Proteins

Question 1

What are the monomers of proteins?

Answer 1

Amino Acids

Question 2

What are the polymers that are combined to make proteins?

Answer 2

Polypeptides

Question 3

How are dipeptides formed?

Answer 3

When two amino acids join together.

Question 4

When are polypeptides formed?

Answer 4

When more than two amino acids join together.

Question 5

What is the general structure of amino acids?

Answer 5

• Amino Group ( -NH2 )
• Carboxyl Group ( - COOH )
• Hydrogen Group ( - H )
• R Group, this is the variable side group, it can be one of 20 naturally occurring amino acids.

Question 6

What reaction joins together amino acids?

Answer 6

Condensation reactions.

Question 7

What bond is formed between amino acids?

Answer 7

Peptide Bonds

Question 8

How are polypeptides formed?

Answer 8

• Amino acids are linked together by condensation reactions to form polypeptides.
• A molecule of water is released during the reaction.

Question 9

How is the water molecule formed in the formation of polypeptides?

Answer 9

• -OH from the carboxyl Group of the first amino acid.
• -H from the amino group of the second amino acid.
These combine to form water.

Question 10

Where does the peptide bond link two amino acids?

Answer 10

Between:
• Carbon of the first amino acid.
• Nitrogen of the second amino acid.

Question 11

What reaction breaks down polypeptides?

Answer 11

Hydrolysis.

Question 12

What is polymerisation?

Answer 12

Polymerisation is the process of reacting monomer molecules together in a chemical reaction to form polymer chains, in the case of protein, a polypeptide.

Question 13

What are the four structures of a protein?

Answer 13

• Primary
• Secondary
• Tertiary
• Quaternary

Question 14

What is the primary structure?

Answer 14

Sequence of amino acids in a polypeptide chain.

Question 15

What is the primary structure determined by?

Answer 15

DNA

Question 16

What does the primary structure determine?

Answer 16

Determines the shape of the protein, and therefore also determines its function.

Question 17

What is the secondary structure?

Answer 17

• Hydrogen Bonds form in the polypeptide.
• Formation of bonds causes the long polypeptide chain to be twisted into a 3-D shape structure, which can be either: Alpha Helix or Beta Pleated Sheet.

Question 18

What are the two structure that the secondary structure can twist into?

Answer 18

• Alpha Helix

* Beta Pleated Sheet

Question 19

What bonds form between the amino acids in the polypeptide chain ( Secondary Structure )?

Answer 19

• Hydrogen bonds

Question 20

How do the hydorgen bonds form?

Answer 20

• -NH and -C=O Groups on either side of every peptide bond.

* Due to the charges of the groups, they will form ionic bonds.

Question 21

What is the charge of the -NH group?

Answer 21

H of -NH group has an overall positive charge

Question 22

What is the charge of the -C=O group?

Answer 22

O of the group has an overall negative charge.

Question 23

What occurs in the tertiary structure?

Answer 23

Alpha helix of the secondary structure. is twisted and folded even further to provide a more complex 3-D structure.

Question 24

What are the bonds in the tertiary structure?

Answer 24

• Disulfide Bridges ( Very strong, not easily broken )
• Ionic Bonds ( Weaker than bridges, but broken by changes in pH )
• Hydrogen Bonds ( Weak but numerous )

Question 25

( Tertiary Structure ) How do disulfide bridges form?

Answer 25

• When two molecules of the cysteine group come close, the sulfur atom i one cysteine bonds to the sulfur atom in the other.

Question 26

( Tertiary Structure ) How do Ionic bonds form?

Answer 26

Formed between carboxyl and amino groups, that are not involved in forming peptide bonds.

Question 27

What is the Quaternary Structure?

Answer 27

This structure is the way the polypeptide chains are assembled together, this applies to polypeptide chains with multiple polypeptides

Question 28

What is the test for proteins?

Answer 28

Biuret Test: • Place a sample of the solution into a test tube, and add an equal volume of sodium hydroxide solution at room temperature. • Add a few drops of dilute copper ( II ) sulphate solution and mix. • A purple colour indicates the presence of peptide bonds, and therefore indicates the presence of a protein. • If it remains blue, there is no protein present.

Question 29

What are some functions of proteins?

Answer 29

* Enzymes * Antibodies * Transport Proteins * Structural Proteins.

Question 30

What are structural proteins?

Answer 30

* They are physically strong. | * Consist of long polypeptide chains parallel to each other.

Question 31

What is an example of transport proteins?

Answer 31

* Channel proteins in cell membranes. * They contain hydrophobic and hydrophillic amino acids, which cause the protein to fold up and form a channel. * These proteins transport molecules and ions across membranes.

Question 32

What are antibodies?

Answer 32

* Proteins involved in the immune response. | * Consist of two light and two heavy polypeptide chains bonded together.