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Cell Biology

Mitochondria, Chloroplasts, Peroxisome & Cytoskeleton

QuestionAnswer
What is the function of the Mitochondria? Generates energy from the breakdown of lipids and carbohydrates
What are the two types of metabolism? catabolism and anabolism
Which type of metabolism is where large things and breaking them down into small things to produce energy? catabolism
Which type of metabolism is where small things and energy create large things? anabolism
What is the biological conversion from one form to another? metabolism
What are the numerous folds in the inner membrane of the mitochondria? cristae
What is the interior of the organelle of the mitochondria? matrix
Where does glycolysis occur? in the cytosol
What happens in glycolysis? Glucose is converted into two Pyruvates with the creation of 2 NADH and 2 ATP
What are NADH and FADH2? electron carriers
What happens to the two pyruvate once it enters into the mitochondria? PDH enzyme converts pyruvate to acetyl-CoA + CO2 with NADH
What is the principal site of ATP generation? The inner mitochondrial membrane
Which membrane is highly permeable to small molecules? the outer mitochondrial membrane
What are channels that allow the free diffusion of molecules smaller located on the outer membrane of the mitochondria? porins
How do mitochondria create diversity in their genome that remodels the network and affect its function and morphology? fission and fusion
What is the partnership where one cell lives within another? endosymbiosis
What are the genes found in the mitochondrial genome? 13 protein- coding sequences, 12S, 16S rRNAS and 22tRNAs
Where are most of the mitochondrial proteins actually transcribes? in the nucleus
What is the theory how the nucleus got genes for proteins of the mitochondria? the genes where thought to have transferred to the nucleus from the ancestral mitochondria genome
How is the 22 tRNA accomplished compared with the 64 tRNA in the whole cell? extreme form of woddle in which U in the anticodon of the tRNA can pair with any of the four bases in the third codon position
What is a disease that leads to blindness and is caused by mutations in mitochondrial genes that encode components of the electron transport chain Leber's hereditary optic neuropathy
Proteins that contain what are directed through the translocon in the mitochondrial outer membrane to diferent mitochondrial compartments? at least 4 classes of specific targeting signals
What targets proteins to the mitochondrial matrix that is an amino-terminal sequence of 20-35 amino acids Presequence
What removes the presequence following import into the mitochondria? proteolytic cleavage
How are proteins that contain mitochondria-specific presequences imported? 1)presequence binds to TOM on surface of mitochondria 2)proteins are then translocated across the outer membrane by the TOM 40 pore 3)Proteins are transferred to TIM allowing translocation or integration in using e- potential
What cleaves the presequence in the matrix? matrix-processing peptidase
What is the process where electron's derived from NADH and FADH2 combine with O2 and the energy released from these oxidation/reduction reactions is used to drive ATP synthesis? oxidative phosphorylation
What passes electrons through a series of carriers to create a proton gradient? electron transport chain
Where do electrons from NADH enter the electron transport chain and this also transferes to coenzyme Q resulting in H+ transfering into the intermembrane space? Complex 1
Where are electrons tranfers from Succinate(via FADH2) to which then transfers them to coenzyme Q? Complex ii
What are the two names for coenzyme Q and why are they called this? Ubiquinone is oxidzed from, Ubiquinol is the reduced form
Which form of coenzyme Q carries the electrons from complex I & II to complex III? ubiquinol
What transfers electrons from ubiquinol to a water soluble protein called cytochrome C resulting in H+ pumping across the membrane? Complex III
What is a peripheral protein bound to the outer face of the inner membrane that carries electrons to complex IV Cytochrome c
What happens to the electrons at complex IV? they are transferred to O2 to form water also H+ pumping occurs across the membrane
What complexes pump protons? 1,III and IV
Which initial electron carrier ended up causing more protons to be pumped: NADH or FADH2? NADH
What is the mechanism of coupling electron transport to ATP generation? cheiosmotic coupling
Who proposed the chemiosmotic hypothesis? Peter Mitchell
Why is the chemiosmotic hypothesis incorrectly named? b/c osmotic referrs to the diffusion of solvents where this hypothesis referrs to the diffusion of solutes which is dialysis
How does the electrochemical gradient drive the transport of molecules across the inner mitochondrial membrane? proton gradient going through ATP synthase
What is the difference in chemical concentration and electric potential across a membrane Electrochemical gradient
What is a membrane spanning protein complex that couples the energetically favorable transport of protons across a membrane to the synthesis of ATP? ATP synthase
For every NADH and FADH2 how many ATP are produced? 3, 2
For one glucose what is the gross yield and net yield for ATP? 38, 36
What is the difference between the gross yield of ATP and net yield for cellular respiration? Minus 2 ATP to import cytoplasmic NADH into mito
What is the evidence for the chemiosmotic model? ET causes protons to be pumped out ofmatrix. OP requires membrane-enclosed compartment. Membrane vesicles containing complexes I, III, or IV establish proton gradients. Uncoupling agents abolish both proton gradient &ATP synthesis.
