enzymes

• What are enzymes

  globular proteins which interact with substance molecules, causing them to react faster
• Role of enzymes *catalysed by enzymes

  - chemical reactions required for growth are anabolic (building up) reactions

  - energy is released by catabolic (breaking down) reactions

  - digestion of large starch molecules
• Role of enzymes in metabolism


  Only happens as a result of the control and order imposed by enzymes
• Factors affecting enzyme activity

  -temperature

  -pH

  - substrate and enzyme concentration
• Temperature- effect on enzymes

  Initially as temperature increases, so does enzyme activate as enzymes gain more kenetic energy and they are more successful collisions with substrate molecules.

  - more enzyme-substrate complied being formed = more product formed at a given time

  - after a certain temperature (45°C), the bonds within the enzyme begin to vibrate (bonds hold enzyme shape together) so much that they break- results in the denaturation of the enzyme
• What is denaturation?


  When the substrate cab no longer fit into the active site due to changes in the shape of the enzymes. Results in enzyme activity dramatically decreasing. Once all enzymes are denatured, the enzyme activity will completely cease
• Examples of cold environment


  Deep oceans, high altitudes, polar regions
• Hot environment examples


  Hot springs, deep sea hypothermal vents
• Optimum temp for enzymes in body

  40 °C
• What happens to enzymes which are in cold environments?


  They tend to have more flexible structures- particularly at the active site. This means that it's less stable than enzymes which work in hot environments. Also smaller changes in temperature will denature them.
• What happens to enzymes in hot environments?

  Have more hydrogen bonds and sulfur bridges in tertiary structures so have an increased stability. The shapes of these enzymes and their active sites are more resistant to change as temperature increases.
• What does change in pH refer to

  Change in hydrogen ion concentration
• High concentration of hydrogen ions =

  Low pH (acidic)
• Low concentration of hydrogen ions =

  High pH (alkaline)
• Why are all enzymes affected by changes in pH?


  They are proteins - held together by hydrogen and ionic bonds between amino acid R-groups. Bonds are a result of interactions between polar and charged molecules in the amino acids (primary structure)
• What is the optimum pH?


  when the hydrogen conc. is right for the active site to be the right shape
• What happens when the pH changed from optimum?

  The structure of the enzyme and active site changes- of optimum pH returns, the enzyme will revert back into its original shape (renaturation)
• What happens if the pH changes significantly?

  The structure of the enzyme is irreversibly altered and the active site will no longer be complementary to the substrate. Rate of reaction decreases
• Enzymes will only function with (ph)


  Narrow pH range
• What happens of the concentration of the substrate is increased?


  The number of substrate molecules, atoms or ions in a particular area increases- leads to a higher collision rate with the active sites
• What happens when the concentration of enzymes increase?

  The number of active sites in an area or volume increases- leads to more enzyme-substrate complexes and at a faster rate
• What's the maximum rate of reaction called?

  Vmax
• What is Vmax


  When all actives sites are occupied by substrate particles- only way to increase rate of reaction is to add more enzymes or increase the temperature. If enzymes are added, the volume of substrate molecules will eventually become a limiting factor.
• What does -ase show? E.g catalASE

  An enzyme
• What does catalase catalyse?


  break down hydrogen peroxide to water and oxygen
• Where is catalase present and why does it mean it's a good for experiment


  In plant and cell tissue, it's readily available
• What needs to happen for a reaction to occur?

  Molecules need to collide in the right orientation
• How to increase rate of reaction

  Temperature or pressure increase- increase in number of successful collisions
• What is the activation energy

  The energy that needs to be supplied at the start of the reaction- sometimes the amount of energy needed is so large that it prevents the reaction happening
• What is the active site?


  An area within the tertiary structure of an enzyme which has a shape that is complementary to the shape of a specific substrate molecule
• What is formed when an enzyme and substrate bond?

  Enzyme-substrate complex
• What happens when the substrates react in the enzymes

  A product-enzyme complex is formed which is then released. The enzyme is unchanged and are able to take part in subsequent reactions
• Why are temporary bonds formed between the enzymes and substrate?

  The atoms are close enough to react- the R-groups in the active sites of the enzyme will also interact with the substrate. This puts a strain on the bonds within the substrate which helps increase rate of reaction
• What does the induced fit hypotheses suggest

  The active site of the enzyme changes shape as the substrate enters
• What do the weak interactions between enzyme and sun stares cause


  Induce changes to the enzymes tertiary structure and bonding is strengthened (strains on substrate molecule). Lowered activation energy
• What is an intracellular enzyme


  An enzyme which acts within cells
• Intraceullar enzyme


  Catalase- breaks hydrogen peroxide in water and oxygen gas
• What's an extracellular enzyme

  Enzymes which work outside of the cell
• Why are extraceullar enzymes needed?


  Break down the molecules needed outside the cell as they can't enter directly due to their size. Often break down nutrients e.g proteins and polysaccharides (digestion)
• Extracellular enzymes in multicellular organisms


  After multi-cellular enzymes eat food, the nutrients are taken into the digestive system where it's broken down by digestive enzymes so or can be absorbed into the blood stream. Then transported around the body and used in cellular reactions