Lesson 9.1 - Structure of proteins

Question 1

What elements do all proteins contain?

Answer 1

Hydrogen, Oxygen, Hydrogen, Nitrogen

Question 2

What are peptides?

Answer 2

Polymers made up of amino acids

Question 3

What forms a protein?

Answer 3

One or more polypeptides arranged as complex macromolecules.

Question 4

What results in different amino acids?

Answer 4

The variable R-group.

Question 5

Conditionally essential amino acids?

Answer 5

6: only needed by infants and growing children

Question 6

Essential amino acids?

Answer 6

6: Can only be obtained by what we eat

Question 7

Non-essential amino acids?

Answer 7

5: Can by formed from other amino acids in the body

Question 8

Synthesis of peptides to form a dipeptide?

Answer 8

• Amino acids join when the amine and carboxylic acid groups connected to the central carbon atoms react.
• R-groups not involved at this point
• Hydrogen in amine group of one amino acid reacts with the hydroxyl group in carboxylic acid group of another amino acid.
• Peptide bond is formed between amino acids and water produced.

Question 9

When many amino acids join together by peptide bonds?

Answer 9

Polypeptide forms.

Question 10

What enzyme catalyses protein synthesis?

Answer 10

Peptidyl transferase.

Question 11

How do long polypeptide chains form proteins?

Answer 11

The different R-groups interact with each other (R-group interactions). Form different types of bonds.

These bonds lead to long chains of amino acids forming complex structures (proteins).

Question 12

Different R-groups?

Answer 12

Different combinations of R-groups lead to the formation of different proteins.
- Structure of proteins is specific to the function within living organisms.

Question 13

Primary structure:

Answer 13

Specific sequence in which amino acids are joined in a polypeptide.

Question 14

What directs the primary structure of proteins?

Answer 14

Directed by information carried within DNA.

Question 15

Bonds involved in the primary structure?

Answer 15

Peptide bonds

Question 16

What does primary structure influence?

Answer 16

• How polypeptide folds to give final shape.

Question 17

What is the secondary structure of proteins?

Answer 17

The oxygen, hydrogen, and nitrogen atoms of the basic, repeating structure of the amino acids interact.

Question 18

Role of hydrogen bonds in secondary structure of proteins?

Answer 18

Hydrogen bonds may form within the amino acid chain, pulling it into a coil shape called an alpha helix.
OR
Peptide chains can lie parallel to each other, joined by hydrogen bonds, forming sheet-like structures. Pattern formed by individual amino acids appears pleated (beta pleated sheet).

Question 19

Summary of secondary structure?

Answer 19

Result of hydrogen bonds and forms at regions along long protein molecules. Depends on the amino sequence.

Question 20

Tertiary structure

Answer 20

Folding of a protein into its final shape. It often includes sections of secondary structure.

Question 21

How does tertiary structure work?

Answer 21

Coiling or folding of sections of proteins into their secondary structures brings R-groups of different amino acids closer together. Close enough to interact so further folding of these sections will occur.

Question 22

What different types of interactions occur between R-groups?

Answer 22

• hydrophobic and hydrophilic reactions –> weak interactions between polar and non-polar R-groups.
• Hydrogen bonds –> weakest bonds formed
• Ionic bonds –> stronger than hydrogen bonds and form between oppositely charged R-groups
• Disulfide bonds/bridges - covalent and strongest of the bonds. Only form between R-groups that contain sulphur atoms.

Question 23

Quaternary structure: result

Answer 23

Association of two or more individual proteins called subunits.

(Same as between tertiary structure). Just between proteins.

Question 24

What types of subunits interact?

Answer 24

Can be identical or different.

Question 25

Enzymes:

Answer 25

Consist of 2 identical subunits

Question 26

Insulin:

Answer 26

Two different subunits

Question 27

Hydrophobic and hydrophilic interactions:

Answer 27

Proteins are assembled in the aqueous environment of the cytoplasm.

The way proteins fold depends on whether the R-groups are hydrophobic or hydrophilic.

Hydrophobic groups are on the inside of the molecule (shielded from the water in the cytoplasm). Hydrophilic groups are on the outside of the molecule.

Question 28

Catalyst for the reverse reaction (break down of peptide bonds)?

Answer 28

Proteases

Question 29

The breaking down of peptide bonds?

Answer 29

Hydrolysis reaction –> water added
Reforms the amine and carboxylic acid groups.

Question 30

Non-proteins in the quaternary structure?

Answer 30

Prosthetic groups

Question 31

What is a protein with a prosthetic group called?

Answer 31

Conjugated proteins