What are the three membranes of the chloroplast? Outer membrane, inner membrane, and thylakoid membrane
What are the spaces of the chloroplast? intermembrane space, stroma and Thylakoid space
Compared with the mitochondrial gemone how is the chloroplast's? larger and more complex containing 150 genes
What does the chloroplast genome encode? 23S, 16S, 5S,4.5S, 30tRNA, and proteins involved in gene expressioin as well as proteins involved with photosynthesis
How do the tRNAs translate in chloroplast? all codons follow the universal genetic code unlike mitochondrial tRNA
How are proteins imported into the stroma of the chloroplast? 1)Imported by a transit peptides binding to guidance complex which guides to TOC which drives protein import through ATP hydrolysis 2)the protein then attaches to TIC and transported into the stroma
What is the difference between the chloroplasts and the mitochondria in terms of structure and function? The thylakoid memebrane
What is the n-terminal sequence of 30 to 100 amino acids long that sends the protein to the chloroplaste? transit peptides
What recognizes the transit sequence and directs them to Toc complex? guidance complex
What cleaves the transit peptides in the stroma? stromal-processing peptidase
What do proteins have that enable them to cross the thylakoid membrane? When is it exxposed? a second signal sequence, after cleavage of transit peptide
How are Chloroplasts related to plastids? contain the same genome, chloro. is specialized for photosynthesis & are the only ones to have thylakoid membrane
What pigment does chloroplasts contain? chromoplast? Leucoplasts? chlorophyll, carotenoids, none
What plastid is responsible for the yellow, orange and red colors of some fruits and flowers with an unclear precise function? chromoplasts
What plastid stores a variety of engery sources in nonphotosynthetic tissue? Leucoplasts
What are all plastids derived from that are small undifferentiated organelles in rapidly dividing cells ? proplastids
How do chloroplasts develop from proplastids? only in the presence of light
How are proteins imported into the stroma of the chloroplast? Harvesting of light energy and conversion into chemical energy as carbohydrate
What are the two stages of photosynthesis? the light reaction and the calvin cycle
Where does the light reaction occur? the dark reaction/calvin cycle? thylakoid membrane and the stroma
What does the absorption of light do? excites an electron to a higher energy state, thus converting the energy of sunlight to potential chemical energy
how are the photosynthetic pigments organized? into photocenters with hundreds of antenna pigment molecules with a chlorophyll reaction center
When light hits an antenna pigment through what sequence are the electrons transported to and from? it transfers energy from Antenna pigments to chlorophylls, which transfers electrons to pheophytin and then to quinones a membrane soluble molecule
What are the use of accessory pigments? to allow for absorption of additional wavelengths of light
What are the chlorophyll center pigments referred to as? special pair
What is the sequence of events in the light reaction? A photon hits Photosystem II which transfers e- to plastoquinone, which transfers to cytochrome bf where H+ is pumped into lumen, e- then go to to photosystem 1 by plastocyanin
What happens at photosystem 1? energy derived from light absorption generates more e- which are transfered to ferredoxin and used to reduce NADP+ to NADPH in the stroma
What replaces the lost electrons in photosystem ii? the splitting of water which also helps to establish a proton gradient
What uses energy stored in the proton gradeint to convert ADP to ATP in the light reaction of the stroma ATP synthase
What transfers electrons from ferrodoxin to NADP+ in the stroma? NADP reductase
What is the pathway of the Cyclic Electron flow? Light energy absorded in PS1 transfers e- to cytochrome bf through PQ, which lower eanery and pumps H+ into the lumen, e- then transferred to PC and back to PS 1
What provides the energy for electron excitation/ejection? photons
What replaces the electrons lost by PS II and PS I? Water, e- from PS II
What is the final electron acceptor of non-cyclic electron flow? NADPH
