the structure and function of these form what: endoplasmic reticulum, golgi complex, endosomes, lysosomes, and vacuoles.
what two key organelles are not part of the interconnected system known as the endomembrane system?
mitochondrial and chloroplast
what are the two main pathways through the cytoplasm?
biosynthetic pathways and secretory pathway.
true or false. the pathways (biosynthetic and/or secretory pathways secrete proteins in the ER which in turn are transported to the rest of the cell via the golgi complex.
the secretory pathway is one of the two secretions through the cytoplasm. Secretory activities of cell scan be divided into two types. What are they?
Constitutive and Regulated secretions
which of the two secretory pathways is being described. Materials are transported in secretory vesicles from their sites of synthesis and discharged into the extracellular space in a continual manner.
constitutive secretion of secretory pathway.
this type of secretory pathway contributes not only to the formation of the extracellular matrix but to the formation of the plasma membrane itself.
what are the two types of secretory pathways?
constitutive and regulated secretion
what type of secretion is being described: materials being stored and only released with direct stimuli.
regulatory secretion of secretory pathway
this type of secretion occurs in endocrine cells that release hormones, in pancreatic acinar cells that release digestive enzymes, and in nerve cells that release neurotransmitters.
materials to be secreted (discharged from the cell) and stored in large, densely packed, membrane-bound what?
In which direction do materials move in a secretory pathway?
materials move out of the cell by the secretory pathway.
what is the difference between secretory pathway and endocytic pathway?
secretory pathway material moves out of the cell. Endocytic pathway material moves into the cell from the outer surface of the cell to compartments, such as endosomes and lysosomes, located within the cytoplasm.
compare and contrast the biosynthetic pathway with the endocytic pathway?
biosynthetic pathway also known as secretory pathway. Has two secretions: constitutive secretion and regulatory secretion. Constitutive secretion materials are transported out of the cell into the extracellular space, constructing the extracellular matrix and the plasma membrane itself. The regulatory secretion is regulated by stimulus. In regulatory secretion some materials ready to be secreted (discharged) are stored in large secretory granules which are membrane bound. Endocytic pathway materials travel from the extracellular space into the cell.
how are particular proteins targeted to particular sub-cellular compartments?
by virtue of specific "addresses" or sorting signals that are encoded in the amino acid sequence of hte proteins or in the attached oligosaccharides.
Cargo is directed to tis proper destination by specific targeting signals that are part of the what?
that are part of the proteins themselves.
Start 8.3 The Endoplasmic Reticulum
Start 8.3 The Endoplasmic Reticulum
what are the two sub-compartments of the ER?
Rough ER and Smooth ER
Which sub-compartment of the ER comprise a system of membranes that enclose a space, or lumen, that is separated from the surrounding cytosol?
both the Smooth ER and Rough ER.
The composition of the luminal (or cisternal) space inside the ER membranes is quite different from that of the surrounding ?
Fluorescently labeled proteins and lipids are capable of diffusing from one type of ER into the other, indicating that their membranes have this characteristic?
that the membranes of Rough ER and Smooth ER are continuous.
true or false. although the membranes of RER and SER are continuous, numerous proteins are found only in one or the other type of ER.
The RER is typically composed of a network of flattened sacs called?
what compartment of the Endoplasmic reticulum includes teh synthesis of steroid hormones, detoxification of a wide variety of organic compounds, and sequestration of calcium ions?
What compartment of the ER includes the synthesis of secreted proteins, lysosomal proteins, and integral membrane proteins?
Proteins to be synthesized on membrane-bound ribosomes of the RER are recognized by a ?
recognized by a hydrophobic signal sequence.
The hydrophobic signal sequence which is recognized on the RER to synthesize proteins is usually situated near the ?
