Exam 3 Flashcards
Transcriptional control
Controlling when and how often a given gene is transcribed.(occurs most often H-bonding occurs)
RNA Processing control
Controling how an RNA transcript is spliced or other wise processed( RNA splicing)
mRNA transport and localization control
Selecting which mRNA’s are exported from the nucleus to the cytosol (mRNA export transport and localization control)
mRNA degradation control
Regulating how quickly certain mRNA molecules are degraded (mRNA half-life).
Translation control
Selecting which mRNA’s are translated into protein by ribosomes(selection and speed of translation)
Protein degradation control
Regulating how rapidly specific protiens are destroyed after they have been made;
Protein activity control
Protien activity control/ regulation
Promoter
region of a gene binds the enzyme RNA polymerase and correctly orients the enzyme to begin its task of making an RNA copy of the gene.
motifs
t
What is the DNA recognition sequence for the first general transcription factor that binds to the promoter.
TATA Box
o Complex with many binding motifso
o RNA polymerase requires general transcription factors
o Regulatory proteins control expression from a distance
o Promoter DNA location on nucleosome can affect initiation of transcription
Eukaryotic gene regulation
How do transcription regulators, general transcription factors, and RNa polymerase gain access to such DNA?
o Nucleosomes can inhibit initiation of transcription if they are positioned over a promoter, b.c they physically block the assembly of the general transcription factors or RNA polymerase on the promoter.
o Such chromatin packaging may have evolved in part to prevent leaky gene expression by blocking the initiation of transcription in the absence of the proper activator proteins.
List the types of Transcription regulations
- Combinations of transcription regulators for one gene
- A single protein coordinates different genes
- Combinations of transcriptional regulator for different cell types
- Reprogramming of differentiated cells
• Master transcription regulator activates transcription of its own gene in addition to that of other cell-type-specific genes
Positive feedback loop
miRNA
Small noncoding RNA that controls gene expression by base-pairing with a specific mRNA to regulate its stability and its translation.
MicroRNA’s control gene expression by
base pairing with specific mRNA’s and inhibiting their stability and translation.
RNA interference
Cellular mechanism activated by double-stranded RNA molecules that results in the destruction of RNAs containing a similar nucleotide sequence. It is widely exploited as an experimental tool for preventing the expression of selected genes (gene silencing).
Step to miRNA destruction of mRNA
Precursor miRNa transcript is processed to form a double stranded intermediate & exported to cytoplasm.
Further processed to form a mature, single stranded miRNA.
Form RISC complex
search for complementary mRNA.
Rapidly degrades the mRNA or transferred to cytoplasm for degradation.
Plasma membrane
a protein studded fatty film so thin that it cannot be seen directly in the light microscope. Every cell on earth uses such a membrane to separate and protect its chemical components from the outside environment
most common phospholipid
Phosphatidycholine
Cholesterol stiffens bilayer by
making it less flexible and less permeable
In eukaryotic cells new phospholipids are manufactured by
enzymes bound to the cytosolic surface of the endoplasmic reticulum.
Flippases
The golgi apparatus contains enzymes that remove specific phopholipids from the side of the bilayer facing the exterior space and flip them into monoloayer that faces the cytosol.
• The action of flippases and similar enzymes in the plasma membrane initiates and maintains the _______________ of the phospholipids that is characteristic of the membranes of animal cells.
asymmetric arrangement
______ is an enzyme that randomly transfers phospholipid molecules from one monolayer to the other allowing the membrane to grow as a bilayer.
Scramblase
are involved in transport of nutrients, metabolites, and ions across the lipid bilayer.
Membrane Protiens
________ usually crosses the lipid bilayer as an alpha helix.
A transmembrane polypeptide chain
The main component of the cell cortex is the
dimeric protein spectrin, a long, thin, flexible rod. It forms a meshwork that provides support for the plasma membrane and maintains the cells biconcave shape
Define Membrane Potential
Voltage difference across a membrane due to a slight excess of positive ions on one side and of negative ions on the other.
Ion channels
proteins that allow only certain kinds of ions to cross the membrane in the direction of their concentration gradient.
Active transporters
actively move ions into or out of cells against their concentration gradient
State the mechanism of action potential propagation
A depolarizing stimulus locally depolarized the axon.
Voltage sensitive Na+ channels are opened
Inward movement of Na+ action potential generated at that site.
local current passively flows down the axon & depolarizes the adjacent region of the axon.
