CBSE Class 10 Science HOTs Life Processes Set 03

CASE-BASED QUESTIONS

Three main regions of the small intestine are the duodenum, the jejunum, and the ileum. The small intestine is where digestion is completed and virtually all absorption occurs. These two activities are facilitated by structural adaptations that increase the mucosal surface area by 600-fold, including circular folds, villi, and microvilli. There are around 200 million microvilli per square millimeter of small intestine, which contain brush border enzymes that complete the digestion of carbohydrates and proteins. Combined with pancreatic juice, intestinal juice provides the liquid medium needed to further digest and absorb substances from chyme large intestine. The main regions of the large intestine are the cecum, the colon, and the rectum. The large intestine absorbs water and forms feces, and is responsible for defecation.

Question. What is the function of large intestine?
Answer: The main functions of the large intestine are the absorption of water and electrolytes from the remaining indigestible food matter, the formation of feces, and the temporary storage of waste material before defecation.

Question. What controls the exit of waste material from intestine?
Answer: The exit of waste material (feces) from the rectum through the anus is controlled by the anal sphincter.

Question. How is the area of absorption increased in small intestine?
Answer: The surface area for absorption in the small intestine is increased by structural adaptations such as circular folds, finger-like projections called villi, and microscopic projections on the surface of cells called microvilli.

Question. What are the enzymes secreted by pancreatic juice?
Answer: Pancreatic juice contains enzymes like trypsin (for digesting proteins), lipase (for breaking down emulsified fats), and pancreatic amylase (for digesting starch).

Respiratory disease causes an immense worldwide health burden. It is estimated that 235 million people suffer from asthma, more than 200 million people have chronic obstructive pulmonary disease (COPD), 65 million endure moderate-to-severe COPD, more than 100 million adult population experience sleep disordered breathing, 8.7 million people develop tuberculosis (TB) annually, millions live with pulmonary hypertension and more than 50 million people struggle with occupational lung diseases. At least 2 billion people are exposed to the toxic effects of biomass fuel consumption, 1 billion are exposed to outdoor air pollution and 1 billion are exposed to tobacco smoke. Each year, 4 million people die prematurely from chronic respiratory disease. Infants and young children are particularly susceptible. Nine million children under 5 years of age die annually and lung diseases are the most common causes of these deaths. Pneumonia is the world’s leading killer of young children. Asthma is the most common chronic disease, affecting about 14% of children globally and is still rising. COPD is the fourth leading cause of death worldwide and the numbers are growing. The most common lethal cancer in the world is lung cancer, which kills more than 1.4 million people each year, and the numbers are growing. Respiratory tract infections caused by influenza kill 250,000–500,000 people and cost 71–167 billion US dollars annually. Respiratory infections are ranked as the greatest single contributor to the overall burden of disease in the world.

Question. Write one difference between respiration in plants and respiration in animals.
Answer: In plants, respiration occurs through individual parts (leaves, stems, roots) via simple diffusion, and there is no specialized respiratory system. In animals, there is a complex and specialized respiratory system (like lungs or gills) to facilitate gas exchange for the entire body.

Question. Define cilia.
Answer: Cilia are tiny, hair-like projections found on the lining of the respiratory tract that move in a rhythmic fashion to sweep out dust, pathogens, and mucus away from the lungs.

Question. How are lungs designed to maximize exchange of gases?
Answer: Lungs contain millions of tiny, balloon-like structures called alveoli. These provide a massive surface area for gas exchange. The walls of the alveoli are extremely thin and are surrounded by an extensive network of thin-walled blood capillaries, allowing for rapid diffusion of gases.

Question. ‘While breathing cycle is rhythmic, exchange of gases is a continuous process.’ Justify.
Answer: Breathing involves a rhythmic cycle of inhalation and exhalation. However, during the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for carbon dioxide to be released, making the exchange of gases a continuous process.

The heart is a pumping organ that receives blood from the veins and pumps it into the arteries. It is situated in the thoracic cavity which lies above the diaphragm between the two lungs. It is enclosed in a double walled membraneous sac.

Question. Name the double walled membranous sac that encloses the heart.
Answer: Pericardium.

Question. What is the function of valves in the heart?
Answer: Valves ensure that blood flows only in one direction and prevent the backflow of blood when the atria or ventricles contract.

Question. The left ventricle of the heart has a thicker wall than the right ventricle. Explain.
Answer: The left ventricle has to pump oxygenated blood to all the distant parts of the body under high pressure, whereas the right ventricle only pumps deoxygenated blood to the nearby lungs. Therefore, the left ventricle requires thicker muscular walls to generate the necessary pressure.

