nucleotides and nucleic acids Flashcards
what is the structure of a nucleotide
pentose sugar, a nitrogenous base, phosphate group.
nucleotides contain elements C,H,O,N,P
differences between RNA and DNA nucleotides
DNA- contains deoxyribose, double stranded, contains thymine
RNA- contains ribose, single stranded, contains uracil
how to identify purines and pyrimidines in DNA and RNA nucleotides
Adenine and Guanine- purines
Cytosine , Thymine and Uracil- pyrimidines
difference between the bases is in their structure, purine base contains two carbon nitrogen rings whereas pyrimidines only has one carbon nitrogen ring so it’s smaller
structure of ADP and ATP
they are phosphorylated nucleotides
ADP (adenosine diphosphate)- adenine, ribose, two phosphate groups
ATP (adenosine triphosphate)- adenine,ribose, three phosphate groups
structure of DNA (deoxyribonucleic acid)
dna is made up of nucleotides which consists of deoxyribose sugar, phosphate group and a nitrogenous base. the nucleotide monomers are joined together through condensation reactions forming a phosphodiester bond. DNA is composed of two polynucleotide strands, in the structure of a double helix, the strands run antiparallel to each other. the bases within DNA are adenine, thymine, cytosine and guanine, they are joined together by complimentary base pairing which forms hydrogen bonds. A-T forms 2 bonds, C-G forms 3 bonds
explain the synthesis and breakdown of polynucleotides by the formation and breakage of phospodiester bonds
nucleotides join together to form polynucleotides, the nucleotides join up between phosphate groups of one nucleotide and the sugar of another through condensation reaction- this forms phosphodiester bond
polynucleotides can be broken down by breaking the phosphodiester bonds using hydrolysis reaction
explain semi conservative DNA replication
1.DNA helicase breaks hydrogen bonds between two polynucleotide DNA strands, unzips o form two single strands
2. each original strand acts as a template for a new strand. free floating DNA nucleotides join to the exposed bases on each original template strand by complimentary base pairing- A-T ,C-G
3. nucleotides on the new strands are joined together by DNA polymerase, catalyses the formation of the sugar phosphate backbone. hydrogen bonds form between the bases on the original and new strands. the strands twist to form a double helix and half the molecule is the original template strands and half is the new daughter DNA
why is it important conserving genetic information
it is important that DNA replication is accurate and the information is conserved because a random mutation (change to DNA sequence) may occur and they can alter the sequence in amino acids, this can cause an abnormal protein to be produced
what is a gene and how does a gene determine the sequence of an amino acid in a polypeptide (the primary structure of a protein)
gene is a sequence of DNA nucleotides that codes for a polypeptide. the order of nucleotide bases in genes determines the order of amino acids in a particular protein. each amino acid is coded for by a sequence of three bases (triplet) in a gene.
explain the genetic code
genetic code is the sequence of base triplets (codons) in DNA or mRNA which codes for specific amino acids
base triplets don’t share their bases, this is known as non overlapping
genetic code is also degenerate- some amino acids will have multiple triplets
genetic code is also universal- triplets are the same in all organisms
explain the roles and structure of mRNA, tRNA and rRNA
mRNA (messenger RNA)- single polynucleotide strand, made in the nucleus during transcription, carries the genetic code from DNA in the nucleus to the protein during translation, three adjacent bases are codons
tRNA (transfer RNA)- single polynucleotide strand that’s folded into a clover shape, hydrogen bonds between specific base pairs hold molecules shape, every molecule has specific three bases called anticodons and an amino acid binding site at the other end, found in cytoplasm and involved in translation, carries amino acids used to make proteins to ribosomes
rRNA (ribosomal RNA)- forms two subunits in a ribosome and proteins, rRNA in ribosome helps catalyse formation of peptide bonds between amino acids
describe transcription
first stage of protein synthesis
1. RNA polymerase attaches to the DNA double helix at the beginning of a gene. the hydrogen bonds between the two strands of DNA in the gene break, separating the strands, and the DNA molecule uncoils. one of the strands is then used to make a template for mRNA copy
2. the RNA polymerase lines up free RNA nucleotides alongside the template strand, complementary base pairing means that mRNA strand ends up being a complementary copy of the DNA template strand. when RNA nucleotides have paired up with their bases on DNA strand, they’re joined together by RNA polymerase, forming an mRNA strand
3. the RNA polymerase moves along the DNA, assembling the mRNA strand. the hydrogen bonds between the uncoiled strands of DNA reform once the RNA polymerase has passed by and the strands recoil back into double helix
4. when RNA polymerase reaches the stop codon, it stops making mRNA and detaches from the DNA, the mRNA leaves the nucleus through nuclear pores and attaches to a ribosome in the cytoplasm where the next stage of protein synthesis takes place
describe translation
amino acids are joined together by a ribosome to make a polypeptide chain following the sequence of codons carried by the mRNA
1. the mRNA attaches itself to a ribosome and tRNA molecules carry amino acids to the ribosome
2. a tRNA molecule with an anticodon that’s complimentary to the start codon on the mRNA attaches itself to the mRNA by CBP, a second tRNA molecule attached itself to the next codon on the mRNA in the same way
3. rRNA in the ribosome catalyses the formation of a peptide bond between the two amino acids attached to the tRNA molecules, this joins the amino acids together, the first tRNA molecule moves away leaving its amino acid behind
4. a third tRNA molecule binds to the next codon on the mRNA, its amino acid binds to the first two and the second tRNA molecule moves away, this process continues producing a polypeptide chain, until their is a stop codon on the mRNA molecule
5.the polypeptide chain then ,obey away from the ribosome and the translation is complete
properties and limitations of ATP
properties- small so it can move out of. ells, water soluble, contains phosphate bonds with immediate energy, releases energy in small quantities, easily regenerated
limitations- instability of phosphate bonds means ATP isn’t a good long term energy store
