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Cell bio exam 2| 162 questions| with
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What are the primary functions of the 5' cap and poly A tail? correct answer Increase the stability of the mRNA;Facilitate mRNA export from the nucleus to the cytoplasm; What are nuclear pore complexes (NPCs) and what do they do? correct answer provide access to the nucleus and regulate the transport of proteins and RNA across the nuclear envelope. What is required for an mRNA to be considered export ready? correct answer must be bound to a specific set of proteins: Poly-A-Binding Proteins, A cap-binding complex, proteins that mark completed RNA splices, nuclear transport receptor Why is translation not a direct one to one correspondence between a single nucleotide on the mRNA and single amino acid in a protein? correct answer there are only 4 different nucleotides in mRNA and 20 different types of amino acids in a protein How many consecutive nucleotides in an in an mRNA make up a codon? correct answer three How is the genetic code redundant? correct answer some amino acids are specified by more than one codon How many codons specify one amino acid? correct answer 64 codons for 20 amino acids What role do transfer RNAs play in translation? correct answer molecular adaptors that match amino acids with codons How do tRNAs function as adaptor molecules? correct answer they recognize and bind codon at one site on their surface and to the amino acid on the other site what is an anticodon? correct answer a set of three consecutive nucleotides that pair with the complementary codon in an mRNA molecule how do aminoacyl-tRNA synthetases couple tRNAs to the correct amino acid? correct answer different synthetase enzyme for each amino acid. Enzyme attaches amino acid to 3' end on tRNA. Step 1: Amino acid is activated through linkage of carboxyl group to AMP Step 2: AMP-linked carboxyl group on amino acid is transferred to hydroxyl group on sugar at 3' end of tRNA molecule
What role do ribosomes (rRNA) play in translation? correct answer responsible for reading the order of amino acids and linking amino acids together Where are ribosomes located within the cell? correct answer They are made in the cytoplasm, then transported to the nucleolus to assemble the large and small ribosomal subunits, then the 2 subunits move back to cytosol via nuclear pores Free ribosome correct answer Free in cytosol Bound ribosome correct answer attached to membranes of endoplasmic reticulum Do ribosomes possess catalytic activity? What is the name of an enzyme that catalyzes the formation of a peptide bond? correct answer Yes. Peptidyl transferase (contained within the large subunit) Where are ribosomes synthesized? correct answer Synthesized in cytosol, then transported to nucleus to create small and large subunit Small subunit of ribosome correct answer binds mRNA and matches the tRNAs to the codons of the mRNA Large subunit of ribosome correct answer Catalyzes formation of peptide bonds that link amino acids together in polypeptide chain What is the mRNA-binding site? correct answer one binding site. What is the A Site? correct answer where the new incoming tRNA bind to mRNA What is the P Site? correct answer where the amino acids on the tRNA make a peptide bond with the amino acids on the rRNA at the A site forming a long amino acid chain What is the E Site? correct answer the tRNA that just gave up its amino acid, now empty, exit the ribosome to go restock their amino acid. What end of the growing polypeptide chain are amino acids added to? correct answer C- Terminal What is the initiator tRNA and what amino acid does it carry? correct answer Starts translation, carries the amino acid Met. What codon does the translation of an mRNA begin with? correct answer AUG What site on the small ribosomal subunit does the initiator tRNA bind? correct answer P-site How is the end of the protein-coding message signaled? What are the release
what are the primary functions of sphingolipids? correct answer important roles in signal transmission, cell recognition, cell surface protection how are sphingolipds different from other phospholipids? correct answer they are derived from sphingosine and not glycerol like other phospholipids. Usually found in neural tissues what kinds of tissues are sphingolipids primarily found in? correct answer neural tissues, brain tissue extracts what is sphinogomyelin and where is it found? correct answer a type of sphinogolipid found in animal membranes what is tay-sachs disease? correct answer genetic disorder caused by insufficient activity of enzyme that breaks down sphingolipids. Sphingolipids then build up and destroy brain and nerve function what is the basic structure of a glycolipid correct answer glycolipids (glycosylated lipids) are derivatives of phospholipids that contain a carbohydrate head group. this carbohydrate head group may contain anywhere from one to six sugars what are the primary functions of glycolipids? correct answer protection- strengthen and protect the plasma membrane cell recognition- attacks pathogen, organ/graft compatibility, blood transfusion, embryonic development how are glycolipids different from other phospholipids or sphingolipids? correct answer they contain a carbohydrate head group what is the primary type of (oligo)glycolipid found in most animal cells? correct answer sphingoglycolipid which surface of plasma membrane are the carbohydrates found on? correct answer extracellular surface which organelle is primarily responsible for glycosylating glycolipids? correct answer sugars are added to the membrane in the Golgi bodies what is the basic structure of a sterol correct answer carbon skeleton made of four linked rings, hydrophobic tail, and small hydrophilic head group. they are hydrogens bound to phospholipids what are the primary functions of sterols? correct answer cell membrane structure, affects fluidity and helps in signaling what is the primary sterol found in animal cells and what membrane is it found in? correct answer cholesterol, it is found in plasma membrane
