The Union Public Service Commission (UPSC) Preliminary Examination stands as a formidable gateway for aspirants aiming to join the prestigious Indian civil services. Among its diverse array of subjects, Biology holds a significant position, with Human Physiology being a cornerstone topic. Understanding the intricate mechanisms governing the human body is imperative for aspirants seeking success in this competitive arena. The UPSC Prelims’ focus on Human Physiology delves into the fundamental principles governing bodily functions, from cellular processes to organ systems, thus necessitating a comprehensive grasp of physiological concepts. Through a meticulous examination of the intricacies of human biology, aspirants are not only tested on their theoretical knowledge but also on their ability to apply these principles to real-world scenarios. As such, mastering the intricacies of Human Physiology is essential for those aspiring to navigate the challenging terrain of the UPSC Preliminary Examination.
Q1. A person with ‘AB’ blood group is sometimes called a universal recipient because of the
(a) lack of the antigen in his blood
(b) lack of antibodies in his blood
(c) lack of both antigens and antibodies in his blood
(d) presence of antibodies in his blood
Ans. (b)
A person with blood type ‘AB’ is often referred to as the universal recipient because their blood lacks antibodies. These antibodies, special proteins produced in response to foreign substances (antigens), can trigger clot formation during transfusions between incompatible donor and recipient blood types within the ABO system—types A, B, O, and AB. The absence of antibodies in type AB blood means there’s no clotting reaction during transfusions. Additionally, individuals with blood type AB have both A and B antigens on their red blood cells (RBCs), allowing them to safely receive blood from donors with any blood type—A, B, AB, or O.
Q2. Which one of the following is a membrane that protects the developing embryo from desiccation? [1995]
(a) Amnion
(b) Allantois
(c) Chorion
(d) Yolk
Ans. (a)
Q3. Which one of the following hormones contains iodine? [1995]
(a) Thyroxine
(c) Insulin
(b) Testosterone
(d) Adrenaline
Ans. (a)
Thyroxine hormone, also referred to as T or tetraiodothyronine, is rich in iodine and is produced by the thyroid glands. A lack of iodine can lead to Goitre disease, characterized by the enlargement of the thyroid gland. Unlike thyroxine, the other three hormones do not contain iodine. Testosterone, for example, is a male sex hormone responsible for stimulating the growth and development of male reproductive organs.
Q4. Living organisms require at least 27 elements of which 15 are metals. Among these, those required in major quantities include (1996)
(a) potassium, manganese, molybdenum and calcium
(b) potassium, molybdenum, copper and calcium
(c) potassium, sodium, magnesium and calcium
(d) sodium, magnesium, copper and manganese
Ans. (c)
Among the elements listed above, potassium, sodium, magnesium, and calcium are needed in significant amounts. Plants and animals contain these elements in varying proportions. They are categorized into two groups: macroelements and microelements. Macronutrients, such as carbon, hydrogen, oxygen, nitrogen, calcium, phosphorus, potassium, sodium, magnesium, and sulfur, are required in larger quantities. Conversely, micronutrients, including iron, manganese, zinc, copper, iodine, cobalt, molybdenum, selenium, chromium, and silicon, are needed in smaller amounts by living organisms.
Q5. Besides proteins and carbohydrates, other element of nutritional value found in milk include (1996)
(a) calcium, potassium and iron
(b) calcium and potassium
(c) potassium and iron
(d) calcium and iron
Ans. (a)
Nutrients like calcium, potassium, and iron contribute to the nutritional value beyond proteins and carbohydrates. Milk is rich in essential minerals and nutrients, making it a ‘complete food’ despite lacking vitamin C.
Q6. The pituitary gland by virtue of its tropic hormones controls the secretary activity of other endocrine glands. Which one of the following endocrine glands can function independent of the pituitary gland (1997)
(a) Thyroid
(b) Gonads
(c) Adrenals
(d) Parathyroid
Ans. (d)
The parathyroid gland operates autonomously from the pituitary gland. Situated in the neck, these small glands generate parathyroid hormone (PTH), which crucially manages calcium and phosphorus levels in the body. Its independence from the pituitary gland stems from the counteracting effect of calcitonin hormone released by the thyroid gland, which regulates PTH activity. Thus, PTH function is governed by calcitonin rather than pituitary gland secretion.
Q7. Oxygen transportation in a human body takes place through (1997)
1. Blood
2. Lungs
3. Tissue
The correct sequence of transportation is
(a) 1,2,3
(b) 3, 1,2
(c) 2,1,3
(d) 1,3,2
Ans. (c)
Oxygen is transported within the human body through a sequential process: from the lungs to the bloodstream and then to the body’s tissues. In respiration, oxygen initially enters the body through the lungs. Subsequently, it is carried by the bloodstream to various tissues.
