✨Module 2: Enzymes Flashcards
(27 cards)
Intracellular enzymes …
Extracellular enzymes …
Act within cells. DNA and RNA polymerase, catalase.
Work outside the cell that has made them.
Name two extracellular enzymes found in the digestive system.
Pepsin - protease found in the stomach and breaks down proteins into amino acids that can be absorbed into the small intestine.
Amylase - found in saliva and catalyses the hydrolysis of starch into maltose. Maltase then functions. Glucose is small enough to be absorbed by cells lining the digestive system and absorbed into the bloodstream.
Why are enzymes important for life?
They speed up important chemical without damaging cells and without the use of heat.
Define enzyme.
Biological catalyst that speeds up chemical reactions without being used up itself.
What is the induced fit model for how an enzyme actually works?
Active site forms a complementary shape AFTER binding. R-groups of amino acids in active site interact with substrate, putting strain on the bonds in substrate and therefore lowering activation energy.
How does temperature affect enzyme activity?
-> Up to optimum, enzymes and substrates gain KE so move around more. So greater chance of more successful collisions per unit time, so more ESC’s formed. Increases rate of reaction.
-> After optimum, the extra KE breaks bonds in the tertiary structure of enzyme (hydrogen bonds first). Active site changes shape and the enzyme denatures. Less ESC’s formed as the active site no longer has a complementary shape to the substrate.
How does pH affect enzyme activity?
-> As pH moves away from optimum, change in ratio of H+ and OH- interferes with hydrogen and ionic bonds so they break.
-> Active site changes shape and enzyme denatures no longer complementary to substrate. Less ESC’s form so rate of reaction decreases.
How does substrate conc affect enzyme activity?
-> As substrate molecules increase, higher probability that substrates collide with enzyme to form ESC’s. The enzyme is in excess at this point.
-> Graph straightens out as all active sites are used up. Enzyme concentration is now acting as a limiting factor.
-> It reaches the Vmax point where all active sites are occupied by substrate molecules so no more ESC’s can form until products are released. The only way to increase the rate of reaction would be to add more enzyme or increase the temp.
Carboxylase.
Decarboxylase.
Add CO2 to a molecule. Addition of CO2 to RuBP.
Remove CO2 from a molecule. Pyruvate decarboxylase catalyses the decarboxylation of pyruvate during respiration.
Protease.
Carbohydrase.
Lipase.
Break down peptide bond/protein. Pepsin catalyses breakdown of proteins into small peptides in stomach.
Break down carbohydrates into simple sugars. Amylase - starch into maltose in saliva and maltase converts maltose to glucose in SI.
Break down lipids into glycerol + fatty acids. Human pancreatic lipase breaks down dietary fats in digestive system.
Hydrolase.
Phosphorylase.
Add water to break a bond/hydrolysis.
Add phosphate group to molecule. Glycogen phosphorylase catalyses breakdown of glycogen into glucose as homeostasis/glycogenolysis.
What does the temperature coefficient (Q10) allow us to see?
What happens to rate of reaction when we increase temperature by 10 degrees C.
Many enzymes have Q10 of approx 2, which means the rate of reaction doubles when we increase the temperature by 10 degrees C.
Q10 no longer applies after the enzyme has denatured.
Why may thermophiles be well adapted to hot environments?
The enzymes present in these organisms are more stable due to the increased number of DS bridges and hydrogen bonds in their tertiary structure. The shape of these enzymes are more resistant to change as temperature rises.
What is an enzyme co-factor?
What are the 3 types of enzyme co-factor?
Non-protein molecules that increase rate of reaction by enabling enzyme activity.
Prosthetic groups, inorganic co-factors, coenzymes (organic).
What is a prosthetic group?
Give an example of one.
(Don’t need to know)
Non-protein cofactors which are permanently bound to the enzyme. Prosthetic groups allow enzymes to make ESC’s without being directly involved in the reaction. The protein is then known as a conjugate protein.
Zn2+ in carbonic anhydrase. It breaks down CO2 in RBC’s.
What is an inorganic co-factor?
Give an example of one.
Non-protein inorganic molecules which enable ESC’s to form without being directly involved in reaction.
Cl- binds to the allosteric site in amylase.
What is an allosteric site?
How does Cl- cofactor function?
Attachment site on enzyme that is away from the active site and alters shape.
Cl- acts as an allosteric activator where it attaches to the allosteric site and change the shape of the active site so it becomes complementary to the substrate.
What is an allosteric inhibitor?
Attaches to allosteric site and changes active site shape so it is NO LONGER complementary to substrate. This decreases rate of reaction.
What is a coenzyme?
Non-protein organic molecules which bind temporarily to enzymes and are often changed by it. Often act as carriers moving chemical groups between enzymes.
What are coenzymes often made of?
Nucleotides.
Where are co-factors and coenzymes obtained?
Co-factor - from minerals.
Coenzymes - from vitamins.
What is a competitive inhibitor?
They have a similar shape to substrate and bind to active site temporarily so they compete with substrates. Rate of ESC’s formed decreases.
Statins are competitive inhibitors of the enzyme that produces cholesterol.
What is a non-competitive inhibitor?
Binds to the allosteric site, resulting in changes to tertiary structure of enzyme. Less ESC’s form.
What is reversible inhibition?
When an inhibitor temporarily binds to an enzyme due to weak hydrogen/ionic bonds (usually competitive inhibitors).
