Enzymes as Biological Catalysts

Question 1

enzymes speed up the rate at which a reaction reaches _____

Answer 1

equilibrium

Question 2

Enzymes DO NOT affect the equilibrium ____ of a reaction

Answer 2

position

Question 3

what are enzymes made of?

Answer 3

mostly proteins - exceptions are some types of RNA - ribozymes are catalysts

Question 4

enzymes can increase the rate of a reaction by a factor of up to __

Answer 4

10^20

Question 5

Enzymes specifically bind and stabilise the ____ ___

Answer 5

transition state

Question 6

what is the transition state?

Answer 6

the reaction intermediate species which has the greatest free energy

Question 7

how do enzymes reduce the activation energy ?

Answer 7

they provide alternative pathways

Question 8

what is glycogen storage disease?

Answer 8

an enzyme deficiency that results in failure of

glycogen to enter transition “phosphorylated” state

Question 9

glycogen storage disease is caused by Defective ____ synthesis/breakdown in muscle, ____ & kidney

Answer 9

Defective glycogen synthesis/breakdown in muscle, liver & kidney

Question 10

what is the most common enzyme to be defective in glycogen storage diseasE>

Answer 10

glucose 6 phosphate

Question 11

what does a defect in glucose 6 phophate cause?

Answer 11

von gierke’s disease

Question 12

what are the symptoms of von gierks (5)

Answer 12

• hypoglycaemia
• skin and mouth ulcers
• hepatomegaly
• bacterial and fungal infection
• bowel inflammation and irritability

Question 13

why do you get hypoglycaemia if you dont have glucose 6 - phosphate

Answer 13

you cannot convert glycogen to glucose

Question 14

what is the treatment for glycogen storage disease?

Answer 14

• slow release glucose meal

- feed little and often

Question 15

why are people with von gierks given corn starch ?

Answer 15

it is hard to metabolise so prevents hypoglycaemia

Question 16

Catalytic activity of many enzymes depends on presence of small molecules, called ____ or____

Answer 16

cofactors or coenzymes.

Question 17

what are cofactors ?

Answer 17

metal ions

Question 18

what are coenzymes?

Answer 18

organic molecules

Question 19

Metal cofactors form a ____ _____ ____ in the enzyme.

Answer 19

metal co-ordination centre

Question 20

what can an enzyme be referred to if it has a metal co-ordination centre?

Answer 20

metalloprotein

Question 21

Coenzymes mostly associate with the enzyme only ____

Answer 21

transiently

Question 22

Coenzymes change ____ or-_____ during the course of the reaction, but are ______.

Answer 22

Coenzymes change charge or structure during the course of the reaction, but are regenerated.

Question 23

what are tightly bound coenzymes caused?

Answer 23

prosthetic groups

Question 24

what is an enzyme without a cofactor called?

Answer 24

apoenzyme

Question 25

what is an enzyme with a cofactor called?

Answer 25

holoenzymes

Question 26

apoenzyme + cofactor =

Answer 26

holoenzymes

Question 27

give ezamples of some cofactors?

Answer 27

metal ions - zinc iron coenzymes

Question 28

metal ions are involved in ____ reactions

Answer 28

redox

Question 29

many coenzymes are derived from ____

Answer 29

vitamins

Question 30

many coenzymes are involved in ___ reactions (NAD, FAD)

Answer 30

redox

Question 31

other coenzymes are involved in group transfer processes, give two examples?

Answer 31

CoA ATP

Question 32

what does CoA transfer?

Answer 32

acetyl groups

Question 33

what does ATP transfer?

Answer 33

phosphate groups

Question 34

symptoms of vitamin deficiencies reflect the loss of specific _____ activities. May be dietary or functional (eg drug or disease-induced deficiencies)

Answer 34

enzyme

Question 35

what is the purpose of amino acids in an active site of an enzymes? 2

Answer 35

- essential for catalytic activity | - for highly specific interactions

Question 36

what are the three pancreatic serine proteases?

Answer 36

- chromotrypsin - trypsin - elastase

Question 37

what is the function of pancreatic serine proteases?

Answer 37

- catalyse the hydrolysis of peptides at specific sites

Question 38

what are the characteristics of the the chymotrypsin active site ?

Answer 38

hydrophobic pocket which binds aromatic amino acids

Question 39

what are the characteristics of the the trypsin active site ?

Answer 39

negatively charged Asp interacts with positively charged Lys or Arg

Question 40

what are the characteristics of the the elastase active site ?

Answer 40

active site partially blocked, only amino acids with small or no side chains can bind

Question 41

Isozymes are _____ (related forms) of enzymes, they catalyse the ___ ____ but have different ___ and ____ (and sequence)

Answer 41

Isozymes are isoforms (related forms) of enzymes, they catalyse the same reaction but have different properties and structure (and sequence)

Question 42

different isozymes can be: - synthesised during different stages of ___ and _____ development - present in different ____ - present in different ____ locations - expressed differently in ___ and ____

Answer 42

- synthesised during different stages of foetal and embryonic development - present in different tissues - present in different cellular locations - expressed differently in health and disease

Question 43

what is an example of a tissue specific isoform?

Answer 43

lactate dehydrogenase

Question 44

lactate dehydrogenase has __ subunits, what are they?

Answer 44

H (heart) and M (muscle)

Question 45

what does the H subunit of lactate dehydrogenase promote?

Answer 45

aerobic metabolism

Question 46

what does the M subunit of lactate dehydrogenase promote?

Answer 46

anaerobic metabolism

Question 47

Relative amounts of isozymes in tissue are useful for _____ purposes

Answer 47

diagnostic

Question 48

lots of the H subunit signifies?

Answer 48

- stroke - heart disease - cancer bascially hypoxia in disease

Question 49

Creatine kinase (CK) is a dimeric protein which binds to the ___ ____

Answer 49

Creatine kinase (CK) is a dimeric protein which binds to the muscle sarcomere

Question 50

the CK - M form is produced in ___ ____ (MM) | and the B form is produced in ____ (BB)

Answer 50

M form is produced in skeletal muscle (MM) | B form is produced in brain (BB)

Question 51

the heart produces ___ type of CK

Answer 51

both

Question 52

appearance of CK - ___ type in blood suggests stroke or tumour

Answer 52

BB

Question 53

appearance of CK - ___ type in blood suggests heart attack

Answer 53

MB

Question 54

side groups of serine, threonine and tyrosine can form ____ esters

Answer 54

phosphate

Question 55

phosphorylation Can convert enzyme to active or inactive form e.g ____ _____

Answer 55

gylcogen phosphorylase

Question 56

what performs phosphorylation reactions?

Answer 56

protein kinases

Question 57

what are zymogens ?

Answer 57

inactive precursors of an enzyme – are irreversibly transformed into active enzymes by cleavage of a covalent bond

Question 58

what are examples of the inactive enzymes in the pancreas pancreas?

Answer 58

trypsinogen and chymotrypsinogen, inactive precursors, are formed

Question 59

what are examples of zymogens in the small intestine?

Answer 59

enteropeptidase cleaves trypsinogen (zymogen) to form active trypsin which cleaves chymotrypsinogen(zymogen) to form active chymotrypsin