Organization

• Cells


  Make up all living things
• Tissue


  A group of specialised cells with a similar structure and function, can be made of more than one type of cell
• Tissue examples


  • Muscular tissue
  • Epithelial tissue
• Organ


  Formed from a number of different tissues, working together to produce a specific function
• Organ example


  • Stomach
• Organ system


  Organs organised to work together to perform a certain function
• Organ system example


  • Digestive system
• Organs in the digestive system

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


  Biological catalysts 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
• 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
• As temperature increases


  Rate of reaction increases up to optimum, then rapidly decreases
• If pH or temperature is too high or low


  Enzyme becomes denatured and can no longer work
• Types of enzymes


  • Carbohydrases
  • Proteases
  • Lipases
• Examples of carbohydrases, proteases and lipases

  • Amylase
  • Pepsin
  • Lipases in pancreas and small intestine
• Soluble glucose, amino acids, fatty acids and glycerol pass into the bloodstream
• Tests for different molecules

  • Benedict's test for sugars
  • Iodine test for starch
  • Biuret test for protein
  • Emulsion test or Sudan III test for lipids
• Bile


  • Produced in the liver, stored in the gallbladder, released into the small intestine
  • Alkaline to neutralise stomach acid
  • Emulsifies large fat droplets to increase surface area for lipase
• Investigating effect of pH on enzyme controlled reaction

  1. Use iodine to detect presence of starch

  2. Warm amylase, starch and buffer solution

  3. Take samples at regular intervals and test with iodine

  4. Time when starch is completely broken down

  5. Calculate rate using 1000/time
• Rate of enzymatic reactions


  Rate = change/time
• Heart


  An organ in the circulatory system that pumps blood around the body
• Circulatory system


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


  1. Deoxygenated blood flows to right atrium, right ventricle, lungs

  2. Oxygenated blood flows to left atrium, left ventricle, body
• Structure of the heart

  • Muscular walls
  • 4 chambers
  • Valves
  • Coronary arteries
• Blood flow through the heart

  Blood flows into atria, atria contract to force blood into ventricles, ventricles contract to pump blood out
• Pacemaker


  Group of cells in right atrium that provide electrical stimulation to control heart rate
• Artificial pacemaker


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

  • Arteries
  • Veins
  • Capillaries
• Arteries


  • Carry blood away from the heart
  • Layers of muscle and elastic fibres to withstand high pressure
• Veins


  • Carry blood towards the heart
  • Wide lumen to allow low pressure flow
  • Valves to ensure one-way flow
• Capillaries


  • Allow blood to flow close to cells for diffusion
  • One cell thick walls for short diffusion pathway
  • Permeable walls
• Lungs


  Found in the thorax, supply oxygen to blood and remove carbon dioxide
• Components of the gas exchange system

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


  Ribcage moves up and out, diaphragm moves down to increase volume and decrease pressure, drawing in air
• Gas exchange in alveoli

  Oxygen diffuses from alveoli into blood, carbon dioxide diffuses from blood into alveoli
• Alveoli


  • Small size and clustered arrangement for large surface area
  • Thin walls for short diffusion pathway
  • Large blood supply to maintain concentration gradient
• Blood


  Made up of plasma, red blood cells, white blood cells and platelets
• Components of blood


  • Plasma
  • Red blood cells
  • White blood cells
  • Platelets
• Red blood cells


  • Biconcave disc shape for large surface area
  • No nucleus to allow more space for haemoglobin