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The human cell > Lecture 1 and 2 > Flashcards

Lecture 1 and 2 Flashcards

1
Q

Define condensation reaction

A

Activated monomers are linked together by the removal of water

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2
Q

What are the three components of a nucleotide?

A

Nitrogen containing base
Deoxyribose (five carbon sugar),
Phosphate group

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3
Q

What carbon is the phosphate and hydroxyl group attached to in a nucleotide?

A

5’ phosphate

3’ hydroxyl

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4
Q

What type of bond forms between nucleotides? What is this called?

A

Covalent bonds
Phosphodiester bonds
(Between hydroxyl and phosphate group)

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5
Q

What is formed by phosphodiester bonds between nucleotides?

A

Sugar-phosphate backbone

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6
Q

How are two polynucleotide chains held together?

A

Hydrogen bonding between the complementary bases

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7
Q

DNA strands are ___parallel

A

Anti

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8
Q

What type of helix do the sugar phosphate backbones wind into?

A

A right handed helix

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9
Q

What is the formula of a phosphate group in a nucleotide?

A

PO4

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10
Q

How far apart are nucleotides in a DNA helix?

A

0.34nm

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11
Q

What distance is between each complete turn of a DNA double helix?

A

3.4nm

10 nucleotides

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12
Q

Why can each strand of DNA act as a template for the synthesis of the other?

A

The two anti-parallel strands are reverse complements of each other

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13
Q

Define transcription

A

The synthesis of RNA from a DNA template

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14
Q

What are the three differences between RNA and DNA?

A

Ribose replaces deoxyribose
Uracil replaces thymine
RNA is single stranded

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15
Q

What are the 4 types of RNA?

A

Messenger
Ribosomal
Transfer
Micro

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16
Q

What does micro RNA do?

A

Regulates expression of mRNA

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17
Q

What protein complex translates mRNA into protein?

A

Ribosomes

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18
Q

How many possible codons are there? How many amino acids?

A

64 codons

20 amino acids (DNA is degenerate)

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19
Q

What are the three stop codons?

A

UAG, UAA, UGA

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20
Q

How are amino acids linked?

A

Condensation reaction in the ribosome forms a peptide bond (between amino group and carboxyl group)

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21
Q

Why do sterioisomers of amino acids exist?

A

Asymmetric alpha carbon

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22
Q

What sterioisomer of amino acids is found in proteins?

A

L- amino acids (not D)

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23
Q

What is pi-pi stacking of aromatic rings?

A

Delocalised electrons generate a weak charge in aromatic side chains

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24
Q

What electrostatic interactions can delocalised electrons in aromatic rings participate in?

A
  • Other aromatic pi-pi stacking

- Cations (side chains of lys, arg, ions and ligands)

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25
Q

What are the 9 classes of proteins?

A

Enzymes, structural, motility, regulatory, transport, hormonal, receptor, defensive, storage

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26
Q

What does it mean that amino acid chains have directionality?

A

N-terminus (amino acid group) at one end, C-terminus (carboxyl group) at the other

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27
Q

What type of bonding is responsible for the local folding of proteins (secondary structure)

A

Hydrogen bonding

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28
Q

Define alpha helix

A

Coiled form of peptide chain

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29
Q

How are alpha helix stabilized?

A

Regular hydrogen bonds between carbonyls and N-H groups of secondary amides of the peptide bond, 4 amino acids apart

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30
Q

How many amino acids are there per turn of the alpha helix?

A

3.6

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31
Q

What are beta sheets comprised of?

A

Adjacent beta strands, stabilized by regular hydrogen bonds between carbonyls and amides of the peptide backbone

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32
Q

What are the features of a beta sheet?

A

More extended chain than a helix

Alternate R groups point above and below the flat sheet

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33
Q

Define tertiary structure of a protein.

A

The overall 3D shape of a protein

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34
Q

What forces stabilize the tertiary structure of a protein?

A 
Hydrogen bonds, van der waals forces 
Disulphide bridges (covalent bond)
Salt bridges (ioninc bond)
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35
Q

What is a monomeric protein?

A

A protein consisting of only one polypeptide chain

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36
Q

Define quaternary structure.

A

Interaction of two or more polypeptide chains to form a protein complex

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37
Q

What name is given to a protein consisting of 2 or more polypeptide chains?

A

Multimeric protein

38
Q

What is collagen?

A

The most abundant protein in the human body

3 stranded coiled-coil

39
Q

Where is collagen found?

A

Extracellular matrix, connective tissue and muscle

40
Q

What is haemoglobin?

A

The most abundant protein in red blood cells
Tetramer
Four iron containing heme groups that carry oxygen around the body

41
Q

Where are fatty acids synthesized?

A

Mainly in liver and adipose tissue

42
Q

What enzyme synthesizes fatty acids?

A

Fatty acid synthase

43
Q

What name is given to the methyl end of a fatty acid?

A

Omega

44
Q

What name is given to the carboxyl end of a fatty acid?

A

Delta

45
Q

How is acetyl-CoA transported out of the mitochondrial matrix?

A

As citrate

46
Q

What is the first stage of fatty acid synthesis?