Where does the H+ gradient come from? photosystem ii and cytochrome bf
What three useful products come from the light reaction? oxygen ATP and NADPH
One molecule of glucose is produced ffrom... in the .... 6 CO2, 18ATP, 12NADPH
If one years worth of photosynthesis was in the form of sugar cubes stacked end to end, they would reach ... 1.6*10^10 to Pluto
What does the plant do with glucose? store/ use as energy, cellulose, metabolism
What are small single-membrane-enclosed organelles that contain enzymes involved in a variety of metabolic reactions? peroxisomes
What are the functions of a peroxisome? breaking down of substrattes by oxidative reactions which leads to production of H2O2, synthesis of lipids and amino acids, in animal cells cholesterol &dolichol are sythesized, in seeds convert stored fatty acids to carbo.
What converts hydrogen peroxide to water or uses it to oxidize another organic compound? catalase
How are peroxisomes assembled? begins in ER: Pex3 & Pex19 initially localize and initiate budding of a nascent peroxisome, additional peroxins are synthesized on cytosolic rib. and imported to form functional peroxisomes
What is the function of the cytoskeleton? cell shape, cell movement internally and cellularly, position of organelles
What are the three types of protein filaments? actin filaments, intermediate filaments, and microtubulus
What is the major cytoskeleton protein which polymerizes to form actin filaments? actin
What are thin, flexible fibers organized into higher-order structures with properties of semisolid that provides mechanical support, determines cell shape and allows movement of the cell surface thereby enabling cells to migrate, engulf particles& divide actin filaments
What is a dynamic behavior of actin filaments and microtubules in which the loss of subunits from one end of the filament is balanced by their addition to the other end? treadmilling
what is the name of the actin monomer? globular G actin
How do G actin combine? they have tight binding sites that mediate head to tail interactions with two other actin monomers
What do G actin polymerize to form? filament f actin
What are the two ends of and F actin called and which is which? pointed end is where the point is and barbed end is where the nobulal is?
Which end of an F actin elongates faster, which dissociates faster? Barbed, Pointed
how do F actin grow? actin monomers bind to ATP which is then hydrolysized to ADP following filament assembly
Why is ATP used if it is not required for polymerization? ATP binds the F actin monomers more readily
What binds to the barbed end of actin filaments and block elongation? cytochalasins
What drug binds to the actin filament and prevents their dissociation into individual actin molecules phalloidin
What protein nucleates the initial actin monomers by moving along the growing filament and adding new monomers to the barbed end? formins
What protein binds to actin filaments and initiates the formation of branches? Arp 2/3
What diverse group of proteins assemble and disassemble actin filaments? actin-binding proteins
What proteins help to regulate actin polymerization? capping proteins, filament stabilizing protein, severing protein, cross-linking proetins, Polymerizing protein and Depolymerizing protein
What protein switches ATP for ADP ATP-ADP exchange protein
Whatis an actin depolymerizing fact? what is a polymerizing factor? ADF/cofilin, profilin
What is a type of actin structure where the filaments are cross linked into closely packed parallel arrays? actin bundles
What is an actin structure where the filaments are cross linked in orthogonal arrays that form 3D meshworks with properties of semisolid gels? actin networks
What major actin-binding protein provides the structural basis for the cortical cytoskeleton in erythrocytes spectrin
What provides the major link-between the specttin-actin network and the plasma membrane? ankyrin
what is the function of integrins in the attachment of actin to the plasma membrane integrins span the membrane and attach to the extracellular matrix as well as provide a focal adhesions to talin and alpha-actinin
what transmembrane protein provides contact between cells at adherens junctions that with catenin anchor actin filaments to the plasma membrane? cadherins
