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Biochemistry > Biochemistry > Flashcards

Biochemistry Flashcards

0
Q

Why are polysaccharides insoluble?

A

The hydroxyl groups in polysaccharides are involved in hydrogen bonds between the polymer chains. Therefore, the polysaccharides are insoluble. Starch and glycogen are stored in granules within cells. Cellulose forms extracellular fibres.

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1
Q

What is a polar molecule?

A

A molecule can be described as polar if it has a permanent dipole. A permanent dipole is due to a difference in electronegativity between the atoms involved in a covalent bond.

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2
Q

What is the difference between an alpha and beta D-glucose?

A

The OH group on carbon 1. Alpha is below and beta is above.

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3
Q

What is the difference between a Fischer projection and a Haworth projection?

A

Fischer projection is a straight line and Haworth projection is a ring.

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4
Q

How can you tell the difference between a Aldose and a ketose monosaccharide?

A

Ketose has oxygen attached to second carbon and Aldose has OH group attached to second carbon.

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5
Q

Name 3 differences between cellulose and starch.

A

Cellulose linkages are B1-4 and starch contains a1-4 and a1-6.
Starch consists of 2 structures - amylose and amylopectin. Cellulose contains one structure of unbranched monomers.
Cellulose forms microfibrlls which are upto 70 parallel neighbouring chains cross linked by H bonding.

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6
Q

Name two forms of starch.

A

Amylopectin and amylose.
Amylopectin is amylose but branched, very large involving upto a million glucose molecules.
amylose is unbranched, helical, joined by 1a-4 links, 6 glucose units per turn.

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7
Q

How do homopolymers and hetropolymers differ. Give an example of each.

A

Homopolymers is one repeating unit like glycogen and heteropolymer is 2 or more repeating units like hyaluronic acid.

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8
Q

In water What is the angle of H-O-H

A

104 degrees

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9
Q

Which amino acid puts a kink in a chain?

A

Proline. It prevents H bonds that stabilise a helix and is pleated sheet breaker.

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10
Q

What is an epimer?

A

Isomers which differ at only one carbon.

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11
Q

What is an anomer?

A

An isomer that differs only at keto-/aldo Carbon.

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12
Q

What is an enantiomer?

A

Isomers that are mirror images (D and L) (optical isomers/stereo isomers)

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13
Q

What is a reducing agent?

A

An element or compound which loses (or donates) an electron to another chemical species in a redox chemical reaction. Since the reducing agent is losing electrons is is said to be oxidised.

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14
Q

What is an aldehyde?

A

An organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl centre (a carbon double bonded to oxygen) bonded to hydrogen and an R group. Aldehydes differ from ketones in that the carbonyl is placed at the end of a carbon skeleton rather than between two carbon atoms.

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15
Q

What is a reducing sugar?

I.e. A sugar that donates an electron and becomes oxidised in a redox reaction.

A

A reducing sugar is any sugar that, in an alkaline solution, forms some aldehyde or ketone.
E.g. Maltose and lactose but not sucrose.

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16
Q

What are you looking for to distinguish between a reducing sugar and a non reducing sugar?

A

Linkage 1-2 as in sucrose means they have joined at the anomers and so there is no free aldehyde, keto or hemiacetal to allow the ring to open.

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17
Q

What are the linkages for the branch points of amylopectin?

A

a(1-6) linkages

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18
Q

What is lipid peroxidation?

A

Becoming rancid

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19
Q

What is an isoprene?

A

A lipid not containing glycerol. (Apart from fatty acids)
it exists in vitamins and minerals.
Vitamin E, K have derivitives of isoprene within their structure.

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20
Q

What does Vitamin K do?

A

Vitamin K is a cofactor required for blood clotting.

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21
Q

What is 666-5 ring structure? The steroid carbon skeleton

A

Lipids (apart from fatty acids) not containing glycerol. includingSteroids or cholesterol

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22
Q

Is Cholesterol polar or non polar?

A

Generally non-polar except one OH group.

