organisation

• A tissue is a group of cells with a similar structure and function.
• organs are groups of tissues that work together to perform a specific function
• organ system is a system of organs that work together to perform a specific function
• organells-cells-tissues-organs-organ systems-organism
• enzyme is a substance that increases the speed of a reaction without being changed or used up
• enzymes are biological catalyst and large proteins
• how do enzymes work?

  they are complementary to the substrate. if t doesnt fit wont be catalysed
• what affects enzyme action?

  Temperature, pH,
• how does temperature affect enzyme action?

  high temperatures can cause the active site to become denatured so the enzyme won't be able to bind to the substrate.
• how does pH affect enzyme activity?

  pH affects the shape of the active site
• how does pH affect enzyme action?

  cause the active site to become denatured
• amylase: a carbohydrase which breaks down starch

  • break down carbohydrates
  • are made in salivary gland, pancreas and small intestines
• protease:

  • break down proteins into amino acids
  • are made in the stomach, pancreas and small intestine
• lipases:

  • break down fats into fatty acids or glycerol
  • made in the pancreas and small intestine
• Digestive enzymes convert food into small soluble molecules that can be absorbed into the bloodstream.
• Carbohydrases break down carbohydrates into simple sugars.
• The products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration.
• bile:

  • made in the liver
  • stored in the gall blader
  • It is alkaline to neutralise hydrochloric acid from the stomach
  • emulsifies fat to form small droplets which increase the surface area
  • alkaline conditions and large surface area increase the rate of fat breakdown by lipase
• how is the small intestine adapted to its function?

  villi-increases surface area for digestion so gets absorbed faster

  single layer of surface cells so doesn't have to diffuse a lot.

  lots of blood supply
• we breathe in air and then it goes into the lungs through the trachea, down to the bronchi and into the bronchioles
• alveoli: site of gas exchange
• Adaptations of alveoli for their function:

  • One cell thick: creates a short diffusion pathway, increasing the rate at which CO2 and oxygen can diffuse across
  • Large surface area: many alveoli are present in the lungs with a shape that further increases surface area
  • Moist walls: gases dissolve in the moisture, aiding their passage across the gas exchange surface
  • Good blood supply: ensures oxygenated blood is taken away from the lungs and carbon dioxide-rich blood is taken to the lungs
  • Large diffusion gradient: breathing maintains a higher oxygen concentration in the alveoli than in the capillaries, facilitating the movement of oxygen from the alveoli to the blood and carbon dioxide in the opposite direction
• The heart is an organ that pumps blood around the body in a double circulatory system.
• The right ventricle pumps blood to the lungs where gas exchange takes place.
• The left ventricle pumps blood around the rest of the body.
• The natural resting heart rate is controlled by a group of cells located in the right atrium that act as a pacemaker.
• Artificial pacemakers are electrical devices used to correct irregularities in the heart rate.
• arteries: carry blood away from the heart at high pressures

  • thick layer of muscles and elastic tissue
  • for high pressures of blood
  • thick walls and narrow lumen
• capillaries: exchange of nutrients and oxygen between blood and tissues

  • really small
  • exchange substances with cells
  • takes waste products away
  • single cell thick and permeable for diffusion
  • tiny lumen
  • lower blood pressure
• vein: carries blood back to the heart

  • big and wide lumen
  • small layers of elastic fibres and smooth muscle
  • low pressure
  • valves which prevent backflow of blood
• arteries vs vein

  -arteries:

  • carry oxygenated blood except for the pulmonary artery
  • high pressure
  • thick muscular walls to pump blood around the body
  • no valves

  -veins:

  • carry deoxygenated blood except the pulmonary vein
  • low pressure
  • thin walls has less muscular tissue
  • has valves
• rate of blood = volume of blood / time taken to flow through the heart
• Blood is a tissue consisting of plasma, in which the red blood cells, white blood cells and platelets are suspended.
• red blood cells: carry oxygen from the lungs to the body cells and back
• platelets: to help blood clot at the site of a wound
• what is the function of platelets?

  -carries waste products

  -carries soluble products of digestion and absorption

  -carries hormones and antibodies
• function of white blood cells: to fight infection, defend against pathogens, and produce antibodies
• white blood cells:

  • phagocytosis - engulf pathogens
  • antibodies - bind onto pathogens and help destroy them
  • antitoxins - neutralise any toxins
  • has a nucles
• In coronary heart disease layers of fatty material build up inside the coronary arteries:

  • reduces the flow of blood
  • reducing the amount of oxygen for the heart muscle
• Stents are used to keep the coronary arteries open.