M5C18 - Respiration Flashcards
(22 cards)
What is anaerobic respiration?
A form of respiration that occurs without oxygen, producing a small amount of ATP (2 ATP per glucose) compared to aerobic respiration (38 ATP).
What is the main difference in ATP yield between aerobic and anaerobic respiration?
Aerobic respiration yields 38 ATP per glucose, whereas anaerobic respiration yields only 2 ATP.
What are the types of organisms based on oxygen dependence?
- Obligate anaerobes: Cannot survive in oxygen.
- Facultative anaerobes: Use oxygen if present, can switch to anaerobic if absent.
- Obligate aerobes: Require oxygen but can temporarily use anaerobic respiration (e.g., muscle cells in mammals).
What is fermentation?
A type of anaerobic respiration where complex organic compounds are broken down without an external electron acceptor like oxygen, producing less ATP.
What are the two main types of fermentation?
- Lactate fermentation (in animals) 2. Alcoholic fermentation (in yeast and some plant cells)
What is the role of fermentation when oxygen is not available?
It regenerates NAD so glycolysis can continue to produce small amounts of ATP.
What happens in lactate fermentation?
Pyruvate is reduced to lactate by lactate dehydrogenase, using reduced NAD. NAD is regenerated for glycolysis to continue.
Why can’t lactate fermentation continue indefinitely?
- ATP yield is too low to sustain long-term activity. 2. Lactate accumulation causes pH to fall, denaturing enzymes and causing fatigue.
What happens to lactate after anaerobic respiration in muscles?
It’s transported to the liver where it is converted back to glucose using oxygen (oxygen debt).
What happens in alcoholic fermentation?
Pyruvate is decarboxylated to ethanal, which is then reduced to ethanol by alcohol dehydrogenase, regenerating NAD.
Can alcoholic fermentation occur indefinitely?
Yes, in yeast and some plants, because ethanol is excreted and NAD is continually regenerated.
What are respiratory substrates?
Organic molecules that are broken down to release energy for ATP synthesis, including carbohydrates, lipids, and proteins.
How are triglycerides used as respiratory substrates?
They are hydrolyzed into glycerol and fatty acids. Fatty acids enter the Krebs cycle via acetyl CoA; glycerol is converted to pyruvate first.
How is glycerol metabolized in respiration?
Glycerol is converted to pyruvate, which then undergoes oxidative decarboxylation to form acetyl CoA and enters the Krebs cycle.
Why do lipids yield more ATP than carbohydrates?
Fatty acids can produce many acetyl CoA molecules, leading to the synthesis of up to 500 ATP molecules. Lipids also have more carbon-hydrogen bonds.
How much more energy do lipids store and release compared to carbohydrates?
About twice as much energy per gram.
How do proteins enter the respiratory pathway?
They are hydrolyzed to amino acids, which are deaminated and then enter the pathway as intermediates like pyruvate or acetyl CoA.
What is the Respiratory Quotient (RQ)?
RQ = CO₂ produced / O₂ consumed. It indicates the type of substrate being respired.
What is the RQ value for glucose (a carbohydrate)?
1
What is the RQ value for proteins?
0.9
What is the RQ value for lipids?
0.7
Why do lipids have a lower RQ than carbohydrates?
They contain more carbon-hydrogen bonds, requiring more oxygen to break down and releasing less CO₂.
