Biology 2.4-2.6
Nuclear and mitochondiral and peroxisomal proteins have
specific signal sequences that direct their import into their correct location post-translation
Based on the results displayed on your graph, which of the following correctly describes the path taken by a secreted protein?
The protein begins its path in the endoplasmic reticulum, passes through the golgi apparatus, and is then delivered to the cell membrane for secretion.
Intermediate filaments
-provide the cell with tensile strength or resistance to force, they are important in maintaining tissue integrity -They also play a role in ordering the cell, forming a basket around the nucleus and helping to anchor organelles in the cytoplasm -length remains consistent
Which of the following processes occur in the nucleus? Select all that apply.
DNA replication. Transcription.
What does the Peroxisomal Targeting Signal consist of?
3 amino acids
Signal sequences tend to be on the C or N terminal end of the polypeptide. Select the least likely reason for this.
A signal sequence on the ends of the polypeptide would allow aggregation of the protein for efficient translocation.
Mitochondria.
ATP production.
Which statement is one of the tenets of cell theory?
All cells come from preexisting cells.
Which cellular structures interact directly with the intermediate filaments? Select all that apply.
Cell membrane, Nucleus
Which statement about microfilaments and microtubules is true?
Both are involved in the movement of cells. Both have a plus and minus end. Both are short-lived, constantly assembling and disassembling. Both are components of the cytoskeleton.
Which statement about microfilaments and microtubules is false?
Both are made of the same type of protein monomers.
Counting the number of mouse cells you have growing in culture
Brighfield light microscopy
Lysosome.
Digestion & recycling.
Insulin is ultimately secreted to the cell exterior. What assists in the trafficking of the insulin to the membrane?
Clathrin coated vesicle
Observing the movement of a flourescently tagged protein within the cell
Confocal light microscopy
Glyoxysome
Converts lipid to carbohydrate for seed germination.
Tubulin (component of the cytoskeleton).
Cytoplasm.
Fibrinogen is an essential protein involved in wound healing. Fibrinogen is modified in the ER and secreted from the hepatocytes to the circulatory system, where is is available should any cellular damage occur. Which of the following correctly identifies the path that Fibrinogen will take as it is synthesized and trafficked through the cell for secretion?
ER→ cis-Golgi → median-Golgi → trans-Golgi→ secretory vesicle → cell membrane
correct imaging technique with the size of the object virus
Electron Microscopy (EM)
Which of the following correctly identifies a key difference between prokaryotic and eukaryotic cells?
Eukaryotes have membrane-bound organelles while prokaryotes do not
Chloroplast
Generates carbohydrate via photosynthesis .
Mitochondria
Generates energy for the cell.
In post-translational translocation, translation occurs in the cytoplasm. The proteins are then transported to their correct organelle based on the presence of an organelle-specific sequence within its polypeptide sequence. Propose the signal required for a protein that functions in the cytoplasm, and in which the cytoplasm is the final destination.
The protein would not require a localization signal.
Nucleus.
Information storage & transmission.
golgi
Insulin is further processed. A signal sequence is removed by proteolysis and 3 disulphide bonds form.
If the ER vesicle was mis-targeted and fused with the cell membrane instead of the golgi, what would the result be?
Insulin would be unable to attain its tertiary structure.
Rolling
Integrins and recycling endosomes
A glycosyltransferase protein that resides in the RER would have which of the following signal sequences? Select all that apply.
KDEL, RER Signal Sequence
correct imaging technique with the size of the object cell
Light Microscopy (LM)
Acid lipase (a lipid hydrolyzing enzyme).
Lysosome.
The cytoskeleton is composed of three major components, each with distinct functions. Which represents the correct order of these components, from smallest to largest size (diameter)?
Microfilaments, intermediate filaments, microtubules
Peroxisome .
Neutralizes by-products from biochemical cellular reactions
Peroxisome.
Neutralizes toxic Hydrogen Peroxide.
RNA polymerase (transcribes DNA to RNA).
Nucleus.
GLUT-1 (glucose transporter).
Plasma membrane.
Rough endoplasmic reticulum.
Protein synthesis & processing.
Ribosomes are composed of
RNA and protein and play a key role in translating mRNA into proteins , the protein portion is translated in the cytoplasm and then shuttled into the nucleus
PDI (protein folding chaperone).
Rough endoplasmic reticulum.
Peroxisomal proteins
Serine-Argine-Leucine tripeptide at the C terminus of the polypeptide which serves as this specific signal sequence
Chromoplast
Stores pigment.
Vacuole
Stores toxins and water.
You are studying a mutation in which your ER resident protein does not have an ER localization signal peptide. What do you hypothesize would be the outcome of this?
