Organisation

• In order of increasing complexity, multicellular organisms are made of:

  • Cells
  • Tissue
  • Organs
  • Organ systems
• Organelle: A specialised unit within a cell which performs a specific function
• Cell: The basic building block of all living organisms
• Tissue: A group of cells working together to perform a shared function, and often with similar structures
• Organ: A structure made up of groups of different tissues, working together to perform specific functions
• Organ system: A group of organs with relative function, working together to perform certain functions within the body
• Organelle - Nucleus

  Cell - Heart muscle cell

  Tissue - Heart muscle

  Organ - Heart

  System - Circulatory system
• The human digestive system has two functions:

  • breaks down complex food substances
  • provides the very large surface area for maximum absorption of food
• Human digestive system:

  
• Mouth: Begins the digestion of carbohydrates
• Stomach: Begins the digestion of protein; small molecules such as alcohol absorbed
• Small intestine (Duodenum)- Continues the digestion of carbohydrates and proteins; begins the digestions of lipids
• Small intestine (ileum) - Completes the digestion of carbohydrates and proteins into single sugars and ammino acids; absorption of single sugars, ammino acids and fatty acids and glycerol
• Large intestine - Absorption of water; egestion of undigested food
• Digestive enzymes are used to break down food in the gut into small, soluble molecules that can be absorbed through the gut wall.
• The surface of the small intestine wall is folded, and has projections called villi.
• Food Tests:

  • Sugars = Benedict's solution
  • Starch = Iodine
  • Protein = Biuret solution
  • Lipids = Ethanol
• Sugar food test:

  1. Add benedict's solution to food
  2. Heat in a water bath

  Result = Changes colour when heated - Red/brown colour if glucose is present

  If there's not much glucose present, the final colour may be green or yellow, or orange if there's a little mor
• Starch food test:

  1. Add iodine to the food your are testing

  Turns a blueish black colour

  The iodine test can also be used with a microscope to stain starch grains in plant cells
• Proteins food test:

  1. Add biuret solution to the food you are testing

  Turns purple if protein is present
• Test for Lipids:

  1. Add Ethanol to the food being tested

  Turns cloudy if Lipids are present
• Enzymes: Biological catalysts that speed up chemical reactions in the body.
• Digestive Enzymes:

  • Carbohydrates = Carbohydrase
  • Starch = Amylase
  • Protein = Protease
  • Lipids = Lipase
• Humans have a double circulatory system. The heart pumps blood through two circuits:

  1. the pulmonary circulation
  2. the systemic circulation
• The pulmonary circulation transports blood to the lungs. At the lungs:

  • oxygendiffuses into the blood from the alveoli - the blood becomes oxygenated
  • carbon dioxide diffuses from the blood into the lungs
• The systemic circulation transports:

  • oxygen and nutrients to the body
  • carbon dioxide and other wastes away from cells
• The systemic circulation is under high pressure - it has to deliver blood to the extremities of the body.

  The pulmonary circulation is under lower pressure, because:

  • blood is delivered to the lungs only, which are very close to the heart
  • in a healthy person, this lower pressure is optimum for the diffusion of gases
• Blood is transported in arteries, veins and capillaries.
• Blood is pumped from the heart in the arteries. It is returned to the heart in the veins
• The capillaries connect the two types of blood vessel and molecules are exchanged between the blood and the cells across their walls.
• Arteries:

  • Carry blood away from the heart
  • Carry oxygenated blood, except for the pulmonary artery
  • Carry blood under high pressure
  • Have thick muscular and elastic walls to pump and accommodate blood
  • A type of supporting tissue called connective tissue provides strength
  • The channel in the blood vessel that carries blood - the lumen - is narrow
• Veins:

  • Carries blood to the heart
  • Always carry deoxygenated blood, except for the pulmonary vein
  • Carry blood under low or negative pressure
  • Have thin walls - have less muscular tissue than arteries
  • Have less connective tissue than arteries
  • Have a wide lumen
• Capillaries: Capillaries connect the smallest branches of arteries and veins
• Capillaries:

  • Wall is one cell thick

  
• The Heart:

  A) Aorta

  B) Left Atrium

  C) Pulmonary vein

  D) Pulmonary artery

  E) Right atrium

  F) Heart valve

  G) Right ventricle

  H) Left Ventricle

  I) Heart valve

  J) Vena Cava

  
• Plasma is a straw-coloured liquid that makes up just over half the volume of blood.
• Plasma: Transports carbon dioxide, digested food molecules, urea and hormones; distributing heat
• Red blood cells: Transporting oxygen
• White blood cells: Ingesting pathogens and producing antibodies
• Platelets: Involved in blood clotting