Question. Give two differences between auricles and ventricles.
Answer:
1. Auricles (atria) are the upper receiving chambers of the heart, while ventricles are the lower pumping chambers.
2. Auricles have relatively thin walls because they only push blood into the ventricles, whereas ventricles have thick muscular walls to pump blood to the lungs or the rest of the body.

During photosynthesis, green plants synthesise organic materials they require from inorganic source. Light is a source of energy for this synthesis.

Question. Mention the raw materials required for photosynthesis.
Answer: The raw materials required for photosynthesis are carbon dioxide (\( CO_2 \)), water (\( H_2O \)), sunlight, and chlorophyll.

Question. Where does photosynthesis mostly take place in a plant?
Answer: Photosynthesis mostly takes place in the leaves, specifically within the chloroplasts of the mesophyll cells.

Question. Write the balanced chemical equation for the process of photosynthesis.
Answer: \( 6CO_2 + 12H_2O \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} C_6H_{12}O_6 + 6H_2O + 6O_2 \)

Question. When do the desert plants take up carbon dioxide and perform photosynthesis?
Answer: Desert plants take up carbon dioxide at night to prevent water loss through transpiration during the hot day. They store it as an intermediate (malic acid) and use the energy absorbed by chlorophyll during the day to perform the final steps of photosynthesis.

Plants lose water in vapour form from the aerial parts by the process of transpiration. Besides removal of excess water, transpiration also helps in upward movement of cell sap, to regulate temperature of the plant and helps to absorb and distribute the salt.

Question. What is ascent of sap?
Answer: The upward movement of water and minerals (sap) from the roots to the top parts of the plant through the xylem tissue is called the ascent of sap.

Question. Name the vascular tissues which conduct water and translocate food.
Answer: Xylem conducts water and minerals, and Phloem translocates food.

Question. Write two difference(s) between transpiration and translocation.
Answer:
1. Transpiration is the loss of water in the form of vapour from aerial parts of the plant, while translocation is the transport of soluble products of photosynthesis (food).
2. Transpiration occurs mainly through xylem and is a physical process driven by suction, while translocation occurs through phloem and requires energy in the form of ATP.

Question. Explain the mechanism of opening and closing of stomata.
Answer: The opening and closing of stomatal pores is controlled by the guard cells. When water flows into the guard cells, they swell and become turgid, causing the pore to open. When the guard cells lose water and shrink, the pore closes.

The glucose breakdown pathway in case of aerobic respiration is shown in the flow chart given below.
Glucose \(\xrightarrow{\text{In cytoplasm}}\) A \(\xrightarrow{\text{In absence of } O_2}\) B
Glucose \(\xrightarrow{\text{In cytoplasm}}\) A \(\xrightarrow{\text{In presence of } O_2 \text{ (In Mitochondria)}}\) \( CO_2 + H_2O + \text{Energy} \)

Question. Identify A and B in the flow chart.
Answer: A is Pyruvate (a 3-carbon molecule). B is Ethanol + Carbon dioxide (in yeast) or Lactic acid (in muscle cells).

Question. Give one point which is common for both aerobic and anaerobic respiration.
Answer: Both processes begin with glycolysis, which is the breakdown of glucose into pyruvate in the cytoplasm, and both release energy.

Question. Why is anaerobic respiration less efficient?
Answer: Anaerobic respiration is less efficient because glucose is only partially broken down, resulting in the release of much less energy (only 2 ATP molecules) compared to aerobic respiration.

Question. State the basic difference between the process of respiration and photosynthesis.
Answer: Respiration is a catabolic process that breaks down food (glucose) to release energy and produces \( CO_2 \), whereas photosynthesis is an anabolic process that uses light energy to synthesize food (glucose) and consumes \( CO_2 \).

Green plants are called the life supporters of the world as they synthesise food by using the sunlight by the process of photosynthesis. The food prepared by green plants supports all other life on our planet earth. The leaves are called kitchen of the plants. Water also plays an important role in plant life processes like transpiration and photosynthesis.

Question. You must have seen the plants on the road side are mostly covered with certain deposits like dust and smoke. Mention three processes which may be hampered due to the dust and smoke on the leaves. Write a chemical reaction to show the process of photosynthesis.
Answer: The three processes hampered are Photosynthesis, Transpiration, and Respiration (Gaseous exchange).
Chemical reaction: \( 6CO_2 + 12H_2O \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} C_6H_{12}O_6 + 6H_2O + 6O_2 \)

Question. The food prepared by the leaves is transported to other parts of the plant. How is food transported in plants?
Answer: Food is transported in plants through the phloem tissue by a process called translocation. This process uses energy from ATP to create osmotic pressure that moves the food from areas of high concentration (leaves) to areas of low concentration (other parts of the plant).

