3.1.4 Proteins

Question 1

What are the monomers that make up proteins called?

Answer 1

Amino acids

Question 2

What is the formula for the amine group in an amino acid molecule?

Answer 2

NH2

Question 3

What is the formula for the carboxyl group in an amino acid molecule?

Answer 3

COOH

Question 4

What is the R group?

Answer 4

It represents a carbon containing side chain

Question 5

How many amino acids are common in all organisms?

Answer 5

20

Question 6

How many essential amino acids are there?

Answer 6

8

Question 7

What is the name of the reaction that bonds amino acids?

Answer 7

Condensation

Question 8

What type of bond is formed during the condensation reaction between two amino acids?

Answer 8

Peptide bonds

Question 9

What is a dipeptide?

Answer 9

The protein formed by the condensation of two amino acids

Question 10

What is a polypeptide?

Answer 10

The protein formed by the condensation of many amino acids

Question 11

Name a property of a functional protein

Answer 11

Contain one or more polypeptide

Question 12

What are the 6 elements found in proteins?

Answer 12

Carbon 
Hydrogen
Oxygen
Nitrogen
Sulphur 
Phosphorus

Question 13

What protein catalyses reactions?

Answer 13

Enzymes

Question 14

What protein transports substances around the body?

Answer 14

Haemoglobin

Question 15

What protein controls movement of the body?

Answer 15

Actin and myosin in muscles

Question 16

Which proteins function is cell recognition?

Answer 16

Antigens

Question 17

What transport across cell surface membranes?

Answer 17

Intrinsic protein channels

Question 18

Which proteins form connective tissue and structural components of the body?

Answer 18

Keratin

Collagen

Question 19

Which proteins protect against invasion by foreign bodies?

Answer 19

Antibodies

Question 20

Which proteins are responsible for hormonal control?

Answer 20

Hormones (eg insulin)

Question 21

Why is there an endless variety of protein structures?

Answer 21

The 20 different amino acid monomer units can be assembled in any order

Question 22

What do you call the variable group of an amino acid?

Answer 22

R group

Question 23

What is an optical isomer?

Answer 23

Mirror image molecules made from alpha and beta amino acids

Question 24

Amino acids can act as both acids and bases, what is this called?

Answer 24

Amphoteric

Question 25

Why are amino acids described as amphoteric?

Answer 25

The amino group can accept a hydrogen which makes it act as a base whereas the carboxyl group donates hydrogen which makes it act as an acid

Question 26

Which group of an amino acid acts as a base?

Answer 26

Amino group

Question 27

Which group of an amino acid acts as an acid?

Answer 27

Carboxyl group

Question 28

What is removed when peptide bonds are formed?

Answer 28

Water

Question 29

What is primary structure?

Answer 29

The sequence of amino acids which determines its shape and function

Question 30

What is secondary structure?

Answer 30

Polypeptide chains can twist into a 3D shape, forming an alpha helix or beta pleated sheet

Question 31

What is tertiary structure?

Answer 31

Precise 3D structure of protein formed by the coiling of secondary proteins

Question 32

What is quaternary structure?

Answer 32

Large proteins can have many polypeptide chains associated together
Non protein groups can join to polypeptides (prosthetic group)
Having both makes a quaternary structure

Question 33

What bonds are involved in primary structure?

Answer 33

Hydrogen bonds

Question 34

What bonds are involved in secondary structure?

Answer 34

Hydrogen bonds

Question 35

What bonds are involved in tertiary structure?

Answer 35

Hydrogen bonds
Ionic bonds
Disulphide bridges

Question 36

What bonds are involved in quaternary structure?

Answer 36

Hydrogen bonds
Ionic bonds
Disulphide bridges

Question 37

Describe hydrogen bonding.

Answer 37

Weak

Strong in large numbers

Question 38

Describe ionic bonding.

Answer 38

Weak
Between any carboxyl and amino groups that are not involved in forming peptide bonds
Easily broken by changes in pH

Question 39

Describe disulphide bridges.

Answer 39

Covalent

Strong

Question 40

Describe the test for proteins.

Answer 40

Biuret test
Add equal parts sodium hydroxide and solution X to a test tube
Add a few drops of copper sulphate and mix
Purple/lilac indicates a protein is present (detects peptide bonds)
No change indicated protein is not present

Question 41

What do you call a non-protein group starched to polypeptides?

Answer 41

Prosthetic group

Question 42

How do hydrogen bonds hold successive coils in an alpha helix?

Answer 42

Fibres are formed by the bonds between the NH group in one amino acid and the CO group of another

Question 43

Describe beta pleated sheets.

Answer 43

Hydrogen bonds between each parallel chain
It is a flat structure that folds
It has great strength (eg silk)

Question 44

What are the two types of protein?

Answer 44

Globular- metabolic functions

Fibrous- structural materials

Question 45

Describe globular proteins?

Answer 45

Rounded molecules
Alpha helix’s and beta pleated sheets
Unstable
Irregular primary structure
Conservative sequence and length between species/individuals
Soluble (suspension)

Question 46

Describe fibrous proteins?

Answer 46

Parallel strands
Lots of beta pleated sheets OR lots of alpha helixes
Stable
Regular, repetitive primary structure
Variable sequences and length between species/individuals
Insoluble