Biological Molecules 4 - Amino acids and proteins

Question 1

What is an amino acid a monomer of?

Answer 1

protein

Question 2

What is the additional element that amino acids are made of?

Answer 2

nitrogen

Question 3

State the general formula of an amino acid

Answer 3

R.NH2CH.COOH

Question 4

What is the R group? give 5 points

Answer 4

the variable group and represents rest of molecule

there are 20 diff. variable groups

diff. for each amino acid

can be polar or nonpolar

can have a + or - charge

Question 5

Since there are 20 diff. amino acids in nature, how do they differ?

give three points

Answer 5

no. of amino acids
type of amino acids
sequence of amino acid

Question 6

How is a dipeptide formed and how? give 5 points

Answer 6

2 amino acids can join to form a dipeptide

resulting bond is a peptide bond

is a condensation reaction so H2O eliminated

involves NH2 group of an amino acid and COOH group of another

broken down by hydrolysis reaction

Question 7

What are polypeptides?

Answer 7

formed by many amino acids joined together by peptide bonds

are polymers

Question 8

What do polypeptides form and what do they all have?

Answer 8

form proteins

all have a primary and secondary structure

sometimes have tertiary and quaternary structures

Question 9

What does the primary structure of a protein refer to?

Answer 9

no. and sequence of amino acids in a polypeptide chain

contain peptide bonds

Question 10

How is a secondary structure formed from the primary structure and what are the 2 types?

Answer 10

the primary structure of a polypeptide can coil to form either an alpha-helix or a beta-pleated sheet.
the alpha-helix is held in a spiral shape by hydrogen bonds
the beta-pleated sheet is a flat zigzag structure also held by hydrogen bonds e.g silk

Question 11

What are the 2 fibrous alpha helices and what are they shaped like?

Answer 11

keratin - found in hair and nails
collagen - found in connective tissue and skin
rope-like strands.

Question 12

How is the tertiary structure formed from the secondary structure?

Answer 12

the sec. struc. folds to give complex 3D shapes held by bonds that form between R groups of some amino acids in the polypep. chain

Question 13

What type of proteins are in the tertiary structure?

Answer 13

globular e.g enzymes, hormones and plasma

Question 13

Give the 5 bonds and interactions in the tertiary structure

Answer 13

hydrogen bonds - between O and OH
ionic bonds - between oppositely charged R groups
disulphide bridges - between S atoms (cysteine)
Hydrophobic R group interactions - inside of protein
Hydrophilic - outside

Question 14

Describe the quaternary structure

Answer 14

occurs when more than one polypep. chain with a tertiary structure combine to form a larger protein complex
the bonds involved are similar to the tertiary structure
sometimes associated with non-protein groups (prosthetic groups) e.g haemoglobin
heam groups in haemoglobin are prosthetic groups which contain iron

Question 15

What are the features of fibrous proteins?

Answer 15

tough, non-specific and insoluble

Question 16

What are the features of globular proteins?

Answer 16

compact and folded into spherical molecules
specific shape
soluble in water