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TEAS 7 Science TEAS 7 Practice Exam 4 Which of the following substances protec...

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.

More Questions on TEAS 7 Science

  • Q #1: Which of the following substances is responsible for donating H+ ions to act as a buffer when blood pH rises?

    A. Carbon dioxide

    B. Carbonic acid

    C. Oxygen

    D. Carbon monoxide

    Answer Explanation

    A buffer is a solution that can resist changes in pH when small amounts of acid or base are added. In the human body, blood is an important buffer that helps maintain a stable pH of about 7.4. One of the main components of the blood buffer system is the bicarbonate buffer, which involves the equilibrium between carbon dioxide (CO2), carbonic acid (H2CO3), and bicarbonate ions (HCO3-). When blood pH rises, meaning it becomes more basic, the bicarbonate buffer can donate H+ ions to lower the pH and restore the balance. The substance that donates H+ ions in this case is carbonic acid, which dissociates into H+ and HCO3-. Therefore, 

     

  • Q #2: Which of the following vessels carries oxygenated blood?

    A. Pulmonary vein

    B. Pulmonary artery

    C. Superior vena cava

    D. Inferior vena cava

    Answer Explanation

    The pulmonary vein is the only vessel in the list that carries oxygenated blood. The pulmonary artery carries deoxygenated blood from the heart to the lungs, where it gets oxygenated. The superior and inferior vena cava are large veins that carry deoxygenated blood from the upper and lower body, respectively, to the heart.

     

  • Q #3: Which of the following are used to determine a person's DNA sequence?

    A. Enzymes

    B. Blood types

    C. Genes

    D. Hormones

    Answer Explanation

    Genes are used in techniques like DNA sequencing to determine a person's DNA sequence. DNA sequencing involves determining the order of nucleotides (A, T, C, and G) in a DNA molecule. Genes are used to replicate and amplify DNA segments, allowing researchers to analyze the sequence of nucleotides present in a person's DNA

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