Nitrogen balance refers to:

• The balance of water and electrolytes

• The difference between protein intake and fat absorption

• The equilibrium between nitrogen intake and nitrogen loss

• The amount of DNA synthesis in the cell

Positive nitrogen balance is typically seen in:

• Starvation

• Severe infections

• Pregnancy and growth

• Chronic illness

Negative nitrogen balance indicates:

• Protein synthesis exceeds degradation

• Body is in an anabolic state

• Protein degradation exceeds synthesis

• Protein mass is maintained

Which of the following is NOT a role of protein turnover?

• Regulation of enzyme levels

• Maintenance of cellular structure

• Increase in carbohydrate storage

• Energy production during fasting

The main function of the ubiquitin-proteasome system is:

• Protein folding

• Synthesis of DNA

• Degradation of targeted proteins

• Formation of antibodies

What is the role of E1 enzyme in ubiquitination?

• Transfers ubiquitin to the target protein

• Activates ubiquitin using ATP

• Tags the protein for degradation directly

• Binds to the lysosome

The enzyme that transfers activated ubiquitin to the target protein is:

• E1

• E2

• E3

• ATP synthase

Autophagy involves:

• Degradation of extracellular proteins only

• Transport of proteins into mitochondria

• Encapsulation of cytoplasmic material into autophagosomes

• Immediate protein secretion

Which of the following best describes lysosomal degradation?

• Uses the proteasome for degradation

• Occurs only in the cytoplasm

• Involves phagocytosis and endocytosis of proteins

• Occurs only in the nucleus

Which protein tag signals degradation via the proteasome?

• Acetyl group

• Phosphate group

• Ubiquitin

• Glycosylation