N-terminus of the nascent polypeptide
what binds the signal sequence and arrest further synthesis and mediates binding of the complex to the RER membrane?
signal recognition particle (SRP)
what does the SRP (signal recognition particle) bind to that stops protein synthesis?
the SRP (signal recognition particle) binds to the signal sequence.
following binding the SRP (signal recognition particle) is released which allows the signal sequence on nascent polypeptide to be released into the ? through a protein lined pore.
what happens to proteins that are not folded correctly?
proteins that are not folded correctly are translocated back into the cytosol and destroyed.
once a newly synthesized protein is synthesized in either the lumen or the membrane of the RER, the protein can be moved from that location to specific destinations along the ? pathway.
biosynthetic pathway (metabolism)
if the lumen of the ER gets "choked" what happens?
UPR is activated which stops further protein synthesis and removes the proteins causing the choke
Most of the lipids of a cells membrane are synthesized where?
Endoplasmic Reticulum (ER) where they are moved to various destinations
where are phospholipids synthesized in the ER?
phospholipids are synthesized in the cytosolic face of the ER.
once the phospholipids are synthesized in the cytosolic face of the membrane where are they inserted to?
Once phospholipids are synthesized in the cytosolic face of the ER, phospholipids are inserted in the outer leaflet of the ER.
is it possible for a phospholipid of one membranes organelle to be transferred to another organelles membrane?
yes it is possible.
it is true that head groups of specific lipids may be modified enzymatically?
the addition of sugars is also known as?
the addition of sugars (glycosylation) to the asparagine residues of proteins begins ? and continues in the ?
the addition of sugars (glycosylation) to the asparagine residues of proteins begins in the RER and continues to the Golgi Complex.
what determines the sequence of the oligosaccharides chains of glycoproteins?
a large family of glycosyltransferases
where are the carbohydrate chains assembled?
in the ER, one sugar at a time and then transfered as a unit.
almost as soon as the carbohydrate unit is transferred; it begins to be modified, beginning with the ?
terminal glucose residues
the Golgi complex functions as a?
aside from being the processing plant the Golgi Complex is also the site of synthesis of the complex polysaccharide that makes up the ?
Golgi complex aside from begin the processing plant also takes on the role of site of synthesis of the polysaccharide that makes up the matrix plant cell wall.
what is being described: a stack of flattened, platelike cisternae with dilated rims and associated vesicles and tubules?
materials enter the Golgi Complex at what ? face and are modified as they enter the ? face.
materials enter in the cis face and and modified as they move to the trans face.
Once materials reach the ? they are ready to be sorted and targeted for delivery to their ultimate cellular or extracellular destination
trans Golgi Network (TGN)
most if not all of vesicles that transport materials in the endomembrane system are encased in what?
most vesicles that transport material are encased in a protein coat.
COPII-coated vesicles carry material from the ? to the ?
COPII carry material from the ER to the Golgi Complex.
COPI-coated vesicles are retrograde to COPII-coated vesicles which means what?
COPI-coated vesicles carry material back from the Golgi Complex to the ER.
what type of coated vesicles carry materials from the trans Golgi Network (TGN) to the endosomes, lysosomes, and plant vacuole.
Clathrin-coated vesicles carry material to the endosomes, lysosomes, and plant vacuole.
True or false. aside from Clathrin-coated vesicles carrying material from the Trans Golgi Network (TGN) to the endosomes, lysosomes, and plant vacuole. The Clathrin-coated vesicles also carry materials from the plasma membrane to endosomes and lysosomes.
each compartment along the biosynthetic or endocytic pathway has a characteristic ?
each biosynthetic or endocytic pathway has a characteristic protein composition.
this is a source of vesicle that contain particular membrane proteins that target the vesicle to a particular destination?
Trans Golgi Network (TGN)
the docking of two membranes is mediated by what?
the docking of two membranes is mediated by tethering proteins.
tethering proteins mediate the docking of two membranes but what regulates this?
since tethering proteins mediate the docking of two membranes, G proteins called Rabs are the ones who regulate this process.
the merger of donor and acceptor membranes is mediated by what ? which interact to form four-stranded bundles.
the v-SNARES AND t-SNARES interact to form four stranded bundles from the donor and acceptor membranes.
