Life Processes-Q&A

Q1. What are the differences between autotrophic nutrition and heterotrophic nutrition?

Q2. Where do plants get each of the raw materials required for photosynthesis?

• Carbon Dioxide: Plants absorb carbon dioxide from the atmosphere through small pores on the surface of leaves called stomata, which regulate gas exchange.
• Water: Water is absorbed from the soil by plant roots. It travels up to the leaves through specialized vessels (xylem) where photosynthesis takes place.
• Sunlight: Sunlight is directly received by the exposed surfaces of leaves. The energy from sunlight is crucial for photosynthesis and is trapped by chlorophyll present in leaf cells.
• Chlorophyll: Chlorophyll is a green pigment that is naturally present in the leaves of plants. It helps capture sunlight, making photosynthesis possible.

Q3. What is the role of the acid in our stomach?

• It creates a highly acidic environment that helps break down and digest proteins in food by unraveling (denaturing) them, making it easier for digestive enzymes like pepsin to work effectively.
• The acid activates pepsinogen, turning it into the active digestive enzyme pepsin, which is essential for protein breakdown.
• It serves as a protective barrier, killing many harmful bacteria and pathogens that may be present in the food, thus helping prevent infections.
• The acidic environment also helps in the absorption of certain nutrients, such as iron, calcium, and vitamin \(B_{12}\), in the intestine.

In summary, stomach acid is crucial for efficient protein digestion, enzyme activation, defense against microorganisms, and nutrient absorption.

Q4. What is the function of digestive enzymes?

• Amylase breaks down starch (a carbohydrate) into simpler sugars.
• Protease enzymes such as pepsin and trypsin break down proteins into smaller peptides and amino acids.
• Lipase breaks down fats into fatty acids and glycerol.

Q5. How is the small intestine designed to absorb digested food?

Structural Adaptations:

• The inner lining of the small intestine has millions of tiny, finger-like projections called villi, which increase the surface area for absorption several times.
• Each villus contains even tinier hair-like structures called microvilli forming a “brush border,” further increasing the surface area for maximum nutrient absorption.
• The wall also has circular folds (plicae circulares) that help slow down the movement of food, allowing more time for absorption to occur.

Absorptive Mechanisms:

Villi

• Nutrients such as amino acids, sugars, vitamins, and minerals are absorbed through the epithelial cells of the villi into an extensive network of blood capillaries.
• Fats are absorbed by tiny lymph vessels called lacteals present within each villus.
• Absorption takes place through different mechanisms: diffusion, facilitated diffusion, osmosis, and active transport, depending on the nutrient.

These adaptations ensure that the digested food is efficiently absorbed and delivered to the bloodstream or lymphatic system for transport throughout the body.

Q6. What advantage over an aquatic organism does a terrestrial organism energy in various organisms?

• Oxygen concentration in air is much higher (about 21%) than in water. In water, oxygen is present in a dissolved form, and its concentration is very low compared to air.
• Terrestrial organisms do not have to expend much energy to obtain oxygen from the atmosphere. They can easily take in air containing sufficient oxygen through their respiratory organs (such as lungs).
• In contrast, aquatic organisms must take in water and extract the small amount of dissolved oxygen. This process requires them to breathe at a much faster rate, thereby spending more energy for obtaining the same amount of oxygen.

In Short: The advantage that terrestrial organisms have is that they can get oxygen from the air, where it is available in higher concentration. This makes the process of respiration easier and less energy-consuming compared to aquatic organisms, which need to extract oxygen that is present in very low concentrations in water.

Q7. How is oxygen and carbon dioxide transported in human beings?

Transport of Oxygen

• In human beings, oxygen is carried by the red blood cells.
• The respiratory pigment called haemoglobin present in red blood corpuscles has a very high affinity for oxygen.
• Oxygen from the lungs combines with haemoglobin to form oxyhaemoglobin.
• This allows oxygen to be efficiently transported by blood from the lungs to all the tissues of the body, where it is needed for cellular respiration.

