[OLD] Biological Molecules - Proteins

Question 1

What is the monomers for a protein?

Answer 1

amino acid

Question 2

What is an amino acid made from?

Answer 2

an amino group (at one end) - NH2
a carboxylic acid group (at the other end) - COOH
a central carbon 
a hydrogen
an R group

Question 3

How many different amino acids are there?

Answer 3

20

Question 4

What is the only difference between the different amino acids?

Answer 4

the R group

Question 5

what are essential amino acids?

Answer 5

amino acids that can’t be made in the body and have to be obtained from the body

Question 6

What is the primary structure of a protein?

Answer 6

the sequence if amino acids in a polypeptide chain (determined by DNA sequence)

Question 7

what is the secondary structure of a protein?

Answer 7

the H bonds between NH2 and COOH groups pull the polypeptide into either an alpha helix or a beta pleated sheet conformation

Question 8

what is the tertiary structure of a protein?

Answer 8

interaction between R groups fold the polypeptide into a specific 3D shape

Question 9

what are the 4 different interactions between R groups?

Answer 9

hydrogen bonds
ionic bonds
disulphide bridge
hydrophilic / hydrophobic interactions

Question 10

describe hydrogen bonds interactions

Answer 10

slightly positive region on one R group forms a bond to slightly negative region on another R group

Question 11

describe ionic bonds interactions

Answer 11

positively charged R group attracted to negatively charged R group

Question 12

describe disulphide bridge interactions

Answer 12

a specific covalent bond that forms between the sulphur containing R groups of 2 cysteine amino acids

Question 13

describe hydrophobic / hydrophilic interactions

Answer 13

some R groups are non-polar and hydrophobic. The polypeptide chain will bend to position these R groups in the centre of the molecule away from the surrounding water. Other R groups will be polar/charged and hydrophilic. They want to interact with water and so the polypeptide will twist so that they are positioned to the outside of the ,olé use in contact with the surrounding water.

Question 14

what is the quaternary structure of a protein?

Answer 14

The interactions between two different polypeptide chains (if a protein consists of more than one polypeptide chain). These bonds may be H bonds, ionic bonds, disulphide bonds or hydrophobic / hydrophilic interactions.

Question 15

4 different types of specialised proteins

Answer 15

enzymes
antibodies
transport proteins
structural proteins

Question 16

structure of enzyme

Answer 16

usually roughly spherical in shape due to tight folding of polypeptide chains. soluble and have roles in metabolism

Question 17

structure of antibodies

Answer 17

made up of two short polypeptide chains and two long polypeptide chains bonded together. they have variable regions and the amino acid sequences in these regions vary greatly.

Question 18

structure of transport proteins

Answer 18

channel proteins are present in cell membranes and contain hydrophobic and hydrophilic amino acids, which cause the protein to fold up and form a channel. these proteins transport molecules and ions across membranes.

Question 19

structure of structural proteins

Answer 19

physically strong, consisting of long polypeptide chains lying parallel to each other with cross-links between them.
examples are keratin (found in hair and nails) and collagen (found in connective tissue)

Question 20

what is the biuret test for proteins?

Answer 20

1) the test solution needs to be alkaline, so add a few drops of sodium hydroxide solution
2) add some copper(II) sulfate solution
if it turns purple then protein is present
otherwise it will stay blue

Question 21

4 different types of specialised proteins

Answer 21

enzymes
antibodies
transport proteins
structural proteins

Question 22

structure of enzyme

Answer 22

usually roughly spherical in shape due to tight folding of polypeptide chains. soluble and have roles in metabolism

Question 23

structure of antibodies

Answer 23

made up of two short polypeptide chains and two long polypeptide chains bonded together. they have variable regions and the amino acid sequences in these regions vary greatly.

Question 24

structure of transport proteins

Answer 24

channel proteins are present in cell membranes and contain hydrophobic and hydrophilic amino acids, which cause the protein to fold up and form a channel. these proteins transport molecules and ions across membranes.

Question 25

structure of structural proteins

Answer 25

physically strong, consisting of long polypeptide chains lying parallel to each other with cross-links between them.
examples are keratin (found in hair and nails) and collagen (found in connective tissue)

Question 26

what is the biuret test for proteins?

Answer 26

1) the test solution needs to be alkaline, so add a few drops of sodium hydroxide solution
2) add some copper(II) sulfate solution
if it turns purple then protein is present
otherwise it will stay blue