.
What process occurs to amino acids in the liver to make them useable in respiration
Amino acids undergo demination in the liver to form keto acid and ammonia.
How are keto acids used in respiration
Some keto acids are fed into glycolysis eg through pyruvate and some others are fed into Krebs cycle.
Explain how reduced FAD and reduced NAD are used to create a electrochemical gradient
Reduced NAD and FAD pass electrons into ETC.
The high energy electrons provide energy used to power proton pumps, and pump protons into inner mitochondrial space.
reduced NAD powers all 3 pumps.