Lysosomes are diverse-appearing, ? organelles that contain an array of acid hydrolases capable of digesting virtually every type of biological macromolecule.
lysosomes are membrane bound organelles.
lysosomes degrade materials, such as bacteria and debris, that are brought into the cell by ?
lysosomes also degrade aging cytoplasmic organelles by a process called ?
in vertebrates this organelle plays a key role in immunologic defense?
what organelle is being described: 90% of the volume of many plant cells is occupied by a single membrane-bound, fluid filled central ?
vacuoles are known as?
where are lysosomes absent in?
plants, lysosomes do not exist in plants
since plants do not have lysosomes what plant organelle replace certain properties that lysosomes offer none plant cells?
vacuoles, have some of the same acid hydrolases found in lysosomes.
in plants, vacuoles are sites of intracellular digestion mediated by ?
the enzyme acid hydrolases mediates intracellular digestion in plants.
what facilitates the uptake of fluid and suspended macromolecules?
what also facilitates the internalization of membrane receptors and their bound ligands?
what functions in he recycling of membrane between the cell surface and cytoplasm?
what is being described: the uptake of particulate (small particles) matter
in what type of endocytosis are ligands bound to plasma membrane receptors?
receptor mediated endocytosis is when specific ligands are bound to plasma membrane receptors
the receptors in the plasma membrane collect in pits are coated on their cytoplasmic surface by what?
what type of process can function as a feeding mechanism or as a cellular system of defense.
what type of organelle is very simple having only two subcompartments in which an imported protein can be placed?
what are the two compartments that an imported protein can be stored in a peroxisome?
boundary membrane and internal matrix
what state must imported proteins assume when entering mitochondria or chloroplast? difference with peroxisomal matrix proteins?
unfolded state. peroxisomal matrix proteins can be imported into peroxisomes in their native folded conformation
what are the two signal markers that distinguish what proteins are tagged for peroxisomes?
mPTS (peroxisomal matrix protein) and PTS (peroximal membrane protein)
what constitutes a cell cycle?
the stages through which a cell pass from one cell division to the next constitutes the cell cycle
what are the two major phases that constitute the cell cycle?
M phase and cytokinesis.
what subphase of interphase is being described: theperiod following mitosis and preceding (before) replication?
G1 of interphase
what subphase of interphase is being described: the period during which DNA synthesis (and histone synthesis) occurs?
S phase of interphase
what subphase of interphase is being described: the period following replication and preceding the onset of mitosis,
G2 phase of interphase
what type of terminally differentiated cells have lost the ability to divide?
vertebrate skeletal muscle and nerve cells
entry of a cell into M phase (mitosis) is triggered by the activation of a protein kinase called?
what are the two types of subunits that MPF (protein kinase) consist of?
MPF which triggers the entry of a cell into the M phase consist of two subunits: a catalytic and regulatory
which of the subunits of MPF is being described: transfers phosphate groups to specific serine and threonine residues of specific protein substrates?
catalytic subunit of MPF is being described
which of the subunits of MPF is being described: consist of a member of a family of preteins called cyclins.
regulatory subunit of MPF
what is the catalytic subunit of MPF called?
Cyclin-dependent kinase (Cdk)
when the cyclin concentration reaches a sufficient level, the kinase is activated, which triggers what to occur?
when the cyclin level is met the kinase can then regulate the entry of cell into the M phase.
at what two points primarily are the activities of the cell cycle controlled?
between G1 and S. and also between G2 and entry into mitosis.
why are the points between G1-S and G2 and entry into mitosis control points?
because the transient activation of a Cdk (cyclin-dependent kinase) is required by a specific cyclin.
Arrest of a cell at one of the checkpoints of the cell cycle is accomplished by ? whose synthesis is stimulated by events such as DNA damage.
what organelle is being described: contains the centrioles and is not present in plant cells?
