Proteins and Genes (chapters 2-3) Flashcards
Exogonic
High energy to low energy
Endogonic
Low energy to high energy
3 Stages of Transcription
- Initiation
- Elongation
- Termination
Transcription - Initiation
- RNA polymerase binds to DNA at promoter region
- Promoter region contains TATA box - recognised by ‘TATA’ sequence
- Once bound, RNA polymerase unzips two DNA strands
Transcription - Elongation
- RNA polymerase moves along template strand to form RNA strand
- RNA synthesized in 5’ to 3’ direction
Transcription - Termination
- RNA polymerase detaches from DNA
- Transcription stops, DNA strands return to normal double helix formation
3 Stages of Translation
- Initiation
- Elongation
- Termination
Translation - Initiation
- 5’ end of mRNA molecule binds to ribosome, read until start codon (AUG) is recognised
- tRNA with complementary anticodon (UAC) binds to ribosome, delivers amino acid methionine
Translation - Elongation
- mRNA molecule is fed through the ribosome so that the next codon can be matched to its complementary tRNA anticodon
- complementary tRNA molecules deliver specific amino acids to the ribosome, which bind to adjacent amino acids with a peptide bond via a condensation reaction
Translation - Termination
- Translation occurs until stop codon found
- The polypeptide chain is then released by the ribosome into the cytosol or endoplasmic reticulum.
Gene Expression 3 Stages
- Transcription
- RNA processing
- Translation
RNA Processing
Making mRNA from pre-mRNA
- Introns cut out, exons join together
- methyl cap added to 5’ end of pre-mRNA, poly-A tail added to 3’ end
- Once all this happens, becomes mRNA
Trinucleotide
Sequence of 3 adjacent nucleotides
pre-mRNA
unmodified RNA molecule
Exporting Proteins - Rough Endoplasmic Reticulum
Has ribosomes ‘rough’
- Makes proteins to be exported from the cell
- Proteins synthesized at ribosomes on Rough E.R.
Exporting Proteins - Golgi Aparatus
Stack of 4-8 flattened membrane sacs called Cisternae
- Modify and package proteins for export outside of the cell
- Proteins move from Rough E.R. to Cisternae in the Golgi Body, where proteins are modified by resident enzymes
- Modifications are necessary to target proteins to intended desination
Exporting Proteins - Vesicles
- Proteins released from Golgi in vesicles that bud off from the trans face
- Cargo proteins bind to specific membrane bound receptor proteins within the vesicle
- Cargo proteins change shape of receptors, telling vesicles where to go
Tryptophan
Rarest naturally occuring amino acid
Trp Operon
A series of genes within certain species of bacteria that encode for the production of the amino acid tryptophan
- ONLY IN PROKARYOTES
Attenuate
To reduce the effect of something
Leader
5’ untranslated region between promoter and operon genes
Domain
Distinct region of complex molecule
Surplus of Tryptophan
- When tryptophan is present, it binds to the repressor protein
- Repressor protein binds to the operator, blocking RNA polymerase from carrying out its function, therefore preventing transcription
Deficit of Tryptophan
- Insufficient quantity of tryptophan to bind to the repressor
- Causes the repressor protein to detach from operator region
- Allows RNA polymerase to transcribe trp structural gens
Proteome
all the proteins that are expressed by a cell or organism at a given time
Enzyme
an organic molecule, typically a protein, that catalyses (speeds up) specific reactions
Antibody
A protein produced by plasma cells during the adaptive immune response that is specific to an antigen and combats pathogens in a variety of ways.
Also known as immunoglobulin
Amino Acid Structure
composed of a central carbon atom, a carboxyl group, an amino group, an R-group,
and a hydrogen atom.
monomer
a molecule that is the smallest building block of a polymer
polymer
a large molecule that is made up of small, repeated monomer subunits
Peptide Bond
the chemical bond linking two amino acids
Levels of Protein Structure
- the sequence of amino acids (primary)
- arrangement into alpha-helices, beta-pleated sheets, or random coils (secondary)
- functional 3D shape of the protein (tertiary)
- bonding of multiple polypeptide chains together (quaternary).
Primary Protein Structure
the first level of protein structure, which refers to the sequence of amino acids in a polypeptide chain
Secondary Protein Structure
the level of protein structure where the amino acid chain forms either alpha-helices, beta-pleated sheets, or random coils
tertiary protein structure
the functional 3D shape of a polypeptide chain
quaternary protein structure
the level of protein structure where multiple polypeptide chains bond together, or other non-protein groups are added to form a fully functional protein
Carboxyl Group (Amino Acid Structure)
the functional group on amino acid molecules that contains a hydroxyl group (OH) and an oxygen doublebonded to a carbon atom