Proteins

Question 1

Size of proteins

Answer 1

Usually very large

Question 2

Each organism…

Answer 2

Makes its own unique proteins. It’s proteins that give the organism their characteristics and allow key functions to occur

Question 3

Proteins are key biological molecules - why?

Answer 3

The shape is highly specific and there fore different to other type of types

Question 4

Monomers of proteins

Answer 4

Amino acids

Question 5

Amino acids contain which elements?

Answer 5

Nitrogen (N), Carbon (C), Oxygen (O), Hydrogen (H) and sometimes sulphur (S)

Question 6

Variety of proteins: Different roles

Answer 6

-Haemoglobin -> Transports oxygen by binding to it
-Antibodies -> Defends the body against infection
-Enzymes -> Biological catalysts
-Actin and myosin -> Involved in muscle contraction

Question 7

Variety of proteins: Structural role

Answer 7

-Keratin -> Found in nails, hair and hooves
-Collagen -> Found in tendons

Question 8

How many types of amino acids?

Answer 8

20 different types of amino acids, all with the same general structure

Question 9

Essential and non-essential amino acids

Answer 9

You must ingest the essential amino acids in your diet, non-essential amino acids can be synthesised by your body

Question 10

General amino acid structure

Answer 10

H H O
| | | |
H—-N—-C—-C—-OH
|
R

Question 11

Each amino acid contains

Answer 11

A central carbon and 4 different chemical groups
-A nitrogen containing amine group (NH^2 or H^2N)
-A carboxyl group (COOH)
-A hydrogen atom (H)
-A ‘R’ variable side chain or group

Question 12

What is different in amino acids in the general structure?

Answer 12

‘R’ variable side chain. Each R group has a different size and are grouped together by different properties e.g. charge and polarity

Question 13

Formation of a peptide bond

Answer 13

Two amino acids joined together to form a dipeptide by a condensation reaction. The hydroxyl group (OH) from the carboxyl group of one amino acid reacts with a hydrogen (H) from the amine group of the second amino acid via a condensation reaction. The water is removed in the formation of a PEPTIDE BOND

Question 14

Many (hundreds of) amino acids form what?

Answer 14

Form a polypeptide chai as a result of many condensation reactions

Question 15

Important points of peptide bonds

Answer 15

-A peptide chain will always have an amine group at one end (N terminus) and a carboxyl at the other end (C terminus)
-Number of peptide bonds in the chain will be one less than the number of amino acids originally joined together

Question 16

Proteins structure

Answer 16

Primary -> Secondary -> Tertiary -> Quaternary

Question 17

Primary structure

Answer 17

-The number and sequence of amino acids in a polypeptide chain. Because there is 20 amino acids, there is a limitless number of possible sequences
-Determines the positions of the bonds = Hydrogen, ionic and disulphide -> between R groups and final shape of protein
-Specific shape indicates it’s function

Question 18

Secondary structure

Answer 18

-The linked amino acids all have -NH and -C=O groups on either side of the polypeptide chain. NH group has overall positive charge and C=O has an overall negative charge.
-A hydrogen bond forms between the slight positive charge on the H and the slight negative charge on oxygen
-These 2 groups form weak hydrogen bonds through put the polypeptide but because there is so many they are strong
-Due to hydrogen bonding the chain coils into alpha helices or folds it’s beta pleated-sheets

Question 19

Tertiary structure

Answer 19

-This is the further folding of the secondary structure into a specific, complex 3D shape
-R groups on the amino acids determine how the chain folds into 3D specific shape.
-Held together by bonds and interactions between R groups of different amino acids
-Hydrogen bonds = weak bonds and easily broken with increasing temperature
-Ionic bonds = Weak but not as week as hydrogen. Bonds form between oppositely charged R groups and are broken by changes in pH