Exam

• Lipids

  -Fats and oils - dont dissolve in water as they are hydrophobic
• Where do you get lipids from in your diet

  • Butter
  • Oil
  • Chocolate
  • Cheese
  • Milk
  • Bacon
• What does your body need lipids for

  • Dense form of energy
  • Insulation from environment. (More resistant to temperature)
  • Cell membrane (Phospholipids)
• Lipids are stored in in adiptose tissue
• Roles of adiptose tissue

  • Heat insulation- adiptose tissue under skin helps reduce heat loss
  • Protection- adiptose tissue around delicate organs like kidneys
• Double bond means its unsaturated
• Carbohydrates = sugars and starch

  Used as energy sources and structural material
• A monomer is a single molecule
• A polymer is a chain of monomers
• Carbohydrates

  • Condensation reaction ( bonds are made;water is lost)
• All carbohydrates are C6H12O6
• Glucose is a hexo sugar
• Fructose = C6H1206

  Galactose = C6H12O6

  Pentose = C5H10O5
• 3 main groups of carbohydrates

  • Manosacharids e.g glucose, fructose (1) manosachoride
  • Disachoride e.g sucrose, maltose, lactose (2)
  • Polysachoride e.g starch, glycogen (3+)
• Fructose is soluble

  Glucose is less soluble
• Carbohydrates make glycosidic bonds
• Glucose and glucose= maltose

  Glucose and fructose = sucrose

  Glucose and Galactose = Lactose

  Glucose x Many(lots of sugar together) = starch

  If you want to seperate them you use hydrolysis

  Starch is storage molecule insoluable compact- coiled/branched
• Two features of starch that make it a good storage molecule

  • Starch is insoluble and doesn't cause osmosis
  • Compact because its branched/ coiled
• Describe how a peptide bond is formed between two amino acids to form a dipeptide

  When two amino acids want to link together to make dipeptide they use condensation reaction and are left with H2O between amine group and carboxyl group
• Different order of amino acids form different bonds and therefore different tertiary structures
• the type of reaction catalysed by the enzyme lactase is hydrolysis
• Active site 


  Specific tertiary structures complementary to the substance
• Globular protein structure 


  Is held together by hydrogen bonds
• Substrate 


  Molecule that binds the active site for a reaction to occur. The molecule that gets broken down/built up
• Activation energy


  Minimum amount of energy needed for a reaction to occur
• Substrate


  Binds to enzymes active site by lock and key model/ the more modern induced fit model
• Enzymes catalyze both anabolic and catabolic reactions

  Anabolic- building up e.g combining amino acids to make proteins

  Catabolic- breaking down e.g breaking a protein into amino acids by hydrolysis
• What is the small part of enzymes involved in catalysis called?

  Active site
• What happens to molecules that don't match the active site's shape?

  They cannot fit or bind to it
• Lock and key enzyme action

  • Small part of enzymes are involved in catalysis- called the active site and consists of a few amino acids
  • The shape of the active site is very precise and is maintained by the tertiary structures of the enzyme
  • Molecules that don't have the same shape as the active site cannot fit or bind into it.
• Lock and key enzyme action part 2

  • The substrate molecule fits exactly into the active site like a key fitting into a lock, where it is held in place by various bonds- this forms an enzyme-substrate complex
  • The enzyme-substrate complex enables the reaction to happen moe easily.
  • Either one substrate molecule is split into two or more products or two or more substrate molecules are joined together
  • Only exists for a fraction of a second until the products are formed
  • The product then leaves the active site and the enzyme is free to take part in another reaction
• Enzyme Action- induced fit

  • Proposes that the active site is not initially an exact fit for the substrate molecule
  • As the substrate moves into the active site, forces between the two molecules distort the enzyme and its active site so it envelops the substrate like a glove.- enzyme-substrate complex lowers the activation energy of the reaction
  • Once the reaction is complete, the products leave the active site and the enzyme changes back to its original shape.
• Enzymes lower activation energy but the start and end results are still the same
• Increased temperature and reaction rate

  • At a higher temperature particles have more kinetic energy
  • So they move around more
  • So there are more collisions between substrates and active sites
  • So more enzyme-substrate complexes form
• Effect of temperature on enzymes

  • They move faster so are more likely to collide and interact with each other and the enzyme
  • Above the optimum, the bonds that maintain the enzyme's shape starts breaking down, irreversibly changing the shape of the active site. This leads to a loss of enzyme activity- the enzyme starts to denature
  • The decrease in rate caused by the enzyme denaturing overwhelms the increase in rate caused by increased kinetic energy- causes the overall rate of reaction to drop shrply above the optimum.
• Trypsin


  • Protease enzyme
  • Found in small intestine
  • Starts the process of protein digestion by breaking log protein chains into smallest polypeptides
  • It cuts all specific amino acids (lysine and arginine)
  • Subsequent proteases cut the polypeptides further into dipeptides or amino acids
  • Produced by the pancreas in an active form called trypsinogen.
  • Useful as it helps break down proteins in the digestive system.
• Amylase

  • Is a carbohydrate
  • Digests starch into smaller molecules (maltose) which in turn is cleaved into two glucose molecules by maltose
  • Produced in salivary glands and the pancreas
  • Salivary amylase begins starch digestion in the mouth and continues to work in the stomach
  • Then it gets topped up by pancreatic amylase in the small intestine
• Lipase

  • Family of enzymes that break down triglycerides into three fatty acids and glycerol
  • Essential to break down cell membranes
  • Produced in the pancreas, mouth and stomach
  • This enzyme works together with ble, which your liver produces
  • Bile emulsifies(spreads out) lipids, making them more accessible to the enzymes.
  • Pancreatic lipase digest lipids in the small intestine.
• Cell cycle

  • How cells duplicate and divide
  • Cells need to divide all the time to replace dead cells, for growth and repair
  • Length of the cell cycle can vary between organisms- depends on cell type
• The nucleus

  • When a cell is not dividing, the chromosomes are organised into long entangled structures- chromatin
  • During cell division, the chromatin condenses into chromosomes (consists of DNA). DNA contains the heredity info and instructions for cell growth, development and reproduction.