nucleotides and nucleic acids

nucelic acids

like dna and rna made up of nucleotides

nucleotides structure and bonding

phosphate bonded to the sugar through ester bond

base and sugar bonded through a glycosidic bond

nucleotides roles

• nucleic acids (DNA RNA)

• phosphorylated when they contain more than 1 phosphate group (ATP , ADP)

• coenzymes like in NADP ,NAD

pyrimidines

• single ring structures

• cytosine, thymine , uracil

purines

• double ring structure

• guanine , adenine

antiparallel

• 2 strands of dna in opposite dirextions

• one has a 5’ end and one has a 3 end

• lie next to eachother

histones

in eukaryotic cells dna winds around it

sugar phosphate backbone

a polynucleotide formed by condensation reactions forming the sugar phosphate backbone which protects base pairs inside keeping the molecule very stable

6 stages of mitosis

• interphase

• prophase

• metaphase

• anaphase

• telophase

• cytokinesis

conservative replication theory

double helix copied as a whole

1 new and one parental DNA

semi conservative replication theory

dna strands unwind and new strands are synthesised 2 hybrid DNA molecules produced

stage 1 of DNA replication

gyrase ( enzyme) unvinds a small part of the double helix

stage 2 of DNA replication

DNA helicase ( enzyme) breaks the hydrogen bonds between strands

stage 3 of DNA replication

free nucleotides in the cytoplasm bond to exposed bases catalysed by DNA polymerase …… they form hydrogen bonds

stage 4 of DNA replication

new phosphodiester binds form between the new strands nucleotides

stage 5 of DNA replication

dna winds itself back up

3 enzymes used in dna replication

• gyrase

• dna helicase

• dna polymerase

leading strand

• 5’-3’

• uses dna polymerase ezyme

lagging strand

• 3’-5’

• rna primer is required to start the process

• okazaki fragments made separately un the nucleus form the lagging strand

• uses DNA ligase to stick the fragments to the lagging strand

replication fork

a Y-shaped structure that forms dna during replication

transcription definition

strand of mRNA is synthesised to form a particular gene template

transcription process

1. gene unwinds and unzips causing hydrogen bonds to break

2. rna polymerse catylises formation of a complementary mRNA strand

3. completed mRNA strand passes iut through the neuclear envelope and attaches to a ribosome

translation definition

converting mRNA into a sequence of amino acids in order to produce a protein

translation process

1. mRna template attaches to the ribosome

2. tRNA molecules bring amino acids which bind to the complementary codon on the mRNA

3. as ribosomes moves along it reads it when 2 amino acids are adjacent to eachother ATP is required to form a peptide bond

4. once polypeptide formed mRNA breaks down and is recycled

5. polypetide chain is folded into its correct structure