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neurologyYou need to know

• A tissue is a group of similar cells working together to carry out a particular function, such as muscle tissue contracting or glandular tissue secreting enzymes.
• An organ is a group of different tissues working together to carry out a particular function, such as the stomach digesting food using muscular tissue, glandular tissue and epithelial tissue.
• Food passes through the digestive system in the order mouth, oesophagus, stomach, small intestine, large intestine, rectum and anus.
• Carbohydrates are made from sugar molecules, proteins are made from amino acids, and lipids are made from fatty acids and glycerol.
• Benedict’s test detects reducing sugars by changing from blue to green, yellow, orange or brick-red after heating, and iodine solution detects starch by changing from orange-brown to blue-black.
• Biuret reagent detects protein by changing from blue to lilac or purple, and the ethanol emulsion test detects lipids by forming a cloudy white emulsion.
• A catalyst is a substance that increases the rate of a chemical reaction without being used up, and enzymes are biological catalysts made of proteins.
• An enzyme has an active site with a specific shape that is complementary to its substrate, so only certain substrates can bind to it.
• Enzymes catalyse reactions when the substrate binds to the active site to form an enzyme-substrate complex, allowing products to form and leave the enzyme unchanged.
• Metabolism is the sum of all chemical reactions in cells, including the synthesis of large molecules from smaller ones and the breakdown of large molecules into smaller ones.
• High temperatures and unsuitable pH values can denature enzymes by changing the shape of the active site, which reduces or stops enzyme activity.
• Amylase breaks starch into sugars, proteases break proteins into amino acids, and lipases break lipids into fatty acids and glycerol.
• Amylase is produced in the salivary glands, pancreas and small intestine; proteases are produced in the stomach, pancreas and small intestine; and lipases are produced in the pancreas and small intestine.
• Bile is made in the liver, stored in the gall bladder and released into the small intestine, where it neutralises stomach acid and emulsifies lipids into small droplets.
• The heart is a double circulatory system because blood travels from the heart to the lungs and back, then from the heart to the body and back, which allows oxygenated blood to be pumped to the body at high pressure.
• Arteries carry blood away from the heart and have thick muscular elastic walls, veins carry blood back to the heart and have valves to prevent backflow, and capillaries have one-cell-thick walls for rapid exchange.
• Blood is made of plasma, red blood cells, white blood cells and platelets; plasma transports dissolved substances, red blood cells carry oxygen, white blood cells defend against pathogens, and platelets help blood clot.
• Coronary heart disease is caused by fatty material building up in the coronary arteries, reducing blood flow to heart muscle, and it can be treated using statins, stents or coronary bypass surgery.
• Alveoli are adapted for gas exchange by having a large surface area, moist surfaces, one-cell-thick walls, a rich capillary supply and ventilation that maintains steep diffusion gradients.
• Xylem transports water and mineral ions and has hollow lignified tubes, phloem transports dissolved sugars, root hair cells absorb water and mineral ions with a large surface area, and transpiration increases with higher temperature, higher light intensity and more air movement but decreases with higher humidity.

• Label the main organs of the human digestive system, including the mouth, oesophagus, stomach, small intestine, large intestine, rectum, anus, liver, gall bladder and pancreas.
• Describe the passage of food through the digestive system, linking each region to its main role in mechanical digestion, chemical digestion, absorption or egestion.
• Carry out and interpret food tests for reducing sugars, starch, protein and lipids using the correct reagents and positive colour changes.
• Calculate rate of reaction from data using `\text{rate}=\frac{\text{change}}{\text{time}}`, giving appropriate units.
• Explain enzyme activity using the active site model, including substrate specificity, optimum temperature, optimum pH and denaturation.
• Label the chambers, valves and major blood vessels of the heart, including the atria, ventricles, vena cava, pulmonary artery, pulmonary vein and aorta.
• Trace the route of blood through the double circulatory system, distinguishing oxygenated blood from deoxygenated blood.
• Compare treatments for cardiovascular problems, such as statins, stents, bypass surgery, mechanical valves, biological valves, heart transplants and artificial hearts, using benefits and risks.
• Explain gas exchange in the alveoli using diffusion gradients, short diffusion distance, large surface area and blood supply.
• Investigate the effect of a factor on transpiration rate using a potometer, controlling variables and using bubble movement or water uptake to estimate rate.