Life Processes - Questions and Answers

Plants obtain raw materials for photosynthesis from:

• Carbon dioxide: From the atmosphere through stomata in leaves
• Water: From the soil through roots
• Sunlight: From the sun, absorbed by chlorophyll
• Minerals: From the soil (nitrogen, phosphorus, iron, magnesium, etc.)

The role of hydrochloric acid in our stomach includes:

• Creating an acidic medium (pH 1-2) that facilitates the action of the enzyme pepsin
• Killing harmful bacteria that might be present in food
• Denaturing proteins, making them easier to digest

Functions of digestive enzymes include:

• Breaking down complex food molecules into simpler, absorbable forms
• Speeding up the digestion process (acting as biological catalysts)
• Enabling the body to absorb nutrients efficiently
• Examples: Amylase breaks down starch, pepsin breaks down proteins, lipase breaks down fats

The small intestine is designed for efficient absorption through:

• Large surface area: It is very long and highly coiled
• Villi: Finger-like projections on the inner lining that increase surface area
• Microvilli: Microscopic projections on villi that further increase surface area
• Rich blood supply: Villi contain blood vessels that transport absorbed nutrients
• Thin walls: Single-cell thick epithelium for easy diffusion

Terrestrial organisms have the advantage of:

• Access to atmospheric air which contains a much higher concentration of oxygen (about 21%) compared to dissolved oxygen in water
• Not needing to filter large volumes of medium to extract oxygen
• Having more efficient respiratory systems adapted to extract oxygen from air
• Lower breathing rate compared to aquatic organisms

Glucose can be oxidized through different pathways:

• Aerobic respiration: In the presence of oxygen, glucose is completely broken down into CO₂ and water, releasing maximum energy. Occurs in mitochondria.
• Anaerobic respiration in yeast: In the absence of oxygen, glucose is broken down into ethanol and CO₂, releasing less energy.
• Anaerobic respiration in muscles: During heavy exercise when oxygen supply is insufficient, glucose is broken down into lactic acid, releasing less energy.

Transport of gases in human beings:

• Oxygen transport:
  • Most oxygen (about 97%) is transported by hemoglobin in red blood cells as oxyhemoglobin
  • A small amount is dissolved directly in plasma
• Carbon dioxide transport:
  • Most carbon dioxide (about 70%) is transported as bicarbonate ions in plasma
  • About 20-25% is transported by hemoglobin as carbaminohemoglobin
  • A small amount is dissolved directly in plasma

The lungs are designed to maximize gas exchange through:

• Alveoli: Millions of tiny, balloon-like structures that provide a massive surface area (about 80 m²)
• Thin walls: Alveolar walls are extremely thin (one-cell thick) for easy diffusion
• Rich blood supply: Dense network of capillaries surrounding each alveolus
• Moist surface: Helps in dissolving gases for efficient exchange
• Large surface area to volume ratio: Maximizes contact between air and blood

Components of human transport system and their functions:

Separation of oxygenated and deoxygenated blood is necessary because:

• It allows highly efficient supply of oxygen to the body
• Mammals and birds have high energy needs to maintain constant body temperature (warm-blooded)
• Prevents mixing which would reduce the oxygen-carrying capacity of blood
• Ensures that tissues receive blood with maximum oxygen content
• Supports their active lifestyle and high metabolic rate

Components of plant transport system:

• Xylem: Transports water and minerals from roots to other parts of the plant
• Phloem: Transports products of photosynthesis (food) from leaves to other parts of the plant

Water and minerals are transported in plants through xylem tissue by:

• Root pressure: Active transport of ions into root xylem creates osmotic pressure that pushes water upward
• Transpiration pull: Evaporation of water from leaves creates suction that pulls water upward through the xylem
• Capillary action: Water moves upward in narrow tubes due to adhesion and cohesion forces

Food is transported in plants through phloem tissue by:

• Translocation: Process of transporting soluble products of photosynthesis
• Energy-requiring process: Unlike xylem transport, phloem transport requires energy (ATP)
• Pressure flow mechanism:
  • Sugars are actively loaded into phloem sieve tubes
  • This increases osmotic pressure, drawing in water
  • The resulting pressure moves the sap to areas of lower pressure
  • Sugars are unloaded at sink tissues (growing parts, storage organs)
• Transport occurs in both upward and downward directions

