What do bioenergetics questions commonly test together?
Pathway location, inputs and outputs, and ATP or electron-carrier counts.
What are the theoretical maximum ATP yields per glucose?
36 or 38 ATP per glucose.
Why is the realistic ATP yield per glucose lower than theoretical values?
Because efficiency and NADH transport costs vary.
Where does glycolysis occur in the cell?
In the cytoplasm.
Where does the Krebs cycle occur?
In the mitochondrial matrix.
Where does the respiratory electron transport chain occur?
Across the inner mitochondrial membrane.
What is ATP composed of in cellular energy currency?
Adenine, ribose, and three phosphate groups.
Which bonds link ATP’s second and third phosphate groups?
Phosphoanhydride bonds.
Why is hydrolysis of ATP’s phosphoanhydride bonds favourable?
Because ADP and inorganic phosphate are more stable than ATP.
What happens to ATP to drive cellular work?
It is hydrolysed to ADP and inorganic phosphate.
How is ADP converted back to ATP?
By re-phosphorylation using energy from food breakdown.
How long does an ATP molecule last in an active human cell?
About one minute before being consumed and regenerated.
How much ATP does the human body recycle daily?
An amount approximately equal to body weight.
Why does an exergonic reaction release free energy?
Because its products have lower free energy than its reactants.
Why does an endergonic reaction require free-energy input?
Because its products have higher free energy than its reactants.
How is ATP hydrolysis coupled to an endergonic cellular reaction?
By transferring ATP’s terminal phosphate to a substrate.
What effect does transferring ATP’s terminal phosphate have on a substrate?
It temporarily increases the substrate’s free energy.
What is oxidation in terms of electrons?
Oxidation is the loss of electrons.
What is reduction in terms of electrons?
Reduction is the gain of electrons.
Do oxidation and reduction occur separately in redox reactions?
They always occur together in a redox reaction.
What does NAD⁺ accept to become NADH?
NAD⁺ accepts two electrons and two protons overall.
What is released into solution when NAD⁺ becomes NADH?
One proton is released into solution.
What does FAD accept to become FADH₂?
FAD accepts two hydrogen atoms.
What does FADH₂ deliver to the electron transport chain?
FADH₂ delivers electrons to the electron transport chain.
Where does glycolysis occur and does it require oxygen?
Glycolysis occurs in the cytosol without requiring oxygen.
What does glycolysis split one glucose molecule into?
Two three-carbon pyruvate molecules.
How many enzyme-catalysed steps are in glycolysis?
Ten enzyme-catalysed steps.
What is the net ATP yield from glycolysis per glucose?
Two ATP molecules net per glucose.
How many ATP are consumed and produced in glycolysis per glucose?
Two ATP are consumed and four ATP are produced.
How many NADH molecules does glycolysis produce per glucose?
Two NADH molecules.
What regulates phosphofructokinase activity?
High ATP inhibits and high AMP activates phosphofructokinase.
What happens to pyruvate when oxygen is available versus unavailable?
With oxygen, pyruvate becomes acetyl-CoA; without oxygen, fermentation regenerates NAD⁺.
What happens to pyruvate in the link reaction?
Pyruvate loses carbon dioxide and forms acetyl-CoA.
How many times does the link reaction occur per glucose molecule?
Twice per glucose molecule.
Where does the Krebs cycle occur in the cell?
In the mitochondrial matrix.
What does the electron transport chain do with electrons from NADH and FADH₂?
It passes them through protein complexes pumping protons into the intercristal space.
What is chemiosmosis?
ATP production driven by proton flow through ATP synthase down an electrochemical gradient.
What role does oxygen play in aerobic respiration?
Oxygen is the final electron acceptor forming water and allowing the chain to continue.
How does cyanide affect the electron transport chain?
It blocks the final electron transport complex.
What effect does dinitrophenol have on the inner mitochondrial membrane?
It makes the membrane leaky, dissipating the proton gradient and generating heat instead of ATP.
What does fermentation regenerate when oxidative phosphorylation is inactive?
NAD⁺
Why is fermentation necessary for glycolysis to continue?
It regenerates NAD⁺ so glycolysis can keep producing ATP.
Which fermentation reduces pyruvate to lactate without releasing CO₂?
Lactic acid fermentation
Which fermentation produces ethanol and carbon dioxide?
Alcoholic fermentation
In which organisms does lactic acid fermentation occur?
Animal cells and some bacteria
What do both lactic acid and alcoholic fermentation regenerate?
NAD⁺
How many net ATP molecules does glycolysis produce during fermentation?
Two ATP per glucose
Do lactic acid and alcoholic fermentation produce extra ATP beyond glycolysis?
No, they do not produce extra ATP.
What structures do chloroplasts use for photosynthesis?
Thylakoid membranes stacked into grana and suspended in the stroma.
What structures do mitochondria use for respiration?
Inner membrane and matrix.
Where do light-dependent reactions occur in photosynthesis?
Across the thylakoid membrane.
What molecule is split by photosystem II during light-dependent reactions?
Water.
What is the final electron acceptor in the light-dependent reactions?
NADP⁺.
Where does the Calvin cycle take place?
In the stroma.
What enzyme fixes carbon dioxide onto RuBP in the Calvin cycle?
RuBisCO.
What molecules convert three-carbon compounds into G3P in the Calvin cycle?
ATP and NADPH.
What electron sources and final acceptors does the respiratory chain use?
NADH and FADH₂ as electron sources and oxygen as final acceptor.
What electron source and final acceptor does the thylakoid chain use?
Water as electron source and NADP⁺ as final acceptor.
Where are protons pumped and where do they flow back in respiration?
Protons are pumped from the mitochondrial matrix into the intercristal space and flow back into the matrix.
Where do protons accumulate and flow back in photosynthesis?
Protons accumulate in the thylakoid space and flow back into the stroma.
How is most ATP produced from glucose in oxidative phosphorylation?
Through the respiratory electron transport chain.
Where is ATP produced directly by substrate-level phosphorylation?
In glycolysis and the Krebs cycle.
What is the approximate realistic ATP yield from one glucose molecule?
Approximately 30–32 ATP.
From which process do well over twenty ATP molecules come during glucose metabolism?
Oxidative phosphorylation rather than direct substrate-level phosphorylation.
Test your knowledge with 24 questions on Bioenergetics and ATP.
1. Regarding the Bioenergetics Exam Framework, which statements are correct?
2. A student reports both 38 ATP and approximately 30–32 ATP per glucose. Which statements correctly interpret these values?
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