Module 2.1.4 Enzymes Sambrook Flashcards
What is the turnover number ?
The number of reactions per enzyme per second
What are enzymes
-biological catalysts
- speed up metabolic reactions
- they remain unchanged
What are chemical catalysts?
-extreme in the following:
High Temp
High pressure
Ph
What are biological catalysts?
-low temp
-normal pressure
-neutral ph
-specific
-catalyse in both directions
What are enzymes made of?
-proteins (amino acids)
What does a gene mutation do to amino acid sequence of enzymes?
-no change as it’s degenerative
Or
-keep the protein the sme but change the structure
Or
-change the sequence enough so a totally different protein is made
What is the primary structure of enzymes?
The amino acid sequence
What is the secondary structure of enzymes?
Spiralling of the polypeptide
What is the tertiary structure of enzymes?
Folding of the polypeptide including the bonds between them giving the protein it’s specific shape-> including the active site
What is the quaternary structure of enzymes?
Multiple polypeptide chains jones together
Examples of metabolic disorders
-Tay sachs disease
-maple syrup urine disease
- phenylketonuria
Examples of structural disorders
-elhers danlos syndrome
-stone man syndrome
What are the 2 parts of the ACTIVE site?
-binding site
-catalytic site
What does the binding site do?
Bind and orient the substrate
What does the catalytic site do?
Puts pressure on the bonds-> reduces repulsion’s -> lowers the activation energy
How do enzymes lower the activation energy?
-put pressure on the bonds in the substrate when they bind to the active site
-this reduces the repulsion between the 2 substrate molecules holding them together allowing them to make a larger molecule
Explain the induced fit model
- substrate binds to the active site
-active site has a CONFORMATIONAL change
-if another substrate were to enter the active site it would not bind in the correct places so would not cause this change
What are intracellular enzymes?
Enzymes that act within the cell
Catabolic definition
Metabolic pathways that BREAKDOWN molecules
Anabolic definition
Metabolism pathways that SYNTHESISE larger molecules
What are intermediate substrates ?
Products of enzyme reactions that become substrates in another reaction
What is catalase?
-an enzyme found in living organisms that is exposed to oxygen
-hydrogen is produced but must be broken down
What are extra cellular enzymes?
Enzymes that act outside the cell
Explain enzyme action
-Mucor release hydrolytic enzymes from their hyphae that digest carbs, lipids and proteins
- the products are then reabsorbed into the hyphae
What does catalase do?
Breaks down hydrogen peroxide to oxygen and water
What’s a prosthetic group ?
-A non protein group that is part of a protein
What is a cofactor?
A non- protein molecule that has to be present for an enzyme catalysed reaction to happen
Why are all prosthetic groups cofactors but not all cofactors are prosthetic groups ?
All prosthetic groups are permanently bound to the enzyme
Name for a red blood cell ?
Erythrocyte
What is carbonic anhydrase ?
Used in erythrocytes to catalyse the conversion of carbon dioxide and water to carbonic acid
What do temporary cofactors do?
-Some bind to the substrate to give it a complementary shape to the active site
-some change the charges on the molecules which make it easier for bonds to form
What is a coenzyme?
Helps an enzyme carry out its function but is not used in the reaction itself
What happens to an enzyme above optimum temperature?
1)increased vibration breaks weak bonds
2)tertiary structure of the enzymes is changed
3)active site becomes denatured
4) substrate will no longer be able to bind to enzyme
How are optimum temperature and bonding related?
-the stronger the hydrogen and ion or bonds in the protein the higher the optimum temperature
What is psychrophilic bacteria
-cold loving bacteria
What is hyperthermophilic bacteria
Heat loving bacteria
Substrate rate of reaction calculation
1
——————————————-
Time taken to reach end point
Temperature coefficient calculation
Q10
R2 rate of reaction at (T+10C)
———————————————
R1 Rate of reaction at TC
What are inactive precursors?
-enzymes that are only activated when they’re needed
What do inactive precursors do?
Stops reactions from happening when they are not needed or would be harmful.
What do inhibitors do ?
Reduce the activity of enzymes
How do inhibitors work?
-bind to the enzyme and effect the way the substrate can bind to the active site
-by blocking the active site or causing a conformational change
Effect of ph on enzymes
-hydrogen and ionic bonds hold the tertiary structure of the protein
-an excess of H+ or OH- ions can cause these bonds to break
-this alters the active site and denatures the enzyme
Affect of substrate concentration on enzyme activity
-the greater the substrate concentration the higher the rate of reaction
-as the substrate molecules increases the likelihood of enzyme substrate complex formation increases.
-if enzyme concentration remains fixed but the amount of substrates increases all available active sites will become saturated
-any further increase in substrate concentration will not increase reaction rate
Effect of enzyme concentration on enzyme activity
-the higher the enzyme concentration, the greater the number of active sits available
-greater the likelihood of enzyme substrate complex formation.
-as long as their is a sufficient substrate available the initial reaction increases linearly
-if substrate is limited increase in enzyme concentration will not increase the reaction and substrate becomes a limiting factor
What is a competitive inhibitor
They only join to the active site
-either some of it or all of it
What does a competitive inhibitor do?
-stops the substrate from bonding to the active site
-can be reversible or irreversible
-when the inhibitor leaves the substrate can bind again
What is a non-competitive inhibitor?
-bind to anywhere on the enzyme other than the active site
What does an non competitive inhibitor do ?
-cause conformational change of the active site
-stops the substrate form being able to bind
-irreversible or reversible
What is a reversible inhibitor called ?
-inhibitor
What is a irreversible inhibitor Called ?
-Inactivator
How do competitive inhibitors affect rate of reaction ?
-if substrate concentration is increased the change of the substrate binding to the actuve sitr
-ROR increases as substrate concentration increases
-both reach same plateau just takes longer with inhibitor
What is negative feedback ?
-mechanism in which a negative effect of homeostasis is reuturned to normal
-some controlled by end-product inhibition
What is an end product inhibitor?
When the end product of a metabolic pathway becomes the inhibitor of the first part of that pathway
What does an end product inhibitor do m?
Stops the pathways from happening all the time and producing too much intermediate or end product
Examples of inhibitors
-ATPaze
-ACE
-Protease
-nucleoside reverse transcriptase inhibitor
