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104 Cards in this Set
- Front
- Back
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What is a polar cell?
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A cell that has two distinct ends.
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Name 6 functions of the cell's plasma membrane.
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1) Maintains structural integrity of cell
2) controls movement of substances in and out 3) regulates cell-cell interactions 4) Serves as a recognition board via receptors 5) establishes transport system for specific molecules 6) transduces extracellular physical and chemical signals into intracellular events. |
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What are 3 types of lipids found in the bi-layer of the plasma membrane?
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Phospholipids
Glycolipids Cholesterol |
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What is the term that describes the hydrophobic and hydrophillic nature of lipids in the bilayer?
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Amphipathic
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What is an integral protein?
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A membrane-bound protein that is embedded in the lipid bi-layer, or completely spans it.
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What type of proteins associated with the plasma membrane are weakly attached via non-covalent interactions?
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Peripheral proteins?
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What molecule is only associated with the extracellular side of the lipid bilayer?
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Glycoproteins and glycolipids. These "glyco" (or carbohydrate) modifications are only found extending into the extracellular space, not the cytosolic space.
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What are two classifications for integral membrane proteins, based on how they weave through the lipid bilayer?
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Single pass - pass through lipid bilayer once
Multipass - weave back and forth through the bilayer. |
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What is the major component of the "modified" fluid mosaic model?
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It accounts for certain proteins needing to stick together for different functions, linked together via a "lipid raft".
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What area of the lipid bilayer is most electron dense, and therefore darker on an electron micrograph?
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The hydrophillic, polar heads.
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What are channel proteins?
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Integral membrane proteins that allow the passage of only one type of ion.
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T/F - channel proteins are ion-specific.
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True.
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What are the 3 different types of channe proteins
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Voltage-gated - open via a change in voltage
Ligand-gated - open via a molecule binding (taste) Mechanically-gated - open via some movement (ear) |
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T/F - channel proteins require binding to transport against concentration gradient.
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False. Ions travel through channel proteins passively, down their concentration gradient.
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T/F - pumps and carrier proteins require binding of molecules to transport those molecules across the membrane.
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True.
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What are some examples of protein pumps in cellular membranes?
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- Na/K pump
- Calcium pump - Glucose transporter |
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What direction does the Na/K pump operate?
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It pumps sodium OUT of the cell, and potassium IN the cell, to re-establish a gradient.
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What direction does the Calcium pump operate?
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It pumps calcium ions OUT of the cell.
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What type/category of membrane proteins are involved in receptor-mediated endocytosis?
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Receptor proteins (duh!).
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What type of surface receptors on the plasma membrane are involved in signaling via phosphorylation?
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Kinases
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What do G-proteins do, basically?
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They are coupled with surface receptors, involved with signaling.
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What is the function for linker and structural proteins in the plasma membrane?
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They are involved in cell-cell attachment, cell matrix attachment, and serve as scaffolding for the cytoskeleton.
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Where is the nuclear lamina located?
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Lining the inside of the inner nuclear membrane.
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What are the dense, dark areas of the nucleus called?
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Heterochromatin - they are dense, inactive regions of DNA.
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What is the lighter-staining region of the nucleus called?
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Euchromatin
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Where in the nucleus is rRNA assembled into ribosomes?
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In the granular portion of the nucleolus.
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What is the difference in constitutive and facultative heterochromatin?
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Constitutie - heterochromatin that remains inactive of transcription
Facultative - can de-condense and become transcriptionally active (depending on cell type) |
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T/F - not all euchromatin in the nucleus is "open" for transcription.
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True. Some are closed, depending on the cell
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What are the major proteins associated with the nucleus?
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histones
fibrous proteins nuclear matrix proteins ribosomal proteins transcription factors polymerases to make DNA |
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Where do the inner and outer membranes of the nuclear envelope join or connect?
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At nuclear pore complexes
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What is each membrane of the nuclear envelope associated with?
