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MGD > Session 3 > Flashcards

Session 3 Flashcards

0
Q

What are isoenzymes?

A
  • Have different amino acid sequences but catalysed the same reaction
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1
Q

What types of short-term and long-term regulation of enzymes are there?

A
  • Short-term: substrate and product concentration; change in enzyme conformation (Allosterically regulation, covalent modification, proteolytic cleavage)
  • Long-term: change in rate of protein synthesis; change in rate of protein degradation
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2
Q

How does substrate concentration affect the rate of reaction?

A
  • High concentration increases forward rate of reaction
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3
Q

How does product concentration affect the rate of reaction?

A
  • High concentration of product inhibits the forward reaction
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4
Q

What type of curve do allosteric enzymes show and why?

A
  • Sigmoidal

- In multi-subunit enzymes, substrate binding becomes subsequently easier

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5
Q

What do allosteric activators do?

A
  • Increase the proportion of the enzyme in the R state
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6
Q

What do allosteric inhibitors do?

A
  • Increase the proportion of enzyme in the T state
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7
Q

How is phosphofructokinase regulated?

A
  • Allosterically regulated
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8
Q

Why is the regulation of phosphofructokinase important?

A
  • Sets the pace of glycolysis
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9
Q

What activates phosphofructokinase?

A
  • AMP

- Fructose-2,6-bisphosphate

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10
Q

What inhibits phosphofructokinase?

A
  • ATP
  • Citrate
  • H+
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11
Q

Give 2 examples of covalent modification

A
  • Phosphorylation (+ATP)

- Acetylation (+Acetyl CoA)

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12
Q

What type of enzymes add a phosphate group to proteins?

A
  • Kinases
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13
Q

What type of enzymes remove a phosphate group from proteins?

A
  • Phosphatases
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14
Q

How do kinase enzymes work?

A
  • A phosphate group is removed from ATP which is transferred to the -OH group of Serine, Threonine or Tyrosine
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15
Q

How do phosphatase enzymes work?

A
  • Remove phosphate groups by hydrolysis
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16
Q

Why do phosphate groups affect enzyme activity?

A
  • Bulky, charged groups that significantly affect enzyme conformation and substrate binding
17
Q

What is amplification?

A
  • one enzyme activates other enzymes, which activates others,which means one signal is amplified very quickly - has a larger effect
18
Q

What is proteolytic cleavage?

A
  • enzymes secreted as zymogens (inactive protein precursors) and are cleaved by proteases to give the active enzyme
19
Q

Give examples of digestive enzymes that undergo proteolytic cleavage

A
  • Stomach: zymogen = pepsinogen, active enzyme = pepsin
  • Pancreas: zymogen = chymotrypsinogen, active enzyme = chymotrypsin
  • Pancreas: zymogen = trypsinogen, active enzyme = trypsin
  • Pancreas: zymogen = procarboxypeptidase, active enzyme = carboxypeptidase
  • Pancreas: zymogen = proelastase, active enzyme = elastase
20
Q

Give examples of when proteolytic cleavage is used

A
  • Digestive enzymes
  • Protein hormones
  • Blood clotting
  • Developmental processes
  • Apotosis
21
Q

What is the overview of the blood clotting cascade?

A

Intrinsic pathway: Extrinsic pathway:
Damaged endothelial lining of Trauma releases tissue factor
Blood cells promotes binding (Factor III)
Of factor XII ⬇️ ⬇️
Factor X activation (common endpoint)
⬇️
Thrombin activation
⬇️
Formation of fibrin clot

22
Q

What is good about the clot formation using a cascade?

A
  • Allows formation of a clot from very small amount of initial factor
23
Q

What type of feedback does thrombin do?

A
  • Positive feedback
24
Q

What forms does DNA take in the nucleus and what does it look like under an electron microscope?

A
  • Euchromatin: appears light (‘beads on a string’ - Nucleosomes not coiled) Genes are expressed
  • Heterochromatin: appears dark (solenoid - Nucleosomes tightly packed) Genes are not expressed
25
Q

What is a nucleosome?

A
  • A positive histone protein with negatively charged DNA wrapped around it
  • Also called ‘beads on a string’
26
Q

What is a solenoid?

A
  • Nucleosomes tightly coiled together
27
Q

What is a nucleoside?

A
  • Base and sugar
28
Q

What is a nucleotide?

A
  • Base, sugar and phosphate
29
Q

What are the differences between DNA and RNA?

A
  • DNA: deoxyribose sugar, has 2 -H groups on the 2nd carbon

- RNA: ribose sugar, has a -H group and an -OH group on the 2nd carbon

30
Q

Which carbons of the sugar are the phosphate group and nitrogenous base joined to in a nucleotide?

A
  • Carbon 1: nitrogenous base

- Carbon 5: phosphate group

31
Q

How does a phosphate group join to the sugar in a nucleotide and what makes it special?

A
  • Phosphate ester link

- Has 2 negative oxygens, makes nucleotide negative

32
Q

What types of nitrogenous bases are there and how are they different?

A
  • Purine: 2 rings

- Pyrimidine: 1 ring

33
Q

What bases are purines?

A
  • Adenine

- Guanine

34
Q

What bases are pyrimidines?

A
  • Cytosine
  • Thymine
  • Uracil
35
Q

How are nucleotides joined?

A
  • Phosphodiester bonds

- The phosphate group on carbon 5 forms a bond to the -OH group on carbon 3 of the adjacent nucleotide

36
Q

Explain 5’ to 3’

A
  • DNA/RNA chain has polarity

- There are distinct ends: the 5’ end has an unbound phosphate group and a 3’ end has an unbound -OH group

37
Q

How are Guanine and Cytosine bases paired?

A
  • 3 hydrogen bonds between the bases
38
Q

How are Adenine and thymine bases paired?

A
  • 2 Hydrogen bonds between the bases
39
Q

How is tRNA formed?

A
  • RNA stem loops: hydrogen bonds form between antiparallel complementary sequences in the same RNA strand

MGD (9 decks)

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