2.1.3: Nucleotides & ATP Flashcards
DNA is a polymer of
nucleotides
The main components of a nucleotide are:
- Phosphate group
- Pentose monosaccharide –> deoxyribose for DNA, ribose for RNA
- Nitrogenous base
Nucleotides join together by ____________ reactions
condensation
Adenine base pairs with
thymine
Thymine base pairs with
adenine
Cytosine base pairs with
guanine
Guanine base pairs with
cytosine
Molecules in the DNA double helix are:
- Complementary
- Antiparallel
- Run in 3’ to 5’, and 5’ to 3’
Structure of DNA
- Double helix of polynucleotide strands
* Hydrogen bonds between complementary bases
What are the two types of nitrogenous bases?
- Purines
* Pyrimidines
Purine
• Larger nitrogenous base
• Double ring
e.g. adenine, guanine
Pyrimidine
• Smaller nitrogenous base
• Single ring
e.g. cytosine, thymine
When cytosine pairs with guanine, they are held together by how many hydrogen bonds?
3
When adenine pairs with thymine they are held together by how many hydrogen bonds?
2
How DNA differs from RNA
- DNA double-stranded; RNA single-stranded
- RNA contains uracil; DNA contains thymine
- Pentose sugar: in DNA = deoxyribose, in RNA = ribose
RNA
Ribonucleic acid
• Molecules involved in transfer and copying of genetic information from DNA.
• Polynucleotides consist of ribose sugar + U, C, A or G.
ATP
Adenosine triphosphate
⟶ Modified nucleotide
ATP contains:
- Triphosphate group
- Adenine
- Ribose
Processes in cells that require ATP
- Secretion: endo/exocytosis, vesicle formation, fusion with plasma membrane
- Active transport
- Muscle contraction
- Synthesis of macromolecules
Properties of ATP
- Small
- Water soluble
- Contains bonds between phosphate groups with intermediate energy
- Releases energy in small quantities
- Easily regulated
How small size makes ATP suitable for function?
Moves easily into, out of and within cells.
How water solubility makes ATP suitable for function?
Energy requiring processes happen in aqueous environments.
How intermediate energy phosphate group bonds makes ATP suitable for function?
Large enough to be useful for cellular reactions, not so long energy wasted as heat.
How energy release in small quantities makes ATP suitable for function?
Quantities suited to cellular needs so energy not wasted as heat.
How easily regeneration makes ATP suitable for function?
Can be recharged with energy.
The monomers making up DNA are
nucleotides
Difference between DNA and RNA nucleotides
DNA nucleotides:
• Contain deoxyribose
• Contain Thymine
RNA nucleotides:
• Contain ribose
• Contain Uracil
Genetic code (characteristics)
- Triplet
- Non-overlapping
- Universal
- Degenerate
Transcription
1) DNA helicase unwinds and unzips section of DNA containing gene, exposing unpaired bases
2) Free RNA nucleotides complementary base pair with the exposed bases on the antisense strand
3) RNA polymerase catalyses the formation of phosphodiester bonds between RNA nucleotides
4) mRNA copy of gene exits nucleus via nuclear pore
Semi conservative replication
1) DNA helicase unwinds and separates the two strands, breaking the hydrogen bonds between them
2) Free nucleotides in excess at replication site hydrogen bond to complementary bases
3) Deoxyribose sugars of adjacent nucleotides are joined by phosphodiester bonds formed in condensation reaction, catalysed by DNA polymerase
4) One polynucleotide strand from the original molecule is conserved in each new molecule that is produced; two new molecules are identical
Translation
1) mRNA attached to ribosome; tRNA molecules carry amino acids to ribosome.
2) tRNA anticodon complementary to mRNA’s codon.
3) 2 amino acids joined by peptide bone catalysed by peptidyl transferase.
4) tRNA leaves amino acid behind. Ribosome moves along mRNA.
5) Process continues, producing polypeptide chain until ‘STOP’ codon.
6) Polypeptide moves away from ribosome; translation is complete.
What is the role of rRNA in translation?
Ribsomal RNA (rRNA) = “reads” the order of amino acids
Why do purines always pair with pyrimidines?
To ensure that the polynucleotide strands are always the same distance apart.
How are nucleotides in DNA linked?
- 3’ to 5’ linkages
* Phosphate group forms bridge between carbon 5 of one deoxyribose molecule and carbon 3 of the next
Antiparallel
run in opposite directions
At the 5’ end of DNA there is what?
A terminal phosphate group linked to carbon 5 of a deoxyribose molecule
At the 3’ end of DNA there is what?
A hydroxyl group attached to carbon 3 of a deoxyribose molecule
Cytosine and guanine number of hydrogen bonds
3
Adenine and thymine number of hydrogen bonds
2
DNA extraction from plant material
1) Grind sample using mortar and pestle (breaks cell walls)
2) Mix sample with detergent (breaks cell membrane, releasing contents of cell into solution)
3) Add salt (breaks H-bonds between DNA and water)
4) Add protease enzyme (breaks down proteins associated with DNA in the nuclei)
5) Add layer of ethanol on top of sample (causes the DNA to precipitate out of solution)
6) DNA (white strands) form between layer of sample and layer of alcohol
How does a stop codon work?
- Does not code for an amino acid
* Has no matching tRNA anticodon
