Proteins

Question 1

What elements are in proteins?

Answer 1

Carbon
Hydrogen
Oxygen
Nitrogen

Sometimes - Sulfur and Phosphorus

Question 2

What are the functions of proteins?

Answer 2

Catalysts 
Transporting substances around the body 
Movement of the body 
Cell recognition 
Transport across cell surface membrane 
Formation of connective tissue and structural components of the body 
Protection against foreign bodies 
Hormonal control

Question 3

Example of catalyst protein?

Answer 3

Enzymes

Question 4

Example of the proteins that transport substances around the body?

Answer 4

Haemoglobin

Question 5

Example of the proteins that help movement of the body?

Answer 5

Actin and myosin in muscles

Question 6

Example of the proteins for cell recognition?

Answer 6

Antigens

Question 7

Example of the proteins that help transport across cell membrane?

Answer 7

Intrinsic protein channels

Question 8

Example of the proteins that form connective tissue and structural components?

Answer 8

Keratin or collagen

Question 9

Example of the proteins for protection against foreign bodies?

Answer 9

Antibodies

Question 10

Example of the proteins for hormone control?

Answer 10

Insulin

Question 11

What is the monomer for proteins?

Answer 11

Amino acids

Question 12

What bonds are proteins held together by?

Answer 12

Peptide bonds

Question 13

How many different occurring amino acid monomer units are there? How many essential ones?

Answer 13

20

Only 8 are essential to build the others

Question 14

What are two amino acids joined together called?

Answer 14

Dipeptides

Question 15

What are many amino acids joined together called?

Answer 15

Polypeptides

Question 16

What is the structure of an amino acid?

Answer 16

An asymmetrical carbon atom bonded to 4 different groups

Carboxylic acid group - COOH
Amino Acid group - NH2
One hydrogen
R - variable group

Question 17

What are optical isomers?

Answer 17

They are mirror image isomers

Eg Alpha amino acids and Beta amino acids

Question 18

What amino acids are all living things made from?

Answer 18

Alpha amino acid

Question 19

What word are amino acids described as? What does this mean?

Answer 19

Amphoteric

The amino acids can act as both acids and bases

Question 20

How can the amino acids act as both acids and bases?

Answer 20

The amino group (NH2) can accept a hydrogen becoming NH3+ (alkaline)

The carboxylic acid group can lose a hydrogen ion and become COO- (acid)

Question 21

What reaction is used to form a dipeptide?

Answer 21

Condensation reaction

Question 22

What is removed in a condensation reaction?

Answer 22

Water

Question 23

What are the two products in a condensation reaction of two amino acids?

Answer 23

Dipeptide and water

Question 24

What are the types of structures of proteins?

Answer 24

Primary
Secondary
Tertiary
Quaternary

Question 25

What is primary structure? Bonds involved?

Answer 25

The sequence of amino acids in the polypeptide chain which determines the shape and function - an unbranched polypeptide chain Peptide bonds

Question 26

What is secondary structure? Bonds involved?

Answer 26

Polypeptide chains can twist into a 3D shape Weak hydrogen bonds

Question 27

What are the two types of secondary structures?

Answer 27

Alpha helix | Beta pleated sheet

Question 28

How does an alpha helix structure work?

Answer 28

Weak hydrogen bonds between NH group of one amino acid and the CO group of the neighbouring amino acid to cause the coil Making fibres

Question 29

What is alpha helix found in?

Answer 29

Keratin - hair and nails | Collagen - tendons

Question 30

How does the beta pleated sheet work?

Answer 30

Hydrogen bonds form parallel chains to produce a flat structure that then folds Creates great strength

Question 31

What is beta pleated sheet found in?

Answer 31

Silk

Question 32

What are the two types of proteins?

Answer 32

Fibrous | Globular

Question 33

What is the structure and use of fibrous proteins?

Answer 33

``` Made of long parallel fibres Linked by cross-bridges (very stable) Lots of molecules involved Regular and repetitive structure Insoluble ``` Used as structural molecules

Question 34

What is the structure and use of globular proteins?

Answer 34

``` Rounded molecules Fewer molecules used Unstable Irregular structure Soluble ``` Often used for metabolic functions

Question 35

What is tertiary structure? Bonds involved?

Answer 35

A precise 3D structure of protein formed by coiling of secondary proteins ``` Hydrogen bonds (weak, easily broken) Di-sulphide bridges (covalent bonds of sulphur atoms in the R group) Ionic bonds (between amino or carboxyl groups that aren’t involved in peptide bonds) - weak and broken by changes in pH ```

Question 36

What is quaternary structure? Bonds involved?

Answer 36

Large proteins consisting of a number of polypeptide chains together Also, Non-protein groups can be joined to the polypeptide called a prosthetic group Hydrogen Ionic Di-Sulphide bridges

Question 37

What do di-sulfide bridges do?

Answer 37

Joins or binds the polypeptide chains together

Question 38

How do you test for proteins?

Answer 38

Add equal volume of sodium hydroxide to the sample Add Biuret reagent (copper sulphate solution) If protein is present a purple/lilac colour will be indicted