Question

2. Energy requiring transport mechanisms include

A. Primary active transport

B. Diffusion

C. Facilitated diffusion

D. Both A and B are correct

E. Both A and C are correct

3. The fixation of nitrogen requires _______.

A. Fe-Mo protein

B. Fe protein

C. Ferredoxin

D. Both A and B are correct

E. All of the above are correct

4. Membranes are rigid when they contain

A. Large amounts of cholesterol

B. Large amounts of unsaturated fatty acids

C. Large amounts of saturated fatty acids

D. Large amounts of water

E. A and B

5. Membrane remodeling

A. Requires phospholipases

B. Requires acyl transferases

C. Occurs only when cells are under stress

D. Both A and B are correct

E. All of the above are correct

7. Which of the following is not a function of lipids

A. Energy storage

B. Components of biological membranes

C. Insulation

D. Source of acetyl-CoA

E. All of the above are functions of lipids

Answer 1

Ans.1

The answer is (A) Primary active transport

Explanation:

There are two modes of transportation of molecules across a membrane and they are differentiated on whether they or not these modes require energy for transportation.The two modes are:

• Active Transport - Active transport requires energy in the form of ATP as they are associated with transporting high concentration molecules like ions,glucose and amino acids.
• Passive Transport - Passive transport of molecules does not require energy.

Diffusion is a type of passive transport where the particles move down their concentration gradient and hence no added energy is required.This is because the allows the passage of only small and non polar molecules across the membrane.

Facilitated diffusion is form of passive transport that occur only with the help of a carrier molecule.It permits the passage of large and polar molecules across the membrane.The particles move down their concentration gradient with dependence on the specific carrier proteins.

Thus, diffusion and facilitated diffusion both does not require energy to carry out the transportation.Hence, the answer is Primary active transport.

Ans.2:

The answer is (E) All of the above are correct

Explanation:

The process of conversion of molecular nitrogen that is present in the air into ammonia or other related nitrogenous compounds in soil is called as Nitrogen Fixation.For biological nitrogen fixation to happen a nitrogenase enzyme is required,usually found in microbes,along with a cofactor called Fe-Mo protein which catalyzes the fixation process.Iron and molybdenum are the primary components of cofactor and hence are important metals required for the fixation process.In the fixation process, the electrons flow from the electron donor ferredoxin to the reductase that is Fe protein, to nitrogenase, that is MoFe protein,to reduce nitrogen to ammonia.Conformational changes necessary for the efficient transfer of electrons is done by the hydrolysis of ATP within the reductase.

Thus, all of the molecules,Fe-Mo protein,Fe protein and Ferredoxin is required for the fixation process.Hence the answer.