Test 2 Review

Peter has pyruvate dehydrogenase (PDH) deficiency, a rare genetic disorder affecting his ability to produce ATP efficiently.

Which of the following is the primary function of the Pyruvate Dehydrogenase complex?

• Conversion of pyruvate to lactate

• Conversion of pyruvate to acetyl-CoA

• Conversion of lactate to pyruvate

• Conversion of acetyl-CoA to pyruvate

What is the primary consequence of PDH deficiency on ATP production?

• Increased ATP production

• Decreased ATP production

• No effect on ATP production

• Unchanged ATP production rate

The cellular organelle is primarily responsible for ATP production in aerobic conditions...

the main energy currency of the cell

Peter has Pyruvate Dehydrogenase (PDH) deficiency, a rare genetic disorder affecting his ability to produce ATP efficiently.

In PDH deficiency, what molecule accumulates due to impaired conversion by the PDH complex?

• ATP

• Acetyl-CoA

• Pyruvate

• Glucose

Which metabolic pathway is primarily affected in PDH deficiency?

• Glycosis

• Krebs cycle (Citric Acid Cycle)

• Pyruvate Decarboxylation

• ETC

Which of the following is a symptom commonly associated with PDH deficiency?

a) Increased exercise tolerance

b) High muscle strength

c) Low blood lactate levels

d) Muscle weakness

Be able to explain

f ATP hydrolysis is inhibited, which of the following types of movement across a cell membrane would likely also be inhibited?

• • Facilitated diffusion of a substance through channel proteins

• Movement of carbon dioxide molecules down their concentration gradient

• Passage of water through aquaporins

• Movement of an ion against its concentration gradient

Answer explanation

An ion moving across a membrane against its concentration gradient is an example of active transport, which often requires ATP hydrolysis. So, if ATP hydrolysis is inhibited, this type of movement would also likely be inhibited.

The sarcolemma, or muscle cell plasma membrane, helps maintain a concentration gradient of calcium ions between a muscle cell’s cytoplasm and the extracellular fluid. When a muscle cell receives a signal to contract, Ca2+  moves down this gradient, passing from the extracellular space into the cytoplasm of the cell.

Which of the following is the most likely mechanism by which   moves across the sarcolemma during muscle cell contraction?

• Ca2+

    passes through membrane channel proteins.

• Ca2+ directly diffuses through the membrane bilayer.

• Ca2+ is transported through transmembrane ATPases.

• Ca2+ flows through aquaporins.

Answer explanation

Membrane channel proteins facilitate the diffusion of charged and polar substances down their concentration gradients.   is charged and, according to the text, moves down its concentration gradient as it enters a muscle cell. So, it is likely that   moves across the sarcolemma by passing through membrane channel proteins.

Which of the following describes how phospholipid regions are positioned in the cell membrane?

• Hydrophilic phosphate regions are positioned toward aqueous environments.

• Hydrophilic phosphate regions face each other within cell membrane.

• Hydrophobic fatty acid regions are positioned toward aqueous environments.

• Hydrophobic fatty acid regions face each other outside of the cell membrane