A

Loading

Acetyl-CoA and malonyl-CoA +ACP +MAT make acetly-ACP and malonyl ACP

47
Q

How many carbon atoms in Acetyl-CoA?

A

2

48
Q

How many carbon atoms in Malonyl-CoA?

A

3

49
Q

When does fatty synthesis occur?

A

In a fed state, high blood glucose (high insulin)

50
Q

What process occurs after loading during fatty acid synthesis?

A

Elongation

51
Q

What enzyme works on acetyl-ACP and malonyl-ACP? What reducing agent is used?

A

Ketosynthase

No reducing agent

52
Q

What type of reaction occurs when ketosynthase catalyses acetyl-ACP and malonyl-ACP?

A

Condensation

53
Q

What is the product of the first condensation reaction during fatty acid synthesis?

A

beta-ketoacyl and CO2

54
Q

What is the next step after condensation during fatty acid synthesis?

A

Reduction

55
Q

What enzyme is used to reduce beta-ketoacyl? What is the reducing agent?

A

Ketoreductase

NADPH

56
Q

What is the product when ketoreductase reacts with beta-ketoacyl in the presence of NADPH?

A

B-hydroxyacyl

57
Q

What is the next step, after reduction 1, in fatty acid synthesis?

A

Dehydration

58
Q

What enzyme is used to dehydrate beta-hydroxyacyl? What reducing agent is used?

A

Dehydratase

No reducing agent

59
Q

What is the product of dehydratase and beta-hydroxyacyl?

A

beta-enoyl and H2O

60
Q

What is the final step of fatty acid synthesis before the cycle repeats?

A

Enoylreductase reduces beta-enoyl using NADPH to form acyl (Cn+2)

61
Q

How many cycles does fatty acid synthase under go?

A

7

62
Q

What is formed by fatty acid synthase after 7 cycles?

A

Palmitate

63
Q

What enzyme removes ACP at the end of 7 cycles of fatty acid synthesis?

A

Thioesterase

64
Q

How many carbons are there in palmitate?

A

16

65
Q

How many carbon atoms are there in stearic acid?

A

18

66
Q

What is an 18 carbon fatty acid with one double bond in the middle called?

A

Oleic acid

67
Q

What enzyme can make oleic acid from stearic acid?

A

Desaturase

68
Q

How many malonyl/acetly-CoA, NADPH and ATP are used in the synthesis of palmitate?

A

7
14 NADPH
7ATP

69
Q

Where is ATP used in fatty acid synthesis?

A

Synthesis of malonly-CoA

70
Q

How is linoleic acid different from oleic acid?

A

linoleic acid is polyunsaturated, 2nd double bond is 6C from omega end (Omega-6 FA)

71
Q

What is alpha-linolenic aicd?

A

3 double bonds, one 3C from omega end (Omega 3-FA)

72
Q

Why is omega 3 and omega 6 essential fatty acids?

A

They must be obtained from diet

We do not have desaturase to remove hydrogen from 3rd or 6th carbon

73
Q

Where are fatty acids stored?

A

In triglycerides in adipose tissue

74
Q

How do fatty acids change fluidity and permeability of membranes?

A

Saturated and unsaturated fatty acids pack differently

75
Q

What enzyme converts omega 6/3 into membrane lipids?

A

Phospholipase

76
Q

Name an important derivative of omega 6 (linoleic acid)

A

Arachidonic acid

77
Q

Name an important derivative of omega 3 (alpha linolenic acid)

A

Eicosapentaenoic acid

78
Q

What enzymes convert omega 3/6 into their important derivatives?

A

Elongases, desaturases

79
Q

What are arachidonic acid and eicosapentaenoic acid used for?

A

Paracrines

80
Q

Name some paracrines derived from essential fatty acids.

A

Leukotrienes, prostoglandins, thromboxanes

81
Q

What are these paracrines effects?

A

Mediators of inflammation, pain, fever, immunosuppression, clotting, vasoconstriction, air way constriction

82
Q

How many x more efficient is triglyceride than glycogen?

A

6x energy store

83
Q

What is the structure of a triglyceride?

A

glycerol head, ester bond between 3 fatty acid tails

84
Q

Why can triglycerides store more energy per mass as opposed to glycogen?

A

They’re anhydrous- they contain no H2O

85
Q

What is the sugar found in ATP?

A

Deoxyribose

86
Q

What is the adinosine part of ATP made of?

A

Adenine

deoxyribose

87
Q

What bonds are between the phosphate groups of ATP?

A

Phosphoanhydride bond

88
Q

Other than energy, what is the citric acid a source for?

A

Precursors for important biological molecules

89
Q

What is the first enzyme involved in glycogen catabolism?

A

Glycogen phosphorylase and phosphate

90
Q

What is the product of the first step of glycogen catabolism?

A

Glucose-1-phosphate (and the rest of the glycogen molecule)

91
Q

What enzyme acts on glucose-1-phosphate during glycogen catabolism?

A

Phosphoglucomutase

92
Q

What does is the product when phosphoglucomutase acts on glucose-1-phosphate?

A

Glucose-6-phosphate, which can then enter glycolysis

The human cell (10 decks)

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