proteins

Question 1

what are the monomers for protein

Answer 1

amino acids

Question 2

all proteins contain which elements

Answer 2

-nitrogen
-carbon
-hydrogen
-oxygen

some contain sulfur

Question 3

why do proteins have a specific role

Answer 3

because each protein has a specific shape

Question 4

amino acids can link together in a chain of peptide bonds to form…

Answer 4

a polypeptide

Question 5

what bond links/binds together amino acids

Answer 5

peptide bond

Question 6

how many different types of amino acids are there

Answer 6

20, and they all have the same general formula

Question 7

what is the general formula for an amino acid

Answer 7

R-CH(NH2)-COOH

H R O
I I II
N - C - C
I I I
H H OH

Question 8

give the structure of an amino acid

Answer 8

-each amino acid contains a central alpha carbon to which a nitrogen containing amine group (H2N) and a carboxyl group (COOH) are attached
-the R group indicates the variable group (20 different options)

Question 9

R groups can be….

Answer 9

-positively charged
-negatively charged
-hydrophilic attracted to water
-hydrophobic repelled by water

Question 10

how is a peptide bond formed

Answer 10

the hydroxyl group from one amino acid combines with a hydrogen atom from the amino group in the second amino acid to form a water molecule which is removes and a bond is formed

Question 11

what is formed when two amino acids join together

Answer 11

dipeptide

Question 12

if there is 10 amino acids present how many peptide bonds are there

Answer 12

9, always one less than number of amino acids

Question 13

what is a protein

Answer 13

a polymer made up of the monomers amino acids- chain of amino acids

Question 14

what is the primary structure

Answer 14

-number and sequence and order of amino acids in a polypeptide chain
-proteins are different from each other because their primary structures, amino acids sequence and numbers are different.

Question 15

what is the secondary structure

Answer 15

-it is a 2D shape
- polypeptide folds into alpha helixes or/and beta pleated sheets
- held together by many weak hydrogen bonds between the C=O groups of the carboxyl group of one amino acid and H in the amine group of another

Question 16

what is the tertiary structure

Answer 16

-further folding of secondary structure/polypeptide chain into a specific unique 3D shape
-the R groups on the amino acids in polypeptide chain determine how the chain folds into it’s specific 3D shape

Question 17

why is the tertiary structure essential to a protein’s function

Answer 17

• the shape of protein determines how it interacts with other molecules which is necessary for it to carry out its specific function

Question 18

what is the quaternary structure

Answer 18

-protein is made up of two or more polypeptide chains joined together
-sometimes there may be a prosthetic group (non-protein component) in a protein
-haemoglobin is an example and its a globular protein

Question 19

what are globular proteins

Answer 19

-they are functional proteins
-approx spherical shape
-soluble in water because globular proteins have got hydrophilic amino acids on their surface so that the hydrophilic R groups can interact with water molecules
-they are transport proteins such as haemoglobin, lipase,DNA polymerase and insulin

Question 20

give examples of globular proteins

Answer 20

-they are transport proteins such as haemoglobin, lipase,DNA polymerase and insulin

Question 21

what are fibrous proteins

Answer 21

-are structural proteins
-often play a structural role for example in bones or tendons or in the walls of blood vessels such as arteries
-fibrous proteins tend to form long rope-like molecules and 3 alpha helixes
-they have a large proportion of amino acids with hydrophobic R groups therefore they are insoluble in water
-they are tough and strong

Question 22

give 3 examples of fibrous proteins

Answer 22

collagen
keratin
elastin

Question 23

why are antibodies only effective against a specific pathogen

Answer 23

-antigens on pathogens have a specific shape/3D structure
-antibodies are complementary to the antigen so they bind to it and form antibody-antigen complex

Question 24

when do proteins denature

Answer 24

only at high temps and large changes to pH

Question 25

where are the bonds in the tertiary structure formed

Answer 25

ionic bonds (quite weak bonds) form between oppositely charged R groups
-weak hydrogen bonds form between C=O and NH of adjacent amino acids
-disulphide bonds only sometimes form if there is Sulfur in the R groups, and they are strong bonds formed between cysteine amino acids only