Eukaryotic cell Flashcards
What occurs in the nucleolus?
partial ribosome synthesis in which RNA pol 1 synthesizes rRNA. Note, the nucleolus is not separated from the nucleus, it is just in a polarized region of it.
what is a nuclear localization sequence?
proteins destined to be used in the nucleus will contain an AA sequence that signals for them to be transported back to the nucleus after cytoplasmic translation
What are the functions of the RER and SER?
RER –> it is studded with ribosomes. It is mainly responsible for synthesizing and processing proteins which are apart of the secretory pathway.
SER –> steroid synthesis and detoxification in the liver and calcium storage in muscle.
proteins that are translated in the cytoplasmic ribosomes are likely to appear where?
they may appear in the
- nucleus
- cytoplasm
- mitochondria
- peroxisome
Proteins synthesized by the RER are likely to end up where?
in any part of the secretory pathway. Therefore they can end up in 1. the RER 2. the Golgi apparatus 3. the plasma membrane 4. ECF 5. inside of lysosome which have degrading functions
how do secretory proteins go from the RER to the Golgi to etc.
They travel through vesicles (never touching the cytoplasm). This vesicle transport makes the secretory pathway “contiguous” (means to share a common border)
Explain what an N-terminal signal sequence is and a signal recognition particle (SRP) is.
An N-terminal signal sequence is the sequence of amino acids on the mRNA. This signal sequence is recognized by the SRP. The SRP binds the RER ribosome Orients the translating peptide so that as its being made it enters the RER lumen.
What is a signal peptide?
the signal peptide is the amino acid sequence that came from the signal sequence translation. The peptide sequence enters the RER lumen first and is cleaved by a signal peptidase inside the lumen. (its only job was to get the protein into the secretory pathway)
true or false, the signal sequence / SRP / signal peptide mechanism is only used for proteins destined for the ECF or a lysosome.
true, proteins destined for the plasma membrane and such have another mechanism
however, all secretory pathway proteins contain a signal sequence + some other signal
PM - transmembrane domain
Golgi - targeting sequence
integral membrane proteins contain regions called transmembrane domains. Explain these and the secretory pathway involved for them
The transmembrane domains are series of hydrophobic amino acids which end up within the membrane. they are derived from interior signal sequences of the mRNA. During translation, these domains are threaded through the ER membrane which then buds off to the Golgi inside a vesicle.
what is the difference between a targeting sequence and a localization signal?
A targeting sequence is a sequence on a peptide that is in the secretory pathway but not destined to be secreted or in the plasma membrane.
A localization signal is sequence on a peptide that is made in the cytoplasm and is destined to go to an organelle that is not apart of the secretory pathway.
for the following peptides, state the signal sequence, if any, that they have for transport.
- secreted peptide
- PM peptide
- lysosome
- RER
- SER
- Golgi
- Cytoplasm
- Nucleus
- mitochondria
- secreted = signal sequence with SRP
- PM = signal sequence + transmembrane domains
- lysosome = signal peptide + targeting signal
- RER = signal P + targeting sequence
- SER = signal P + targeting sequence
- Golgi = signal + targeting sequence
- Cytoplasm = nothing
- nucleus = localization
- mito = localization
true or false, the Golgi is very uni-directional
true, proteins enter the cis side and leave the trans side
Autophagy, phagocytosis, and crinophagy are all done by this organelle… Explain each process.
Autophagy = self eating (eating damaged organelle) Phagocytosis = cell eating ECF content Crinophagy = the digestion of excess material
this is performed by lysosomes which contain acid hydrolase’s
what do peroxisomes do?
a variety of metabolic tasks. They have bi-product that is peroxy acid but this is degraded by catalase (an enzyme)
true or false, weaker intermolecular forces means higher vapour pressure of the substance.
true, vapour pressure is the measured pressure of a gas phase substance back down on a liquid. The easier it evaporates, the more gas form there is, the more vapour pressure.
easier evaporation = weak IMF’s
how does dissolving a solute in a solvent effect the solvents vapour pressure?
the solute dissociates and forms ionic interactions with the solvent making it more difficult for the solvent to enter the gas phase. Therefore adding a solute will decrease vapour pressure.
what is the Van Hoft factor (i)
i represents the amount of particles in solution when something dissolves.
glucose (C6H12O6), i = 1
NaCl, i = 2
what is a colligative process?
a process that depends on the number of solute particles more than the kind of particle. Vapour pressure decrease due to solute addition is a colligative process (the amt of solute added)
