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Biochemistry Flashcards

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4906061037amino acidhave 4 groups attached to a central carbon - amino group - carboxylic acid group - a hydrogen atom - R group0
4906061038Stereochemistry for amino acidsat the alpha carbon the stereochemistry is always L in eukaryotes. D-amino acids can exist in prokaryotes. All amino acids except cysteine have S configuration. Glycine is the only amino acid that is not chiral.1
4906061039nonpolar, nonaromatic side chainglycine, alanine, valine, leucine, isoleucine, methionine, proline2
4906061040aromatic side chaintryptophan, phenylalanine, tyrosine3
4906061041polar side chainserine, threonine, asparagine, glutamine, cystine4
4906061042negatively charged side chain (acidic)asparatate, glutamate5
4906061043positively charged side chain (basic)lysine, arginine, histidine6
4906061044amphotericcan accept or donate protons7
4906061045pKais the pH at which half of the species is deprotonated [HA] = [A-]8
4906061046Amino acids at different pH valueslow pH = fully protonated pH near the pI = neutral zwitterion high pH = fully deprotonated9
4906061047isoelectric pointcan be calculated by averaging the two pKa values of the amino acids without a charged side chain10
4906061048titration of an amino acidthe curve will be nearly flat at the pKa values of the amino acid and nearly vertical at the pI of the amino acid11
4906061049pI of amino acidsAcidic amino acids have a pI well below 6 Basic amino acids have a pI well above 6 Amino acids without charged side chains have a pI around 612
4906061050formation of a peptide bondoccurs via a condensation or dehydration reaction. The nucleophilic amino group of one amino acid attacks the electrophilic carbonyl group of another amino acid. *Note that amino bonds are rigid because of resonance.13
4906061051breaking of a peptide bondoccurs via hydrolysis. In the body: trypsin -> cleaves at the carboxyl end of arginine and lysine. Chymotrypsin -> cleaves at the carboxyl end of phenylalanine, tryptophan, and tyrosine. Organic chemistry: hydrolyzes the amide bond using acid or base catalysis14
4906061052primary structureis the linear sequence of amino acids in a peptide and is stabilized by peptide bonds15
4906061053secondary structureis the local structure of neighboring amino acids and is stabilized by hydrogen bonding between amino acid groups and non adjacent carboxyl groups16
4906061054alpha helixare clockwise coils around a central axis17
4906061055beta pleated sheetsare rippled strands that can be parallel or antiparallel18
4906061056prolinecan interrupt secondary structure because its rigid cyclic structures19
4906061057tertiary structureis the three-dimensional shape of a single polypeptide chain, and is stabilized by hydrophobic interactions, acid-base interactions, hydrogen bonding, and disulfide bonds20
4906061058hydrophobic interactionspush hydrophobic R groups to the interior side of a protein which increased entropy of the surrounding water molecules and creates negative Gibbs free energy21
4906061059disulfide bondsoccur when two cysteine molecules are oxidized and create a covalent bond to form cystine22
4906061060quaternary structureis the interaction between peptides in proteins that contain multiple subunits23
4906061061denaturation of proteinscan occur through heat and increasing solute concentration which lead to loss of three-dimensional protein structure24
4906061062isoelectric point of a neutral amino acidpI = pKa NH+ group + pKa COOH group / 225
4906061063Isoelectric point of an acidic amino acidpI = pKa R group + pKa COOH group / 226
4906061064isoelectric point of basic amino acidpI = pKa NH+ group + pKa R group / 227
4906061065enzymesare biological catalysts that are unchanged by the reactions they catalyze and are reusable.28
4906061066Key features of enzymeslower activation energy increase the rate of reaction do not alter the equilibrium constant are not changed or consumed in the reaction are pH and temperature- sensitive, with optimal activity at specific pH ranges and temperatures do not affect the overall delta G of the reaction are specific for a particular reaction or class of reaction29
4906061067oxidoreductasecatalyze oxidation-reduction reactions that involve the transfer of electrons30
4906061068transferasesmove a functional group from one molecule to another molecule31
4906061069hydrolasescatalyze clevage with the addition of water32
4906061070lyasescatalyze cleavage without the addition of water and without the transfer of electrons. The reverse reaction (synthesis) is often more important biologically.33
4906061071isomerasescatalyze the interconversion of isomers, including both constitutional isomers and stereoisomers34
4906061072ligasesare responsible for joining two large biomolecules , often of the same type35
4906061073Mnemonic for Major Enzyme ClassificationsLI'L HOT36
4906061074exergonic reactionsrelease energy; delta G is negative37
4906061075mechanism of enzymesThey do not alter the free energy or enthalpy change that accompanies the reaction nor the final equilibrium position. It does however change the rate (kinetics) at which equilibrium is reached. They act by stabilizing the transition state, providing a favorable miroenvironment, or bonding with the substrate molecules.38
4906061076lock and key theoryhypothesizes that the enzyme and substrate are exactly complementary39
4906061077induced fit modelhypothesizes that the enzyme and substrate under go a conformational change to interact fully40
