(SEM II) THEORY EXAMINATION 2017-18 BIOCHEMISTRY

SECTION A – Short Answer Questions

This section contains brief conceptual questions that test the basic understanding of important topics in biochemistry. Students are required to answer all questions in short form. The questions cover fundamental concepts such as carbohydrate chemistry, enzyme activity, metabolic reactions, and biological molecules. These questions help evaluate the student's basic knowledge and clarity of biochemical principles.

1. What is Mutarotation?

Answer:
Mutarotation is the change in the optical rotation of a sugar solution due to the conversion between its alpha (α) and beta (β) forms. This occurs when sugars like glucose dissolve in water and the ring structure opens and closes repeatedly until equilibrium is reached.

2. Define Essential and Non-Essential Amino Acids.

Answer:

Essential amino acids: These amino acids cannot be synthesized by the human body and must be obtained from food. Example: lysine, leucine, valine.

Non-essential amino acids: These amino acids can be synthesized by the body and are not required from diet. Example: glycine, alanine, glutamic acid.

3. What is Phosphorolysis?

Answer:
Phosphorolysis is a biochemical reaction in which a compound is broken down by the addition of inorganic phosphate (Pi) instead of water. It plays an important role in metabolic processes such as glycogen breakdown.

SECTION B – Long Answer Questions

This section requires students to answer any two questions in detail. These questions focus on deeper understanding of biochemical processes and require explanations, mechanisms, and sometimes diagrams. The topics mainly cover carbohydrates, enzymes, and metabolic pathways.

SECTION B (Long Answer)

1. What is a Monosaccharide?

Answer:
Monosaccharides are the simplest form of carbohydrates that cannot be hydrolyzed into smaller sugar molecules. They usually contain 3–7 carbon atoms and serve as basic energy sources in the body.

Examples include:

Glucose

Fructose

Galactose

Monosaccharides are important because they participate in metabolic pathways such as glycolysis, which produces energy in the form of ATP.

2. What is Enzyme Inhibition?

Answer:
Enzyme inhibition is the process by which the activity of an enzyme is decreased or stopped by a substance called an inhibitor.

Types of enzyme inhibition:

Competitive inhibition:
The inhibitor competes with the substrate for the enzyme's active site.

Non-competitive inhibition:
The inhibitor binds to another site on the enzyme and changes its structure.

Enzyme inhibition is important in drug action and metabolic regulation.

3. What are Ketone Bodies?

Answer:
Ketone bodies are compounds produced in the liver during the breakdown of fatty acids when glucose is not available.

Main ketone bodies:

Acetoacetate

Beta-hydroxybutyrate

Acetone

They serve as an alternative energy source for tissues such as the brain during fasting or starvation.

SECTION C – Descriptive / Analytical Questions

This section includes analytical and explanatory questions where students must answer any five questions in detail. These questions test deeper conceptual knowledge, biochemical mechanisms, and clinical applications.

SECTION C (Descriptive Answer)

1. What is a Reducing Sugar?

Answer:
A reducing sugar is a carbohydrate that can donate electrons and reduce other compounds because it contains a free aldehyde or ketone group.

Examples include:

Glucose

Lactose

Maltose

Reducing sugars react with Benedict’s reagent or Fehling’s solution during chemical tests.

2. What is β-Oxidation of Fatty Acids?

Answer:
β-oxidation is the metabolic process in which fatty acids are broken down in the mitochondria to produce energy.

Steps of β-oxidation include:

Oxidation

Hydration

Second oxidation

Thiolysis

This process produces acetyl-CoA, NADH, and FADH₂, which are used to generate ATP in the electron transport chain.

3. What is Oxidative Phosphorylation?

Answer:
Oxidative phosphorylation is the process of producing ATP using energy released from electron transport in the mitochondria.

Electrons from NADH and FADH₂ move through the electron transport chain, which creates a proton gradient. This gradient drives the enzyme ATP synthase to produce ATP.

This process is the main source of energy in aerobic organisms.