Topic 2 | Organisation Flashcards
What are the levels of organisation in living things?
Cells → Tissues → Organs → Organ Systems. For example, cells form tissues like muscular tissue, tissues form organs like the stomach, and organs form organ systems like the digestive system.
What are the main organs of the human digestive system and their functions?
Glands (e.g., salivary glands, pancreas) produce digestive juices containing enzymes. Stomach produces hydrochloric acid to kill bacteria and provide the optimum pH for enzymes. Small intestine absorbs soluble molecules into the blood. Liver produces bile, stored in the gallbladder, to help digest lipids. Large intestine absorbs water from undigested food, producing faeces.
What are enzymes and how do they work?
Enzymes are biological catalysts that speed up chemical reactions without being used up. They have an active site where the substrate binds, following the lock and key hypothesis. Enzymes are proteins and require an optimum pH and temperature to function.
Explain the lock and key hypothesis.
The lock and key hypothesis states that the shape of the substrate is complementary to the shape of the enzyme’s active site. When they bind, they form an enzyme-substrate complex, allowing the reaction to occur.
What are the optimum conditions for enzymes?
Most enzymes have an optimum temperature around 37°C (body temperature) and an optimum pH of 7. However, enzymes in the stomach have a lower optimum pH due to the acidic environment.
What happens when an enzyme is denatured?
When an enzyme is denatured, the bonds in its structure break, changing the shape of the active site. This prevents the substrate from binding, and the enzyme can no longer function.
What are the main types of digestive enzymes and their functions?
Carbohydrases (e.g., amylase) break down carbohydrates into simple sugars. Proteases (e.g., pepsin) break down proteins into amino acids. Lipases break down lipids into fatty acids and glycerol.
What are the tests for carbohydrates, proteins, and lipids?
Benedict’s test for sugars (turns brick red). Iodine test for starch (turns blue-black). Biuret test for protein (turns purple). Emulsion test for lipids (add ethanol, results in a cloudy layer).
What are the roles of bile in digestion?
Bile is produced in the liver and stored in the gallbladder. It neutralises stomach acid and emulsifies fats, breaking them into smaller droplets to increase the surface area for lipase to act.
What is the structure and function of the heart?
The heart is a muscular organ with four chambers (two atria and two ventricles). It pumps blood around the body in a double circulatory system: one circuit to the lungs for oxygenation and another to the body to deliver oxygen.
What are the three types of blood vessels and their functions?
Arteries carry oxygenated blood away from the heart under high pressure. Veins carry deoxygenated blood back to the heart under low pressure and have valves to prevent backflow. Capillaries allow the exchange of substances between blood and tissues due to their thin walls.
How does gas exchange occur in the lungs?
Gas exchange occurs in the alveoli, where oxygen diffuses from the air into the blood, and carbon dioxide diffuses from the blood into the air. The alveoli are adapted with a large surface area, thin walls, and a good blood supply.
What are the components of blood and their functions?
Plasma carries blood cells, nutrients, and waste products. Red blood cells carry oxygen using haemoglobin. White blood cells are part of the immune system and fight pathogens. Platelets help blood clot at wound sites.
What is coronary heart disease and how can it be treated?
Coronary heart disease occurs when coronary arteries are blocked by fatty deposits, reducing blood flow to the heart. Treatments include stents to keep arteries open and statins to lower cholesterol.
What are non-communicable diseases and what factors increase their risk?
Non-communicable diseases are not infectious and include heart disease and cancer. Risk factors include poor diet, lack of exercise, smoking, and genetic predisposition.
What are the differences between benign and malignant tumours?
Benign tumours are non-cancerous, grow slowly, and do not spread to other tissues. Malignant tumours are cancerous, grow rapidly, and can spread to other parts of the body, forming secondary tumours.
What are the main plant tissues and their functions?
Epidermal tissue reduces water loss. Palisade mesophyll is where most photosynthesis occurs. Spongy mesophyll allows gas exchange. Xylem transports water and minerals. Phloem transports food substances.
What is transpiration and what factors affect its rate?
Transpiration is the loss of water vapour from leaves. Factors affecting its rate include temperature, humidity, air movement, and light intensity.
What is the role of guard cells in plants?
Guard cells control the opening and closing of stomata, allowing gas exchange and regulating water loss through transpiration.
What is translocation in plants?
Translocation is the movement of food substances (e.g., sugars) through the phloem from leaves to other parts of the plant for use or storage.
