Module 2 Biological Molecules

Question 1

explain why insulin is insoluble in blood

Answer 1

it is polar and hydrophilic amino acids are folded on the surface

Question 2

describe the structure of collagen

Answer 2

3 polypeptides wound together in a long, strong rope-like structure

Question 3

DNA replication steps

Answer 3

• DNA section unwinds creating a replication fork
• DNA Helicase breaks hydrogen bonds between bases
• bases are exposed
• free nucleotides complementary to exposed bases align
• DNA polymerase joins the nucleotides by forming phosphodiester bonds
• DNA polymerase works in a 5’ to 3’ direction so the two strands develop in opposite directions.
• hydrogen bonds are formed between the bases and 2 new DNA helices are formed

Question 4

Why is it known as semi- conservative replication ?

Answer 4

only 50% of the parent DNA from the template ends up in daughter DNA

Question 5

give features of DNA and explain how each one is important in the semi-conservative replication of DNA

Answer 5

• weak / easily broken hydrogen bonds between bases allow 2 strands to separate/unzip
• two strands so both can act as template
• complementary base pairing allows accurate replication

Question 6

name the reaction that breaks down proteins

Answer 6

hydrolysis

Question 7

Based on what principles are amino acids separated in TLC (thin layer chromatography) ?

Answer 7

• depends on solubility in mobile phase
• depends on interactions amino acids form with silica in the stationary phase

Question 8

why should the chromatography plate only be handled by the edges ?

Answer 8

to prevent contamination with proteins on hands

Question 9

what are the three types of proteins ?

Answer 9

• globular
• fibrous
• conjugated

Question 10

two kinds of phosphorylation

Answer 10

• oxidative
• substrate-level

Question 11

describe how ATP is resynthesised in cells

Answer 11

ATP is hydrolysed to form ADP + Pi + energy. By the ATP synthase enzyme

Question 12

what are non-coding regions within a gene called that do not code for proteins ?

Answer 12

introns

Question 13

what are coding regions within a gene called that code for proteins ?

Answer 13

exons

Question 14

2 examples of functional RNA molecules

Answer 14

• transfer RNA (tRNA)
• ribosomal RNA (rRNA)

Question 15

even though DNA codes for proteins directly, why is mRNA needed to be made for making proteins ?

Answer 15

because DNA is too large to move out of the nucleus , so a section is copied into mRNA

Question 16

DNA bases are either …

Answer 16

• purines - two-carbon nitrogen ring bases (A,G)
• pyrimidines - one-carbon nitrogen ring bases (C,T)

Question 18

Stages of transcription

Answer 18

-A ribosome attaches to the start codon on the mRNA.
A tRNA molecule with a complementary anticodon to the start codon binds to the mRNA. It has a specific amino acid attached (always Methionine).
-The ribosome moves along to the next codon.
-The process is repeated and the condensation reaction between amino acids joins them with a peptide bond
-The ribosome continues to move along the mRNA until a stop codon is reached.
-The ribosome, mRNA and tRNA separate and the polypeptide is complete.

Question 19

What is splicing ?

Answer 19

removal of non coding regions (introns) from preMRNA leaving only coding regions (exons)

Question 20

Define ‘gene’ ?

Answer 20

section of DNA that codes for an amino acid

Question 21

What are Okazaki fragments?

Question 22

Biological roles of water

Answer 22

An excellent solvent - many substances can dissolve in water
A relatively high specific heat capacity
A relatively high latent heat of vaporisation
Water is less dense when a solid
Water has high surface tension and cohesion
It acts as a reagent

Question 23

What is an element ?

Answer 23

a substance made up of the same type of atom e.g. Na , Cu

Question 24

What is a molecule ?

Answer 24

two or more atoms of the same or different elements chemically combined. e.g. H2O

Question 25

What is an ion ?

Answer 25

an atom that has gained or loss electrons

Question 26

What is covalent bonding ?

Answer 26

type of chemical bond in which two atoms share a pair of electrons

Question 27

What is a monomer ?

Answer 27

smaller units from which larger molecules are made

Question 28

Property to function: Water as a good solvent

Answer 28

Property: polarity so many ions and covalently bonded polar substances will dissolve in it Related functions: - chemical reactions can occur within cells - hydrophilic metabolites can be transported efficiently which allows organisms such as prokaryotes to exchange useful substances with their surroundings via diffusion

Question 29

Property to function: Specific heat capacity

Answer 29

Property: high specific heat capacity due to many hydrogen bonds. Waters specific heat capacity is 4200 J/kg C meaning a relatively large amount of energy is required to raise temperatures Functions: - provides suitable stable habitats in aquatic environments - is able to maintain a constant temperature as water is able to absorb a lot of heat without big temperature fluctuations which is optimal for enzyme activity. - Water in blood plasma is also vital in transferring heat around the body , helping to maintain a fairly constant temperature.

Question 30

Property to function: Specific latent heat

Answer 30

Property: high specific latent heat due to many hydrogen bonds meaning a relatively large amount of thermal energy is required for water to change from liquid to gas Functions: - Coolant - only a little water is required to evaporate for the organism to lose a great amount of heat - this provides a cooling effect for living organisms for example the transpiration from leaves or evaporation of water in sweat on the skin

Question 31

Property to function: Cohesion and adhesion

Answer 31

Property: Hydrogen bonds between water molecules allows for strong cohesion between water molecules. Water is also able to hydrogen bond to other molecules, such as cellulose, which is known as adhesion. Functions: - allows columns of water to move through the xylem of plants and through blood vessels in animals - enables surface tension where a body of water meets the air

Question 32

Property to function: Water expansion when frozen

Answer 32

Property: water is most dense at 4 degrees at which point it is still a liquid. This means that when water freezes into ice, it becomes less dense as water molecules are held further apart in ice than water. Therefore ice floats , creating a layer of insulation so that the rest of the water below does not freeze Functions: allows aquatic organisms to continue living in that environment , making water an ideal habitat

Question 33

Specific heat capacity

Answer 33

The specific heat capacity of a substance is amount of thermal energy required to raise the temperature of 1kg of that substance by 1 degrees

Question 34

Specific latent heat

Answer 34

The specific latent heat of vaporisation of a substance is the amount of thermal energy required for a substance to change state from liquid to gas.

Question 35

What is a polymer ?

Answer 35

molecules made from lots of repeating units (monomers) joined together

Question 36

condensation reaction

Answer 36

joins two monomers together with the formation of a covalent bond and involves the elimination of a molecule of water or another small molecule

Question 37

hydrolysis reaction

Answer 37

breaks the covalent bond between two monomers and involves the use of a water molecule