Enzymes Flashcards Preview

Food Chemistry 2 > Enzymes > Flashcards

Flashcards in Enzymes Deck (100)
Loading flashcards...
1

What are functions of enzymes?

-reduces activation energy
-enables biological rections to proceed at faster rates

2

properties of enzymes?

-enzymes can be hydrolyzed by dilute acids or alkali to form free AA or low molecular weight peptides
-E can be broken down by proteases to form AA or peptides with participation of H2O
-E can respond to typical common protein tests (ie. ninhydrin and lowry)
-E is comprised of AA linked together by peptide bonds

3

what can hydrolyze enzymes?

what do they form?

dilute acids or alkali; or peptides

forms free AA or low molecular weight peptides

4

what links AAs together?

peptide bonds

5

sizes of collagen, myosin, trypsin, amylose?

collage: 100-400kDa
myosin: 200kDa
trypsin: 20kDa
amylose: 40-50kDa

6

def of proenzyme?

immature and inactive enzyme

7

def of holoenzyme?

complete enzyme that is active

it is bound to its cofactor

8

def of apoenzyme?

enzyme that requires a cofactor

it is inactive

becomes active when it is bound to a cofactor

9

def of a prosthetic group?

the non-protein part that forms a part of a protein

10

examples of prosthetic groups?

metal ions: Ca, Fe, Zn

11

relationship between holoenzyme and prosthetic group?

-sometimes, the holoenzyme is the whole protein

-other times, the holoenzyme needs the essential non-protein part for the protein to be active (ie. the prosthetic group)

12

what are features of the enzyme active site? (3)

small
3D
clefts/crevices

13

what are 2 events that occur at the active site?

binding and transformation

14

Relationship between binding and transformation?

-binding of substrate preceeds transformation
-not all binding leads to transformation
-no transformation occurs without binding

15

4 levels of enzyme specificity?

1. bond specificity
2. group specificity
3. absolute specificity
4. sterospecificity

16

how are enzymes bond specific?

-E acts on compounds with one type of bond (ie. lipase can act on lipids as long as they have an ester bond)
-can have relative or low specificity

17

How are enzymes group specific?

when an enzyme acts on a group of closely related compounds
-ie. pepsin can hydrolyze peptide bonds where there is are aromatic AAs
-ie trypsin can hydrolyze peptide bonds where there are basic AA
-moderate specificity

18

how are enzymes absolutely specific?

when enzyme acts on one single substrate
-ie lactase only acts on lactose. Sucrase only acts on sucrose
-very high specificity

19

how are enzymes sterospecific?

when enzyme acts on one isomer of a molecule
-ie L-AA oxidase acts only on L-AA

20

why is it necessary to understand specificity in a baking company?

-linear starch has alpha(1-4) bonds.
-branched starch has alpha (1-6) bonds
-linear starch is stickier than branched starch

21

how many enzyme classifications are there? what are these classifications based on?

6 classifications

based on recommendation of enzyme commission of the international union of biochemists

also based on types of reaction catalyzed

22

what is the numbering system that enzyme nomenclature

enzyme commission = EC

EC = (A.B.C.D) --> letters are digits

A = 1st group
B = sub group
C = sub sub group
D = numbering

23

what are the 6 enzyme classifications?

1. oxidoreductase
2. transferase
3. hydrolyse
4. lyases
5. isomerases
6. ligases

24

what are oxidoreductases?

can catalyze oxidation or reduction reactions

ie. polyphenol oxidase (PPO), glycose odidase (GOX), peroxidase, lipoxygenase

25

what are transferases

transfers groups from one substrate (the donor) to another substrate (Acceptor)

eg. transglutaminase

26

what are hydrolyases

catalyzes cleavage or hydrolysis of larger molecules into smaller molecules with H2O as a co-reactant

eg. proteases and lipases

27

what are lyases

removes group from one molecule, leaving behind a product with a lower molecular weight (usually with unsaturated bonds)

eg. histidine decarboxylase, pectin, lyase

28

what are isomerases

catalyzes the conversion of molecules into their isomers

eg. glucose isomerase

29

what are racemases and epimerases?

isomerase enzymes that catalyzes the inversion of stereochemistry

racemases: catalyzes sterochemical inversion around the asymmetric carbon atom (in a substrate has only one center of asymmetry)

epimerases: catalyzes sterochemical inversion of the configuration around an asymmetric carbon (in a substrate with more than one center of assymmetry)

30

what are ligases

catalyzes the joining together of two or more molecules

eg. fatty acyl CoA synthase