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138 Cards in this Set
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cell theory
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1) all living things are composed of cells; 2) the cell is the basic functional unit of life; 3) cells arise only from pre-existing cells; 4) cells carry genetic information in the form of DNA, which is passed from parent cell to daughter cell.
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magnification vs. resolution
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increase in apparent size of an object vs. differentiation of two closely situated objects
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compound light microscope
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uses two lenses or lens systems; total magnification is the product of the eyepiece magnification and the magnification of the selected objective.
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diaphragm of a compound lt microscope
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controls amount of light passing thru specimen
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hematoxylin
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a dye that reveals distribution of DNA and RNA within a cell due to its affinity for negatively charged molecules
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phase contrast microscope
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a special type of light microscope that permits study of living cells; differences in refractive index are used to produce contrast between cellular structures.
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electron microscope
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uses a beam of e- to allow a thousandfold higher magnification than is possible with light microscopy; however tissues must be fixed and sectioned, and sometimes stained with solutions of heavy metals.
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autoradiography
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expose cells to a radioactive compound, incubate, fix at various intervals, and prepare for microscopy; each preparation is covered with a film of photographic emulsion; dark silver grains reveal the distribution of radioactivity within the specimen.
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centrifugation
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separates cells or cell parts by weight, e.g. centrifugation of a eukaryotic cell sediments high-density ribosomes at the bottom, while low-density mitochondria and lysosomes remain at the top.
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cell type of multicellular organisms
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eukaryotic
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cytoskeleton of a eukaryotic cell
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composed of microtubules, microfilaments, intermediate fibers, and other accessory proteins (all found in the cytosol)
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fluid mosaic model
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states that the cell membrane consists of a phospholipid bilayer with proteins embedded throughout; lipids and many of the proteins can move freely within the membrane
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transport proteins
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membrane-spanning molecules that allow certain ions and polar molecules to pass through the lipid bilayer
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two regions of a phospholipid
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hydrophilic (polar) phosphoric acid region (exterior) and hydrophobic (np) fatty acid region (interior)
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CAMs
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cell adhesion molecules = proteins that contribute to cell recognition and adhesion, and are particularly important during development
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receptors
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complex proteins and glycoproteins generally embedded in the membrane with sites that bind to specific molecules in the cell's external environment
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nucleolus
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a dense structure in the nucleus where rRNA synthesis occurs
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ER
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endoplasmic reticulum = a network of membrane-enclosed spaces connected at points with the nuclear membrane. Rough ER = ribosomes line its outer surface, smooth = without ribosomes, involved in lipid synthesis and the detoxification of drugs and poisons
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protein synthesis by RER
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cross into the cisternae of the RER, where they undergo chemical modification, and then cross into smooth ER where they are secreted into cytoplasmic vesicles and transported to the Golgi apparatus.
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Golgi apparatus
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a stack of membrane-enclosed sacs; the Golgi receives vesicles and their contents from smooth ER, modifies them, repackages them into vesicles, and distributes them.
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secretory vesicles
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produced by the Golgi, release their contents to the cell's exterior by the process of exocytosis
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vesicles and vacuoles
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both are membrane-bound sacs involved in the transport and storage of materials that are ingested, secreted, processed, or digested by the cell. Vacuoles are larger and are more likely to be found in plant cells.
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lysosomes
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membrane-bound vesicles that contain hydrolytic enzymes involved in intracellular digestion; enzymes are maximally effective at a pH of 5; lysosomes fuse with endocytotic vacuoles to digest material
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autolysis
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rupturing the lysosome membrane and releasing its hydrolytic enzymes is a method of "suicide" for dying or injured cells
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microbodies
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membrane-bound organelles specialized as containers for metabolic rxns, ex: peroxisomes and glyoxysomes
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peroxisomes
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a microbody that contains oxidative enzymes that catalyze a class of rxns in which H2O2 is produced by the transfer of H from a substrate to O; they break down fats into smaller molecules and are used to detoxify compounds harmful to the body, e.g. alcohol.
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glyoxysomes
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usually found in fat tissue of germinating seedlings; used to convert fats into sugars until the seed is mature enough to produce its own supply of sugars by photosynthesis
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mitochondria
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sites of aerobic respiration, has outer and inner phospholipid bilayer membranes; are semiautonomous = contain their own DNA and ribosomes, which enables them to produce some of their own proteins and to self-replicate by binary fission.
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inner membrane of mitochondria
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has many convolutions called cristae and a high protein content that includes the proteins of the electron transport chain
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mitochondrial matrix
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area bound by the inner membrane, and the site of many of the rxns in cell respiration
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chloroplasts
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or plastids, are found only in plant and algal cells. Contain chlorophyll and are the site of photosynthesis. Exhibit same semiautonomy as mitochondria.
