Proteins

Question 1

what is the monomer of proteins?

Answer 1

amino acids

Question 2

what is the polymer of amino acids? what re they made from?

Answer 2

polypeptide

- constructed from same set of 20 amino acids

Question 3

what is the structure of protein?

Answer 3

one or more polypeptides folded into specific 3-D structure

Question 4

how many different amino acids are there?

Answer 4

20

Question 5

what are some functions of proteins?

Answer 5

• speed up chemical reactions
• provide structural support
• provide transport
• are hormones
• allow for movement
• defend our bodies against foreign invaders

Question 6

what do all amino acids have in common?

Answer 6

-have the same common structure, with differing R-groups

Question 7

what do r-groups determine?

Answer 7

Chemical properties of the R-groups determines the unique characteristics of an amino acid

Question 8

what are the components of an amino acid?

Answer 8

• amino group (N1 H2)
• central carbon (with a hydrogen atom attached)
• carboxyl group (C with double bonded O and single bonded hydroxyl)
• varying r-groups

Question 9

which amino acids are hyrdophobic? hydrophilic?

Answer 9

Hydrophobic –> Nonpolar amino acids

Hydrophilic –> Polar amino acids; and charged amino acids

Question 10

how are 2 amino acids linked? what kind of bond do they form? what is this kind of bond between 2 amino acids called?

Answer 10

by removal of water molecule

• covalent
• peptide bond

Question 11

what does the backbone of a polypeptide consist of?

Answer 11

-amino group, carboxyl group, central carbon and hydrogen

Question 12

where does the peptide bond form between amino acids?

Answer 12

between the hydroxyl (of the carboxyl) and an hydrogen of the amino group –> to form water molecule (tehrefor removing H and OH

Question 13

how are functional proteins formed?

Answer 13

one or more polypeptides must fold into a specific shape

Question 14

What determines a protein’s unique shape?

Answer 14

The amino acid sequence

-Shape determined and maintained by interactions between the different amino acids

Question 15

what does a proteins structure determine? how many levels of structure do proteins have? what are they?

Answer 15

it’s function

• proteins have 4 levels of structure
  1. primary
  2. secondary
  3. tertiary
  4. quaternary

Question 16

in the backbone of polypeptide what kind of bond is formed between the C, O, and N? what does this result?

Answer 16

• polar covalent bonds
• results in atoms that are unfairly sharing electrons, therefore they have partial charges –> with partial charges they can form hydrogen bonds

Question 17

Primary protein structure:

1. what is the shape
2. how is it held together
3. what kind of proteins do you find this in?
4. how many polypeptides are involved

Answer 17

1. linear sequence of amino acids
2. held together by peptide bonds (covalent bonds between monomers)
3. all proteins have this level of structure
4. one polypeptide

Question 18

Secondary protein structure:

1. what is the shape/structures
2. how is it held together
3. what are the 2 types of secondary structures?
4. how many polypeptides are involved

Answer 18

1. coiled and/or folded into particular shapes - local folded structures that form within a polypeptide
2. hydrogen bonds forming between between atoms in polypeptide backbone (not r-groups)
3. Alpha-helix and beta-pleated
4. one polypeptide

Question 19

what is an alpha helix?

Answer 19

a coil held together by hydrogen bonds between backbones of amino acids (is made of only one polypeptide)

Question 20

what are beta-pleated sheets?

Answer 20

two or more regions within a single polypeptide lying side by side, connected by hydrogen bonds between parts of the two parallel polypeptide backbones

Question 21

Tertiary protein structure:

1. what is the shape
2. how is it held together
3. how many polypeptides are involved

Answer 21

1. overall rounded or globule shape
2. held together by interactions between r-groups within single polypeptide. can have many different types of interactions occurring at once
3. single polypeptide which is all folded up

Question 22

what are 4 types of interactions that may be occurring between r-groups and which kinds of amino acids are involved?

Answer 22

1. hydrophobic interactions –> non-polar amino acids
2. hydrogen bonds –> polar amino acids
3. ionic bonds –> charged amino acids
4. covalent bonds (disulfide bridges) –> between sulfhydryl groups

Question 23

Quaternary protein structure:

1. how is it held together
2. what kind of proteins do you find this in?
3. how many polypeptides are involved

Answer 23

1. held together by interactions between r-groups of different polypeptides
2. Only proteins made up of multiple sub units have this level of structure
3. 2 or more polypeptide chains interacting with one another

Question 24

what are fibrous proteins? what is often their function? give an example

Answer 24

• polypeptide chains that are arranged in long strands or sheets
• often for structural purposes
• eg. collagen - has primary, secondary and quaternary levels of structure

Question 25

what are globular proteins? what is often their function? give an example

Answer 25

-polypeptide chains that folded into spherical shapes -often are enzymes, transport proteins, receptor proteins, or hormones -eg. hemoglobin - has primary, tertiary, and quaternary levels of structure

Question 26

what are 3 factors that affect a proteins structure? changes in these conditions may cause what?

Answer 26

1. Temperature 2. pH 3. Salt concentration - may cause a protein to denature (destroy the characteristic properties of) and lose its function

Question 27

how is protein structure affected by temperature? which levels of structure are effected by increase in temp, why? which level of structure is relatively unaffected, why?

Answer 27

- temp causes an increase/decrease of movement of particles. - Heat increases the kinetic energy and causes the molecules to vibrate so rapidly and violently that hydrogen and hydrophobic bonds are disrupted - cold decreases the kinetic energy and once cold enough, causes proteins to become solid and stop their functions - levels 2, 3, and 4 --> because held together with hydrogen and hydrophobic interactions (which are weak) - level 1 --> because held together with covalent bonds which are strong

Question 28

how is protein structure affected by change in pH? which kinds of bonds will changes in pH affect?

Answer 28

- when there is an increase/decrease in the amount of pH, it changes how many hydrogen ions there are in the environment - Increase in H+ → decrease in OH- - Increase in OH- --> decrease H+ - Will disrupt ionic and hydrogen bonds, and hydrophobic interactions

Question 29

which levels of structure will be effected by change in pH, why? which level of structure will remain relatively unaffected, why?

Answer 29

- level 2 --> because held together with hydrogen bonds | - level 3 and 4 --> because held together with mix of hydrogen, ionic, and hydrophobic bonds/interactions

Question 30

how is protein structure effected by change in salt concentration? which kinds of bonds will changes salt concentration affect?

Answer 30

- when there is an increase/decrease in the salt concentration, it changes how many hydrogen ions there are in the environment - Will disrupt ionic and hydrogen bonds, and hydrophobic interactions

Question 31

which levels of structure will be effected by change in salt concentration, why? which level of structure will remain relatively unaffected, why?

Answer 31

- level 2 --> because held together with hydrogen bonds | - level 3 and 4 --> because held together with mix of hydrogen, ionic, and hydrophobic bonds/interactions