The average life span of human red blood cells is about: MCQ with Answer and Explanation

The average life span of human red blood cells is about:
A. 120 days
B. 1 year
C. 30 days
D. 24 hours
Answer: Option A
Solution (By JKSSB Mock Tests)
Mature human RBCs have a lifespan of approximately 120 days, after which they are phagocytosed by macrophages in the spleen and liver. They lack nuclei and organelles, thus cannot repair themselves. New RBCs are produced in the bone marrow at a rate of about 2 million per second. Erythropoietin stimulates RBC production.

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Practice More Biology Questions

Question #1
The bone that protects the brain is the:
A. Cranium
B. Vertebra
C. Sternum
D. Pelvis

Correct Answer: Option A


Explanation:
The cranium (skull) is composed of several bones fused together, encasing and protecting the brain. Vertebrae protect the spinal cord, sternum protects the heart and lungs anteriorly, pelvis supports abdominal organs and connects to legs. The cranium also provides attachment for muscles.

This question belongs to: Science Biology
Question #2
Identify the INCORRECT statement about the human brain:
A. The hypothalamus regulates body temperature.
B. The medulla oblongata controls vomiting.
C. The cerebrum is divided into two hemispheres.
D. The cerebellum is responsible for voluntary muscle movements.

Correct Answer: Option D


Explanation:
The cerebellum coordinates movement and balance; voluntary movements are initiated in the cerebrum. So B is incorrect.

This question belongs to: Science Biology
Question #3
Consider statements about human physiology: 1. The pancreas secretes both digestive enzymes and hormones. 2. The liver secretes bile, which contains digestive enzymes. 3. The gall bladder stores and concentrates bile. Which are correct?
A. 1 and 3 only
B. 2 and 3 only
C. 1, 2 and 3
D. 1 and 2 only

Correct Answer: Option A


Explanation:
The pancreas is a mixed gland; its exocrine part secretes digestive enzymes (trypsin, lipase, amylase), and its endocrine part (Islets of Langerhans) secretes hormones (insulin, glucagon). The liver continuously secretes bile, but bile does not contain digestive enzymes; it contains bile salts that emulsify fats. The gall bladder stores and concentrates this bile before releasing it into the duodenum. Thus, statements 1 and 3 are correct.

This question belongs to: Science Biology