Module 6: Reg. of Gene Expression (Expression and Operons) Flashcards
Gene Expression
Process by which information from a gene is used in the synthesis of a functional gene product (typically proteins)
Not ALL gene products…
Not ALL gene products are needed ALL the time!
Controlling gene expression is used to control…
what gene products are present within a cell
Gene expression control occurs at what overall levels?
3 levels:
1) Transcriptional Level
2) Translational Level
3) Post-Translational Level
Transcriptional level of regulation is generally determined by…
Whether RNA polymerase binds to a gene promoter or not (initiating transcription)
Translational level of regulation is generally determined by…
Whether mRNA “makes it” to or binds to ribosome to initiate translation
–> Can be impacted by mRNA secondary structure
At the translational level, mRNA secondary structure can impact:
1) Susceptibility of mRNA to enzymatic degradation (by RNAses)
2) Inhibition of ribosomal binding
Post-Translational level of regulation is generally determined by…
Modifications made to a formed protein to either ACTIVATE or DEGRADE it
The __________ regulation occurs the …..
The sooner regulation occurs the less energy and resources are wasted
Controlling gene expression is what kind of a process?
CONSERVATIVE PROCESS
–> Conserves energy and resources
–> Why make a protein just to degrade/deactivate it when you can prevent its formation in the first place?
What are the two classifications of gene expression?
1) Constitutive expression
2) Inducible expression
Constitutive Expression
The constant expression of genes that encode for products ALWAYS needed by a cell for essential processes
–> Genes are constantly “on”; constant gene product generation
What specific pathways involve constitutively expressed genes (3)?
Genes involved in:
1) Glycolysis
2) Transcription
3) Translation
Inducible Expression
The SELECTIVE expression of genes that encode for products needed ONLY under certain conditions’
–> Genes are “off” and must be “turned on”; their expression is induced
Gene products of inducibly expressed genes are…
ONLY needed according to the presence of a specific substrate
Classifications of enzymatic control/regulation within cells (2):
2 Classifications:
1) Control of enzymatic ACTIVITY
2) Control of enzymatic PRODUCTION
How can activity of enzymes be regulated?
By altering ENZYMATIC STRUCTURE to alter the binding properties of an enzyme
Can occur in one of 2 ways:
1) Binding of inhibitors
2) Covalent modification
What are the two methods of regulating enzyme activity?
1) Binding of inhibitors
2) Covalent modification
What are the types of regulation of enzymatic activity by inhibitor binding?
1) Competitive Inhibition
2) Allosteric Inhibition
Competitive Inhibition
When an inhibitor molecule binds to the ACTIVE SITE of an enzyme, blocking the substrate from binding
(Inhibitor and substrate “compete” for the active site)
Why is competitive inhibition competitive?
Because the inhibitor and substrate “compete” for binding of the active site!
Allosteric Inhibition
An inhibitor molecule that binds to a site on an enzyme OTHER than the active site (allosteric site)
Binding of an inhibitor to an allosteric site causes…
conformational change to the enzyme so that the substrate can no longer bind to the active site!
Allosteric inhibitors are typically…
The PRODUCT of a multistep pathway that the enzyme is involved in