Nucleic acids and their functions Flashcards
What are the pyrimidine bases?
Thymine, cytosine, uracil
What are the purine bases?
Adenine and guanine
What are the pentose sugar in RNA and DNA?
RNA= ribose
DNA= Deoxyribose
What is chemoautotrophic?
An organism that uses chemical energy to make complex organic molecules
What is photoautotrophic?
An organism that uses light energy to make complex organic molecules for food.
Described how ATP and energy is related in a exergonic reaction:
The enzyme ATPase hydrolyses the bond between the second and third phosphate group, removing the third phosphate (ATP molecule is hydrolysed into adenosine diphosphate and phosphate ion), this releases chemical energy as the bond breaks (30.6 kJ).
What is phosphorylation?
Addition of phosphate to ADP
What are the advantages of ATP as a supplier of energy?
- Hydrolysis of ATP involves a single reaction, whereas break down of glucose involves many, taking longer to release the energy
- Only one enzyme is needed
- ATP releases small amounts of energy when needed, whereas glucose would release a lot at once
- Common source of energy for many different chemical reactions
What are the roles of ATP?
- Metabolic processes
- Active transport
- Movement
- Secretion
How many hydrogen bonds join up Adenine and Thymine. Cytosine and Guanine?
AT= 2
GC= 3
Why may values not be exactly equal when calculating the percentage of the four bases?
- Free nucleotides in cells
- Experimental errors may occur
Why is DNA well suited to its function?
- Stable molecule and its genetic info passes unchanged from generation to generation
- Large molecule= carry large amounts of genetic info
- Two strands are able to separate, as held by hydrogen bonds
- Base pairs are protected as they are on the inside of the sugar-phosphate backbone
Who proposed the molecular structure of DNA?
Watson and Crick
What are the two functions of DNA?
- Replication= has two complimentary strands, when separated, two identical double helices can form
- Protein synthesis= Sequence of bases can code for amino acids in proteins
Describe conservative replication:
Where the parental double helix remains intact, and a whole new double helix is made
Describe semi-conservative replication:
The parental double helix separates into two strands, each of which acts as a template for synthesis of a new strand
Describe dispersive replication:
Two new double helices contain fragments from both strands of the parental helix
Describe what Meselson-Stahl experiment did:
Grew bacteria in heavy nitrogen to make the DNA “Heavy”. Then they moved it into normal nitrogen so new DNA would be lighter. After each round of replication they extracted and spun the DNA in a centrifuge to see how heavy it was. After replication 1, the DNA was half-heavy, ruling out conservative replication. After replication 2, there were two bands, one half-heavy and one light, ruling out dispersive.
What are introns?
Non-coding nucleotide sequence in DNA and pre-mRNA, that is removed from pre-mRNA to make mature mRNA
Describe the sequence of events in transcription:
DNA helicase breaks the hydrogen bonds between the bases, allowing the two strands to separate.
RNA polymerase binds to the template strand at the beginning of the sequence
Free RNA nucleotides align opposite the template strand, the RNA polymerase moves along the strand allowing the RNA strand to grow based off of their complimentary bases. (mRNA is synthesises alongside the unwound DNA)
RNA polymerase separates from the template strand when it reaches a stop signal. DNA strands wind back in to create the double helix.
Describe the process of translation:
Initiation= Ribosome attaches to the start codon, first tRNA molecule attaches its anticodon to the codon with hydrogen bonds. Second tRNA molecule attaches to the second codon.
Elongation= The two amino acids are sufficiently close enough for a ribosomal enzyme to catalyse the formation of a peptide bond.
Termination= The sequence repeats until it reaches a ‘stop’ codon
