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139 Cards in this Set
- Front
- Back
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What is the smallest entity capable of independent reproduction, of metabolism, and of maintaining a stable internal environment in the midst of a variable external environment?
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cell
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What cell structures do prokaryotes have?
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ribosomes DNA no nuclei nor other membrane-bound organelles |
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Where do metabolic processes occur in prokaryotic cells?
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cytoplasm
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Describe prokaryotic DNA. |
single circular molecule attached to the plasma membrane
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How do prokaryotic cells replicate? |
binary fission
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Are single-celled organisms prokaryotic or eukaryotic? |
can be either
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What is the cytosol? |
intracellular fluid |
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What does the cytoplasm consist of? (3)
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cytosol cytoskeletal elements organelles |
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What percentage of the cytosol is made up of water? Proteins? |
70% 20% |
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What type of molecules dissolve readily in water? |
hydrophilic
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What binds peripheral proteins to phospholipids or integral proteins? |
noncovalent attractions
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What are proteins that carry branching oligosaccharide chains on the exoplasmic surface of the cell? |
membrane receptors
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What do the carbohydrate side chains attached to membrane proteins (glycoproteins) and glycolipids of the phospholipid bilayer form? |
outer halo of carbohydrate called a glycocalyx that surrounds the cell
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What within the glycocalyx are unique to every individual and what are they for?
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carbohydrate side chains, cell-cell communication
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Are membranes with phospholipids composed of unsaturated fatty acids more or less fluid than those with saturated fatty acids? Why? |
More. Double bonds cause the carbon chains to kink, keeping fatty acids from packing together tightly.
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Are membranes with large amounts of cholesterol more or less fluid than those with less cholesterol? Why? |
Less, cholesterol interferes with phospholipid movement. At low temperatures, however, cholesterol keeps membranes from solidifying.
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What molecules have no difficulty crossing the lipid layer? |
small, uncharged particles nonpolar, hydrophobic molecules |
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What is a term for the relative solute concentration of a solution? |
tonicity
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What will the net movement of water by osmosis be for a hypotonic solution? |
out
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What drives the movement of materials in passive transport?
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KE
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Why does simple diffusion occur? |
collisions occur more frequently in areas of high concentration
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What is osmotic pressure? |
pressure generated by the presence of solutes (water-soluble molecules) dissolved in water
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If the concentration of solutes (osmotic pressure) is higher on one side of a membrane, the net flow of water will continue toward the more concentrated solution until what? |
hydrostatic pressure of water building up on that side counterbalances the osmotic pressure, or until the membrane ruptures
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What happens when a plant cell is placed in distilled water? |
Turgor pressure increases as it swells, but it doesn't burst.
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What happens when a red blood cell is placed in distilled water? |
It will rupture (hemolyze) because the cell membrane cannot withstand the pressure of the influx of water.
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What happens when a plant cell is placed in a hypertonic solution? |
The cytoplasm will shrivel and shrink away from the cell wall (plasmolyze).
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What happens when a red blood cell is placed in a hypotonic solution?
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It will shrivel (crenate).
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What is facilitated diffusion? |
passive transport using transport proteins (gates or carriers)
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Is passive transport spontaneous? |
yes
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What are channel proteins? |
amphipathic transmembrane molecules with a region of hydrophilic amino acids on the interior
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What are chemically gated ion channels? |
ligand gated
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What is a substance that binds to a biological molecule (usually to trigger a signal)? |
ligand
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What is the mechanism of carrier proteins? |
bind to solutes and undergo a conformational change that physically carries the solute molecule across the membrane
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How does the sodium potassium pump work? |
Sodium binds to the ATPase on the cytoplasmic side of the membrane. ATP hydrolyzed (converted to ADP). Protein phosphorylated, changing its conformation and pumping sodium out of the cell. New conformation has high affinity for extracellular potassium, which binds and triggers the release of the phosphate group. Protein reverts to its original conformation, releasing potassium into the cell and regaining a high affinity for sodium. |
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What is bulk transport?
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endocytosis and exocytosis
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What are membrane-bound sacs that surround a substance to be exported or imported? |
transport vesicles
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What are three ways endocytosis occurs? |
phagocytosis (cell eating) pinocytosis (cell drinking) receptor-mediated endocytosis |
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What are pseudopodia? |
extensions of the plasma membrane formed in phagocytosis
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What does a pinched-off pocket of membrane become? |
large transport vesicle called a vacuole
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What happens to particles brought in by phagocytosis? |
Lysosomes fuse with the membrane of the vacuole and digestion occurs.
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How does pinocytosis occur and what does the cell use it for?
