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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, 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 passes through the digestive system in this 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.
• Large insoluble food molecules must be digested into small soluble molecules so they can be absorbed through the small intestine wall into the blood.
• Benedict’s solution tests for reducing sugars and turns from blue to green, yellow, orange or brick-red when heated if reducing sugar is present.
• Iodine solution tests for starch and changes from orange-brown to blue-black if starch is present.
• Biuret reagent tests for protein and changes from blue to lilac or purple if protein is present.
• The Sudan III test or ethanol emulsion test detects lipids; a positive result is a red-stained oil layer with Sudan III or a cloudy white emulsion with ethanol and water.
• A catalyst is a substance that increases the rate of a chemical reaction without being used up or permanently changed.
• An enzyme is a biological catalyst made of protein, with an active site that has a specific shape for binding its substrate.
• Enzymes are specific because only substrates with a complementary shape can bind successfully to the enzyme’s active site.
• Metabolism is the sum of all chemical reactions in a cell or organism, and enzyme-controlled reactions include digestion, respiration and the synthesis of larger molecules.
• Increasing temperature raises enzyme activity up to an optimum temperature, but high temperatures denature the enzyme by changing the shape of the active site.
• Each enzyme has an optimum pH, and pH values far from the optimum can denature the enzyme by changing the shape of the active site.
• Amylase digests starch into sugars, proteases digest proteins into amino acids, and lipases digest 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 to increase the 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 blood to be pumped at high pressure to body tissues after it has been oxygenated.

• Label the digestive system accurately, including the mouth, oesophagus, stomach, liver, gall bladder, pancreas, small intestine, large intestine, rectum and anus.
• Describe the route of food through the digestive system and link each major organ to its role in digestion, absorption or egestion.
• Carry out food tests safely and identify positive results for reducing sugars, starch, proteins and lipids using the correct reagents and colour changes.
• Calculate rate of reaction from data using `rate = change ÷ time`, including choosing suitable units from the information given.
• Interpret enzyme graphs by identifying the optimum temperature or pH and explaining changes in rate using active site shape and denaturation.
• Write simple word equations for digestion, such as starch being broken down into sugars, protein into amino acids, and lipids into fatty acids and glycerol.
• Label the heart accurately, including the atria, ventricles, valves, aorta, vena cava, pulmonary artery and pulmonary vein.
• Compare arteries, veins and capillaries by linking their structure to function, including wall thickness, lumen size, valves and diffusion distance.
• Evaluate treatments for cardiovascular disease by weighing benefits and risks of options such as stents, statins, bypass surgery, valve replacement, transplants and artificial hearts.
• Plan or interpret a transpiration investigation using a potometer, controlling variables and explaining how temperature, humidity, air movement and light intensity affect water loss.