IB MYP Integrated Sciences e-Assessment : Reproduction Exam Style Practice Questions - New Syllabus

Question  (7 marks)

Skin is a living organ that needs care to remain healthy. The skin contains natural oils that limit evaporation of water. Many people use cosmetic products and creams to replace the natural oil lost from the skin as part of the aging process. New creams and techniques are being developed to increase oil levels in skin.

Recently, a new technique in skin care is being developed in which dermatologists use small electric currents to improve the absorption of creams. This is called galvanic facial treatment.

Question (1 mark)

Skin is naturally regenerated as old cells are replaced by new ones. State the name of the cell division process by which these cells are replaced.

▶️Answer/Explanation

Answer: Mitosis

Detailed Solution: Mitosis is the process by which cells divide to produce two identical daughter cells. This process is essential for growth, repair, and regeneration of tissues, including the skin.

Question (3 marks)

In galvanic facial treatment, a cream containing a positively charged active ingredient is applied to the skin. A positively charged electrode is put in contact with the skin. Explain how galvanic facial treatment can improve the absorption of the active ingredient into the skin.

▶️Answer/Explanation

Answer: When the skin is charged, the cells begin to absorb the material at a faster rate due to the fact that they are dividing.

Detailed Solution: The positively charged electrode repels the positively charged active ingredient in the cream, pushing it deeper into the skin. This process, known as iontophoresis, enhances the absorption of the active ingredient by using electrical currents to drive the molecules through the skin’s layers.

Question (3 marks)

Electroporation is a technique used to introduce bioactive molecules into cells. In electroporation, a voltage is applied across skin cells, which allows a small electric current to pass through cells. This current changes the characteristics of the outer layer of skin cells. If a voltage of 2 kV is applied across the face, the current passing through the skin is 250 mA. Use the formula sheet to calculate the resistance of human skin.

▶️Answer/Explanation

Answer: 250,000,000 ÷ 2000 = 125,000 Ω

Detailed Solution: Using Ohm’s Law (V = IR), where V is voltage, I is current, and R is resistance, we can calculate the resistance as follows: R = V / I. Here, V = 2 kV = 2000 V, and I = 250 mA = 0.25 A. Therefore, R = 2000 / 0.25 = 8000 Ω. However, the student’s calculation was incorrect due to a unit conversion error.