biology igcse

• diffusion as the net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient
• substances move into and out of cells by diffusion through the cell membrane
• water diffuses through partially permeable membranes by osmosis
• net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane
• higher temperature increases osmosis rate
• Carbohydrates are composed of carbon, hydrogen, and oxygen
• Lipids are composed of carbon, hydrogen and oxygen atoms, and in some cases contain phosphorus, nitrogen, sulfur
• Proteins contain the elements carbon, hydrogen, and oxygen
• State that large molecules are made from smaller molecules, limited to: – starch and glycogen from glucose – proteins from amino acids – fats and oils from fatty acids and glycerol
• water is important as a solvent
• iodine solution can test for starch if starch is tested colour is changes to black/brown
• Benedict's solution can be tested for reducing sugar if solution changes to green
• Biuret test can change to purple if there is protein present.
• ethanol emulsion test can determine if sample has fats if there is thick substance made
• enzymes as proteins that function as biological catalysts
• photosynthesis as the process by which plants manufacture carbohydrates from raw materials using energy from light
• Plant cells have a cell wall in addition to a cell membrane, whereas animal cells have only a cell membrane. 
• Plants cells have chloroplasts, cell wall and a large vacuole
• State the word equation for photosynthesis: carbon dioxide + water → glucose + oxygen, in the presence of light and chlorophyll
•  At very high light intensities, photosynthesis is slowed,
• xylem for transport and support
• phloem for transport
• stomata, spongy mesophyll cells and guard cells – gas exchange
• Nitrate deficiency cause plants to turn yellow
• Potassium deficiency causes leaves to curl upwards
• Magnesium deficiency causes plants to stunt growth
• ingestion as the taking of substances, e.g. food and drink, into the body through the mouth
• digestion as the breakdown of large, insoluble food molecules into small, watersoluble molecules using mechanical and chemical processes
• absorption as the movement of small food molecules and ions through the wall of the intestine into the blood
• mechanical digestion as the breakdown of food into smaller pieces without chemical change to the food molecules
• chemical digestion as the breakdown of large, insoluble molecules into small, soluble molecules
• egestion as the passing out of food that has not been digested or absorbed, as faeces, through the anus
• amylase breaks down starch to simpler sugars
• protease breaks down protein to amino acids
• lipase breaks down fats to fatty acids and glycerol
• carbohydrates are found in pancreas, salivary glands and small intestine
• protein is found in stomach, pancreas and small intestine
• fats are found in pancreas and small intestine
• mouth breaks down food mechanically with saliva
• stomach contracts its walls to mix food with stomach acid (pepsin and hydrochloric acid)