1.5 Nucleic Acid + 1.6 ATP Flashcards
Draw the structure of a nucleotide
Slide 4
Name the pentose sugars in DNA & RNA
DNA: deoxyribose
RNA: ribose
State the role of DNA in living cells
Base sequence of genes codes for functional RNA and amino acid sequence of polypeptides
Genetic information determines our inherited characteristics influencing structure and function of organisms
State the role of RNA in living cells
mRNA is a complementary sequence to 1 gene from DNA with introns (non coding regions) spliced out. Codons can be translated into a polypeptide by ribosomes
rRNA is component of ribosomes (along with proteins)
tRNA: supplies complementary amino acid to mRNA codons during translation
How do polynucleotide form?
Condensation reaction between nucleotides form strong phosphodiester bonds (sugar-phosphate backbone)
Describe the structure of DNA
Double helix of 2 polynucleotide strands (deoxyribose)
H-bonds between complementary purine and pyrimidine base pairs on opposite strands
Adenine + thymine
Guanine + cytosine
Which bases are purine and which are pyrimidine?
A and G 2 ring purine bases
T and C and U 1 ring pyrimidine bases
Name the complementary base pairs in DNA
2 H-bonds between adenine and thymine
3 H-bonds between guanine and cytosine
Name the complementary base pairs in RNA
2 H-bonds between adenine and uracil
3 H-bonds between guanine and cytosine
Relate the structure of DNA to its function
Sugar-phosphate backbone and many H-bonds provide stability
Long molecule storing lots of information
Helix is compact for storage in nucleus
Base sequence of triplets codes for amino acids
Double-stranded for semi-conservative replication
Complementary base pairing for accurate replication
Weak H-bonds break so strands separate for replication
Describe the structure of messenger RNA (mRNA)
Long ribose polynucleotide (but shorter than DNA)
Contains uracil instead of thymine
Single-stranded and linear (no complementary base pairing)
Codon sequence is complementary to exons of 1 gene from 1 DNA strand
Relate the structure of messenger RNA (mRNA) to its functions
Breaks down quickly so no excess polypeptide forms
Ribosome can move along strand and tRNA can bind to exposed bases
Can be translated into specific polypeptide by ribosomes
Describe the structure of transfer RNA (tRNA)
single strand of about 80 nucleotides, folded into clover shape(some paired bases)
Anticodon on one end, amino acid binding site on the other
a) anticodon binds to complementary mRNA codon
b)amino acid corresponds to anticodon
Order DNA,mRNA and tRNA according to increasing length
tRNA
mRNA
DNA
Why did scientists initially doubt that DNA carried the genetic code?
Chemically simple molecule with few components
Why is DNA replication described as ‘semi conservative’?
Strands from original DNA molecule act as a template
New DNA molecule contains 1 old strand and 1 new strand
Outline the process of semiconservative DNA replication
1.DNA helicase breaks H-bonds between base pairs
2.Each strands act as a template
3.Free nucleotides from nuclear sap attach to exposed bases by complementary base pairing.
4.DNA polymerase catalyses condensation reaction that join adjacent nucleotides on new strands
5.H-bonds reform
Describe the meselson-stahl experiment
1.Bacteria were grown in a medium containing heavy isotope 15N for many generations
- Some bacteria were moved to a medium containing light isotope 14N. Samples were extracted after 1 & 2 cycles of DNA replication
- Centrifugation formed a pellet. Heavier DNA (bases made from 15N) settled closer to bottom of tube
Explain how the Meselson-stahl experiment validated semiconservative replication
Slide 40
Describe the structure or adenosine triphosphate(ATP)
Nucleotide derivative of adenine with 3 phosphate groups
Slide 42
Explain the role of ATP in cells
ATP hydrolase catalyses ATP —> ADP + Pi
Energy released is coupled to metabolic reactions
Phosphate group phosphorylates compounds to make them more reactive
How is ATP resynthesised in cells?
ATP synthase catalyses condensation reaction between ADP and Pi
During photosynthesis and respiration
Explain why ATP is suitable as the ‘energy currency’ of cells
High energy bonds between phosphate groups
Small amount of energy released at a time = less energy wasted as heat
Single-step hydrolysis = energy available quickly
Readily resynthesised
