1.4 Enzymes Flashcards
what is the shape / structure of enzymes?
tertiary structure 3D shap
how is the active site held together?
held by peptide, hydrogen, ionic and disulphide bonds
what is the lock and key model?
- Substrate(s) and the active site of the enzyme come into contact
- Substrate(s) binds, enzyme-substrate complex forms
- Reaction takes place, product(s) formed in an enzyme-product complex
- Product(s) released from the active site. The active site is now free to bind to another substrate
what changes occur to the enzyme at the end of the reaction?
no changes, enzyme remains unchanged
the induced fit hypothesis
A model of enzyme action which states that once a specific substrate binds to the active site, the enzyme undergoes subtle conformational changes. This puts a strain on the substrate, lowering the activation energy for the reaction
when does this reaction occur?
at lower activation energy
what are intracellular enzymes?
An enzyme that acts within cells, e.g.
catalase
what are extracellular enzymes?
An enzyme that is secreted by cells and
functions outside of cells, e.g. amylase.
how does low temperature affect enzymes?
at low temperatures, there are low KE so fewer successful collisions where the substrate is able to enter the active site of the enzyme and form products
how does high temperature affect enzymes?
● As temperature increases molecules have more KE
● Molecules moves faster and collide more frequently
● More enzyme-substrate complexes form
● Rate of reaction increases
● Rate peaks at the optimum temperature
what happens if the temperature continues to increase?
● Temperature increases above the optimum
● Increased vibrations break hydrogen and ionic bonds in tertiary structure
● Active site changes shape, enzyme is denatured
● No more enzyme-substrate complexes can form
● Rate of reaction decreases
How does substrate concentration affect the rate of an enzyme-controlled reaction?
If enzyme concentration is fixed, the rate of
reaction increases proportionally to the
substrate concentration.
Once all active sites become full, the rate of
reaction becomes constant - graph plateaus
(enzyme concentration is a limiting factor)
How does enzyme concentration affect the rate of an enzyme-controlled reaction?
If substrate concentration is fixed, the rate of
reaction increases proportionally to the
enzyme concentration.
When all of the substrates occupy active
sites, the rate of reaction remains constant -
graph plateaus (substrate concentration is a
limiting factor)
what effect does low substrate conc have?
it becomes a factor that is limiting the rate of reaction
what does further increase in substrate conc do?
has no effect as it is no longer the limiting factor
when does the rate of reaction become plateaus
when all enzymes have full active sites
the enzyme conc becomes the limiting factor
what are the advantages of using immobilized enzymes for blood glucose monitoring?
shows accurate results
the enzyme is more stable
specific / will only give results for glucose
detects very low conc
define metabolism ?
The sum of all the enzyme controlled
chemical reactions taking place in a cell
State the two main types of reactions that make up metabolism
Anabolic and catabolic reactions.
what is anabolism ?
A set of metabolic pathways that
synthesise complex molecules from
smaller, simpler molecules
what is catabolism?
A set of metabolic pathways that
breakdown complex molecules into
smaller, simpler molecules
what is an enzyme?
● A biological catalyst used to speed up the
rate of intracellular and extracellular
biochemical reactions
● Not used up or permanently altered
what is the active site of an enzyme?
A region on an enzyme that is complementary to the shape of a specific substrate. The substrate binds and the reaction takes place.
why is the active site described as ‘specific’?
● The 3D structure of each enzyme (including the active site) is unique due to the presence of different side chains and branches
● Only specific substrates complementary to the active site can bind