Transport of Carbon Dioxide:

• Carbon dioxide is more soluble in water than oxygen.
• Most of the carbon dioxide produced during respiration is transported in the dissolved form in our blood plasma (about 70% as bicarbonate ions, the rest as carbamino compounds and dissolved \(CO_2\)).
• Only a small amount of carbon dioxide gets carried by haemoglobin.
• Carbon dioxide is finally brought back in dissolved form by the blood to the lungs, from where it is expelled during exhalation.

Q8. How are the lungs designed in human beings to maximise the area for exchange of gases?

• Inside the lungs, the air passage keeps dividing into smaller tubes called bronchioles.
• These bronchioles end in millions of tiny balloon-like structures called alveoli.
• The alveoli provide a very large surface area for the exchange of gases.
• The walls of alveoli are very thin and surrounded by a network of capillaries, which helps gases to pass easily between the blood and the air inside the alveoli.
• If all alveoli from human lungs are spread out, they would cover an area of about 80 to 100 square metres (almost the size of a tennis court).
• This large surface area and thin walls maximise the efficiency of gas exchange, allowing oxygen to diffuse into the blood and carbon dioxide to diffuse out of the blood quickly and efficiently.

Summary:The presence of millions of alveoli in the lungs, each with thin walls and surrounded by capillaries, increases the surface area and makes the exchange of gases (oxygen and carbon dioxide) highly efficient—as required by our body's needs.

Q9. What are the different ways in which glucose is oxidised to provide energy in various organisms?

1. Aerobic Respiration
   Occurs in the presence of oxygen.
   First, glucose (a six-carbon molecule) is broken down in the cytoplasm by the process called glycolysis to form pyruvate (a three-carbon molecule).
   In aerobic respiration, pyruvate enters the mitochondria and is completely broken down into carbon dioxide and water.
   This process releases a large amount of energy.
   Example: Most living organisms like humans, birds, and plants undergo aerobic respiration.
2. Anaerobic Respiration
   • Occurs in the absence of oxygen.
   • After glycolysis, the pyruvate is broken down differently:
     • In yeast and some bacteria, pyruvate is converted into ethanol and carbon dioxide (fermentation).
     • In human muscles during vigorous exercise (when oxygen supply is limited), pyruvate is converted into lactic acid.
   • This process releases less energy compared to aerobic respiration.
   • Example: Yeast (ethanol and \(CO_2\)), human muscles (lactic acid).

Q10.What are the component of the transport system in human beings what are the of these components?

1. Heart
   • The heart is a muscular organ that acts as a pump.
   • Its function is to pump blood throughout the body, ensuring that oxygenated blood reaches all body tissues and deoxygenated blood is sent to the lungs for purification.
2. Blood
   • Blood is a red-colored fluid connective tissue.
   • Its main function is to transport oxygen, carbon dioxide, nutrients, hormones, and waste products to and from different parts of the body.
   • It contains:
   • Red Blood Cells (RBCs): Carry oxygen.
   • White Blood Cells (WBCs): Help in defense against infections.
   • Platelets: Help in blood clotting.
3. Blood Vessels
   • These are tubular structures that carry blood all over the body.
   • There are three main types:
   • Arteries: Carry oxygenated blood away from the heart to different body parts.
   • Veins: Carry deoxygenated blood from body parts back to the heart.
   • Capillaries: Very thin blood vessels where the actual exchange of gases, nutrients, and wastes takes place between blood and tissues.

