Protein synthesis Flashcards
What elements do nucleotides contain
carbon, hydrogen, oxygen, nitrogen ,phosphorus
What 3 features does a nucleotide contain
- pentose monosaccharide
- phosphate groups
- nitrogenous base
What is a phosphodiester bond
- condensation reaction
- Phosphate group at C5 of the pentose sugar forms a covalent bond with the hydroxyl group at the third carbon of the next nucleotide
Features of pyrimidines, which bases
- Smaller bases
- Contain single carbon ring structures
- Thymine and Cytosine
Features of purines, which bases
- Larger bases
- contain double carbon ring structures
- Adenine and Guanine
How many bonds do bases form when they join
- Thymine + Adenine= 2 hydrogen bonds
- Cytosine + Guanine= 3 hydrogen bonds
What is mRNA
- messenger RNA
- a short section of the long DNA molecule corresponding to a gene
- polymer of nucleotide monomers
How is the double helix of DNA formed, features of it
- 2 strands of polynucleotides coiled into a helix
- Hydrogen bonds between bases join the 2 strands
- the 2 strands are antiparallel- opposite directions
How to extract DNA
- grind sample in mortar and pestle, TO BREAK CELL WALL
- mix sample with detergent (breaks membrane, releases cell contents)
- add salt, to break H bonds between DNA and water
- add protease enzyme, to break down proteins associated with DNA
- add layer of ethanol on top, causing DNA to precipitate out, forms white precipitate
- pick up DNA by spooling onto a glass rod
What is semi-conservative replication, process of it
- hydrogen bonds between strands broken
- free DNA nucleotides pair with exposed complementary bases
- hydrogen bonds form between strands again, phosphodiester bonds form between new adjacent nucleotides
- produces 2 new molecules of DNA, each with 1 old and 1 new strand
Role of DNA helicase
Unwinds/separates 2 strands of the double helix
Role of DNA polymerase
Catalyses the formation of phosphodiester bonds between nucleotides
What is a gene
A section of DNA that contains the complete sequence of bases (codons) to code for an entire protein
What is meant by universal
- all organisms use the same genetic code and system
- however, the sequences of bases coding for each protein are different
What is degenerate code
-Many amino acids can be coded for by more than 1 codon
- 20 amino acids, 64 codon possibilities
Definition of transcription
The process by which a cell makes an RNA copy of a piece of DNA
Why does transcription occur
DNA is to large to leave the nucleus, genes must be copied and transported to ribosome for protein synthesis
Role of amino acid Methionine
- initiates protein synthesis
- initiation codon recognised by anticodon on mRNA
Summary of stages in transcription
- DNA helicase breaks H bonds, free RNA nucleotide bases pair with complementary bases on the antisense strand
- Phosphodiester bonds form between free RNA nucleotides by RNA polymerase, transcription stop at end of gene
- mRNA detaches from the DNA strand, leaves nucleus through a nuclear pore, travels to ribosome
- DNA double helix reforms
Sense vs antisense strand
- Sense strand= codes for protein
- antisense strand= acts as template strand- bases forming RNA will be complementary to antisense strand so will code for protein, as will have the same sequence as the sense strand
Definition of translation
- the process by which mRNA is decoded and translated into a sequence of amino acids
Role, structure, featuRes of tRNA
- transfer RNA
- made up of a strand of RNA, folded so 3 bases/anticodons are at 1 end of the molecule
- anticodon binds to complementary codon on mRNA
- carry an amino acid corresponding to the codon
- when tRNA anticodons bind to complementary codons, amino acids are brought together in the sequence for the protein
Role of ribosomes in transcription/translation
- act as the binding site for mRNA and tRNA
- catalyse assembly of the protein
Summary of process of translation
- mRNA binds to subunit of ribosome at start codon, tRNA with complementary anticodon binds to mRNA start codon
- another tRNA carrying the corresponding amino acid binds to the next codon on the mRNA, max 2
- first amino acids then transferred to the amino acid on the second tRNA by a peptide bond
- ribosome moves along mRNA, releasing the first amino acid
- stages repeat, until ribosome reaches stop codon, polypeptide is released
Peptidyl transferase
- enzyme that catalyses joining of amino acids
What does translation form
-the primary structure of a protein
- complete sequence of amino acids
Structure of ATP
- nitrogenous base, always ADENINE
- ribose pentose sugar
- 3 phosphate groups
Function of ATP
- supply energy inside cells in a usable from
- its used for energy transfer in cells of all living things
Equation for ATP energy release, type of reaction
- ATP + water = ADP + P + energy
- hydrolysis
Key properties of ATP
- small
- easily regenerated
- water soluble
- energy released in small quantities
- contains bonds between phosphates with intermediate energy
Differences between RNA and DNA
- Uracil rather than thymine
- uracil bonds with A
- RNA small enough to leave nucleus and travel to ribosomes