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cell wall of plants vs. fungy
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cellulose vs. chitin
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centrioles
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specialized type of microtubule involved in spindle organization during cell division; not bound by a membrane; animal cells usually have a pair that are oriented at right angles to each other and lie in a region called the centrosome. Plant cells do not contain centrioles.
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microtubules
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hollow rods made up of polymerized tubulins that radiate throughout the cell and provide it with support; provide a framework for organelle movement within the cell; cilia, flagella, and centrioles are all composed of microtubules.
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microfilaments
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solid rods of actin, involved in cell movement as well as support; can move materials across the plasma membrane in the contraction phase of cell division.
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intermediate filaments
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a collection of fibers involved in maintenance of cytoskeletal integrity; diameters fall between those of microtubules and microfilaments
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osmosis
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simple diffusion of water from a region of lower solute concentration to a region of higher solute concentration
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hypertonic vs. hypotonic
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higher solute vs. lower solute concentration
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facilitated diffusion
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or passive transport, is the net movement of particles down their concentration gradient with the help of carrier molecules = does not require energy
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endocytosis
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a process in which the cell membrane invaginates, forming a vesicle that contains extracellular medium; can be pinocytosis (ingetion of fluids or small particles) or phagocytosis (engulfing of large particles)
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exocytosis
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a vesicle within the cell fuses with the cell membrane and releases its contents to the outside
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tissues
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groups of morphologically and functionally-related cells
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4 types of tissues
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epithelial, connective, nervous, and muscle
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viruses
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acellular structures composed of nucleic acid (DNA or RNA, single or dble) enclosed by a protein coat (capsid)
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size of virus vs. prokaryote vs. eukaryote
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20-300 nm vs. 1-10 um vs. 10-100 um
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bacteriophages
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viruses that exclusively infect bacteria
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enzyme without its cofactor
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apoenzyme (with the cofactor = holoenzyme)
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tightly bound cofactors
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prosthetic groups
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coenzymes
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cofacts that are small organic groups, e.g. biotin; usually derived from the diet as vitamins b/c they cannot be synthesized by the body
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thiamin deficiency
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often seen in alcoholics; results in Wernicke-Korsokoff syndrome
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Michaelis-Menten model
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an enzyme-substrate complex is formed at rate k1 from enzyme E and substrate S. The ES complex can either dissociate into E and S at rate k2 or form product P at rate k3.
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Michaelis constant
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Km = (k2+k3) / k1 = ratio of the breakdown of the ES complex to its formation
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Km = [S]
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where rate = 1/2 Vmax, i.e. where half of the enzyme's active sites are filled
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a low Km
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reflects a high affinity for the substrate, i.e. low [S] required for 50% enzyme saturation
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effect of temperature on rxn rate
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rates tend to double for every 10*C increase, until the optimal temperature is reached; at higher temperatures, enzymes become denatured
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effect of pH on rxn rate
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max activity of many human enzymes occurs around pH = 7.2; exceptions include pepsin (pH=2) and pancreatic enzymes, which work optimally in the alkaline conditions of the sm intestine (pH=8.5)
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allosteric enzyme
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has two or more active sites; can oscillate between two configurations, depending on its interactions with its regulator(s)
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allosteric inhibitors vs. activators
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prevents an enzyme from binding to its substrate by stabilizing the inactive conformation vs. stabilizes the active configuration, promoting formation of ES complexes
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feedback inhibition
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the end product of a sequence of enzymatic rxns becomes an allosteric modulator (inhibitor) of one of the preceding enzymes in the sequence
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reversible inhibition
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rxns with weak enzyme-inhibitor complexes that dissociate easily; can be competitive or noncompetitive
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competitive inhibitors
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compete with the substrate directly by binding to the active site of the enzyme, often very similar in structure to the actual substrate (e.g. succinate dehydrogenase is inhibited by malonate); can be overcome by sufficently high substrate concentrations
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noncompetitive inhibitors
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bind to other sites on the enzyme and cause a conformational change such that the enzyme can no longer bind substrate (therefore, cannot be relieved by increased [S])
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irreversible inhibition
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permanent damage is done to the active site, either by tight, covalent bonding of the inhibitor to the enzyme or by denaturation of the active site
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zymogen
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an enzyme that is secreted in an inactive form; cleaved under certain physiological conditions to the active form of the enzyme; ex: pepsinogen, trypsinogen, and chymotrypsinogen
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anabolic
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energy-requiring processes, involving the biosynthesis of complex organic compounds from simpler molecules
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catabolic
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release energy as complex organic molecules are broken down
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autotrophic
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convert sunlight into bond energy stored in the bonds of organic compounds (mostly glucose) in the anabolic process of photosynthesis
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heterotrophic
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obtain energy catabolically, via the breakdown of organic nutrients that must be ingested
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net rxn of photosynthesis
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6CO2 + 6H2O + energy = C6H12O6 + 6CO2
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ATP
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adenosine triphosphate = nitrogenous base adenine, the sugar ribose, and three weakly linked phophate groups
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energy stored in in the high-energy phosphate bonds of ATP
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7 kcal/mole
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NAD+
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nicotinamide adenine dinucleotide
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FAD
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flavin adenine dinucleotide
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NADP+
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nicotinamide adenine dinucleotide phosphate
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glycolysis
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the oxidative breakdown of glucose into two molecules of pyruvate, the production of ATP, and the reduction of NAD+ to NADH; occurs in the cytoplasm
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deficiency of pyruvate kinase
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(the final enzyme in the glycolytic pathway) leads to a form of anemia (hemolytic anemia) in which, due to a lack of a ATP, red blood cells are unable to maintain their shape. The spleen tends to sequester and destroy these deformed rbc's, causing hemolytic anemia.
