RowQ
The Vault
RowQ
The Vault
CBSE Class 10 Biology · 11 questions · 27 marks
Every living organism, from a single bacterium to a blue whale, must carry out certain essential functions just to stay alive — this chapter groups those functions under nutrition, respiration, transportation, and excretion. You will see how a single leaf traps sunlight to build sugar, and how kidneys the size of a fist filter the entire blood supply many times a day. Understanding these life processes also explains why simple diffusion works for a single cell but fails once an organism grows large and complex.
Which enzyme present in human saliva begins the digestion of starch in the mouth?
Answer
Salivary amylase is correct — it breaks down starch into simpler sugars like maltose; pepsin and trypsin act on proteins while lipase acts on fats.
What is the functional and structural unit of the human kidney called?
Answer
Nephron is correct — each kidney contains about a million nephrons that filter blood and form urine; neurons, alveoli, and villi belong to other organ systems.
In which cell organelle does the final, energy-rich stage of aerobic respiration take place?
Answer
Mitochondria is correct — pyruvate produced in the cytoplasm is completely broken down here into CO2 and water, releasing most of the energy.
Which blood vessel carries oxygen-rich blood from the lungs back to the heart?
Answer
Pulmonary vein is correct — it is the only vein in the body that carries oxygenated blood; the pulmonary artery, by contrast, carries deoxygenated blood to the lungs.
Assertion (A): Multicellular organisms like humans cannot rely on simple diffusion to transport oxygen and nutrients to every cell. Reason (R): As an organism's body size increases, its surface area to volume ratio decreases, making diffusion too slow to meet the demand of internal cells.
Answer
Both A and R are true and R is the correct explanation of A — this is why complex organisms have evolved dedicated transport systems such as blood circulation.
Why is diffusion an inadequate means of transport for large, multicellular organisms but sufficient for organisms like Amoeba?
Answer
In small or single-celled organisms such as Amoeba, the surface area to volume ratio is large, so diffusion alone can supply oxygen and remove waste quickly enough for every part of the body. In large multicellular organisms, the surface area to volume ratio is much smaller and the distance between the outer surface and internal cells is greater, so diffusion is too slow — dedicated transport systems (blood, xylem/phloem) are needed instead.
Describe double circulation in humans and explain why it is necessary.
Answer
In double circulation, blood passes through the heart twice in one complete cycle: the pulmonary circulation carries deoxygenated blood from the heart to the lungs and returns oxygenated blood back to the heart, while the systemic circulation carries this oxygenated blood from the heart to the rest of the body and returns deoxygenated blood back. This is necessary because it keeps oxygenated and deoxygenated blood from mixing, allowing blood to reach body tissues at high oxygen concentration and higher pressure, which supports the high energy demands of a warm-blooded body.
Differentiate between the transport of materials in xylem and phloem.
Answer
Xylem transports water and dissolved minerals; movement is unidirectional (only upward from roots to leaves), and it is driven mainly by transpiration pull, a passive physical process requiring no energy. Phloem transports food, mainly sucrose, made during photosynthesis; movement (translocation) can occur in both upward and downward directions depending on need, and it requires ATP energy supplied by companion cells to load and unload sugars.
Describe the structure of a nephron and explain the steps involved in the formation of urine.
Answer
A nephron consists of a cup-shaped Bowman's capsule surrounding a cluster of capillaries called the glomerulus, followed by a long renal tubule with three regions: the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule, which opens into a collecting duct. Urine formation occurs in three steps. First, filtration occurs at the glomerulus, where blood pressure forces water, glucose, amino acids, salts, and nitrogenous wastes like urea out of the blood into the Bowman's capsule, forming a filtrate (blood cells and large proteins are retained in the blood). Second, selective reabsorption occurs as the filtrate passes along the tubule — useful substances such as glucose, amino acids, most salts, and a large amount of water are reabsorbed back into the surrounding capillaries. Third, tubular secretion adds any remaining excess ions and wastes from the blood directly into the tubule. The remaining fluid, now concentrated urine, passes through the collecting duct to the ureter, is stored in the urinary bladder, and is released through the urethra.
Explain the process of human nutrition from ingestion to absorption, mentioning the role of at least three digestive enzymes.
Answer
Human nutrition is holozoic and occurs in several steps. Ingestion: food is taken into the mouth, where teeth chew it and saliva containing salivary amylase begins breaking down starch into maltose. Digestion: the food (bolus) passes down the oesophagus by peristalsis into the stomach, where gastric glands secrete hydrochloric acid (which kills germs and provides an acidic medium) and pepsin, which begins protein digestion. In the small intestine, bile from the liver emulsifies fats into smaller droplets, and pancreatic juice supplies trypsin (digests proteins further) and lipase (digests emulsified fats), while intestinal enzymes complete the breakdown of all food into simple absorbable forms — glucose, amino acids, and fatty acids with glycerol. Absorption: the inner wall of the small intestine has finger-like projections called villi that greatly increase surface area and absorb these digested nutrients into the bloodstream. Assimilation and egestion: absorbed nutrients are used by body cells, while undigested waste passes into the large intestine, where water is absorbed, and the solid waste is egested through the anus.
During a football match, a player sprints hard for the ball and soon afterward feels a painful cramp in his calf muscle. Read the situation and answer: Explain, in terms of cellular respiration, why the cramp occurred and name the substance responsible.
Answer
During intense exercise, the muscle cells require energy faster than the blood can supply oxygen, so the muscles switch to anaerobic respiration. In this pathway, glucose is broken down incompletely into lactic acid, releasing a smaller amount of energy compared to aerobic respiration. The buildup of lactic acid in the muscle tissue causes fatigue and a painful cramp. The substance responsible is lactic acid, and the cramp typically eases once rest and increased oxygen supply allow it to be broken down further.
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