Q11. Why is it necessary to separate oxygenated and deoxygenated bloods in mammals and birds

• Warm-blooded: Mammals and birds are warm-blooded (endothermic) animals.
  They need to maintain a constant and relatively high body temperature regardless of external conditions.
• Efficient oxygen supply: Their cells require a steady and rich supply of oxygen for a high rate of metabolic activities which produce energy necessary for warmth and activity.
• Double circulatory system: The heart is divided into four chambers (two atria and two ventricles), so oxygen-rich (oxygenated) blood from the lungs never mixes with oxygen-poor (deoxygenated) blood from the body. This ensures only oxygen-rich blood is pumped to the organs, maximizing energy production.
• Why is separation necessary? If the oxygenated and deoxygenated blood mixed, the supply of oxygen to tissues would be less efficient, reducing the amount of energy produced through respiration. This would make it difficult for mammals and birds to sustain their high metabolism and maintain body temperature.

Summary:
The complete separation of oxygenated and deoxygenated blood in mammals and birds allows for an efficient supply of oxygen to body tissues, helps sustain high metabolic rates, and enables these animals to regulate their body temperature effectively, which is vital for their survival as warm-blooded organisms.

Q12. What are the components of the transport system in highly organised plants?

1. Xylem Transports water and dissolved minerals from roots to various parts of the plant.
   Components of Xylem
   • Tracheids
   • Vessels
   • Xylem fibres
   • Xylem parenchyma
   Movement direction: Mainly upward (from root to leaves).
2. Phloem Transports food (mainly sucrose) produced in leaves via photosynthesis to all parts of the plant.
   Components of Xylem
   • Sieve tubes
   • Companion cells
   • Phloem fibres
   • Phloem parenchyma
   Movement direction: Multi-directional (from leaves to roots, stems, fruits, etc.).
   
   These tissues form the vascular system in higher plants, ensuring efficient transport and distribution of water, minerals, and food materials to support growth and development.

Q13. How are water and minerals transported in plants?

• Absorption by roots: Water and minerals are absorbed from the soil by the root hairs through the process of osmosis (for water) and active transport/diffusion (for minerals).
• Movement to xylem: From the root hairs, water and dissolved minerals move cell to cell across the root cortex and finally reach the xylem vessels present in the root.
• Transport through xylem: Xylem vessels form continuous tubes from roots to leaves. They transport water and minerals upward through the stem to the leaves.
• Driving force (Transpiration pull): The main force for upward movement is the transpiration pull created due to evaporation of water from the stomata of leaves.
  • This creates a negative pressure (suction force) in the leaf xylem, pulling water upward.
  • Cohesion (water molecules stick to each other) and adhesion (water molecules stick to xylem walls) help maintain the continuous water column.
• Role of root pressure and capillary action:
  • Root pressure (generated by osmotic pressure in roots) and
  • Capillary action (rise of liquid in thin tubes) also aid in transport, but transpiration pull is the strongest force.

Summary: Water and minerals are absorbed by root hairs from the soil and conducted through xylem vessels to all parts of the plant. Their upward movement is mainly due to transpiration pull, with the help of cohesion, adhesion, root pressure, and capillary action.

Q14. How is food transported in plants?

• The movement of food in phloem takes place with the help of sieve tubes and companion cells.
• It requires energy (ATP) because the transport can occur in both upward and downward directions, depending on the need of the plant.
• Food moves as a solution of sugars (mainly sucrose) from source (leaves) to sink (roots, fruits, stems, storage organs).

Summary: Food in plants is transported by the phloem through a process called translocation, where sugars move from leaves (source) to other parts of the plant (sink) with the help of energy.

Q15. Describe the structure and functioning of nephrons.

1. Structure of Nephron:
   • Nephron is the basic structural and functional unit of the kidney.
   • Each kidney has about 1 million nephrons.
   • A nephron consists of:
     • Bowman’s capsule: a cup-shaped structure containing a bundle of capillaries called the glomerulus.
     • Glomerulus: network of capillaries where filtration of blood takes place.
     • Tubule: long coiled tube divided into proximal tubule, loop of Henle, and distal tubule.
     • Collecting Duct: It Receives fluid from multiple nephrons.
       It is a Final site for water reabsorption; carries urine to the renal pelvis.
2. Functioning of Nephron:
   • Ultrafiltration: Blood enters the glomerulus under pressure; water, salts, glucose, urea, etc., filter into Bowman’s capsule.
   • Selective reabsorption: Useful substances like glucose, amino acids, most water, and salts are reabsorbed from the tubule into the blood.
   • Tubular secretion: Additional wastes like excess ions are secreted into the tubule.
   • Urine formation: The remaining liquid (mostly urea, excess salts, and water) is urine, which collects in the collecting duct and finally passes to the ureter.

