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Structure + Function 1 > amino acids and proteins > Flashcards

amino acids and proteins Flashcards

1
Q

how many amino acids are building blocks for proteins in cells?

A

22

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2
Q

describe the general structure of an amino acid

A

Amino group - N terminus end

Carboxyl group - C terminus end

R group

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3
Q

what defines the chemical characteristics of the amino acid?

A

R

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4
Q

In what ways can amino acids be classified based on chemical characteristics?

A

All about R group side chain

Polar

Non-polar

Charged

Non-charged

Aliphatic

Aromatic

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5
Q

In which ways can amino acids be classified based on synthesis?

A

Proteinogenic

Non-proteinogenic

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6
Q

In what ways can amino acids be characterised based on essentiallnes

A

essential
conditionally essential
non essential

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7
Q

What makes an R group polar?

A

-OH group

C=O bond

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8
Q

amino acids with ‘polar uncharged R groups” are characterised by what?

A

polar groups in the side chains, which can form hydrogen bonds. e.g -OH, -SH, -C=O and -NH2

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9
Q

the amino acids with “aromatic R groups” are characterised by what?

A

an aromatic ring structure, which gives these amino acids there characteristic UV spectra

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10
Q

the amino acids with “acidic R groups” are characterised by what?

A

the amino acids aspartate and glutamate, the negatively charged side chains can form electrostatic interactions with positively charged basic side chains

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11
Q

the amino acids with “basic R groups” are characterised by what?

A

lysine, arginine and histidine, positive charged side chains

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12
Q

the amino acids hydroxyproline and hydroxylysine are hydroxylated forms of what? what do they require for their synthesis?

A
  • proline and lysine
  • vitamin C as a co enzyme
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13
Q

what is desmosine formed from?

A

4 lysine residues

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14
Q

how do you know if amino acids are aliphatic?

A

only carbon and hydrogen in the side chain

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15
Q

What are proteinogenic amino acids?

A

Building blocks of proteins

20 are encoded by triplets of the genetic code

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16
Q

What is different about selenocysteine and pyrrolysine?

A

They both contain a structural change in the mRNA sequence allowing a STOP codon not to be recognised as such by a specific tRNA

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17
Q

What are non-proteinogenic amino acids?

A

Don’t need to bind into a protein to exert their function.

e.g. GABA (neurotransmitter)

Carnitine (transport of fatty acids in the blood)

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18
Q

How are non-proteinogenic amino acids produced?

A
  • are not produced directly and I isolation by standard cellular machinery
  • Occurring post-translationally, once the protein has already formed
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19
Q

What are some common modifications of non-proteinogenic amino acids?

A

Phosphorylation

Methylation

Acetylation

Hydroxylation

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20
Q

What are essential amino acids?

A

Cant be synthesised by the body so must be obtained through the diet

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21
Q

What are conditional essential amino acids?

A

In condition of stress, a surplus of these amino acids need to be uptaken through the diet to cope with body demand

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22
Q

What are non-essential amino acids?

A

Can be synthesised by the body

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23
Q

What is an issue with herbivores consuming lots of hay/straw/haylage?

A

High levels of lignin, which reduces the absorption of nutrients. This decreases levels of essential amino acids such as Lysine

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24
Q

What are some types of proteins in body?

A

Receptor

Contractile

Hormonal

Structural

Enzymes

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25
Q

What are some functions of proteins in the body?

A

Protection

Storage

Structure

Receptors

Transport

Enzymes

Contractions

Hormones

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26
Q

What is primary protein structure?

A

Sequence of a chain of amino acids

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27
Q

How do amino acids bind together?

A

Peptide (amide) bonds

28
Q

What type of chain is a protein?

A

polypeptide

29
Q

How does a peptide bond form?

A

dehydration synthesis reaction (condensation)

30
Q

What is secondary protein structure?

What are the 2 types?

A

When hydrogen bonds form between amino acids

α helix

β pleated sheets

31
Q

Is an α helix hollow?

A

NO - just a spiral

32
Q

Is an α helix hollow?

A

NO - just a spiral

33
Q

What type of spiral is an α-helix?

A

Right-hand spiral

34
Q

How do α-helix spirals form?

A

Every backbone NH group donates a hydrogen bond to the backbone C=O group of the amino acid, located 3 or 4 residues earlier along the protein sequence

35
Q

What does a β structure contain?

A

β strands and β sheets

36
Q

What are β strands?

A

Portions of the polypeptide chain that are almost fully extended, having a zig-zag shape

37
Q

Are β strands flexible or elastic?

A

Flexible but not elastic

38
Q

Describe the structure of β strands

A

H-bonded β strands can be on separate polypeptide chains, or on different segments of the same chain

β strands in a sheet can either be parallel or antiparallel

39
Q

How do β-sheets form?

A

When multiple β strands are arranged side by side, they form β sheets

39
Q

How do β-sheets form?

A

When multiple β strands are arranged side by side, they form β sheets

40
Q

How are β sheets stabilised?

A

Stabilised by hydrogen bonds between carbonyl oxygens and amide hydrogens on adjacent β strands

41
Q

What is tertiary protein structure?

A
  • Occurs when certain attractions are present between alpha helices and beta-pleated sheets
  • spatial arrangement of atoms
42
Q

How is protein tertiary structure stabilised?

A

Numerous weak interactions:

Hydrogen bonds

Electrostatic interactions

Hydrophobic interactions

Disulfide bonds

43
Q

How is protein tertiary structure stabilised?

A

Numerous weak interactions:

Hydrogen bonds

Electrostatic interactions

Hydrophobic interactions

Disulfide bonds

44
Q

What are the 2 major classes of tertiary structure proteins?

A

Fibrous and globular

45
Q

Are proteins always either hydrophilic or hydrophobic?

A

Can be either depending on structure, or amphipathic

46
Q

What is protein quaternary structure?

A

When a protein has more than one subunit and sometimes other elements too

47
Q

Give an example of a quaternary protein

A

haemoglobin

48
Q

Describe the structure of haemoglobin

A

4 chains

4 subunits

A non-protein heme group binding a Fe2+

49
Q

What is the function of haemoglobin?

A

Allows aerobic respiration by transporting O2 and CO2

50
Q

What causes mis-folded proteins?

A

Mutations in their amino-acid sequence

Error in the folding process

51
Q

What 2 types of effect can protein misfolding have?

A

Loss of function and gain of function

52
Q

What 2 types of effect can protein misfolding have?

A

Loss of function and gain of function

53
Q

Give an example of an effect of protein mis-folding which is loss of function?

A

Cystic fibrosis

54
Q

Give examples of an effect of protein mis-folding which is gain of function?

A

Alzheimer’s

Parkinson’s

Huntington’s

55
Q

What causes sickle-cell anaemia?

A

Mutation in haemoglobin

56
Q

What is the process of making RNA from DNA?

A

Transcription

57
Q

What is the process of making a protein from RNA?

A

Translation

58
Q

what do disulphide bonds consist of?

A

one cysteine residue

59
Q

how is the primary structure of a protein always written?

A

N->C terminal

60
Q

what structure is a a-helix?

A

secondary

61
Q

how many amino acids per tern of the helix are there in a a-helix

A

3.6

62
Q

the biological function of myoglobin is determined by the presence of a what?

A

heme (haem) group

63
Q

what bonds are formed between b-strands

A

hydrogen

64
Q

what amino acid does not have a chiral alpha carbon?

A

glycine

65
Q

what is the amino acid desmosine commonly found in?

A

elastin, a protein found in connective tissue

Structure + Function 1 (18 decks)

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