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ESA 1 Revision > MGD Session 3 > Flashcards

MGD Session 3 Flashcards

1
Q

What are the 2 categories of short term enzyme regulation?

A
  1. Substrate and product concentration

2. Change in enzyme conformation

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2
Q

What are the 3 kinds of enzyme regulation by changing enzyme conformation?

A
  1. Allosteric regulation
  2. Covalent modification
  3. Proteolytic cleavage
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3
Q

How do substrate and product concentrations affect enzyme regulation?

A

Substrate availability affects rate of enzyme activity. Accumulation of the product of a reaction inhibits the forwards reaction.

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4
Q

What is an isoenzyme?

A

Different forms of the same enzyme that have different kinetic properties

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5
Q

What is meant by allosteric control?

A

When the binding of a substrate to one active site (of an enzyme with multiple subunits) enhances substrate binding to the other active sites.

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6
Q

Give two examples of allosteric control.

A

Haemoglobin T and R states.

Phosphofructokinase is allosterically controlled.

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7
Q

What is an allosteric inhibitor?

A

A molecule that binds and decreases enzyme activity, shifting the curve to the right.

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8
Q

What is an allosteric activator?

A

A molecule that binds to the enzyme increasing the activity and shifting the curve to the left.

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9
Q

Briefly describe how allosteric control works in haemoglobin - referring to activators and inhibitors.

A

An allosteric inhibitor shifts the R to T conformational equilibrium twoard T whereas an allosteric activator shifts it towards the R state.

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10
Q

What are the allosteric activators (2) and inhibitors (3) of phosphofructokinase?

A

Activators: AMP, fructose-2,6-bisphosphate

Inhibitors, ATP, Citrate, H+

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11
Q

What is the main type of covalent modification that occurs?

A

Phosphorylation

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12
Q

What kind of enzymes add phosphates to protein?

A

Protein kinases

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13
Q

What kind of enzymes remove phosphates from protein?

A

Protein phosphatases

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14
Q

Onto which group of an amino acid does a kinase add a phosphate group? Which amino acids can they be added to? (name 3)

A

Phosphates are added onto the OH group of the amino acids Serine, Threonine or Tyrosine.

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15
Q

What is meant by proteolytic activation?

A

Enzymes are secreted as a zymogen and are then activated by proteolytic cleavage.

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16
Q

What is a zymogen?

A

An inactive protein precursor.

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17
Q

How does change in the amount of enzyme alter enzyme activity?

A
  • Regulation of enzyme synthesis
  • Regulated protein degradation (addition of ubiquitin)
  • Regulation of metabolic pathways
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18
Q

What is feedback inhibition?

A

When the end product of a pathway inhibits its own rate of synthesis

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19
Q

What is feedforward activation?

A

When increased amounts of inital substrate increases the first step in the pathway

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20
Q

What is meant by counter regulation of pathways?

A

If a catabolic pathway is activated, the opposing anabolic pathway will be inactivated

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21
Q

How does amplification by enzyme cascades work?

A

When an enzyme activates another enzyme, the number of affected molecules increases geometrically in an enzyme cascade.

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22
Q

List the inactive precursors of the following enzymes:

a) Pepsin
b) Chymotrypsin
c) Trypsin
d) Carboxypeptidase
e) Elastase

A

a) Pepsinogen
b) Chymotrypsinogen
c) Trypsinogen
d) Procarboxypeptidase
e) Proelastase

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23
Q

Name the four zymogens (and their active proteins) that trypsin cleaves.

A

Chymotrypsinogen (Chymotrypsin)
Proelastase (Elastase)
Procarboxypeptidase (Carboxypeptidase)
Prolipase (Lipase)

24
Q

Which enzyme cleaves Trypsinogen to Trypsin?

A

Enteropeptidase

25
Q

How does a deficiency of antitrypsin cause emphysema?

A

Lack of antitrypsin allows trypsin to cleave proelastase to elastase. This means the elastase works on the elastin in the walls of the alveoli and so they fail to stretch.

26
Q

What are the two pathways that contribute to the blood clotting cascade contribute to?

A

Intrinsic pathway and Extrinsic pathway

27
Q

What does the intrinsic pathway do?

A

Damaged membrane of the blood cells promotes the binding of Factor XI, which in turn promotes activation of Factor IX. Cofactor VIII and Factor IX enable the activation of Factor X (along with the extrinsic pathway)

28
Q

What does the extrinsic pathway do?

