Cell organisation and enzymes

• Cell - a basic building block that all living organisms have + there's different types of specialised cells eg : epithelial cell , muscle cells , glandular cells
• Tissues - a group of similar cells that work together to carry out a particular function

  eg : - lots of epithelial cells -> epithelial tissue which covers bodies surface

  - lots of muscle cells -> muscle tissue which contracts and relaxes

  - lots of glandular cells -> glandular tissue which makes and secretes chemicals
• Organ - a group of different tissues that work together to perform a particular function

  eg: epithelial, muscle and glandular tissues = stomach
• Organ systems - a group of organs that work together to perform a particular function

  eg : pancreas , stomach , liver ect = digestive system

  eg : heart and blood vessels ect = cardiovascular system
• Organism - multiple organ systems working together to form an organism
• Cells -> tissues -> organs -> organ systems -> organism
• Enzymes -

  • type of catalyst ( biological)
  • made by living organisms
  • make from large proteins ( made up of long chains of amino acids )
  • can fold up to make different shapes - unique enzyme
  • only catalyses one specific reaction because of The unique shape of its active site
• How enzymes work

  • speeds up the reaction of the reactant ( substrate ) getting broken up into smaller pieces ( product )
  • active site is complementary to the substrate
  • enzyme and substrate fit together like a lock and key
  • if substrate doesn't fit active site the reaction won't be catalysted
• Two models for enzyme action

  Lock and key model ( original )

  • scientists thought substrates had to fit perfectly into active site Induced fit model ( more realistic )
  • enzyme changes shape slightly as it binds to substrate
• High temp can affect enzyme action

  • it starts to break apart bonds holding enzymes together
  • changes shape enough = enzyme won't be able to bind to substrate
  • enzyme is denatured
  • 45 degrees + = is permanent and can't start working again
• Optimum temp of enzymes - temp where enzyme activity is highest = 37 degrees
• pH can also affect enzyme activity

  • some bonds holding enzymes together start to break
  • active site starts to change shape ( substrate can fit but less well ) - slows down rate of reaction but doesn't stop it completely
  • active site changes so much that substrate can't fit = denatured
• Optimum pH- depends where enzyme normally works

  • most neutral ( 7 ) / 8
  • in stomach - 2 - acidic environment
• Digestive enzymes break big molecules down into smaller , soluble ones which can pass through the walls of the digestive system and be absorbed into the blood
• The enzyme amylase ( a carbohydrase ) breaks down starch ( a carbohydrate) into maltose and other sugars produced in the salivary glands , small intestine and pancreas
• The enzyme protease breaks down protein into amino acids produced in the stomach , small intestine and pancreas
• The enzyme lipase breaks down lipid Into glycerol and fatty acids produced in the small intestine and pancreas
• The products of digestion can be used to make new carbohydrates, proteins and lipids
• Bile is made in the liver and stored in the gallbladder
• Bile speeds up digestion in 2 ways :

  • It makes conditions alkaline so enzymes in the small intestine work better
  • It emulsifies fat so there's a larger surface area for lipase to work on