how do sterols affect membrane fluidity? correct answer they act as a dynamic glue. More sterol=less fluid membrane what are liposomes and micelles and why are they important? correct answer they are essential for the absorption of fat-soluble vitamins and complicated lipids. this is used in targeted drug therapy why are membranes manufactured asymmetrically in the smooth ER? correct answer enzyme inserts new phospholipids into cytosolic monolayer. what type of enzymes insert new phospholipids into the cytosolic monolayer? correct answer phospholipid syntheses what are phospholipid translocators? correct answer flip phospholipids understand how membrane orientation is maintained during vesicular trafficking correct answer cytosolic surface is always cytosolic surface and luminal surface is always extracellular surface. two leaflets make up one unit membrane. different surfaces of the membrane have different types of phospholipids, glycolipids, and proteins what are lipid rafts and what are their characteristics and functions? correct answer localized regions of plasma membrane where there are elevated levels of cholesterol, protein, and sphingolipids. sphingolipids and cholesterol self assemble to form lipid rafts, they are basic building blocks). lipid rafters are more ordered and tightly packed that the surrounding bilayer and can float freely. lipid rafts are ticker and more viscus. they serve as organizing centers for assembly of signaling molecules-influenceing membrane fluidity and membrane protein movement. in what ways can proteins associate with a membrane? correct answer transporters, anchors, receptors, and enzymes. most membrane functions are carried out by proteins describe the different types of integral membrane proteins correct answer integral membrane proteins are proteins directly associated with the membrane what are transmembrane proteins? correct answer single pass, multipass, amphipathetic, hydrophobic region of interior membrane.
- single pass- polypeptide chain cross bilayer as an alpha helix
- multipass-transmembrane alpha helix with an aqueous pore how does the amphipathic nature of transmembrane proteins allow them to span? correct answer hydrophobic interior region by hydrophilic exterior region on the sides of the membrane what are membrane-associated proteins? correct answer associatd with the cytosolic surface of the membrane via the amphipathetic alphahelix embedded in monolayer
how can the lateral movement of proteins in the plasma membrane be restricted? correct answer protein protein interaction, proteins teathered to ECM molecules outside of the cell, proteins tethered to cell cortex inside the cell, proteins tethered to other proteins in adjacent cell describe the three most important aspects of lipid composition that affect membrane fluidity and understand the underlying reasons for each. correct answer 1. length of fatty acid tails: shorter tails= more fluid membrane (van der waals force interactions). longer chain=more stable
- degree of saturation of fatty acid tails: unsaturated faty acid tails hinder close packing, thus increasing fluidity. saturated fatty acids makes for close packing, making the membrane more stable and less fluid
- sterol content: sterols decrease fluidity as temp increases becuase phospholipid movement is restrained. at low temp, sterolss increase fluidity because the phospholipids are prevented from packing close what is membrane transport? correct answer the ability to move ions and molecules across membrnes seletivly how do selectivly permeable membranes regulate molecular traffic? correct answer characteristics of materials being transported, membrane solubility charachteristics, presence of specific transmembrane transport prtoeins what is simple diffusion? how does the hydrophobic interior of the membrane affect simple diffusion? correct answer direct, unaided net movement of molecules into and through the lipid bilayer in the direction dictated by the concentrations of the solute on the two sides of the membrane what kinds of molecules can undergo simple diffusion and which cannot? correct answer small, uncharged, nonpolar (hydrophobic) molecues can go through via simple diffusion (gases and steroid-based hormones). the smaller the molecule and the less strongly its association with water, the more rapidly it will diffuse across a bilayer. hydrophobic interior creates a barrior to most hydrophillic molecules and ions. ions are lectrically attracted to water what are the different gradients that are involved with transport across a membrane? correct answer concentration and elctrochemical gradient what two gradients drive simple diffusion and passive/facilitated transport? correct answer concentration and electrochemical gradient explain how charged and uncharged molecules are affected by the gradients correct answer For charged molecules and ions, the difference in electrical potential across a membrane is an additonal force that drives movement across a membrane. most cell membranse have a voltage across them (electrical potential, sytosolic side is usually negative) what is electrochemical graident? how does electrochemical gradient affect passive transport? correct answer electrochemical gradient is gradient of electrochemical potential an ion can move
