Key Concepts
- 1What is photosynthesis equation?
- 2What is double circulation?
Important Formulas & Facts
6CO₂ + 6H₂O + Sunlight → C₆H₁₂O₆ + 6O₂ (in chloroplasts). Chlorophyll absorbs light. Carbon fixation in stomata. Glucose is the food.
Blood passes through the heart twice in one complete cycle. Pulmonary circulation (heart↔lungs for oxygenation) + Systemic circulation (heart↔body for delivering O₂). Ensures no mixing of oxygenated and deoxygenated blood.
Must-Know Questions
Q1The site of photosynthesis in a cell is:
Photosynthesis occurs in the chloroplasts. Chloroplasts contain the green pigment chlorophyll, which absorbs sunlight for photosynthesis. The equation is: 6CO₂ + 6H₂O →(sunlight, chlorophyll) C₆H₁₂O₆ + 6O₂.
Q2What is the role of HCl in the stomach?
HCl (hydrochloric acid) secreted by the gastric glands in the stomach wall plays the following roles: 1. Creates an acidic medium (pH ~2) required for the activation of the enzyme pepsinogen into pepsin. 2. Pepsin works in acidic medium to digest proteins. 3. Kills bacteria and other germs that enter with food. 4. Helps in the breakdown of food particles.
Q3Name the largest artery and the largest vein in the human body.
The largest artery is the aorta, which carries oxygenated blood from the left ventricle to all parts of the body. The largest vein is the vena cava (superior and inferior), which carries deoxygenated blood from the body back to the right atrium of the heart.
Q4What are the differences between aerobic and anaerobic respiration?
Aerobic Respiration: 1. Occurs in the presence of oxygen. 2. Complete breakdown of glucose. 3. Products: CO₂ + H₂O + 38 ATP (energy). 4. Occurs in cytoplasm + mitochondria. 5. Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (38 ATP). 6. Occurs in most organisms. Anaerobic Respiration: 1. Occurs in the absence of oxygen. 2. Incomplete breakdown of glucose. 3. Products: Ethanol + CO₂ + 2 ATP (in yeast) OR Lactic acid + 2 ATP (in muscles). 4. Occurs only in cytoplasm. 5. Equation (yeast): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + Energy (2 ATP). 6. Occurs in yeast, some bacteria, and in muscle cells during heavy exercise. Aerobic respiration produces much more energy (38 ATP vs 2 ATP).
Q5Why is the small intestine the main site of absorption of food?
The small intestine is the main site of absorption because: 1. It has finger-like projections called villi that greatly increase the surface area for absorption. 2. Villi are richly supplied with blood capillaries and lacteals (lymph vessels) for efficient transport. 3. The wall of the villi is very thin (one cell thick) for easy passage of nutrients. 4. The small intestine is very long (~6-7 metres), providing ample time and surface for absorption. 5. Complete digestion of carbohydrates, proteins, and fats occurs here, making nutrients available for absorption.
Practice Life Processes
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