Enzymes

Question 1

What are the characteristics of enzymes?

Answer 1

1. Specific
2. Proteins with large molecular weights
3. Labile
4. Catalytic efficiency
5. Does not alter the equilibrium
6. Their activity can be regulated
7. They have an active site

Question 2

What are the two types of ‘substrate specificity’?

Answer 2

1. Abosolute specificity
2. Broad specificity

Question 3

What are the two types of specificity related to enzymes?

Answer 3

1. Substrate specificty
2. Reaction specificity
3. Stereospecificity

Question 4

What are the proteins with large molecular weights with secondary and tertiary structure?

Answer 4

• Simple proteins
• Conjugated proteins
• Protein + co - factor component

Question 5

What is a Holo enzyme?

Answer 5

An Apo-enzyme + non-protein

Question 6

What are the two classification sof enzymes based on thenumber of polypeptide chains?

Answer 6

1. Monomeric - One chain
2. Multimeric - more thna one chain

Question 7

What is a Multienzyme complex?

Answer 7

• Many reaction catalyzing sites in same macro-molecule at different sites
• Becomes inactive when units each with enzyme activity is fractionated.

Question 8

Examples of multienzyme complexes?

Answer 8

Eg: Fatty acid synthetase , Pyruvate dehydrogenase

Question 9

What does it mean to say that an enzyme is “Labile”?

Answer 9

Unstable – enzymes are proteins & are subjected to denaturation by all agents causing denaturation of proteins.

Question 10

What is the catalytic efficiency of enzymes?

Answer 10

Accelerate specific chemical reactions by decreasing activation energy

Question 11

How can the activity fo an enzyme be regulated?

Answer 11

1. Activated
2. Inhibited

Question 12

Describe the role of enzymes in compartmentalization.

Answer 12

Isolate the substrate and products from other competing reactions providing a favourable environment for the reactions or pathways.

Question 13

Describe the active site of an enzyme

Answer 13

Is made up of several amino acids that come together as a result of specific folding of IIry and III ry structure of enzymes
- globular proteins
- hydrophilic side chains on outer parts
- has specific 3D structure, shape & specific charges.
- forms a cleft or pocket on the enzyme surface
that accepts & binds substrate.

Question 14

Importance of active site?

Answer 14

• within the active site the substrates are brought close to one another in optimal alignment with cofactors & prosthetic gps and amino acid side chains responsible for chemical transformation in to products.

•Active site shield substrates from water and generate an environment (polar, acid, hydrophobic or alkaline) that can differ from the surrounding cytoplasm.

Question 15

What are the ‘Mechanisms that facilitate Catalysis’ ?

Answer 15

• Proximity - bond forming distance (conc)
• Acid –base catalysis – prosthetic groups and side chains of amino acids of enz help catalysis by acting as acids and bases etc
• Catalysis by strain - ‘Enz’ that break bonds bind substrates in an unfavourable conformation that will help break the bond
• Covalent catalysis – formation of a covalent bond between ‘Enz’ and a substrate (s). Introduces a new reaction path whose activation energy is lower hence the re becomes faster. Enz modification is transient (temporary)

Question 16

How do enzymes lower the EA?

Answer 16

1. Acting as a template for susbtrate orientation
2. Stressing the susbtrates and stabilizing the transition state
3. Providing a favorable microenvironment
4. Partticipating in the catalytic reaction.

Question 17

Enzymes are classed in to 6 groups depending on reactions catalysed?

Answer 17

1. Oxidoreductase
2. Transferases
3. Hydrolases
4. Lyases
5. Isomerases
6. Ligases

Question 18

Oxidoreductase?q

Answer 18

Oxidize or reduce substrates by transfer of hydrogens, electrons or oxygen

Oxidation & reduction take place in the same reaction

Answer 19

remove groups (not H) from substrates & transfer them to acceptor molecules (not H2O)

ATP + glucose —(hexonkinase)—-> glucose-6-P + ADP

Question 20

Hydrolases?