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net rxn of glycolysis
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glucose + 2ADP + 2Pi + 2NAD+ = 2Pyr + 2ATP + 2NADH + 2H+ + 2H2O
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fermentation
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glycolysis + reduction of pyruvate to ethanol or lactic acid and regeneration of NAD+ (yields 2ATP per glucose)
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alcohol fermentation
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occurs in yeast and some bacteria; pyruvate is decarboxylated to acetaldehyde, which is then reduced by NADH to yield ethanol
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lactic acid fermentation
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occurs in certain fungi, bacteria, and in human muscle cells during strenuous activity (in humans, the accumulation of lactic acid casuse a decrease in blodd pH that leads to muscle fatigue)
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oxygen debt
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the amount of oxygen needed to oxidize lactic acid back to pyruvate, so it can enter cellular respiration
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cellular respiration
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an aerobic process in which oxygen acts as the final e- acceptor; occurs in the eukaryotic mitochondrion; divided into three stages = pyruvate decarboxylation, TCA, and e- transport chain
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pyruvate decarboxylation
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occurs in the mitochondrial matrix; NAD+ is reduced to NADH as the acetyl group is transferred to coenzyme A
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TCA cycle
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tricarboxylic acid cycle: acetyl CoA + oxaloacetate forms citrate...
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net rxn of TCA
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2Acetyl CoA + 6NAD+ + 2FAD + 2GDP + 2Pi + 4H20 = 4CO2 + 6NADH + 2FADH2 + 2ATP + 4H+ + 2CoA
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ETC
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e- transport chain = a complex carrier mechanism located on the inside of the inner mitochondrial membrane
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cytochromes
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electron carriers that resemble hemoglobin in the structure of their active site - functional unit contains a central iron atom, which is capable of undergoing a reversible redox rxn
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FMN
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flavin mononucleotide = first molecule of the ETC, accepts e- from NADH
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cytochrom a3
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the last carrier of the ETC, passes its e- to O2
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cyanide and ETC
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CN- blocks the transfer of e- from cytochrom a3 to O2
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dinitrophenol and ETC
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uncouples the ETC from the proton gradient established across the inner mitochondrial membrane
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protein complexes of the ETC
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NADH dehydrogenase, b-c1 complex, and cytochrome oxidase
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FADH2 and ETC
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FADH2 delivers its e- to carrier Q (ubiquinone), which lies between NADH dehydrogenase and b-c1 complexes - therefore, only 2 ATP are produced per FADH2 (as opposed to the 3ATP produced per NADH)
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ATP synthetases
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use the proton motive force created by the ETC to phosphorylate ADP to ATP - H+ flow from the intermembrane space back to the mitochondrial matrix
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oxidative phosphorylation
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the coupling of the oxidation of NADH with the phosphorylation of ADP
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NADH produced by glycolysis, vs. those produced by cellular respiration
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NADH produced by glycolysis cannot cross the inner mitochondrial membrane, and therefore must transfer their e- to an intermediate carrier molecule which delivers the e- to the second carrier protein complex Q = 2ATP produced, instead of 3.