The ER resident protein would be translated in the cytoplasm.
The animal cells in the video express a GFP fusion protein. The location of the green fluorescence tells you where the protein is located within the cell. As you can see in the video, the protein localizes to a large round organelle found at the center of the cell. Which organelle do you think this is?
The Nucleus
Eukaryotes most likely evolved organelles via invagination of the cell membrane in addition to endosymbosis. What advantage do organelles provide to the cell?
They increase the efficiency of cellular activities by physically separating them.
The microvilli have a similar structure to the cilia, but cannot move independently to propel the cell forward. What is the main reason for this?
The microfilaments do not have motor proteins present like the microtubules.
How is the Peroxisomal Targeting Sequence used to direct proteins to the Peroxisome?
The sequence is recognized by a helper protein in the cytosol, which brings the protein to the peroxisome.
In Microscopy, resolution refers to which of the following?
The smallest distance by which two objects can be separated and still be distinguished as separate .
dynein
minus end directed
As with all experiments, several important controls were included. Pollard and Weihing included a control that inhibits new protein synthesis (cycloheximide); an inhibitor of new ATP synthesis (dinitrophenol); and an inhibitor of microtubule polymerization (colchicine). What was the purpose of these controls?
To demonstrate that microfilaments and not microtubules are involved in amoeba movement
The golgi apparatus packages and sorts proteins to their final location. Which of the following is not a location the Golgi will send proteins to?
To the mitochondria
Observing the subcellular structure and organization within the cell
Transmission electron microscopy
The mitotic spindle
a dynamic microtubule based structure, with the minus ends of spindle microtubules anchored in each of the two centrosomes at either side of a cell and the plus ends attach to chromosomes via a protein complex called the kinetochore
prokaryotes lack
a membrane bound nucleus and contain very few internal membrane bound compartments
kinesin
plus end directed
microfilaments
a.k.a. as actin filaments and are composed of non-covalently bound actin monomers, smallest cytoskeletal filaments and are generally very dynamic,
Researchers observe that while the actin microfilaments in an amoeba seem to be intact, the organism appears incapable of forming pseudopods for movement. They hypothetize that its immobility may be caused a defect in the ability of
actin monomers to assemble at the plus end of the microfilament.
The nucleus is a membrane-bound organelle found in ______.
all eukaryotic cells.
Eukaryotic cells can be divided into
animal and plants cells which share cell membrane, endomembrane system, and mitochondia,
Microtubules
are assymmetric or polar, with minus ends buried in the MTOC and plus ends near the cell surface. the polar nature of the microtubules allows them to be used as highways for directed transport of materials within the cell
Prokaryotic cells
are bounds by a plasma membrane, nucleoid, and the cytoplasm , ribosomes
kinesis and dynein
are opposing microtubule motor proteins that use the energy of ATP hydrolysis to carry cargo such as vesicle and mitochondria
Dynein (linked) .
associated with the microtubules to flex cilia for cellular movement
Myosin
associates with the microfilaments for cellular contraction.
Dynein (cytoplasmic)
associates with the microtubules to deliver cargo to the negative end.
Kinesin
associates with the microtubules to deliver cargo to the positive end.
integrins
attachement to the ECM
correctly folded proteins
become enclosed in ER-derived vesicles (membrane bound compartments) that bud from the ER and fuse with the membranous golgi apparatus
What are the different type of light microscopy
bright field, phase contrast, and fluorescence
Vesicles
can move materials between the organelles of the endomembrane system
prokaryotes are surrounded by a
cell wall, which is made of peptidoglycans and serves to protect the bacterium and resist cytoplasmic pressure
Eukaryotic cells can be further subdivided to plant and animal cells. Select the organelles and structures which are plant specific and not present in the animal cell
chloroplast, chromoplast, glyoxysome, cell wall
The Golgi consists of flattened membrane enclosed compartments (cisternae) that move and are renamed as they mature. Sort the golgi compartments from the least mature to the most mature.
cis compartment, medial compartment, trans compartment
The golgi apparatus
consists of a series of flattened membranous stacks that are adjacent to but not connected with the RER.