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The cell membrane folds inward (invaginates) to suck extracellular fluid and its solute contents into a pouch that becomes a vesicle. Pinocytosis is used to sample the contents of extracellular fluid. |
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What allows a cell to take in particular substance regardless of their concentration outside of the cell? |
receptor-mediated endocytosis
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Where are receptor proteins for endocytosis located? |
in plasma membrane depressions
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How does exocytosis function in cell growth?
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fusion of vesicle membrane with plasma membrane increases membrane size
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What form an electrochemical gradient across a membrane? |
membrane potential (charge separation) and chemical gradient (concentration differences)
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What disease is a progressive deterioration of brain function caused by a harmful buildup of membrane-derived sphingolipids in brain neurons? |
Tay-Sach's
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What body system utilizes autocrine signaling? |
immune system
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What signaling occurs between cells that are in direct physical contact with each other? |
juxtacrine signaling
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What is juxtacrine signaling important for? |
cell differentiation during development electrical signals in cardiac cells |
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What involves chemical messengers that send signals over short distances between nearby cells?
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paracrine signaling
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What involves hormones that function in long-distance communication by traveling through the bloodstream to target cells? |
endocrine signaling
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What is the process by which the binding of an extracellular signal molecule is converted to an intracellular response?
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signal transduction
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What is a sequence of metabolic steps? |
pathway
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What does the presence of multiple intermediaries in a transduction cascade allow for? (3) |
amplification feedback loops signal propagation |
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What is the first messenger in a signal transduction cascade? |
extracellular signal molecule
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What do G-proteins do after activation?
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produce effector that stimulates synthesis of second messenger, which goes on to activate an intracellular process
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When are ribosome subunits separated?
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when the ribosome is not synthesizing protein
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What is a ribozyme?
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RNA enzyme
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What is the structure of ribosomes in prokaryotic cells? |
30S + 50S = 70S |
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What is the structure of ribosomes in eukaryotic cells? |
40S + 60S = 80S
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What is the function of the nucleolus?
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location of RNA and ribosome assembly within the nucleus
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What is the function of rough endoplasmic reticulum? |
protein synthesis
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What is the function of smooth endoplasmic reticulum? |
lipid synthesis detoxification of drugs and other toxins (liver) |
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What is the function of the Golgi apparatus? |
packaging and transport of proteins and lipids
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What is the function of vacuoles? |
storage of water, food, and wastes
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What is the function of lysosomes?
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contain digestive enzymes
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What is the function of peroxisomes? |
contain hydrogen peroxide and oxidative enzymes for beta oxidation of fatty acids
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What are centrioles?
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pair of rod-shaped proteins that function in cell division
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What is cytoskeleton?
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protein scaffolding that provides cell structure, support, and motility
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What is nucleoplasm?
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interior region of the nucleus that contains the DNA
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What is the nuclear lamina?
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cytoskeletal support network of the nucleoplasm
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Describe the outer layer of the nuclear membrane. (2)
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may be embedded with ribosomes continuous with other membrane-bound organelles in the cytoplasm, such as ER |
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Does the nucleus contain one or many nucleoli?
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depends on the type of cell
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What is a complex of DNA and protein?
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chromatin
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What are histones and what do they bind to? |
positively charged proteins that bind to the negatively charged phosphate backbone of DNA
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What are nucleosomes?
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DNA wrapped around 8 histone proteins to form the basic structural unit of chromatin
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What is the function of nucleosomes? |
to be further wrapped into DNA supercoils
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What is loosely coiled DNA that is actively involved in gene expression? |
euchromatin
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What is an inactive form of DNA?
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heterochromatin
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What is constitutive heterochromatin? |
permanently inactive
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What is facultative heterochromatin?
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temporarily inactive
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What are sister chromatids?
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replicated chromosomes joined at a centromere
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What is a genophore?
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circular DNA molecule of prokaryotic cells
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Where does the citric acid cycle occur?
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mitochondrial matrix
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Where are the proteins of the electron transport chain and ATP synthesis embedded?
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inner mitochondrial membrane
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Does the inner or outer mitochondrial membrane contain porins for small molecules?
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outer, the inner is highly impermeable
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What are cristae? |
inward folds of the inner mitochondrial membrane through the matrix
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Is mitochondrial DNA linear or circular?
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circular
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What organelle has its own ribosomes?
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mitochondrion
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What hypothesis states that mitochondria originated as prokaryotes that were engulfed and incorporated (by endocytosis) into an ancestral eukaryotic cell? |
endosymbiotic hypothesis
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What is an example of cytoplasmic (extranuclear) inheritance and why?
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Mitochondrial DNA. It is replicated independently of nuclear DNA.
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What has been used as a molecular clock to determine the time of divergence between different species and populations and why?
