2.1.3 Nucleotides and nucleic acids Flashcards
what is a nucleotide?
it is a bio molecule and a monomer that can join to make the polymer nucleic acid - DNA and RNA
- all nucleotides contain: Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphate
- consists of a pentose sugar, phosphate group and a nitrogenous base
why are nucleotides important?
- they r the monomers that make up DNA/RNA(stores genetic info and how to make proteins)
- can become phosphorylated nucleotides that make up ADP and ATP(energy currency of the cell)
- may be the components of coenzymes e.g. adenine nucleotides r components of coenzyme NADP
what is a DNA nucleotide and draw it
- contains a deoxyribose sugar as the pentose sugar, a nitrogenous base that can be either (adenine(A), thymine (T), cytosine (C), and guanine (G)) and a phosphate group
draw here
what is a RNA nucleotide and draw it
- contains a ribose sugar as its pentose sugar, a nitrogenous base that is either; adenine (A), Cytosine (C), Guanine (G) or Uracil (U), and a phosphate group
how can u classify the nitrogenous bases? an what do they mean?
there r two types of bases: purines or pyrimidines
purines include: Adenine/Guanine
pyrimidines: Cytosine/Thymine/Uracil
difference is in the struc - purines are 2 carbon-nitrogen rings joined together and pyrimidines r 1 C-N ring so the latter is smaller than the former
what is ADP and ATP
they are phosphorylated nucleotides - both containing base adenine and sugar ribose
- to phosphorylate a nucleotide u add a phosphate group
- ADP(adenosine diphosphate) - 2 phosphate groups
- ATP (adenosine triphosphate) - 3 phosphate groups
how is ATP used and released
energy released from glucose is used to make ATP and then ATP is broken down to release energy for cells to use
- ATP is synthesised from ADP and inorganic phosphate (Pi)
- ADP is phosphorylated to form ATP and a phosphate bond is formed using the energy from glucose
- energy is stored in the phosphate bond and when needed will break down to release energy
what are many nucleotides joined together called
polynucleotides
what is the structure of a polynucleotide and how do nucleotides bond
draw diagram
nucleotides join between the phosphate group of one and the sugar of another to form a phosphodiester bond (where 1 phosphate group makes 2 ester bonds on both sides)
- the chain of sugars and phosphates is known as the sugar-phosphate backbone
diagram
what is the structure of DNA
- it is a polymer consisting of nucleotide monomers
- each nucleotide consists of 1 pentose (deoxyribose) sugar, 1 phosphate group, and A/C/T/G as their nitrogenous base
- nucleotides joined by phosphodiester bonds
- composed of 2 polynucleotide chains joined to forma double helix shape
- strand join via H bonds between bases (complementary base pairing): A-T and G-C
- two H bonds form between A and T and 3 form between G and C
- the strands r anti-parallel (run in oppo directions)
what is complementary base pairing
A forms 2 H bonds to T
C forms 3 H bonds to G
(or inRNA A forms 2 H bonds to U)
explain the struc and also draw the anti-parallel sugar-phosphate backbone
the anti parallel sugar phosphate backbone is formed by 2 polynucleotides running in opposite directions w the nucleotides joined by phosphodiester bonds and the strands to each other by Hbonds
- the oppo direction refers to direction of 3rd/5th Carbon molecule on the deoxyribose are facing
- 5’ end is when phosphate is attached to 5th carbon atomof sugar
- 3’end is when phosphate is attached to 2rd C atom of sugar
- molecule is stable af
diagram
how is DNA arranged in a eukaryotic cell
- maj of DNA in nucleus
- each molecule of DNA wound around proteins called histones into chromosomes
- each chromosome is 1 molecule of DNA
- also loops of DNA in mitochondria and chloroplasts
how is DNA arranged in a prokaryotic cell
- DNA is in a loop in cytoplasm(no nucleus)
why and when does DNA replicate?
- each cells makes copies of its DNA so that the when cell division occurs each daughter cell has the same original amount of DNA as the parent cell - aka it is genetically identical
- it replicates during interphase
what is DNA replication also known as
semi conservative replication
how does semi conservative replication work (show the direction by drawing diagram)
- DNA molecule unwinds, double helix untwists (gyrase enzyme)
- DNA unzips (catalysed by DNA helicase) - H bonds break between polynucleotide strands leaving exposed nucleotide bases
- free phosphorylated nucleotides bond to exposed bases by complementary base pairing
- DNA polymerase catalyses addition of new nucleotide bases in the 5’ to 3’ direction to the strands of DNA using unzipped DNA as temple
- leading strand is synthesised continously
- lagging strand is in fragments (later joined by ligase enzymes)
product is 2 DNA molecules - identical to each other and to the parent molecule - each contains 1 new strand and 1 old strand - making it semi-conservative replication
diagram
what is a mutation
a random change to the DNA base sequence - inserting wrong nucleotide
what r the effects of a mutation during DNA replication
can be advantageous e..g white coat in winter can help conceal
or disadvantageous - e..g make a faulty enzyme
or just neutral e..g can roll your tongue
name differences between RNA and DNA molecule
RNA sugar is pentose not deoxyribose
RNA nitrogenous bases r Uracil and not Thymine
RNA is a single stranded molecule
RNA is shorter
there r 3 forms of RNA: m(messenger)RNA, r(ribosomal)RNA, and t(transfer)RNA
define a gene
a gene is a length of DNA that codes for a polypeptide or for a length of RNA that is involved in regulating gene expression
how do genes code for a polypeptide
each gene contains a sequence of DNA base triplets that determines the aa sequence or primary struc of a protein/polypeptide
- (aka every 3 nucleotides codes for a specific aa - the sequence of the triplets determines which one)
why is the gene important for proteins
- determines it primary struc which will in turn determine its ultimate final struc/shape (tertiary/quatenary)
- e..g shape of active site of enzyme most be complementary of substrate to work
- antibodies must to complementary to the antigens on pathogens it attacks
why is mRNA necessary
the original instructions for making proteins cannot be removed from the nucleus so it has to be transcribed into mRNA to be transferred to ribosomes to make proteins
- the base triplets r now called codons
