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Topic 1B- More Biological
Molecule
Created

@February 10, 2025 3:30 PM

Class

Cells to Systems

DNA and RNA Carry Important Info
DNA stores genetic info
Instructions required for grow and development in organisms
RNA structure is similar to DNA, transferring genetic info from DNA to
ribosomes
Ribosomes read RNA sequences to produce polypeptides

Nucleotide
Made from pentose sugar
Nitrogen organic base
Phosphate group
Monomers that are in DNA and RNA

Sugar in DNA
Called Deoxyribose
All nucleotides have the same sugar and phosphate group

Topic 1B- More Biological Molecule

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Base varies- Can be Adenine, thymine, cytosine or guanine

Sugar in RNA
RNA contains ribose sugar instead of deoxyribose
Also contains phosphate group and Uracil as base (Replaces Thymine)

Polynucleotides
Polymer of nucleotides
Formed by DNA and RNA
Nucleotides fuse via condensation reaction
Creates phosphodiester bond (Phosphate group and two ester bonds)
Sugar-Phosphate Backbone
Made of chain of sugars and phosphates

Double- Helix Structure
Two DNA polynucleotides link via hydrogen bonding
Complementary Base Pairing- Base only joins with something specific
Adenine joins with Thymine, A-T
Cytosine with Guanine, C-G
Two H bonds between A-T
Three H bonds between C and G
Nucleotide strands facing opposite directions twist to create double helix

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Short Polynucleotide Chain
RNA is made from one polynucleotide chain
Shorter than DNA polynucleotides

Semi- Conservative Replication
DNA helicase enzyme breaks H bonds
Causes helix to unwind
Original strand is template for new strand
Free DNA nucleotides go towards exposed complementary bases
DNA polymerase catalyses condensation reaction, linking free nucleotides
together, H bonds form
Fresh DNA contains old and new strand of DNA

Antiparallel Strands
Active site is complementary to 3’ end of new DNA strand, nucleotides can
only join this end
New strand is made in 5’ to 3’ direction and template strand is moved to 3’
to 5’ direction
Strands are in opposite directions

Water
Importance
H20 is involved in lots of metabolic reactions
H20 is solvent causing substances to dissolve

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Solvent can help with temp control
Molecules stick together making it easy to be transported inside plants
Structure
Contains one oxygen atom and 2 hydrogens with shared electrons
Polar molecule, due to one side containing small positive charge and
the other having small negative charge
Properties
Involved in condensation and hydrolysis
Condensation releases H20 as biproduct
Hydrolysis needs H20 to break bonds
High Latent Heat of Vaporisation
Needs high amounts of energy to break H bonds
This occurs during evaporation
Useful for organisms as a way to cool down
Resisting Changes in Temp
H bonds absorb lots of energy
Needs lots of energy to heat water
No quick temp changes, means temp is stable
Helps organisms keep constant body temp
Good Solvent
Involved in metabolic reactions so molecule is made of positively and
negatively charged atom
Positive side is attracted to negative ion and vice versa
Ions become surrounded by water molecules
Strong Cohesion
Very cohesive due to polar properties

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Helps it to flow and makes it ideal for transporting molecules
Contains high surface tension

ATP (Adenosine Triphosphate)
Immediate Energy Source
Energy released from glucose via respiration
Energy can’t be obtained directly from glucose
Energy released contributes to ATP production
ATP is made from adenine, ribose sugar and three phosphate groups
Molecule diffuses to cell requiring energy
Stored between phosphate groups
Quickly Made and Used
ATP broken into ADP
Causes energy release, reaction is catalysed by ATP hydrolase
Energy can be used to initiate other reactions
Inorganic phosphate is added to another substance making it more
reactive
ATP can be re-synthesised in condensation reaction then catalysed by
ATP synthase

Inorganic Ions
Contains Electrical Charge
Positive charge- Cation

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Negative charge- Anion
Doesn’t contain carbon- Inorganic ion
Part of Haemoglobin
Haemo is large protein carrying oxygen around body
Made of four polypeptide chains with iron ion
Ion binds to oxygen
More hydrogen ions present, more acidic the environment is
Glucose and Amino Acids
Require sodium ions to help molecules be transported into cell
Known as cotransport
Phosphate Ions
Attached to phosphate group
P
...
groups store ATP
Groups allow nucleotides form polynucleotides

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