Biochemistry - Enzymes as Biological Catalysts Flashcards
What is the function of an enzyme?
Enzymes CATALYSE specific reactions which make up a metabolic process. Impact on health and disease.
What does an enzyme do with regard to Equilibrium?
An enzyme speeds up the rate at which equilibrium is achieved.
What do enzymes NOT affect?
The POSITION of EQUILIBRIUM in a reaction.
Enzymes are … to to their substrates.
SPECIFIC.
What are enzymes? MESP
Mostly Protein
Efficient
Specific
Potent
Enzymes - M
Mostly Protein
e.g. RNA - ribozymes
Enzymes - E
Efficient
Can increase rate by a factor of 1020.
Can work at various temperatures.
At what temperatures can enzymes work at?
Enzymes can work at:
Body Temperature
Neutral pH
Acidic Conditions
Aqueous Solutions
Enzymes - S
Specific
They have a limited substrate range.
Can distinguish between STEREOISOMERISM.
Enzymes - P
Potent
Enzymes can convert many substrate molecules into product per second.
What is the Activation Energy?
Ea
The activation energy is the minimum energy required for a reaction to take place.
What intermediate product is produced in a reaction going from Substrate to Products?
TRANSITION STATE.
What is the Transition State?
An intermediate compound with the GREATEST FREE ENERGY in a reaction.
Explain the ‘Cocktail Party’ Analogy.
You are in a room full of people with the intention to meet the ‘right’ person. The greater the number of people, the greater the likelihood of meeting the person you’re looking for.
What effect do enzymes have on the Activation Energy?
Enzymes LOWER the Activation Energy.
How do enzymes lower the Activation Energy?
Enzymes lower the activation energy by providing alternative pathways for reactions.
What is Glycogen Storage Disease?
Enzyme Deficiency
Failure for Glycogen to enter “phosphorylated state”.
Can’t part-take in Glycolytic pathway.
Catalytic activity of enzymes depends on what?
Catalytic activity of enzymes depends on the presence of CO-ENZYMES and COFACTORS.
What are COFACTORS?
Cofactors are METAL IONS (inorganic).
What are CO-ENZYMES?
Co-enzymes are ORGANIC MOLECULES (organic organ).
What is a METALLOPROTEIN?
A co-factor with a metal co-ordination centre in an enzyme.
The association between an enzyme and a coenzyme is…
TRANSIENT
not permanent
What happens to Co-Enzymes during the course of a reaction?
They may change shape/structure/charge but are regenerated.
What is a PROSTHETIC GROUP?
A prosthetic group is a TIGHTLY BOUND CO-ENZYME.
Name an example of PROSTHETIC GROUP.
Haem in Haemoglobin and Cytochromes.
What is a APOENZYME?
An enzyme WITHOUT a COFACTOR.
What is a HALOENZYME?
An enzyme WITH a COFACTOR.
Halo - circle - centre - with metal centre
APOENZYME + COFACTOR =
HALOENZYME
Examples of Cofactors include…
Zinc
Iron
Copper
What is the function of metal ions? (2)
Stabilise Transition States
Involved in Redox Processes
What are the functions of Co-enzymes?
Involved in Redox Processes (NAD+, FAD)
Involved in Group Transfer (CoA, ATP transfers PO3-)
Where are many Co-enzymes derived from?
Vitamins.
What do the symptoms of vitamin deficiencies reflect?
They reflect the loss of ENZYME ACTIVITIES.
What is NAD?
Nicotinamide Adenine Dinucleotide (NAD)
What does NAD+ go to?
NADH
What do NAD and NADH do?
They donate and receive electrons.
Easily regenerated.
Where does the substrate bind in an enzyme?
Substrate binds to the ACTIVE SITE.
What is the INDUCED FIT?
The induced fit occurs when an active site changes conformation to bind more tightly to a substrate to increase likelihood of a reaction.
Describe the Lock-and-Key Model.
The model illustrates that an enzyme’s active site is COMPLEMENTARY to the shape of the substrate.
What is an Active Site?
A cleft/crevice.
The Active Site contains …?
AMINO ACIDS
What are the Amino Acids in an active site essential for? (2)
Catalytic Activity
Specific Interactions
What two factors affect enzyme activity?
Temperature
pH
What is an ISOZYME?
Isoforms of enzymes
Catalyse same reaction but have a different sequence of amino acids and different structure.
What are ISOFORMS?
Several different forms of a protein.
Similar function to another protein but differing genes (slightly).
What are examples of Active Sites?
Three pancreatic serine protases:
Chemotrypsin
Trypsin
Elastase
When can different isozymes be synthesised?
Different isozymes can be synthesised during FOETAL and EMBRYONIC development.
Where are isozymes present?
Isozymes are present in different TISSUES and CELLULAR LOCATIONS.
Name an example of a tissue specific isoform.
Lactate Dehydrogenase
