Chapter 11 part 2: Metabolic Control and Gene Regulation Flashcards
(29 cards)
Anabolic metabolism
requires the input of energy to create large molecules from small molecules
Catabolic metabolism
breaking down large molecules into smaller molecules which releases energy
There are two ways in which metabolic pathways itself can be regulated
1) through regulating enzymes
2) Through regulating the genes that code for enzymes
Feedback inhibition
the end product of the metabolic pathways inhibits the enzyme
What are operons?
groupings of functionally related genes that appear primarily in prokaryotes. All of these genes are controlled by a single promoter sequence. Therefore, a single switch controls the transcription of all of the genes present in the operon
Inducible operons
normally turned off meaning they aren’t normally expressed
Repressible operons
are normally turned on and are expressed but can be regulated if needed
What kind of operons do catabolic processes use
They usually use inducible operons because the processes involve only genes that are expressed when the presence of the molecule being broken down is synthesized
What kind of operons do anabolic pathways use?
usually involve repressible operons which are normally expressed but when the molecule is synthesized by the pathway it is turned off
Negative regulation
the binding of the repressor molecule stops transcription
Positive regulation
the binding of the activator molecule starts transcription
The lac operon
is an inducible operon that’s under negative control. It turns on only when lactose or allolactose is present to induce enzyme production. Lac operon activates only when lactose is present, and glucose is low. cAMP and CRP assists in activating the operon in low glucose conditions
What are the three enzymes in the lac operon mechanism
B-galactosidase, B-galactoside permease, B-galactoside transacetylase
The lac operon produces the enzymes needed to break down lactose only when lactose is present and glucose is absent
Strong transcription when lactose is present, and glucose is absent -> the repressor molecule will be inactive, and the CRP molecule will be active. Transcription will occur and the enzymes will be made
The trp operon
is an example of a repressible operon. an operon that is always on and can be turned off by an active repressor molecule. It controls the production of tryptophan which is an essential amino acid. It is constantly on meaning the genes for tryptophan synthesis are being transcribed. It turns off when tryptophan binds to and activates the repressor. It produces the enzymes needed to make tryptophan only when tryptophan is absent
Transcription is tryptophan is absent
the repressor molecule will be inactive, and transcription will occur. Therefore the enzymes will be made
No transcription if tryptophan is present
the repressor molecule will be active and no transcription will occur. therefore no enzymes will be made
Chromatin
the complex of DNA and proteins called histones
What is the 10nm fiber (level 1) of chromatin
Histones bind to the chromosomal DNA in a complex called a nucleosome. Each nucleosome contains eight histone molecules with an amino acid projecting outward
Histones replicate independently of DNA
What is the 30nm fiber (level 2)
the histone tails interact with linker DNA such that the string of nucleosomes coil to form a chromatin fiber that is 30nm in diameter
Euchromatin
True chromatin because it uncoils during interphase making the DNA accessible to the cells transcriptional machinery
Heterochromatin
remains coiled even during interphase leaving DNA inaccessible