Q8. What is the average fat content of buffalo’s milk? (1997)
(a) 7.2%
(b) 4.5%
(c) 9.0%
(d) 10:0
Ans. (a)
Experiment: The average fat content of buffalo milk is 72%, surpassing the fat contents of other organisms, as indicated below:
- Cow’s milk: 4.2%
- Goat’s milk: 3.5%
- Human milk: 3.8%
Q9. Recommended daily intake of proteins for a moderately active women is (1997)
(a) 30 g
(b) 37 g
(c) 40 g
(d) 46
Ans (d)
The CDC suggests that a moderately active woman should aim for a daily protein intake of 46g. However, individual protein needs for women vary based on factors like weight, activity level, and pregnancy status. Pregnant and lactating women, in particular, require increased protein intake, with recommendations of 65g and 75g per day, respectively.
Q10. Consumption of fish is considered to be healthy when compared to flesh of other animals because contains fish (1998)
(a) polyunsaturated fatty acids
(b) saturated fatty acids
(c) essential vitamins
(d) more carbohydrates and proteins
Ans (d)
Fish is abundant in polyunsaturated fatty acids and boasts lower levels of saturated fatty acids compared to other meat sources. While beef and pork contain unsaturated fatty acids at a rate of 4-10%, chicken falls within the range of 25-30%. However, fish surpasses them all, boasting levels above 50%. Additionally, various plant-based oils such as soybean oil, corn oil, and sunflower oil are rich in polyunsaturated fats. These fats play a crucial role in reducing bad cholesterol levels, thereby potentially lowering the risk of heart disease and stroke.
Q11. The complete conversion of glucose in the presence of oxygen into carbon dioxide and water with release of energy is called (1998)
(a) aerobic respiration
(b) anaerobic respiration
(c) glycolysis
(d) hydrolysis
Ans. (c)
Aerobic respiration refers to the full conversion of glucose in the presence of oxygen into carbon dioxide and water, accompanied by the liberation of energy. In this metabolic pathway, glucose undergoes complete oxidation in the presence of oxygen.
76. With reference to the human body, consider following statements. (2002)
1. The production of somatotropin goes up when person exercises.
2. Men’s testes produce progesterone.
3. Adrenal glands secrete testosterone.
4. Stress causes the adrenals to release very little amount of cortisol than usual.
Which of these statements are correct?
(a) 1,2,3 and 4
(b) 1,2 and 3
(c) 2, 3 and 4
(d) 1 and 4
Ans. (d)
Statements (1) and (4) are accurate. Exercise serves as a physiological trigger for the secretion of growth hormone (somatotropin). Somatotropin levels rise with both aerobic and anaerobic exercises. Prolonged stress conditions can deplete adrenal resources or result in lower-than-normal cortisol release. Statements (2) and (3) contain errors that can be rectified: Testosterone, a male hormone, is secreted by Leydig cells in the testes. Progesterone, on the other hand, is a female hormone produced by the corpus luteum. These hormones play significant roles in the secondary sexual development of their respective organisms.
Q13.
Assertion (A) Drinking of whisky increases the 77 frequency of urination.
Reason (R) Alcohol intake speeds up the secretion of vasopressin in the body. (2002)
(a) Both A and R are individually true and R is the correct explanation of A
(b) Both A and R are individually true, but R is not the correct explanation of A
(c) A is true, but R is false
(d) A is false
Ans. (c)
Assertion: Drinking whisky increases the frequency of urination.
Reason: Alcohol acts as a diuretic, promoting urine production by inhibiting the release of ADH (anti-diuretic hormone or vasopressin) from the pituitary gland. This inhibition leads to reduced levels of ADH, which prevent the kidneys from reabsorbing water, thereby increasing urine production.
Q14. With reference to the latest developments in stem cell research, consider the following statements. (2002)
1. The only source of human stem cells are the embryos at blastocyst stage.
2. The stem cells can be derived without causing destruction to blastocysts.
3. The stem cells can regenerate themselves in vitro virtually forever.
4. Indian research centres also created a few cell lines, which can be developed into many types.
Which of these statements are correct?
(a) 1, 2 and 4
(b) 1, 2 and 3
(c) 1, 2 and 4
(d) 3 and 4
Ans. (d)
The statements regarding stem cell research are as follows:
- Statements (3) and (4) accurately describe stem cell characteristics. Stem cells, whether embryonic or adult, possess the unique ability to divide, generating both stem cells and specialized cells in response to local signals. Additionally, they can self-regenerate under controlled laboratory conditions.
- Contrary to statements (1) and (2), human embryonic stem cells are obtained from blastocysts, which are five-day-old human embryos. The process of deriving these cells involves the destruction of the embryos.
Furthermore, Indian research centers have achieved success in developing several cell lines capable of differentiation into various cell types, such as ependymal cells found in the brain’s ventricles.
