Give the importance of the following features in red blood cells. i) Biconcave in shape: ii) Lack of nucleus. 18. Below is the representation of hormone concentration involved in the menstrual cycle.

Here are the answers to your questions:

17. Give the importance of the following features in red blood cells.

    • i) Biconcave in shape: This shape increases the surface area to volume ratio, which facilitates efficient diffusion of oxygen into and out of the cell. It also provides flexibility, allowing red blood cells to squeeze through narrow capillaries.
    • ii) Lack of nucleus: The absence of a nucleus allows more space for hemoglobin, thereby increasing the oxygen-carrying capacity of the red blood cell. It also contributes to the cell's flexibility.

18. Below is the representation of hormone concentration involved in the menstrual cycle.

    • i) Name hormone B and D:
      • B: Estrogen (The dotted line that rises in the follicular phase, peaking before ovulation).
      • D: Progesterone (The solid line that rises significantly after ovulation).
    • ii) Name the organ that secretes hormone A: Assuming 'A' refers to a hormone that initiates the menstrual cycle, such as Gonadotropin-releasing hormone (GnRH), the organ that secretes it is the hypothalamus.

19. Give the function of the following organelles.

    • i) Ribosomes: They are the site of protein synthesis (translation), where amino acids are assembled into proteins according to genetic instructions.
    • ii) Golgi apparatus: It modifies, sorts, and packages proteins and lipids into vesicles for secretion or delivery to other organelles within the cell.

20. List two differences between monosaccharides and polysaccharides.

    • i) Monosaccharides are simple sugars (e.g., glucose, fructose) that cannot be hydrolyzed into smaller sugar units, whereas polysaccharides are complex carbohydrates (e.g., starch, cellulose) made up of many monosaccharide units linked together.
    • ii) Monosaccharides are generally sweet-tasting and soluble in water, while polysaccharides are typically not sweet and are insoluble or sparingly soluble in water.