Question

please answer all

1. A type of adipose tissue in many organisms is called brown fat. Which of the following statements is correct for brown fat?

Hibernating bears have very little of this type of adipose tissue.

It produces a great deal of heat as a result of the presence of thermogenin.

The efficiency of oxidative phosphorylation is high in this tissue.

Its color is derived from high blood supply.

2. What statement illustrates the role of Ca2+ in regulation of the pyruvate dehydrogenase (PDH) complex?

Ca2+ activates phosphatase activity, deactivating PDH activity.

In liver, Ca2+ stimulates pyruvate dehydrogenase kinase, increasing conversion of pyruvate to acetyl CoA.

Insulin causes an increase in intercellular Ca2+, inhibiting pyruvate dehydrogenase phosphatase activity.

Ca2+ is elevated in the cell with the increase of muscle contractions, activating PDH activity.

Insulin causes a decrease in Ca2+, activating pyruvate dehydrogenase kinase activity.

3. A characteristic of the glycerolphosphate shuttle is

it shuttles NADH across the mitochondrial membrane to yield 2.5 ATP/NADH

it shuttles "NADH electron equivalents" across the mitochondrial membrane to yield 1.5 ATP/NADH

it only operates efficiently when the [NADH] in the cytoplasm is higher than in the matrix

malate is a key component in the shuttle process

4. Which statement is incorrect about this cycle?

Reaction 2 is catalyzed by aconitase.

Reaction 6 is catalyzed by fumarase.

The enzyme that catalyzes reaction 4 uses the coenzyme TPP.

Reaction 6 is catalyzed by a membrane embedded enzyme.

5. What is the function of the respirasome? Select all that apply.

directly conducts ATP synthesis

facilitates a rapid transfer of the substrate

prevents the release of reaction intermediates

generates ROS

facilitates scavenging of ROS

Answer 1

1) Following three statements are correct

It produces a great deal of heat as a result of the presence of thermogenin-CORRECT

The efficiency of oxidative phosphorylation is high in this tissue- CORRECT

The efficiency of oxidative phosphorylation is high in this tissue-CORRECT

The other two statements are not correct.   Brown fat is abundant in hibernating bear, it helps bear maintain its body temperature during cold conditions via thermoregulation.   The color of the brown fat is due to presence of iron-rich mitochondria in brown fat.

2) The correct statement is

“Ca²⁺ is elevated in the cell with the increase of muscle contractions, activating PDH activity.”

Note that released Ca²⁺ will stimulate phosphotase. Phosphotase will activate PDH by removing phosphate from one of its active site. On the other hand, kinase deactivates PDH by phsophorylation of active site.

3) The correct statement is

“it shuttles "NADH electron equivalents" across the mitochondrial membrane to yield 1.5 ATP/NADH”

Note that NADH from glycolysis process bypasses complex-I as a result 1.5 ATP molecules are produced per NADH.

5) The correct statements are

facilitates a rapid transfer of the substrate

prevents the release of reaction intermediates

facilitates scavenging of ROS

Note that   respirasome contains complexes I, III and IV and plus the mobile electron carriers Q/QH2 and cytochrome c.