1.5 - Nucleic acids and their functions Flashcards
What do you call DNA, RNA and ATP?
Nucleotides
What does each nucleotide contain?
- a phosphate group
- pentose sugar
- a nitrogenous base
What are the four nitrogenous bases in DNA and are they purine or pyrimidine?
Thymine (pyrimidine)
Adenine (purine)
Cytosine (pyrimidine)
Guanine (purine)
What does pyrimidine and purine mean?
pyrimidine is a single ring
purine is a double ring
what does ATP stand for?
adenosine triphosphate
What is the structure of adenosine triphosphate?
3 phosphate, ribose and adenine
How is adenosine diphosphate formed?
when the high energy bond between the 3rd and 2nd phosphate group is broken via hydrolysis by the enzyme ATPase, 30.6kj of energy is released
What is the reaction for ATP to ADP and vice versa? (its reversible)
ATP ⇌ ADP + Pi + 30.6 kj energy
What is adding a phosphate group to ADP called? And what is this reaction called?
Phosporylation, it’s an endergonic reaction (energy is used)
What kind of reaction is hydrolysis?
An exergonic reaction (energy is given out)
Where is ATP produced?
in the cytoplasm, mitochondria (matrix and inner membrane) and in chloroplasts
What is universal energy currency?
used for energy in all cells in all living organisms
What does ATP provide energy for?
Metabolic processes (builds large molecules from smaller molecules)
Active transport
Muscle contraction/movement
Nerve impulse transmissions
Secretion (packaging and transport of secretary products into vesicles)
What are the advantages of ATP?
-hydrolysis of ATP to ADP is a single reaction that releases immediate reactions (efficient and only needs 1 enzyme)
-releases energy in small amounts vs glucose which contains large amounts of energy
- soluble and easily transported
- universal energy currency
What does the DNA structure consist of?
- of two polynucleotide strands that are arranged into a double helix
- anti-parallel
- held together by H-bonds that form between complimentary nitrogenous bases (ATGC)
- The h-bonds are weak but collectively are very strong
How do we extract DNA?
by grinding up a sample in a solution of ice cold salt and washing up liquid
-> the detergent dissolves the lipids in the phospholipid membranes allowing the DNA to be released and cold temp protects the DNA from cellular DNAases.
When comparing RNA to DNA what are the 7 things that should be listed?
1.Name
2.Strange number
3.Chain length
4.Pentose sugar
5.Organic bases
6.Chemical stability
7.Function
What is the full name of DNA? RNA?
Deoxyribonucleic acid, Ribonucleic acid
What is the function of DNA? RNA?
-carries genetic information
-transfers information from DNA to ribosomes, makes up ribosomes w/proteins, involved in protein synthesis
What is the chemical stability of DNA? RNA?
-very stable
-less stable
What is mRNA? What does it do?
-a single stranded molecule, synthesised in the nucleus
-copies and then carries genetic infor from DNA to ribosomes in cytoplasm, each strand of mRNA contains genetic code for 1 gene and each gene codes for a particular polypeptide
What is rRNA? What does it do?
-ribosomal RNA forms ribosomes w/addition of protein, found in the cytoplasm
-ribosomes are the site of protein synthesis by process of translation
What is tRNA? What does it do?
-small molecule winded intto a cloverleaf shape, has an anticodon at one end and an amino acid at the other
-transfers correct amino acid to the growing polypeptide during translation
What happens during replication?
-DNA helicase breaks the H-bonds between the bases causing the double helix to unwind and separate into 2 strands
-the exposed bases bind to free floating nucleotides (forming phosphodiester bond)
-1 strand acts as a template for new molecule so newly synthesised DNA contains 1 parent strand and a complimentary newly synthesised strand
What were the three theories on DNA replication?
conservative replication
semiconservative replication
dispersive replication
What were the steps in Meselson’s and Stahl’s ‘beautiful experiment’ which proves semiconservative replication?
- Bacteria (e.coli) was grown for a generation in heavy nitrogen agar, when Dna was centrifuged the Dna band settled low down the tube
- then grown for the 1st generation in light nitrogen agar, when the dna was centrifuged, the dna band settled at a mid-point on the tube (hybrid DNA)
- after 2nd generation in light agar, Dna band extracted formed a lighter band at the top of the tube
How is conservative replication ruled out?
b/c after bacteria was grown for one generation in light nitrogen, only one dna band was produced - if it was conservative replication two bands would have been seen - one in the light position, one in the heavy position
How is dispersive replication ruled out?
half of the DNA after grown for two generations was half heavy, weight and half light
What is meant by the term semi-conservative replication?
each new DNA molecule consists of 1 original template strand and one newly synthesised strand which ensures the genetic info is accurately passed on during cell division
Where does transcription occur?
in the nucleus
Where does translation occur?
at ribosomes
Where does post-translational modification occur>
in Golgi apparatus prior to packaging of the protein into vesicles
What are the 5 steps to transcription?
- DNA acts as a template for the production of mRNA
- DNA helicase acts on a specfic region of DNA, breaking the H-bonds between the DNA strands causing them to unwind exposing free nucleotide bases
- Free RNA nucleotides pair to exposed bases on the template strand and RNA polymerase joins them by forming H-bonds. 4. This contunues until RNA polymerase reaches a stop codon when RNA detaches and production of mRNA is complete. 5. mRNA carries DNA code out of nucleus through a nuclear pore to the cytoplasm and attaches to a ribosome.
Define what an intron is
non-coding nucleotide sequence in DNA and pre-mRNA that is removed from pre-mRNA to produce mature mRNA
Define what an exon is
nucleotide sequence on one strand of the DNA molecule and the corresponding mRNA that codes for the production of a specific polypeptide
where do amino acids come from?
come from proteins, made by plants which animals eat and is passed on
What are the 5 steps of translation?
- Initiation (a ribosome attaches to a start codon at 1 end of the mRNA molecule)
- A tRNA molecule w/a comp anticodon to the 1st codon binds to the 1st attachment site on ribosome.
- Elongation (2nd tRNA molecule joins to 2nd attachment site + a risbomal enzyme catalyses the formation of a peptide bond between 2 amino acids)
- 1st tRNA is released + ribosome now moves 1 codon along the mRNA which exposes a free attachment site and another tRNA molecule joins and process repeats. 5. Termination (amino acid added until the ribsoome reaches a stop codon, ribosome detaches from mRNA molecule + polypeptide is released).