The endomembrane system
consists of a series of interconnected membrane structures, the nuclear envelope, the endoplasmic reticulum, the golgi, lysosomes, and the cell membrane ,
The eukaryotic cell
contains many organelle, these allow maintenance of different environments within the cell adn increase effieciency of cellular processes
Now let us compare all 3 cell types - prokaryotic, eukaryotic animal and eukaryotic plant. What cellular structures do all cell types have in common?
cytoplasm, DNA, cell membrane
cytoplasm
cytosol ( water and dissolved ions, small molecules and proteins)
Proteins that function in the ---- do not have RER signal localization and are -----
cytosol, nucleus, or mitochondria, translated entirely in the cytosol
secreted proteins
destined to be released by the cell, travel in post-golgi vesicles toward the cell membrane, where they are released into the extracellular space upon vesicle fusion with the membrane - this is called exocytosis
What happens in the golgi?
differential changes in glycosylation take place so that by the time the protein has traveled from the cis to the trans golgi it is correctly stamped and addressed to ensure delivery to the correct place m( recycled to the RER, retained in the golgi, sent to the lysosome, or packaged for delivery to the plasma membrane)
the nuclear membrane
double membrane perforated with thousands fo aqueous pores that pass small substances, mRNA and ribosomes must leave the nucleus through these nuclear pores
In tight parallel bundles, actin filaments generate
finger like projections of the plasma membrane that are important in increasing the surface area of the cell for interaction with the exterior environment. Branched networks form large projections of the plasma membrane that are critical for cell crawling and migration
polymerized tubulin dimers
flexing
Ribosomes can be
free (cytosolic) or bound to the endoplasmic reticulum
Anterograde transport
from the ER to the golgi
Retrograde Transport
from the golgi to the ER, returns the ER resident proteins to their correct location
RER-derived vesicles fuse with
golgi membrane and transfer their contents to the golgi lumen
A protein that is destined to be secreted from the cell:
has a signal sequence that targets its translation into the lumen of the RER.
In eukaryotic cells, sugar residues are covalently attached to proteins through the process of glycosylation. This posttranslational modification occurs: (select all that apply)
in the RER and in the Golgi apparatus
Proteins destined for the plasma membrane are inserted
in the RER vesicle membrane so when fusion occurs these proteins are retained in the cell membrane
Lysosomes are not involved
in the secretion of protein
rough endoplasmic reticulum
insulin is translated here.
Cells also move by rolling along the ECM using
integrin proteins, which are recycled in endosomes , these vesicles move the integrin from the back of the cell to the front of the cell, propelling the cell forward
Keratin
intermediate filament found in epithelial cells
You are attempting to diagnose a patient whose symptoms are quite unusual. The patient has extremely delicate skin, even slight pressure results in damage and tearing to the skin. Preliminary test results show no defect in desmosomes or integrins, what do you test for next?
intermediate filaments
Non-coated vesicles
lysosome - retained with the cytoplasm
Post translational translocation
mRNA is translated in the cytosol and the folded protein is moved to the correct organelle via recognition of specific amino acid sequences within the polypeptide. Each organelle has a specific recognition sequence.
Co-translation translocation
mRNA translation begins in the cytosol with the translation of a short ER localization signal sequwnce, this recruits the signal recognition particle to bind to the ribosome, halt translation, and movement of the ribosome to the ER, Upon ER docking, translation resumes with the polypeptide being produced inside the ER lumen
ribosomes
machines that carry out protein synthesis
Prokaryotic flagella
made of the protein flagellin, unlike the cilia the dont bend but a motor protein will drive the rotation of the flagella, some eukaryotic cells have flagella they are more cilia like though
Lysosomes
membbrane enclosed organelles that contain an array of hydrolytic enzymes capable of breaking down all types of biological polymers, proteins, nucleic acids, carbohydrates, and lipids.
organelles
membrane bound structures, the membrane is a phospholipid bilayer that acts as a regulated barrier through which some substances but not others can pass
crawling
microfilament assembly/ disassembly
What are the 3 cytoskeletal filaments
microfilaments, intermediate filaments, and microtubules, which provide a cell with internal structure, organization, tensile strength, and highways for directed transport of materials. The also allow a cell to interact with an move about within its environment
Cilia
more stable microtubule strucutre, they dont grow/ shrink but there is constant subunit exchange with little net effect on length. Cilia move due to the action of their crosslinked dynein motor proteins
the nucleus houses
most of the cell's DNA and is the site of DNA replication and transcription
Myosin
motor protein
Microtubules in resting cell
network radiates from the microtube organizing center which in animal cells is called a centrosome
Based on the results of the experiment above, when the DNA encoding a nuclear signal sequence is removed from a gene encoding a nuclear protein, the resulting protein localizes to ______.
only the cytoplasm.
