b2 - organisation

• cells - basic building blocks of living organisms
• each cell has a specific function
• organs are a group of tissues which work together to perform a specific function - make up an organ
• main blood vessels of the heart : pulmonary vein, pulmonary artery, aorta, vena cava and the coronary arteries
• pacemaker : controls resting heart rate
• blood vessels : arteries, veins and capillaries
• main components of blood : plasma, white blood cells, red blood cells, platelets
• the digestive systems function is to break down and absorb food
• enzymes are biological catalysts and work best at optimum temperature and pH
• enzymes: carbohydrase (amylase), protease, lipase
• risk factors to health and disease include : diet, exercise, drugs, alcohol consumption, environment and stress
• communicable diseases : pathogens- viral/bacterial
• non-communicable diseases are diseases which cannot be spread, for example heart disease or cancer
• the xylem transports water via transpiration. It is dead, hollow cells strengthened with lignin
• the phloem is made from elongated living cells and transports sugars via translocation
• substances move up the stem via the xylem and phloem to the leaves
• spongy mesophyll - facilitate diffusion of gases, loosely packed cells
• lower epidermis of the leaf contains stomata
• stomata and guard cells control the rate of gas exchange and transpiration
• stomata enables water loss from leaves in transpiration
• the rate of evaporation is controlled by stomata and guard cells
• enzymes are catalysts
• carbohydrase changes starch into sugars
• isomerase changes glucose syrup into fructose syrup
• protease pre-digests proteins in some baby foods
• starch = amylase
• fat = lipase
• fat is broken down into fatty acids and glycerol
• protein is broken down into amino acids
• bile is produced in the liver
• the stomach produces hydrochloric acid
• how increasing temperature causes enzymes to denature:

  High temperatures start to break the bonds holding the enzyme together 

  This causes the enzyme and it's active site to change shape

  This means the enzymes active site will no longer be complementary to the substrate 
• rate on transpiration increases when light intensity is increased because the stomata open wider to let more carbon dioxide into the leaf for photosynthesis
• Heart ➔artery ➔capillaries ➔veins ➔ heart
• antibodies bind to pathogens and help immune cells destroy them
• cells ➔ tissues ➔organs ➔ organ systems
• structure and function of capillaries:

  1. Capillaries are the smallest of the three blood vessels.
  2. The role of capillaries is to exchange nutrients and waste products with the tissues.
  3. Capillary walls are permeable, meaning substances are able to move through them.
  4. Their walls are also only one cell thick which means a short distance for diffusion.
  5. Capillaries carry blood at a low pressure and have a lower rate of flow than arteries.
• the pancreas produces amylases, proteases and lipases
• water passes up the plant via the xylem
• pulmonary artery carries deoxygenated blood from the heart to the lungs