Enzymes and how they work

Question 1

what is the active site

Answer 1

parts of the enzyme that react with the substrate (and cofactors) in the reaction

Question 2

What is a co-enzyme

Answer 2

– small diffusible organic residue that participates in the enzyme- catalyzed reaction
– stable to heat

Question 3

What is a prosthetic group

Answer 3

coenzyme covalently or firmly bound to the enzyme so that it is not removed by dialysis

Question 4

What is a zymogen

Answer 4

– an inactive precursor of an enzyme

Question 5

what is a holoenzyme

Answer 5

the protein (apoenzyme) with coenzyme or ions required for activity

Question 6

What is a an apoenzyme

Answer 6

The protein without coenzyme or ions required for activity. Labile to heat

Question 7

What is a substrate

Answer 7

A molecule on which an enzyme performs a reaction

Question 8

What do lyzozymes do

Answer 8

Protects against harmful bacteria

Causes bacteria to lyse and lose their cell content

Question 9

Where are lyzozymes found

Answer 9

Tissue fluids and secretions
saliva
nasal mucus
tears

Question 10

What is the bacterial cell wall made of

Answer 10

peptidoglycan

Question 11

What’re the condition for the chemical hydrolysis of peptidoglycan

Answer 11

– 4-6 M HCl

– sealed tube at 105 °C – 12 hours

Question 12

What are the building block s of peptidoglycan

Answer 12

N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

Question 13

How do lyzozymes hydrolyse peptidoglycan and at pH does this occur very quickly.

Answer 13

hydrolyses the beta 1:4 bond in the glycol chain between NAG and NAM, happens quickly when close to neutral pH.

Question 14

Name 4 serum proteases

Answer 14

• Trypsin
• Chymotrypsin
• Elastase
• Thrombin

Question 15

What amino acids is the charge relay system in serum proteases made of

Answer 15

Serine
Histidine
Aspartate

Question 16

Why are zymogens secreted instead of the proteolytic enzyme

Answer 16

the enzyme will digest proteins and is a hazard to the body

Question 17

Give three examples of zymogens

Answer 17

– Pepsinogen
– Trypsinogen
– Chymotrypsinogen

Question 18

Describe the activation of pepsinogen

Answer 18

Chief cells in stomach release pepsinogen. Parietal cells release HCl. HCl cleaves and activates pepsinogen

Question 19

Describe the activation of trypsin

Answer 19

trypsinogen is secreted by the pancreatic duct and enterokinase from the brush border of the duodenum activates it into trypsin. Trypsin then activates other zymogens

Question 20

how many amino acids in chymotrypsinogen and how many disulphide bridges and what affect does this have on the active site

Answer 20

245 amino acids
5 S-S bridges
In this state the three portions of active sites cannot come together

Question 21

Describe the activation of chymotrypsinogen

Answer 21

• Trypsin cuts bond between Arg15 and the next residue (p-chymotrypsin)
• Cut at Leu13 removes a dipeptide
• Cut at Tyr146 and Asn148 removes another dipeptide (a-chymotrypsin)

Asp102, His57 and Ser195 can come together and form the active site