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ATP production per glucose molecule
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glyclolysis: -2 (invested) + 4 (substrate, ATP) + 4 (oxidative, NADH); pyruvate decarboxylation: +6 (oxidative, NADH); TCA: +18 (oxidative, NADH) + 4 (oxidative, FADH2) + 2 (substrate, GTP) = 36 ATP
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order of preference for other energy sources
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other carbohydrates > fats > proteins
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fat storage
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stored in adipose tissue in the form of triglyceride; when needed they are hydrolyzed by lipases to fatty acids and glycerol (which can be converted to glyceraldehyde 3P)
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beta-oxidation cycles
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convert a fatty acid (that has been activated by 2ATP in the cytoplasm) into 2-C fragments, which are then converted to acetyl CoA; each round produces 1NADH and 1FADH2... fats yield the greatest #ATP per gram
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transamination rxn
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loss of an amino group by an amino acid to form an alpha-keto acid????
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binary fission
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a type of asexual reproduction and (prokaryotic) cell dvision; the single DNA molecule attaches to the plasma membrane during replication and duplicates while the cell continues to grow in size.
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somatic cells
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or autosomal = contain the diploid number of chromosomes characteristic of its species
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2n for humans?
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46 (so the haploid number is 23)
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four stages of the eukaryotic cell cycle
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G1, S, G2, and M
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interphase
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G1, S, and G2; the longest part of the cell cycle; a cell normally spends at least 90% of the cycle here
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G1
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presynthetic gap = intense biochemical activity and growth in which the cell doubles in size; once the cell passes a restriction point, it is committed to continue through the rest of the cell cycle and divide
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G0
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a nondividing phase; some cells including specialized skeletal muscle cells and nerve cells enter this phase instead of passing through the restriction point during G1
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S stage
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synthesis = each chromosome is replicated, so that the chromosome consists of two identical sister chromatids held together at a central region called the centromere
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telomeres
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the ends of the chromosome (as opposed to the centromere)
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G2
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postsynthetic gap = cell continues to grow in size while assembly of new organelles and other cell structures continue
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M stage
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mitotic stage = mitosis and cytokinesis
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chromatin
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the active, uncoiled DNA of interphase; individual chromosomes are not visible under a light microscope
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mitotic stages
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prophase, metaphase, anaphase, and telophase
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prophase
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chromosomes condense, centriole pairs move toward opposite ends of the cell and the spindle apparatus forms between them; nuclear membrane dissolves and nucleoli become less distinct or disappear
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kinetochores
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appear during prophase at the chromosome centromere and have attached kinetochore fibers
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metaphase
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kinetchore fibers interact with the fibers of the spindle apparatus to align the chromosomes at the metaphase plate (or equatorial plate)
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anaphase
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the centromeres split so that each chromatid has its own distinct centromere (telomeres are the last part of the chromatids to separate); sister chromatids are pulled toward opposite ends of the cell by the shortening of the kinetochore fibers
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telophase
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spindle apparatus disappears and a nuclear membrane forms around each set of chromosomes
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spindle fibers consists of...
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microtubules and associated proteins
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asters
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structures formed by the spindle fibers radiating outward from the centrioles = the spindle apparatus
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cytokinesis
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division of the cell -- a cleavage furrow forms in animal cells
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asexual reproduction
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the production of offspring without fertilization
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types of asexual reproduction
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binary fission, budding, regeneration, and parthenogenesis
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budding
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replication of the nucleus followed by unequal cytokinesis, occurs in hydra and yeast
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regeneration
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the regrowth of a lost or injured body part, replacement of cells occurs by mitosis
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parthenogenesis
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the development of an unfertilized egg into an adult organism; since the organism develops from a haploid cell, all of its cells will be haploid
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meiosis
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the process by which gametes are produced
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name of cells that undergo meiosis
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gametocytes or "germ cells"
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prophase I (of meiosis)
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synapsis occurs, chromtin condenses, spindle apparatus forms, and the nucleoli and nuclear membrane disappear
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synapsis
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the pairing and intertwining of homologous chromosomes to form a tetrad
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tetrad
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a synaptic pair of homologous chromosomes, contain 4 chromatids
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crossing over
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the exchange of equivalent pieces of DNA between chromatids of homologous chromosomes (not between sister chromatids)
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chiasmata
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points at which chromosomes remain joined where crossing over occurred
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anaphase I (of meiosis)
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disjunction = homologous pairs separate and are pulled to opposite poles of the cell
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homologous chromosomes or sister chromatids fail to separate
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nondisjunction (occurs during anaphase I or II) -- results in one gamete having two copies of a particular chromosome and the otehr having no copies
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examples of nondisjunction
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trisomy 21, Down's syndrome (autosomal chromosomes), Klinefelter's, Turner's (sex chromosomes)
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number of female gametes formed per meiotic cycle
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only 1 functional gamete (although 4 haploid daugher cells are produced)
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