iGCSE Biology (0610)-16.5 Sexual hormones in humans

Question

(a) State the names of two hormones released by the ovaries.

(b) During pregnancy, antibodies are acquired by the fetus from the mother.

State the organ the antibodies cross to reach the fetus.

(c) A baby was breastfed for six months. The concentration of antibodies in the baby’s blood obtained from breast milk and the concentration of antibodies made by the baby itself were measured.

Fig. 6.1 shows the results.

(i) Complete the sentences to describe the changes in antibody concentration in the baby.

After birth the concentration of antibodies acquired from the mother decreases rapidly to 0 arbitrary units at ………………………………… months.

Antibodies start being produced by cells called ………………………………… in the baby immediately after birth.

The total concentration of antibodies in the baby from both sources is ………………………………… arbitrary units at 4 months.

The concentration of antibodies acquired from the mother and the concentration of antibodies produced by the baby are the same at ………………………………… months.

(ii) Describe the benefits of breastfeeding a baby for the first six months of life.

(iii) State two ways, other than breastfeeding, that a baby can acquire immunity.

(d) Explain the importance of the shape of an antibody.

(e) Antibodies are proteins.

State the chemical elements present in all proteins that are also found in carbohydrates and fats.

▶️ Answer/Explanation

Solution

(a) oestrogen; progesterone

Explanation: The ovaries release two main hormones – oestrogen and progesterone. Oestrogen is responsible for the development of female secondary sexual characteristics and regulation of the menstrual cycle, while progesterone prepares the uterus for pregnancy and maintains the uterine lining.

(b) placenta

Explanation: The placenta is the specialized organ that forms during pregnancy to allow the transfer of antibodies and nutrients from the mother’s bloodstream to the fetus while keeping their blood supplies separate.

(c)(i) 6; lymphocytes; 56; 3

Explanation:

The graph shows maternal antibodies decrease to zero by 6 months.
Lymphocytes are the white blood cells that produce antibodies.
At 4 months, the total antibodies (maternal + baby’s own) add up to 56 arbitrary units.
The two lines intersect at 3 months when concentrations are equal.

(c)(ii) Any two from:

Provides passive immunity by supplying maternal antibodies
Contains all necessary nutrients for baby’s growth
Helps protect against infections and diseases
Creates bonding between mother and baby
Is always at the right temperature and sterile

(c)(iii) Any two from:

Antibodies received across placenta during pregnancy
Vaccination (active immunity)
Direct antibody injections (passive immunity)
Natural infection leading to antibody production

(d) Key points:

Each pathogen has unique surface antigens
Antibodies have complementary shapes to specific antigens
This allows precise binding to mark pathogens for destruction
The specific shape enables the immune system to recognize and neutralize specific threats

(e) carbon, hydrogen, oxygen

Explanation: These three elements are common to all proteins, carbohydrates and fats. Proteins additionally contain nitrogen and sometimes sulfur, while carbohydrates and fats contain only C, H and O.

Question

Fig. 4.1 shows the concentrations of female sex hormones during the menstrual cycle.

(a) Identify, from Fig. 4.1, hormone: R and S.

(b) State the day or days of the menstrual cycle shown in Fig. 4.1 when:

ovulation is most likely to occur.

shedding of the uterine lining occurs.

(c) Describe how the concentration of progesterone would change during pregnancy. Give a reason for this change.

(d) State the sites of production of progesterone during a menstrual cycle and during pregnancy.

during a menstrual cycle

during pregnancy

(e) Describe the role of FSH in the menstrual cycle.

▶️ Answer/Explanation

Solution

(a)
– Hormone R: Oestrogen (peaks before ovulation, stimulates LH release).
– Hormone S: Luteinizing Hormone (LH) (sharp surge triggers ovulation).

(b)
– Ovulation: Days 12–16 (LH surge occurs around day 14).
– Shedding of uterine lining (menstruation): Days 1–8 (progesterone and oestrogen levels drop).

(c)
– Progesterone concentration: Increases and remains high during pregnancy.
– Reason: Maintains the thickened uterine lining and prevents menstruation/ovulation. Produced by the corpus luteum initially, then by the placenta.

(d)
– Menstrual cycle: Ovary (corpus luteum).
– Pregnancy: Placenta (after the first trimester).

(e)
– Role of FSH: Stimulates the growth and maturation of ovarian follicles and the release of oestrogen from the ovaries.

iGCSE Biology (0610)-16.5 Sexual hormones in humans – iGCSE Style Questions Paper 4

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