Question. Name the elements of xylem which transport water and minerals in the upward direction. Explain the mechanism of transport of water and minerals in plants.
Answer: The elements of xylem are vessels and tracheids. The mechanism involves two main forces: root pressure (due to active intake of ions creating an osmotic gradient) and transpiration pull (evaporation of water from leaves creates a suction force that pulls the water column upwards from the roots).

QUESTIONS

Question. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
Answer: In multicellular organisms, only the cells of skin are in direct contact with the environment. Diffusion is a very slow process and it will take very long time to reach all the cells of the body part. Diffusion is insufficient to meet oxygen requirement.

Question. What criteria do we use to decide whether something is alive?
Answer: If something shows any one of the following characteristics, then it is a living being:
(i) It can move on its own.
(ii) It needs food to get energy and nutrients.
(iii) It respires.
(iv) It responds to changes that take place in its surroundings.
(v) It exhibits growth and development.
(vi) It removes its metabolic wastes.

Question. What are outside raw materials used for by an organism?
Answer: All organisms take in oxygen, water and food as raw material from the outside. As plants make their own food by the process of photosynthesis and they need carbon dioxide and water as raw material for photosynthesis.

Question. What processes would you consider essential for maintaining life?
Answer: Nutrition, respiration, transportation, excretion are some processes that are essential for maintaining life.

Question. What are the differences between autotrophic nutrition and heterotrophic nutrition?
Answer:
Autotrophic nutrition:
(a) Autotrophic nutrition implies that the organism prepares its own food and is not dependent on any other organism for its food.
(b) In autotrophic nutrition, organic material is prepared from inorganic materials like carbon dioxide and water by utilizing the sunlight energy.
(c) Green plants and certain bacteria perform autotrophic mode of nutrition.
Heterotrophic nutrition:
(a) Heterotrophic nutrition implies that the organism is not able to prepare its own food and is dependent on other organisms for its food.
(b) In heterotrophic nutrition organic material cannot be prepared from inorganic materials like carbon dioxide and water.
(c) Animals and non-green plants perform heterotrophic mode of nutrition.

Question. Where do plants get each of the raw materials required for photosynthesis?
Answer:
1. Carbon dioxide: From Atmosphere
2. Water: From Ground water
3. Solar energy: From Sun

Question. What is the role of the acid in our stomach? 
Answer: The acid found in our stomach is hydrochloric acid. It helps to kill harmful germs which may have come along with food. Stomach acid activates the enzyme pepsin for digestion of protein.

Question. What is the function of digestive enzymes?
Answer: The function of digestive enzyme is to speed up the process of breaking up of complex molecules into simpler and absorbable molecules so that it is easier for the body to absorb food.

Question. How is the small intestine designed to absorb digested food?
Answer: In the small intestine, the innermost layer is in the shape of finger like projections known as villi. Several folds of villi increase the absorbing surface area of small intestine. The blood capillaries in villi help to absorb simpler molecules from food.

Question. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Answer: The amount of oxygen dissolved in water is very low as compared to the amount of oxygen present in the air. Because of this, terrestrial organisms have to make less efforts for obtaining oxygen for respiration than the aquatic organisms.

Question. What are the different ways in which glucose is oxidised to provide energy in various organisms?
Answer: There are two types of respiration for oxidisation of glucose.
(a) Aerobic respiration: In this process, complete oxidation of glucose is involved hence, optimum output of energy is achieved. This process takes place in presence of oxygen.
(b) Anaerobic respiration: This process takes place in the absence of oxygen hence, complete oxidation of glucose does not take place. Usually, bacteria shows anaerobic respiration. Even sometimes in our calf muscles, anaerobic respiration takes place.

Question. How is oxygen and carbon dioxide transported in human beings?
Answer: Oxygen and carbon dioxide are transported in human beings with a gas transportation system. This system is mainly composed of following parts:
Lungs: Lungs help in breathing in oxygen-rich air and breathing out carbon dioxide-rich air.
Heart: Heart pumps deoxygenated blood to lungs for oxygenation and pumps oxygenated blood to different organs of the body.
Veins: Veins usually carry deoxygenated blood from different parts of the body to the heart. One exception is the pulmonary vein which carries oxygenated blood from lungs to heart.
Arteries: Arteries usually carry oxygenated blood from heart to different parts of the body. One exception is the pulmonary artery which carries deoxygenated blood from heart to lungs.

Question. How are the lungs designed in human beings to maximise the area for exchange of gases?
Answer: In the lungs, the air-passage divides into smaller tubes called bronchi which form bronchioles. The bronchioles terminate in balloon-like structures called alveoli. The alveoli present in the lungs provide maximum surface area for exchange of gases. The alveoli have very thin walls and contain an extensive network of blood vessels to facilitate exchange of gases.