Nucleic Acids Flashcards
Structure of Nucleotide
Nitrogenous/Organic base
Deoxyribose sugar (pentose sugar)
Phosphate group
Bonds in DNA - Phosphodiester bond
Forms between the deoxyribose sugar on one nucleotide and the phosphate group on other
Forming a dinucleotide
Bonds in DNA - hydrogen
Weak bonds between the bases
join two strands together
Bonds in DNA - hydrogen
Weak bonds between the bases
join two strands together
How is DNA adapted to be a storage molecule?
Sugar phosphate backbone - provides strength and stability
Large molecule so can store lots of information
Coiled into a helix so compact
Double stranded so replication can occur semi conservatively
mRNA
Copy of a gene from DNA
Much shorter than DNA so can leave the nucleus
Short-lived - only needed temporary to create a protein
Single stranded - every 3 bases code for a specific amino acid. these 3 bases are codons
tRNA
Only found in the cytoplasm
Single stranded but folded into a clover leaf shape which is held in place by hydrogen bonds - approximately 75 nucleotides long
Attaches to one of the amino acids and then transfers this to the ribosome to create the polypeptide
A reigon of 3 bases is an anticodon
Chargaffs rule
A purine always pairs with a pyramidine
Purines:
Adenine
Guanine
Pyramidines:
Thymine
Cytosoine
There will be equal amounts of adenine and thymine
and equal amounts of cytosine and guanine
If we know one we can work out the other.
Bonds in ATP
The bonds between the end 2 phosphates are unstable and have a lower activation energy. This means they are easy to break. ATP/energy is released once broken.
Hydrolysis of ATP
ATP —> ADP + Pi
H20 required
Energy released
Condensation of ATP
ATP <——– ADP + Pi
H2O relrased
energy used up
What happens to the phosphate that is released when ATP is hydrolysed
The phosphate group is often transferred to other molecules to lower their activation energy and make them more reactive (phosphorylation)
What is a Gene?
A gene is a section of DNA that codes for a particular protein/polypeptide and codes for functional RNA
Genes in DNA
DNA molecules have many genes along their length and have a specific position called the locus.
Between the genes are non coding repeats. The number of repeats vary from person to person so can be used in genetic fingerprinting.
Give two ways in which the hydrolysis of ATP is used in cells
Metabolic reactions such as respiration
To add phosphate to other substances and make them more reactive
Describe how ATP is resynthesised in cells
From ADP and phosphate
By ATP synthase
DNA is a polymer of nucleotides. Each nucleotide contains an organic base.
Explain how the organic bases help to stabilise the structure of DNA
Hydrogen bonds between the base pairs hold two strands together
Many hydrogen bonds provide strength
Give three ways in which the DNA in a chloroplast is different from DNA in the nucleus
DNA in a chloroplast is shorter
DNA in a chloroplast is circular
DNA in a chloroplast has fewer genes
Explain how a change in a sequence of DNA bases could result in a non functional enzyme
Change in amino acids
Change in hydrogen bonds ——> change in tertiary structure
Enzyme-substrate complexes form
Structural differences between a DNA molecule and an mRNA molecule
DNA has thymine whereas mRNA has uracil
DNA has deoxyribose sugar, mRNA has a ribose sugar
DNA is larger whereas mRNA is shorter
DNA is double stranded whereas mRNA is single stranded
Structural differences between DNA and tRNA
DNA has thymine whereas tRNA has uracil
DNA is linear whereas tRNA is clover-leaf shaped
DNA has a deoxyribose sugar, tRNA has ribose
Give one difference between the function of DNA and RNA
DNA - holds genetic information
RNA - Transfers genetic information from DNA to ribosomes
What are ribosomes formed from?
RNA and proteins
Why did scientists initally doubt that DNA carried the genetic code?
Due to the relative simplicity
What is a locus?
The location of a gene on a particular DNA molecule
