Proteins

Question 1

What are proteins made up of?

Answer 1

Amino acids

Question 2

What elements make up a protein?

Answer 2

C
H
O
N
(S)

Question 3

How many naturally occurring amino acids are there?

Answer 3

20

Question 4

What is the basic structure of an amino acid?

Answer 4

R 
                      I         
H  —  N  —  C  —  C  =  O 
           I          I         I 
          H        H        OH

Question 5

How are 2 amino acids joined (functional groups) ?

Answer 5

Amino group of one

Carboxyl group of another

Question 6

What type of reaction joins 2 amino acids?

Answer 6

Condensation

Question 7

What is the bond name formed between 2 amino acids?

Answer 7

Peptide bond

Question 8

What is the name of 2 amino acids joined together?

Answer 8

Dipeptide

Question 9

What are the type of bonds which form the 3D structure of the protein?

Answer 9

Hydrogen bonds
Iconic bonds
Disulphide bridges

Question 10

What do the type of bonds formed between amino acid chain depend on?

Answer 10

The R group

Question 11

Which atoms form hydrogen bonds in amino acid chains?

Answer 11

Delta negative charge of O (lone pairs)

Delta positive charge of H

Question 12

What affects hydrogen bonds?

Answer 12

Temperature

pH

Question 13

Which 2 molecules allow the formation of disulphide bridges?

Answer 13

Cysteine molecules

Question 14

How does a disulphides bridge occur?

Answer 14

Oxidation reaction between 2 sulfur groups

Question 15

What is the primary structure of a protein?

Answer 15

The sequence of amino acids that make up the polypeptide chain help together by peptide bonds

Question 16

What is the secondary structure of a protein?

Answer 16

The arrangement of the polypeptide chain into a regular repeating structure held together by hydrogen bonds

Question 17

Give examples of secondary structure.

Answer 17

a helix

B pleated sheet

Question 18

What type of protein is prone to having B pleated sheets as a secondary structure?

Answer 18

Fibrous proteins

Question 19

What is tertiary structure?

Answer 19

A level of 3D organisation imposed on top of the secondary structure of many proteins

Question 20

What type of protein is prone to having tertiary structures?

Answer 20

Globular proteins

Question 21

What is the quaternary structure of a protein?

Answer 21

Only seen in proteins consisting of several polypeptide chains

Question 22

Give examples of quaternary structure.

Answer 22

Important enzymes

Blood pigment haemoglobin

Question 23

What is the name of changes in protein structure leading the bonds to break?

Answer 23

Denaturing

Question 24

What are the properties of fibrous proteins?

Answer 24

Little or no tertiary structure
Long parallel chains with occasional cross-linkages into fibres
Insoluble in water
Very tough

Question 25

What is the function of fibrous proteins?

Answer 25

Structural proteins Appear in connective tissues Keratin in hair

Question 26

Give an example of a fibrous protein.

Answer 26

Collagen

Question 27

What is the function of collagen?

Answer 27

Gives strength to tendons, ligaments, bones and skin

Question 28

What is the primary structure of collagen?

Answer 28

3 polypeptide chains Each up to 1000 amino acids long Repeating sequences of glycine and 2 other amino acids

Question 29

Which amino acids make up collagen?

Answer 29

Glycine and 2 others | Often proline and hydroxyproline

Question 30

How are the amino acids arranged in collagen?

Answer 30

Three a - chains are arranged in a unique triple helix | Held together by very large no of hydrogen bonds

Question 31

What disease may result in the triple helix of collagen not forming?

Answer 31

Genetic disease osteogenesis imperfecta

Question 32

What are the properties of globular proteins?

Answer 32

Complex tertiary (and sometimes quaternary) structure Spherical shapes Large size

Question 33

Why are globular proteins insoluble?

Answer 33

They are too big

Question 34

What is unusual about globular proteins solubility?

Answer 34

Is expected to dissolve in water (ionic properties of amino and carboxyl group) form a colloid instead

Question 35

What is the name of the molecule formed by globular proteins in water?

Answer 35

A colloid

Question 36

What is the function of globular proteins?

Answer 36

Hold molecules in position in the cytoplasm

Question 37

Give examples of globular proteins.

Answer 37

Antibodies Enzymes Some hormones Haemoglobin

Question 38

How is haemoglobin held together?

Answer 38

Disulphides bridge

Question 39

What are conjugated proteins?

Answer 39

Protein molecules that join with/ conjugate to another molecule called a prosthetic group

Question 40

Give an example of a conjugated protein (including the prosthetic group)

Answer 40

Haemoglobin (Iron containing prosthetic group) Chlorophyll (Magnesium containing prosthetic group)

Question 41

What are glycoproteins?

Answer 41

Proteins with a carbohydrate prosthetic group

Question 42

What is the problem with glycoproteins?

Answer 42

Carbohydrate part of molecule helps them hold lots of water makes it harder for protein digesting enzymes to break them down

Question 43

Give examples of glycoproteins used in the body.

Answer 43

Lubricants - mucus and synovial fluid

Question 44

Why are glycoproteins good lubricants?

Answer 44

Water holding properties make them slippery and viscous - reduces friction

Question 45

What are lipoproteins?

Answer 45

Proteins conjugated with lipids

Question 46

What is the role of lipoproteins?

Answer 46

Important in the transport of cholesterol in blood

Question 47

What is the difference between HDLs and LDLs?

Answer 47

HDLs contain more protein - so they are denser

Question 48

What are the types of lipoproteins found in blood?

Answer 48

High density lipoproteins | Low density lipoproteins

Question 49

What is the test for proteins?

Answer 49

Biuret test | Blue solution —> purple solution

Question 50

What are amino acids?

Answer 50

The building blocks of proteins

Question 51

What is a peptide bond?

Answer 51

The bond formed by condensation reactions between amino acids

Question 52

What are fibrous proteins?

Answer 52

Proteins that have long, parallel polypeptide chains with the occasional cross-linkages that form into fibres, but with little tertiary structure

Question 53

What is a disulphide bridge?

Answer 53

A strong covalent bond formed as a result of an oxidation reaction between sulfur groups in cysteine

Question 54

What are globular proteins?

Answer 54

Large proteins with complex tertiary and sometimes quaternary structures, folded into spherical (globular) shapes

Question 55

What is a prosthetic group?

Answer 55

The molecule that is incorporated in a conjugated protein