Biological Molecules

Question 1

What is a polymer?

Answer 1

A molecule made of many identical/similar molecules/monomers/sub-units.

Question 2

Describe the structure of an amino acid.

Answer 2

Normally a single carbon with 4 different groups attached - the “amino” part coming from a NH2 (amino group) and the “acid” coming from a COOH (carboxyl group), there is an “R” group which changes depending which amino acid it is, and the last thing attached to the carbon is a hydrogen.

Question 3

How are amino acids joined together? What bond forms?

Answer 3

By a condensation reaction, where a molecule of water is removed, and the NH2 and COOH join in a HNCO (peptide) bond (One hydrogen is removed from the NH2, and the OH is removed from the COOH (leaving the doubly bonded O))

Question 4

What is the primary structure of the polypeptide?

Answer 4

The sequence of amino acids.

Question 5

What is the secondary structure of the polypeptide? What are the 2 examples?

Answer 5

The folding of the amino acid chain, being held by hydrogen bonds. The 2 common examples are beta pleated sheets and alpha helix.

Question 6

What is the tertiary structure of the polypeptide?

Answer 6

Increased folding of the amino acid chain, being held by more hydrogen bonds, ionic bonds and disulphide bridges.

Question 7

What is the quaternary structure of the polypeptide?

Answer 7

Numerous tertiary chains joined together.

Question 8

How are proteins adapted to their roles as receptor molecules?

Answer 8

The tertiary structure of the polypeptide determines the shape of its active site, and this is complementary to the shape of their substrate, meaning only specific enzyme-substrate complexes can be formed.

Question 9

How are fibrous proteins adapted to to their function? Give an example.

Answer 9

They are long chains of amino acids, folded into either a helix or pleated sheet and they are many polypeptide chains fitted together. they are insoluble as they have r groups that are non-polar. The fibres provide stability for the protein, for example, keratin in hair has these fibres and this makes hair stronger.

Question 10

What is the test for proteins, and what would a positive result look like?

Answer 10

Biuret solution, if the solution turns from a light blue colour to a lilac colour it means that there is protein present.

Question 11

What reaction produces triglycerides? What are the 2 reactants and what bond binds them together?

Answer 11

Condensation reaction. Glycerol and 3 fatty acids joined by 3 ester bonds.

Question 12

What does benedict’s reagent test for? What does a positive result look like?

Answer 12

It tests for reducing sugars. If the solution turns brick red then a reducing sugar is present. If the solution stays blue, but then turns brick red when HCl and sodium hydrogencarbonate are added then a non-reducing sugar is present.

Question 13

What is the test for starch? What does a positive result look like?

Answer 13

Iodine/Potassium iodide can be used to test for the present of a starch. If the solution goes from orange to brown, then starch is present.

Question 14

What is the test for lipids? What does a positive result look like?

Answer 14

The emulsion test. If a lipid is present the solution will go from clear to cloudy.

Question 15

What do enzymes do, and how do they work?

Answer 15

They speed up the rate of a reaction by providing an alternative reaction pathway that requires a lower activation energy.

Question 16

What factors impact the rate of enzyme controlled reactions? How do they do this?

Answer 16

Temperature: Increased temp increases rate, as the kinetic energy increases, however this is only to a certain temp as the active site will become denatured at a certain temperature.
pH: Could increase/decrease depending on which enzyme it is, but if the pH is too acidic or alkaline it could denature the active site.
Enzyme conc: Increased conc increases rate, as there’s more active sites, but only to a certain point as if there are more active sites than substrates, the substrate conc becomes the limiting factor.
Substrate conc: Increased conc increases rate, as more enzyme-substrate complexes can be made, but only to a certain point as there are more substrates than active sites, the enzyme conc becomes the limiting factor.
Competitive reversible inhibitor conc: Increasing conc decreases rate, as the active sites become blocked.
Non-competitive reversible inhibitor conc: Increasing conc decreases rate, as the shape of the enzyme is changed.

Question 17

What is the basic structure of the DNA nucleotide?

Answer 17

Deoxyribose sugar with a phosphate and base attached.

Question 18

What are the bases that are in DNA? Which are complementary to each other?

Answer 18

Cytosine + Guanine, Adenine + Thymine

Question 19

What is the basic structure of the RNA nucleotide?

Answer 19

Ribose sugar with a phosphate and base attached.

Question 20

What are the bases that are in RNA? Which are complementary to each other?

Answer 20

Cytosine + Guanine, Adenine + Uracil

Question 21

What bond attaches nucleotides together? What reaction does this bonding occur?

Answer 21

A phosphodiester bond. Condensation reaction.

Question 22

What is the function of the phosphodiester backbone?

Answer 22

It protects the more chemically reactive nitrogen containing organic bases inside the double helix.

Question 23

How many hydrogen bonds are between the two pairs of bases?

Answer 23

Two between adenine and thymine.

Three between cytosine and guanine.

Question 24

What is meant by semi-conservative replication?

Answer 24

That the two strands produced have a strand from the original helix.

Question 25

What are the steps of semi-conservative replication?

Answer 25

DNA helicase causes the hydrogen bonds between the two strands to break, unzipping the helix.
One of the strands is used as a template for free-floating nucleotides to attach to their complementary bases.
DNA polymerase attaches them by reforming the hydrogen bonds to make two identical strands of DNA.

Question 26

What is the general structure of ATP?

Answer 26

A ribose sugar, adenine base, and 3 phosphate groups.

Question 27

What happens when ATP is hydrolysed? What catalyst is used?

Answer 27

It’s broken into ADP (Ribose sugar, adenine base, and 2 phosphate groups) and an inorganic phosphate. By breaking the phosphate-phosphate bond in ATP, energy is released. It’s catalysed by ATP hydrolase.

Question 28

If a compound is phosphorylated, what has happened to it?

Answer 28

An inorganic phosphate has been added, and the compound becomes more reactive.

Question 29

What happens when ADP goes through a condensation reaction with an inorganic phosphate? What catalyst is used?

Answer 29

It’s re-made into ATP, by reforming the phosphate-phosphate bond. It’s catalysed by ATP synthase.

Question 30

What are the properties of ATP?

Answer 30

It’s an immediate source of energy.

It can be made and reformed quickly.

Question 31

What are the properties of water?

Answer 31

It’s polar, meaning that water molecules have hydrogen bonds between them and therefore stick together.
It’s a metabolite, meaning that it’s needed for metabolic reactions such as condensation and hydrolysis.
It’s a solvent, meaning gases/enzymes/etc can easily diffuse into it.
It has a high specific heat capacity, meaning it can act as a buffer as the strong hydrogen bonds minimize temperature fluctuations.
It has a high latent heat of vapourisation, meaning that a cooling effect occurs when it evaporates, it also means that little water is lost, and this is because of the strong hydrogen bonds between the molecules require a lot of energy to evaporate even 1 gram of water.
It has strong cohesion between molecules, meaning that water can travel up xylem in columns of water, as this cohesion causes the surface tension at the water-air boundary is high.

Question 32

Name the important inorganic ions and what they’re used in.

Answer 32

Hydrogen ions: determine the pH of substances
Iron ions: in haemoglobin, and helps carry oxygen in the blood around the body.
Sodium ions: involved in the co-transportation of glucose.
Phosphate ions: component of DNA and ATP.