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Proteins > Protein Diversity & Amino Acids > Flashcards

Protein Diversity & Amino Acids Flashcards

1
Q

What is the proteome?

A

The full set of proteins encoded by the human genome

This is NOT the same as the number of genes

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2
Q

What mechanisms mean that one gene does not result in one protein?

A
  1. single nucleotide polymorphisms give rise to proteins that differ by 1 AA
  2. alternative splicing of RNA
  3. post-translational modifications
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3
Q

What are the functions of proteins within the cell?

A
  1. 2/3 are either binding molecules or enzymes
  2. receptors
  3. signalling molecules
  4. structural molecules
  5. translation factors
  6. transporters
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4
Q

What causes phenylketonuria?

A

The absence of the enzyme phenylalanine hydroxylase

This means phenylalanine cannot be broken down

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5
Q

What are the two main proteins involved in transport?

A

Haemoglobin and ferritin

Ferritin is needed to transport iron

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6
Q

What causes Duchenne muscular dystrophy?

What does this result in?

A

Dystrophin is absent/ineffective

Patients lose the ability to use their muscles

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7
Q

What is osteogenesis imperfecta?

What causes it?

A

Brittle bone disease

A mutation in the collagen gene means that collagen is not correctly formed

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8
Q

What causes scurvy?

A

A lack of vitamin C

Vitamin C is crucial in collagen formation

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9
Q

How are proteins involved in regulation?

A

They are involved in the regulation of cell division, protein synthesis and hormones

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10
Q

What is self-recognition?

A

The immune system checks that all the cells belong to us and identifies those that don’t

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11
Q

What causes myasthenia gravis?

A

Antibodies bind to a neurotransmitter receptor at the neuromuscular junction

This means the body cannot respond to neurological signals

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12
Q

What is the general structure of an amino acid?

A

It has a central alpha carbon atom

This is attached to an amino group and a carboxyl group

It is also attached to a H atom and an R-group

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13
Q

How are amino acids named?

What are the abbreviations of their names?

A

Alpha-amino acids are named according to the R group they contain

They have a full name, a 3-letter code and a 1-letter code

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14
Q

How does the R-group determine the behaviour of an amino acid?

A

The R-groups of amino acids have different chemical properties

The R-group determines the behaviour of an amino acid when it is incorporated into a polypeptide chain

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15
Q

How many amino acids are there?

A

There are many, but only 20 are found in proteins

The others may have metabolic roles

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16
Q

What are the 5 different ways of categorising R-groups?

A
  1. size (large/small)
  2. shape (aliphatic/aromatic)
  3. hydrophobicity (polar/non-polar)
  4. charge (acidic/basic)
  5. sulphur-containing
17
Q

What are the 2 sulfur containing amino acids?

A

Cysteine and methionine

18
Q

What is significant about the structure of proline?

A

It is NOT an amino acid

It is an imino acid

19
Q

What are the 9 amino acids that have non-polar side chains?

A
  1. glycine
  2. alanine
  3. valine
  4. leucine
  5. isoleucine
  6. methionine
  7. phenylalanine
  8. tryptophan
  9. proline
20
Q

What are the 6 amino acids that have polar side chains?

A
  1. serine
  2. threonine
  3. cysteine
  4. tyrosine
  5. asparagine
  6. glutamine
21
Q

What are the 2 acidic amino acids that have negatively charged side chains?

A
  1. aspartate

2. glutamate

22
Q

What are the 3 basic amino acids that have positively charged side chains?

A
  1. lysine
  2. arginine
  3. histidine
23
Q

How does the structure of proline differ from the other amino acids?

A

The alpha amino group is covalently linked to the side chain

This makes it a secondary amine, rather than a primary amine

24
Q

How does the structure of proline affect its properties?

A

The C-N bond is very inflexible

This limits the conformations that it can take up in the 3D structure of a protein

25
Q

Which amino acid does not have optical isomers?

Why?

A

All a-amino acids are chiral molecules, except glycine

Glycine does not have an optical isomer because it has a H atom as an R group

26
Q

What is a chiral molecule?

What types of isomers does it produce?

A

It has 4 different groups attached to the central carbon atom

This produces D- and L-isomers

27
Q

What type of optical isomers are found in proteins?

Why?

A

L-isomers

This is due to the specificity of enzymes - an enzyme could not catalyse a reaction with a D-isomer

28
Q

What determines the charge on amino acids with ionisable R groups?

A

The charge on amino acids with ionisable R-groups is pH dependent

29
Q

What groups are present in amino acids that are charged?

A

Charged amino acids contain either a weak acid or a weak basic group

This can exist in the ionised or unionised form, depending on the pH of the surroundings

30
Q

What value will tell you the pH at which an ionisable group ionises?

A

The pKa value for an ionisable group tells you at which pH the group ionises

The pKa value is the pH at which a group is 50% ionised

31
Q

What is the pKa value of carboxylic acid groups?

A

pH 1.8 - 2.5

This means at pH 7, in the body, these groups are almost always negatively charged

32
Q

What is the pKa value for amino groups?

A

pH 9 - 10

This means at pH 7, in the body, these groups are almost always positively charged

33
Q

What is the pKa value of histidine?

How does this affect its charge in the body?

A

pH 6 is close to the body pH (7)

Histidine residues are either positively charged or neutral depending on the immediate surrounding environment

34
Q

What function is significant about the pKa value of histidine?

A

Histidine residues are found in the active sites of enzymes

They act as donors or receptors of protons during enzymatic action

Proteins (5 decks)

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