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nucleotides and nucleic acids (nucleotides (dna (adenine and guanine=…
nucleotides and nucleic acids
nucleotides
nucleotides are used to make nucleic acids
made of....
a pentose sugar
a nitrogenous base
a phosphate group
all nucleotides contain the elements C, H, O,N,P
Nucleotides are MONOMERS that make up dna and rna (types of nucleic acid)
dna is used to store genetic information
rna is used to make proteins from the instructions in dna
ADP and ATP are types of nucleotide used for storing and transporting energy in cells
dna
the pentose sugar in dna= deoxyribose
each dna nucleotide has the same sugar and phosphate group but the base can vary
possible bases: guanine (G), Thymine (T), Cytosine (C), Adenine (A)
adenine and guanine= purines
purines contain two carbon-nitrogen rings joined together
cytosine and thymine= pyrimidines
a pyrimidine contains only one carbon- nitrogen ring (its smaller)
a molecules of dna contains TWO polynucleotide chains twisted into a double helix
anti parallel sugar phosphate backbone
rna
rna contains nucleotides with ribose sugar
rna has a phosphate group and 4 different bases
CONTAINS URACIL INSTEAD OF THYMINE AS A BASE
rna is made up of a single polynucleotide chain
shorter polynucleotide chain
ADP and ATP are phosphorylated nucleotides
to PHOSPHORYLATE a nucleotide you add one or more phosphate groups to it
ADP contains the base adenine, the sugar ribose and TWO phosphate groups
ATP contains the base adenine, the sugar ribose and THREE phosphate groups
ATP provides energy for chemical reactions in the cell
ATP is synthesized from ADP and inorganic phosphate using energy from an energy releasing reaction e.g. respiration
energy is stored in the phosphate bond
when this energy is needed by the cell ATP is broken back down into ADP and inorganic phosphate. energy is released by the phosphate bond and is used by the cell
help regulate metabolic pathways
components of coenzymes (NAD, FAD)
in eukaryotes= dna is wound into chromosomes, loop of dna WITHOUT HISTONE PROTEINS in mitochondria and chloroplasts
in prokaryotes= dna is in a loop (plasmid), it is 'naked' (not wound around histone proteins)
polynucleotides and dna
nucleotides join together to form polynucleotides
the nucleotides join together by the phosphate group of one nucleotide and the sugar of another via a CONDENSATION forming PHOSPHODIESTER BOND
the chain of sugars and phosphates= sugar-phosphate backbone
polynucleotides can be broken down into nucleotides again by breaking phosphodiester bonds by HYDROLYSIS
double helix
two polynucleotide chains join together by HYDROGEN BONDS between the bases
complementary base pairing= each base can only join with one particular partner
adenine and thymine
cytosine and guanine
a purine and a pyrimidine
TWO hydrogen bonds form between A and T and THREE hydrogen bonds form between C and G
two ANTIPARALLEL polynucleotide strands twist to form double helix
precipitation reaction (purifying dna)
1) break up cells in sample using blender
2) make up a solution of detergent (washing liquid), salt (sodium chloride) and distilled water
3) add broken up cells to beaker containing detergent solution and incubate beaker in water bath at 60 degrees for 5 minutes
4) place mixture in ice bath then filter and transfer into a clean boiling tube
5) add protease enzymes to the filtered mixture and then add rnase enzymes
6) slowly dribble cold ethanol into the testtube so it forms a layer on top of the mixture
7) wait for a minutes as white precip forms
dna replication
semi conservative replication
2) each original strand acts as a template for a new strand. Free floating DNA nucleotides join to exposed bases on each original template by complementary base pairing
3) the nucleotides of the new strand are joined together by dna POLYMERASE. this forms the sugar-phosphate backbone. Hydrogen bonds form between the bases of the original and new strand and twist into a double helix
4) each new strand contains 1 original and one new strand, strands are identical
1) HELICASE breaks down the hydrogen bonds between the two polynucleotide dna strands. the helix unzips to form two single strands by gyrase enzyme
mutations
= a change to a dna base sequence
can alter the sequence of amino acids in a protein which can cause an abnormal protein to be produced
enzymes proof read DNA sequence to reduce risk of mutations
genes and protein synthesis
genes= instructions for making protiens
a gene= a sequence of dna nucleotides that codes for a polypeptide (forms primary structure of protein)
different proteins have different number and order of amino acids
the ORDER of bases in the gene that determines the order of amino acids in a particular protein
each amino acid is coded for by a sequence of 3 bases (TRIPLET) in a gene
different sequences of bases code for different amino acids. so the sequence of bases in a gene is a template that's used to make proteins in protein synthesis
dna is copied onto rna
dna molecules are found in the nucleus of the cell but ribosomes are found in cytoplasm
dna is TOO LARGE to move out of the cell so a section is copied onto mRNA (transcription)
the mRNA leaves the nucleus and joins with a ribosome in the cytoplasm where it can be used to synthesise a protein (translation)
types of rna
messenger (mRNA)
made in nucleus
3 adjacent bases are called a codon
carries the genetic code from the nucleus to the cytoplasm where its used to make a protein during translation
transfer (tRNA)
found in cytoplasm
has an amino acid binding site at one end and a sequence of 3 bases on the other end (anticodon)
carries the amino acids that are used to make proteins to the ribosomes during translation
ribosomal (rRNA)
forms the two subunits in a ribosome
the ribosome moves along the mRNA strand during protein synthesis
helps catalyse the formation of peptide bonds between amino acids
genetic code is non overlapping, universal and degenerate
genetic code= the sequence of codons in dna or mrna which codes for specific amino acids
in the genetic code each base triplet is read in sequence (separate from triplet before and after) - non overlapping
some amino acids are coded for by more than one base triplet - degenerate
some triplets are used to tell the cell when to start and stop the production of protein (stop and start codons)
the same specific base triplets code for the same amino acids in all living things- universal
transcription and translation
transcription
1) rna polymerase attaches to dna double helix at the beginning of a gene
2) hydrogen bonds between two dna strands break and molecule uncoils
3) one strand is used as a template to make an mrna copy
4) the rna polymerase lines up free rna nucleotides alongside template strand. complementary base pairing means that mrna strand ends up being a complementary copy of the dna template (except uracil instead of thymine)
5) once the rna nucleotides have paired up with their specific bases on the dna strand theyre joined together forming mrna molecule
6) the rna polymerase moves along dna separating strand and assembling the mrna strand
7) hydrogen bonds reform once rna polymerase pass by and strands coil back into double helix
8) when rna polymerase reaches a stop codon it stops making mrna and detaches from dna
9) mrna moves out of nucleus through nuclear pore and attaches to ribosome in cytoplasm
translation
occurs in ribosomes
during translation amino acids are joined together to make a polypeptide chain following the sequence of codons carried by the mrna
1) mrna attaches to ribosome and trna molecules carry amino acids to ribosome
2) trna molecule attaches to mrna by complementary base pairing
3) a second trna molecule attaches to the next codon on mrna in the same way
4) rRNA catalyzes the formation of peptide bond between 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
5) a third trna molecule binds to the next codon on the mrna. its amino acid binds to the first two and the second trna moves away
6) process continues producing a polypeptide chain until theres a stop codon on the mrna
7) the polypeptide chain moves away from ribosome
requires ATP