1.5 nucleic acids Flashcards
what is a nucleotide composed of? and how does it get made?
one or more phosphate group
pentose sugar
organic base (containing nitrogen)
a condensation reaction
what does ATP stand for?
adenosine triphosphate
what does atp do?
provides the necessary energy for most reactions in most cells
how does energy get produced from ATP?
the bond from the condensation reaction between the middle and terminal phosphate group is broken by the enzyme ATPase by catalysing its hydrolysis,
letting energy be released to be used by the cell
what is adenosine triphosphate composed of?
- three phosphate groups
- bonds formed from a condensation reaction
- ribose (a pentose sugar)
- adenine (organic base)
how does ATP turn into ADP? is it reversible?
ATP + water = ADP + p1 + energy
what is the addition of the phosphate group back to ADP to form ATP?
phosphorylation
how does ADP turn into ATP?
ADP and p1 need energy in the form of glucose in respiration or from absorbing light in photosynthesis
where is ATP produced in the cell?
cytoplasm, mitochondira, chloroplasts
what 5 functions does ATP provide energy for?
(mamns)
metabolic processes (build larger complex molecules from smaller molecules)
active transport (change shape of carrier protein to be carried against conc grad)
movement (muscle contraction)
nerve transmission
secretion (packaging and transport of products into vesicles)
define an exergonic reaction?
e e
energy released
define endergonic reaction?
energy needed
what are the 5 advantages of ATP vs glucose?
(i, 1, s, s, e)
- a single reaction that releases immediate energy
- only one enzyme is needed to release energy from ATP (ATPase)
-ATP releases energy in small amounts wherever it is needed (lots of energy from glucose is not always needed) - ATP is soluble and easily transported
- ATP is a common source of energy for chemical reactions, making cell efficient
what are the two nucleic acids?
Deoxyribonucleic Acid (DNA)
Ribonucleic Acid (RNA)
what are nucleic acids made of?
nucleotides
what are the bases and pentose sugar in DNA?
Adenine + Thymine
Cytosine + Guanine
Deoxyribose
what are the bases and pentose sugar in RNA?
Adenine + Uracil
Cytosine + Guanine
Ribose
what bases are purine? what is its structure?
(who is pure?)
U
Adenine and Guanine
double ring structure
what bases are pyrimidine? what is their structure?
(pyramids cut)
Thymine, Uracil, Cytosine
single ring structure
are purine and pyrimidine complimentary?
yes, bonded with hydrogen bonds
describe DNA?
- each DNA is double-stranded polymer of nucleotides/polynucleotides
- alternating phosphate group and pentose sugar give the polynucleotides structure
- pentose sugar is deoxyribose
- four bases are:
adenine + thymine
cytosine + guanine - purine bases bind with the pyrimdine bases
- base pairing link the polynucleotides
- polynucleotides are anti-parallel
- twisted into a double-helix, maintained by H bonding
- completely equal distribution of each A/T and C/G but unequal amounts of them
what is the function of DNA?
replication
protein synthesis
describe RNA?
- single-stranded polynucleotide
- contains pentose sugar = ribose
- organic bases of:
adinine + uracil
guanine + cytosine - no thymine
- much shorter than DNA
what are the three types of RNA?
transfer RNA (tRNA)
messenger RNA (mRNA)
ribosomal RNA (rRNA)
what is the function of messenger RNA?
- synthesised from nucleus
- used in transcription - carries genetic code from DNA to ribosome
- each strand codes for one gene (during translation, it attaches to the ribosome and has codons) and therefore, one polypeptide chain
what is the function of ribosomal RNA?
- found in the cytoplasm
- a part of ribosomes
- ribosomes synthesised in the nucleus, then get transported out into the cytoplasm
-ribosomes are sit of protein synthesis
what is the function of transfer RNA?
- has anti-codons and an amino attachment site
- transports amino acids to ribosomes (protein synthesis)
- anti-codon form a complex with complimentary codons of the mRNA to “check the amino acid” for it to be added to the polypeptide chain.
what occurs during DNA replication?
- hydrogen bonds holding the base pairs together break and the two halves of the DNA molecule separate, this is catalysed by DNA helicase
- DNA unwinds and unzips
-DNA strands seperate, addition of free nucleotides (catalysied by DNA polymerase) to the exposed bases of both of the strands. - nucleotides now join their complimentary pairs
- this forms two identical DNA molecules, one newly synthesised and one from the original molecule.
describe the theory of semi-conservative DNA replication?
