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FLC > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Which functions are carried out by enzymes?

A
  • Digestion
  • Blood Clotting
  • Defence / Immune system activation of complement
  • Movement
  • Nerve Conduction
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2
Q

Where are enzymes located/found in the body?

A
  • Intracellularly

- Secreted extracellularly

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3
Q

What are the consequences of enzyme defects?

A

Defects in enzymes cause disease

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4
Q

Is the formation of an enzyme-substrate complex an active or passive process?

A

Active process - requires energy

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5
Q

Give an example of an antibiotic

A

Penicillin

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6
Q

Which enzyme catalyses movement in the body?

A

ATPase catalyses the muscle actomyosin contraction mechanism

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7
Q

Name a few examples of types of enzymes found in the body

A
  • Proteases
  • Nucleases
  • Kinases
  • Polymerases
  • Synthases
    etc.
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8
Q

Explain how the antibiotic Penicillin works

A

Inhibits cell wall synthesis in bacteria causing it to burst

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9
Q

How are enzymes useful in drug use?

A

Enzymes can be used as drug targets

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10
Q

What compounds do enzymes aid digestion of?

A

Carbohydrates, Proteins and fats

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11
Q

In what ways can we alter factors to make catalysis easier?

A
  • Constrain substrate movement
  • Stabilise +ve and -ve (transition state)
  • Provide a lower Ea route
  • Strain certain bonds => breakage easier
  • Use co factors
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12
Q

What is the consequence of Phenylketonuria to patients?

A

Results in decreased metabolism of the amino acid phenylalanine to Tyrosine due to inheriting defected
phenylhydroxylase enzyme
- lots of phenylalanine -> converted into toxic by products
- affect brain maturation

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13
Q

Explain what is meant by the Induced Fit Model

A

Active site alters it shape to become complementary to its substrate

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14
Q

What is the basic reaction path of substrate binding?

A

E + S <=> ES => EP => E + P

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15
Q

How does compartmentation regulate enzymes in the cell?

A

Each enzyme has a short amino acid sequence that is a targeting signal telling organelles whether it can enter the cell or not

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16
Q

Give 3 examples of diseases caused by enzyme defects

A
  1. Phenylketonuria -
  2. GSD (Glycogen storage disease) -
  3. Tay-sachs Disease -
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17
Q

Give an example of an anti-inflammatory agent

A

Aspirin

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18
Q

Explain what Tay Sachs disease is

A

Absence of hexosaminidase-A (Hex-A) enzyme causes GM2 ganglioside (lipid) to accumulate
abnormally in cells, especially causing progressive damage to nerve cells in brain
- patients unable to form membrane lipid cerebreside (significant to brain)”

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19
Q

Why does enzyme activity eventually plateau?

A

There is a limit to the number of substrates a single enzyme can bind to in a given time

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20
Q

How can enzyme active sites be observed?

A

Xray Crystallography

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21
Q

Explain how the drug aspirin works as an anti inflammatory agent

A

Inflammation caused by cyclooxygenases and messenger prostaglandin molecule
Aspirin blocks prostaglandin production and cyclooxygenases

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22
Q

What is compartmentation?

A

The concentrating and separating of enzymes and metabolites within organelles

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23
Q

What is the consequence of covalent modifications of enzymes?

A

Change the enzyme shape and therefore its functional activity

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24
Q

What is Vmax?

A

Maximum velocity (rate) at which the enzyme catalyses a reaction. Occurs when all enzyme active sites are saturated with substrates

25
Q

How is enzyme activity regulated in the body?

A
  • Compartmentation
  • Covalent Modification
  • Allosteric regulation
26
Q

What is allosteric regulation?

A

Regulation of an enzyme by binding an effector molecule at a site other than the enzyme’s active site

27
Q

How can Vmax and Km be used to determine reaction rate?

A

Rate of reaction = 1/Vmax + km/Vmax

28
Q

How can we increase reaction rate?

A

Increase substrate concentration

29
Q

What is a GSD (glycogen storage disease)?

A

Metabolic disorder caused by enzyme deficiencies affecting glycogen synthesis / breakdown or glycolysis

30
Q

Give an example of an enzyme that causes blood clotting

A

Thrombin catalyses the formation of fibrin clots

31
Q

Give an example of a common enzyme covalent modification?

