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Principles: Biochemistry > Enzymes as Biological Catalysts > Flashcards

Enzymes as Biological Catalysts Flashcards

1
Q

what do enzymes do

A

catalyse reactions that make up metabolism
speeds up rate at which reaction reaches equilibrium
mostly proteins

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2
Q

do enzymes affect the position of equilibrium

A

NO

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3
Q

best conditions for enzymes to work at optimum

A

body temp
aqueous solution
neutral pH

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4
Q

describe enzyme action

A

enzyme specifically binds and stabilises transition state
transition state is reaction intermediate species which has greatest free energy
enzymes reduce activation

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5
Q

how do enzymes speed up reactions

A

lower activation energy

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6
Q

how do enzymes reduce activation energy

A

by providing alternative reaction pathway

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7
Q

what is glycogen storage disease

A

enzyme deficiency that results in failure of glycogen to enter transition ‘phosphorylated’ state

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8
Q

what is glycogen storage diseases caused by

A

defective glycogen synthesis/breakdown in muscle, liver and kidney
11 variants arising from defects in 12 glycogen/glucose metabolising enzymes

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9
Q

symptoms of Von Glerkes Disease

A 
Hypoglycaemia
Hepatomegaly (liver swelling)
Skin/mouth ulcers
Bacterial/fungal infection
Bowel inflammation/irritability
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10
Q

treatment of glycogen storage diseases

A

slow release glucose mean

feed little and often

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11
Q

what are coenzymes/cofactors

A

small molecules upon which catalytic activity is dependant on
cofactors - inorganic metal ions
coenzymes - organic molecules

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12
Q

describe coenzymes

A

mostly associate with enzyme only transient

change charge/structure during reaction but are regenerated

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13
Q

what Is a prosthetic group

A

tightly bound coenzyme eg haem in haemoglobin

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14
Q

what is an enzyme without a cofactor called

A

apoenzyme

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15
Q

what is an enzyme with a cofactor called

A

holoenzyme

apoenzyme + cofactor = holoenzyme

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16
Q

what is a metalloprotein

A

metal cofactor forms metal co-ordination centre in enzyme

17
Q

examples of cofactors

A

metal ions, involved in redox, stabilise transition
coenzymes - derived from vitamins, CoA, NAD/FAD, ATP
vitamins

18
Q

why are vitamin deficiencies caused

A

loss of specific enzyme activity

19
Q

what is NAD

A

coenzyme for redox reactions
may donate/receive electrons during enzyme catalysis
regenerated

20
Q

where do substrates bind

A

active site
cleft/crevice
contains amino acid essential for catalytic activity/highly specific interactions

21
Q

how do substrate bind to enzymes

A

lock and key

induced fit model - active site changes shape complementary fit

22
Q

3 pancreatic serine proteases catalyse hydrolysis of what peptides at specific sites

A

chmotrypsin - hydrophobic
trypsin - negative
elastene - active site partly blocked

23
Q

define isoenzymes

A

isoforms of enzymes

catalyse same reaction but have different properties/structure

24
Q

where are different isozymes found in the body

A

synthesised during foetal/embryonic development

in tissues/cellular locations

25
Q

give an example of of isoymes

A

lactate dehydrogenase

2 subunits - heart promotes aerobic metabolism, muscle promotes anaerobic metabolism

26
Q

what is clinical use of isozymes

A

diagnostic in tissue/blood

27
Q

what is creatine kinase

A

dimeric protein binds to muscle sarcomere
M in skeletal muscle
B in brain
heart produced both types - heterodimer (MB)

28
Q

what does appearance of brain type CK in blood suggest

A

stroke/tumour

29
Q

what does appearance of heart type CK suggest

A

heart attack

30
Q

how are enzymes regulated - reversible

A

phosphorylation - reversible
makes enzyme active/inactive
carried out by kinases

31
Q

how are enzymes modified - irreversible covalent

A

activation of enzymes

zymogens - inactive precursors of an enzyme - irreversibly transformed into active enzyme by cleavage of covalent bond

32
Q

where do zymogens work

A

in pancreas - chymotrypsinogen/trypsinogen
small intestine - enteropepidase cleaves trypsinogen = active trypsin which cleaves chymotrypsinogen forming active chymotrypsin

33
Q

what are irreversible proteolytic

A

enzymes regulated by partial proteolysis eg. digestive enzymes

34
Q

5 general characteristics universal to all enzymes

A 
active site
induced fit model
alternative route to products
substrate specific 
stabilise transition state

Principles: Biochemistry (6 decks)

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