Nucleotides and Nucleic Acids Flashcards
What are nucleotides, and what do they form?
Nucleotides are the monomers that form nucleic acids such as DNA and RNA.
How are nitrogenous bases categorized?
Nitrogenous bases are categorized based on their structure and the number of rings: Purines have two rings (adenine and guanine), while Pyrimidines have one ring (cytosine, thymine in DNA, and uracil in RNA).
What sugars are found in DNA and RNA?
DNA contains deoxyribose, and RNA contains ribose.
What is the complementary base pairing in DNA and RNA?
In DNA, adenine pairs with thymine and guanine pairs with cytosine. In RNA, adenine pairs with uracil instead of thymine.
What type of bond forms between nucleotides, and what is the resulting structure called?
A phosphodiester bond forms between nucleotides, creating a polynucleotide chain.
What is the function of deoxyribonucleic acid (DNA)?
DNA codes for the sequence of amino acids in the primary structure of proteins, determining their final 3D structure.
What is the structure of DNA?
DNA forms a double helix made of two antiparallel strands, held together by hydrogen bonds between complementary bases.
What contributes to the stability of the DNA structure?
DNA’s stability comes from the phosphodiester bonds between adjacent nucleotides, creating a sugar-phosphate backbone.
Why is the double-stranded structure of DNA advantageous for replication?
It allows both strands to act as templates during DNA replication.
How does DNA replication occur, and what makes it semi-conservative?
During DNA replication, one strand is conserved, and a new strand is formed from new nucleotides. This is called semi-conservative replication.
What are gene mutations, and when do they occur?
Gene mutations are random, spontaneous changes in the DNA base sequence, which can occur during DNA replication.
What are the 3’ prime end and 5’ prime end in a DNA strand?
The 3’ end and 5’ end refer to which carbon in the deoxyribose sugar is exposed at the end of the DNA strand. The 3’ end exposes carbon 3, and the 5’ end exposes carbon 5.
Which enzyme catalyzes DNA replication, and where does it bind?
DNA polymerase catalyzes DNA replication, and it binds at the 3’ end of the DNA strand.
What is the first step of DNA replication, and which enzyme is involved?
The first step is the breaking of hydrogen bonds between the complementary bases, facilitated by the enzyme DNA helicase.
What happens after the DNA strands separate during replication?
Free-floating DNA nucleotides align with their complementary bases on each template strand.
How are new DNA strands formed?
Hydrogen bonds form between complementary bases of the new and old strands, and DNA polymerase forms phosphodiester bonds between adjacent nucleotides.
What is continuous replication?
Continuous replication occurs on the leading strand, where DNA polymerase can add nucleotides smoothly as the replication fork opens, synthesizing the new strand in a 5’ to 3’ direction continuously.
What is discontinuous replication?
Discontinuous replication occurs on the lagging strand, where DNA polymerase synthesizes DNA in small fragments (Okazaki fragments) due to the 5’ to 3’ direction of replication.
Why does the lagging strand experience discontinuous replication?
The lagging strand is oriented in the 3’ to 5’ direction, opposite to DNA polymerase’s 5’ to 3’ activity. This requires replication in short fragments as the fork opens.
What are Okazaki fragments and how are Okazaki fragments joined together??
Okazaki fragments are short segments of DNA synthesized discontinuously on the lagging strand during replication.
DNA ligase joins the Okazaki fragments by forming phosphodiester bonds between them, creating a continuous DNA strand.
What is the difference between the leading and lagging strands?
The leading strand is replicated continuously in the 5’ to 3’ direction, while the lagging strand is replicated discontinuously in the 3’ to 5’ direction through Okazaki fragments.
what are the steps of transcription
1) helicase acts on a region of DNA to break the hydrogen bonds between the bases
2) RNA polymerase moves along one of the two DNA strands
3) RNA polymerase matches up complimentary RNA nucleotides
4) C matches G and G matches C, U matches A and A matches T
5) as the RNA nucleotides join the pre-mRNA is formed
6) The DNA behind the RNA polymerase rejoins into a double helix
7) when the RNA polymerase reaches a stop codon, the chain is terminated and the pre-mRNA detaches
what is pre-mRNA?
contains non-coding DNA (introns)
exons- the coding parts of DNA
splicosomes- a group of enzymes that carry out splicing to remove the introns from the pre-mRNA turning it into mRNA
What does it mean that the genetic code is degenerate?
The genetic code is degenerate because multiple codons can code for the same amino acid, allowing for redundancy in the code.
what are the steps of translation
1) mRNA attaches to the ribosome at the ‘start’ codon
2) tRNA attaches to the mRNA with a complimentary anticodon
3) this tRNA brings an amino acid
4) the ribosomes move along the mRNA bringing in 2 tRNA molecules at any one time
5) an enzyme and ATP are used to join the amino acids with a peptide bond
6) the first tRNA is released and can collect another amino acid
7) the process is repeated until a ‘stop’ codon is reached
8) this forms a primary sector protein
where does transcription and translation take place
transcription- nucleus
translation- ribosomes (cytoplasm or RER)
what is ATP
adenosine triphosphate
it is a store of potential chemical energy
how does ATP release energy?
- energy is released when bonds are broken
- a small amount of energy is required to break the bond
- more is then released from breaking it
- ATP is re-synthesised in a condensation reaction using the enzyme ATP synthase
when the bond is broken ADP (adenosine diphosphate) is formed
what are the advantages of ATP
- releases energy in small, usable quantities
- easily regenerated
- ATP is a small molecule so it can move through membranes
- contains bonds between the phosphates with intermediate energy
- It’s soluble and unstable so therefore it is not good for storage so energy is stored in carbs and fats which are used as long term storage and are not soluble as they are used for other things in the body (e.g. fats are also used as insulation so therefore cannot be soluble)
why is ATP called the universal energy currency?
ATP is the chemical store in every living cell
what are the 3 types of mutation?
substitution- least harmful as it still might code for the same amino acid because codons are degenerate
insertion and deletion- causes a frame shift as it has a knock on effect on the rest of the codon. therefore they are more likely to affect the sequence of amino acids (primary structure of the protein)
