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MD2001 > Biological Molecules > Flashcards

Biological Molecules Flashcards

1
Q

What is a hypertonic solution?

A

A solution with a higher concentration of solutes outside the cell than within it. This leads to cremation of cells such as RBCs.

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2
Q

What is a hypotonic solution?

A

A solution with a lower concentration of solutions outside the cell than within it. This leads to lysis of cell as the cells get swollen and eventually ruptured.

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3
Q

What is stronger covalent or ionic bond?

A

Covalent bond.

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4
Q

What are the three types of intramolecular bonds?

A
  1. Ionic
  2. Covalent
  3. Metallic
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5
Q

What are the different types of intermolecular forces?

A
  1. London forces
  2. Dipole-dipole forces.
  3. Hydrogen bonds.
  4. Ionic
  5. Covalent
  6. Metallic
    Note: hydrophilic and hydrophobic interactions.
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6
Q

What is an oligosaccharide?

A

A carbohydrate with a relatively small number of monomers.

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7
Q

How are fatty acids stored?

A

Triacyl glycerol.

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8
Q

What are phospholipid molecules comprised of?

A
  1. A hydrophilic head (phosphate group and glycerol).

2. Two hydrophobic fatty acid tails.

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9
Q

What is the chemical composition of steroids?

A

4 fused carbon rings with functional groups attached.

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10
Q

Name two common types of steroids?

A
  1. Cholesterol

2. Testosterone.

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11
Q

Uses of amino acids?

A
  1. Sources of energy.
  2. Neurotransmitters e.g. glutamine.
  3. Precursors for other molecules e.g. glycine precursor for porphyrin ring.
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12
Q

How does the energy of each phosphate on DNA differ?

A

Removal of the first phosphate releases the most amount of energy. The energy released is then reduced for the other two phosphate molecules.

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13
Q

Uses of nucleotides?

A
  1. Short term energy source i.e. ATP and GTP.
  2. Store of electrons i.e. NAD, NADP.
  3. Cofactors for enzymes i.e. coenzyme A.
  4. Signalling molecules i.e. cAMP.
  5. Building blocks for nucleic acids i.e. DNA/RNA.
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14
Q

What are the different blood types and how is this due to biological molecules?

A
  1. O,A,B,AB.
  2. On surface of RBCs, one has different sugars.
  3. Type A has an extra sugar added on.
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15
Q

What are viruses coated with?

A

Glycoproteins.

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16
Q

What does a monosaccharide consist of?

A
  1. 3-6 Carbon atoms.
  2. A carbonyl group.
  3. Several hydroxyl groups.
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17
Q

How are L and D assigned to carbohydrates?

A

The -OH group on the chiral carbon furthest away form the carbonyl group determines if L or D isomer.

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18
Q

What is the correct name for the aldohexose which is more commonly known as blood sugar?

A

D-glucose.

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19
Q

What is the difference between D-glucose and D-galactose?

A
  1. On 4th carbon atom the -OH group is on difference sides.

2. On D-glucose it is on the right hand side.

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20
Q

What is galactosemia?

A
  1. When one lacks the enzymes to required for galactose metabolism into glucose.
  2. Toxic effects in liver, kidney, brain and eyes.
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21
Q

What happens in the formation of cyclic monosaccharides?

A
  1. Hydroxyl group on C-5 reacts with carbonyl group.
  2. Place C6 above the ring.
  3. Put -OH groups below ring in C2 and C4.
  4. Put -OH group above ring in C3.
  5. Write a new -OH on C1 either down for alpha or up for beta.
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22
Q

What happens when alpha and beta D-glucose are placed in solution?

A
  1. Cyclic structures will open and close.

2. Converted into opposites.

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23
Q

What is the simplest sugar?

A

D-glyceraldehyde.

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24
Q

Name three tests for glucose.

A
  1. Fehling’s reagent (forms D-gluconate).
  2. Glucose oxidase test.
  3. Concentration of HBA1c.
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25
Q

What is lactose formed from?

A
  1. Beta-D-galactose.

2. Alpha or beta-D-glucose.

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26
Q

What happens in lactose intolerance?

A
  1. Lack of lactase.
  2. Lactose passes into colon and bacteria ferment lactose.
  3. Leads to stomach cramps, bloating, flatulence.
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27
Q

How often does amylopectin branch?

A

1 every 30 glucose molecules.

28
Q

What are the functions of proteins?

A
  1. Provide structure e.g. collagen.
  2. Transport molecules e.g. haemoglobin transports O2, LDL transports cholesterol.
  3. Antibodies.
  4. Enzymes
  5. Regulation of genes e.g. lac Repressor.
29
Q

What are the basic amino acids?

A

BLAH

  1. Lysine.
  2. Arginine.
  3. Histidine
30
Q

What are the acidic amino acids?

A

AAG

  1. Aspartate.
  2. Glutamate
31
Q

What are the polar amino acids with uncharged R groups?

A

PSTAG

  1. Serine.
  2. Threonine
  3. Asparagine.
  4. Glutamine.
32
Q

What are the hydrophobic amino acids?

