Cell structure and function Flashcards
What is the purpose of the polyadenelation signal?
During termination of transcription the polyadenaletaion signal (AAUAAA) causes the RNA polymerase II to remove itself 10-35 base pairs downstream of the polyadenelation signal.
What are the functions of the protein in the plasma membrane?
TESCAI Transport Enzyme Signal Cell-cell communication Attachment Intercellular
Explain how transcription is initiated in eukaryotic cells
A eukaryotic promoter includes a TATA box (TATAAA)
in which several transcription factors must bind to the DNA before RNA polymerase II can do so.
(the TATAAA box is before the start point)
More transcription factors along with RNA polymerase II bind to the promoter region.
Does transcription include both translated and untranslated sequences?
YES
What is the transcription rate in eukaryotes?
40 nucleotides per second
What are three steps involved in cell signalling?
Reception, transduction and response
What are the four different types of receptors?
G (globular) protein receptors
receptor tyrosine kinases
ligand gated channels
intracellular receptors
Explain how the G protein coupled receptors work, using adenylyl cyclase as an example
A ligand (for example a hormone) induces a protein conformational change of the receptor.
This activates a specific cytoplasmic G protein to exchange its low energy GDP for a high energy GTP.
Activated G protein activates an effector enzyme such as adenylyl cyclase (in the cholera effected signalling pathway)
This produces the second messenger cAMP
The cAMP activates protein kinases which causes a cascade of phosphorylation reactions.
G protein then inactivates itself by HYDROLYSING its GTP into GDP
Explain how the Receptor Tyrosine Kinases work:
RTK are membrane bound proteins, where its cytoplasmic region is made of three TYROSINE amino acids
Binding of the signalling molecule causes the RTK to dimerise and form a DIMER.
cross phosphorylation of the tyrosine amino acids occurs.
Relay proteins then recognise these phosphorylates tyrosine proteins and these relay proteins then become activated themselves.
This causes a cascade of phosphorylation reactions downstream using usually protein kinases.
Explain how ligand gated channels work, using the post synaptic membrane as an example
Specific signal molecules (e.g. neurotransmitters) cause ligand gated ion channels to open in the post synaptic membrane resulting in an influx of sodium ions and localised depolarization. The amino acids lining the pore of the channel are selective and only let in certain molecules of a specific size and charge.
Can hormones pass through the plasma membrane and activate intracellular receptors?
Yes, they are hydrophobic so can pass through membrane and attach to receptor proteins INSIDE the cell.
What are the two types of signal transduction pathways?
cAMP and Ca2+
What is a phosphorylation cascade?
A series of protein kinases add phosphate groups to the next one in line, to effect the final EFFECTOR, which may be an enzyme.
Phosphate is added via ATP turning into ADP and donating an inorganic phosphate to each of the protein kinases.
How are Ca2+ ions removed before signalling in the cell?
Ca2+ pumps are in the plasma membrane (pumping Ca2+ out of the cell) mitocondria (pumping Ca2+ into the mitochondria) Endoplasmic reticulum
What is the signalling pathway used for muscle contraction?
A ligand (for example a hormone) induces a protein conformational change of the receptor.
This activates a specific cytoplasmic G protein to exchange its low energy GDP for a high energy GTP.
Activated G protein activates an effector enzyme such as phospholipase (in the cholera effected signalling pathway)
phospholipase cuts PIP2 into half into IP3 which acts as a ligand (a second messenger)
IP3 gated ligand channel lets in Ca2+ ions from the endoplasmic reticulum
Ca2+ acts as a second messenger to activate other proteins such as myosin
What are examples of cellular response?
PRIM G or GRIMP
Gene expression Protein function Ion channel Metabolism Regulation of cellular organelles or organisation
What form of energy is used during translation?
GTP turning into GDP
What are the post translation modifications that can occur in the golgi apparatus?
BAMPCCC
Biotinylation Acetylation Methylation Phosphorlyation Carboxylation Carbohydrate addition Cleavage
When blood sugar levels are low, the hormone
glucagon is released, to increase blood sugar levels.
Released from alpha cells in islets of langarhan in pancreas
When blood sugar levels are high, the hormone
insulin is released, to decrease blood sugar levels.
Released from beta cells in islets of langarhan in pancreas
What are the four major cycles in cellular respiration?
Glycolysis
Formation of Acetyl co enzyme A
Krebs cycle
Electron transport chain
What is produced in glycolysis?
Reactants:
oxidizing Glucose
Products:
2ATP
2NADH + 2H+
2 pyruvate molecules
anaerboic cytoplasm
What is produced in the formation of acetyl co enzyme A?
Reactants:
2 pyruvate molecules
Products:
2 CO2
2 NADH + 2H+
2 acetyl co enzyme A
aerobic
mitochondrial matrix
What is produced in the Krebs cycle?
Reactants:
2 acetyl co enzyme A
Products: 2 ATP 4 CO2 6 NADH + 6H+ 2 FADH2
mitochondrial matrix
Explain the electron transport chain and chemiosmosis:
NADH and FADH2 donate electrons to a series of electron carriers in the inner membrane of the mitochondria.
As electrons pass from each protein carrier to carrier, it transfers energy for hydrogen ions (protons) to be pumped into the inter membrane space,
electrons are then transferred to oxygen, reducing it to become water.
Chemiosmosis:
Proton gradient is established in the inter membrane space.
Protons passively move through ATP synthase and H+ movement powers rotation through a turbine like thing to mass produce ATP from ADP + Pi
26 or 28 ATP is produced
What is the enzyme involved in converting glucose to pyruvate in glycolysis?
Phosphofructokinase
