Back to AI Flashcard MakerBiology /Biology IB HL - 8.2 Cell Respiration Part 3
Where does pyruvate remain in anaerobic conditions and what happens to it?
The pyruvate remains in the cytosol and is converted into lactic acid (animals) or ethanol and CO2 (plants and yeast)
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Key Terms
Term
Definition
Where does pyruvate remain in anaerobic conditions and what happens to it?
The pyruvate remains in the cytosol and is converted into lactic acid (animals) or ethanol and CO2 (plants and yeast)
Is the conversion of pyruvate into lactic acid or ethanol irreversible?
This conversion is reversible and is necessary to ensure that glycolysis can continue to produce small quantities of ATP
What does glycolysis involve in terms of redox?
Glycolysis involves oxidation reactions that cause hydrogen carriers (NAD+) to be reduced (becomes NADH + H+)
What happens to reduced hydrogen carriers?
Typically, the reduced hydrogen carriers are oxidised via aerobic respiration to restore available stocks of NAD+
What will glycolysis do to hydrogen carriers in anaerobic conditions?
In the absence of oxygen, glycolysis will quickly deplete available stocks of NAD+, preventing further glycolysis
What does fermentation of pyruvate involve?
Fermentation of pyruvate involves a reduction reaction that oxidises NADH (releasing NAD+ to restore available stocks)
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| Term | Definition |
|---|---|
Where does pyruvate remain in anaerobic conditions and what happens to it? | The pyruvate remains in the cytosol and is converted into lactic acid (animals) or ethanol and CO2 (plants and yeast) |
Is the conversion of pyruvate into lactic acid or ethanol irreversible? | This conversion is reversible and is necessary to ensure that glycolysis can continue to produce small quantities of ATP |
What does glycolysis involve in terms of redox? | Glycolysis involves oxidation reactions that cause hydrogen carriers (NAD+) to be reduced (becomes NADH + H+) |
What happens to reduced hydrogen carriers? | Typically, the reduced hydrogen carriers are oxidised via aerobic respiration to restore available stocks of NAD+ |
What will glycolysis do to hydrogen carriers in anaerobic conditions? | In the absence of oxygen, glycolysis will quickly deplete available stocks of NAD+, preventing further glycolysis |
What does fermentation of pyruvate involve? | Fermentation of pyruvate involves a reduction reaction that oxidises NADH (releasing NAD+ to restore available stocks) |
What does the fermentation of pyruvate allow for? | Hence, anaerobic respiration allows small amounts of ATP to be produced (via glycolysis) in the absence of oxygen |
What is the link reaction? | The first stage of aerobic respiration is the link reaction, which transports pyruvate into the mitochondria |
What does aerobic respiration use more oxygen to do? | Aerobic respiration uses available oxygen to further oxidise the sugar molecule for a greater yield of ATP |
Why is it called the link reaction? | The link reaction is named thus because it links the products of glycolysis with the aerobic processes of the mitochondria |
How and where is pyruvate transported into the mitochondrion? | Pyruvate is transported from the cytosol into the mitochondrial matrix by carrier proteins on the mitochondrial membrane |
What does the pyruvate lose? | The pyruvate loses a carbon atom (decarboxylation), which forms a carbon dioxide molecule |
What does the decarboxylated pyruvate form? | The 2C compound then forms an acetyl group when it loses hydrogen atoms via oxidation (NAD+ is reduced to NADH + H+) |
What does the acetyl compound join with? | The acetyl compound then combines with coenzyme A to form acetyl coenzyme A (acetyl CoA) |
How many times does the link reaction occur? | As glycolysis splits glucose into two pyruvate molecules, the link reaction occurs twice per molecule of glucose |
What does one molecule of glucose form in the link reaction? | Per glucose molecule, the link reaction produces acetyl CoA (×2), NADH + H+ (×2) and CO2 (×2) |
What is the second stage of aerobic respiration? | The second stage of aerobic respiration is the Krebs cycle, which occurs within the matrix of the mitochondria |
What is the first step of Krebs? | In the Krebs cycle, acetyl CoA transfers its acetyl group to a 4C compound (oxaloacetate) to make a 6C compound (citrate) |
What is recycled in Krebs? | Coenzyme A is released and can return to the link reaction to form another molecule of acetyl CoA |
What is the overall breakdown of Krebs? | Over a series of reactions, the 6C compound is broken down to reform the original 4C compound (hence, a cycle) |
What two atoms are released and what do they form? | Two carbon atoms are released via decarboxylation to form two molecules of carbon dioxide (CO2) |
What type of redox reactions occur in Krebs? | Multiple oxidation reactions result in the reduction of hydrogen carriers (3 × NADH + H+ ; 1 × FADH2) |
How many molecules of ATP are produced by Krebs? | One molecule of ATP is produced directly via substrate level phosphorylation |
How many times does Krebs occur? | As the link reaction produces two molecules of acetyl CoA (one per each pyruvate), the Krebs cycle occurs twice |
What are the products of Krebs per glucose molecule? | Per glucose molecule, the Krebs cycle produces: 4 × CO2 ; 2 × ATP ; 6 × NADH + H+ ; 2 × FADH2 |