Biology Chapter 2

• 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, substances that increase the rate of reaction without being used up
• Enzyme catalysis


  1. Substrate binding

  2. Transition state facilitation

  3. Catalysis

  4. Release
• Lock and key hypothesis

  The shape of the substrate is complementary to the shape of the active site, so when they bond it forms an enzyme-substrate complex. Once bound, the reaction takes place and the products are released from the surface of the enzyme.
• Optimum pH and temperature for enzymes

  Optimum temperature is around 37 degrees celsius (body temperature). Optimum pH for most enzymes is 7, but some have a low optimum pH.
• If the pH or temperature is too high or too low, the enzyme will be denatured and can no longer work
• Types of enzymes


  • Carbohydrases
  • Proteases
  • Lipases
• Carbohydrases


  Convert carbohydrates into simple sugars
• Proteases


  Convert proteins into amino acids
• Lipases


  Convert lipids into fatty acids and glycerol
• Tests for different molecules

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


  Produced in the liver and stored in the gallbladder, then released into the small intestine. It is alkaline to neutralise stomach acid and emulsifies fats.
• Investigating the effect of pH on an 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. Record time for complete breakdown of starch

  5. Calculate rate using 1000/time
• Heart


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


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


  Two circuits - deoxygenated blood flows to the lungs, oxygenated blood flows around the body
• Parts of the heart

  • Right atrium
  • Right ventricle
  • Left atrium
  • Left ventricle
  • Muscular walls
  • Valves
  • Coronary arteries
• Blood flow through the heart

  1. Blood flows into right atrium and right ventricle, then to lungs

  2. Blood flows into left atrium and left ventricle, then around body

  3. Valves ensure one-way flow
• Pacemaker


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


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

  • Arteries
  • Veins
  • Capillaries
• Arteries


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


  Carry blood towards the heart, have a wide lumen and valves to ensure one-way flow
• Capillaries


  Allow blood to flow very close to cells to enable substances to move between them, have one cell thick permeable walls
• Lungs


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

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


  Ribcage moves up and out, diaphragm moves down, increasing volume and decreasing pressure, drawing air into the lungs
• Gas exchange


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


  Adapted for gas exchange with large surface area, thin walls, and good blood supply
• Components of blood


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


  Liquid that carries the other blood components and various substances
• Red blood cells


  Carry oxygen from the lungs to cells, have a biconcave disc shape and contain haemoglobin
• White blood cells


  Part of the immune system, defend the body against pathogens