Summary: Nephron is the functional unit of the kidney, made up of Bowman’s capsule, glomerulus, tubule, and collecting duct. It filters blood, reabsorbs useful substances, and removes wastes. Thus, it helps in the formation of urine and maintains the balance of water and salts in the body.

Q16. What are the methods used by plants to get rid of excretory products?

1. Oxygen and Carbon dioxide
   • During photosynthesis, plants give out oxygen as a waste product.
   • During respiration, carbon dioxide is released.
   • These gases diffuse out through stomata in leaves and lenticels in stems.
2. Excess water
   • Removed by the process of transpiration through stomata.
3. Other wastes
   • Some waste products are stored in leaves, bark, or old xylem (wood), which later fall off.
   • Certain wastes (e.g., resins, gums, latex, oils) are stored in special cells or ducts.
   • In some plants, wastes are also excreted into the surrounding soil.

Summary: Plants get rid of wastes by diffusion of gases \((O_2,~ CO_2)\) through stomata and lenticels, by transpiration of extra water, by storing wastes in leaves, bark, or old xylem (which later shed), and by storing or secreting substances like gums, resins, and latex.

Q17. How is the amount of urine produced?

The amount of urine produced in the human body, is mainly regulated by two factors: the volume of blood and the amount of antidiuretic hormone (ADH).

Q18. What are the different ways in which glucose is oxidised to provide energy in various organisms?

Ways in which glucose is oxidised to provide energy

1. Glycolysis: In the cytoplasm, glucose is broken into pyruvate.
2. Pyruvate:
   • Aerobic respiration:
     • Pyruvate enters mitochondria and gets completely broken down into \(CO_2\) and \(H_2O\).
     • Large amount of energy is released (≈ 36 ATP molecules).
   • Anaerobic respiration:
     • In yeast and some microbes, pyruvate is converted into ethanol and \(CO_2\).
     • Less energy is released (≈ 2 ATP).
   • In lack of oxygen:
     • Pyruvate is converted into lactic acid.
     • This causes muscle cramps and releases very little energy.

Summary: Glucose is first broken into pyruvate. In the presence of oxygen, pyruvate is completely oxidised in mitochondria to \(CO_2\) and \(H_2O\) (aerobic respiration). In absence of oxygen, it is converted to ethanol and \(H_2O\) (anaerobic respiration in yeast). In muscles, due to lack of oxygen, it forms lactic acid.

Q19. How is oxygen and carbon dioxide transported in human beings?

Transport of Oxygen and Carbon Dioxide in Humans

1. Transport of Oxygen \((O_2)\):
   • Oxygen is absorbed by the lungs and enters the blood.
   • About 98% of oxygen binds with haemoglobin in red blood cells to form oxyhaemoglobin.
   • The remaining 2% dissolves in plasma.
   • Oxygen is carried to all body cells, where it is used in cellular respiration.
2. Transport of Carbon Dioxide \((CO_2)\):
   \((CO_2)\) produced by cells during respiration, is transported back to the lungs in three ways:
   • About 70% as bicarbonate ions \((HCO_3^⁻)\) in plasma.
   • About 23% bound to haemoglobin as carbaminohaemoglobin
   • About 7% dissolved directly in plasma.

Summary: Oxygen is mostly carried by haemoglobin as oxyhaemoglobin, and a small amount is dissolved in plasma. Carbon dioxide is transported mainly as bicarbonate ions, some bound to haemoglobin, and a little dissolved in plasma.