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Inner membrane - associates with nuclear lamina
Outer membrane - contiguous with the endoplasmic reticulum. |
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T/F - the nuclear pore is a single protein channel.
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False. It's a large macromolecule consisting of more than 100 proteins.
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T/F - anything can diffuse freely through nuclear pores when they are open.
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False. Small molecules can diffuse freely, large macromolecules require energy
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Besides energy, what to larger molecules require to go through nuclear pore?
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They require a nuclear localization signal (a certain amino acid sequence).
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What amino acids are involved in the nuclear localization signal?
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Basic amino acids like lysine and arginine.
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How are RNA's transported through nuclear pore complexes?
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They are transported as ribonucleoproteins, which requires energy via ATP.
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What do nuclear shuttle/transport proteins do?
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They bring substances to nuclear pore, and tether the substance to the pore. They require energy.
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What is the nucleolus?
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Prominent structure in nucleus that is the site for rRNA synthesis and ribosome assembly.
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T/F - the primary transcript of RNA (no modifications) is processed in the nucleolus to yield mature RNA for ribosome construction.
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True.
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How many ribosomal proteins are in the large of small subunits of a ribosomes, respectively?
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49 proteins in large subunit
33 proteins in small subunit |
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How many histone molecules make up one nucleosome?
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eight
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What is a nucleosome?
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The functional unit of euchromatin that helps organize the DNA and wrap it.
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Where are most cells of the body located in the cell cycle?
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In the arrested, G0 phase.
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What are the 4 distinct phases of the cell cycle?
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M, G1, S, and G2
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What phase of cell cycle is involved in DNA rep?
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S phase
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What happens in the G2 phase of the cell cycle?
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DNA proofreading and organelle multiplication.
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What regulates the progression through specific "control points" in the cell cycle?
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Extracellular signals and cell size.
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T/F - no DNA syntesis occurs in G1 phase?
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True.
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What are ribosomes?
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They are giant macromolecular machines that bring together mRNA and aa-tRNA to synthesize polypeptides
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What proteins and RNA's are included in each subunit of a ribosome?
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- small subunits have 33 proteins and one RNA molecule
- large subunits contain 59 proteins and three RNA molecules. |
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T/F - a ribosome can be recycled?
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True. The subunits dissociated and reform many times.
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What is it called when multiple ribosomes are on one mRNA?
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Polyribosomes
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The subunit numbers for the human ribosomes are what?
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Large Subunit - 60S
Small Subunit - 40S Total - 80S |
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Where can a protein that is sythesized freely in the cytosol go?
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To the nucleus, mitochondria, or peroxisomes, or freely in cytosol
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Where can proteins synthesized by membrane-bound ribosomes go?
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To the plasma membrane, secretory vesicles, or lysosomes.
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What are structures formed as a result of endocytosis, that usually lead to become lysosomes?
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Endosomes
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What ion concentration does the ER regulate?
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Calcium
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Where are lipids synthesized in the cell?
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ER
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Where do the ribosomal subunits bind to on the messenger RNA?
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To the 5 prime end.
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If a protein has no signal sequence related to it, the ribosome will release it where?
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In the cytosol
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What organelles are part of the secretory pathway?
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ER, Golgi, Secretory Vesicles, Endosomes, Lysosomes, and the Plasma Membrane
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What if a protein has an ER signal, but not other specifics, where is the default path after being inserted into ER?
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To the plasma membrane.
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What are the 3 sections/faces of the golgi, starting in and going out?
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Cis, Medial, and Trans
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What do vesicles bud off of the golgia?
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At the trans-golgi network.
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T/F - some post-translational modification of proteins happens at the golgi?
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True.
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Where in the cell do proteins get a sugar added to their ends and become glycoproteins? "terminally glycosylated"
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At the golgi
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T/F - vesicles in golgi travel in one direction.
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False. Flow is bidirectional.
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What is the difference in the constitutive and regulative secretory pathways?
