CBSE Class 10 Biology Life Processes MCQs Set 19

Answer: (a) ATP

Explanation:
1. Energy released in respiration is stored in ATP (adenosine triphosphate).
2. Cells use ATP for muscle contraction, protein synthesis and conduction of nerve impulses.

Teacher's Note:
1. ATP is formed from ADP and inorganic phosphate.
2. Addition of a phosphate group is phosphorylation.

Answer: (d) cytoplasm

Explanation:
1. Glycolysis occurs in the cytoplasm and does not need oxygen.
2. One glucose molecule (6 carbon) forms two pyruvate molecules (3 carbon) with a net gain of 2 ATP.

Teacher's Note:
1. After glycolysis the path differs with and without oxygen.
2. Only the later aerobic steps occur in mitochondria.

Answer: (a) carbon dioxide produced is absorbed by KOH creating partial vacuum

Explanation:
1. Seeds respire and release CO2, which KOH absorbs.
2. The fall in gas pressure in the flask pushes the water up in the tube.

Teacher's Note:
1. This shows that germinating seeds give out carbon dioxide in respiration.
2. The apparatus must be air tight for correct results.

Answer: (d) Yeast

Explanation:
1. Yeast can obtain energy by fermentation without oxygen.
2. Human muscle cells use anaerobic respiration only during vigorous exercise, and the other animals depend on oxygen.

Teacher's Note:
1. Most bacteria also respire anaerobically.
2. Anaerobic means without air.

Answer: (b) lactic acid

Explanation:
1. With scarce oxygen, pyruvate is changed into lactic acid in muscle cells.
2. The accumulated lactic acid causes fatigue and cramps.

Teacher's Note:
1. Rest and a good oxygen supply remove the lactic acid.
2. Lactic acid has three carbon atoms.

Answer: (a) 2 ATP

Explanation:
1. Only glycolysis gives energy in absence of oxygen, which is 2 ATP.
2. Aerobic respiration gives about 38 ATP.

Teacher's Note:
1. Anaerobic respiration is much less efficient.
2. Incomplete breakdown of glucose leaves much energy in the end products.

Answer: (d) yeast and human

Explanation:
1. Yeast under anaerobic conditions gives 2 ATP, while human cells in the presence of oxygen give 38 ATP.
2. The other pairs reverse the order or put an aerobic organism in the position of the 2 ATP producer.

Teacher's Note:
1. Match the ATP number with the type of respiration.
2. Aerobic organisms get far more energy from the same amount of food.

Answer: (c) Aerobic respiration occurs in cytoplasm and mitochondria, anaerobic only in cytoplasm

Explanation:
1. The later stages of aerobic respiration need mitochondria, but anaerobic respiration is confined to the cytoplasm.
2. Aerobic respiration breaks glucose completely, and anaerobic breaks it incompletely.

Teacher's Note:
1. Compare oxygen need, site, breakdown, end products and energy.
2. This is a favourite board question.

Answer: (b) roots do not get enough oxygen and respire anaerobically

Explanation:
1. Water fills the air spaces of the soil, so roots lack oxygen.
2. Anaerobic respiration in roots produces alcohol, which is harmful, and gives little energy.

Teacher's Note:
1. Roots need oxygen for respiration like any other part.
2. Good drainage is important for plants.

Answer: (a) stomata, lenticels and root hairs

Explanation:
1. Plants have no special respiratory organs and exchange gases by diffusion through these parts.
2. Gills, lungs and trachea are respiratory organs of animals.

Teacher's Note:
1. Aquatic plants exchange gases over their whole surface.
2. Lenticels are in woody stems.

Answer: (d) nostrils, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, alveoli

Explanation:
1. This is the order of the respiratory tract from outside to the site of gas exchange.
2. The larynx lies above the trachea, and bronchi divide into bronchioles that end in alveoli.

Teacher's Note:
1. Alveoli are the last part.
2. The oesophagus carries food and not air.

Answer: (c) keep it from collapsing

Explanation:
1. The incomplete C shaped rings keep the windpipe open even when little air is in it.
2. Without them, the trachea could collapse and block the passage of air.

Teacher's Note:
1. The gap in the ring faces the oesophagus.
2. Vocal cords in the larynx produce sound.

Answer: (b) alveoli

Explanation:
1. Alveoli have thin walls and are surrounded by capillaries.
2. About 80 square metres of surface area is provided by the large number of alveoli.

Teacher's Note:
1. Alveoli are the structural and functional units of lungs.
2. The surface area is large so that diffusion is quick.

Answer: (a) Thick walls

Explanation:
1. Alveoli have very thin walls, so thick walls are not a feature.
2. Thin walls and many capillaries allow rapid diffusion of oxygen and carbon dioxide.

Teacher's Note:
1. Large area, thin wall and rich blood supply are the adaptations.
2. They are also kept moist.

Answer: (c) dissolved in plasma

Explanation:
1. Carbon dioxide is much more soluble in water than oxygen.
2. So most of it travels dissolved in the blood plasma.

Teacher's Note:
1. Oxygen needs a pigment because it is less soluble.
2. This is a common board question.

Answer: (b) the diaphragm contracts and ribs move up and out

Explanation:
1. Contraction of the diaphragm flattens it and the external intercostal muscles lift the ribs.
2. The chest cavity becomes larger, the air pressure in the lungs falls and air rushes in.

Teacher's Note:
1. Exhalation is the reverse.
2. Lungs have no muscles of their own.

Answer: (d) is a biochemical process that releases energy in all cells

Explanation:
1. Respiration oxidises food with the help of enzymes in every cell.
2. Breathing is the physical movement of air in and out of lungs, with no release of energy.

Teacher's Note:
1. Breathing supplies oxygen for respiration.
2. Respiration occurs in plants also, but they do not breathe.

Answer: (c) destroys the cilia in the respiratory tract

Explanation:
1. Cilia remove dust and germs, and when they are destroyed harmful substances reach the lungs.
2. This leads to infection, cough and may cause lung cancer.

Teacher's Note:
1. Tobacco also affects the heart, tongue and liver.
2. Chewing tobacco is a major cause of oral cancer.

Answer: (b) red blood corpuscles

Explanation:
1. Haemoglobin is present in RBCs and gives them their red colour.
2. Mature human RBCs are biconcave and without a nucleus.

Teacher's Note:
1. White blood cells fight infection.
2. Platelets help in blood clotting.

Answer: (a) Photosynthesis stores energy while respiration releases it

Explanation:
1. Photosynthesis is anabolic and stores light energy in food, while respiration is catabolic and releases energy.
2. Photosynthesis occurs only in green cells in presence of light and respiration occurs in all cells all the time.

Teacher's Note:
1. One uses CO2 and water, the other releases them.
2. The two processes are complementary in nature.