Q15. With reference to the blood in a normal person, which one of the following statements is correct? (2002)
(a) Compared to arteries, veins are less numerous as hold less of the body’s blood at any given time
(b) Blood cells constitute about 70% of the total volume of the blood
(c) White Blood Cells (WBC) are made by lymph nodes only
(d) The blood has more platelets than WBC
Ans. (d)
Blood contains a greater quantity of platelets than white blood cells (WBCs). In human blood, there are approximately 300,000 platelets per cubic millimeter, whereas WBCs number around 5000 per cubic millimeter. Veins possess a similar level of complexity to arteries, both being types of blood vessels. Arteries transport blood from the heart to various organs, while veins transport blood from organs back to the heart. In a healthy individual, the volume of blood remains constant over time because blood circulation is continuous.
Q16. The hormone insulin is a (2004)
(a) glycolipids
(b) fatty acid
(c) peptide
(d) sterol
Ans. (c)
Insulin, a peptide hormone, is synthesized within the B-cells of the pancreatic islets of Langerhans. Its production involves a protein chain. Triggered mainly by heightened levels of glucose in the bloodstream, the body’s response to elevated blood sugar includes the secretion of insulin.
Q17.
Assertion (A) Fatty acids should be a part of the balanced human diet.
Reason (R) The cells of the human body not synthesise any fatty acids. (2004)
Codes
(a) Both A and R are individually true and R is the correct explanation of A
(b) Both A and R are individually true, but R is not the correct explanation of A
(c) A is true, but R is false
(d) A is false, but R is true
Ans. (c)
Assertion is true, but Reason is false. It can be corrected as as a balanced diet is the one which contains the correct proportions and quantity of various nutrients such as fats, carbohydrates, proteins, etc. to maintain health. The body cells of all mammals including man can synthesise the various fatty acids except linoleic acid and linolenic acid which can be obtained only from food. Fatty acids combines alcohol or glycerol to produce fats,
Q18. In which organ of the human body, are the lymp- hocyte cell formed? (2004)
(a) Liver
(b) Long bone
(c) Pancreas
(d) Spleen
Ans. (b)
Lymphocytes originate in the bone marrow and thymus gland. They are the smallest type of white blood cells, slightly larger than red blood cells, and characterized by a large nucleus. Constituting about 25% of the total white blood cell count, they come in two varieties: B-cells and T-cells. Together, these cells play crucial roles in generating the body’s immune responses.
Q19. Which one of the following is the correct sequence in the order of decreasing length of the three structural parts, given below, of small intestine in the human body? (2007)
(a) Jejunum-Duodenum – Ileum
(b) Ileum-Duodenum-Jejunum
(c) Jejunum – Ileum-Duodenum
(d) Ileum-Jejunum – Duodenum
Ans. (d)
The correct sequence of the small intestine’s structural parts in decreasing length is as follows: Jejunum – Ileum – Duodenum. The small intestine comprises three main segments: duodenum, jejunum, and ileum. The ileum, the final segment, is also the longest, where the intestinal walls begin to thin and narrow, and blood supply diminishes. Adjacent to the duodenum, the jejunum follows. The remainder of the small intestine coils within the lower abdominal cavity, constituting slightly less than half of the remaining length. The duodenum, which is relatively short, serves as the initial part of the small intestine into which the stomach empties.
Q20. In human body, which one of the following hormones regulates blood calcium and phosphate? (2007)
(a) Glucagon
(b) Growth hormone
(c) Parathyroid hormone
(d) Thyroxine
Ans. (c)
In the human body, the parathyroid hormone plays a crucial role in regulating the levels of calcium and phosphate in the blood. This hormone, also known as parathormone, is released from the parathyroid gland. Its main function is to elevate the calcium levels in the blood while reducing the levels of phosphorus.
Another important hormone is glucagon, which is produced by the alpha cells of the pancreas. This peptide hormone works to increase the concentration of glucose and fat in the bloodstream.
The growth hormone, secreted by the pituitary gland, is responsible for stimulating growth, cell reproduction, and cell regeneration in humans.
Thyroid hormone, on the other hand, is produced by the thyroid gland and plays a crucial role in controlling the metabolism of glucose, fat, and proteins in the body.
Q21. How do most insects respire? (2007)
(a) Through skin
(b) Through gills
(c) By lungs
(d) By tracheal system
Ans. (d)
Many insects rely on a tracheal system for respiration, utilizing a network of small tubes known as tracheae since they lack lungs. Air enters these tubes through openings called spiracles along the insect’s abdomen, then diffuses down the tracheae. Unlike insects, other creatures like earthworms and frogs respire through their skin, while fish primarily respire through gills. Mammals, including humans, predominantly respire through lungs.
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