organisation

• lock and key theory


  states that the active site must be complemetary to the shape of the substrate molecule
• plasma


  takes nutrients, hormones and proteins to parts of the body that need it
• platelets


  cells which form clots to stop or prevent bleeding
• red blood cells

  carry oxygen from the lungs and deliver it throughout our body
• white blood cells

  immune system cells which protect your body from bacteria and viruses
• features of arteries

  have muscle and elastic tissue and have thick walls to maintain high blood pressure
• features of capillaries

  have thin walls which are a single cell thick and permeable , they help to exchange nutrients
• features of vein

  have thin walls (to maintain low blood pressure )with a small layer of elastic fibres. they also have valves to stop backflow of the blood
• how is coronary heart disease caused?

  the coronary arteries get blocked up by fatty plaques containing cholesterol
• factors which caused CHD

  POOR DIET- eating more fat increases cholesterol levels causinh blockage

  STRESS- increases blood pressure and cholesterol levels

  SMOKING- reduces amount of oxygen your blood can carry
• benign tumors


  only contained in one place and don't invade other areas of the body, but can still grow quickly
• malignant tumors


  cells can spread around the body invadinh healthy tissues and can lodge into another organ and form a secondary tumor
• causes of cancer

  genetics, ionising radiation, viral infections, changes to DNA (mutations)
• function of phloem

  carries sugar from leaves to roots of a plant
• function of xylem

  carries water & dissolves substances from roots to leaves