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Pharmacology > Enzymes in Physiology > Flashcards

Enzymes in Physiology Flashcards

1
Q

Define Enzyme

A

Enzymes are protein catalysts that speed up the rate of biochemical reactions without being changed or used up.

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2
Q

Enzymes provide..

A

A reaction surface (active site)

A suitable environment.

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3
Q

What do enzymes actually do?

A

They decrease the activation energy. More molecules meet this energy leading to an increased rate of reaction.

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4
Q

Every chemical energy is accompanied by…

A

a change in free energy, (Gibbs free energy)

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5
Q

Gibbs free energy equation

A

(free energy of initial state) - (free energy of final state)

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6
Q

What is active site?

A

A region within an enzyme that fits the shape of substrate molecules.

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7
Q

How do substrates bind?

A

Amino acid side-chains align to bind the substrate through H-bonding and hydrophobic interactions.

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8
Q

When are products released?

A

When the reaction is complete as they no longer fit well in the active site.

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9
Q

2 Binding Hypothesises:

A

Lock and key (rigid structure)

Induced Fit (more flexible and changes shape upon a drug.)

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10
Q

Enzymes optimum pH

A

7.4

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11
Q

What happens at low or high pH?

A

Activity as lost as tertiary structure is disrupted.

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12
Q

Changing the pH alters.. (3)

A

the ionization state of amino acid side chains

ionic bonding, structural stability, shape and functionality of enzyme

overall 3D structure of all enzymes

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13
Q

Enzymes optimum temperature

A

37 degrees

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14
Q

What are cofactors?

A

Non-organic molecules that bind to the active site and facilitate the reaction by maintaining correct configuration of active site.

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15
Q

Polypeptide proportion of the enzyme is called..

A

Apoenzyme

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16
Q

What are coenzymes?

A

Organic molecules bound to the enzyme by weak interactions or H bonds - many have modified vitamins in their structure and carry electrons.

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17
Q

All enzymes end in …

A

-ase

sucrase
catalyses the hydrolysis of sucrose

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18
Q

Describe Oxido-reductases

A

Catalyse transfer of electrons from donors to acceptors (oxidation and reduction reactions)

19
Q

Oxido-reductases

Dehydrogenases

A

Accept and donate electrons as hydride ions or hydrogen atoms often using cofactors such as NAD+/NADH as an electron donor to acceptor.

20
Q

Describe Transferases

A

Catalyse transfer of a specific functional group between molecules.

21
Q

Transferases

1- What do Kinases do?
2 - What do Aminotransferases do?
3 - Glycosyltransferases?
4 -Acyltransferases?

A

1- kinases - transfer phosphate groups

2 - transfer amino groups

3 - transfer carbohydrate residues

4 - transfer fatty acyl groups

22
Q

Describe Hydrolases

A

Catalyse cleavage of bonds by the addition of a water molecule

23
Q

Hydrolases

1- What do phosphates do?
2 - Lipases?
3 - Peptidases?

A

1 - hydrolyse phosphoric ester bonds

2- hydrolyse ester bonds in lipids

3 - hydrolyse peptide bonds to form 2 products.

24
Q

Describe Lysases

A

Catalyse the addition of water, ammonia or CO2 to double bonds or remove them to create double bonds

25
Q

Lysases

1- Decarboxylases?
2 - Dehydrases?
3- Deaminases?

A

1- remove CO2

2- remove H2O

3 - remove NH3

26
Q

Describe Isomerases

A

Catalyse the interconversion of isomeric forms of a molecule by transferring groups within the same molecule

e. g. Cis and Trans molecules
e. g. D and L isomers

27
Q

Describe Ligases

A

Catalyse the synthesis of new covalent bonds using ATP energy

28
Q

Enzymes may recognise and catalyse…. (3)

A

Absolute - one type of reaction for a single substrate

Group - one type of reaction for similar substrates

Linkage - one of type of reaction for a specific type of bond

29
Q

Example of Absolute catalysis

A

Urease catalyses only hydrolysis of urea

30
Q

Example of Group catalysis

A

Hexokinase adds phosphate groups to hexoses

31
Q

Example of Linkage

A

Trypsin catalyses hydrolysis of peptide bonds

32
Q

Active site conformation drives selectivity

Chymotrypsin prefers…

A

aromatic side chains adjacent to scissile bond

33
Q

Active site conformation drives selectivity

Trypsin prefers…

A

positively charged side chains that can interact with Asp189

34
Q

Active site conformation drives selectivity

Elastase prefers…

A

small uncharged side chains, as pocket is blocked

35
Q

What are isoenzymes?

A

Different forms of an enzyme catalysing same reaction in different tissues.

36
Q

Are there any differences between isoenzymes?

A

Slight variations in quaternary structure - different physical attributes and optimal conditions.

37
Q

Give an example of isoenzymes

A

LDH1 - in heart muscle converts lactate to pyruvate, and then to Acetyl coA

LDH5 - in skeletal muscle converts lactate to pyruvate.

38
Q

Positive allosterism is when…

A

Some effectors speed up enzyme action

39
Q

Negative allosterism is when…

A

Some effectors slow enzyme action.

40
Q

Structure of allosteric enzyme

A

Quaternary structure with two different sites of attachment - the active site and the effector binding sit

41
Q

How does Allosteric regulation of enzyme action work (3)

A

Enzyme complex attaches to the substrate at the active site - releases product.

One product functions as a negative feedback effector by fitting into the effector binding site.

Binding of the effector in the effector binding site causes a conformational shift of the enzyme that closes the active site and inactivates the enzyme.

42
Q

Allosteric enzymes are basis for…

A

feedback inhibition.

43
Q

What happens in feedback inhibition?

A

A product serves as an inhibitor for a previous allosteric enzyme earlier in the series.

Pharmacology (11 decks)

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