12.2 Proteins and Enzymes

Question 1

What elements do all amino acids contain?

Answer 1

Nitrogen, carbon, hydrogen and oxygen

Question 2

What do some proteins contain?

Answer 2

Sulphur

Question 3

What do each protein have?

Answer 3

A specific shape and therefore a specific function

Question 4

What bonds are found in proteins?

Answer 4

Peptide bonds

Question 5

What monomers make up proteins?

Answer 5

Amino acids

Question 6

What is the general structure of an amino acid?

Answer 6

It has a central carbon atom, to which nitrogen containing an amine group and carboxyl group are attached. The different R group is what makes amino acids different.

Question 7

R groups can be…

Answer 7

Positively charged, Negatively charged, Hydrophilic or Hydrophobic

Question 8

What is a dipeptide?

Answer 8

A dimer made by two amino acids joined together by a condensation reaction (forming a peptide bond)

Question 9

What are the four protein structures?

Answer 9

Primary structure
Secondary structure
Tertiary structure
Quaternary structure

Question 10

Describe the primary structure

Answer 10

• it is the number and sequence of amino acids in a polypeptide chain
• it ONLY involves peptide bonds

Question 11

What is the primary structure responsible for?

Answer 11

The overall structure of protein - changing one amino acid may alter the structure and function of the protein

Question 12

What does the primary structure look like?

Answer 12

Question 13

What do polypeptide chains fold into? (secondary structure)

Answer 13

Alpha helices and Beta pleated sheets

Question 14

What bonds are found in secondary structure?

Answer 14

Weak hydrogen bonds

Question 15

Why are secondary structures stable and strong?

Answer 15

They contain many hydrogen bonds which provide strength in numbers

Question 16

What is the structure of an Alpha Helix and a Beta Pleated Sheet?

Answer 16

Question 17

What does the R group do?

Answer 17

It determines the different shapes of proteins

Question 18

What bonds are found in the tertiary structure?

Answer 18

Weak hydrogen bonds, ionic bonds and disulphide bridges

Question 19

Why is the tertiary structure important?

Answer 19

It determines how the protein will interact with other molecules

Question 20

Describe the quaternary structure?

Answer 20

Two or more polypeptide chains joined together

Question 21

What is the tertiary structure of a protein?

Answer 21

Question 22

What are the two types of quaternary structures?

Answer 22

Globular (functional) and Fibrous (structural)

Question 23

Describe a globular protein

Answer 23

• It is either tertiary or quaternary
• Compact and folded into spherical molecules
• Soluble in water

Question 24

Describe a fibrous protein

Answer 24

• Made from a-helices twisting around each other
• Chains have cross linkages (mainly Hydrogen bonds) forming long strands
• Strong, tough and insoluble

Question 25

What can denature proteins?

Answer 25

High temperature and change in pH

Question 26

How does temperature denature proteins?

Answer 26

Increasing temperature increases the kinetic energy of molecules, therefore causing more vibrations. These vibrations can break the weak hydrogen bonds in the secondary and tertiary structure - changing the overall shape of the protein

Question 27

How does change in pH denature proteins?

Answer 27

It breaks the ionic bonds between the R groups in the tertiary structure

Question 29

What is the tertiary structure important for?

Answer 29

Folding the peptide chain into a specific 3D structure