Can be converted into other compounds - see slide

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23
Q

Which lipids are more susceptible to peroxidation?

What is the 3 stage process?

A

Polyunsaturated fatty acids (PUFAs)

3 stashes are initiation propagation and termination.

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24
Q

How do antioxidants slow or stop peroxidation at the propagation stage?

A

Because they are reducing agents thus loses an electron to allow free radicals to become stable and form ketone.

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25
Q

What is ^G?

A

Change in Gibbs free energy.

^ is a triangle

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26
Q

What does delta G degrees equal?

A

Change in Gibbs free energy at standard conditions

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27
Q

What are the six classes of enzymes?

A

Oxidoreductases, transferases, hydrolase, lyases, isomerases and ligases

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28
Q

What does an enzyme do to activation energy?

A

An enzyme lowers activation energy needed to change substrate into product.

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29
Q

How does enzyme substrate complex lower activation energy or the free energy of activation?

A

By either stabilising the transition state or providing an alternative transition state,

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30
Q

What does dehydrogenase do?

A

Dehydrogenase takes hydrogen but can also add.

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31
Q

What does the enzyme decarboxylase do?

A

Decarboxylase takes the carboxyl group out.

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32
Q

Define enthalpy (H)?

A

?

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33
Q

Define entropy (S)?

A

Measure of randomness or disorder of the system

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34
Q

What type of reaction is catalysed by Oxidoreductases?

A

oxidation and reduction ( removal or addition of hydrogen atoms)

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35
Q

What type of reaction is catalysed by transferases?

A

Transfer of chemical group (e.g. phosphate, methyl) from one substance to another.

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36
Q

What type of reaction is catalysed by hydrolases?

A

Hydrolysis (splitting of bonds by water)

37
Q

What type of reaction is catalysed by lyases?

A

Removal of chemical groups from substances

38
Q

What type of reaction is catalysed by Isomerases?

A

Structural rearrangement of atoms within one molecule.

39
Q

What type of reaction is catalysed by ligases.

A

Joining together of two molecules utilising energy (e.g. ATP).

40
Q

Why does the enzyme catalyst reaction tail off with time?

A 
Several possible reasons 
1 enzyme becomes thermally inactivated with time.
2 product inhibition.
3 substrate depletion.
4 product build up - reverse reaction
41
Q

What is Vo?

A

Initial rate or initial velocity and is expressed as micromol substrate converted to products per minute.

42
Q

What is the concentration rate curve described by

A

The concentration-rate curve is described by the Michaelis-Menten equation and obeys Michaelis-Menten Kinetics.

43
Q

What is Michaelis constant (Km)?

A

A measure of affinity of that substrate for the enzyme - the lower the Km the greater the affinity.

44
Q

What is the change in Gibbs free energy for a reaction at equilibrium.

A

Zero

45
Q

True or false?

The change in Gibbs free energy of a reaction is not altered in an enzyme catalysed reaction.

A

True

46
Q

Which enzyme is a protease that begins digestions of proteins breaking them into peptides and amino acids?

A

Pepsin

47
Q

What does Vmax represent?

A

Maximum reaction velocity

48
Q

Name two linear transformation of the Michaelis - Menton equation.

A

Lineweaver-Burk and Eadie-Hofstee stay

49
Q

What does [S] represent?

A

Substrate concentration

50
Q

What is the difference between a rectangular hyperbola curve and the sigmoidal curve?

A

Draw them

51
Q

What has a higher melting point a cis-cis fFatty acid or a saturated fatty acid?

A

Saturated fatty acid

52
Q

Why does the enzyme catalyst reaction tail off with time?

A 
Several possible reasons 
1 enzyme becomes thermally inactivated with time.
2 product inhibition.
3 substrate depletion.
4 product build up - reverse reaction
53
Q

What is the concentration rate curve described by

A

The concentration-rate curve is described by the Michaelis-Menten equation and obeys Michaelis-Menten Kinetics.

54
Q

What is Michaelis constant (Km)?

A

A measure of affinity of that substrate for the enzyme - the lower the Km the greater the affinity.

