Enzymes

Homework 1

  • Biological catalysts

  • Production of ATP (energy) id a complex chain of reactions

  • Enzymes control the rate of chemical reactions, speeding them up in order to be able to maintain life functions (most organisms would otherwise conduct them too slowly) E.g Lactose is broken down into small bits to make it digestible for us by Lactase.

  • Metabolism = all the reactions that happen within the organism

  • Chemical reaction = A+B (reactants) → C+D (products)

  • Anabolic reactions = metabolic reactions joining together complex molecules

    • Protein synthesis, DNA synthesis and replication, carbohydrate synthesis (complex)

  • Catabolic reactions = metabolic reactions breaking down complex molecules

    • Digestion, cellular respiration, digestion of complex carbon compounds

  • Energy is the capacity to cause change

  • kcal = measurement of heat

  • Enzymes = specifically shaped globular proteins with an active site that perfectly fits the substrate it breaks down

  • The active site contains very few amino acids, reactions are catalysed by these

  • Fischers lock-and-key model now adapted to the induced-fit model

  • Enzymes change in shape when they come into contact with their substrates

  • Activation energy: energy required for a metabolic reaction, lowered by enzymes

  • Minimum rate of motion: kinetic energy provided by the substrate for the reaction

  • Energy barrier: there are fewer molecules with enough energy to pass the energy requirement for a reaction. There are two ways of solving this:

    • Increasing energy present in the molecule (addition of heat = more kinetic energy)

    • Lowering the energy required for the reaction

  • Reactions keep going until there is equilibrium between reactants and products

  • For reactions to occur, substrates and enzymes need to collide, which requires kinetic energy

  • Often, substrates or enzymes are anchored in structures like cell membranes

E+S ⇔ ES ⇔ E+P

E = Enzyme, S = Substrate, ES = Enzyme-Substrate Complex, P = Product

Class work 1

Protein Folding

Non—polar amino acids: not soluble in water

Amino acids can be positively or negatively charged

Amino acids are linked together by peptide bonds

Protein folding gives the protein its function, i.e channel proteins (aquaporin, sodium-potassium pump, etc) are folded to be hollow in the center, allowing for other molecules to pass through

Amino acid chains bend and form kinks, creating linkages and interactions

Denaturation = peptide bonds breaking down, protein loses structure and can no longer bind with the substrate at the active site

Exergonic reactions: energy is released, energy of reactants is higher than energy of products

Endergonic reactions: energy is consumed, energy of products is higher than energy of reactantser

Homework 2

  • Reactions depend on molecular collisions. The faster molecules move, the more they collide, and with greater energy

  • Reactions with no enzymes increase rate of reaction as temperature rises, but due to denaturation, reactions with enzymes have an upper limit

  • Intermolecular bonds become stressed and broken under high temperatures = denaturation

  • Denaturation can be temporary if the temperature returns to a suitable level, but if the temeprature is so high that it prevents the enzyme from returning to its native state

  • Denaturation from too high pH: when a solution becomes acidic, the amount of hydrogen ions rise, and these ions (positive) can bond with the negative charges in the amino acids in the active site (or subsrate) preventing them from bonding together by preventing a matching of charges

  • Denaturation from too low pH: when a solution becomes more basic, the amount of hydroxide ions rises, and these bond with positive charges in the amino acids, once again preventing matching of charges and thereby any form of bonding

  • Most enzymes operate in areas of the body with somewhat neutral pH levels, but there are exceptions

    • Pepsin is an enzyme active in the stomach

  • Collision theory: if the amount of reactant molecules increases, the rate of reaction will speed up, since there will be more molecules to collide with, generating more energy. This has an upper limit, since enzymes have a maximum speed they can operate at and only one active site

Class Work 2

  • Glucolysis

    • Part of respiration, step one of converting sugar into ATP, involves 10 enzymes

  • Higher molecular motion = higher chance of collision

  • Thing that accelerate molecular motion:

    • Increased substrate concentration (to a limit)

    • Increased temeprature (to a limit)

    • Increased pressure

    • Decreased area