12. RESPIRATION Flashcards
Explain why mitochondria have many cristae
To provide a large surface area for respiration enzymes for a faster rate of respiration
Write a full and balanced symbol equation for aerobic respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O
Describe the function of a coenzyme
To transport particles from one reaction to another
Name the four stages of aerobic respiration
Glycolysis, link reaction, Kreb’s cycle and oxidative phosphorylation
Where does glycolysis occur?
Cytoplasm
Is glycolysis anaerobic or aerobic?
Anaerobic (because it does not require oxygen)
How is glucose phosphorylated to glucose phosphate in the first stage of glycolysis?
Two phosphate ions are added from two molecules of ATP
In glycolysis, glucose phosphate splits into two 3 carbon molecules. What are they called?
Triose phosphate
Describe how pyruvate is formed from triose phosphate in the final stage of glycolysis
Triose phosphate is oxidised by the removal of hydrogen atoms, which are used to reduce NAD to NADH.
How many molecules of ATP are required in the oxidation of triose phosphate to pyruvate in glycolysis?
2 ATP per triose phosphate, so 4 ATP in total
How many carbon atoms does each pyruvate molecule contain?
3 carbons each (6 carbons in total)
Name all the reactants of glycolysis
1 x Glucose, 2 x ATP, 4 x ADP, 2 x NAD
Name all the products of glycolysis
2 x Pyruvate, 2 x ADP, 2 x NADH, 4 x ATP
Why can we say there is a net production of 2 ATP in glycolysis?
Because two ATP are required for the phosphorylation of glucose phosphate, but four ATP are produced in the oxidation of Triose Phosphate
Where does the link reaction occur?
Mitochondrial matrix
Name the two reactions that happen to pyruvate when it is converted to acetate?
Oxidation and Decarboxylation
Describe how pyruvate is oxidised to acetate in the link reaction?
Pyruvate is oxidised through the removal of hydrogen atoms which are used to reduce NAD to NADH
Describe the decarboxylation of pyruvate to acetate
A carbon atom is removed from pyruvate and is used to produce one molecule of carbon dioxide
How many carbon atoms does acetate contain?
Two
Desribe how acetate is converted to acetyl coenzyme A in the final stage of the link reaction
Acetate and coenzyme A are combined to form Acetyl Coenzyme A
Name all the reactants of the link reaction per pyruyvate molecule
1 x Pyruvate, 1 x NAD, 1 x Coenzyme A
Name all the reactants of the link reaction per glucose molecule
2 x Pyruvate, 2 x NAD, 2 x Coenzyme A
Name all the products of the link reaction per pyruvate molecule
1 x Acetylcoenzyme A, 1 x Carbon Dioxide, 1 x NADH
Name all the products of the link reaction per glucose molecule
2 x Acetylcoenzyme A, 2 x Carbon Dioxide, 2 x NADH
Describe what happens to acetylcoenzyme A in the first stage of the Krebs cycle
Acetylcoenzyme splits into acetate and coenzyme A
Describe what happens to the coenzyme A produced from the splitting of acetylcoenzyme A in the Krebs cycle
It goes back to the link reaction to bond with another molecule of acetate
Describe what happens to the acetate produced from the splitting of acetylcoenzyme A in the link reaction
It bonds with a 4 carbon molecule to produce a 6 carbon molecule
In the krebs cycle, the 6C molecule undergoes a series of what type of reactions?
A series of redox reactions
How many molecules of NAD are reduced into NADH in the series of redox reactions in the krebs cycle (per molecule of acetate)?
3 NAD reduced to 3 NADH
How many molecules of NAD are reduced into NADH in the series of redox reactions in the krebs cycle (per molecule of glucose)?
6 NAD reduced to 6 NADH
How many molecules of FAD are reduced into FADH2 in the series of redox reactions in the krebs cycle (per molecule of acetate)?
1 FAD reduced to 1 FADH2
How many molecules of FAD are reduced into FADH2 in the series of redox reactions in the krebs cycle (per molecule of glucose)?
2 FAD reduced to 2 FADH2
How many molecules of carbon dioxide are produced in the krebs cycle (per molecule of acetate)?
2 carbon dioxide molecules
How many molecules of carbon dioxide are produced in the krebs cycle (per molecule of glucose)?
4 carbon dioxide molecules
How many molecules of ATP are produced in the krebs cycle (per molecule of acetate)?
1 molecule of ATP
How many molecules of ATP are produced in the krebs cycle (per molecule of glucose)?
2 molecules of ATP
What happens to the reduced coenzymes that are made in the krebs cycle?
