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Fundamentals Of Life Science > Proteins and Enzymes > Flashcards

Proteins and Enzymes Flashcards

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1
Q

What is a protein?

A

Linear covalent polymers of amino acids which have a specific 3D structure

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2
Q

What is a fibrous protein?

A

Elongated in 1 direction

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3
Q

What are the roles of fibrous proteins?

A

Specialised for mechanical strength and support

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4
Q

What are globular proteins?

A

Compact proteins which are often water soluble

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5
Q

What are the roles of globular proteins?

A

Dynamic proteins such as enzymes or receptors.

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6
Q

What is an example of a part globular, part structural protein?

A

Myosin

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7
Q

What percentage of dry cell weight do proteins represent?

A

50%

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8
Q

What is the role of proteins?

A

to perform the functions essential for life

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9
Q

What is the structure of an amino acid?

A

Carboxyl group
Amino group
R group
H atom

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10
Q

What causes the folding of proteins?

A

The hydrophobic effect (driven by the need of internalise hydrophobic polypeptide chains) (polar chains on outside, non-polar on inside)

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11
Q

What is the hydrophobic effect?

A

globular proteins internalise the non polar hydrophobic side chains of amino acids and externalise the polar amino acids which can form hydrogen bonds with the external environment.

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12
Q

What is pKA?

A

PH value at which a weakly ionising group is 50% associated

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13
Q

What is the role of di-sulfide bridges?

A

Hold polypeptide chains in shape

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14
Q

What is the most hydrophobic amino acid?

A

Phenylalanine

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15
Q

What are the aromatic amino acids?

A

Tryptophan, Tyrosin and Phenylalanine

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16
Q

In what form do amino acids exist as?

A

Zwitter ions

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17
Q

What are required to form polypeptides with other amino acids?

A

Charged interactions between amino acids

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18
Q

What is the simplest amino acid?

A

Glycine

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19
Q

What are the main hydrophobic amino acids?

A

Valine, Leucine and Isoleucine

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20
Q

What is special about the cystine amino acid?

A

Contains a very reactive sulphydral group which can form di-sulphide bonds with other cystine residues in a spontaneous oxidation reaction

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21
Q

what is special about Tyrosine?

A

It is an aromatic amino acid which is polar due to its reactive OH group.

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22
Q

What is the primary structure?

A

linear sequence of amino acids

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23
Q

What is the secondary structure?

A

regions of regularly repeating conformations of the peptide stabilised by hydrogen bonding between the peptide groups e.g alpha helices and beta sheets

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24
Q

What is tertiary structure?

A

the 3D shape of the folded chain. Arrangement of all amino acids including R groups and any prosthetic groups (in a single polypeptide chain)

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25
Q

What is the quaternary structure?

A

the arrangement of two or more polypeptide subunits in an oligomeric protein (multi chain only)

26
Q

which amino acids have ionising side chains?

A

Asp, Glu, His, Arg, Ly, Tyr and Cys

27
Q

How do we know that ionising side chains have an effect on protein structure and function?

A

Use electrophoresis to separate proteins and amino acids at different PHs, because they carry different charges at different PHs

28
Q

Describe the structure of a right handed alpha helix

A

Each C=O is hydrogen bonded with the amide hydrogen of the residue 4 places ahead

29
Q

What’s an example of an alpha helix

A

Alpha Keratin

30
Q

What’s an example of a beta pleated sheet?

A

virus coat proteins

31
Q

Describe the tertiary structure of Mb

A
  • contains a heme group
  • globular
  • folded to be very compact (with hydrophobic on inside)
  • 75% of amino acids folded into a right handed alpha helix
32
Q

Why is Hb an allosteric protein?

A

It has multiple ligand binding sites

33
Q

What is the structure of Hb made up of?

A

Two molecules of alpha globin
Two molecules of beta globin
Tetramer organised into a pair of dimers
Largely alpha helical

34
Q

What is collagen?

A

A major protein in vertebrae connective tissue (25-35% of total proteins in mammals)

35
Q

What is collagen made up of?

A
  • Units of the triple stranded tropocollagen molecule. The triple helix is held together by H bonds between chains.
  • multiple repeats of -Gly-X-Y (where X is often proline and Y is often hydroxyproline)
  • Three left handed helical chains coiled around each other in a right handed supercoi
36
Q

What is an enzyme?

A

Usually a protein (can sometimes be RNA) that accelerates biological reactions

37
Q

Why are enzymes important for life?

A
  • Accelerates metabolic reactions
  • enables regulation of metabolic reactions
  • integration of metabolism
38
Q

What are the biomedical applications of enzymes?

A
  1. Diagnostic reagents (e.g enzymes being released into blood after tissue damage)
  2. Lab reagents
  3. Drug metabolism
  4. Drugs work by inhibiting enzymes
39
Q

What are isozymes?

A

Tissue-specific physically distant form of an enzyme

40
Q

What is important about the Methionine residue?

A

Important at the start of translation as is coded for by the AUG. This is an essential amino acid

41
Q

What is important about the Lysine residue?

A

+tve charge which helps packaging of DNA in the nucleus forming chromatin.

42
Q

Which amino acids are the small amino acids?

A

Glycine (gly)

Alanine (Ala)

43
Q

Which are the nucleophilic amino acids?

A

Serine (Ser)
Threonine (Thr)
Cystine (Cys)

44
Q

Which are the aromatic amino acids?

A

Phenylalanine (Phe)
Tyrosine (Tyr)
Tryptophan (Trp)

45
Q

Which amino acids are hydrophobic?

A 
Valine (Val)
Leucine (Leu)
Isoleucine (Ile)
Methionine (Met)
Proline (Pro)
46
Q

Which amino acids are amides?

A

Glutamine (Gln)

Asparagine (Asn)

47
Q

Which amino acids are Acidic?

A 
Aspartic acid (Asp)
Glutamic Acid (Glu)
48
Q

Which amino acids are Basic?

A

Histamine (His)
Lysine (Lys)
Argenine (Arg)

49
Q

What is an essential amino acid?

A

Amino acids which cannot be made in the body and therefore must be obtained through the diet

50
Q

What are the essential amino acids?

A

Thr
Phe, Trp
Val, Leu, Ile, Met
His, Lys

51
Q

What is a non-essential amino acid?

A

An amino acid that can be made within the body

52
Q

What are the non-essential am ino acids?

A 
Pro
Cys, Ser
Gly, Ala
Gln, Asn
Arg
Asp, Glu
Tyr
53
Q

What is the side chain to Cystine?

A

CH2 - SH

54
Q

What is the side chain to Glutamic acid (glutamate)?

A

CH2-CH2-C=O-OH

55
Q

What is the side chain to Glutamine?

A

CH2-CH2-C=O-NH2

56
Q

What is the side chain to Glycine?

A

H

57
Q

What is the side chain to Serine?

A

CH2OH

58
Q

What is the side chain to Phenylalanine?

A

CH2-aromatic ring

59
Q

What is the side chain to Tyrosine?

A

CH2- aromatic ring - OH

60
Q

What is the side chain to Valine?

A

CHCH3-CH3

Fundamentals Of Life Science (26 decks)

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