4906061078substrate kineticsas a substrate concentration increases the reaction rate does as well until a maximum value is reached41
4906061079Michaelis- Menten rate42
4906061080Michaelis-Menten equation43
4906061081Michaelis-Menten plot44
4906061082Lineweaver-Burk plot45
4906061083cooperative enzymesdisplay a sigmoidal curve because of the changes in activity with substrate binding46
4906061084feedback inhibitionis a regulatory mechanism whereby the catalytic activity of an enzyme is inhibited by the presence of high levels of a product later in the same pathway47
4906061085reversible inhibitionis characterized by the ability to replace the inhibitor with a compound of greater affinity or to remove it using mild laboratory treatment48
4906061086competitive inhibitionresults when the inhibitor is similar to the substrate and bind at the active site. This can be over come by adding more substrate. Vmax is unchanged and Km increases49
4906061087noncompetitive inhibitionresults when the inhibitor binds to an allosteric site instead of the active side which induces a change in enzyme conformation. Vmax is decreased and Km is unchanged.50
4906061088mixed inhibitionresults when the inhibitor binds with unequal affinity to the enzyme and the enzyme-substrate complex. Vmax is decreases and Km is increased or decreased depending on if the inhibitor has a higher affinity for the enzyme or enzyme-substrate complex.51
4906061089uncompetitive inhibitionresults when the inhibitory binds only with the enzyme substrate complex. Km and Vmax both decrease.52
4906061090irreversible inhibitionalters the enzyme in such a way that the active site is unavailable for a prolonged duration or permanently. New enzyme molecules must be synthesized for the reaction to occur again53
4906061091allosteric sitescan be occupied by activators which increase either affinity or enzymatic turnover54
4906061092Phosphorylation and glycosylationcan alter the activity or selectivity of enzymes55
4906061093zymogensare secreted in inactive form and are activated by cleavage56
4906061094structural proteinscompose the cytoskeleton , anchoring proteins, and much of the extracellular matrix57
4906061095Most common structural proteinscollagen, elastin, keratin, actin, and tubulin58
4906061096collagenthee alpha helices woven together and make up most of the extracellular matrix of connective tissue. It provides strength and flexibility59
4906061097elastinfound in the extracellular matrix of connective tissue and primarily functions to stretch and recoil.60
4906061098keratinare intermediate filament protein found in epithelial cells. They provide mechanical integrity of the cell and function as regulatory proteins. Ex: hair and nails61
4906061099actinmakes up microfilaments and the thin filaments in myofibrils. It is the most abundant protein in eukaryotic cells. It contains a positive and negative end which allows motor proteins to travel along it.62
4906061100tubulinmakes up microtubules. It provides structure, chromosome separation in mitosis, and intracellular transport with kinesin and dynein.63
4906061101motor proteinshave one or more heads capable of force generation through a conformational change. Ex: myosin, kinesin, and dynein64
4906061102myosinis the primary motor protein that interacts with actin. It is also found in the thick filament in a myofibril. Each subunit has a head and a neck. Movement at the neck is responsible for the power stroke of sarcomere contraction.65
4906061103kinesin and dyneinsare motor proteins associated with microtubules. They have two head, in which one remains attached to tubulin at all times. Kinesin brings vesicles to the positive end while dyneins go toward the negative end.66
4906061104Application of motor proteinsmuscle contraction, vesicle movement within cells, and cell motility.67
4906061105binding protiensbind specific substrate, either to sequester in the body or hold its concentration at a steady state68
4906061106Cell adhesion molecules (CAMs)are integral membrane proteins that allow cells to bind to other cells or surfaces.69
4906061107cadherinsare calcium dependent glycoproteins that hold similar cells together70
4906061108integrinshave two membrane-spanning chains and permit cells to adhere to proteins in the extracellular matrix. Some also have signaling capabilities71
4906061109selectinsallow cells to adhere to carbohydrates on the surface of other cells and are most commonly used in the immune system72
4906061110antibodiesalso called imunoglobulins are used by the immune system to target a specific antigen, which may be a protein on the surface of a pathogen or a toxin73
4906061111antibody structurecontains a constant region and a variable region which is responsible for antigen binding. It has two identical heavy chains and two identical light chins that are held together by disulfide linkages and noncovalent interactions.74
4906061112opsonizationmarking the pathogen for destruction by other white blood cells immediately75
4906061113agglutinationclumping together the antigen and antibody into a large insoluble protein complex that can be phagocytized and digested by macrophages76
4906061114ion channelscan be use for regulating ion flow into or out of a cell. There are three main types of channels 1) ungated channels are always open 2) voltage-gated channels are open within a range of membrane potentials 3) ligand-gated channels open in the presence of a specific binding substance, usually a hormone or neurotransmitter77
