Biological Molecules - Proteins

Question 1

What polymer is an amino acid the monomer of?

Answer 1

A protein (polypeptide)

Question 2

How many amino acids occur naturally in proteins?

Answer 2

20

Question 3

How many amino acids are essential? (can only be obtained through food)

Answer 3

9

Question 4

What does it mean that amino acids are amphoteric?

Answer 4

Amino acids can act as both an acid and a base.

Amino acids therefore work as buffer solutions.

Question 5

What is the central atom of an amino acid?

Answer 5

Carbon

Question 6

What are the 4 groups of an amino acid?

Answer 6

Amine group (-NH2)
Carboxyl group (-COOH)
Hydrogen group (-H)
R group (variable chemical group)

Question 7

Draw the structure of an amino acid.

Answer 7

See bio book

Question 8

What is a polypeptide?

Answer 8

A chain of multiple amino acids.

Question 9

What is a protein?

Answer 9

one or multiple folded and modified polypeptide chains bonded together

Question 10

What bonds form between amino acids and between which groups?

Answer 10

Peptide bonds between C of carboxyl group and N of amine group.

Question 11

What kind of reaction breaks the bond between two amino acids?

Answer 11

Hydrolysis reaction (water used up)

Question 12

What kind of reaction forms a peptide bond?

Answer 12

Condensation reaction (water produced)

Question 13

What is the primary structure of a protein?

Answer 13

The specific sequence of amino acids in a polypeptide chain.

This decides the structure and the function of the protein.

Question 14

What are the two structures formed as part of the secondary structure of a protein?

Answer 14

Alpha-helix

Beta-pleated sheet

Question 15

What is an alpha-helix?

Answer 15

When a polypeptide chain stabilises by coiling into a cylindrical shape held together by hydrogen bonds between carboxyl and amine groups.

Question 16

What is a beta-pleated sheet?

Answer 16

Polypeptide chains become linked in parallel flat strands joined by hydrogen bonds between carboxyl and amine/hydroxyl groups.

Question 17

What is the tertiary structure of a protein?

Answer 17

The secondary structures fold up to form a precise 3D structure.
The R-groups on amino acids result in further folding.

Question 18

What is the quaternary structure of a protein?

Answer 18

Multiple proteins interact to form a larger molecule.
May have identical or non-identical subunits.
Made of more than one polypeptide chain.
May contain prosthetic groups (non protein groups)

Question 19

What is an example of a prosthetic group in a protein?

Answer 19

Haemoglobin contains proteins attached to haem groups.

Question 20

What are the 4 types of bonds between R-groups of polypeptides that form their precise 3D structure?

Answer 20

Disulphide bonds
Ionic bonds
Hydrophobic interactions
Hydrogen bonding

Question 21

What kind of bond is a disulphide bond and between which amino acids does it form?

Answer 21

Covalent bond between two cysteine monomers

Disulphide bridge

Question 22

Which types of protein bonding are the first to break when a protein is denatured due to temperature or PH?

Answer 22

Ionic bonds

Hydrogen bonds

Question 23

What groups on amino acids do ionic bonds form between?

Answer 23

Ionic bonds form between amine and carboxyl groups, ionising them.

Question 24

What are hydrophobic interactions and to what amino acids do they occur?

Answer 24

Hydrophobic interactions involve amino acids with non-polar (hydrophobic) R groups.
Hydrophobic R groups twist the protein to take position in the centre of a loop, away from water.

Question 25

In proteins, what do hydrogen bonds form between?

Answer 25

Delta negative oxygen and delta positive hydrogen.

Question 26

What are the features of a fibrous protein?

Answer 26

Little/no tertiary structure.
Long, parallel polypeptide chains.
Cross linkages at intervals forming long fibres or sheets.
Usually insoluble.
Usually play a structural role.
Very strong.

Question 27

What are 4 examples of fibrous proteins?

Answer 27

Keratin
Elastin
Collagen
Myosin

Question 28

Where is collagen found in the body?

Answer 28

Skin, bones, cartilage, blood vessels

structural protein

Question 29

What is the structure of collagen?

Answer 29

3 polypeptide chains in a helical shape to form a “rope”.

Held together by hydrogen bonds.

Question 30

What feature of collagen’s primary structure allows it to be so strong?

Answer 30

Small glycine R-group allows the closeness of polypeptide chains, increasing the strength of the intermolecular forces.

Question 31

What is the general structure of a globular protein?

Answer 31

Globular proteins have complex tertiary and quaternary structures.
They are folded into globular (spherical) shapes.

Question 32

What role do globular proteins usually play in the cell?

Answer 32

Roles in metabolic reactions (enzymes)

Question 33

Are globular proteins usually soluble or insoluble and why?

Answer 33

Globular proteins are usually soluble as all the hydrophobic R-groups are in the centre of the 3D structure.

Question 34

What are 4 examples of globular proteins?

Answer 34

Enzymes, haemoglobin, insulin, actin

Question 35

What is the structure of haemoglobin?

Answer 35

Made of 4 polypeptide chains.
2 identical alpha chains and 2 identical beta chains.
Each polypeptide contains a prosthetic haem group, so haemoglobin is a conjugated protein.

Question 36

What ion is contained in a haem group and what is its function?

Answer 36

Haem group contains an iron (Fe2+) ion at its centre. This combines with oxygen at high oxygen concentrations.

Question 37

How many haem groups does haemoglobin have and how many oxygen molecules can it carry?

Answer 37

4 haem groups

4 oxygen molecules

Question 38

What is a conjugated protein?

Answer 38

A protein containing a prosthetic group