how are actin filaments arranged in microvilli? in closely packed parallel bundles of cross-linked actin filaments
How are actin filaments arranged in pseudopodia? in cross-linked 3D networks of actin filaments
What are the functions of intermediate filaments? to provide structural mechanical strength to cells and tissues and provide a scaffold for the localization of cellular processes
What are some examples of intermediate filament proteins? nuclear lamins and Keratin proteins
Which intermediate filament protein are used in the production of structures stuch as hair, nails and horns as well as epithelial cells? Keratin
What is the structure of intermediate filament proteins? central alpha-helical rod domain of 310aa, central rod flanked by amino- and carboxy- terminal domans
What is the assembly of an intermediate filament? 1 formation of dimers where central domain winds 2 then chain associates in a staggered antiparallel tetramer 3 no distinct ends 4
What are some differences between actin and IF? IF= apolar, more stable do not exhibt dynamic behavior
how has keritin's importance been examined experimentally? Fuchs used transgenic mice to investigate the in vivo effects of expressing a kertin deletion mutant encoding a truncated polypeptide that disrupted the formation of normal keratin filaments
What did this keritin experiment result in and find? Mice developed a severe skin abnormalities including blisters due to epidermis cell lysis, they found that keritin provides mechanical strength and it is similar to a human disease known as EBS
What is the third principle of the cytoskeleton that are rigid hollow rods that are dynamic structures that function in cell shape, cell movement, and separation of chromosomes? microtubules
What protein composes microtubules? What are the two ends of a microbulule called Tubulin, the minus and plus ends
What are the three types of Tubulin and their functions? alpha and beta combine to form dimers that make up microtubules, gamma tubulin is consentrated in the centromeres and plays a critical role in initating microtubules assembly
How are microtubules polymersized and depolymersized? Both alpha and beta tubulin bind to GTP causing polymerization, beta is then hydolysized weaking the binding affinity of tubulin which then leads to depolymerization
What is the dynamic behavior in which tubulin molecules bound to GDP are continually lost from the minus end and replaced by the addition of tubulin molecules bound to GTP to the plus end of the same microtubule? Treadmilling
What is rapid GTP hydrolysis in which individual microtubules alternate between cycles of growth and shrinkage? dynamic instability
What drug commonly used in experiment binds to tubulin and inhibit microtubule polymerization which in turn blocks mitosis? Colchicine
What drugs is used in cancer chemotherapy because they selectively inhibit rapidly dividing cells? vincristine and vinblastine
What useful drug stabilizes microtubules rather than inhibiting their assembly? taxol
What are the single large cells formed by the fusion of many individual cells during development? muscle fiber
What are the cylindrical bundles of two types of filaments: thick filaments of myosin and thin filaments of actin? myofibril
What is a protein that interacts with actin as a molecular motor? myosin
What are each myofibril units organized as a chain of contractile units that are responsible for the striated appearance of skeletal and cardiac muscles? sacromeres
What is a protein that converts chemical energy in the form of ATP to mechanical energy, thus generating force and movement? molecular motor
What are two additional proteins that contribute to sacromere structure and stability? Which protein acts like a spring to keep myosin filaments in the center of the sacromere? titin and Nebulin, Titin
What is the sliding filament model for contraction of a muscle? the actin filaments slide past the myosin filaments toward the middle of the sacromere resulting in a shortening of the sacromere without any change in filament length
What is the structure of myosin ii? large protein consisting of two identical heavy chains, each heavy chain contains globular head region and a long alpha helical chain tail?