- every DNA is a template for now DNA, and that each new DNA strand is made of and original strand and a newly synthesised one
what was the experiment that Meleson and Stahl did to prove the semi-conservative theory?
cultured bacterium Escherichia coli, containing amino acids with heavy N15, which was incorporated into the bacteria nucleotide in its nitrogen-containing base.
describe the first step to Meleson and Stahls experiment?
- extracted bacterial DNA and centrifuged it
- this DNA settled at a low point in the tube as it contained N15 (heavy isotope)
describe the second step to Meleson and Stahl’s experiment?
- bacteria was washed and transferred to a tube containing a lighter isotope (N14) and replicated once
- after replication, DNA is centrifuged and and shown to have a midpoint density as half the strand was made of N14 and the other half was N15.
- this is hybrid DNA
describe the third step to Meleson and Stahls experiment?
the DNA was centrifuged again, and the DNA settled at midpoints (both N14 and N15) and high points (just N14)
what makes up a gene?
a certain sequence of nucleotides (bases, pentose sugar, phosphate group) and multiple codons, one codon codes for one amino acid.
what does a gene do?
genes carry the genetic info to build a protein with primary structure (after being copied in transcription)
define intron?
non-coding sections of DNA
define exon?
coding sections of DNA
what does a mRNA molecule contain before it leaves the nucleus? what gets removed before leaving the nucleus through what?
both introns and exons, the introns get removed and the exons join together, before the mRNa can leave the nucleus
through post transcription, modification of pre-mRNA
why are exons and introns advantageous?
a single gene can code for multiple polypeptide chains as different exons and introns are needed for different proteins.
what are the steps to transcription? describe and explain?
DNA does not leave the nucleus but acts as a template for the production of mRNA; it is copied from the cistron, which codes for a specific polypeptide
- DNA unwinds and unzips at the cistron, catalysed by DNA helicase by breaking the hydrogen bonds between complementary bases
- RNA polymerase attaches to the ONE DNA strand to be copied going from 5’ to 3’ (direction)
- free nucleotides align opposite complementary nucleotides on DNA strand to copy genetic info
- RNA moves along the DNA strand, forming bonds with nucleotides, and synthesises a molecule of mRNA along the unzipped DNA
- Behind the RNA polymerase, the DNA strand rejoins to form a double helix
- mRNA carries the DNA code out of the nucleus through the nuclear pores to cytoplasm where it attcahes to a ribosome.
what enzyme attaches to a cistron to copy the DNA?
RNA polymerase
what is a polysome system?
a group of ribosomes all translating the same strand of mRNA
describe and explain how translation works?
- mRNA attaches to a ribosome (large & small subunits)
- ribosome moves along the mRNA and reads the code
- mRNA has codons (triplets of bases), which each code for an amino acid
- on the tRNA, there are complementary anti-codons which align with the mRNA codons
- there are amino acid binding sites on the opposite side of the tRNA where the amino acids are attached
- a codon-anticodon complex occurs, which ensures the carried amino acid from activation in the cytoplasm matches the codon and is in the correct position to form a polypeptide
- the correct amino acid is now transferred to another tRNA molecule, creating a chain
- the discarded tRNA goes back to the cytoplasm as the ribosome moves 3 bases over
- peptide bonds form between adjacent amino acids on the same tRNA via a condensation reaction.
what happens to the tRNA molecule released from the ribosome?
- it goes back to the cytoplasm and is free to collect another identical amino acid from the amino acid pool in the cytoplasm
- this is amino acid activation which energy is required in the form of ATP
define elongation?
two amino acids close enough for a peptide bond to form between them
define initiation?
ribosome attaches to a start codon at one end of the mRNA
define termination?
amino acids are added until the ribosome reaches a stop codon, then the ribosome detaches from the mRNA and a polypeptide chain is released.
how many genes are needed to code for 1 polypeptide chain?
1
how many genes would be needed to code for haemoglobin? why?
4 because it has quaternary structure containing 4 different proteins/polypeptide chains
how many genes would be needed for collagen?
1, as 3 identical polypeptide chains
what shape is tRNA and mRNA?
tRNA is a clover leaf shape
mRNA is linear
how does a phosphate group get broken off ATP?
ATPase through a hydrolysis reaction
what does the large subunit contain?
two binding sites for two tRNA
what does a small subunit contain?
one binding site for mRNA
what is genetic code?
denegerate, linear, non-overlapping universal triplet code for the production of polypeptides
DONUT
what forms betweeen codon and anti codon?
hydrogen bonds
how much energy is released when ATP undergoes hydrolysis into ADP and a p group?
30.6 kj per mole
