organisation

• a tissue is a group of cells with similar structure and function, which all work together, eg muscle tissue
• an organ is a group of tissues which work together to perform a specific job, eg stomach
• organ systems are groups of organs working together, such as the digestive system
• the salivary glands produce amylase
• the oesophagus carries food from mouth to stomach
• the stomach releases digestive enzymes such as pepsin, lipase and protease
• the liver produces bile for lipid digestion
• the small intestine digests food and absorbs nutrients
• the large intestine absorbs water from digested food
• the pancreas releases amylase, protease, and lipase
• the gall bladder stores bile before releasing it to the small intestine
• carbohydrates are made up of simple sugars. complex carbohydrates are starch, cellulose and glycogen. they are broken down by amylase into glucose (used as an energy source in respiration).
• test for starch - add iodine solution and it will turn blue-black
• lipids are used for energy stores and make up the cell membrane. they are broken down by lipase into (3) fatty acids and (1) glycerol.
• test for lipids - (emulsion test) add ethanol and water and it will turn cloudy white
• proteins are made of amino acids and are broken down into amino acids. they are important for making antibodies, enzymes and hormones.
• test for protein - add biuret solution, and it will turn purple
• sugars are broken down by sucrose into glucose and fructose
• test for sugars - add benedict's solution and boil in a water bath, it will turn brick red
• enzymes are biological catalysts. each enzyme catalyses a specific reaction. they work best at a specific temperature and pH, called the optimum. high temperatures and extreme pH levels cause enzymes to denature.
• how do enzymes work?

  A) enzyme

  B) active site

  C) substrate

  D) combined - reaction takes place

  E) substrate is broken down, enzyme can be reused

  F) products

  
• the blood is made of plasma which has 3 components suspended in it:

  1. red blood cells
  2. white blood cells
  3. platelets
• red blood cells have no nucleus so can carry a lot of haemoglobin. they are very small so can fit through capilliaries. they have a biconcave disc shape so have a higher surface area for oxygen.
• white blood cells protect the body against infection. they can change shape so can squeeze out of blood vessels, into tissues. they can also surround and engulf microorganisms.
• platelets are fragments of cells which collect at wounds and trigger blood clotting
• struc

  A) pulmonary artery

  B) aorta

  C) pulmonary vein

  D) vena cava

  E) right atrium

  F) right ventricle

  G) left ventricle

  H) semilunar valve

  I) semilunar valve

  J) atrioventricular valve

  K) left atrium

  
• structure of a leaf

  A) air space

  B) waxy cuticle

  C) upper epidermis

  D) mesophyll

  E) lower epidermis

  F) stoma

  G) waxy cuticle

  H) guard cell

  I) spongy mesophyll

  J) palisade mesophyll

  
• transpiration is the loss of water from leaves through evaporation. it is affected by temperature, air flow, light intensity and humidity. the water leaves through the stomate which are opened and closed by guard cells
• the pancreas makes pancreatic juice, containing the digestive enzymes amylase, lipase, and protease (trypsin), in an alkali solution of sodium hydrocarbonate to neutralise the acidic chyme coming into the stomach.
• two types of protease - pepsin (pH2, found in stomach) and trypsin (pH 8, found in the small intestine)