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)
t or f, the addition of any solute to a solvent will result in the colligative processes vapour pressure depression, boiling point elevation, and freezing-point depression.
true
what is osmosis and osmotic pressure? What is hydrostatic pressure?
osmosis is the diffusion of water. Osmotic pressure is the pressure required to stop osmosis from occurring.
hydrostatic pressure is the pressure exerted by a fluid at equilibrium
why is simple diffusions curve (force of diffusion vs. flux) linear and facilitated curved and levels off?
note: flux = rate of diffusion
facilitated diffusion is subject to saturation kinetics (all carrier / channels are taken up)
microtubules, intermediate filaments, and microfilaments. Explain each.
microtubules are made of tubulin and are used in mitosis to move chromosomes. They are hollow and the largest filament in the cytoskeleton. Microtubules also act as railroad for transport such as nerve axon transport.
intermediate filaments - middle size
microfilaments - smallest, made of actin, involved with amoeboid movement
t or f, both eukaryotic and prokaryotic flagella have a basal structure, hook, and filament organization.
false, only prokaryotes have this set up. Eukaryotes have an microtubule arrangement that differs.
dynein is a motor protein found where?
in the microtubule tracks which facilitate transport of intracellular material
Mitosis: What is the difference between sister chromatids and homologous chromosomes?
sister chromatids –> are identical copies of a chromosome that result after DNA replication
Homologous chromosomes –> are non-identical copies of the same chromosome
e.g. You have two copies of chromosome 1 (one from mom, one from dad). These are homologous chromosomes. Then after DNA replication you have two copies of paternal chromosome 1 and 2 copies of maternal chromosome 1.
each pair are sister chromatids to each other
Explain the cell cycle.
The Cycle begins with mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis. This is the actual division of one cell into two
then G1 phase occurs: growth and development
then S phase occurs: DNA replication
then G2 occurs: more growth
then mitosis again
what occurs during Prophase of mitosis? (3)
- chromosomes condense tightly and sister chromatids are joined by centromeres.
- nucleolus disappears
- Centrioles move to opposite sides of the cell
- nuclear envelope begins to degrade
what are centrioles and the microtubule organization centre (MCOT)
MCOT is in every cell and it coordinates microtubule cytoskeleton development. Centrioles are apart of it and they form the spindle fibres in mitosis.
what is the difference between the kintechore and the centromere?
The centromere links sister chromatids together
The Kinetochore links each sister chromatid to a spindle fibre
What occurs during metaphase of mitosis?
The chromosomes line up along the metaphase plate. This is achieved because the kinetochores of each chromosome is connected to the centriole spindle fibres.
Note: polar centrioles / MCOTs are also referred to as asters since they look like (a) stars
what occurs during anaphase of mitosis?
the spindle fibres shorten towards the centrioles which separates the sister chromatids. The cell begins to elongate and develop the cleavage furrow.
What occurs during telophase?
essentially the opposite of prophase.
- nuclear envelope forms around polarized chromosomes (ex-sister chromatids)
- nucleolus appears in each
- chromosomes re-condense
cytokinesis occurs in which the cells actually separate.
what are capsase enzymes
Capsase enzymes are the main enzyme involved in apoptosis
what are initiation capsase’s and effector capsase’s?
upon an external (cytokine / toxin / etc.) signal or internal signal (accumulation of a tumour suppressor protein) initiation capsase’s clump together which activates effector capsase’s which cleave many proteins for apoptosis.
what is an alpha-beta tubulin dimer?
this is the monomer unit for the microtubule cytoskeleton of the cell (which is a hollow rod)
t or f, the MTOC is a pair of centrioles which duplicate and then move to each end of the cell upon mitosis.
true
t or f, the kinetochore is a part of the chromosome centromere and is the location where the spindle fibres attach which extend from polarized centrioles.
true
what is a microfilament and what are they made from?
the smallest filament in the cell. they are made from actin and are used in small gross movements.
what are microtubules made out of?
alpha tubulin and beta tubulin dimers. many dimers non-covalently form a hollow tube
t or f, all cytoskeleton structures are made from non-covalent interactions of many proteins
true, cytoskeleton is a great example of quaternary structure.
microtubules elongate from one end, what is the other end?
microtubule organization centre MTOC located near the nucleus.
what is within the MTOC?
a pair of centrioles which control cell division via splitting chromosomes
therefore microtubules are responsible for mitosis / meiosis
what is the miotic spindle
the centrioles + their expanding microtubules
t or f, the centromere of each Xm has a kinetchore which the mitoic spindle attaches too
true
what else do microtubules do other than mitosis?
they mediate transport of substances within the cell (e.g. in axons)
cilia and flagella are also made from microtubules
what do microfilaments do? what are they made from?
they are made out of actin (thin filament)
actin / microfilaments are responsible for gross movement of the cell and contractile processes in muscle cells
they perform cytokinesis too
what are intermediate filaments made from and what do they do?
these are heterogenous being composed of many proteins.
these simply create cell structure and are less dynamic than microfilaments and microtubules (they don’t grow and shrink repeatedly)
what is a desmosome?
do not form seals but merely hold cells together (tight junctions hold cells in a seal)