What energy drives the filament sliding? the myosin head binding and hydolyzing ATP
What is the cycle for contraction? Starts w/ M bound to a, ATP binds to M dissociating the A-M complex, ATP hydrolysis induces comformational change in m. M head rebinds to a new position on actin resulting in release of P triggering power stroke releasing ADP, m returns to initial confor
Where is calcium stored in the cell? in the ER or sacroplasmic reticulum
How does Ca2+ signal muscle contraction? by attaching to tropomyosin and troponin that changes conformation resulting in the uncovering the myosin binding site on actin
What is Tropomyosin and the different types of troponin? protein that binds lengthwise along actin filaments with low Ca it blocks myosin binding site, TnI-inhibitory, TnC- binds to Ca2+, and TnT- binds to tropomyosin
Describe the function of actin filaments and non-muscle myosins on contractile ring formation and function. Actin are integrated with myosin II which produce contraction sliding the plasma membrane progressively inward constricting the center and pinching the two cells in two by sliding the actin filaments forming a contractile ring until the cell divides
How is non-muscle myosin regulated? Through phosphorylation of of the regulatory light chain
What enzyme catalyzes the regulatory light chain? myosin light chain kinase
What is the structure of myosin i? contains a head group, but it has a comparatively short tail and does not form a dimer or filament
What are some functions of myosin i? moves vesicles, cargo, plasma membrane and organelles to the barbed end of actin filaments
Where do microtubules extend outward from which is located adjacent to the nucleus near the center of interphase, during mitosis this duplicates and separate to form the mitotic spindle? centrosome
What are cylindrical ctructures based on nine triplets of microtubules, that are necessary to form basal bodies, cilia and flagella? centrioles
What happens when the centrioles are removed form animal cells? results id despersion of centrosomes contents and a decline in microbulue production
What type of microtubules attaches to the condensed chromosomesof mitotic cells at their centromeres which are associated with kinetichores? kinetochore microtubules
Which type of microtubule also emanates from the centrosomes that connect to the ends of the chromosome via chromokinesin? chromosomal microtubules
What type of microtubule found in the mitotic spindle does not attach to chromosomes instead they are stabilized by over lapping with each other in the center of the cell? polar microtubules
What type of microtubule extends outward from the centrosomes to the cell periphery and have freely exposed plus ends? Astral microtubles
What is the chromosomal movement towards the spindle poles along the knietochore microtubules, this movement is driven by minus-end -directed motor proteins associated with the kinetichore resulting in the deattachment and shortening of kintechore and mt? Anaphase A
What is the separation of spindle poles resulting from two movements 1 the overlapping of PMs slide past each other to push spindle pole apart, 2 spindle poles are pulled apart due to the driving force of the minus-end -directed motor anchored to cortex? Anaphase B
how are microtubules arranged in dendrites? axons? -oriented in both directions plus ends pointed toward and away from the cell - oriented with their plus ends pointing toward the tip of the axon
What protein stabilizes microtubules by capping their ends? Microtubules-associated proteins (MAPS)
What does stable microtubules determine in nerve cells polarity and
What protein stabilizes microtubules and its mutation has lead to Alzheimers? tau
What re motor proteins that move along microtubules toward the plus end? Kinesins
What are motor proteins that move along microtubules toward the minus end? Dyneins
What are microtubule-based projections that are responsible for movement of a variety of eukaryotic cells? Cilian and Flagella
What is the fundamental structure of both cilia and flagella and is composed of microtubules and their associated proteins? axoneme
How are microtubules in cilia and flagella arranged? 9+2 pattern
What protein links microtubule doublets to each other in the axoneme? nexin
What is a structure similar to a centriole that initiates the growth of axonemal microtubules and contains 9 triplets of microtubules? basal body
Two arms of what are attached to each A tubule and its motor activity drives he beating of cilia and flagella? dynein
Describe how dynein dynamics leads to flagellar and ciliary movement. Movement results from sliding of outer m doublet relative to 1 another, by dynein bases that bind to A tubules while head binds to B tubulin of adjacent, dyenin head moves toward minus-end-direction then causes A to slide toward basal B, doublet bends
Why is cell-cell communication important in multicellular organisms? Cell-cell contact can stimulate differentiation, enable migration and tissue formation, arrest cell division etc…
