2.4 Proteins

Question 1

What is the monomer that forms proteins?

Answer 1

Amino Acids

Question 2

What is the structure of an amino acid?

Answer 2

Central carbon bound to:

• An amine group (NH2)
• A carboxyl group (COOH)
• A hydrogen atom
• A variable side chain (R)

Question 3

How many amino acids exist universally?

Answer 3

20

Question 4

What do we call a chain of amino acids?

Answer 4

Polypeptide

Question 5

Are polypeptides polar?

Answer 5

They differ in structure, some are some are not

Question 6

What type of bond holds amino acids together?

Answer 6

(Covalent bonds) called peptide bonds

Question 7

How are polypeptides broken down?

Answer 7

Hydrolysis

Question 8

Between which groups do peptide bonds form?

Answer 8

Carboxyl and Amine group

Question 9

What is the primary structure of amino acid sequences?

Answer 9

The order

Question 10

What is the secondary structure of amino acid sequences?

Answer 10

How the amino acids are folded

Question 11

What is the tertiary structure of amino acid sequences?

Answer 11

The overall 3D configuration

Question 12

What is the quaternary structure of amino acid sequences?

Answer 12

The structure including any other polypeptide strands which may or not be present

Question 13

What are the two stable configurations of amino acid secondary structures?

Answer 13

Alpha helices

Beta-pleated sheets

Question 14

Describe alpha helix structure

Answer 14

Amino acids fold in a coil/ spiral arrangement

Question 15

Describe beta-pleated sheets

Answer 15

Directionally-oriented staggered strand conformation

Question 16

How do alpha helices and beta pleated sheets form?

Answer 16

Hydrogen bonds form between non-adjacent amine and carboxyl groups

Question 17

What determines the tertiary strucutre?

Answer 17

Interactions between the variable chains

Question 18

Give an example of a protein with a quaternary structure

Answer 18

Haemoglobin

4 polypeptide chains and an iron-containing haeme group

Question 19

What is a prosthetic group?

Answer 19

A non amino-acid component that is part of a protein

Question 20

Define denaturation

Answer 20

Is a structural change in a protein that results in the loss (usually permanently) of its biological properties

Question 21

Which two factors can cause denaturation?

Answer 21

pH

temperature

Question 22

How does temperature cause denaturation?

Answer 22

High levels of thermal energy can break the hydrogen bonds

Question 23

How does pH cause denaturation?

Answer 23

The pH can alter the charge of the protein, altering it’s solubility and shape

Question 24

What is the process of converting a gene sequence into a polypeptide?

Answer 24

Transcription

Translation

Question 25

How many polypeptides do genes typically code for?

Answer 25

Usually 1 but there are exceptions

Question 26

When do genes code for more than one polypeptide?

Answer 26

• Genes may be alternatively spliced to generate multiple polypeptide variants
• Genes encoding tRNA sequences are transcribed but never translated
• Genes may be mutated and consequently produce an alternative polypeptide sequence

Question 27

What is the proteome?

Answer 27

The totality of proteins expressed within a cell, tissue or organism at a certain time

Question 28

Why may a proteome be significantly larger than the number of genes?

Answer 28

• Alternative splicing (creating more than one protein from a single gene)
• Modification after translation to promote further variants

Question 29

What purposes may a protein serve?

Answer 29

Structure
Hormones
Immunity
Transport
Sensation
Movement
Enzymes