B2 - Organisation

• Levels of organisation in multicellular organisms (in order of increasing complexity)


  • Cells
  • Tissues
  • 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 structure
• Organ


  A structure made up of groups of different tissues, working together to perform specific functions
• Organ system


  A group of organs with related functions, working together to perform certain functions within the body
• Examples of tissues in mammals (like humans)


  • Muscular tissue
  • Glandular tissue
  • Epithelial tissue
• Muscular tissue


  Contracts (shortens) to move whatever it is attached to
• Glandular tissue


  Makes and secretes chemicals like enzymes and hormones
• Epithelial tissue


  Covers some parts of the body, e.g. the inside of the gut
• Label these parts

  Fill these in

  A) nucleus

  B) heart muscle cells

  C) heart muscle

  D) heart

  E) circulatory system

  F) organelle

  G) cell

  H) tissue

  I) organ

  J) organ system

  
• Cells


  Make up all living things
• Organs in the digestive system


  • Glands (salivary glands, pancreas)
  • Stomach
  • Small intestine
  • Liver
  • Gall bladder
  • Large intestine
  • Rectum
  • Anus
• Enzymes


  Biological catalysts, substances that increase the rate of reaction without being used up
• How enzymes work (Lock and Key Hypothesis)


  1. Substrate binds to active site of enzyme

  2. Reaction takes place

  3. Products released
• Enzymes


  • They can both break up large molecules and join small ones
  • They are protein molecules and the shape of the enzyme is vital to its function
• Active site


  Uniquely shaped site where the substrate binds
• Optimum pH and temperature for enzymes


  • Optimum temperature is around 37 degrees Celsius (body temperature)
  • Optimum pH is 7, but some enzymes have a low optimum pH
• When the temperature becomes too hot, the bonds in the structure will break, changing the shape of the active site so the substrate can no longer fit in. The enzyme is said to be denatured and can no longer work
• If the pH is too high or too low, the forces that hold the amino acid chains that make up the protein will be affected, changing the shape of the active site so the substrate can no longer fit in. The enzyme is said to be denatured and can no longer work
• Types of enzymes

  • Carbohydrases (convert carbohydrates into simple sugars)
  • Proteases (convert proteins into amino acids)
  • Lipases (convert lipids into fatty acids and glycerol)
• Carbohydrase example


  • Amylase breaks down starch into maltose
• Protease example


  • Pepsin produced in the stomach
• Soluble glucose, amino acids, fatty acids and glycerol pass into the bloodstream to be carried to all the cells around the body
• Tests for different molecules

  • Benedict's test for sugars (turns brick red)
  • Iodine test for starch (turns blue-black)
  • Biuret test for protein (turns purple)
  • Emulsion test for lipids (add ethanol which results in a cloudy layer if a lipid is present)
  • Sudan III test for lipids (red layer forms on top)
• Bile


  Produced in the liver and stored in the gallbladder, then released into the small intestine. It is alkaline to neutralise the hydrochloric acid from the stomach, and it emulsifies large drops of fat into smaller ones to allow lipase to break them down faster
• Investigating the effect of pH on an enzyme controlled reaction

  1. Use iodine which turns blue-black in the presence of starch

  2. Warm a solution of amylase, starch and a buffer solution

  3. Take drops of the solution at regular points and place in wells with iodine

  4. The time for the starch to be completely broken down is recorded and the rate is calculated
• Circulatory system

  Carries oxygen and nutrients to every cell in the body and removes the waste products
• Double circulatory system

  There are two circuits - deoxygenated blood flows to the lungs, then oxygenated blood flows around the body
• Parts of the heart

  • Right atrium
  • Right ventricle
  • Left atrium
  • Left ventricle
  • Muscular walls
  • Valves
  • Coronary arteries
• How the heart pumps blood

  1. Blood flows into the right atrium and left atrium

  2. The atria contract forcing the blood into the ventricles

  3. The ventricles then contract, pushing the blood to the lungs and around the body

  4. Valves close to prevent backflow
• Pacemaker


  Group of cells in the right atrium that provide electrical stimulation to make the heart contract
• Artificial pacemaker

  Electrical device that produces a signal causing the heart to beat at a normal speed
• Types of blood vessels

  • Arteries (carry blood away from the heart)
  • Veins (carry blood towards the heart)
  • Capillaries (allow blood to flow close to cells for diffusion)
• Arteries


  • Layers of muscle in the walls make them strong
  • Elastic fibres allow them to stretch to withstand the high pressure from the heart
• Veins

  • Wide lumen to allow low pressure blood to flow
  • Valves to ensure blood flows in the right direction
• Capillaries


  • One cell thick walls create a short diffusion pathway
  • Permeable walls to allow substances to move between blood and cells
• The rate of blood flow is calculated from volume of blood/number of minutes
• Parts of the gas exchange system

  • Trachea
  • Intercostal muscles
  • Bronchi
  • Bronchioles
  • Alveoli
  • Diaphragm
• Ventilation

  1. Ribcage moves up and out, diaphragm moves down to increase volume and decrease pressure, causing air to be drawn in

  2. The opposite happens when exhaling