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The constitutive is unregulated and constant secretion (like in fibroblasts)
The regulated is where secretions are kept and released by signals (like Mast cells) |
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What organelle contains degradative enzymes and a low pH of 4.5 - 5.0?
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Lysosomes
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What do proteins have that serve as "recognition" that they are meant for a lysome?
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They have a phosphoyrlated mannose attached. (M6P)
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What pump proteins are important for lysosomes?
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Hydrogen pumps (to lower pH)
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What vesicles are formed by phagocytosis?
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Phagosomes
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What are peroxisomes?
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Membrane-bound organelles containing enzymes that participate in oxidative reactions.
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T/F - peroxisomes oxidize long chain fatty acids to create ATP.
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False. They do oxidize long chain fatty acids, but the energy generated is not used to synthesize ATP
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What organelle is responsible for detoxifying various toxic substances.
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Peroxisomes
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What is is produced when peroxisomes oxidize substrates?
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Hydrogen peroxide, which si broken down by catalase.
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What breaks down hydrogen peroxide?
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Catalase.
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What genetic malfunction in this organelle causes several forms of mental retardation?
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Peroxisomes.
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What organelles in the cell have double membranes surrounding them?
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Mitochondria and the Nucleus
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Where do you find the most mitochondria?
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In areas of high ATP use (sperm tails, muscle cells, nerve terminals)
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What organelle releases toxic cocktail of proteins that brings about death of cell (apoptosis) in response to toxic stimuli?
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MItochondria
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How to mitochondria divide?
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By binary fission.
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Which membrane of the mitochondria is not very permeable?
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The inner (it must regulate hydrogen ion concentration in the intermembrane space)
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What proteolytic structures are located in the cytosol, and not membrane bound?
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Proteasome
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How to cytosolic proteins get tagged to be destroyed by proteasome?
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Tagged with 76 amino acid peptide called ubiquitin
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What are proteasome?
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Large cylindrical structures that float in the cytoplasm and degrade proteins.
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T/F - all the cytoskeletal elements are held together by non-covalent bonds.
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True.
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What cytoskeletal elements are made up of a dimeric molecule called tubulin?
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Microtubules.
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Where do you find microtubules?
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1) mechanical reinforcing rods for cytoskeleton of cell
2) form spindle fibers for chromosome movement 4) Called neurotubules in neurons, provide tracks for movement in axons 5) cilia and flagella component |
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What cytoskeletal component is integral in axons?
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Microtubules
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What is the major site of microtubule polymerization called?
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Centrioles (short cylinders of MT at right angles to one another)
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What cytoskeletal component anchors and reinforces surface of cell?
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Actin (microfilaments)
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What protein supports fingerlike projections of the plasma membrane to facilitate movement and increase surface area (microvilli)
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Actin
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What genetic defect in this actin binding protein causes most common forms of muscular dystrophy?
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Genetic defect in dystrophin, an actin-binding protein
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What cytoskeletal elements provide tracks for ATP powered motor porteins?
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Actin filaments AND microtubules.
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What molecule essentially makes up intermediate filaments?
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The keratin molecule
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What cytoskeletal element forms bundles that link plasma membrane with nucleus?
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Intermediate filaments.
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What cytoskeletal element reinforces nuclear envelope?
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intermediate filaments. And they criss cross around the cell too.
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A genetic defect in this filament causes severe blistering of skin, and other disorders.
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Intermediate filaments
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T/F - intermediate filaments don't usually break under stress.
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True. They are like ropes.
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Which filament will not break under the most stress?
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Intermediate filaments
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T/F - intermediate filaments don't polymerize/depolymerize
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True. Once you form them they don't form/reform like actin and MT.
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What are the inclusions mentioned in class?
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Glycogen, LIpids, Lipofuscin, Skin Pigments (hemosiderin, Melanin), and Crystals.
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What is lipofuscin?
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Brownish, age pigment .
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