Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

A is matched with 2: Photosynthesis occurs in the chloroplasts where light energy is converted into chemical energy forming glucose and oxygen. B is matched with 1: Mineral uptake happens at the plasma membrane, where ions and nutrients are absorbed into the cell. C is matched with 3: Respiration takes place in the mitochondria, where glucose is broken down to release energy in the form of ATP. D is matched with 4: Protein synthesis occurs at the ribosomes where mRNA is translated into proteins.

Explanation

The potato is a modified stem known as a tuber. It is an underground stem that stores food and is capable of producing new shoots (vegetative reproduction). The "eyes" on the surface of a potato are actually buds from which new potato plants can grow. The sweet potato is also a modified root (specifically, a storage root) and not a stem. The coconut is a fruit and contains a seed, not a modified stem. Its outer husk is a part of the fruit, not a stem modification.

Explanation

Plastic surgery is the earliest medical advancement among the options listed. It dates back to ancient India, where Sushruta, known as the “Father of Surgery,” described advanced reconstructive surgical techniques in the 6th century BCE. He performed reconstructive procedures such as rhinoplasty (nose reconstruction). These procedures were significantly ahead of their time and predates other medical milestones by centuries.

Explanation

As per the WHO reports around 1996, Tuberculosis (TB) which is caused by Mycobacterium tuberculosis was responsible for the highest number of deaths globally. It primarily affects the lungs and is prevalent in developing countries due to poverty, overcrowded living conditions, and limited access to healthcare. TB has remained a significant global health burden despite being curable and preventable. However, currently Heart diseases are the largest reason behind human mortality.

Explanation

Xerophthalmia, caused by Vitamin A deficiency, is a critical public health issue in India. It primarily affects children and can lead to dryness of the conjunctiva and cornea, eventually resulting in blindness if left untreated. Addressing this condition through improved dietary intake and supplementation programs is a top priority for reducing malnutrition and its consequences in India.

Explanation

Option (b) is correct:

A is matched with 2: Carotene, specifically beta-carotene, is a provitamin A carotenoid found in plant foods. It is converted into vitamin A (retinol) in the human body which plays a crucial role in vision, immune function, and skin health. B is matched with 1: Enzymes are biological catalysts that speed up chemical reactions in the body. Pepsin is a digestive enzyme produced in the stomach that breaks down proteins into smaller peptides. C is matched with 4: Hormones are signaling molecules produced by glands that regulate physiological processes. Progesterone is a steroid hormone involved in the menstrual cycle, pregnancy, and embryogenesis. D is matched with 3: Proteins are large biomolecules made of amino acids that perform a variety of functions in the body. Keratin is a structural protein found in hair, nails, and the outer layer of skin.

Explanation

Diabetes mellitus is characterized by higher blood sugar levels (hyperglycemia) due to either insufficient insulin production or reduced insulin sensitivity. Type 1 diabetes (previously known as insulin-dependent, juvenile or childhood-onset) is characterized by deficient insulin production and requires daily administration of insulin. Type 2 diabetes affects how your body uses sugar (glucose) for energy. It stops the body from using insulin properly, which can lead to high levels of blood sugar if not treated.

Explanation

Option 1, 2 and 4 are correct: AIDS (Acquired Immunodeficiency Syndrome), caused by the HIV virus, is transmitted through:

Sexual intercourse: HIV is primarily transmitted through unprotected sexual contact, including vaginal and anal intercourse with an infected partner. The virus is present in bodily fluids such as semen and vaginal secretions. Blood transfusion: Receiving blood transfusions contaminated with HIV can transmit the virus. HIV can be transmitted from an infected mother to her child during pregnancy, childbirth, or breastfeeding. This mode of transmission is known as vertical or mother-to-child transmission. It is transferred from an infected mother to her foetus across the placenta. These are the primary modes of transmission as confirmed by WHO. Option 3 is incorrect: HIV cannot be transmitted through mosquitoes or other blood-sucking insects because the HIV virus does not survive or replicate in these organisms.

Explanation

Malnutrition refers to a state of improper nutrition, which can arise from overnutrition (excess intake of food or nutrients), undernutrition (deficiency of essential nutrients), and imbalanced nutrition (inadequate or excessive intake of specific nutrients relative to others). Overnutrition: Consuming excessive calories or nutrients can lead to obesity and associated health issues like diabetes, cardiovascular diseases, and metabolic disorders. Undernutrition: A lack of essential nutrients causes deficiencies like protein-energy malnutrition (e.g., kwashiorkor, marasmus), anemia, and weakened immunity. Imbalanced nutrition: A diet lacking in proper proportions of macronutrients (carbohydrates, proteins, fats) and micronutrients (vitamins, minerals) can cause health problems, even if calorie intake is sufficient. All these conditions impair the body’s ability to function optimally and lead to health complications.

Explanation

Fluorosis results from prolonged excessive fluoride intake, leading to alterations in tooth enamel (dental fluorosis) or bone structure (skeletal fluorosis). It is commonly linked to water sources with high natural fluoride levels such as deep wells that access fluoride-rich geological formations. Since shallow hand pumps draw water from near the surface so they are less likely to contain such high fluoride concentrations. Options (a), (b), and (c) are incorrect:

Cholera, typhoid, and jaundice are caused by microbial or viral contamination of shallow water sources, making them common risks. These diseases are not linked to deep underground water. Cholera: A severe diarrheal disease caused by Vibrio cholerae, primarily spread through contaminated water and food. Typhoid: A bacterial infection caused by Salmonella typhi, characterized by high fever, weakness, and gastrointestinal symptoms. Jaundice: A condition marked by yellowing of the skin and eyes due to excess bilirubin, often caused by liver disease, hepatitis, or bile duct obstruction.