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neurologyYou need to know

• A tissue is a group of specialised cells working together to perform a particular function, such as muscle tissue contracting to move food along the gut.
• An organ is a structure made from different tissues working together to perform a particular function, such as the stomach digesting food using muscular, glandular and epithelial tissues.
• The main organs of the human digestive system are the mouth, oesophagus, stomach, liver, gall bladder, pancreas, small intestine, large intestine, rectum and anus.
• Food travels through the digestive system in the order mouth, oesophagus, stomach, small intestine, large intestine, rectum and anus.
• Carbohydrates, proteins and lipids are large biological molecules; carbohydrates are made from sugar units, proteins are made from amino acids, and lipids are made from fatty acids and glycerol.
• Benedict's solution tests for reducing sugars and gives a brick-red precipitate when heated if the result is positive.
• Iodine solution tests for starch and turns from orange-brown to blue-black if the result is positive.
• Biuret reagent tests for protein and turns from blue to lilac or purple if the result is positive.
• The ethanol emulsion test detects lipids and gives a cloudy white emulsion if the result is positive.
• A catalyst is a substance that increases the rate of a chemical reaction without being used up, and enzymes are biological catalysts made of protein.
• An enzyme has an active site with a specific shape, so only a complementary substrate can bind to it and form an enzyme-substrate complex.
• Enzymes digest large insoluble food molecules into smaller soluble molecules so they can be absorbed through the wall of the small intestine into the blood.
• Increasing temperature increases enzyme activity up to the optimum temperature, but temperatures above the optimum denature the enzyme by changing the shape of its active site.
• Each enzyme has an optimum pH, and pH values too far above or below the optimum can denature the enzyme by changing the shape of its active site.
• Amylase is produced in the salivary glands, pancreas and small intestine and digests starch into sugars.
• Protease is produced in the stomach, pancreas and small intestine and digests proteins into amino acids.
• Lipase is produced in the pancreas and small intestine and digests lipids into fatty acids and glycerol.
• Bile is produced in the liver, stored in the gall bladder and released into the small intestine, where it neutralises stomach acid and emulsifies lipids to increase their surface area for lipase.
• The heart is a double circulatory system because the right side pumps blood to the lungs and the left side pumps blood to the body, which allows high pressure delivery of oxygenated blood to body cells.
• Arteries carry blood away from the heart with thick muscular and elastic walls, veins carry blood towards the heart with valves to prevent backflow, and capillaries have one-cell-thick walls for rapid exchange of substances.

• Label the human digestive system accurately, including the mouth, oesophagus, stomach, liver, gall bladder, pancreas, small intestine, large intestine, rectum and anus.
• Describe the passage of food through the digestive system in the correct order, linking organs to digestion, absorption, water absorption and egestion.
• Carry out food tests safely for starch, reducing sugar, protein and lipid, and identify positive and negative results using the correct colour changes or emulsion result.
• Use the lock-and-key model to explain enzyme action, including substrate binding, enzyme-substrate complex formation, product formation and reuse of the enzyme.
• Interpret enzyme reaction rate data by identifying the optimum temperature or pH and explaining decreases in rate using denaturation of the active site.
• Write simple word equations for digestion, such as starch being digested into sugars, proteins into amino acids, and lipids into fatty acids and glycerol.
• Label the heart and major blood vessels, including the atria, ventricles, valves, aorta, vena cava, pulmonary artery and pulmonary vein.
• Compare treatments for coronary heart disease, faulty valves and heart failure by weighing benefits and risks of options such as statins, stents, valve replacement, biological valves, mechanical valves, heart transplant and artificial hearts.
• Explain gas exchange in the alveoli by linking diffusion of oxygen and carbon dioxide to a large surface area, thin walls, moist surfaces, good blood supply and ventilation.
• Explain transpiration investigations by using a potometer, controlling variables, and predicting how temperature, humidity, air movement and light intensity affect the rate of water loss.