They are transported to the mitochondrial inner membrane to be used in oxidative phosphorylation
Where does oxidative phosphorylation occur?
Cristae (mitochondrial inner membrane)
At the beginning of oxidative phosphorylation, reduced coenyzmes are oxidised through the removal of hydrogen atoms. What do these hydrogen atoms split into?
H+ and electrons
What happens to the electrons produced from the oxidation of the coenzymes in oxidative phosphorylation?
They travel down the electron transport chain, releasing energy
What is the energy released from the electron transport chain in oxidative phosphorylation used for?
It’s used to pump the H+ from the mitochondrial matrix into the intermembrane space (over the inner membrane)
In oxidative phosphorylation, what does that pumping of H+ from the matrix into the intermembrane space create over the inner membrane?
An electrochemical gradient
Describe chemiosmosis in oxidative phosphorylation
H+ flow down an electrochemical gradient from the inner membrane space through ATP Synthase into the matrix
What does the flow of H+ through ATP Synthase during chemiosmosis catalyse?
The formation of ATP from ADP + Pi
Describe the role of oxygen in oxidative phosphorylation
It is the final electron acceptor. It bonds with electrons and H+ to form water.
Write an equation to show the formation of water at the end of the electron transport chain in oxidative phosphorylation
2H+ + 2e- + 1/2 O2 → H2O
Describe what would happen to the ETC in oxidative phosphorylation if oxygen wasn’t present
Oxygen could not act as the final electron acceptor, electrons could not pass down the ETC, the electrochemical gradient couldn’t be formed, and chemiosmosis couldn’t occur. ATP would not be formed
Apart from carbohydrates, name the two main alternative respiratory substrates
Proteins and lipids
Which chemical groups in a lipid can be used as alternative respiratory substrates?
Glycerol and fatty acids
Fatty acids can be oxidised through the removal of hydrogen atoms. Describe how these hydrogen atoms can be used as alternative substrates in respiration
The hydrogen atoms can go into oxidative phosphorylation, where they’ll split into H+ and e-
Fatty acids can be split into 2 carbon fragments. Describe how these 2 carbon fragments can be used as alternative substrates in respiration
The 2 carbon fragments are converted into acetylcoenzyme A, which enters the Krebs cycle
Describe how glycerol can be used as an alternative substrate in respiration
Glycerol can be phosphorylated to triose phosphate, which is then converted to pyruvate, which then enters the link reaction
Before being used in respiration, amino acids are deaminated. What does this mean?
Removal of the amine group
Why does deamination of amino acids produce molecules with differing numbers of carbon atoms?
Because the number of carbon atoms in the R groups will differ
Describe how the 3 carbon molecules produced from amino acid deamination can be used as an alternative substrate in respiration
They can be converted to pyruvate, which enters the link reaction and then the Krebs cycle
Describe how the 4 and 5 carbon molecules produced from amino acid deamination can be used as an alternative substrate in respiration
They are converted into intermediates and enter the krebs cycle at different points
Which is the only stage of respiration that occurs in anaerobic conditions in animals and plants
Glycolysis
Where in the cell does anaerobic respiration occur in animals?
Cytoplasm
Describe what happens to pyruvate in animal anaerobic respiration
It is reduced through the addition of a hydrogen atom from NADH
Describe the products of the reduction of pyruvate in animal anaerobic respiration
1 x Lactate, 1 x NAD
What happens to the NAD produced from anaerobic respiration in animals?
It is recycled back into glycolysis
What is the net production of ATP from anaerobic respiration in animals
2 ATP
Describe the effect of the build up of lactate in respiring tissues
It lowers the pH of the tissue, causing fatigue
Lactate can be removed from the tissue by the blood. Where is it transported to, and what happens to it?
It’s transported to the liver and turned into glycogen
How is the lactate produced in anaerobic respiration in animals converted back into pyruvate?
It is oxidised back into pyruvate when oxygen becomes available again
What is the name for the anaerobic respiration in microorganisms and plants?
Fermentation
Describe what happens to pyruvate in fermentation
It is reduced through the addition of a hydrogen atom from NADH. It is also decarboxylated, producing a molecule of carbon dioxide.
How many carbon atoms does a molecule of ethanol contain?
2 carbons
Name all the products of fermentation one molecule of pyruvate
1 x ethanol, 1 x carbon dioxide, 1 x NAD
What happens to the NAD produced from fermentation?
It is recycled back into glycolysis
Where does the Kreb’s cycle occur?
Mitochondrial matrix
