Amino acids

Question 1

What percentage of the body is made up of proteins?

Answer 1

18%

Question 2

What elements do all proteins contain?

Answer 2

C, H, O and N

Question 3

What is a structural use of proteins in the body?

Answer 3

Muscle fibres, hair (keratin) and bones

Question 4

What is a use of proteins in the immune system?

Answer 4

Antibodies

Question 5

What is a use of proteins in cells for reactions?

Answer 5

Enzymes

Question 6

What is a use of proteins in the nucleus?

Answer 6

Histone proteins which DNA is wound around

Question 7

What is a use of proteins in the blood?

Answer 7

Proteins such as albumin or some hormones such as insulin

Question 8

What is a use of proteins in membranes?

Answer 8

Channel proteins, receptor proteins and carrier proteins

Question 9

What is the polymer of proteins?

Answer 9

Polypeptides

Question 10

What is the monomer of proteins?

Answer 10

Amino acids

Question 11

How is a protein formed?

Answer 11

Amino acids are joined together at the ribosomes which make up the polypeptide which is then folded up into a protein

Question 12

How many different amino acids are there?

Answer 12

20

Question 13

How many proteins are essential?

Answer 13

9

Question 14

How many proteins are non-essential?

Answer 14

5

Question 15

How many proteins are conditionally essential (needed by growing children)?

Answer 15

6

Question 16

What is different between amino acids?

Answer 16

Their R group which each has different properties

Question 17

What parts of the amino acid don’t change?

Answer 17

The amino group and the carboxylic acid group

Question 18

What are the different types of R group?

Answer 18

They can be hydrophobic, hydrophilic, acidic, basic or charged

Question 19

Where are non-polar amino acids found?

Answer 19

Towards the inside of the protein molecule

Question 20

Where are polar amino acids found?

Answer 20

The outside of protein molecules

Question 21

What types of amino acids will dissolve in water?

Answer 21

Polar and charged (acidic and basic)

Question 22

What bond forms when amino acids are chemically joined together?

Answer 22

A peptide bond

Question 23

How are peptide bonds formed?

Answer 23

A covalent bond between the nitrogen of the amino group bonds to the carbon of a carboxylic acid on another. Also, one molecule of water is lost as the hydroxyl from the carboxylic acid reacts with a hydrogen in the amine group.

Question 24

What enzyme causes peptide bonds to be formed and where is it found?

Answer 24

Peptidyl transferase and it lies in the ribosome

Question 25

What are the steps for the biuret test?

Answer 25

1. 3cm of sample is mixed with equal volume of 10% NaOH solution.
2. 1% copper sulfate solution is added a few drops at a time until the solution turns blue.
3. The solution is mixed and left to stand for 5 minutes
4. If proteins are present, the solution turns from blue to lilac

Question 26

What are risks of NaOH?

Answer 26

It is corrosive and extremely hazardous to eyes so safety glasses are worn

Question 27

What are the risks of CuSO4?

Answer 27

It is harmful is swallowed and is dangerous for the environment so it use be disposed of safely.

Question 28

How does the biuret test indicate the presence of peptide bonds?

Answer 28

Copper (II) ions are reduced to Copper (I) ions which then form a complex with the nitrogen component in the peptide bon in alkaline conditions (due to NaOH). Then, the blue of the copper sulfate turns to violet when the complex forms and indicates if proteins are present.

Question 29

What is the stationary phase in the TLC method?

Answer 29

Thin silica gel layer applied to thin glass of metal sheet.

Question 30

What is the mobile phase in the TLC method?

Answer 30

Organic solvent

Question 31

What does TLC measure?

Answer 31

How different amino acids travel at different speeds according to their ability to make hydrogen bonds with the silica gel (stationary phase) and therefore their solubility in the solvent (the mobile phase)

Question 32

How do you carry out TLC?

Answer 32

1. Wearing gloves, draw a pencil line on the chromatography plate 2cm from the bottom and mark 4 equally spaced dots
2. The amino acid mixture in the locution is spotted onto the first dot using a capillary tube, allowed to dry, then spotted again.
3. Using a capillary tube, 2 different known amino acid are spotted onto the remaining 2 dots (to be used for comparison)
4. The plate is placed in a jar with no more than 1cm of solvent at the bottom and the jar is closed.
5. The plate is removed from the solvent once it has reached 2cm from the top and a pencil line is drawn to mark the old solvent front.
6. The plate is then sprayed in the fume cupboard with ninhydrin spray.
7. The amino acids react with the ninhydrin to form a purple/brown colour and the centre of the spot is marked with a pencil

Question 33

How a you calculate the Rf value of the unknown amino acid?

Answer 33

The same amino acid will always travel the same distance relative to the solvent under identical conditions so values for each amino acid can be calculated to identify them against known values.

Question 34

How do you calculate Rf?

Answer 34

Distance travelled by amino acid / distance travelled by solvent front

Question 35

Why are gloves worn?

Answer 35

To prevent bacteria transfer or contamination