1.6 Proteins

Question 1

How is protein made?

Answer 1

Amino acids (monomers) > polypeptides (polymers) > protein

Question 2

What elements does a protein contain?

Answer 2

1. a central carbon
2. amino group (—NH2) — a basic group
3. carboxyl group (—COOH) — an acidic group
4. hydrogen atoms
5. R (side) group — a variety of different chemical groups

Question 3

How many different amino acids are there?

Answer 3

20

Question 4

What can be formed when combing two amino acid monomers?

Answer 4

A dipeptide

Question 5

What is the process called when combining two amino acid monomers to form a dipeptide?

Answer 5

Condensation

Question 6

How is water made when combining two amino acids?

Answer 6

By combining an —OH from the carboxyl group of one amino acid with an —H from another amino acid.

Question 7

What bond is linking two amino acids?

Answer 7

A peptide bond

Question 8

How can a peptide bond be broken down?

Answer 8

By hydrolysis (with addition of water)

Question 9

What is the process called when many amino acid monomers are joined together?

Answer 9

Polymerisation

Question 10

What is a polypeptide?

Answer 10

Condensation of many amino
acids

Question 11

What does a functional protein contain?

Answer 11

One or more polypeptides

Question 12

What levels of structure does protein have?

Answer 12

1. primary structure
2. secondary structure - pleated sheet (折片) or alpha helix
3. tertiary structure
4. quarternary structure

Question 13

Why is it important that primary structures of proteins are correct?

Answer 13

Because the primary structure of protein determines all properties of a protein, so if the primary structure of protein goes wrong, the entire protein will go wrong.

Question 14

Which level of protein structure are amino acids?

Answer 14

Primary structure

Question 15

What bond is formed in a polypeptide chain?

Answer 15

Hydrogen bond

Question 16

What does the hydrogen bond cause?

Answer 16

It causes the polypeptide chain to be twisted into a 3D shape

Question 17

How is alpha helix formed?

Answer 17

They are formed as a result of hydrogen bonds forming between the —OH from the carboxyl group of one amino acid and the —H from another amino acid.

Question 18

How is pleated sheet formed?

Answer 18

They are formed between sections of the same or different polypeptide chains.

Question 19

How are tertiary structure of protein formed?

Answer 19

By twisting and folding the secondary protein structure even more to give a more complex 3D structure of protein.

Question 20

What bonds are maintaining the tertiary structure of protein?

Answer 20

1. disulfide bonds
2. ionic bonds
3. hydrogen bonds

Question 21

Are disulfide bonds strong or weak?

Answer 21

Strong and not easily broken

Question 22

How do ionic bonds form? Are they strong or weak?

Answer 22

They are formed between a carboxyl group and an amino group that are not involved in forming peptide bonds. They are weak and are easily broken by changes in pH.

Question 23

How many hydrogen bonds are there? Are they strong or weak?

Answer 23

They are numerous (很多) but they are weak and easily broken.

Question 24

Why are the tertiary structures of proteins important when it comes to the function of proteins?

Answer 24

Because it makes each proteins distinctive (獨特的) and allows it to be recognised.

Question 25

What does the quaternary structure of protein contains?

Answer 25

1. different polypeptide chains
2. non-protein
   ☆ they form a large, complex protein molecule ☆

Question 26

What is used to test for protein?

Answer 26

Biuret solution

Question 27

How will the colour of the food sample change?

Answer 27

Blue > purple