All Free Biology MCQs with Answers

• A. Increases blood glucose level by stimulating glucagon production
• B. Decreases blood glucose levels by forming glycogen
• C. Increases blood glucose levels by promoting cellular uptake of glucose
• D. Increases blood glucose levels by hydrolysis of glycogen

Explanation: Insulin is a peptide hormone, secreted by the b cells of the islets of Langerhans in the pancreas, that promotes the uptake of glucose by body cells, particularly in the liver (hepatocytes) and muscles (adipocytes), and thereby controls its concentration in the blood.

• A. Cancer of the thyroid gland
• B. Oversecretion of pars distalis
• C. Deficiency of iodine in diet
• D. Low secretion of growth hormone

Explanation: Iodine is needed for the synthesis of T3 and T4. Iodine binds to the tyrosine residues in thyroglobulin, which is then hydrolysed into iodotyrosines that combine to form tri-iodothyronine (T3 ) or thyroxine (tetraiodothyronine or T4 ). Therefore, deficiency of iodine in the diet of a pregnant female will lead to the improper synthesis of thyroid hormones in the newly borne infant.

• A. Oxytocin - posterior pituitary - growth and maintenance of mammary glands
• B. Melatonin - ­pineal gland - regulates the normal rhythm of sleepwake cycle.
• C. Progesterone - corpus luteum-stimulation of growth and activities of female secondary sex organs
• D. Atrial natriuretic factor - ventricular wall - increases the blood pressure.

Explanation: Option C is correct. Melatonin is a hormone produced by the brain's pineal gland that primarily regulates circadian rhythms, the body's 24-hour internal clock, to promote sleep and wake cycles. Beyond sleep, it functions as an antioxidant and anti-inflammatory agent, protecting cells and DNA from damage. Melatonin also supports the immune system and can influence reproductive functions and brain health by protecting against neurodegeneration. Oxytocin is produced by the hypothalamus and generally secreted by the posterior pituitary. It stimulates the secretion of milk from mammary glands; causes contraction of the uterus at the time of childbirth. Progesterone is secreted by the corpus luteum. It stimulates the uterus for pregnancy, implantation, formation of the placenta, and development of the mammary glands. The atrial natriuretic factor is secreted by the atrial wall in response to an increased return of the venous blood. This hormone regulates the blood volume through increased excretion of ions and water.

• A. Epinephrine
• B. Cortisol
• C. Melatonin
• D. Calcitonin

Explanation: The hormones epinephrine and norepinephrine are secreted from the adrenal medulla. They are emergency hormones released in condition of stress, emergency etc. Epinephrine and norepinephrine are also released by the adrenergic nerve fibres of the sympathetic nervous system where they act as neurotransmitters.

• A. Hyposecretion of thyroid gland
• B. Hypersecretion of thyroid gland
• C. Hyposecretion of adrenal gland
• D. Hypersecretion of adrenal gland

Explanation: Graves' disease is characterized by secretion of excessive amount of thyroid hormone (T4 and T3). It is an autoimmune disease. Thyroid hormones affect many organs in the body. So Graves' disease symptoms also can affect those organs. Anyone can get Graves' disease. But it's more common in women and in people older than 30. It is characterized by exophthalmia (protrusion of eye balls because of fluid accumulation behind them), loss of weight, slight rise in the body temperature, excitability, rapid heart beat, nervousness and restlessness.

• A. Corpus cardiacum
• B. Corpus luteum
• C. Corpus allatum
• D. Pineal gland

Explanation: The corpus luteum is a temporary endocrine gland in human females. It is formed after the follicle ruptures and LH transforms this ruptured follicle into a yellow glandular mass called the corpus luteum. It secretes progesterone, which stimulates the uterine glands to produce an increased amount of watery mucus and is also essential for the maintenance of the endometrium lining. In the absence of fertilization, the corpus luteum degenerates, leading to menstruation. Hence, it is considered a temporary gland because it secretes hormones for some time and then degenerates.

• A. Thyroxin
• B. Cortisol
• C. Calcitonin
• D. None of these

Explanation: Antagonistic hormones have opposite effects on one another.The hormones antagonistic to insulin are glucagon and cortisol, adrenaline, and growth hormone.Cortisol helps control the body's use of fats, proteins, and carbohydrates; suppresses inflammation; regulates blood pressure; increases blood sugar; and can also decrease bone formation.

• A. Centrosome
• B. Nucleus
• C. Mitochondria
• D. Golgi apparatus

Explanation: Option A: Neurons cannot undergo division because they do not have centrosomes. Centrosomes are organelles that help to organize microtubules, which are essential for cell division. Without centrosomes, neurons cannot properly divide and therefore cannot repair themselves or replace damaged cells. Option B: The nucleus contains the cell's DNA, which is essential for cell division. Option C: Mitochondria are responsible for generating energy for the cell. Option D: Golgi apparatus is responsible for processing and packaging proteins. All of these organelles are essential for the normal function of neurons, but they are not necessary for cell division.

• A. Gibberellins
• B. Ethylene
• C. Cytokinins
• D. Auxins
• E. Abscisic acids

Explanation: Auxins are plant hormones that play a crucial role in regulating plant growth and development. One of their main functions is to promote cell division in the apical meristem of young plants, which is the area of the plant responsible for growth in length. Auxins also help control plant growth orientation, and promote the formation of roots and fruits.

• A. Oxytocin
• B. Parathormone
• C. Glucagon
• D. Insulin
• E. Cortisol

Explanation: Diabetes mellitus is a metabolic disorder characterized by high levels of glucose in the blood due to the inability of the body to produce or respond to the hormone insulin. Insulin is produced by the beta cells of the pancreas and is responsible for glucose uptake from the blood into the cells, where it can be used as energy or stored as glycogen. When insulin is deficient, as in the case of diabetes, glycogen synthesis gets depressed, and glucose levels increase in the blood.