Chapter 15 Flashcards
Name the organelle: Metabolic pathways, protein synthesis
cytosol
Name the organelle: contains nuclear genome, DNA and RNA synthesis
nucleus
Name the organelle: ATP Synthesis by oxidative phosphorylation, own DNA and ribosome
mitochondria
Name the organelle: ATP Synthesis and carbon fixation by photosynthesis, own DNA and ribosome
chloroplasts
Name the organelle: membrane synthesis, protein distribution
ER
The ER that has ribosomes attached is
rough
The ER that has the steroid hormone synthesis, Ca2+ sequestration
Think of Milk when you see calcium. And milk is rich and smooth.
Smooth ER
Name the organelle: proteins and lipid modification and sorting
Golgi apparatus
Name the organelle: intracellular degradation
lysosomes
Name the organelle: sorting of endocytosed material
endosomes
Name the organelle: oxidation of toxic molecules
peroxisomes
Which organelles form part of the endomembrane system?
ER, Golgi apparatus, lysosomes, endosomes, peroxisomes
The _____ system is a set of organelles that extensively communicate via vesicle budding
endomembrane
Mitochondria or chloroplast form part of the endomembrane system because they are thought to have come from the engulfment of an ancient prokaryotic cell. True or false?
False. Both do not form part of the endomembrane system.
Name the organelle: ATP synthesis of oxidative phosphorylation.
mitochondria
Name the organelle: Intracellular degradation
lysosomes
Name the organelle: ATP synthesis and carbon fixation by photosynthesis
chloroplasts
Name the organelle: oxidative breakdown of toxic molecules
peroxisomes
Name the organelle: modification, sorting, packaging of proteins and lipids for either secretion or delivery to another organelles
Golgi apparatus
Name the organelle: synthesis of most lipids; synthesis of proteins for distribution to many organelles and to the plasma membrane
ER
Name the organelle: contains the main genome; DNA and RNA Synthesis
nucleus
Name the organelle: contains many metabolic pathways, protein synthesis; the cystoskeleton
cytosol
The volume of the cytosol in typical eukaryotic cell is about ___.
50%
____, ____, and ____ are each surrounded by a double membrane.
Nucleus, mitochondria and chloroplast
Organelles like the Golgi apparatus, lysosomes, and the ER have a ____ membrane.
single
The synthesis of virtually all proteins in the cell begins on ribosomes in the ______. The exceptions are the few ____ and _____ proteins that are synthesized on ribosomes inside these organelles.
cytosol; mitochondria; chloroplasts
What are the three mechanisms of protein transport into organelles?
1- Transport through nuclear pore; 2- Transport across membrane; 3- Transport by vesicles.
____ proteins enter through nuclear pores.
folded
___ proteins enter organelles via protein translocators.
unfolded
Unfolded proteins enter organelles via protein ____.
translocators.
____ proteins move via transport vesicles that fuse with destination membranes.
Folded
____ direct proteins to the correct organelle.
signal sequences
Signal sequences have a continuous stretch of ___ amino acids.
3-60
What happens if the cystolic protein has no signal sequence?
It stays in the cytosol
What is the signal sequence for the retention in lumen of ER?
Think… Before I go to the ER, I need:
Listerine, Aspirin, Glue… Then LEave and stay COOl.
Lys-Asp-Glu-Leu-COO-
What is the signal sequence for Import into nucleus?
Pro-Pro-Lys-Lys-Lys-Arg-Lys-Val
Which amino acids are positively charged for the following signal sequences: Lys-Asp-Glu-Leu-COO-
Lys
Which amino acids are negatively charged for the following signal sequences: Lys-Asp-Glu-Leu-COO-
Think… In the ER, taking aspirin and glue will result in negative consequences.
Asp-Glu
Which amino acids are positively charged for the following signal sequences: Pro-Pro-Lys-Lys-Lys-Arg-Lys-Val
Think…. Lysterine and Argentina have a positive meaning for me.