Structure of nephron:

• Basic filtration unit of the kidney
• Consists of a cluster of thin-walled capillaries called glomerulus
• Glomerulus is surrounded by Bowman's capsule (cup-shaped end of nephron tubule)
• Tubular part of nephron has different regions with specific functions
• Connected to collecting duct which leads to ureter

Functioning of nephron:

• Filtration: Blood is filtered in glomerulus under pressure, forming filtrate in Bowman's capsule
• Reabsorption: As filtrate passes through tubule, useful substances (glucose, amino acids, salts, water) are selectively reabsorbed into blood
• Secretion: Additional wastes are actively secreted into tubule from blood
• Urine formation: Remaining fluid with concentrated wastes becomes urine, which passes to collecting duct and then to ureter

Plants use various methods to excrete waste products:

• Gaseous wastes: Oxygen (from photosynthesis) and CO₂ (from respiration) are removed through stomata
• Excess water: Removed through transpiration
• Storage in tissues: Many wastes are stored in cellular vacuoles
• Storage in dead tissues: Wastes stored in old xylem as resins and gums
• Leaf fall: Waste products stored in leaves that are shed
• Excretion into soil: Some wastes are excreted into the surrounding soil

The amount of urine produced is regulated by:

• Reabsorption of water: In kidney tubules, amount of water reabsorbed depends on body's hydration status
• Hormonal control:
  • Antidiuretic hormone (ADH) increases water reabsorption when body is dehydrated
  • When ADH is low, more water is excreted in urine
• Concentration of dissolved wastes: More concentrated wastes require more water for excretion
• Nervous control: Urinary bladder is under nervous control, allowing voluntary urination

Answer: (c) excretion.

Answer: (a) transport of water.

Answer: (d) all of the above.

Answer: (b) mitochondria.

Fat digestion process:

• Fats are first emulsified by bile salts from liver in small intestine
• Emulsification breaks large fat globules into smaller ones, increasing surface area for enzyme action
• Pancreatic lipase then breaks down emulsified fats into fatty acids and glycerol
• These simpler molecules are absorbed by intestinal cells

Location: Fat digestion primarily occurs in the small intestine.

Role of saliva in digestion:

• Moistens food, making it easier to swallow
• Contains salivary amylase enzyme that begins starch digestion
• Helps in dissolving food particles for tasting
• Cleanses the mouth and has antibacterial properties

Necessary conditions for autotrophic nutrition:

• Carbon dioxide
• Water
• Sunlight (as energy source)
• Chlorophyll (to absorb sunlight)
• Suitable temperature

By-products: Oxygen and water are by-products of photosynthesis.

Organisms using anaerobic respiration: Yeast, some bacteria, muscle cells during heavy exercise.

Alveoli are designed to maximize gas exchange through:

• Numerous in number (millions), providing enormous surface area (about 80 m²)
• Thin walls (one-cell thick) for easy diffusion
• Rich blood supply with dense capillary network
• Moist surface to dissolve gases
• Elastic walls that expand during inhalation

Consequences of hemoglobin deficiency (anemia):

• Reduced oxygen-carrying capacity of blood
• Fatigue and weakness due to insufficient oxygen supply to tissues
• Shortness of breath, especially during physical activity
• Pale skin and mucous membranes
• Dizziness and headaches
• Reduced ability to perform physical work
• In severe cases, can lead to organ damage

Double circulation: Blood passes through the heart twice during one complete cycle around the body.

• Pulmonary circulation: Deoxygenated blood from right ventricle → lungs → oxygenated blood back to left atrium
• Systemic circulation: Oxygenated blood from left ventricle → body tissues → deoxygenated blood back to right atrium

Necessity:

• Ensures complete separation of oxygenated and deoxygenated blood
• Maintains high blood pressure for efficient systemic circulation
• Provides sufficient oxygen supply to meet high metabolic demands
• Supports maintenance of constant body temperature in warm-blooded animals