Chapter 3 - proteins Flashcards

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1
Q

what is the structure of an amino acid?

A
  • amine group (H-N-H)
  • variable R group (diff R group=diff amino acids)
  • carboxyl group (O=C-O-H)
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2
Q

how are peptides synthesised?

A

1) peptide bond formed between two amino acids by a condensation reaction (carboxyl + amine group)
resulting in a dipeptide
2) many amino acids joined=polypeptide formed (catalysed by peptidyl transferase)
3) R groups interact forming bonds - causes long chains of amino acids folding in proteins
4) diff sequences of amino acids=diff structures=diff shapes

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3
Q

how to separate amino acids using thin layer chromatography?

A

1) stationary phase
- layer of silica gel applied to rigid surface
- add amino acids to one end of gel
- submerge this end in organic solvent
2) mobile phase
- organic solvent moves through silica gel

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4
Q

what is the primary structure of protein?

A
  • the sequence in which amino acids are joined
  • bonds involved=peptide bonds
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5
Q

what is the secondary structure of proteins?

A
  • oxygen, hydrogen, and nitrogen atoms of amino acids interact
  • can form alpha helix or beta pleated sheet
  • bonds involved=peptide bonds, hydrogen bonds
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6
Q

what is the tertiary structure of proteins?

A
  • the folding of a protein into its final shape
  • R groups interact
  • bonds involved=peptide bonds, hydrogen bonds, ionic bonds, disulfide bonds
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7
Q

what is the quaternary structure of proteins?

A
  • results from association of two or more individual proteins (subunits)
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8
Q

hydrophilic and hydrophobic interactions?

A
  • the way a protein folds depends on whether R groups are hydrophilic or hydrophobic
  • hydrophilic groups=outside, hydrophobic groups=inside
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9
Q

how are peptides broken down?

A
  • proteases (enzymes) catalyse the breakdown
  • water molecule used in hydrolysis reaction
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10
Q

what is the Biuret test for proteins?

A

1) mix equal volume of sample and 10% sodium hydroxide solution
2) add 1% copper sulfate solution until solution turned blue
3) mix solution
positive=purple

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11
Q

what are globular proteins?

A
  • compact, water soluble, spherical shape, soluble
  • essential in regulating many of the processes needed for life
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12
Q

what is insulin?

A
  • a globular protein
  • a hormone
  • involved in the regulation of blood glucose concentration
  • soluble
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13
Q

what are conjugated proteins?

A
  • globular proteins that contain a non protein component (prosthetic group)
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14
Q

what is haemoglobin?

A
  • red, oxygen carrying pigment found in red blood cells
  • quaternary protein (four polypeptides subunits)
  • each subunit contains a prosthetic haem group
  • iron in haem groups enable haemoglobin to carry oxygen
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15
Q

what is catalase?

A
  • an enzyme
  • quaternary protein (four haem prosthetic groups)
  • iron allows catalase to interact with hydrogen peroxide and speed up its reactions
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16
Q

what are fibrous proteins?

A
  • formed from long, insoluble molecules
  • contain a limited range of amino acids
  • tend to make strong, long molecules
17
Q

what is keratin?

A

-group of fibrous proteins
- present in hair, skin and nails
- large proportion of sulfur containing amino acids=many strong disulfide bonds=strong, inflexible, insoluble materials

18
Q

what is elastin?

A
  • fibrous protein
  • found in elastic fibres
  • present in the walls of blood vessels and alveoli=give these the flexibility to expand and return
  • quaternary protein
19
Q

what is collagen?

A
  • a fibrous protein
  • connective tissue found in skin, tendons, ligaments, nervous system
  • made of 3 polypeptides wound together
  • long, rope-like structure
  • has flexibility