The structure of proteins

Question 1

What elements do proteins contain?

Answer 1

Carbon, hydrogen, oxygen and nitrogen

Question 2

How many different amino acids are found in cells?

Answer 2

20

Question 3

Why are 5 of these 20 amino acids found in cells classified as non-essential?

Answer 3

Because our bodies can make them from other amino acids

Question 4

How many amino acids can we only obtain from food? (and therefore are essential)?

Answer 4

9

Question 5

Why are 6 of these 20 amino acids found in cells classified as conditionally essential?

Answer 5

because they are only required by infants and growing children

Question 6

What part of the amino acid determines its type?

Answer 6

The R group

Question 7

Draw the structure of an amino acid and label its different parts

Answer 7

d

Question 8

Describe how two amino acids undergo a condensation reaction

Answer 8

The amine (-NH2) group of one amino acid and the carboxyl group (-OOH) of the other react and join to a central carbon atom. It is able to do this because the hydroxyl (-OH) in the carboxylic acid group (-OOH) reacts with one hydrogen atom in the amine group (-NH2) of the other amino acid. A water molecule (H20) is produced and a peptide bond is formed between the two amino acids

Question 9

What is the name of the bond formed between two amino acids?

Answer 9

A peptide bond

Question 10

What is always produced in a condensation reaction?

Answer 10

Water

Question 11

What is the name of two amino acids joined together?

Answer 11

A dipeptide

Question 12

What is the name of two or more amino acids that have joined together?

Answer 12

A polypeptide

Question 13

What is the name of the enzyme that helps speed up the reaction for the condensation of amino acids?

Answer 13

peptidyl transferase

Question 14

Where is peptidyl transferase found?

Answer 14

In ribosomes

Question 15

What are ribosomes known for in regards to proteins?

Answer 15

Ribosomes are the site of protein synthesis

Question 16

How are polypetides able to fold into complex and unique structures?

Answer 16

The R groups on the amino acids are able to form bonds which fold the polypeptide chains. The different sequence of R groups make the chains fold in unique ways.

Question 17

What is the definition of the primary structure of proteins?

Answer 17

It is the sequence in which the amino acids are joined

Question 18

What is the definition of the secondary structure of proteins?

Answer 18

It is the formation of hydrogen bonds within the amino acid chain

Question 19

What are the two ways in which the formation of hydrogen bonds can alter the shape of the amino acid chain?

Answer 19

The hydrogen bonds may create a alpha helix type structure Or the hydrogen bonds may form between parallel polypeptide chains which would create a beta pleated sheet structure.

Question 20

What is the definition of the tertiary structure of proteins?

Answer 20

It is when the R groups interact with each other to enable further folding of the polypeptide chain.

Question 21

What are the 4 interactions that could occur between the R groups?

Answer 21

Hydrophobic and hydrophilic interactions Hydrogen bonds Ionic bonds Disulfide bonds (also known as disulfide bridges)

Question 22

What are Hydrophobic and hydrophilic interactions?

Answer 22

They are weak interaction between polar and non-polar R groups

Question 23

What are Hydrogen bonds?

Answer 23

They ate the weakest of the bonds formed and they are between the delta charges

Question 24

What are Ionic bonds?

Answer 24

These are stronger than hydrogen bonds and form between oppositely charged R-groups

Question 25

What are Disulfide bonds (also known as disulfide bridges)?

Answer 25

These are covalent and so the strongest of all the bonds. However, they only occur between R-groups that contain sulfur atoms

Question 26

What is the definition of the Quaternary structure of proteins?

Answer 26

It is the interaction between two or more identical or different protein chains (as opposed to within one protein chain). The interactions between the sub-units are the same in tertiary structure.

Question 27

How are peptides broken back into their individual amino acids?

Answer 27

A water molecule is added to break the peptide bond in a hydrolysis reaction. A enzyme named protease catalyses the reaction.