Core Concept: Nucleic acids and their functions Flashcards
What is a nucleotide
monomer of a nucleic acid
contains a pentose sugar nitrogeneous base and a phosphate group
What is a nucleic acid
polymers of nucleotides
What are the two types of organic(nitrogenous) bases
purine and pyrimidine
What reaction releases energy from ATP
What is the name of the enzyme that catalyses this
hydrolysis
ATPase
What are the components of ATP
adenine base ribose sugar and three phosphates
Why is ATP referred to as a universal energy currency
used to provide energy for all biochemical reactions in all living organisms
Define phosphorylation
the addition of a phospahte group to a molecule
Describe the formation and breakdown of ATP in terms of endergonic or exergonic
the formation of ATP is condensation reaction which is endergonic
the break down of ATP is hydrolysis which is exergonic
Advantages of using ATP as an energy supplier instead of glucose directly
4 points
provides a useable small amount of energy when and where it is needed
one hydrolysis reaction that releases energy immediately whereas glucose involves many intermediates and takes longer for energy to be released
one enzyme needed to hydrolyse ATP but many needed for glucose
higher efficiency of ATP than glucose higher control by the cell
Roles of ATP
5 points
Metabolic processes- build large complex molecules (DNA synthesis)
Active transport- to change the shape of carrier proteins
Movement - for muscle contraction
Nerve transmission - Na and K actively transported across axon membrane
secretion - the packaging and transport of vesicles
Structure of DNA
double helix
antiparallel
long thin and tightly coiled molecule
comlimentary base pairs A,T,C,G
phosphate deoxyribose sugar backbone
What are the complimentary base pairs of DNA
Are they purine or pyrimidine
adenine and thymine
cytosine and guamine
purine= adenine and guamine
pyrimidine= cytocine and thymine
What bonds are between the bases
hydrogen bonds
How is DNA suited for its function
4 points
stable so information passes unchanged from generation to generation
is long chain so holds alot of genetic informstion
two strands are able to seperate as they are held together by H bonds
double helix shape protects the genetic information on the inside
The structure of RNA
single stranded
shorter than DNA
ribose sugar
AUCG bases
Complimentary base pairs of RNA
Are they purine or pyrimidine
Adenine and Uracil
Cytosine and Guamine
purine= adenine and guamine
pyrimidine= cytocine and uracil
Different types of RNA and their function
mRNA - carries genetic code from the DNA to the ribosomes
rRNA - component in ribosomes
tRNA- provides the ribosomes with specific amino acids for protein synthesis
Differences between RNA and DNA
4 points
RNA is single stranded DNA is double stranded helix
RNA has Uracil DNA has Thymine
RNA is shorter DNA is longer
RNA has ribose sugar DNA has deoxyribose sugar
Two main roles of DNA
Replication
Protein synthesis
Process of DNA replication
DNA helicase breaks H bonds between bases(DNA is unzipped)
this exposes unpaired bases.
free DNA nucleotides bind to their comlementary base pairs on the template strand DNA polymerase binds these nucleotides together by condensation reactions between sugar and phosphate groups of adjacent nucleotides then 2 new DNA molecules are formed from 1 new and 1 old strand of the DNA.
Define semi-conservative replication
Theory of DNA replication in which each strand of a parental double helix acts as a template for the formation of a new molecule, each containing an original, parental strand, and a newly synthesised, complementary daughter strand.
Describe the process of the experiment that confirmed the semi-conservative replication theory
E.Coli DNA was placed ina culture medium comtaining a heavy nitrogen isotope (N15) and then left to replicate once
it was washed and transfeered to another culture medium of light nitrogen (N14) it was left to replicate 2 more times
upon the 1st round of replication (in N15) it was centrifuged the result was a band near the bottom of the centrifuge of high density
the 2nd round this was repeated and there was only one band in the middle of the centrifuge with a mid point density suggesting an even mix of N14 and N15. this disproved conservitive replication
the final round of replication there was a band in the middle where it was previously observed and a band higher up with less density suggeesting DNA strands of N14 only this disproved dispersive replication
What are the other theories of DNA replication that were disproved by Meselsohn and Stahl’s experiment
2 points
dispersive- each new double helix synthesised contains fragments of new and old DNA
conservative- a whole new double helix is synthesised
How many bases code for an amino acid
What is this called
three
its called a triplet code of DNA
once transcribed onto mRNA it is called a codon
Characteristics of the genetic code
three bases encode for each amino acid
there are 64 possible codes but only 20 amino acids
the code is punctuated as there are codes that dont code for amino acids but are stop codons
the code is universal
code is non overlapping
How many possible codes are there
What does the suggest
64 because 4 bases triplet code is 3 so 4 to the power of 3
this suggests more than triplet code codes for the same amino acid
What is a ‘stop’ codon
a codon that is at the end of the mRNA that does not code for a protein but codes for the end of the chain (ribosomes stops) synthesising
What is meant by the code being universal and non-overlapping
one base is in one code
the same 3 bases code for the same amino acid in every organism universally
Define intron
non coding region of DNA
Define exon
coding region of DNA
What is the difference between DNA of a prokaryote and DNA of a eukaryote
DNA is in the nucleus in eukaryotes whereas in the prokaryote it is not
DNA has introns in eukaryotes but prokayotic DNA does not only (Exons)
Name the two stages of protein synthesis
Transcription
Translation
Describe the process of transcription
DNA helicase unzips a section (gene) of the DNA by breaking the hydrogen bonds between complementary base pairs.
RNA polymerase links to the template strand of DNA and attaches mRNA nucleotides to their complementary base pairs, until a stop sequence / codon.
The newly made premRNA then leaves the DNA.
Post-transcriptional modification of the pre-mRNA takes place to remove the introns, leaving only exons in the mature mRNA. This leaves the nucleus via the nuclear pores to be translated into a protein in the cytoplasm.
Describe the process of translation
mRNA is a linear chain of three base codons. There are complementary anticodons on tRNA molecules.
When the mRNA leaves the nucleus, it attaches to the small subunit of a ribosome.
The large subunits of a ribosome have 2 attachment sites for tRNA. The ribosome holds the mRNA and the tRNA (which have attached specific amino acids) in position for the amino acids to form peptide bonds and create a polypeptide chain.
The codon on the mRNA therefore determines the tRNA as the tRNA which attaches must have a complementary 3 base code. called an anti codon.
The tRNA that matches the codon on the mRNA has a specific amino acid attached to the 3’ end of the tRNA molecule. The ribosome moves along the mRNA holding each tRNA in place until the amino acid attaches. The tRNA then leaves, the ribosome moves along and the next tRNA attaches to the next codon.
until a stop codon is reached
How can polypeptides be further modified
they can be folded in the rough endoplasmic reticulum and can be modifeid in the golgibody by having lipid and sugar groups added