Answer 20

water participates in the breakage of covalent bonds (C-C, C-N, C-O etc) of substrate with concurrent addition of elements of water to the those bonds.

Ester + H20 —(esterases)—-> acic + alcohol

Question 21

Lyases?

Answer 21

remove atoms/small groups (elimination) from large substrates to leave a double bond (other than hydrolysis or oxidation) or a ring st.

Question 22

Isomerases?

Answer 22

Rearrange functional groups / isomerization of substrate

Glyceraldehede-3-phosphate <—(Triose phosphate/isomerase)—> DHAP (Ketose)

Question 23

Ligases?

Answer 23

Joins 2 molecules

Covalently links 2 molecules with subsequent breakage of a high energy bond.

• forms C-C, C-N, C-O, C-S bonds

ATP + aspartate + NH3 —(Aspartate:NH3 Ligase)—> AMP + pp + asparagine.

Question 24

HI

Answer 24

HI

Question 25

What is covalent modification?

Answer 25

Responds to hormonal regulaation (Eg; Insulin and glucagon) Covalent might help allostery Carries out SIGNAL AMPLIFICATION

Question 26

Examples of Allosteric enzymes?

Answer 26

1. Glycogen synthase - need to get phosphorylated to become active 2. Glycogen phosphorylated

Question 27

Regulation of Glycogen Sythase after a meal?

Answer 27

“Reciprocal regulation” The activity is high Hexokinase [Need to add more points] Activity changes based on glucose levels

Question 28

Action of Glucagon and Insulin on Glycogen Phosphylase based on glucose concentration?

Answer 28

1. Glucagon activates Kinase to phsophorylase

Question 29

What is a signal cascade?

Answer 29

For cells that cannot pass through the plasma membrane and to amplify the signal ligand binds to the gate receptor changes conformation Adenylate Cyclase —-(glucagon)—-> Ad Cyclase ATP -> cAMP activate the protein kinase Enzyme a -> Enzyme b

Question 30

Differenttiate between active and apssive regulation of enzyme activity

Answer 30

Active - Enzyme regulation Passive - Substrate regulation

Question 31

Differentiate between Induction and Repression of enzymes

Answer 31

Regulates the number of active enzymes

Question 32

What are isozymes?

Answer 32

Multiple forms of the same enzyme structure, ionic charge, physical, electrophoreticsal and immunological - all different they catalyse the same reaction Maybe in different organs but catalyse the same reaction [sometimes protein used]

Question 33

isozyme used in clinical diagnmosis?

Question 34

Enzymes for diagnosis?

Answer 34

during disease, enzymes spill into blood enzyme level will be very high idenitify the enzyme to see where and the extent of the tissue damage “Cell Necrosis”

Question 35

isozyme for liver damage?

Answer 35

Alanine aminotransferase

Question 36

creatine kinase as isoenzyme?

Answer 36

creatine phosphate - very high energy molecule increased maount in skeletal muscle, mycardium and brain (All has different isozymes) -> can measure the concentration and help identify which is damaged 2 subunits - M & B -> combinations? 3

Question 37

isozymes of creatine kinase in skeletal muscle, cardiac muscle and brain?

Answer 37

SM - MM (CK3 CK MM) -> will be high in the blood (usually very low) CM - MB (CK MB) -> After heart attack (MI) MB CK level is high -> Trop - I level can be high

Question 38

how to identify the isozymes?

Answer 38

electrophoresis migration of CK? CK 1, CK 2 and CK 3

Question 39

Enzymes used in diagnosis examples. list.

Answer 39

ALT - viral hapatitis Acid phospate - prostate cancer Alkaline phosphate - bone and liver amylase - pnacreatitis, pancreatic cancer LDH, CK - myocardial infarction

Question 40

Myocardial markers

Question 41

eznymes as laboratory agents?

Question 42

Enzymes for therapaeutic use?

Answer 42

Therapy in pancreatic insufficientcy - Amylase, Lipase, Protease Hyaalurodinase - depolymerise ground susbtance [Look into other examples]

Question 43

z