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Principles: biochemistry > Enzymes as Biological Catalysts > Flashcards

Enzymes as Biological Catalysts Flashcards

1
Q

enzymes speed up the rate at which a reaction reaches _____

A

equilibrium

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2
Q

Enzymes DO NOT affect the equilibrium ____ of a reaction

A

position

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3
Q

what are enzymes made of?

A

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

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4
Q

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

A

10^20

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5
Q

Enzymes specifically bind and stabilise the ____ ___

A

transition state

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6
Q

what is the transition state?

A

the reaction intermediate species which has the greatest free energy

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7
Q

how do enzymes reduce the activation energy ?

A

they provide alternative pathways

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8
Q

what is glycogen storage disease?

A

an enzyme deficiency that results in failure of

glycogen to enter transition “phosphorylated” state

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9
Q

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

A

Defective glycogen synthesis/breakdown in muscle, liver & kidney

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10
Q

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

A

glucose 6 phosphate

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11
Q

what does a defect in glucose 6 phophate cause?

A

von gierke’s disease

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12
Q

what are the symptoms of von gierks (5)

A
  • hypoglycaemia
  • skin and mouth ulcers
  • hepatomegaly
  • bacterial and fungal infection
  • bowel inflammation and irritability
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13
Q

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

A

you cannot convert glycogen to glucose

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14
Q

what is the treatment for glycogen storage disease?

A
  • slow release glucose meal

- feed little and often

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15
Q

why are people with von gierks given corn starch ?

A

it is hard to metabolise so prevents hypoglycaemia

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16
Q

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

A

cofactors or coenzymes.

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17
Q

what are cofactors ?

A

metal ions

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18
Q

what are coenzymes?

A

organic molecules

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19
Q

Metal cofactors form a ____ _____ ____ in the enzyme.

A

metal co-ordination centre

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20
Q

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

A

metalloprotein

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21
Q

Coenzymes mostly associate with the enzyme only ____

A

transiently

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22
Q

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

A

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

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23
Q

what are tightly bound coenzymes caused?

A

prosthetic groups

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24
Q

what is an enzyme without a cofactor called?

A

apoenzyme

25
Q

what is an enzyme with a cofactor called?

A

holoenzymes

26
Q

apoenzyme + cofactor =

A

holoenzymes

27
Q

give ezamples of some cofactors?

A

metal ions - zinc iron

coenzymes

28
Q

metal ions are involved in ____ reactions

A

redox

29
Q

many coenzymes are derived from ____

A

vitamins

30
Q

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

A

redox

31
Q

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

A

CoA

ATP

32
Q

what does CoA transfer?

A

acetyl groups

33
Q

what does ATP transfer?

A

phosphate groups

34
Q

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

A

enzyme

35
Q

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

A
  • essential for catalytic activity

- for highly specific interactions

36
Q

what are the three pancreatic serine proteases?

A
  • chromotrypsin
  • trypsin
  • elastase
37
Q

what is the function of pancreatic serine proteases?

A
  • catalyse the hydrolysis of peptides at specific sites
38
Q

what are the characteristics of the the chymotrypsin active site ?

A

hydrophobic pocket which binds aromatic amino acids

39
Q

what are the characteristics of the the trypsin active site ?

A

negatively charged Asp interacts with positively charged Lys or Arg

40
Q

what are the characteristics of the the elastase active site ?

A

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

41
Q

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

A

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

42
Q

different isozymes can be:

  • synthesised during different stages of ___ and _____ development
  • present in different ____
  • present in different ____ locations
  • expressed differently in ___ and ____
A
  • synthesised during different stages of foetal and embryonic development
  • present in different tissues
  • present in different cellular locations
  • expressed differently in health and disease
43
Q

what is an example of a tissue specific isoform?

A

lactate dehydrogenase

44
Q

lactate dehydrogenase has __ subunits, what are they?

A

H (heart) and M (muscle)

45
Q

what does the H subunit of lactate dehydrogenase promote?

A

aerobic metabolism

46
Q

what does the M subunit of lactate dehydrogenase promote?

A

anaerobic metabolism

47
Q

Relative amounts of isozymes in tissue are useful for _____ purposes

A

diagnostic

48
Q

lots of the H subunit signifies?

A
  • stroke
  • heart disease
  • cancer

bascially hypoxia in disease

49
Q

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

A

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

50
Q

the CK - M form is produced in ___ ____ (MM)

and the B form is produced in ____ (BB)

A

M form is produced in skeletal muscle (MM)

B form is produced in brain (BB)

51
Q

the heart produces ___ type of CK

A

both

52
Q

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

A

BB

53
Q

appearance of CK - ___ type in blood suggests heart attack

A

MB

54
Q

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

A

phosphate

55
Q

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

A

gylcogen phosphorylase

56
Q

what performs phosphorylation reactions?

A

protein kinases

57
Q

what are zymogens ?

A

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

58
Q

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

A

trypsinogen and chymotrypsinogen, inactive precursors, are formed

59
Q

what are examples of zymogens in the small intestine?

A

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

Principles: biochemistry (7 decks)

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