Pentose monosaccharide, nitrogenous base, phosphate group
State the two main types of nucleic acid
DNA and RNA
Describe the similarities and differences between the nucleotides of DNA and RNA
DNA - deoxyribose, A C G T, phosphate-sugar backbone pentose sugar, phosphodiester bond RNA - ribose, A C G U, phosphate, pentose sugar ,phosphodiester bond
List the five full names of the 5 possible nitrogenous bases in nucleic acids
Adenine Cytosine Guanine Thymine Uracil
Name the two types of nitrogenous base and state which bases belong to each type
Pyrimidines (thymine, cytosine, uracil [tiny])
Purines (adenine, guanine)
Outline the structure of the two types of nitrogenous base
Purine- 2 rings, pyrimidines have 1 ring
State the name of the reaction which joins nucleotides to other nucleotides and the name of the reaction which breaks phosphodiester bonds
Forming - condensation
Breaking - hydrolysis
State 3 main types of activity for which cells require energy
Movement [protein fibres that cause muscle]
Synthesis [making proteins]
Transport [pumping molecules across membranes using active transport]
(EMESTEE)
Draw and label a diagram of ATP and ADP
List two similarities and two differences between ATP and DNA/RNA nucleotides
Both have adenine, ribose and 2 phosphates however ATP has an extra phosphate
Draw a diagram to show the ATP cycle
State 5 properties of ATP and explain why each makes it suited to function as an energy transfer molecule
Small so moves easily into and out of cells
Water soluble
Contains bonds with not too much energy but not too little
Releases energy in small quantities
Easily regenerated
Define the term phosphorylation
the addition of a phosphate group to a molecule
Draw and label a diagram of the structure of DNA
Define the terms complementary base pairing
CG - 3 hydrogen bonds
AT - 2 hydrogen bonds
Define the term sugar phosphate backbone
The sugar phosphate backbone is an important structural component of DNA linked by phosphodiester bonds
Define the term anti parallel
Two parallel strands running in opposite directions
Define the term double helix
The shape of DNA as two strands of DNA strands which twist to as helices
Define the term strand in relation to DNA
one DNA polymer
Explain how purines and pyrimidines are arranges in the complementary base pairing rules
One pyrimidines bonds to its complementary purine
Describe the significance of the double stranded complementary base paired nature of DNA for its function
Complementary base pairing - allows itself to replicate easily as nucleotides will match by themselves
It's stable- from the H bonds and backbone
Describe and explain the importance of the steps in the isolation and purification of DNA by precipitation
Grind in pestle and mortar to break cell walls
Add detergent to break down cell membranes
Add salt - breaks hydrogen bonds between DNA and water molecules
Add protease - break down proteins associated with DNA in the nucleus
Add ethanol - causes DNA to precipitate out of solution
Explain why DNA replication is necessary
DNA replication is needed because the two daughter cells produced as a results of cell division need to be genetically identical therefore all the parent cell DNA must be fist repliated
Define the term semi-conservative replication
Each offspring molecule has one original strand and one replicated strand
Draw and annotate a diagram to show the sequence of events in DNA replication
Describe the sequence of DNA replication
1. DNA helicase breaks H bonds to separate strands
2. Free nucleotides attracted to their complementary bases and form their H bonds
3. DNA polymerase catalysing the formation of phosphodiester bonds
4. Two identical molecules formed with one old and one new strand
State the role of the enzymes DNA polymerase and DNA helicase in DNA replication
DNA polymerase - catalyses formation of phosphodiester bonds
DNA helicase - breaks hydrogen bonds between complementary base pairs unzipping the molecules
Explain how the results of Meselson and Stahl's experiment demonstrate that DNA is replicated by semi conservative replication
This was because they first grew E. coli in N-15, so all DNA was heavy. They then grew it in N-14 and the DNA became lighter. After another division in N-14 two distinct bands formed (one of only N-14 and the other of N-14 and N-15) demonstrating that one strand is conserved and one is synthesised.
Describe how and explain why DNA replication occurs by continuous replication of one strand and discontinuous replication of the other strand.
DNA polymerase can only travel in 3'-5' direction forming in 5'-3', therefore the leading strand is replicated continuously but the lagging strand has to be replicated in the opposite direction is segments called Okazaki fragments then joined together by DNA ligase.
Explain the importance of DNA replication converting genetic information with accuracy
Must be copied accurately so daughter cells are identical and can perform their set function
Define the term mutation
a permanent change in the base sequence of DNA
Outline the sequence of bases in DNA can code for the primary structure of a polypeptide chain
The code in the base sequences is a triplet code
The sequence of triplets coding for the amino acids to make a protein is known as a gene.
Define the term codon
A unique three base sequence (triplet) of DNA or RNA coding for an amino acid
Define the term gene
A sequence of DNA that contains the complete sequence of bases to code for a protein
Explain why the genetic code is a triplet code, the value of it being non overlapping and the reason for it being degenerate
Triplet code - 3 bases make a codon which n turn codes for an amino acid
Non overlapping - DNA is read 3 at a time
Degenerate - as multiple codons code for the same amino acid
Universal - the same amino acid codes apply for all organisms
Outline how mutations can alter the structure of a protein
A different amino acid may be coded for as the codon is different. Primary protein structure will change and tertiary structure could change due to different R group interactions. Protein's function could change as well
Define the term transcription
the process of copying DNA to make mRNA to be transported out of the nucleus by the nuclear pores to the site of protein synthesis
Define the term translation
the process by which the complementary code carried my mRNA is decoded by tRNA into a sequence of amino acids at the ribosome
State the four types of RNA
mRNA, tRNA, rRNA, pre-mRNA
Draw a table to compare the structure and function of mRNA, tRNA and DNA
mRNA - chain of amino acids making codons
tRNA - has some paired bases but is folded in a way so that three bases (anticodon) are not paired and are at one end of the molecule. They bind to complementary codons on the mRNA and are also attached to an amino acid.