Which signaling involves the release of secreted molecules that act upon distant sites? endocrine eignaling
Which signaling involves secreted molecules that act upon nearby target cells? Paracrine signals
Which signaling occurs when cells respond to signals they-themselves produce? Autocrine signaling
What is an example of autocrine signaling? T-cell amplification in an immune response
What type of hormones act upon intracellular receptors? steroid hormones
Are steroids hydrophobic or hydrophilic signaling molecules? Hydrophobic
Describe steroid hormone signaling. Steroid hormones diffuse into the cell and bind their receptors which act as transcription factors
What typically occurs when these hormones bind to their receptors? the receptors are transcription factors that can activate or repress genes
How does nitric oxide (NO) stimulate the relaxation of smooth muscle cells that surround blood vessels? acetylcholine stims endothelial cells synthesize NO, NO diffuses into neighboring cell, activates guanylyl cyclase which stimulates synthesis of the second messenger cGMP which induces muscle cell relaxation lowing BP
How is NO synthesized? from amino acid arginine by the enzyme synthase
How does NO affect guanylyl cyclase? by binding to a heme group at the active site of the enzyme, stimulating synthesis of the second messenger cGMP
How is NO similar to estrogen? it can diffuse through the plasma membrane
What is a heterotrimeric G protein? proteins that consist of 3 subunits designated alpha, beta and gamma
How Does Glucocrticoid activat transcription? Diffuses into the cytoplasm Binds to its receptor and displaces Hsp90 Glucocorticoid receptor dimerizes Dimerized receptor moves into nucleus and binds histone acetyltransferase (HAT) and together activate transcription
What are the distinct binding sites for receptors of sterol hormoones? ligand binding, DNA binding and activation domains
Hundreds of genes can respond to hydrophobic hormones depending on... cell type, stage of development and disease state
NO action lead to what drug? Viagra
What are the other exterior cell binding types? ligands binding to cell surface, receptors transmitting signals to the interior (signal transduction), and specific responses such as enzyme control or gene expression
What type of process can a cell signaling be? amplifying
how does G protein-coupled receptors activate G proteins? hormone binds and stim the release of GDP and it is exchanged for GTP, activated GTP bound a dissociates from b&y and the receptor,
how does the G proteins can activate either adenylyl cyclase or phospholipase C? The activated G protein subunit alpha stimulates adenylyl cyclases which catalyzes the conversion of ATP to cAMP
how does heterotrimeric G protein become inactive? By hydrolysis of GTP
Describe the cAMP pathway? ligand binds to seven membrane protein, activating G-protein, activates adenylyl cyclase, that producess cAMP,
Describe the formation of diacylglycerol? 7-transmembrane activated by a ligand, activates G-proteins, phospholipase C,which cuts off the polar head that forms Diacylglycerolwhich activats Protein kinase C and IP3 which mobilizes Calcium
What does Ca2+ do in cell signaling? acts with Calmodulin to aactivate kinases
What is an enzyme-linked receptor? Receptors that are directly linked to intracellular kinase
What enzyme converts sGMP to GMP? cGMP phosphodiesterase
how do receptor protein-tyrosine kinases activate MAP kinase (ERK) ligand binds to RTK causing them to dimerize which results in them Ping each other, adaptor protein binds to P-tyrosine, SOS binds to adaptor, and activates Ras that then activates kinase Raf uses ATP to Activate AEK to activate ERK
What are the affects of ERK? proliferation, differentiation and cell survival, modulate gene expression
Describe the PI 3-kinase/Akt pathway. PI 3-kinase activated by g-protein or binding to RTK's, head is phosporylated, Akt binds to it, and is phosphorylated by PDK1 and mTOR/rictor complex
What does activated Akt regulate? cell survival, transcription, translation and metabolism
What is a docking site for the pleckstrin homology domain of Akt, bringing Akt to the cell surface? PIP3
What are primary messengers? secondary messengers? ligands that bind to the initial receptor, any other messenger produced
What are the two causes of cancer? genetic mutation and infection w/ virus
What is an oncogene mutation? a cancerous gene that gains a function, dominant mutation, often transcribes signal transduction proteins
What are some examples of an oncogene mutation? RTK receptor permanently active due to dimerization, Ras loses ability to hydrolyze
What is a protooncogene? the normal form of an oncogene
What are tumor suppressor genes? genes that lose there function in cancer, recessive manor, often involves proteins that control cell cycle or dell death
Net effect when the number is even is? when odd? stimulates, inhibits
How do systems reset? Eliminate hormone Sometimes phosphorylate receptor Sometimes produce antagonist hormone GTP autohydrolysis by G protein cAMP phosphodiesterase Phosphatase counteracts PKA
Created by: sfitzpatrick