Proteins

Question 1

Describe the structure of an amino acid. (F)

Answer 1

• amine group (-NH2)
• carboxyl group (-COOH)
• alpha-carbon (C)
• R-group (variable)

Question 2

State how many amino acids occur in life.

Answer 2

20

Question 3

Explain how the variety of amino acids leads to a wide range of dipeptides and very quickly to an incredible variety of polypeptide chains.

Answer 3

• Dipeptide: 400 possible combinations (20^2)
• Tripeptide: 8000 possible combinations (20^3)
• etc.

Question 4

Define the term “polypeptide chain”.

Answer 4

Chain of three or more amino acids

Question 5

Describe how one end of a polypeptide chain differs from the other end.

Answer 5

One end is an amine group (-NH2) which has basic properties, and the other end is a carboxyl group (-COOH) and has acidic properties.

Question 6

Define the term “primary structure” of a protein. (F)

Answer 6

The sequence of amino acids.

Question 7

Define the term “secondary structure” of a protein and describe the two different types. (F)

Answer 7

The folding of the polypeptide chain into an alpha helix (coiled) or beta pleated sheet (flat).

Question 8

Define the term “tertiary structure” of a protein. (F)

Answer 8

The 3D shape of a polypeptide chain.

Question 9

Explain how the primary structure of a protein determines its tertiary structure.

Answer 9

The R-groups on the amino acids affect the bonding in the tertiary structure.

Question 10

Define the term “quaternary structure” of a protein.

Answer 10

When two or more polypeptides associate.

Question 11

Define the term “globular protein”. (F)

Answer 11

Spherical, water-soluble protein.

Question 12

Define the term “prosthetic group”. (F)

Answer 12

Non-protein component of a conjugated protein

Question 13

Give an example of a conjugated protein (the bloody one).

Answer 13

Haemoglobin

Question 14

Give an example of an enzyme (the H2O2 one ;) ).

Answer 14

Catalase

Question 15

Give an example of a peptide hormone (the sugary one).

Answer 15

Insulin

Question 16

Give 3 examples of fibrous proteins.

Answer 16

• collagen
• elastin
• elastin

Question 17

Describe the structure of collagen.

Answer 17

• 3 polypeptide chains
• triple helix
• every third amino acid is glycine
• hydrogen bonds

Question 18

Describe the structure of keratin.

Answer 18

• lots of cysteine (with S)

- disulfide bridges (degree of disulfide bonds determines flexibility)

Question 19

Describe the structure of elastin.

Answer 19

• cross-linked structure

- covalent bonds between lysine amino acids

Question 20

Compare the structure of globular and fibrous proteins.

Answer 20

• G is spherical

- F is long

Question 21

Compare the properties of globular and fibrous proteins.

Answer 21

• G is soluble

- F is insoluble

Question 22

Compare the functions of globular and fibrous proteins.

Answer 22

• G acts as enzymes and hormones

- F acts as structural components

Question 23

Identify the key structural components of haemoglobin.

Answer 23

• 4 polypeptide chains
• 2 alpha helices, 2 beta pleated sheets
• 4 haem prosthetic groups (Fe2+)

Question 24

State the properties of haemoglobin.

Answer 24

Haem group combines reversibly with an oxygen molecule

Question 25

State the functions of haemoglobin.

Answer 25

Transports oxygen in red blood cells

Question 26

Identify the key structural components of catalase.

Answer 26

- 4 polypeptide chains | - 4 haem prosthetic groups (Fe2+)

Question 27

State the properties of catalase.

Answer 27

Can interact with H2O2 with haem groups

Question 28

State the functions of catalase.

Answer 28

Speeds up breakdown of H2O2 formed from metabolic reactions

Question 29

Identify the key structural components of insulin.

Answer 29

3 polypeptide chains

Question 30

State the properties of insulin.

Answer 30

- soluble | - precise shape

Question 31

State the functions of insulin.

Answer 31

Regulation of blood glucose concentration

Question 32

Describe the properties of collagen.

Answer 32

- flexible | - tough

Question 33

Describe the location of collagen.

Answer 33

- skin - tendons - ligaments - nervous system

Question 34

Describe the functions of collagen.

Answer 34

Connective tissue

Question 35

Describe the properties of keratin.

Answer 35

- strong - inflexible - insoluble

Question 36

Describe the location of keratin.

Answer 36

- hair - skin - nails

Question 37

Describe the functions of keratin.

Answer 37

- protection | - adhesion

Question 38

Describe the properties of elastin.

Answer 38

- flexible | - strong

Question 39

Describe the location of elastin.

Answer 39

- walls of blood vessels | - alveoli in lungs

Question 40

Describe the functions of elastin.

Answer 40

- allow flexibility to expand when needed - allow to return to normal size - strength and elasticity

Question 41

What holds the primary structure of a protein held together? (F)

Answer 41

Peptide bonds

Question 42

What holds the secondary structure of a protein held together? (F)

Answer 42

Hydrogen bonds

Question 43

What holds the tertiary structure of a protein held together? (F)

Answer 43

- hydrogen bonds - ionic bonds - disulfide bridges - hydrophobic-hydrophilic interactions

Question 44

What holds the quaternary structure of a protein held together? (F)

Answer 44

- hydrogen bonds - ionic bonds - disulfide bridges - hydrophobic-hydrophilic interactions

Question 45

Define the term "protein".

Answer 45

One or more polypeptides with a specific function

Question 46

Define the term "fibrous protein". (F)

Answer 46

Long, insoluble, structural protein.

Question 47

Define the term "conjugated protein". (F)

Answer 47

Globular protein that contains a prosthetic group