Enzymes 🔐 Flashcards
(21 cards)
What is an enzyme?
Biological catalyst which is used to speed up chemical/metabolic reactions without being used up by lowering activation energy.
What is activation energy?
Is the energy that must be overcome for the reaction to start.
Enzymes lower activation energy.
Why is a lower activation energy needed?
Reduces repulsion so the enzyme and substrate can bond more easily.
What is the lock and key theory?
Enzyme has active site with particular shape.
Active site is specific to substrate.
Substrate is complementary to the active site of the enzyme and binds to the active site creating an enzyme substrate complex.
Enzyme changes shape to facilitate the reaction (induced fit).
Enzyme product complex forms.
What happens to rate of reaction when temperature increases?
The enzyme activity increases until optimum temperature (Vmax) is reached.
Enzyme gains KE as temperature increase so move faster.
Collisions more likely to be successful.
Increases rate of reaction.
Too high of an increase leads to enzyme denaturing as there is a change in tertiary structure.
What happens to enzyme rate of reaction when temperature is lower?
Not enough kinetic energy for enzymes. Become inactive NOT DENATURED.
Why does rate reaction increase as pH increases?
More H+ ions present which interact with polar/charged R groups of the amino acids.
changes shape of enzyme which thus makes it lose its active site. ——-> acidic conditions.
—-> Affect ionic bonds and hydrogen bonds
Less H+ ions means less interactions which hold up shape of the enzyme.
Enzyme denatured in both conditions
What does the term Vmax refer to?
Maximum rate of reaction which links to the optimum temperature of the enzyme.
What does Q10 mean?
Represents how rate is increased by every 10oC.
How to increase in substrate/enzyme concentration increase rate?
More substrate or enzyme=more formation of enzyme substrate complex.
Eventually will reach maximum ESC that can be formed.
Certain extent—-> one becomes limiting factor
Line of graph starts to plateau as all active sites being occupied.
Extracellualr enzymes
Made via protein synthesis and released out of cell. Packaged and processed.
Amylase—-> Breaks down starch into maltose
Trypsin—-> Breaks down protein into amino acids
Has to have access to food outside cell.
Intracellular enzymes
Catalase needed in the breakdown of hydrogen peroxide = toxic
By product of metabolic reactions
Needs to be broken down quickly
What does the term inhibitor mean?
Chemical that can bind to enzyme in certain way to reduce its rate of reaction.
Competitive inhibitor?
Similar shape to substrate so active site isn’t changed.
‘Competing’ for same active site as substrate.
Non competitive inhibitor?
Has complementary shape to allosteric site which changes shape (conformational change) of active site.
How do competitive inhibitors reduce rate of reaction?
Compete with substrate for active site.
Bind to the enzyme active site so less active sites are available.
Less ESC are formed.
Add more substrates —-> higher chance of collisions so can outcompete CI —–> Rate restored back to Vmax
How do non competitive inhibitors reduce rate of reaction?
Binds to allosteric site
Permanent change
Changes tertiary (3D shape) of enzyme.
Less active site for substate to bind with.
Less ECS formed
Decreases rate/ Vmax not restored.
How does an inactive enzyme become active?
Apoenzyme (inactive) —> Holoenzyme (active)
Can become activated by another enzyme
Pepsinogen makes pepsin
Inactive so pepsin doesn't catalyse the stomach tissues.
Change in conditions. (temperature/pH)
What are cofactors?
Inorganic—–> from mineral ions
Temporarily bound
E.G: Chloride ions in amylase
What are coenzymes?
Specific cofactor
Organic——> vitamins
Temporarily bound.
e.g: NAD/NADP
carry hydrogen for respiration and photosynthesis.
What are prosthetic groups?
Permanently bound
e.g: Fe 2+ in haemoglobin.
Zn2+ in carbonic anhydrase
