Biology 2 - Organisation

• Put these smallest to largest - cells, organisms, organ systems, organs, tissues?

  Cells, tissues, organs, organ systems, organisms
• What is a tissue?


  A group of similar cells working together to carry out a particular function
• Examples of tissues


  Muscular tissue

  Glandular tissue

  Epithelial tissue
• What does muscular tissue do?

  Contracts (shortens) to move whatever it’s attached to
• What does glandular tissue do?

  Makes and secretes enzymes and hormones
• What does epithelial tissue do?

  Covers some parts of the body
• Example of part of the body epithelial tissue covers

  Inside of gut
• What is an organ? 


  A group of different tissues that work together to perform a certain function
• Example of organ


  Stomach
• What tissues is the stomach made of?

  Muscular tissue

  Glandular tissue

  Epithelial tissue
• What does muscular tissue do?

  Moves stomach wall to churn up food
• What does glandular tissue do? 


  Makes digestive juices to digest food
• What does epithelial tissue do?

  Covers outside and inside of stomach
• What is an organ system?

  A group of organs working together to perform a particular function
• Example of organ system


  Digestive system
• What does the digestive system do?

  Breaks down and absorbs food
• What organs does the digestive system contain?

  Glands (pancreas, salivary glands)

  Stomach

  Small intestine

  Liver

  Large intestine
• What do the glands (pancreas and salivary glands) do in the digestive system?


  Produce digestive juices
• What do the stomach and small intestine both do in the digestive system?

  Digest food
• What does the liver do in the digestive system?

  Produces bile
• What does the small intestine also do in the digestive system? 


  Absorbs soluble food molecules
• What does the large intestine do in the digestive system?

  Absorbs water from undigested food, leaving faeces
• What are the two main ways to quicken the rate of reaction?

  Raise temperature

  Enzymes
• What is the problem with raising the temperature?

  Useful reactions would happen more quickly however so would unwanted ones too

  Limit to how much you can raise the temperature until cells become damaged
• What is a catalyst? 


  A substance which increases the speed of a reaction without being changed or used up in the reaction
• What is an enzyme made of?

  Enzymes are large proteins made up of chains of amino acids. They are folded into unique shapes which are important to the enzymes job
• Lock and key model of enzyme action

  Every enzyme has an active site with a unique shape that fits onto the substance involved in a reaction. The substrate fits to the active site to catalyse the reaction.
• What variables effect the rate of reaction?

  Temperature

  pH
• How can a high temperature affect the rate of reaction? 


  Increases the rate at first

  When it gets too hot, some bonds holding enzyme together break

  Changes shape of active site so substrate won’t fit any more

  Enzyme is denatured
• What is an optimum temperature?

  The temperature an enzyme works best at
• How does pH affect the enzymes? 


  Too high or too low interferes with bonds

  Changes shape of active site and denatures enzyme
• What is the optimum pH?

  pH the enzyme works best at
• What is the most common optimum pH for enzymes?

  Neutral - pH 7
• Example of enzyme that does not work best at pH 7

  Pepsin - optimum = pH 2
• What is pepsin used for and why does it work well there?

  Breaks down proteins in the stomach

  Well suited to acidic conditions
• What does amylase catalyse?

  Breakdown of starch to maltose
• How do you detect starch using iodine solution? 


  If starch is present iodine solution will change from browny-orange to blue-black
• How to investigate effect of pH on enzyme activity


  1. Put a drop of iodine solution in every well of a spotting tile

  2. Bunsen burner on heat proof mat

  3. Tripod and gauze over Bunsen burner

  4. Beaker of water on tripod

  5. Heat to 35 degrees Celsius using thermometer to keep constant

  6. Use syringe - add 1cm^3 of amylase solution and buffer solution with pH 5 to boiling tube

  7. Use different syringe - add 5cm^3 of starch solution to boiling tube

  8. Immediately mix contents and start stop clock

  9. Continuous sampling to record how long it takes for amylase to break down starch

  10. Use dropping pipette to take fresh sample from boiling tube every 30 seconds and drop into well

  11. When iodine remains brown-orange starch is not present

  12. Repeat with buffer solutions of different pH values to see effect of pH for starch to break down
• Control variables = concentration and volume of amylase solution
• Rate of reaction equation

  Rate of reaction = 1000/time