organisation

• organs are made of a variety of tissues
• both plants and animals have tissues and organs
• organ systems are composed of several organs
• plants are multicellular organisms just like animals
• epidermal tissue - covers the plant
• mesophyll tissue - photosynthesis
• xylem consists of dead cells that are hollow and have no chloroplasts
• phloem consists of living cells that transports food molecules from the rest of the plant to the leaves
• tissues are a collection of the same cells
• plant are multicellular organisms just like animals
• the digestive system is made of the mouth, oesophagus, the stomach, the small intestine, the large intestine and the rectum and the anus
• the mouth contains the tongue and teeth which perform mechanical digestion and saliva which contains enzymes
• the oesophagus is the tube which connects the mouth with the stomach
• the stomach churns food with enzymes and hydrochloric acid
• the small intestine is where small molecules are digested and absorbed into the blood
• the large intestine is where water is absorbed leaving solid waste
• the rectum is where the waste is stored
• the anus is where the faeces passes out of the body
• the liver releases bile into the small intestine where it helps to digest food
• the pancreas releases digestive juices containing enzymes to help break down food
• enzymes are biological catalysts
• enzymes are proteins that are folded into complex shapes that allow smaller molecules to fit into them
• the place where substrate molecules fit into enzymes is called the active site
• changes in ph alter an enzymes shape
• different enzymes work best at different ph levels
• the optimum ph for enzymes depends on where they work
• carbohydrases (enzymes) break down carbohydrates
• most carbohydrates are mainly starch so starch is the substrate that is broken down by enzymes
• amylase is the carbohydrase that breaks down starch
• digestive enzymes are chemicals that break down large insoluble food molecules into smaller soluble molecules
• digestive enzymes are classified by what they digest. carbohydrase - carbohydrates into sugars , protease - proteins into amino acids, lipase - fatty acids into glycerol
• catalysts lower activation energy which speeds up digestive reactions
• the pancreas is part of the digestive system and the endocrine system
• enzymes in the small intestine work best in alkaline conditions but food is acidic after leaving the stomach so bile neutralises it
• before lipase can work lipids need to be emulsified which is done by bile from the liver and stored in the gallbladder
• bile is not an enzyme
• intestinal villi are tiny finger like outgrowths that increase the surface area of the gut to give a greater time for absorption of nutrients
• villi have a great blood supply which has a lower concentration of food so diffusion happens quickly
• iodine tests for starch and turns from orange red to blue black
• Benedict's solution tests for carbohydrates (add a few drops and put in a water bath) it turns from light blue to red (green or yellow if less is present)