Biological Molecules B Flashcards
Base pairing
A-T
Two hydrogen bonds
C-G
Three hydrogen bonds
The quantities of AT and CG are always the same but the ratio of AT CG varies from species to species
What is DNA?
The material responsible for passing genetic information from cell to cell and generation to generation
DNA structure
The double helix has anti-parallel structure
The uprights of the phosphate and deoxyribose wind around one another
They form the structural backbone of the DNA molecule
DNA is a polynucleotide chain
Why is DNA a stable molecule?
The phosphodiester back bone protects the more chemically reactive bases inside the double helix
As there are 3 H bonds between CG the more CG pairings the more stable
Ribonucleic structure
Polymer made up of nucleotides (polynucleotides)
Single stranded and shorter than DNA
Pentose sugar is ribose no deoxyribose
And thymine is switched out for uracil
How is DNA adapted to its function
Stable structure allowing it to pass generations without significant change
The two strands are joined by H bonds allowing them to separate during replication and protein synthesis
A large molecule so can carry a lot of genetic information
Helical structure protects genetic information to some extent from chemical and physical forces
Base pairing allows DNA to replicate and transfer information as mRNA
Semi conservative replication
DNA helicase causes the double helix to unwinds as it breaks hydrogen bonds between complementary base pairs
Each exposed polynucleotide strand acts as a template
DNA polymerase joins free floating nucleotides which align due to specific base pairing
Nucleotides are joined together in a condensation reaction catalysed by DNA polymerase
Phosphodiester/hydrogen bonds reform
Four requirements for semi conservative replication
The four nucleotides each with their bases
DNA polymerase
A source of chemical energy
Both strands of the DNA molecule to act as a template strand for the attachment of nucleotides
ATP to ADP
A hydrolysis reaction
Catalyzed by ATP hydrolase (ATPase)
How does ATP store energy
The bonds between the phosphate groups are unstable so have a low Ea
This means they’re easily broken
When broken they release energy
It is a immediate source of energy - it’s not a good long term store because of its instability
Why is ATP a better energy source than glucose?
Each ATP molecule releases less energy than a glucose molecule which is released in smaller, more manageable amounts
The hydrolysis of ATP to ADP is a single reaction that releases immediate energy whether the breakdown of glucose is a long series of reactions and the energy release takes longer
Structure of ATP
Adenosine triphosphate
Chain of 3 phosphate groups
Ribose sugar which has a 5 carbon ring structure (pentose sugar) that acts as a backbone
Adenine - a nitrogen containing organic base
How is ATP adapted to its function?
It can’t move through the cell membrane
Phosphorylation
Roles of ATP
Movement
Metabolic processes
Active transport
Secretion
Activation of molecules
ADP + Pi to ATP
A condensation reaction
ATP synthase
It can occur in 3 ways -
Photophosphorylation
Oxidative phosphorylation
Substrate level phosphorylation