A

Trauma releases tissue factor (Factor III). This (along with the intrinsic pathway) activates Factor X.

29
Q

Explain the blood clotting cascade following the activation of Factor X.

A

Factor X activation causes activation of thrombin from prothrombin which, in turn, causes the activation of fibrinogen to fibrin.

30
Q

Explain the role of y-carboxyglutamate (Gla) residues.

A

Post translational modification of factors 2, 7, 9 and 10 in the liver adds COOH groups to the glutamate residues to form carboxyglutamate (Gla). This allows interaction with the sites of damage and brings together clotting factors. Without Gla residues, clots will not form as clotting factors are not brought to the site.

31
Q

What is haemophilia A?

A

A defect in factor VIII.

32
Q

How does positive feedback play a role in the blood clotting cascade?

A

The activation of thrombin promotes further activation in the cascade (Factors V, VIII and XI)

33
Q

What is fibrinolysis?

A

The breakdown of the clot.

34
Q

How does fibrinolysis take place?

A

T-Pa (Tissue plasminogen activator) and Streptokinase cause the activation of plasminogen to plasmin, which breaks down fibrin into fibrin fragments.

35
Q

How is the clotting process stopped?

A

Dilution of clotting factors by blood flow
Removal of clotting factors by the liver
Digestion of clotting factors by proteases (protein C)
Specific Inhibitors prevent continual clotting.

36
Q

How is clotting localised?

A

Gla-residue factors bind to damaged endothelial cell lining and allow rapid activation of effector molecules.

37
Q

What is the difference between heterochromatin and euchromatin?

A

Heterochromatin is non-expressed, densely packed DNA and shows up dark on a micrograph. It is in the solenoid fibre form. Euchromatin is the expressed DNA, it is less tightly bound and shows up as a lighter colour on a micrograph. It is in the beads on a string form.

38
Q

How is DNA packaged?

A

DNA wound around histones (beads on a string)
Beads on a string packaged into a solenoid
Solenoids loop and are packaged into chromosomes.

39
Q

How many pairs of chromosomes do humans have?

A

23

40
Q

What is the size of a solenoid fibre?

A

30nm

41
Q

On which chromosome is the Sickle Cell Anaemia mutation?

A

11

42
Q

On which chromosome is the Cystic Fibrosis mutation?

A

7

43
Q

What are the two types of nitrogenous bases? Describe the differences.

A

Purines (G and A) have a 2 ring structure.

Pyrimidines (C, T and U) have a 1 ring structure.

44
Q

Which base pairs do we find in DNA?

A

G pairs with C

A pairs with T

45
Q

What is the difference in strand numbers between DNA and RNA?

A

DNA is double stranded

RNA is single stranded.

46
Q

What comprises a nucleotide?

A

A nitrogenous base, a sugar and a phosphate.

47
Q

How are nucleotides linked together?

A

Phosphodiester bonds between the phosphate of one nucleotide and the sugar of the next nucleotide.

48
Q

What is the difference in the DNA sugars and RNA sugars?

A

DNA has 2-deoxyribose sugar
RNA has ribose sugar.
The 2nd carbon in the sugar has 2 H groups in RNA and 1 H group, 1 OH group in DNA.

49
Q

What are the two ends of a polynucleotide categorised as?

A

5’ and 3’

5’ starts with phosphate group and 3’ ends with free -OH

50
Q

What is a nucleoside?

A

A nucleotide without a phosphate group.

51
Q

What nucleoside forms from an Adenine base in RNA?

A

Adenosine

52
Q

What nucleoside forms from a Guanine base in DNA?

A

Deoxyguanosine

53
Q

What nucleotide forms from a Uracil base in RNA?

A

Uridine monophosphate

54
Q

What nucleotide forms from a Cytosine base in DNA?

A

Deoxycytidine

55
Q

What does ‘antiparallel’ suggest about DNA structure?

A

One DNA strand runs 5’ - 3’ (left to right)

The other strand runs 3’ - 5’ (left to right)

56
Q

What are RNA stem loops?

A

When RNA folds back on itself and forms hydrogen bonds due to complimentary bases.

57
Q

List the key properties of the DNA double helix.

A

Two polymers complimentary and antiparallel to eachother.
One turn has 10 base pairs
Space between base pairs is 0.34nm,
Purines and pyrimidines are planar and unsaturated.
Major and minor grooves exist in the sugar-phosphate backbone

ESA 1 Revision (14 decks)

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