Lys-Lys-Lys-Arg-Lys
Which amino acids are negatively charged for the following signal sequences: Pro-Pro-Lys-Lys-Lys-Arg-Lys-Va
none
What would happen if you add a signal sequence (for the ER) to the N-terminal end of a normally cystolic protein? (Assume in each case that the protein involved is a **soluble** protein, not a membrane protein.)
The protein will now be transported into the ER lumen.
What would happen if you change the hydrophobic amino acids in an ER signal sequence into charged amino acids? (Assume in each case that the protein involved is a **soluble** protein, not a membrane protein.)
The altered signal sequence will not be recognized and the protein will remain in the cytosol.
What would happen if you change the hydrophobic amino acids in an ER signal sequence into other hydrophobic amino acids? (Assume in each case that the protein involved is a **soluble** protein, not a membrane protein.)(
The protein will still be delivered into the ER.
The __ nuclear membrane is continuous with the __ membrane.
outer; ER
In the nucleus, the mesh-work of protein filaments provides ____ support. What type of protein filaments are these called?
structural; nuclear lamina
In the structure of the nucleus…. the _____ form the gates through which molecules enter or leave the nucleus.
nuclear pores
The inner and outer nuclear membranes form the _____ of the nucleus.
nuclear envelope
What is the term the describes a large, elaborate structure composed of a complex of about 30 amino acids.
nuclear pore
What prevents the passage of large molecules but allowing small, water-soluble molecules to pass freely and non-selectively between the nucleus and the cytosol?
nuclear pore complex
Folded proteins with nuclear localization signals are bound by ____.
nuclear import receptors
Nuclear import receptors and cargo cross the nuclear envelope via the ____.
nuclear pore
___ binds to the nuclear import receptor in the nucleus and returns it to the cytoplasm.
Ran-GTP
_____ hydrolysis drives nuclear transport.
GTP
Dr. Kim has discovered a drug that blocks the ability of Ran to exchange GDP to GTP. What is the most likely effect of this drug on nuclear transport?
Nuclear transport receptors would be unable to release their cargo in the nucleus.
Unfolded proteins enter mitochondria (chloroplasts) via _____.
protein translocators
In the mitochondria, the unfolded proteins diffuse laterally in the ___ membrane until it encounters a second ____ in the inner membrane.
outer; translocator
A mitochondrion has an ___ and ____ membrane, and each membrane has its own protein ____.
outer; inner; translocator
What is the most extensive membrane network in eukaryotic cells?
ER
When translating proteins with ER signal sequences, _____ are targeted to the ER.
ribosomes
All ribosomal subunits return to the common pool in the _____.
cytosol
ER protein targeting depends on the interaction between the ______ and the _____.
signal recognition particle; SRP receptor
ER proteins are threaded through a _________.
protein translocator
SRP and SRP receptor bind and hydrolize ___.
GTP
In the ER, the SRP is displaced and released for ___.
reuse
After signal sequence cleavage, soluble proteins are released into the ___.
ER lumen
After signal sequence cleavage, soluble proteins are released into the ER lumen. The signal peptide is now _____ and then the cleaved signal is going to be ___ later.
cleaved; ejected
Using genetic engineering techniques, you have created a set of proteins that contain two (and only two) conflicting signal sequences that specifiy different compartments. Predict which signal would win out for the following combinations.
The protein would enter the ER. ER sorting signal would supersede a nuclear localization signal.
The arrangement of ER membrane proteins is determined by hydrophobic _______ and ______ sequences.
start transfer; stop transfer
What is 1?
hydrophobic start-transfer sequence
What is 2?
cytosol
What is 3?
ER Lumen
What is 4?
COOH
Which is the mature single-pass transmembrane protein in ER membrane?
5
Which # represents the hydrophobic stop-transfer sequence?
