Free medical quiz
Dietary Energy Production Quiz
Focused SBA-style practice, followed by the answer and explanation for every question.
- Free now
- 5 questions
- Full bank
- 7 questions
- Answers
- Explained
Free question
Try one with the answer
A question from this quiz. Answer it to see the explanation students get.
Which process best describes what occurs during Stage One of dietary energy production?
- A Enzymatic digestion of macronutrients into absorbable small molecules in the gastrointestinal tract You picked ✓
- B Oxidative phosphorylation across the inner mitochondrial membrane You picked ✕
- C Electron transfer along the respiratory chain to generate a proton gradient You picked ✕
- D Conversion of glucose to pyruvate within the cytosol You picked ✕
- E Formation of acetyl-CoA from pyruvate in the mitochondrial matrix You picked ✕
Correct!
Incorrect
The answer is A: Enzymatic digestion of macronutrients into absorbable small molecules in the gastrointestinal tract
Explanation
Why A is correct
See Stage One. Option A is correct. The body gets energy from food in four stages. Stage One is basic digestion. Large molecules in the diet (polysaccharides, proteins and fats) are broken down into small building blocks that can be absorbed: sugars, amino acids, and fatty acids with glycerol. This happens outside the cells, in the lumen of the gut, using digestive enzymes such as salivary amylase (which starts the digestion of starch) and pepsin (which starts the digestion of protein in the stomach). It is a catabolic process, meaning that it breaks complex molecules down into simpler ones. Importantly, no ATP is produced at this stage, because the energy comes later when the building blocks are used inside cells. The later stages are glycolysis and the link reaction (Stage Two), the Krebs cycle (Stage Three) and oxidative phosphorylation (Stage Four).
- Stage One: basic digestion, breaking large molecules into small absorbable building blocks.
- Location: outside the cells, in the lumen of the gut.
- Type: a catabolic process.
- ATP: none is produced at this stage.
A helpful aid is to count the stages by location: gut first, then cytosol, then mitochondrial matrix, then the inner mitochondrial membrane.
Why the other options are incorrect
- B. Oxidative phosphorylation across the inner mitochondrial membrane: Oxidative phosphorylation is Stage Four and takes place in the mitochondria. It is the last stage of energy production, not the first. Your answer
- C. Electron transfer along the respiratory chain to generate a proton gradient: Electron transfer along the respiratory chain is part of oxidative phosphorylation in Stage Four. It needs reduced carriers that are only made in the later stages. Your answer
- D. Conversion of glucose to pyruvate within the cytosol: Turning glucose into pyruvate is glycolysis, which is Stage Two and occurs inside cells in the cytosol. Stage One happens outside the cells, in the gut. Your answer
- E. Formation of acetyl-CoA from pyruvate in the mitochondrial matrix: Making acetyl-CoA from pyruvate is the link reaction, which belongs to Stage Two and happens in the mitochondria after glycolysis. Stage One is much earlier, before food even enters cells. Your answer
With Premium, questions you miss become Revision Coach flashcards, scheduled for review.
Question preview
What you will practise
More questions from this set. Start the quiz to answer them and see each explanation.
-
1
What is the net ATP yield produced directly by glycolysis from one glucose molecule in human cells?
-
2
Which statement best describes a defining feature of the Krebs cycle in human cells?
Revise before you test
Review SimpleMed's doctor-written article, then return here to check recall.
Read the topic articleNeed wider coverage?
Explore every Metabolism topic set, or build a tailored mixed session.
Browse subject quizzes