Enzymes as Biological Catalysts

Question 1

what do enzymes do

Answer 1

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

Question 2

do enzymes affect the position of equilibrium

Answer 2

NO

Question 3

best conditions for enzymes to work at optimum

Answer 3

body temp
aqueous solution
neutral pH

Question 4

describe enzyme action

Answer 4

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

Question 5

how do enzymes speed up reactions

Answer 5

lower activation energy

Question 6

how do enzymes reduce activation energy

Answer 6

by providing alternative reaction pathway

Question 7

what is glycogen storage disease

Answer 7

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

Question 8

what is glycogen storage diseases caused by

Answer 8

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

Question 9

symptoms of Von Glerkes Disease

Answer 9

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

Question 10

treatment of glycogen storage diseases

Answer 10

slow release glucose mean

feed little and often

Question 11

what are coenzymes/cofactors

Answer 11

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

Question 12

describe coenzymes

Answer 12

mostly associate with enzyme only transient

change charge/structure during reaction but are regenerated

Question 13

what Is a prosthetic group

Answer 13

tightly bound coenzyme eg haem in haemoglobin

Question 14

what is an enzyme without a cofactor called

Answer 14

apoenzyme

Question 15

what is an enzyme with a cofactor called

Answer 15

holoenzyme

apoenzyme + cofactor = holoenzyme

Question 16

what is a metalloprotein

Answer 16

metal cofactor forms metal co-ordination centre in enzyme

Question 17

examples of cofactors

Answer 17

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

Question 18

why are vitamin deficiencies caused

Answer 18

loss of specific enzyme activity

Question 19

what is NAD

Answer 19

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

Question 20

where do substrates bind

Answer 20

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

Question 21

how do substrate bind to enzymes

Answer 21

lock and key

induced fit model - active site changes shape complementary fit

Question 22

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

Answer 22

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

Question 23

define isoenzymes

Answer 23

isoforms of enzymes

catalyse same reaction but have different properties/structure

Question 24

where are different isozymes found in the body

Answer 24

synthesised during foetal/embryonic development

in tissues/cellular locations

Question 25

give an example of of isoymes

Answer 25

lactate dehydrogenase | 2 subunits - heart promotes aerobic metabolism, muscle promotes anaerobic metabolism

Question 26

what is clinical use of isozymes

Answer 26

diagnostic in tissue/blood

Question 27

what is creatine kinase

Answer 27

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

Question 28

what does appearance of brain type CK in blood suggest

Answer 28

stroke/tumour

Question 29

what does appearance of heart type CK suggest

Answer 29

heart attack

Question 30

how are enzymes regulated - reversible

Answer 30

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

Question 31

how are enzymes modified - irreversible covalent

Answer 31

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

Question 32

where do zymogens work

Answer 32

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

Question 33

what are irreversible proteolytic

Answer 33

enzymes regulated by partial proteolysis eg. digestive enzymes

Question 34

5 general characteristics universal to all enzymes

Answer 34

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