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Metabolism: The Interconnected Web of Chemical Reactions in Living Organisms

Description: Metabolism: The Interconnected Web of Chemical Reactions in Living Organisms
Number of Questions: 15
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Tags: biochemistry metabolism chemical reactions living organisms
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What is the primary function of metabolism in living organisms?

  1. To convert food into energy

  2. To synthesize new cells and tissues

  3. To break down waste products

  4. To regulate body temperature


Correct Option: A
Explanation:

Metabolism is the sum of all chemical reactions that occur in a living organism, with the primary goal of converting food into energy to power cellular processes.

Which of the following is NOT a type of metabolism?

  1. Catabolism

  2. Anabolism

  3. Photosynthesis

  4. Gluconeogenesis


Correct Option: C
Explanation:

Photosynthesis is the process by which plants convert light energy into chemical energy, while catabolism, anabolism, and gluconeogenesis are all types of metabolism that occur in living organisms.

What is the role of enzymes in metabolism?

  1. To speed up chemical reactions

  2. To provide energy for chemical reactions

  3. To regulate the rate of chemical reactions

  4. To change the products of chemical reactions


Correct Option: A
Explanation:

Enzymes are biological catalysts that increase the rate of chemical reactions in living organisms by lowering the activation energy required for the reaction to occur.

Which of the following is the first step in cellular respiration?

  1. Glycolysis

  2. Krebs cycle

  3. Electron transport chain

  4. Oxidative phosphorylation


Correct Option: A
Explanation:

Glycolysis is the first step in cellular respiration, where glucose is broken down into pyruvate, releasing energy in the form of ATP.

What is the final electron acceptor in the electron transport chain?

  1. Oxygen

  2. Hydrogen

  3. Carbon dioxide

  4. Water


Correct Option: A
Explanation:

Oxygen is the final electron acceptor in the electron transport chain, where it combines with electrons and hydrogen ions to form water.

Which of the following is a key intermediate in the Krebs cycle?

  1. Acetyl CoA

  2. Pyruvate

  3. Glucose

  4. Lactate


Correct Option: A
Explanation:

Acetyl CoA is a key intermediate in the Krebs cycle, where it combines with oxaloacetate to form citrate, initiating a series of reactions that generate energy.

What is the primary function of the liver in metabolism?

  1. To detoxify harmful substances

  2. To store and release glucose

  3. To produce bile for digestion

  4. To synthesize proteins


Correct Option: B
Explanation:

The liver plays a crucial role in metabolism by storing and releasing glucose, maintaining blood sugar levels, and converting excess glucose into glycogen for storage.

Which hormone is responsible for regulating blood sugar levels?

  1. Insulin

  2. Glucagon

  3. Epinephrine

  4. Thyroxine


Correct Option: A
Explanation:

Insulin is the primary hormone responsible for regulating blood sugar levels by promoting the uptake of glucose into cells and inhibiting the production of glucose by the liver.

What is the role of gluconeogenesis in metabolism?

  1. To convert glucose into glycogen

  2. To convert glycogen into glucose

  3. To synthesize glucose from non-carbohydrate sources

  4. To break down glucose into pyruvate


Correct Option: C
Explanation:

Gluconeogenesis is the process by which glucose is synthesized from non-carbohydrate sources, such as amino acids and fatty acids, to maintain blood sugar levels.

Which of the following is NOT a product of the Krebs cycle?

  1. ATP

  2. NADH

  3. FADH2

  4. Glucose


Correct Option: D
Explanation:

Glucose is not a product of the Krebs cycle, which generates ATP, NADH, and FADH2 as high-energy molecules.

What is the primary energy currency of cells?

  1. Glucose

  2. ATP

  3. ADP

  4. NADH


Correct Option: B
Explanation:

ATP (adenosine triphosphate) is the primary energy currency of cells, providing energy for various cellular processes through the hydrolysis of its phosphate bonds.

Which of the following is a key intermediate in glycolysis?

  1. Pyruvate

  2. Glucose-6-phosphate

  3. Fructose-1,6-bisphosphate

  4. Acetyl CoA


Correct Option: C
Explanation:

Fructose-1,6-bisphosphate is a key intermediate in glycolysis, where it is split into two three-carbon molecules, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.

What is the role of the electron transport chain in metabolism?

  1. To generate ATP through oxidative phosphorylation

  2. To produce NADH and FADH2

  3. To transfer electrons from NADH and FADH2 to oxygen

  4. To regulate the Krebs cycle


Correct Option: A
Explanation:

The electron transport chain is responsible for generating ATP through oxidative phosphorylation, where electrons are transferred through a series of protein complexes, releasing energy that is used to pump protons across a membrane, creating a gradient that drives ATP synthesis.

Which of the following is a key intermediate in the pentose phosphate pathway?

  1. Glucose-6-phosphate

  2. Ribose-5-phosphate

  3. Fructose-6-phosphate

  4. Pyruvate


Correct Option: B
Explanation:

Ribose-5-phosphate is a key intermediate in the pentose phosphate pathway, which generates NADPH and ribose-5-phosphate, a precursor for the synthesis of nucleotides and nucleic acids.

What is the primary function of the urea cycle in metabolism?

  1. To convert ammonia into urea

  2. To synthesize amino acids

  3. To break down proteins

  4. To regulate the Krebs cycle


Correct Option: A
Explanation:

The urea cycle is responsible for converting toxic ammonia, a byproduct of protein metabolism, into urea, which is excreted in urine, thus eliminating nitrogenous waste from the body.

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