30.2- PEPTIDES, POLYPEPTIDES, AND PROTEINS

Question 1

What do amino acids link together to form?

Answer 1

peptides

Question 2

What are molecules containing up to about 50 amino acids referred to as?

Answer 2

polypeptides

Question 3

What is it called when there are more than 50 amino acids?

Answer 3

proteins

Question 4

Examples of naturally occurring proteins? (4)

Answer 4

enzymes
wool
hair
muscles

Question 5

What is the functional group of an amide?

Answer 5

-CONH2

Question 6

What can the amine group of one amino acids react with a carboxylic acid group of another to form?

Answer 6

amide linkage -CONH-

Question 7

What are compounds formed by the linkage of amino acids called?

Answer 7

peptides

Question 8

What is a peptide with two amino acids called?

Answer 8

dipeptide

Question 9

What groups does a dipeptide retain?

Answer 9

retains -NH2 and -CO2H groups and so can react further to give tri- and tetra-peptides, and so on

Question 10

What is the primary structure of a protein?

Answer 10

fixed sequence of amino acids

Question 11

What type of polymers are polypeptides and proteins?

Answer 11

condensation polymers

Question 12

Why are polypeptides and proteins condensation polymers?

Answer 12

as a small molecule eliminated as each link of chain forms

Question 13

What happens when a protein or peptide is boiled with HCl of conc. 6moldm-3 for about 24hrs?

Answer 13

breaks down to mixture of all amino acids that made up original protein or peptide

Question 14

What happens to the peptide linkages when a protein or peptide is boiled in HCl of conc. 6moldm-3 for about 24 hrs?

Answer 14

all peptide linkages hydrolysed by acid

Question 15

How is the complex shape of proteins held in position?

Answer 15

by hydrogen bonds + other intermolecular forces + sulfur-sulfur bonds

Question 16

Example of how the shape of proteins are vital to their functions?

Answer 16

enzymes + structural materials in living things

Question 17

What structure do many proteins have?

Answer 17

helical

Question 18

What is the helix of proteins held by?

Answer 18

hydrogen bonding

Question 19

What is another structure of proteins other than the helix?

Answer 19

pleated sheet

Question 20

What is wool?

Answer 20

protein fibre with helix held together by hydrogen bonds

Question 21

What happens to the hydrogen bonding and fibre when wool is gently stretched?

Answer 21

hydrogen bonds stretch + fibre extends

Question 22

When releasing wool after it has been stretched, what does this allow?

Answer 22

allows hydrogen bonds to return to their normal length + fibre returns to its original shape

Question 23

What can washing wool at high temps do?

Answer 23

permanently break hydrogen bonds + garment may permanently lose its shape

Question 24

How can the amino acids in a protein chain bond together (3)

Answer 24

hydrogen bonding
ionic attractions
sulfur-sulfur bonds

Question 25

What three levels of structure do all proteins have?

Answer 25

primary, secondary and tertiary

Question 26

What is the primary structure of a protein held by?

Answer 26

covalent bonding

Question 27

As the primary structure of a protein is held by covalent bonding, what is its stability like?

Answer 27

relatively stable

Question 28

What is the secondary structure of a protein?

Answer 28

protein may form helix or folded sheet

Question 29

What is the secondary structure held in place by?

Answer 29

hydrogen bonding

Question 30

What is the strength of hydrogen bonding like on comparison to covalent bonds?

Answer 30

hydrogen bonds much weaker than covalent bonds

Question 31

How can the secondary structure of proteins be disrupted?

Answer 31

by gentle heating or changes in pH

Question 32

What is the tertiary structure?

Answer 32

α-helix or β-pleated sheet being folded into a three dimensional shape

Question 33

What is the tertiary structure held in place by?

Answer 33

mixture of hydrogen bonding, ionic interactions and sulfur-sulfur bonds

Question 34

What shapes do most proteins fold into?

Answer 34

globular shapes

Question 35

Example of techniques used to determine the secondary and tertiary structures of proteins and what it can do?

Answer 35

X-ray diffraction- can locate actual positions of atoms in space

Question 36

What is the first step in determining the primary structure?

Answer 36

find out number of each type of amino acid present in protein

Question 37

How is the process if determining the primary structure of protein done?

Answer 37

protein refluxed with 6moldm-3 HCl process called hydrolysis breaks amide bonds between amino acids and results in mixture containing all individual amino acids in original protein