All Free Biology MCQs with Answers

941. Fertilization normally occurs in the

• A. Uterus
• B. Ovary
• C. Fallopian tube
• D. Vagina

Explanation: Fertilization typically occurs in the ampulla of the fallopian tube (oviduct).

942. hCG is produced by

• A. Corpus luteum
• B. Trophoblast/Placenta
• C. Pituitary
• D. Hypothalamus

Explanation: Human chorionic gonadotropin (hCG) is produced by the trophoblast (developing placenta) to maintain the corpus luteum.

943. The morula develops into

• A. Zygote
• B. Blastocyst
• C. Gastrula
• D. Neurula

Explanation: The morula (solid ball of cells) develops into a blastocyst (with inner cell mass and blastocoel) before implantation.

944. Menstruation is caused by

• A. Rise in estrogen
• B. Fall in progesterone and estrogen
• C. Rise in hCG
• D. Rise in LH

Explanation: When pregnancy doesn't occur, the corpus luteum degenerates → progesterone and estrogen fall → endometrium breaks down.

945. Sertoli cells provide

• A. Testosterone
• B. Nourishment to developing sperm
• C. LH
• D. FSH

Explanation: Sertoli (nurse) cells provide nutrients and support to developing sperm cells in the seminiferous tubules.

946. Parturition is triggered by

• A. Rising progesterone
• B. Falling progesterone and rising oxytocin
• C. Rising hCG
• D. Falling estrogen

Explanation: Falling progesterone and rising oxytocin and prostaglandins trigger uterine contractions for childbirth.

947. The site of gas exchange in lungs is

• A. Bronchi
• B. Bronchioles
• C. Alveoli
• D. Trachea

Explanation: Alveoli are the site of gas exchange, with thin walls and large surface area for efficient O2 and CO2 diffusion.

948. Surfactant is produced by

• A. Type I alveolar cells
• B. Type II alveolar cells
• C. Goblet cells
• D. Ciliated cells

Explanation: Type II pneumocytes (alveolar cells) produce surfactant, which reduces surface tension to prevent alveolar collapse.

949. The Bohr effect describes

• A. O2 binding to hemoglobin
• B. Effect of CO2/pH on O2 affinity
• C. CO2 transport
• D. Lung compliance

Explanation: The Bohr effect states that increased CO2/decreased pH reduces hemoglobin's affinity for O2, facilitating O2 release to tissues.

950. Most CO2 is transported as

• A. Dissolved in plasma
• B. Carbaminohemoglobin
• C. Bicarbonate ions
• D. Free CO2

Explanation: About 70% of CO2 is transported as bicarbonate (HCO3-) in plasma, formed by carbonic anhydrase in RBCs.