MDCAT/MCAT preparation.
Enzyme structure and function MCQs

NOTES:
Enzymes are biological catalysts that speed up biochemical reactions in living organisms. They are mostly proteins and have a unique three-dimensional structure essential for their function.

Enzyme Structure:
Primary Structure: This is the sequence of amino acids in the polypeptide chain.
Secondary Structure: This involves local folding into alpha-helices and beta-sheets due to hydrogen bonding.
Tertiary Structure: This is the overall three-dimensional shape formed by the entire polypeptide chain.
Quaternary Structure: This is the structure formed by the assembly of multiple polypeptide subunits.

Active Site:
The active site is a specific region on the enzyme where the substrate binds. The shape and chemical environment of the active site are complementary to the substrate, allowing the enzyme to catalyze the reaction efficiently.

Coenzymes and Cofactors:
Cofactors: Non-protein chemical compounds that are bound to an enzyme and are required for its activity. They can be metal ions like zinc, iron, or magnesium.
Coenzymes: Organic molecules that bind to the enzyme and help in the catalytic process. Examples include NAD+ and FAD. Coenzymes are often derived from vitamins.

Holoenzyme and Apoenzyme:
Apoenzyme: The protein part of an enzyme, without its cofactor or coenzyme.
Holoenzyme: The complete, active enzyme with its cofactor or coenzyme.

Digestive Enzymes:
Pepsin: A digestive enzyme produced in the stomach that breaks down proteins into smaller peptides. It is secreted as an inactive zymogen called pepsinogen, which is activated by the acidic environment in the stomach.

Zymase:
Zymase: A complex of enzymes found in yeast that catalyzes the fermentation of sugars into ethanol and carbon dioxide. It is crucial in processes like brewing and baking.

Optimum pH and Temperature:
Optimum pH: Each enzyme works best at a specific pH. For instance, pepsin works best in the acidic environment of the stomach (pH 1.5-2).
Optimum Temperature: Enzymes have an optimal temperature range where they function most efficiently. Human enzymes typically have an optimum temperature around 37°C (body temperature).

MCQs:
Q) Coenzymes are closely related to:
Q) The effect of reversible competitive inhibitor can be neutralized by increasing the concentration of:
Q) Prosthetic groups are:
Q) Enzyme substrate specificity is a result of which property of enzymes?
Q) In which of the following location enzymes controlling cellular respiration are present?
Q) An activated enzyme consisting of polypeptide chain and a cofactor is called:
Q) How many binding sites does an allosteric enzyme have?
Q) Which of the following properties of amino acids is affected by a change in pH?
Q) How does changing the temperature from 30°C to 40°C in the human body affect the rate of reaction?
Q) Which term refers to a non-protein organic component firmly attached to apoenzyme via covalent linkage?
Q) What is the term for an inorganic ion that serves as a detachable cofactor?
Q) What's the term for an inhibitor that binds elsewhere on the enzyme, not at the active site?
Q) Which enzyme found in saliva is responsible for the digestion of carbohydrates?
Q) Which of the following describes the function of transferases?
Q) Which statement is true about peptidyl transferase?
Q) Which bonds in enzymes are sensitive to temperature and pH, respectively?
Q) Which enzyme is the fastest in catalyzing biochemical reactions?
Q) Which organelle contains enzymes for digestion?
Q) Which enzyme is produced in an inactive form?
Q) Where are pancreatic zymogens activated?
Q) Enzyme functions by:
Q) Which enzyme is responsible for joining the ends of two strands of nucleic acid?
Q) Which enzyme complex is involved in alcoholic fermentation?
Q) What is the optimum temperature for enzymatic activity in the human body?
Q) What determines the specificity of an enzyme?
Q) An enzyme increases the speed of a reaction by:
Q) What term is used for an inactive enzyme precursor?
Q) What term describes inhibitors that block enzymes by forming weak bonds?
Q) What are inhibitors that permanently bind to enzymes and destroy their activity?
Q) Which type of enzymes can be used to digest antibodies?

What are enzymes?
How do enzymes work?
Enzyme structure and function
Examples of enzymes
Digestive enzymes
Enzyme inhibitors
Types of enzymes
Enzymes and their functions in the body
Coenzymes and cofactors
Enzyme active site
Enzyme-substrate complex
Optimum pH for enzymes
Optimum temperature for enzymes
Difference between apoenzyme and holoenzyme
Competitive vs non-competitive inhibitors
Role of enzymes in metabolism
Enzyme catalysis
Factors affecting enzyme activity

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