6
Transport vesicles carry soluble proteins and membrane between _____.
compartments
During _____, this vesicle here fuse with a plasma membrane and release its content, the outside
exocytosis
In ______, extracellular material is captured by vesicle and then inward from the plasma membrane and is carried into the cell.
endocytosis
Transport by ___ moves proteins and lipids between membrane compartments.
vesicles
What type of pathway is the ER to the GA to the plasma membrane, and ER to the GA to endosome to the lysosome.
Secretory
What type of pathway is the plasma membrane to the lysosome?
endocytic
To function optimally, each transport vesicle that buds off from a compartment must take with it only the proteins ________ to its destination and must fuse ____ with the appropriate target membrane.
appropriate; only
_____ is driven by the assembly of a protein coat.
Vesicle budding
___ vesicles bud from membrane surfaces.
coated
What is the origin and destination of the following coat proteins: clathrin + adaptin 1
Golgi apparatus; lysosomes (via endosomes)
What is the origin and destination of the following coat protein: clathrin + adaptin 2
plasma membrane; endosomes
What is the origin and destination of the following coat protein: COP proteins
ER, Golgi cisterna, Golgi apparatus;
Golgi apparatus, Golgi cisterna, ER
Vesicles that bud from membranes usually have a distinctive protein coat on their cytosolic surface and are therefore called coated vesicles. What are the functions of the coat?
1- It helps shape the membrane into a bud;
2- It captures molecules for onward transport
_____ receptors recognize transport signals on cargo molecules and bind.
cargo
____ mediate the connection between coat proteins and cargo receptors
Adaptins
_____ (binds GTP) pinches off the vesicle.
dynamin
____ and ____ are involved in the initial shaping of the vesicle into the pit.
clathrin; adaptin
How does a transport vesicle select its particular cargo?
Second class of coat proteins called adaptins does the job.
What are the 2 functions of the adaptins?
1- Secure the clathrin coat to the vesicle membrane;
2- Help select the cargo molecules for transport
Dr. Kim has just joined a lab that studies vesicle budding from the Golgi and has been given a cell line that does not form mature vesicles. She wants to start designing some experiments but wasn’t listening carefully when she was told about the molecular defect of this cell line. She’s too embarrassed to ask and come to you for help. She does recall that ***this cell line forms coated pits but vesicle budding and the removal of coat proteins don’t happen***. Which of the following proteins might be lacking in this cell line?
dynamin
After a transport vesicle buds from a membrane, coated vesicle rapidly lose its protein coat and then it must find its way to its correct destination to deliver its content. How?
Docking and fusion and mediated by proteins on the surface of the vesicle and target membrane, including Rab and SNARE proteins.
___ proteins on the surface of each type of vesicles are recognized by corresponding tethering proteins on the cytosolic surface of the target membrane.
Rab
Once the tethering protein has captured a vesicle by grabbing hold of its Rab protein, _____ on the vesicle interact with complementary _____ on the target (t-SNARE) membrane.
SNAREs; SNAREs
The same SNAREs play a central role in catalyzing the membrane ___.
fusion
____ the soluble contents.
What are the protein-protein interactions that mediate fusion of transport vesicles?
Tethering
Docking
Fusion
___ proteins are involved in the recognition of the transport vesicle with its target membrane.
Rab
___ are transferred to asparagines by oligosaccharide protein transferase.
Pre-formed oligosaccharides
The unfolded ER protein pass through the translocator right so now you need to modify in the ___.
ER lumen
Proteins are modified by ___ in the ___.
enzymes; ER
What is the purpose of disulfide bond formation?
Helps stabilize the protein structure
Addition of oligosaccharide side chains is termed ____.
glycosylation
What is the purpose of glycosylation?
1- Protein protection from degradation
2- Keeps the protein in the ER until it is properly folded;
3- Acts as a transport signal for packaging the protein into appropriate transport vesicle;
4- Cell-cell recognition
Name the two types of protein modification that can occur in the ER but not in the cytosol.
1- Disulfide bond are formed by the oxidation of pairs of cysteine side chains (This does not occur in the cytosol because of its reducing environment.)
