Biology topic 2 organisation

• 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 working together to perform a certain function
• Organ system example


  • Digestive system
• Organs in the digestive system

  • Glands (salivary glands and 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
• Optimum pH and temperature for enzymes

  • Optimum temperature is around 37 degrees celsius (body temperature)
  • Optimum pH for most enzymes is 7, some 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 (convert carbohydrates into simple sugars)
  • Proteases (convert proteins into amino acids)
  • Lipases (convert lipids into fatty acids and glycerol)
• 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
  • Alkaline to neutralise hydrochloric acid
  • 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. Warm a solution of amylase, starch and buffer

  2. Take drops at regular intervals and test with iodine

  3. Time when starch is completely broken down

  4. Calculate rate using 1000/time
• Circulatory system


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


  Two circuits - deoxygenated blood to lungs, oxygenated blood around 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 atria

  2. Atria contract, forcing blood into ventricles

  3. Ventricles contract, pushing blood to lungs and body

  4. Valves close to prevent backflow
• Pacemaker


  Group of cells in right atrium that provide electrical stimulation to make the heart beat
• 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 heart)
  • Veins (carry blood towards heart)
  • Capillaries (allow blood to flow close to cells)
• Arteries


  • Layers of muscle and elastic fibres to withstand high pressure
• Veins


  • Wide lumen to allow low pressure blood flow, valves to ensure one-way flow
• Capillaries


  • One cell thick walls, permeable to allow substances to move between blood and cells
• The lungs are found in the thorax and are protected by the ribcage
• Parts of the gas exchange system

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


  1. Ribcage moves up and out, diaphragm moves down, increasing volume and decreasing pressure, drawing air in

  2. Opposite happens when exhaling
• Gas exchange in alveoli

  1. Oxygen diffuses from alveoli into blood

  2. Carbon dioxide diffuses from blood into alveoli
• Alveoli


  • Very small and arranged in clusters, creating large surface area
  • Capillaries provide large blood supply
  • Thin walls for short diffusion pathway
• 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 room for haemoglobin
  • Contain haemoglobin to bind oxygen
• White blood cells


  Part of the immune system, defend against pathogens
• There are different types of white blood cells that produce antibodies, engulf pathogens, and coordinate the immune response
• Alveoli


  Very thin, meaning there is a short diffusion pathway
• Calculating breathing rate


  Divide the number of breaths by the number of minutes