across a membrane. chemcial gradient=difference in solute concentration across a memrane and electrical gradient (difference in charge across a membrane) How is the electrochemical gradient involved in coupled transport? correct answer coupled transporters transport two different solutes simultaneously or sequencentially by coupling the uphill transport of one solute across the membrane (passive transport) to the downhill transport of another (active transport=needs energy) what types of membrane transport require transporters or channel proteins? correct answer passive (facilitated transport) and active transport understand passive (facilitated) transport. what are uniports and what kinds of membrane transport are they used for? correct answer uniports transport a single solute across the membrane passively down concentration or electrocmehical transport what are the five types of transmembrane channel proteins and what type of transport do they mediate? correct answer channel proteins: passive transport mediated by the concentration or electricochemical gradient. the hydrophylic transmembrane channels alloow water soluble solutes to pass. 5 types are porins, aquaporins, gap junctions, plasmadesmata, and ion channels describe porins, aquaporins, and ion channels correct answer porins: beta barrel proteins found in outer membranes. they are large pores with low specificity aquaporins: fast movement of water, this is found in kidnesy ion channels: smallest porse size, selectivity involes pore size and distribution of charged amino acids in pore. the rate of transport what determines ion channel slectivity correct answer pore size and distribution of charged amino acids in pore where are most ion channels found? correct answer plasma membranes are ion channels fast or slow? correct answer very fast different ways that ion channels can be gated? why stimuli regulates ion channels? correct answer voltage-gated: changes in electrical potential across a membrane ligand-gated: controlled by the binding of specific ligand (hormone, econdary messenger, ATP) mechanically-gated: open and close in response to mechanical forces that act on membrane voltage gated ion channels? correct answer changes in electrical potential across a membrane ligand gated ion channels correct answer controlled by the binding of specific ligand (hormone, econdary messenger, ATP) mechaincally gated ion channels correct answer stretch-activated (sound strikes auditory hair cells, vibrations stretch ion channels, ions follow into hair cells, electrical signal sent to brain and perceive as sound
what are examples of important activated carriers? what is the function of Nicotinaminde adenine dinucleotide correct answer (ATP, NADH, FADH2) explain oxidation/reductions reactiosn correct answer explain the two methods used by animal cells to make ATP and where do these events occur? correct answer 1. oxidation reactions of food molecules are directly coupled to the energetically unfavorble reaction of ATP synthesiss. this is produced during glycolysis
- ATP is generaged in reactins which use enrgy from the activated carrier NADH. this takes place in the mitochondrial membranes what is substrate-level phosphorylation? what is oxidative phosphorylation? correct answer substrate-level: oxidation of food molecules directly coupled to atp synthesis oxidative-level: atp generaged in reactions using enrgy from NADH, takes place in mitochondrial membranes what are the three stages of cellular metabolism/ correct answer 1. glycolysis: partial oxidation of glucose and production of ATP int eh absence of oxygen define glycolysis. is o2 involved? is co2 released? by what method is ATP produced during glycolysis? what happens during steps 6 and 7 of glycolysis and why these steps are the central reactions of glycolysis? what are the end products of glycolysis? what are the energy requirements and energy yields of glycolysis? why is glucose phosphorylated during the energy investment phase of glycolysis? correct answer glycolyysis is partial oxidation of glucose and producion of ATP in the absense of oxygen (anaerobic reactions). net gain of 2 ATP molecules and 2 NADH molecules for every molecule of glucose broken down. ATP investementis 2 molecules of ATP are initally consumed in first three reactions to provide energy neeed to drive the reaction. steps 6-7 are the energy-generation phase, aldehyde is converted int a carboxylic acid. this reaction releases enough free energy to syntehsiE a molecule from ADP+Pi. no molecular oxygen is involved but oxidation occurs becuase 2 hydrogen atoms are removed 2 ATP and 2 NADH step 6: energy released during C-H bond oxidation drives formation of high-energy phosphate bond step 7: hydrolysis drives ATP formation structure and function of mitochondira. important charachteristics of inner and outer mitochonrial membrane correct answer mitochondria contains enzymes required for he oxidation of pyruvate and fatty acids to acetyl-coA and enzymes for citric acid cycle, channel forming protein called porin. outer membrane: has many copies of porin, which forms wide aqueous channels through a lipid bilayer, which makes the intermembrane space of mitochondria chemcialy equivalent to the cytosol inner membrane: impermeable to the passage of ions and small molecules.
