Chapter 3 - Enzymes - activity determination

Question 1

What does Oxidoreductases catalyze?

Answer 1

They catalyze reactions of oxidation and reduction

Question 2

Which 4 groups are Oxidoreductases classified into?

Answer 2

• oxidases
• dehydrogenases
• hydroperoxidases
• oxygenases

Question 3

What does oxidases do?

Answer 3

They transfer hydrogen from a substrate to oxygen

Question 4

What does dehydrogenases do?

Answer 4

They transfer hydrogen from one substrate to another (not oxygen); they require coenzymes/prosthetic groups such as NAD, ADP, FAD, FMN.

Question 5

What does hydroperoxidases do?

Answer 5

They use hydrogen peroxide or organic peroxides for oxidation of differen substrates.

Question 6

What does oxygenases do?

Answer 6

They incorporate oxygen into a substrate.

Question 7

Peroxidase = ?

Answer 7

Hydroperoxidases

Question 8

Which enzymes use hydrogen peroxide to oxidize different substances (peroxidase actvity)?

Answer 8

• catalase

- peroxidase (hydrogenperoxidase)

Question 9

Where is catalase found?

Answer 9

• blood
• liver
• kidney

Question 10

Where is peroxidase found?

Answer 10

• plants
• leucocytes
• milk

Question 11

Catalase uses ______ _______ as an electron acceptor.

Answer 11

Hydrogen peroxidase

Question 12

Which color does oxidized benzidin have?

Answer 12

Intensive blue color

Question 13

Give an example of a copper containing enzyme:

Answer 13

o-Diphenol oxidase

Question 14

Where are o-Diphenol oxidase present?

Answer 14

They are present in plants

Question 15

What does o-Diphenol oxidase do?

Answer 15

o-Diphenol oxidase transfer hydrogen from a substrate to molecular oxygen forming water

Question 16

What does the Cytochrome oxidase do?

Answer 16

Cytochrome oxidase catalyzes the final step of the electron transport chain (respiratory chain); the transfer of electrons from cytochromes c to oxygen.

Question 17

What does the cytochrome contain?

Answer 17

It contains two molecules of heme, and two ions of copper

Question 18

What reduces cytochrome c?

Answer 18

P-phenyldiamine

Question 19

Succinate dehydrogenase:

Answer 19

• is a compinent of the electron transport chain (respiratory chain) and the tricarboxylic acid cycle ( TCA, Krebs cycle)
• is bound to inner mitochondrial membrane
• contains; FAD and iron sulfur (Fe-S) centres as prosthetic group
• Malonate (HOOC-CH2-COOH), succinate analogue, is a very strong competitive inhibitor of this enzyme

Question 20

What is the third class of enzymes (EC 3) called;

Answer 20

Hydrolases

Question 21

What does Hydrolases do?

Answer 21

They hydrolyze different types of chemical bounds such as;

• peptide bonds (peptidase, e.g pepsin, trypsin, chymotrypsin, carboxy-peptidase, aminopeptidase)
• glycosdidic bonds (glycosidases, e.g. amylase, maltase, sucrase)
• ester bonds (esterases, e.g lipase, phosphatase.

Question 22

Arginase

Answer 22

Is a hydrolase which catalyzes the last reaction of the urea cycle in the liver.

Question 23

Is urease present in humans?

Answer 23

No

Question 24

Where is urease present?

Answer 24

In many plants and microorganisms

Question 25

What is lysozyme?

Answer 25

It is an proteolytic enzyme present in saliva, tears, nasal mucus, gastric juice, milk, and egg white.

Question 26

What does the lysozyme do?

Answer 26

It destroys cell walls of many airborne gram-positive bacteria, and uses its antibacterial antivirus, and antiflammatory drug

Question 27

What is the first class of enzymes called?

Answer 27

• Oxidoreductases