Plants rely on what instead of centrosomes?
mitotic spindle fibers
the end of prophase is marked by the rupture of the ?
the rupture of the nuclear envelop marks the end of prophase.
what are the different phases of mitosis?
prophase, prometaphase, metaphase, anaphase and telophase.
what phase of mitosis is occurring: sister chromatids suddenly split away from one another, a process that is triggered by the ubiquitin-mediated destruction of cohesin, a protein complex that holds the sister together
anaphase. the sister chromatids were attached together at the metaphase stage of mitosis
what phase in mitosis is being described: the reformation of he nuclear envelope, the dispersal of the chromosomes, and the reformation of membranous cytoplasmic networks.
what process is being described: the division of the cytoplasm into two daughter cells.
what is the difference between how cytokinesis occurs in animal cells vs plant cells?
in animal cells cytokinesis occurs by constriction and in plant cells cytokinesis occurs by construction.
what type of cell is cytokinesis taking place: building a cell membrane and cell wall in a plane lying between the poles?
what type of cells do cytokinesis create a furrow (pinch)?
what stage of meiosis has no counterpart in mitosis?
prophase I of meiosis has no counter part in mitosis.
why is prophase I of meiosis so different compared to prophase in mitosis?
prophase I in meiosis is different because this is the time where crossing over occurs, which does not take place during mitosis.
during crossing over what term describes when homologous chromosomes remain attached to one another at specific points called ? which represents sites of recombination
in meiosis what phase is being described: homologous chromosomes separate from one another with the maternal and paternal chromosomes of each tetrad segregating independently.
Start of chap 15
start of chap 15
cells usually communicate with each other through ?
extracellular messenger molecules
what type of signaling is being described: A cell that produces the messenger also expresses receptors, so technically cells that release the message will stimulate (or inhibit) themselves because they have the receptor on their surface.
autocrine signaling. think of autocrine as self regulating extracellular messenger molecules.
what type of signaling is being described: messenger molecules who only travel short distances through the extracellular space to cells that are in close proximity to the cell that is generating the message.
paracrine messenger molecules
what type of extracellular messenger molecule can only travel short distances because they are unstable, can be eaten up by enzymes or they bind to the extracellular matrix?
paracrine messenger molecules
what type of messenger signaling molecule is being described: messenger molecules reach their target cells via passage through the bloodstream.
what extracellular messenger molecule is also known as a hormone?
endocrine signaling molecule who typically act on target cells located at distant sites in the body.
what are the 3 types of extracellular messenger molecules that take place in cell signaling?
autocrine (self regulating), paracrine (travels short distance), endocrine (travels through blood stream long distances..aka hormones).
what term describes the following: Cell signaling typically includes recognition of the stimulus at teh outer surface of the plasma membrane; transfer of the signal across the plasma membrane; and transmission of the signal to the cell interior; triggering a response.
in cell signaling a prominent feature of signaling pathways is the involvement of ? that serve as switches that turn a pathway on or off?
what is the phenomenon in which information is relayed across the plasma membrane to the cell interior and often to the cell nucleus?
through signaling pathways what are the two enzymes that activate or inhibit their substrates through changes in conformation.
protein kinases and protein phosphatases
what is the protein involved in signaling pathways that turns a pathway on or off?
true or false: first messengers create extracellular stimuli, they interact with G protein-coupled receptor (GPRC) which are on the outer cell surface to stimulate a second messenger within the cell
receptors are located where in the cell?
receptors are located in the extracellular surface of the cell.
true or false: messenger molecules (or ligands) bind to the receptors which are in the extracellular surface of the cell.
what type of messenger are small substances that typically activate (or inactivate) specific proteins?
if a second messenger is generated the enzyme responsible for this is called what?
effector because it brings about effects
depending on its structure what interaction does a second messenger have with the plasma membrane?
the second messenger can diffuse or remain embedded in the plasma membrane.