2- Proteins in the ER can undergo glycosylation. (Glycoysylating enzymes are not found in the cytosol. An oligosaccharyl transferase is a membrane-bound enzyme that has its active site exposed on the lumenal side of the ER membrane.)
Exit from the ER is ___.
selective
What are the reasons proteins remain in the ER?
1- Have an ER retention signal (4 aa);
2- Are incorrectly folded (retained by chaperones);
3- Are incorrectly assembled multimeric proteins (retained by chaperones)
____ prevent misfolded or partially assembled proteins from leaving the ER.
chaperones
Accumulation of misfolded proteins in the ER lumen triggers an ______.
unfolded protein response (UPR)
Proteins are further modified and sorted in the ____.
Golgi apparatus
___ golgi network faces the ER, It buds vesicles that return to the ER or continue through the Golgi apparatus.
cis
___ golgi network faces the plasma membrane. It buds vesicle destined for the plasma membrane or other compartments.
trans
The fusion of a vesicle (transport or secretory) with the plasma membrane is ___.
exocytosis
Secretory proteins are released from the cell by _____.
exocytosis
What are the two distinct types of exocytosis that proteins (and lipids) move to the plasma membrane?
unregulated exocytosis;
regulated exocytosis
Which exocytosis default by pathway and transport vesicles are continuously fusing?
unregulated
Which exocytosis occurs only in some cells and the secretory vesicles do not fuse until a signal is received?
regulated
___ vesicles do not fuse until a signal is received.
secretory
Both the unregulated and regulated exocytosis diverge in the ____. Also, specify if it cis or trans.
trans Golgi network
Secretory vesicles ______ and _____ concentrated proteins.
store; release
What are the 3 types of sorting compartments for the endosomes?
Recycling; Degradation; Transcytosis
In endosomes, ____ is the terms that occurs when receptors return to the plasma membrane.
recycling
In endosomes, ____ is when the receptors/cargo and contents of the lumen move to _____.
degradation; lysosomes
In endosomes, _____ occurs when receptors (& cargo?) move to a new plasma membrane area.
transcytosis
_____ digest extracellular materials and old organelles.
lysosomes
____ is the uptake of material into cell by membrane invagination and internalization of the resulting vesicle.
endocytosis
______ is the uptake of particles into large vesicles called _____.
phagocytosis; phagosomes
Phagocytosis occurs in ____ cells. Phagosomes fuse with ____.
phagocytic; lysosomes
_____involves the intake of molecules and fluid and is active in all cells.
Pinocytosis
Pinocytosis are indiscriminate, occurs via _____ coated pits and vesicles, and vesicles fuse with _____.
clathrin; endosomes
_________ is the selective endocytosis of specific macromolecules.
Receptor-mediated endocytosis
Receptor-mediated endocytosis occurs in ______.
low density lipoproteins
Pathway to lysosomes…. _____ is the enclosure of an old organelle in a double membrane creating autophagosome.
autophagy
Lysosomal enzymes are all ___ hydrolases, which have optimal activity at a low pH of about __.
Acidic; 5
Fully folded proteins can be transported into which of the following organelles?
nucleus
Which of the following organelles is the site of steroid hormone synthesis in endocrine cells?
Smooth ER
Nuclear pores restrict larger molecules from traversing the membrane due to their
interwoven meshwork of protein fibrils.
Which of the following accurately describes a step in GTP-driven nuclear transport?
Binding of Ran-GTP to the receptor releases the cargo protein.
In which process do Rab proteins function?
vesicle tethering
What is one of the main differences in the behavior of the proteins in a vesicle destined for constitutive secretion, and the proteins in the vesicle destined for regulated secretion?
Proteins in the regulated secretion vesicle tend to aggregate and become highly concentrated in the ionic conditions in the vesicle.
Which of the endocytic pathways involves the ingestion of large particles or microorganisms and is performed mainly by specialized cells?
phagocytosis
