Which of the following substances protects the skin from ultraviolet radiation?

A. Melanin

B. Perspiration

C. Sebum

D. Keratin

Answer Explanation:

One of the functions of the skin is to protect the body from harmful effects of ultraviolet (UV) radiation. UV rays can damage the DNA of skin cells and cause mutations that may lead to skin cancer. The skin has a natural defense mechanism against UV radiation, which is the production of a pigment called melanin. Melanin is synthesized by specialized cells called melanocytes, which are located in the basal layer of the epidermis. Melanin absorbs UV rays and prevents them from reaching the deeper layers of the skin.

Therefore, the Correct Answer is A.

Q #1: In a hypertonic solution, water flows through aquaporins embedded in the plasma membrane of the cell. This type of transport is best known as which of the following?

A. Osmosis

B. Diffusion

C. Facilitated diffusion

D. Active transport

Answer Explanation

One of the ways that cells regulate their water balance is by adjusting to different solute concentrations in their environment. When a cell is placed in a solution that has a higher concentration of solutes than the cell itself, the solution is called hypertonic. In this case, water will tend to move out of the cell through special channels called aquaporins, which are embedded in the plasma membrane. This movement of water across a selectively permeable membrane is a type of passive transport called osmosis. Osmosis does not require any energy input from the cell, unlike other forms of transport such as diffusion, facilitated diffusion, or active transport.
Q #2: Which of the following is the structure through which blood exits the glomerulus?

A. Proximal tubule

B. Distal tubule

C. Afferent arteriole

D. Efferent arteriole

Answer Explanation

The glomerulus is a network of capillaries that filters blood and forms the primary urine. The blood enters the glomerulus through the afferent arteriole and leaves through the efferent arteriole. The efferent arteriole has a smaller diameter than the afferent arteriole, creating a high pressure in the glomerulus that facilitates filtration.
Q #3: Which of the following is the atomic number of an atom that has 12 protons and 12 neutrons?

A. 24

B. 1

C. 12

D. 144

Answer Explanation

The atomic number of an atom is defined as the number of protons in its nucleus. Protons are positively charged particles that make up part of the atomic mass, along with neutrons, which have no charge. The number of neutrons can vary for atoms of the same element, resulting in different isotopes. However, the number of protons is always constant for a given element. Therefore, to find the atomic number of an atom that has 12 protons and 12 neutrons, we only need to look at the number of protons.

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Which of the following substances protects the skin from ultraviolet radiation?

More Questions on TEAS 7 Science

Q #1: In a hypertonic solution, water flows through aquaporins embedded in the plasma membrane of the cell. This type of transport is best known as which of the following?

Answer Explanation

Q #2: Which of the following is the structure through which blood exits the glomerulus?

Answer Explanation

Q #3: Which of the following is the atomic number of an atom that has 12 protons and 12 neutrons?

Answer Explanation

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