Enzyme Key Concepts Chapter 3 MDCAT Biology Entry Test Preparation. Enzymes important points gathered from admission test practise exams. Important details and numerical values are included in the chapter-by-chapter notes for Biology in the MDCAT.
Key Concepts in Enzymes Chapter 3
Here is list of enzymes key points from mdcat Biology for entry test preparation.
- Enzyme is a Greek word: en- inside, Zyme – yeast
- As it is Best discovered in yeast that’s why its name is an enzyme.
- the First enzyme was discovered by Anselme Payen in 1833, and the enzyme was the carbohydrate digesting enzyme; diastase.
- The word enzyme was first coined by Wilhelm Kuhne in 1877.
- The first enzyme was purified by Sumner in 1926.
- Enzymes are globular proteins.
- All enzymes are proteins except ribozyme which is chemically RNA but performs the activity of the enzyme.
- rRNA found in the large subunit of the ribosome is ribozyme and is also called peptidyl transferase which has a role in the formation of the peptide bond. ,
- Enzymes are named by adding ‘use’ to the name of substrate they act, ‘ e.g. proteases, lipases, etc.
10.Enzymes are named according to the types of reaction they catalyze, e.g.
wides, reductases, etc.
- Enzymes are named by taking into consideration both the substrate acted upon and the type of reaction catalyzed, e.g. DNA-polymerase.
12.Some enzymes are named as per substance synthesized e.g. rhodonite catalyzes the synthesis of rhodonite from hydrochloric acid and sodium thiosulphate.
13.Substrate is a substance on which an enzyme acts.
- The region of the enzyme where the substrate attaches is called the active site.
15.Mostly active site is composed of 3 – 12 amino acids. These amino acids have a specific alkyl group that has a role in catalyzing the reaction.
- The region of the enzyme other than the active site is called an allosteric site.
17.Some enzymes do not work until a non-proteinous part attached, this non-proteinous part is called a cofactor. ,
- If the cofactor is organic then it is called co-enzyme. For example NADP,
FAD etc. = contains vit “
- Co-enzyme mostly composed of part of vitamin B. e.g . .
B3 (also called niacin or nicotinic acid or nicotinamide), FAD contains vIt 82 (ribof7avin) co-enzyme A contains vit B5 pantothenic acid)
2O.If the cofactor is inorganic then it is called a prosthetic group
21.Some enzyme required metallic ions for its best activity e.g hexokinase is the first enzyme use in glycolysis requires Mg+” ion, carbonic anhydrase require Zn++ ion, enterokinase require Ca++
22.An enzyme without its cofactor is called an apoenzyme
- Enzyme with its cofactor is called Holoenzyme
- Classification of enzymes: Enzymes are classified as
These enzymes catalyze the oxidation-reduction process it includes
oxidase, dehydrogenase, oxygenate, and hydro peroxidase.
These enzymes transfer a functional group so amino, or methyl groups from one molecule to other molecules. This includes:
e. phosphotransferase ( kinase)
27. Hydrolases: Enzyme which breaks the bond with the addition 0 water is called hydrolases. e. g, peptidase, carbohydrates, endonuclease, etc.
28.Wase: These enzymes catalyze the reaction in which certain groups are added to a double bond or removed to form a double bond. This includes:
a. Decarboxylase b. Synthase”
Synthetase forms a bond between two substrates in the presence of.
energy like A TP, GTP, etc. For example; aminoacyl tRNA synthetase connects specific amino acids with the 3′ end of tRNA, DNA ligase forms a bond between two nucleotides.
A heterogeneous group of enzyme which converts one isomer into another isomeric form. For example mutase.
31.Enzyme decreases the activation energy.
32.Activation energy Is the amount of energy required to react two molecules.
- Enzyme activity is affected by the amount of substrate, pH, and temperature.
34.Lock and the key hypothesis were proposed by Emil Fischer in 1890.
35.According to this hypothesis; “For a specific”substrate there is a specific enzyme as for q specific lock there is a specific key”
36.lnduced fit hypothesis is proposed by Koshland in 1959.
37.According to the induced fit hypothesis; “Enzymes can slightly undergo some changes for the attachment of substrate during chemical reaction” “
- The agent which blocks the activity of the enzyme permanently or temporarily is called an inhibitor. ·
39.lnhibitor may be reversible or irreversible.
- The inhibitor which blocks the enzyme permanently or denatures the enzyme is called irreversible. Eg cyanide, heavy metal.
41.inhibitor temporarily blocks the enzyme is called reversible. Most of the medicines are reversible inhibitors of enzymes.
- Inhibitor which is structurally similar to the substrate and attached to the
active site of the enzyme is called”competitive inhibitor. e.g sulphonamide drugs.
43.lnhibitor which is dissimilar from the substrate and attached to the site other than the active site is called a non-competitive inhibitor. E.g insecticides, heavy metal, and cyanide.
44.Feedback inhibition is the mechanism in which the product of reaction when accumulated to a certain level then product inhibit the enzyme activity.
Difference b/w synthetase and synthase Syrrthatase requires energy for a bond formation like ATP, GTP while Synthase does not require energy for bond formation.
Synthetase is included in ligases and synthase is included in lyases.
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