55
Q

What is the change in Gibbs free energy for a reaction at equilibrium.

A

Zero

56
Q

True or false?

The change in Gibbs free energy of a reaction is not altered in an enzyme catalysed reaction.

A

True

57
Q

Which enzyme is a protease that begins digestions of proteins breaking them into peptides and amino acids?

A

Pepsin

58
Q

What does Vmax represent?

A

Maximum reaction velocity

59
Q

Name two linear transformation of the Michaelis - Menton equation.

A

Lineweaver-Burk and Eadie-Hofstee stay

60
Q

What does [S] represent?

A

Substrate concentration

61
Q

What is the difference between a rectangular hyperbola curve and the sigmoidal curve?

A

Draw them

62
Q

What has a higher melting point a cis-cis fFatty acid or a saturated fatty acid?

A

Saturated fatty acid

63
Q

What is an aliphatic amino acid?

A

Amino acid with hydrocarbon side chain.

64
Q

What makes amino acids hydrophilic?

A

Hydroxyl group capable of hydrogen bonding and neutral polar.

65
Q

What makes an amino acid hydrophobic?

A

Hydrocarbon side chain, aliphatic, aromatic ring,

66
Q

What is special about the amino acid proline?

A

Bends protein, contributes compactness of globular proteins,

67
Q

What is a chiral carbon?

A

A carbon which has four different groups attached.

68
Q

What is a neutral polar?

A

An amino acid that is not charged at physiological pH.

69
Q

Why are neutral polar amino acids considered to be hydrophilic?

A

Because they have hydroxyl groups in their side chains which make them capable of hydrogen bonding

70
Q

What type of bonding is involved in acidic and basic amino acids?

A

Ionic bonding

71
Q

When are ion pairs, also known as salt bridges, formed?

A

When amino acids of opposite charge are in close proximity of each other they can form salt bridges.

72
Q

What does the formation and breakage of ion pairs/salt bridges depend on?

A

PH

73
Q

What do ion pairs/salt bridges do to tertiary structures?

A

Increase stability.

74
Q

What is the bond angle for water?

A

104.5 degrees.

75
Q

In water how many times weaker is hydrogen bonds to covalent bonds?

A

20

76
Q

What makes water have a higher than expected melting and boiling point?

A

The hydrogen bonding.

77
Q

What would denature a disulphides bridge -s-s-

A

Reducing agents

78
Q

What would denature an ionic bond?

A

Acid (-COOH~ to -COOH)

Alkali ( +H3N to H2N-)

79
Q

What would denature hydrogen bonds?

A

Urea

80
Q

What denatures hydrophobic bonds?

A

Organic solvents (non polar) and detergents.

81
Q

Name 3 types of reversible inhibitors?

A

Competitive, non competitive and uncompetitive.

81
Q

What effect does a competitive inhibitor have on the enzyme reaction rate?

A

Decreases the velocity (Vo) but not the Vmax.

82
Q

When Michaelis-Menton is not preserved and a S shaped sigmoidal plot is mapped, what would that tell you about the enzyme?

A

The enzyme is allosteric.

83
Q

Why are lipids known as amphiphiles?

A

Because they have polar and non polar regions within their structure.

84
Q

What does a phosphatidyl choline contain?

A

A choline group, a phosphate group, a glycerol and two fatty acids.

85
Q

What does a triglyceride contain?

A

A glycerol and three fatty acids.

86
Q

What are the five classes of lipids?

A
  1. Fatty acids, 2.acylglycerols- glycerides a - neutral fat
  2. phosphoacylglycerols or phosphglcerides
  3. Lipids not containing glycerol (except f.a.)
  4. Lipids combined with other molecules such as proteins or carbohydrates
87
Q

Esterification can sometimes be same as condensation or dehydration reaction. what is lipolisis?

A

lipolisis is when you add water to lipids which is by hydrolysis reaction

88
Q

What is the symbol for entropy?

A

S

89
Q

What is the symbol for gas constant?

A

R

Biochemistry (11 decks)

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