Nucleotides

What does a nucleotide consist of?

Sugar

Phosphate group

A base (A, T , C or G)

What is DNA?

Polymer made of repeating units of nucleotides

Has deoxyribose sugar

What bond is between the complementary bases?

Hydrogen bonds

What are the two nuclei acids?

DNA and RNA are polymers - individual nucleotides are the monomers that build up the polynucleotides

DNA = deoxyribonucleic acid

DNA = ribonucleico acid

Bases in RNA

A = U

C = G

What is a purine

Contains 2 carbon - nitrogen rings

A and G

What is a pyrimidine?

Contains one carbon - nitrogen ring

T C and U

How may strands does DNA have compared to RNA

DNA has double strands

RNA is single strand

How many hydrogen bonds between AT and CG?

A - T = 2

C - G = 3

Where is the hydroxyl and Pentose groups in DNA?

Hydroxyl group on carbon 3 of pentose sugar and phosphate group on carbon 5 of nucleotide

What is bonded to carbon 2 on DNA and RNA?

DNA = H group

RNA = hydroxyl group, more susceptible to hydrolysis

How do phosphodiester bonds form?

Condensation reactions occurs between the phosphate group of one nucleotide and the pentose sugar of the other via condensation reactions

Make a sugar phosphate backbone

Describe how 2 single polynucleotide strands join to make a double helix

Hydrogen bonding between base pairs

2 hydrogen bonds between at and 3 between cg

Complementary base parking

Antiparallel strands twist to make double helix

What is ATP consisted of?

Adenine, Ribose, 3 phosphate groups

AMP = 1 phosphate group

ADP = 2 phosphate groups

ATP = 3 phosphate groups

What is ATP?

Chemical energy needed to fuel biological activities

Is produced continuously

What is the role of ATP?

Stores most of the energy in the third bond of the molecule

Energy is release when the bond is broken to release the third inorganic phosphate

What is phosphorylation

Adding a phosphate group

How is ATP formed

Using ATP synthase,

ADP bonds to a third norganic phosphate group using energy from glucose

What does anti parallel mean?

Parallel but with chains running in oppose directions

3 to 5 direction

5 to 3 direction

Explain the steps of purification of DNA

1. Prepare your equipment - kiwi, pineapple juice, salt , detergent and cold alchohol

2. Make the extraction solution - water, salt and detergent

3. Prepare fruit mush using pestle and mortar

4. Add extraction solution and leave for 20 min - detergent breaks down cell membrane so DNA can be released

5. Filter the solution - gets rid of pulp

6. Purify DNA by removing proteins bound to DNA using pineapple juice

7. Precipitating the DNA - DNA mixes with alcohol and produced white clump of DNA

Purpose of detergent

Breaks down cell membrane

Processs of precipitating DNA from cells

Cell surface membrane and nuclear envelope are physically broken down by detergent

Mixture is filtered

DNA is precipitated using ethanol

Why does DNA need to replicate

Before a cell divided, it needs to copy itself so each new cell has a copy of DNA

Explain Semi conservative replication (1)

DNA helicase causes 2 strands to seperate as it breaks the hydrogen bonds between the bases

Forms 2 strands

Semi conservative replication (2)

Each original strand is a template

Free nucleotides are attracted to exposed complementary bases

Semi conservative replication (3)

DNA polymerase joins free nucleotide to the original strand (phosphodiester bond)

Forms sugar phosphate backbone

Hydrogen bonds form between bases

Semi conservative replication (4)

2 identical strands forme

Nucleotides joined to from a polynucleotide

Each strand has half the oriental DNA

Evidence for the semi conservative replication - theory

Matthew Meselsohn and Franklin Stahl used E. coli

Grown in a medium containing heavy isotope nitrogen 15

This bacteria used the 15N to make the purine and pyrimidine bases in its DNA

Explanation of results - Semi conservative replication

Parental generation - both strands made with 14N

First generation - DNA made of one strand 15N and one strand 14N

Second generation - some DNA made of 2 strands of 14N and some with mix

Explain what genes are

each gene has a different sequence of bases

Gene code for a specific polypeptide

Each gene is on a fixed position on a chromosome

sequence of three bases code for..

Amino acid

The order of the bases are important - why?

They control the order the amino acids are assembled to produce a protein

Structure of amino acid

Amino group - NH2

Carboxyl group - COOH

r group

What is a codon

Sequence of 3 nucleotide bases that code for an amino acid

Degenerate code:

More than one codon codes for each amino acid

Non - overlapping code

Only read once

Universal code

The same codon codes for the same amino acids in all organisms

How does DNA control all activities in cell?

Chemical reactions are controlled by enzymes, which are proteins

DNA codes for proteins

Why may 2 different species of Actium have different percentages of guanine?

Different proteins

Different base sequence

Different genes

Name the DNA structure

Explain mRNA:

Made in the nucleus, small enoug to pass through nuclear pores

Carries copy of genetic code for a protein to the ribosome in cytoplasm

Uses Uracil instead of thymine

Describe tRNA

One strand folded in on itself

Amino acid determined by anticodon at top

Anticodon is complementary to the codon on mRNA

Transcription process

DNA helicase seperate the 2 trends pf DA by breaking the H bonds

RNA polymerase = moves along one strand of DNA, causing RNA nucleotides to align with complementary bases and join together using a phosphodiester bond

As it moves along, DNA strands rejoin behind it

Describe how mRNA is formed by transcription in eukaryotes

Hydrogen bonds break - DNA helicase

One DNA strand is a template, RNA snucleotides align by complementary bases

Uracil pairs with adenine instead of thymine

RNA polymerase joins nucleotides with phosphodiester bonds

Explain process of translation (1) until next codon

One end of the mRNA attaches to the ribosome

TRNA molecule with complementary anticodon attaches to ribosome

Second tRNA molecule binds to next codon

Exaplin process of translation (2)

Ribosomes move along mRNA and join 2 amino acids together by a peptide bond

Continues until stop codon is reached