Proteins Flashcards

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1
Q

What are proteins made up of?

A

Amino acids

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2
Q

What are the bonds that hold together amino acids?

A

peptide bond

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3
Q

Name the parts that make up amino acids (draw a simple diagram)

A

Amino group
Carboxylic acid group
Alpha-carbon
R chain

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4
Q

How many amino acids are there?

A

20

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5
Q

Name what is formed when a series of amino acids are joined together

A

Polypeptide (polymer)

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6
Q

Describe the meaning of polymerisation

A

The joining of many monomers into a polymer

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7
Q

Describe the primary structure (of protein)

A

Sequence of amino acids into a polypeptide chain.

  • As each amino acid has a different molecular structure in their R group + as these molecular differences affect all bonds that the polypeptide chain will be able to make
  • The primary structure determines the ultimate shape + functionality of the protein
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8
Q

Describe the secondary structure (of protein)

A

Polypeptide chain twisted into a 3D shape
Occurs as H bonds form between the ‘+’ charged H of the NH group and the ‘-‘ charged C=O group (H bonds relatively weak)
E.g an a-helix or B-pleated sheet

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9
Q

Describe the tertiary structure (of protein)

A
  • It is the result of further twisting of secondary structure
  • It can be complex + is specific to protein
  • Also plays significant role in determining the behaviour of the protein
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10
Q

Name the 3 types of bond that is maintains the tertiary structure

A

Disulfide bonds - fairly strong + not easily broken
Ionic bonds - form between any carboxyl groups + amino groups not involved in peptide bonds. Weaker than disulfide bonds + easily broken by changes in pH
Hydrogen bonds - numerous but easily broken

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11
Q

Describe the quaternary structure

A

Multiple polypeptides bond together e.g haemoglobin (large protein) - the haem group is not a protein

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12
Q

Describe the test for proteins

A

Biuret test (which detects peptide bonds):

  1. Place sample of the solution to be tested into a test tube + add equal volume of NaOH solution at room temp.
  2. Add a few drops of very dilute (0.05%) copper (II) sulfate solution + mix gently
  3. A purple colouration indicates the presence of peptide bond and hence a protein (if protein is not present it remains blue)
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13
Q

What is the difference between fibrous and globular proteins? Give an example of each

A

Fibrous proteins: have structural functions e.g collagen is found in tendons which join muscles to bones
Globular proteins: perform metabolic reactions e.g enzymes + haemoglobin

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14
Q

Describe the difference between the shapes/structure of fibrous and globular proteins

A

Fibrous: long polypeptide strands/chains twisted together (tightly wound around one another) - form long parallel chains. Chains are linked by cross-bridges + so form very stable molecules
Globular: not long but polypeptide chains wrapped around one another in a ball/bundle shape

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15
Q

Describe the structure and function of the fibrous protein collagen

A
  • Primary structure is a polypeptide chain
  • Secondary structure is that it is very tightly coiled
  • Higher concentration of glycine (an amino acid) helps it to pack closer together
  • Tertiary structure is also a helix shape
  • Quaternary structure is 3 double coiled polypeptide chains wound together
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