A

De/Phosphorylation of enzymes

32
Q

What is an active site?

A

3D celft/cavity that binds substrates using electrostatic, hydrophobic, hydrogen bonding and Van der Waals interactions

33
Q

How is phenylketonuria treated?

A

Patients consume a low phenylalanine diet

34
Q

List some properties of allosteric enzymes

A
  • Multi sub unit complexes
  • Regulatory and catalytic sites on different sub units
  • involved in feedback inhibition of metabolic pathways
35
Q

What is Vmax dependent on?

A

The rate at which an enzyme can process a substrate molecule

36
Q

What is an enzyme?

A

Proteins that are biological catalysts which speed up the rate of reaction
by providing an alternative reaction route with a lower activation energy

37
Q

Give an example of an anticancer drug

A

Methotrexate

38
Q

Which enzymes are involved in nerve conduction?

A

Membrane ion pumps for sodium and calcium ions

39
Q

What is Km?

A

Michaelis Constant

The concentration of substrate when enzyme reaches 1/2Vmax

40
Q

How are enzymes categorised?

A

Enzymes are categorised by the type of reaction they catalyse

41
Q

Explain how anticancer drug Methotrexate works

A

Methotrexate is a Folate analogue (inhibits Folate action)
Folic acid significant in DNA/RNA synthesis
Methotrexate blocks enzymes using Folate as co factor - inhibiting DNA synthesis

42
Q

List some functional properties of enzymes

A
  • Increase reaction rate (>10bn fold)
  • Specific to substrates
  • Remain unchanged during reactions
  • Doesn’t alter reaction equilibrium (catalyses reaction in forwards and backwards direction)
  • Decreases activation energy
43
Q

What is a medicinal use of proteases?

A

Therapeutic drug targets

44
Q

Why is an acylenzyme able to form from chymotrypsin?

A

Chymotrypsin has a very reactive serine which attacks the peptide to form the acyl protein product

45
Q

What is the function of proteases?

A

Hydrolyse peptides by selectively cleaving particular peptide bonds

46
Q

What makes the chymotrypsin serine so reactive?

A

The serine has a catalytic triad that makes the OH group increase in electronegativity - therefore is very reactive

47
Q

How stable are the proteins present in our bodies?

A

They are chemically stable but not thermodynamically stable

48
Q

What is a catalytic triad?

A

Group of 3 amino acids found in active sites fo certain proteases involved in catalysis

49
Q

How do serine proteases identify which bond to cleave?

A

Serine proteases have a high specificity for the peptide bond they hydrolyse

50
Q

Name some common proteases

A
  • serine
  • cysteine
  • aspartyl
  • metalloproteinases
51
Q

Outline how the acyl Enzyme intermediate is formed during peptide bond cleavage

A
  1. Catalytic triad and electronegativity converts OH into very -ve charge
  2. O interferes with C-N (peptide) bond
  3. Ester intermediate formed (acyl enzyme)
  4. Water hydrolyses the intermediate
  5. Peptide bond is cleaved
52
Q

Explain what is meant by the hydrophobic pocket?

A

A binding site containing mainly hydrophobic amino acids

e.g. binding site for aromatic side chains in chymotrypsin substrates

53
Q

Which peptide bonds does Trypsin specifically hydrolyse?

A

“Has specificity for peptide bonds on Arginine and Lysine (+ve charged)
- forms electrostatic attractions to -ve pocket

54
Q

Which substrates does the elastase cleave?

A

Only cleaves small substrates as the pocket is small - only small residues are able to fit

55
Q

How is the 3D structure of proteins conserved by Serine proteases?

A

With a charge relay system

56
Q

Where is the protein Elastase found in the body?

A

In the lungs

57
Q

Where is Trypsin proteins found?

A

In the liver

58
Q

Which is chymotrypsin’s area of specificity?

A

Chymotrypsin cleaves aromatic residues due to hydrophobic pocket:

  • Phenylalanine
  • Tryptophan
  • Tyrosine
59
Q

What is the role of ATP synthase enzyme?

A

Forms ATP by converting energy from H+ by moving them down their diffusion gradient in chemiosmosis
Proton current rotates synthase to form ATP

FLC (34 decks)

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