Proteins

Question 1

Proteins always contain

Answer 1

-nitrogen
-carbon
-hydrogen
-oxygen

Question 2

Many proteins may also contain

Answer 2

-sulphur and phorphorus

Question 3

How are proteins made

Answer 3

-polymers made out of monomers called amino acids

Question 4

Chain of amino acids is called

Answer 4

polypeptides

Question 5

how many different amino acids are used to make up proteins

Answer 5

20

Question 6

basic structure of amino acids

Answer 6

-an amino group (-NH2) at one end
-carboxyl group at the other end (COOH)
-hydrogen atom
-R group (different in each amino acid)

Question 7

at ph7 the amino acid has what

Answer 7

-positive and negative charge

Question 7

Name for an amino acid that has a positive and negative group

Answer 7

Zwitterion

Question 8

What are linear sequences of amino acids

Answer 8

proteins

Question 9

How is a peptide bond formed

Answer 9

-amino group of one amino acid reacts with the carboxyl group of another and eliminates water (condensation)
-bond between them is the peptide bond
-resulting compound is a dipeptide

Question 10

Primary structure of a protein

Answer 10

-polypeptide chains can have up to 20 amino acids

Question 11

Primary structure is determined by

Answer 11

-base sequence on one strand of the DNA molecule

Question 12

Secondary structure

Answer 12

-shape the polypeptide chain forms as a result of hydrogen bonding
-twisted into 3d shape
-spiral shape - alpha helix
-beta pleated sheet is another form

Question 13

Keratin proteins

Answer 13

-high proportion of alpha helix and the protein fibroin

Question 14

Silk has a high proportion of

Answer 14

-beta pleated sheet

Question 15

Tertiary structure

Answer 15

-the alpha helix of secondary protein folded and twisted to give complex compact 3d structure

Question 16

The tertiary structure is maintained by

Answer 16

-hydrogen bonds
-ionic bonds
-disulphide bonds
-hydrophobic interactions

Question 17

what bonds are important in giving globular proteins

Answer 17

-hydrogen
-disulphide
-ionic

Question 18

Quaternary structure

Answer 18

-some polypeptides are not functional unless combined
-can be associated with non-protein groups and form large, complex molecules like haemoglobin

Question 19

Fibrous proteins

Answer 19

-long, thin shape
-insoluble in water so they have structural functions in bones
-polypeptides are in parallel chains or sheets with many cross linkages forming long fibres (keratin-hair)
-strong, tough

Question 20

Collagen is needed in

Answer 20

-tendons because they provide strength and the toughness needed

Question 21

A single fibre is normally called a

Answer 21

-tropocollagen that consists of 3 identical polypeptide chains twisted around each other like a rope
-3 are linked by hydrogen bonds, stable

Question 22

Globular proteins are

Answer 22

-compacted and folded into spherical molecules which makes them insoluble in water

Question 23

Functions of globular proteins

Answer 23

-enzyme antibodies
-plasma, proteins and hormones

Question 24

Haemoglobin consists of

Answer 24

-four folded polypeptide chains at the centre of each is an iron containing group - haem

Question 25

Test for proteins

Answer 25

-few drops of biuret reagent is added
-if protein is present colour change from blue -> purple
-more concentrated the proteins the darker the colour