Biochemistry: The Next Level Quiz | Biochemistry

Quiz Answer Key and Fun Facts

1. Plasma is the liquid part of the human blood that is like a soup, containing several mirco- and macromolecules suspended in a fluid. What is the most abundant protein in the human blood plasma?

Answer: albumin

Albumin is the most abundant protein in the blood plasma. It serves as a carrier protein for several water-insoluble substances. It also functions to retain water in the circulation by oncotic pressure. Hemoglobin, is more abundant than albumin. However, hemoglobin is bound within the red blood cells, and therefore not normally found in the blood plasma (in vivo).

2. Proteins are denatured when placed in a low pH (acidic) environment. Proteins lose their function when they are denatured. Enzymes are examples of a protein. In the stomach, pepsin is an enzyme secreted within the hollow space of the stomach which functions for digestion. However, the enzyme pepsin is not denatured in the stomach despite the very acidic environment attributed to hydrochloric acid (HCl). How can this be?

Answer: pepsin is secreted in its precursor form (pepsinogen)

Pepsinogen is secreted into the lumen of the stomach. This is the precursor form of pepsin. Hydrochloric acid found within the stomach will hydrolyze pepsinogen. Pepsin will be formed from pepsinogen (after hydrolysis). Only then can pepsin perform its job to breakdown food particles (particulary protein in food) in the stomach.

3. A bruise, medically known as a contusion, is made when a certain external area of the body is hit by something really hard, and the capillaries in that area collapse. It first appears on the skin with a violet color. After a few days, it becomes greenish in color. A few more days after, it appears yellowish in color, until it eventually fades and disappears. What causes the bruise to appear greenish in color?

Answer: biliverdin

An injury to the capillaries also injure the red blood cells. This causes the violet color to appear on the skin. The heme of hemoglobin in red blood cells are catabolized or broken down by the macrophages. The first product is biliverdin. Biliverdin is an intermediate product of heme (from hemoglobin) catabolism or break down. Biliverdin is greenish in color.

The final product of heme catabolism is bilirubin, which is responsible for the yellowish color of a bruise several days after.

4. Which of the following is NOT a form of a feedback inhibition?

Answer: Continuous exposure to a delectable aroma of food causes secretion of saliva and movement of the gastrointestinal tract

Feedback inhibition or negative feedback is a regulatory mechanism used by the body to control certain physiologic activities. For example, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) causes the production and secretion of estrogen and progesterone, respectively.

When the estrogen and progesterone levels in the blood is already high, this gives a feedback to the anterior pituitary gland (secreting FSH and LH) to stop secreting anymore. This mechanism is known as feedback inhibition.

5. Ammonia is a nitrogenous waste product of protein metabolism, and is harmful especially in high concentrations in the human body. Urea cycle is a means to detoxify and to prevent the accumulation of ammonia in the body by converting it to urea, and eventually excreted in the urine. How many moles of nitrogen enter the urea cycle in every turn?

Answer: 2

Two moles of nitrogen enter the urea cycle. One mole of nitrogen enter the urea cycle in the form of ammonia. The other mole of nitrogen enters the urea cycle as the amino group of aspartate. Both entries are expensive, requiring a few molecules of ATP.

In each turn of the urea cycle, one molecule of urea is produced. Urea, produced in the liver via the urea cycle, is then brought to the kidneys for excretion.

6. Insulin is a peptide hormone produced in the pancreas by the beta cells. It aims to lower the glucose (sugar) levels in the blood, and is normally secreted every after meals. Their action is to activate the transporters of glucose found on the surface of cells, so that the cells can take up glucose from the blood and into the cells. What glucose transporter is regulated by the action of insulin?

Answer: glucose transporter 4 (GLUT 4)

After acting on specific target cells, insulin enables these cells to take up glucose from the blood into the cells. This action by the cells causes the lowering or decrease in the level of glucose in the blood. GLUT 4 is an insulin-regulated glucose transporter, normally found on somatic cells (liver, muscle, fat cells).

The beta cells of the pancreas (the cells that produce and secrete insulin) have GLUT 2. GLUT 2 is activated by an increase of glucose concentration in the blood. These transporters open when the cell senses that the blood has high glucose levels. This kind of transporter enables the beta cells to detect high glucose concentrations, thus secreting insulin to make the glucose concentration lower.

7. It has been known that Vitamin A improves eyesight. However, this statement is not 100% true. What makes this claim about Vitamin A partly false?

Answer: Rhodopsin (from Vitamin A) is only used to see in the dark, but not when enough light is available.

The sensory portion of the eyes (retina) contain rods and cones. The rods and cones are specialized cells responsible for the sense of vision. Rhodopsin is a pigment produced by the rods of the eyes. The rods are used for night vision, while the cones are used when ample light is available.

Rhodopsin is made from Vitamin A. It is produced only when a small amount of light is available in the environment, so that we can see in the dark. Rhodopsin is not used when enough light is available in the surroundings (example, daylight). The cones of the eyes are responsible for vision when enough light is available. They do not produce rhodopsin for us to see clearly.

8. Fiber-rich foods have been an essential part of everyday meals. Research have shown that regular consumption of fiber or fiber-rich food can lower the risk of having colon cancer. Question: What is this fiber made of?

Answer: cellulose

When a carbohydrate is not digested by the various enzymes found in the human digestive system, it is made of cellulose. Unfortunately, cellulose (commonly found in plants) cannot be digested by humans because we lack the enzyme to break it down. Fortunately, cellulose (known now as "fiber") functions in different ways that seem to be beneficial for the human body.

9. Cancer has become one of the leading causes of death all over the world. The sudden increase in the number of cases in each countries alarmed the medical community and it has now become a focus in medical research and study. Question: What is the field in medicine that deals with the biology, diagnosis, and treatment of cancer?

Answer: Oncology

Oncology came from the Greek word "onkos", meaning mass or bulk.

[Conchology is the study sea shells, cytology is the study of cells]

10. Secondary messengers are needed by cells ligands only bind to surface receptors but its action would affect some internal structures within the cells. The following ligands require secondary messengers EXCEPT:

Answer: steroid hormones

Steroid hormones do not require cell surface receptors or secondary messengers because they are lipid soluble (hydrophobic). They can easily pass through the cell membrane by means of simple diffusion. Once inside the cell, intracellular receptors bind to steroid hormones and they go to their respective target structures within the cell.

On the other hand, insulin, adrenalin (epinephrine), and glucagon require cell surface receptors because they do not easily diffuse to enter their target cells. Once they bind to their respective receptors, secondary messengers are activated and a cascade takes place, activating specific proteins and structures within the cell.

Source: Author AlvarezMD

This quiz was reviewed by FunTrivia editor crisw before going online.
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Biochemistry: The Next Level Trivia Quiz

This is quiz is about the biochemistry of the human body. It is a challenging quiz, but it is certain that you will learn a lot after this. Good luck!

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