what is the intermembrane spaces? correct answer where is the mitochondrial matrex correct answer where does the reaction of conversion of pyruvate ito acetyl coA take place? what enzyme catalyzes this reacction correct answer mitochondrial matrix, and the enzyme is pyruvate dehydrogenase complex describe process of citric acid cycle correct answer 1. acetyl coA starts common pathway for degradation of 2-carbon acetyl residues. Generates NAdh by oxidizing acetyl coA to Co who is hans aldof krebs correct answer discovered citric acid cycl, noble prize in physiology and medicine in 1953 which part of mitochondria does citirc acid cycle occur correct answer matrix what is the begining substrate? what is role of O2? why doe the cycle depend on molecular oxygen? correct answer beginging substrate is acetyl coA, which is then converted ito co citric cycle does not use oxygen correct answer it requies oxygen to procceed becuase oxygen is a lectron acceptor what is generated GTP used for? what is end product of ciric acid cycle? correct answer 3 NADH, 1 FADH2, 1GTP, and releases 2 moecules of CO2. GTP exchanges phosphate group with ADP to form ATP because ATP is not directly formed int eh citric acid sycle difference between substrate-level phosphoryoation and oxidative phosphorylation. stages of oxidative phosphorylation correct answer oxidatie phosphorylation: process of ATP synthesis involves consumption of o sage 1: energy of electron transport is used to pump protons across membrane stage 2: energy in proton gradient is harndessed by atp synthase to make atp what is chemosmotic theory correct answer created by peter d. mitchell. biological energy transfer requirements for chemiosmotic coupling in mitochondria? correct answer inner mitochondrial membrane, high energy electrions (NADH and FADH2) two sets of prtoein complexes embedded in membrane (transferes electrons, pumps protons and syntehsizes ATP), protns to generage a H+ gradient where in the mitochondria different steps of oxidative phosphorylation are occuring correct answer inner membrae
copper atoms in cytosome C oxidase complex what is the enregy from the electron transport chain used to do? correct answer stepwise movement of high-energy electrons correct answer where are the protons that are pumped fromteh inner mitochondrial membrane come from? correct answer water is a reservior of h+ difference between electrochemical gradient and electron motive force correct answer electrochemical proton gradient is used to drive formation of ATP and transport of selected metabolites across inner mitochondrial membrane what is ph in mitochondrial maattrix andinnermembrane space? correct answer ph is higher in the matrix compared to intermembrane what is ATP syntahse and its function? correct answer an enzyme that creates a hydrophilic pathway across the inner mitochondrial membrane that allows protons to flow down their electrochemical gradient what are names of fat cells that can oxidize food molecules? what is name of process and underlying mechnism correct answer brown fat cells. innermembrane of brown fat cells contain special transport protein that moves protons down electrochemcial graident. endosymbiont therory correct answer emdosymboisis of cyanobacterium gave rise to chloroplast and photosynthetic eucaryoic cells what are the activated carriers created by chloroplasts? correct answer NADPH-high energy hydrogen and electron donor and ATP where do the sugars synthesized by the chloroplasts go? correct answer exported to the cytosol for production of cellular ATP, starch, and other metabolities structure of chloroplats stroma, inner/outer membranes, thylakoids, grana, thylakoid space correct answer outer membrane is hgihly permeabe and inner membranes (thylakoid) is barely permeable what is analogus between chloroplasts and mitochondria correct answer inernal membrane is thylakoid in chloroplast, cristae in mitochondria matrix (mitochondria) is stroma (chloroplast) pHs associated with different areas of chloroplast correct answer intermembrane space= low pH matrix= high pH
which membrane is H+ gradient set up and used to produce ATP correct answer thylakoid membrane which area is ATP produced? correct answer stroma what occurs during light reactions? correct answer photosynthetic electron-transfer reactions in thylakoid membrane. chlorophyll obtains electrons from water, and generates o2 via water splitting enzyme. electron flow pumps H+ across thylakoid membrane from stroma into thlakoid space. this creates an electrochemical proton gradient across the thylakoid membrane and the proton gradient is used to produce ATP in the stroma. high energy electrons reduce NADP+ to NADPH in stroma define photosystem and describe basic structure correct answer large, multi-protein complex. the antenna and photochemical reaction center define antenna complex correct answer cluster of chlorophyl and accessory pigments (carotenoids) molecules that absorb light energy and pass virtual photons to photochemical reaction center via FRET what is caroenoid correct answer accessory pigments that serve to protect chlorophyll what is photochemical reaction center? correct answer FRET and how it relates to photosystems correct answer mechanism of energy transfer between two ight sensitive molecules (chromophores). donor transfer energy to acceptor flow path of electrsons through electron transport chain embedded in thylakoid membrane correct answer non-cyclic and cyclic photosynthesis correct answer non-cyclic photosynthesis is a 2 stage process forming ATP and NADPH. this is found in plants, cynanobacteria and algae cyclic photosynthesis: shut of PSII, allowing the production of ATP only using PS I. organism that has no need for reductive power in NADPH to fix power but still needs ATP what occurs during dark reactions? correct answer carbon-fixation reactions. ATP adn NADPH from light reactions are used as energy source (activted carriers) to convert CO2 into carbohydrate (carbon fixation). this occurs in stroma with formation of glyceradlehyde 3- phosphate, which is then transported to the cytosol