A
  1. Alanine.
  2. Phenylalanine.
  3. Leucine.
  4. Isoleucine.
  5. Tyrosine.
  6. Tryptophan.
  7. Valine.
  8. Methionine.
33
Q

What is special about proline?

A

R group bends around to form a covalent bond with nitrogen atom of amino group. This creates a kink in the protein chain.

34
Q

What happens to LDLR receptor during receptor mediated endocytosis?

A
  1. A reduction in pH of endosome.
  2. This causes a conformational change in LDLR due to the presence of a histidine residue.
  3. LDL can no longer bind to the receptor and is released to the lysosome.
35
Q

What part of the LDLR is affected due to the mutation which causes hypercholesterolemia?

A

Mutation in gene which codes for histidine residue.

36
Q

What are the 3 types of secondary protein structure?

A
  1. Alpha helix.
  2. Beta sheets.
  3. Bend/loop.
37
Q

How many amino acids per turn are there in a right handed alpha helix?

A

3.6 amino acid residues.

38
Q

Which amino acid numbers do hydrogen bonds form between?

A

Every fourth amino acid

39
Q

What is a beta strand?

A

Extended stretches of 5 or more amino acids.

40
Q

How many amino acids are required to form a bend/loop?

A

4 amino acids.

41
Q

What amino acid is commonly found in bends/loops?

A

Proline.

42
Q

Name four quaternary structures, stating how many subunits each has.

A
  1. Mechanosensitive channels (7 identical).
  2. Stored insulin (6 identical).
  3. Heterotrimeric G protein (3 different subunits).
  4. 70S ribosomes (30 different subunits).
43
Q

What amino acid residue forms hydrogen bonds with haem molecule?

A
  1. Histidine F8 (eight residue of F helix).
44
Q

What amino acid residue stabilises the oxygen molecule?

A

Histidine E7.

45
Q

What amino acid change occurs in sickle cell anaemia and at which position?

A
  1. Position 6 in beta chain of haemoglobin.

2. Hydrophilic glutamic acid is replaced by hydrophobic valine.

46
Q

Describe the structure of collagen.

A
  1. Consists of building blocks of tropocollagen.

2. Each consists of 3 polypeptide chains with a left handed twist wound together to form a right handed supercoil.

47
Q

Explain the importance of glycine in collagen.

A
  1. Small side chain allows tight turns.
  2. Small side chains allows close packing of subunits.
  3. 3 amino acid residues per turn.
48
Q

Explain the importance of proline in collagen.

A
  1. Imposes left hand twists in the helix.
  2. Makes it most stabilising force of the protein.
  3. Hydroxyproline forms H bonds that stabilise the triple helix.
49
Q

Explain how the covalent cross links form in collagen.

A
  1. Lysine deaminated using lysyl oxidase.
  2. This produces allysine (an aldehyde derivative).
  3. Two allysine molecules combine to form an aldol condensation product.
50
Q

Name three diseases associated with collagen.

A
  1. Osteogenesis imperfecta.
  2. Scurvy.
  3. Ethlers-Danloss syndrome.
51
Q

What enzyme is lacked in Phenylketonuria?

A

Phenylalanine hydroxylase.

52
Q

What is the x and y intercept on Lineweaver-Burke Plots?

A
  1. X intercept: -1/Km.

2. Y intercept: 1/Vmax.

53
Q

How is Km expressed

A

Km= (k-1 + k2)/k+1.

54
Q

What does a low Km represent?

A

High affinity of enzyme and substrate.

55
Q

What is Km?

A

Substrate concentration at which the enzyme works at half of maximum rate.

56
Q

What are the units of Km?

A

Concentration (M).

57
Q

What does k2 equal?

A

Vmax/(E) total

58
Q

Explain the importance of glucokinase in phosphorylation of glucose?

A
  1. Found in liver and has a very high Km, meaning it will only phosphorylate glucose when concentrations are high, allowing production of glycogen.
59
Q

Give two examples of irreversible inhibition.

A
  1. DIPF (an organophosphate) inhibits AChE.

2. Aspirin inhibits COX-1 preventing AA being converted to Prostaglandin H2.

60
Q

Give an example of a competitive inhibitor.

A

Sulphonamides as have similar shape to 4-aminobenzoic acid (needed to make folic acid for bacteria).

61
Q

What is the effect of competitive inhibitors on Vmax and Km?

A
  1. Vmax stays the same.

2. Km increases (line becomes steeper).

62
Q

What is the effect of non-competitive inhibition on Vmax and Km?

A
  1. Vmax decreases.

2. Km stays the same.

63
Q

What is the effect of mixed inhibitors on Vmax and Km?

A
  1. Vmax decreases.

2. Km increases.

64
Q

Give an example of allosteric inhibition.

A
  1. Phosphofructokinase.

2. Has two binding sites for ATP: an active site and an inhibition site.

65
Q

Explain what one most do if they get ethylene glycol poisoning?

A
  1. Give a near intoxicating dose of ethanol.

Ethanol competes with ethylene glycol for alcohol dehydrogenase active hence slows the production of toxic oxalate.

MD2001 (10 decks)

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