Biochemistry : Other Homeostatic Conditions

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #232 : Fundamental Macromolecules And Concepts

There are at least four types of glucose transporter in the body. GLUT1 and GLUT3 are located in most tissues including the brain and the red blood cells. These glucose transporters rapidly take up glucose from the blood but have the lowest  value. GLUT2 is commonly found in the liver and the pancreas. GLUT2 has a lower affinity for glucose but has the highest  value. GLUT4 is common in skeletal tissues and in adipose tissues. This transporter is normally not active for uptake unless stimulated by insulin or during exercise.  

In patients with diabetes mellitus type II, one of the best form of treatment is exercise. Which of the following statements is/are supportive for exercise as a potential treatment for type II diabetes? 

I. Exercise activates the GLUT4 transporter

II. Exercise activates the GLUT1 receptor

III. Exercise allows the skeletal muscles to uptake glucose from circulation without the need for insulin

Possible Answers:

III only

I, II, and III

I only

I and III

II only

Correct answer:

I and III

Explanation:

Diabetes mellitus type II is when the cells do not uptake glucose from the blood in the presence of insulin. Exercise allows the activation of GLUT4, which results in glucose uptake from the blood without the need of insulin.

Example Question #236 : Fundamental Macromolecules And Concepts

The GLUT1 transporter that regulates glucose uptake in red blood cells and the central nervous system is an example of __________.

Possible Answers:

primary active transport

simple diffusion

secondary active transport

mediated transport

Correct answer:

mediated transport

Explanation:

The GLUT1 transporter is a uniport member of the major facilitator superfamily. Glucose flux varies depending on glucose concentration as the transporter approaches maximum saturation. This, along with competitive inhibition, indicates mediated transport in GLUT1.

Example Question #233 : Fundamental Macromolecules And Concepts

What conformational change is responsible for converting hemoglobin from its tense (T) state to its relaxed (R) state upon binding oxygen molecules? 

Possible Answers:

Two ionic bonds are broken after binding each oxygen molecule, allowing the iron atom of the heme group to align in a progressively more planar fashion with its surrounding protoporphyrin ring 

Two ionic bonds are created after binding each oxygen molecule, allowing the iron atom of the heme group to align in a progressively more non-planar fashion with its surrounding protoporphyrin ring 

Two ionic bonds are broken after binding each oxygen molecule, allowing the iron atom of the heme group to align in a progressively more non-planar fashion with its surrounding protoporphyrin ring 

Two ionic bonds are created after binding each oxygen molecule, allowing the iron atom of the heme group to align in a progressively more planar fashion with its surrounding protoporphyrin ring 

The oxygen molecule is converted to water and the energy is used to convert between the two configurations

Correct answer:

Two ionic bonds are broken after binding each oxygen molecule, allowing the iron atom of the heme group to align in a progressively more planar fashion with its surrounding protoporphyrin ring 

Explanation:

Hemoglobin exhibits cooperative binding, so each oxygen atom which binds allows the following one to bind with more ease (for a maximum of four). Hemoglobin unbound is initially in the tense (T) state, which contains 8 ionic bonds. These bonds cause the irons atom of the heme groups to be relatively non-planar with their surrounding protoporphyrin rings, which is less stable than them being planar. Each oxygen which binds causes 2 of these ionic bonds to break, allowing the iron atom to become more and more planar upon binding more oxygens. By the time four oxygens are bound, all 8 bonds have been broken and the hemoglobin is in its fully relaxed state, with the iron atoms stably planar with their rings.

Example Question #238 : Fundamental Macromolecules And Concepts

What is a zymogen?

Possible Answers:

An enzyme that is secreted in inactive form and requires modification in order to become activated

An enzyme that is secreted in active form and undergoes modification in order to become inactivated

An antibody used to fight infection

A hormone responsible for controlling other hormone levels

Any protein secreted by the pancreas

Correct answer:

An enzyme that is secreted in inactive form and requires modification in order to become activated

Explanation:

A zymogen is a protein which is released as an inactive precursor and then requires some kind of modification (such as cleavage, hydrolysis, etc.) to become activated. An example is pepsinogen, which is released by chief cells in the stomach in an inactive form, which is then activated to become pepsin by hydrochloric acid in the stomach. Pepsin catalyzes breakdown of consumed proteins. All of the other answers are incorrect.

Example Question #239 : Fundamental Macromolecules And Concepts

Which one of the following is a characteristic of low insulin levels? 

Possible Answers:

Increased formation of 3-hydroxybutyrate

Decreased action of hormone-sensitive lipase

Increased glycogen synthesis

Decreased glycogenolysis

Correct answer:

Increased formation of 3-hydroxybutyrate

Explanation:

3-hydroxybutyrate is a ketone body, which accumulates as a result of an increase of glucagon. Increased glycogen synthesis, decreased glycogenolysis, and action of hormone-sensitive lipase are all results of an increase in insulin levels. 

Example Question #1 : Other Homeostatic Conditions

What direction is the flow of water when a cell is in a hypertonic solution?

Possible Answers:

The net flow of water will be from the cell to the environment, and this will be active and require energy.

The net flow of water will be from the environment into the cell, and this will be passive requiring no energy.

The net flow of water will be from the cell to the environment, and this will be passive and require no energy.

The net flow of water will be neither in or out of the cell.

The net flow of water will be from the environment into the cell, this will be active requiring energy.

Correct answer:

The net flow of water will be from the cell to the environment, and this will be passive and require no energy.

Explanation:

In a hypertonic solution, the net flow of water will be from the cell into the environment, the process will cause the cell to lose water and shrink. This will be passive requiring no energy. In plant cells it is called plasmolysis, and in animal cells it is called crenation.

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