Biology Notes

Photosynthesis

• Photosynthesis is a process where plants make glucose using sunlight.
• Photosynthesis equation: carbon dioxide + water $\rightarrow$ glucose + oxygen
• Carbon dioxide enters leaves through stomata.

Digestive System

• A balanced diet includes carbohydrates, lipids, proteins, vitamins, minerals, fiber, and water.
• Carbohydrates and lipids provide energy.
• Proteins are for growth and repair.
• Vitamins are vital for many processes.
• Minerals, like iron and calcium, are essential.
• Fiber aids digestion.
• Food energy is measured in joules (J) or kilojoules (kJ).
• Unbalanced diets can lead to obesity, starvation, and deficiency diseases.
• Digestion breaks down food into absorbable particles.
• Mechanical digestion: chewing and stomach churning.
• Chemical digestion: enzymes break down food.
• Digestive system: mouth, oesophagus, stomach, liver, pancreas, small & large intestine, rectum, anus.
• Intestinal bacteria aid digestion and prevent harmful bacteria growth.
• Villi in the small intestine increase surface area for absorption.
• Enzymes are biological catalysts that speed up reactions.

Gas Exchange System

• The gas exchange system provides oxygen to the blood and removes carbon dioxide.
• Components: trachea, bronchi, bronchioles, alveoli, intercostal muscles, and diaphragm.
• Gas exchange occurs in alveoli.
• Alveoli have moist, thin walls and a large surface area for diffusion.
• Breathing involves inhaling and exhaling.
• Inhalation: muscles contract, lung volume increases, air enters.
• Exhalation: muscles relax, lung volume decreases, air exits.
• Lung capacity is affected by exercise, asthma, and smoking.
• Smoking can cause lung and heart disease, and cancer.
• During exhalation, the diaphragm relaxes and moves upwards, and the intercostal muscles relax and move downwards and inwards.

Health and Disease

• Health includes physical, mental, and social well-being.
• Disease affects the body's functions.
• Communicable diseases are transmittable and caused by pathogens.
• Pathogens are micro-organisms that cause disease.
• Antibiotics kill bacteria.
• Vaccines protect against pathogens.
• Non-communicable diseases are non-transmittable.
• Drugs affect the body; medicines treat pain or disease.
• Recreational drugs can impact health and behavior.
• Mental health issues include anxiety and depression.