All Free Biology MCQs with Answers

1451. Glycolysis process occur in?

• A. cytosol
• B. Mitochondria
• C. Matrix
• D. Endoplasmic reticulum

Explanation: Glycolysis takes place in the cytosol, the fluid portion of the cell outside the mitochondria, and splits one glucose molecule into two pyruvate molecules. The mitochondrial matrix is the site of the Krebs cycle, not glycolysis. Students may choose mitochondria because most later aerobic-respiration stages occur there.

1452. Kind of cellular respiration which occurs in presence of oxygen is _________ ?

• A. Anaerobic respiration
• B. Aerobic respiration
• C. Nitrogenous respiration
• D. Acidic respiration

Explanation: Aerobic respiration uses oxygen as the final electron acceptor and generally releases much more ATP than anaerobic respiration. Students may choose anaerobic respiration because both processes release energy from food, but anaerobic respiration occurs without oxygen.

1453. Which is not recycled in the ecosystem?

• A. Wind
• B. Carbon
• C. Oxygen
• D. Energy

Explanation: Energy flows through an ecosystem and is progressively lost as heat, so it must continually enter, mainly as sunlight, rather than being recycled. Carbon and oxygen participate in biogeochemical cycles, while wind is a moving form of energy and is not the best biological answer. Students may choose carbon because it is repeatedly transferred between organisms and the environment.

1454. In fermentation ............. ATP produce per glucose molecule :

• A. 2
• B. 4
• C. 6
• D. 36Health

Explanation: Fermentation follows glycolysis, and glycolysis produces 4 ATP but uses 2 ATP, giving a net gain of 4 - 2 = 2 ATP per glucose molecule. The likely distractor is 4 ATP, which is the gross production before subtracting the ATP investment.

1455. During anaerobic respiration the final electron acceptor in electron transport chain is:

• A. Molecular oxygen
• B. NADP+
• C. water
• D. Sulfate

Explanation: In anaerobic respiration, an inorganic substance other than oxygen accepts electrons at the end of the electron transport chain; sulfate can serve as this terminal electron acceptor in sulfate-reducing organisms. Molecular oxygen is the terminal acceptor in aerobic respiration, so it is the likely alternative students choose.

1456. Fermentation takes place in which componenet of a cell ?

• A. Cytoplasm
• B. Nucleus
• C. Mitochondria
• D. None of the above

Explanation: Fermentation is anaerobic breakdown of glucose and occurs in the cytoplasm, where glycolysis takes place; it does not require mitochondria. Students may choose mitochondria because aerobic respiration occurs there, but fermentation is used when oxygen-dependent mitochondrial respiration is not occurring.

1457. Metabolism of photosynthesis and respiration involves the knowledge of____________?

• A. Genetic engineering
• B. Biotechnology
• C. Biochemistry
• D. Chemistry

Explanation: Biochemistry applies chemistry to biological processes, including the enzyme-controlled reactions of photosynthesis and respiration and the metabolism of their products. Students may choose chemistry because chemical principles are involved, but biochemistry specifically studies those chemical reactions inside living organisms.

1458. Kranz anatomy is a characteristic feature of_________?

• A. C4 plants
• B. C3 plants
• C. C2 plants
• D. CAM plants

Explanation: Kranz anatomy is characteristic of C4 plants, whose leaves have prominent bundle-sheath cells surrounding the vascular bundles. This arrangement supports the concentration of carbon dioxide around Rubisco. Students may choose CAM plants because they also reduce photorespiration, but CAM plants do not characteristically show Kranz anatomy.

1459. Fuel used by cells in cellular respiration to get energy is ________ ?

• A. polysaccharides
• B. Polypeptides
• C. Glucose
• D. Sugar

Explanation: Glucose is the usual respiratory substrate because its oxidation in cellular respiration releases energy that is captured as ATP. Students may choose sugar, but sugar is a broad term and may include many carbohydrates, whereas glucose is the specific molecule normally meant here.

1460. Splitting of glucose relates to_________?

• A. respiration
• B. photorespiration
• C. glycolysis
• D. pyruvic acid

Explanation: Glycolysis is the metabolic pathway in which one glucose molecule is split into two three-carbon molecules of pyruvate. Respiration is the broader process, while pyruvic acid is a product rather than the name of the splitting pathway. Students often choose respiration because glucose breakdown occurs during respiration, but that answer is too general.