Proteins

Question 1

What are proteins also called?

Answer 1

Polypeptides/polymers

Question 2

How are proteins structured?

Answer 2

Long chains of amino acids

Question 3

What do all amino acids contain?

Answer 3

• carbon
• hydrogen
• oxygen
• nitrogen

Question 4

What do many amino acids also contain?

Answer 4

Sulfur

Question 5

How is an amino acid structured?

Answer 5

An amino group (NH2)
A central C with a H
A variable R group attached to the central C
A carboxyl group (COOH)

Question 6

How many different R groups are there giving the same number of different amino acids?

Answer 6

20

Question 7

What is the simplest amino acid?

Answer 7

Glycine: R=H

Question 8

What is the the more complex amino acid example?

Answer 8

Cysteine- R=CH^2SH

Question 9

What bonds amino acids?

Answer 9

Peptide bond

Question 10

How is a peptide bond formed?

Answer 10

Condensation reaction

Question 11

What do two amino acids combine to form?

Answer 11

A dipeptide

Question 12

What groups does a peptide bond form between?

Answer 12

One amino acid’s carboxyl group and the other’s amino group.

Question 13

Three or more amino acids joined by a peptide form what?

Answer 13

Polypeptide

Question 14

What is the primary structure of a polypeptide?

Answer 14

A long chain of amino acids

Question 15

What happens if the sequence changes due to DNA mutation in a primary structure?

Answer 15

The protein will be non-functional

Question 16

What are the two secondary structures and how are they formed?

Answer 16

The polypeptide chain twists to form

• an alpha helix
• or a beta pleated sheet

Question 17

What maintains the secondary structure’s shape?

Answer 17

Hydrogen bonds between the peptide bonds.

Question 18

What make up proteins?

Answer 18

Amino acid monomers

Question 19

What is a tertiary structure’s shape?

Answer 19

Secondary structure folded into a specific 3d shape

Question 20

What 3 types of bonds hold together tertiary structure?

Answer 20

• Hydrogen bonds between R groups containing O- and H+
• ionic bonds between R groups containing oppositely charged ions.
• disulfide bonds between sulfur containing R groups. Very stable, occur least often.

Question 21

What are hydrophobic interactions?

Answer 21

Interactions between two non-polar R gtoups. Within protein, amino acids with non polar R groups move away from aqueous environment to form hydrophonic centre at protein molecule interior.

Question 22

How are quaternary formed?

Answer 22

2 or more polypeptide chains combined. Held by same bonds as tertiary.

Question 23

What is an example of quaternary and what is it made up of?

Answer 23

Haemoglobin. 4 tertiary bonded together- 2 alpha and 2 beta chains

Question 24

What are the two protein types and their functions?

Answer 24

Fibrous (structural)

Globular (biochemical)

Question 25

What structure do fibrous proteins have?

Answer 25

Secondary

Question 26

How are fibrous formed/structured?

Answer 26

Polypeptide chains twisted to form long strands

Question 27

Are fibrous insoluble or soluble?

Answer 27

Insoluble- can't dissolve

Question 28

What is the structure of the fibrous protein collagen?

Answer 28

3 intertwined chains

Question 29

What is the function of the fibrous protein collagen?

Answer 29

Main connective tissue in body, found in ligaments, tendons and cartilage

Question 30

What is the fibrous protein keratin's structure?

Answer 30

Two intertwined chains

Question 31

What are keratin's two functions?

Answer 31

- main component of hard structures such as hair, nails and hooves - part of skin cells, preventing pathogen entry.

Question 32

What structure do globular proteins have?

Answer 32

Tertiary or quaternary

Question 33

Is globular soluble or insoluble?

Answer 33

Soluble

Question 34

What are the possible biochemical functions of globular proteins? (4)

Answer 34

- Enzymes - transport proteins such as haemoglobin and myoglobin. - hormones- such as oestrogen and insulin. - antibodies

Question 35

What is denaturing?

Answer 35

If the bonds that maintain a protein's shape are broken, the protein will stop working properly= denatured.

Question 36

What factors can denature proteins?

Answer 36

``` Changes in:- -temp -pH -salt concentration (Specific conditions vary from protein to protein). ```

Question 37

What effect does denaturing have on fibrous?

Answer 37

Loses structural strength

Question 38

What effect does denaturing have on globular?

Answer 38

Becomes insoluble and inactive

Question 39

What is the test for proteins?

Answer 39

Add biuret agent (copper sulfate and sodium hydroxide). | A change from pale blue to lilac/purple = positive.