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tim bio 2021/2022 > 2.10 Proteins - structure, function and biuret test > Flashcards

2.10 Proteins - structure, function and biuret test Flashcards

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1
Q

What decides the amino acid sequence that determines the primary structure of a protein?

A

A DNA sequence

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2
Q

Describe the ionic bonds that hold the tertiary structure of a protein in place.

A

Weaker than disulfide bonds

Easily broken by changes in pH

Form between free carboxyl and amino groups in the polypeptide chain

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3
Q

What does Biuret reagent contain?

A

Concentrated Copper (II) sulfate solution

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4
Q

Describe the disulfide bonds that hold the tertiary structure of a protein in place.

A

Strong

Not easily broken

Occur between two cysteine amino acids

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5
Q

Name the bonds that hold the tertiary structure of a protein in place.

A

Disulfide Bonds

Hydrogen Bonds

Ionic Bonds

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6
Q

What do the below instructions describe:

  1. Place a 2cm3 of food in a test tube.
  2. Add 2 cm3 of sodium hydroxide solution at room temperature.
  3. Add a few drops of very dilute copper (II) sulfate solution (Biuret reagent)
  4. Observe and record colour change.
A

The Biuret test for proteins.

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7
Q

Identify the molecule

A

Amino acid

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8
Q

Name 3 fibrous type proteins

A

Collagen

Keratin

Silk

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9
Q

What is the monomer unit of a protein?

A

Amino acid

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10
Q

What do we call 2 amino acids chemically joined together?

A

Dipeptide

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11
Q

What is meant by a fibrous protein?

A

A protein made from many parallel polypeptide chains. These chains main form an α helix shape.

Fibrous proteins are usually insoluble in water.

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12
Q

Which colour does Biuret solution turn in the presence of protein?

A

Biuret changes from blue to purple.

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13
Q

Give 3 examples of enzymes

A

Amylase

Protease

Lipase

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14
Q

Which colour does Biuret reagent turn in the absence of protein?

A

It remains a blue colour

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15
Q

Identify the circled group

A

R group

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16
Q

Idenitfy the circled group

A

Amine group

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17
Q

What is meant by the tertiary structure of a protein?

A

When the α helix or β pleated sheets of the secondary protein structure are folded even more to give a complex, specific 3D structure.

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18
Q

What colour is Biuret reagent?

A

Blue

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19
Q

What is meant by a globular protein?

A

A protein made from few polypeptides, which form a spherical shape.

They are usually water soluble.

20
Q

Describe the hyodrogen bonds that hold the tertiary structure of a protein in place.

A

Individually weak and easily broken

Cumulatively provide some strength

21
Q

What is the polymer unit of a protein?

A

Polypeptide

22
Q

What is meant by the secondary structure of a protein?

A

When hydrogen bonds form between the C=O and -NH groups of the amino acids that form a polypeptide. This causes a polypeptide chain to fold into a 3D shape such as an α helix or β pleated sheet.

23
Q

How can a polypeptide be broken down into amino acids?

A

Hydrolysis

24
Q

What is meant by the primary structure of a protein?

A

The sequence of the amino acids in the polypeptide that forms the protein.

25
Q

How many naturally occurring amino acids are their?

A

20

26
Q

Name 3 globular type proteins

A

Enzymes

Hormones

Transport proteins

27
Q

What is the only difference between different amino acids?

A

the R-group

28
Q

What is the function of the protein keratin?

A

the main component of hard structures such as hair, nails, claws and hooves.

29
Q

Give an example of a transport protein

A

Haemoglobin in red blood cells

Cell membrane transport protiens

30
Q

Which type of bond forms between two amino acids?

A

Peptide bond

31
Q

A change of just 1 amino acid in the primary structure of a protein can cause what to happen?

A

A change in the shape of the protein.

The protein will stop working.

The protein will stop working as well.

32
Q

Every protein has a very _________ 3D shape, which is why they can carry out very ________ functions

A

specific

specific

33
Q

Name the 3 groups present on in an amino acids molecule.

A

Amino group (NH2)

Carboxyl group (COOH)

R-group

34
Q

Give 2 examples of hormones

A

Insulin

Oestrogen

35
Q

What is released when two amino acids chemically join together?

A

A water molecule (from condensation reaction)

36
Q

Identify the circled group

A

Carboxyl group

37
Q

How would you carry out the Biuret test for proteins?

A
  1. Place a 2cm3 of food in a test tube.
  2. Add 2 cm3 of sodium hydroxide solution at room temperature.
  3. Add a few drops of very dilute copper (II) sulfate solution (Biuret reagent)
  4. Observe and record colour change.
38
Q

Which type of reaction takes place during the polymerisation of amino acids?

A

Condensation reaction

39
Q

What is the function of the protein collagen?

A

the main component of connective tissue such as tendons and cartilage

40
Q

Which part of the amino acid structure is different in the 20 different amino acids.

A

The R group

41
Q

Give an example of a prosthetic group that is asociated with a quaternary protein structure.

A

The iron containing ‘Haem’ group in the haemoglobin protein.

42
Q

What is meant by the quaternary structure of a protein?

A

(Molecule contains) more than one polypeptide (chain);

There may also be prosthetic (non protein) groups attached to these proteins.

43
Q

Describe the structure of proteins

A
  1. Polymer of amino acids;
  2. Joined by peptide bonds;
  3. Formed by condensation;
  4. Primary structure is order of amino acids;
  5. Secondary structure is folding of polypeptide chain due to hydrogen bonding;
  6. Tertiary structure is 3-D folding due to hydrogen bonding and ionic/disulfide bonds;
  7. Quaternary structure is two or more polypeptide chains;
44
Q

Describe how proteins are digested in the gut

A
  1. Hydrolysis of peptide bonds;
  2. Endopeptidases break polypeptides into smaller peptide chains;
  3. Exopeptidases remove terminal amino acids;
  4. Dipeptidases hydrolyse/break down dipeptides into amino acids;
45
Q

describe how a peptide bond is formed between 2 AA to form a dipeptide

A

condensation reaction/loss water

between amine and carboxyl group

46
Q

describe how the secondary structure of a protein is produced

A

H bonds

between NH and C=O

forming beta pleat sheets or alpha helix

47
Q

2 proteins have same number and type of AA but different tertiary structire - why?

A

different sequence of AA

therefore

ionic/H/disulphide bonds form in different places

tim bio 2021/2022 (20 decks)

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