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Mitochondrial DNA (mtDNA). It has a rapid mutation rate compared to nuclear DNA.
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What are cisternae?
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network of membranes and flattened, fluid-filled sacs of the ER
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What is protein synthesis initiated by?
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free ribosomes in the cytosol
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What are proteins tagged with during synthesis?
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short sequences of amino acids called signal sequences or targeting peptides, which determine the proteins' ultimate destinations in the cell
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Where may protein synthesis be completed and what does this depend on?
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cytoplasm or it may be cotranslationally translocated to the RER membrane
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What happens to proteins that pass into the lumen of the rough endoplasmic reticulum?
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They are folded with the assistance of chaperone proteins and may have carbohydrate side chains added.
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Where do proteins go after the lumen of the RER?
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Golgi body
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What happens to proteins that are transported to the RER but remain embedded in is membrane?
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used in membrane biosynthesis
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Can rough and smooth ER be interconverted?
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Yes, depending on the needs of the cell
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What are two forms of posttranslational modification that may help direct a protein to its final destination and where do they occur?
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glycosylation (addition of sugars), phosphorylation Golgi body |
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Where are Golgi bodies particularly abundant?
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cells of the digestive and respiratory tracts and in other tissues that involve secretion
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How does apoptosis occur?
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Lysosomes disintegrate and release their digestive enzymes throughout the cell.
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When is apoptosis important? (2)
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during development when cells are aged or defective |
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What organelle is important in maintaining osmotic balance?
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vacuole
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What organelles are not associated with other membranous vesicles within the cell and are capable of self-replicating by absorbing materials from the cytoplasm?
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peroxisomes
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What do peroxisomes do to hydrogen peroxide?
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break it down into oxygen and water or use it to breakdown/detoxify other substances
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What are the three components of the cytoskeleton?
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microfilaments intermediate filaments microtubules |
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What are actin filaments?
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microfilaments
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What participate in animal cell division through the formation of the cleavage furrow?
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microfilaments
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What are one of the main components of the nuclear lamina?
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intermediate filaments
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What element of the cytoskeleton is keratin composed of?
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intermediate filaments
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What is the largest cytoskeletal element?
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microtubule
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What element of cytoskeleton is composed of alpha and beta subunits to form a basic dimer from which the polymer is assembled? What is the significance of this?
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Microtubules. The molecule can be lengthened or shortened to generate force to push or pull materials apart.
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What are cilia and flagella composed of?
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microtubules
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What are long, whiplike bundles of microtubules that project from the cell membrane to propel spermatozoa or single-celled protists through a liquid medium?
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flagella
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What are clusters of microtubules that typically occur in groups on the external surface of a membrane?
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cilia
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What is the functional unit of motile cilia and flagella?
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central core or skeleton (axoneme) and a basal body
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What is an axoneme?
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ring of 9 pairs of microtubules arranged lengthwise around 2 central microtubules (9+2 arrangement)
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What are microtubule pairs joined by?
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cross-linking dynein proteins, which act as molecular motors
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How is an axoneme attached to a cell?
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basal body of 9 clusters of 3 microtubules
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What resemble the basal bodies of cilia and flagella in the triplet arrangement of 9 sets of microtubules and where are they found?
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centrioles, centrosome
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What function as microtubule organizing centers of the mitotic spindle during cell division?
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centrosomes
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What are plant cell walls composed of?
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cellulose fibers
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What provides a supportive framework for cells and tissues?
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extracellular matrix
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What does the ECM occupy?
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interstitial matrix between cells
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What is the basement membrane?
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formed by ECM, anchors and underlies epithelial tissues
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What protein forms connective tissue?
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collagen
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What are proteoglycans and what do they associate with?
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heavily glycosylated proteins attached to glycosaminoglycans collagen |
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What binds the ECM to integrin?
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fibronectin
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Where are integrin proteins located?
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in the plasma membrane
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What protein provides a communication pathway between the internal environment of the cell and the ECM?
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fibronectin
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What do cells that adhere to one another to form tissues in multicellular organisms rely on?
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intercellular junctions
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What are the three primary intercellular junctions in animal cells?
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gap junctions tight junctions desmosomes |
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What is the function of gap junctions?
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connect the cytoplasm of adjacent cells across a gap of interstitial space by means of integral membrane protein channels
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What allow chemical and electrical signals to be transmitted quickly and how do they do this?
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Gap junctions. They provide a direct passageway for ions and small molecules.
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What allow all cardiac cells to contract simultaneously?
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gap junctions
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What do gap junctions consist of?
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six connexin monomers forming connexon with open and closed conformations
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What are desmosomes?
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dense cellular adhesions that act as protein anchors to hold cells together in tissues
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