Biology - 1.4.2 - many proteins are enzymes
what are the two main categories for tertiary and quaternary protein structures
fibrous and globular
what is a globular protein
spherical, soluble in water due to position of R group, and 3D shape such as enzymes
what is a fibrous protein
repetitive sequence of amino acids that are water soluble and often used for structural purposes such as collagen
what is an enzyme
biological catalysts which are globular proteins with a specific 3D shape that reduce the level of activation energy needed for a reaction
describe the induced fit model of enzyme action
the active site of the enzyme changes slightly in order to allow the substrate to bind
how is the substrate held in place
held with temporary bonds between amino acids
describe the lock and key model of enzyme action
substrate fits perfectly into enzyme active site and it does not require changing shape
what term is used to describe enzymes working inside cells
intracellular
what is the term used to describe enzymes working outside cells
extracellular
what determines the shape of the active site?
tertiary level of structure
what forms between the enzyme and the substrate
temporary bonds between the R groups
does an increase in temperature inc/dec the R.o.R?
increases
how does temperature affect the rate of reaction
gives the molecules (enzyme and substrate) more kinetic energy, leading to more frequent high energy collisions and therefore the chances of the formation of ES complexes
explain the curve of a temperature controlled enzyme reaction
1. low kinetic energy, less frequent collisions, less ES complexes
2. peak conditions for highest rate, higher chance of ES complexes formed
3. Bonds holding active site together are broken , causing denaturation, no complexes can be formed
does an increase or decrease in pH inc/dec the R.o.R
decreases
how does pH affect the rate of reaction
if the pH goes up or down, it can denature the enzymes by changing the charges on the amino acids in the active site, changing its' shape. Also breaks hydrogen and ionic bonds, altering shape
explain the shape of a pH controlled enzyme reaction
1. below the optimum pH, the rate of reaction is low or zero, because in acidic conditions, H+ ions break ionic/hydrogen bonds and denature
2. maximum rate achieved at optimum.
3. above the optimum pH, the rate of reaction is low or zero, because in alkaline conditions, OH- ions break ionic/hydrogen bonds and denature
formula for pH
pH = -log10 [ H+]
what does an enzyme do
lowers the activation of a reaction that it catalyses
how does enzyme concentration affect rate of reaction
the higher the enzyme concentration, the greater number of available active sites for enzyme substrate compleux formation, therefore an increased rate of reaction
explain the shape of an enzyme concentration controlled reaction
linear increase as more active sites become available
continues in a linear manner as long as sufficient substrate is available
if substrate is limited, at a certain point further enzyme increase will not increase rate
how does substrate concentration affect an enzyme controlled reaction
the greater the substrate concentration, the higher the rate of reaction
explain the shape of a substrate controlled reaction graph
If enzyme concentration is fixed, initial increases in substrate will result in a proportional increase in the rate of reaction.
If the concentration of substrate is limited, the graph will plateau as all active sites are saturated with a substrate, therefore no increase in rate
what is the point of saturation
where all active sites have formed an ES complex and there are none available