Based on the results of the experiment above, when the DNA encoding a nuclear signal sequence is added to a gene encoding a cytoplasmic protein, the resulting protein localizes to ______.
only the nucleus.
phase contrast microscopy
or differential interference contrast microscopy, to better see unstained cells which allows visualization of differences in refractive index
Sort the steps of lysosomal digestion from the point where the food particle is taken into the cell
phagocytosis, phagosome fuses with primary lysosome, the food particle is digested in the secondary lysosome, the recyclable material diffuse into the cytoplasm, and exocytosis of undigested materials
Smooth ER synthesizes
phospholipids and cholesterol to provide to other organelles and to the plasma membrane as well as the site of glycogen break down, it is NOT involved in the pathway of protein secretion because it has no ribosomes dock
Whats the difference between plant and animal cells
plant cells have cell wall for strength, chloroplasts for photosynthesis, leucoplast for starch, chromoplasts for pigments and glyoxysomes for see germination
within the RER lumen
proteins are minimally glycosylated and folded,
RER bound ribosomes translate
proteins that are secreted from the cell and proteins that remain within the endomembrane system, including resident ER adn golgi proteins, and lysosomal and plasma membrane proteins
Free ribosomes translate
proteins that reside in the cytosol, nucleus, and mitochondria
After translation into the RER lumen, some proteins are processed by ___, which is cleavage of the protein to make a shortened, finished protein.
proteolysis
polymerized actin
pseudopodia
flagellin
rotation
When comparing your liver cells you notice the hepatocytes secrete a much larger amount of protein than the endothelial cells grown under the same conditions. From this, you hypothesize that these cells must have a large number or amount of
rough endoplasmic reticulum.
nucleoid contains
supercoiled DNA and a few proteins
Rough ER
the ER where ribosomes are bound
Lysosomal digestion refers to
the activity of the hydrolytic enzymes within the secondary lysosome.
cell theory
the cell is the smallest unit of life and cells make up all living organisms, and all cells come from existing cells
Lysosomes function as
the digestive system of the cell serving both to degrade material taken up from outside the cell and to digest obsolete components of the cell itself.
The smaller the cell
the larger its surface to area volume is.
centrosome
the microtubule organizing center in animals, consists of two centrioles which contain tubulin
Transport of Vesicle direction is coordinated by
the motor proteins kinesin and dyenin
An NLS is a short amino acid sequence commonly rich in basic amino acids that is often found near the C-terminus of a protein. Which of the following sequences found at the C-terminus of a protein would most likely result in nuclear localization?
the one with the more basic amino acid
After performing cell fractionation by centrifugation, you discover in fraction number 2 a membrane bound organelle which after further testing stains positive for the presence of hydrogen peroxide. This organelle is most likely
the peroxisome.
The growing end of the actin filament, and the shrinking end
the plus end , the minus end
the microtubules shorten dramatically during
the process of forming the mitotic spindle, by losing tubulin dimers from their plus ends. Th chromosomal movement toward the spindle poles is thought to occur by sliding of the kinetochore down the shortening microtubule
the limit of resolution depends on
the wavelength of light and the light gathering properties of the object
Ribosomes are not true organelles because
they are not membrane bound
the polymerization and depolymerization of microfilaments
they can polymerize and depolymerize quickly in response to the needs of the cell, as actin polymerizes head to tail each end o fthe filament is distinct
Actin filament
thin filament
COP I & II coated vesicles
transport between the golgi and ER
clathrin coated vesicles
transport between the golgi and the cell membrane
fluorescence microscopy
uses filters to direct only specific wavelengths of broad spectrum, high intensity ligh to a specimen labled with a fluorescent dye. the fluorescent dye may be attached to an antibody that binds to a specific portion of a particular macromolecule, usually a protein
Electron Microscopy
uses high speed electrons, focused by electromagnets to image cells and subcellular structures. the pattern of electron scatter/transmission is reflective of molecular structure and can be captured on film or on a fluorescent screen. The practical limit o fresolution of standard electron microscopes is 2-3 nm, allowing one to visualize organelles and some large macromolecules
Bright Field Microscopy
uses white light and and works best with stained cells as tissues and cells typically have little inherent contrast
Movement of vesicles between the ER, golgi, and cell membrane is not unidirectional
vesicles can move from the ER to the golgi or from the golgi to the ER
cell membrane
vesicles fuse here and the mature insulin cleaved and finally activated.
In their simplest form, lysosomes are
visualized as dense spherical vacuoles, but they can display considerable variation in size and shape as a result of differences in the materials that have been taken up for digestions,
Nucleolus
where ribosome proteins are assembled with ribosomal RNA, then the ribosomes leave the nucleus to start their job.
Light microscopy
will allow us to visualize the general size and shape of cells adn some larger organelles with a limit of resolution of about 200nm, meaning that objects separated by a minimum of 200 nm can be viewed as distinct entities.
If actin is arranged in bundles
with the myosin motors protein this can affect contraction, for example the actin/myosin interaction results in muscle contraction in the sliding filament model
