Topic 1A- Biological Molecules (Proteins)

Question 1

What are proteins made up of

Answer 1

Long chains of amino acids

Question 2

What do you call two amino acids joined together by a chemical bond

Answer 2

Dipeptide

Question 3

What do you call more than two amino acids joined together by chemical bonds

Answer 3

Polypeptide

Question 4

What is a protein

Answer 4

One or more polypeptide

Question 5

How many different amino acids are there and what makes them all different

Answer 5

There are 20 different amino acids and what makes them different is they all have different R groups

Question 6

Draw the general structure of an amino acid

Answer 6

Find it on Google

Question 7

What are the 3 groups in an amino acid

Answer 7

Amine group (H2N)
Variable group (R)
Carboxyl group (COOH)

Question 8

What type of reaction forms polypeptides? Explain what happens and what type of bond is formed and where.

Answer 8

Condensation reactions

The OH from one amino acid’s carboxyl group reacts with the H on another’s amine group to form a water molecule, and a peptide bond is formed between the Carbon and Nitrogen.

Question 9

When does the reverse reaction to the peptides being formed happen

Answer 9

During digestion

Question 10

What are the four protein levels

Answer 10

1) Primary structure
2) Secondary structure
3) Tertiary structure
4) Quaternary structure

Question 11

Give the definition of the primary structure

Answer 11

The number and sequence of amino acids in the polypeptide chain

Question 12

Explain what the secondary structure is and how this occurs

Answer 12

This is when the alpha helixes and beta pleated sheets form because of hydrogen bonding between carboxyl and amino groups in the peptide backbone. Certain amino acids tend to form an alpha helix, while others tend to form a beta-pleated sheet.

Question 13

Explain what the tertiary structure is and how this happens

Answer 13

This is the further folding of the polypeptide chain. The tertiary structure is formed by interactions between the R groups on the amino acids, such as hydrogen bonds, disulfide bridges, ionic bonds and hydrophobic interactions. This causes the chain to coil and fold even further

Question 14

How do ionic bonds occur on polypeptides

Answer 14

This is electrostatic forces of attraction between oppositely charged parts of the molecule

Question 15

How do disulfide bridges occur

Answer 15

They happen whenever two molecules of the amino acid ‘cysteine’ come close together - the sulfur atom in one cysteine covalently bonds to the sulfur atom in the other.

Question 16

What is the quaternary structure of a protein

Answer 16

some proteins are made of several different polypeptide chains held together by bonds (often disulfide bridges). The Quaternary structure is the way these polypeptide chains are assembled together.

Question 17

Draw the general structure of an amino acid

Answer 17

Google the answer

Question 18

What is an amine group

Answer 18

NH2

Question 19

What is a carboxyl group

Answer 19

COOH

Question 20

What are the elements found in amino acids

Answer 20

All have Carbon, Hydrogen and oxygen.

Some have sulfur

Question 21

What do the ends of a chain of amino acid always look like

Answer 21

One end always has a free amine group and the other always has a free carboxyl group

Question 22

What type of bonds joins the primary structure together in proteins

Answer 22

Peptide bonds

Question 23

How do you know the number of peptide bonds In a polypeptide chain

Answer 23

It’s the number of amino acids - 1

Question 24

What are the strongest type of bond in the tertiary structure of proteins and why

Answer 24

Disulfide bridges are the strongest as they are a covalent bond between two amino acids containing sulfur

Question 25

Describe the structure of haemoglobin

Answer 25

They contain 4 polypeptides :
2 alpha chains
2 beta chains
They also contain the 4 prosthetic groups (which means it’s not protein) we call this a haem group (it’s Fe2+)

This prosthetic group binds to an oxygen molecule.

Question 26

Give the definition of a quaternary structure

Answer 26

2 or more polypeptide chains held together to carry out a specific function

Question 27

Give the steps of how to test a food for proteins

Answer 27

Biuret test:

1) Mix the food sample with distilled water using a pestle and mortar, and add it to a test tube.

2) Your solution must be alkaline, so Add sodium hydroxide solution and mix carefully.

3) Add a few drops of copper (II) sulfate solution and leave the solution for 5 minutes.

4) If protein is present, the solution will turn purple. If there is no protein present, the solution will stay blue.

Question 28

Explain how a dipeptide is formed

Answer 28

This is formed by the condensation of two amino acids, forming a peptide bond between them.

The condensation reaction occurs between one amine group (NH2) and one carboxyl group (COOH), to form a peptide bond via the removal of water.

Question 29

What type of reaction forms dipeptides

Answer 29

Condensation reactions

Question 30

What type of reaction breaks down dipeptides

Answer 30

Hydrolysis reaction

Question 31

What is at each end of any chain of amino acid

Answer 31

There’s always a free amine group and a free carboxyl group

Question 32

Explain why the structure of a protein is determined by the relative position of amino acids

Answer 32

Because the bonds formed (hydrogen bonds, disulfide bridges, ionic bonds and hydrophobic interactions) are determined by the position of the R groups, which are determined by the primary structure

Question 33

What shape usually are enzymes and why

Answer 33

Spherical due to the tight folding of the polypeptide chains.

Question 34

Are enzymes soluble or insoluble

Answer 34

Soluble

Question 35

What is the word that means an enzymes active site is similar shape to the substrate

Answer 35

Complementary

Question 36

What are antibodies made up of

Answer 36

Two light (short) polypeptide chains and two heavy (long) polypeptide chains bonded together

Question 37

What is the structure of transport proteins and why

Answer 37

They are made up of hydrophobic and hydrophilic amino acids, which cause the protein to fold up and form a channel. These proteins transport molecules and ions across cell membranes

Question 38

Describe the structure of structural proteins and explain why

Answer 38

They are physically strong, so they consist of long polypeptide chains lying parallel to each other with cross - links between them.

Question 39

What does a polar and non-polar molecule mean?

Answer 39

Polar= molecules with a uniform distribution of electron density across the whole molecule

Non-polar= molecules with an unequal distribution of electrons density across the whole molecule