Proteins and Enzymes

Question 1

How many protein molecules are in a cell?

Answer 1

42 million

Question 2

How are amino acids joined?

Answer 2

• joined covalently by peptide bonds
• peptide: shortened parts of a protein
• proteins: “polypeptide chains”

Question 3

What is the structure of proteins?

Answer 3

• complex and 3 dimensional
• primary, secondary, tertiary and quaternary

Question 4

What is the primary structure of proteins?

Answer 4

• base determinant of protein shape and function
• amino acid sequence of a protein linked to a human chain

Question 5

What is the secondary structure of proteins?

Answer 5

• peptides fold in complex ways
• the force responsible for this is the hydrogen bond created by a hydrogen atom with partial positive charge and an atom with a partial negative charge
• though hydrogen bonds are much weaker than covalent bonds, the abundance of hydrogen atoms in proteins gives rise to many connectors that stabilise the secondary structure

Question 6

What is the tertiary structure of proteins?

Answer 6

• conformation of an entire polypeptide chain
• also stabilised by hydrogen bonds but also uses other interactions:
  
  • electrostatic bonds
  • van der waals interaction
  • disulfide bonds
  • hydrophobic interaction

Question 7

What are electrostatic bonds?

Answer 7

occur between positive and negatively charged groups

Question 8

What is a van der waals interaction?

Answer 8

a non-covalent attraction due to movement of ions at atomic or molecular orbituals

Question 9

What are disulfide bonds?

Answer 9

form between sulfhydryl groups of the amino acid cysteine

Question 10

What is denaturation?

Answer 10

environmental factors, such as heat or acidity can alter or break these forces

Question 11

What is the quaternary structure of protein?

Answer 11

While tertiary structure describes conformation of whole polypeptide chains, many proteins contain subunits that link together via the same interactions already discussed - this is referred to as a quaternary structure

Question 12

What are enzymes?

Answer 12

• enzymes accelerate metabolic reactions
• reactants are called substrates
• there is almost no biological substance that is not a substrate of an enzyme
• generally named after their substrate or the type of reaction they catalyse

Question 13

What are the main features of enzymes?

Answer 13

• they speed up reactions
• they display high specificity
• their catalytic power is regulated

Question 14

What is an active site?

Answer 14

attraction is at a small area of the surface of the enzyme called the active site

Question 15

What are cofactors and coenzymes?

Answer 15

• to catalyse reactions, many enzymes need the presence of non protein chemical entities, or cofactors in their active sites
• tend to be metal ions and organic compounds