4906061115facilitated difusionis a type of passive transport that allows the diffusion of molecules down a concentration gradient through a pore in the membrane created by transmembrane proteins78
4906061116enzyme linked receptorsparticipate in cell signaling through extracellular ligand binding and initiation of second messenger cascades. They have three primary protein domains including the membrane-spanning domain, ligand-binding domain, and a catalytic domain.79
4906061117membrane spanning domainanchors the receptor in the cell membrane80
4906061118ligand binding domainis stimulated by the appropriate ligand and induces a conformational change that activates the catalytic domain81
4906061119G protein-coupled receptorshave a membrane-bound protein associated with a trimeric G protein. They also initiate second messenger systems82
4906061120Functions of heterotrimeric G proteinsGs: stimulates adenylate cyclase increasing levels of cAMP Gi: inhibits adenylate cyclase decreasing levels of cAMP Gq : activates phospholipase C which cleaves a phospholipid from the membrane to form PIP2. PIP2 is then cleaved into DAG and IP3; IP3 can open calcium channels in the ER to increase calcium levels in the cell83
4906061121How G protein-coupled receptors work1) ligand binding engages the G protein 2) GDP is replaces with GTP; the alpha subunit dissociates from the beta and gamma subunits 3) the activated alpha subunit alters the activity of adenylate cyclase or phospholipase C 4) GTP is dephosphorylated to GDP; the alpha subunit rebinds to the beta and gamma subunits84
4906061122electrophoresisuses a gel matrix to observe the migration of proteins in response to an electric field85
4906061123native PAGEmaintains the protein's shape, but results are difficult to compare because the mass-to-charge ration differs for each protein. Most useful to compare the molecular size or the charge of proteins known to be similar in size86
4906061124SDS-PAGEdenatures the proteins and masks the native charge so that comparison of size is more accurate, but the functional protein cannot be recaptured from the gel87
4906061125isoelectric focusingseparates proteins by their isoelectric point; the protein migrates toward an electrode until it reaches a region of the gel where pH = pI of the protein88
4906061126chromatographyseparates protein mixtures on the basis of affinity for a stationary phase or a mobile phase89
4906061127column chromatographyuses beads of a polar compound, like silica or alumina (stationary phase), with nonpolar solvent (mobile phase)90
4906061128ion-exchange chromatographyuses a charged column and a variably saline eluent91
4906061129size-exclusion chromatographyrelies on porous beads. Larger molecules elute first because they are not trapped in the small pores92
4906061130affinity chromatographyuses a bound receptor or ligand and an eluent with free ligand or a receptor for the protein of interest93
4906061131X-ray crystallographyis used primarily to determine protein structure after a protein is isolated. NMR can also be used but this is less common94
4906061132Edman degradationis used to determine amino acid sequencing. Amino acid composition can be determined by simple hydrolysis but this will not yield the order95
4906061133UV spectroscopycan be used to determine protein concentration96
4906061134Bradford protein assaythis is the most common method for testing protein concentration and uses a color change from brown-green to blue. This method is limited by the presence of detergent and excessive buffer. It is also less accurate when more than one protein is present.97
4906061135Migration velocityV = Ez/ f98
4906061136aldosessugars with aldehydes at their most oxidized group99
4906061137ketosessugars with ketones at their most oxidized group100
4906061138D sugarssugars with the highest-numbered chiral carbon with the -OH group on the right101
4906061139L sugarssugars with the highest-numbered chiral carbon with the -OH on the left102
4906061140Common monosaccarides103
4906061141StereoisomersCompounds that have the same Chemical formula but differ in spatial arrangement of their component atoms104
4906061142EnantiomersA stereoisomer that is non-identical, non-superimposable mirror images of each other105
4906061143diastereomersare non-superimposable configurations of molecules with similar connectivity. They differ at at least one chiral carbon106
4906061144epimersare a subtype of diasteromers that differ at exactly one chiral carbon107
4906061145anomersare a subtype of epimers that differ at the anomeric carbon108
4906061146anomeric carbonis the new chiral center formed in ring closure; it was the carbon containing the carbonyl in the straight-chain form.109
4906061147alpha anomershave the -OH on the anomeric carbon trans to the free -CH2OH group110
4906061148beta anomershave the -OH on the anomeric carbon cis to the free -CH2OH group111
4906061149Haworth projectionsprovide a good way to represent three dimensional structure112
4906061150mutarotationcyclic compounds shift from one anomeric form to another with the straight-chain form as an intermediate113
4906061151monosaccharidesare single carbohydrates units, with glucose as the most commonly observe monomer114
4906061152Tollen's or Benedict's reagentsare used to determine reducing sugars115
4906061153TautomerizationRefers to the rearrangement of bonds in a compound, usually by moving a hydrogen and forming a double bond116
4906061154deoxy sugarsare sugars with a -H replacing an -OH group117
4906061155Esterificationsugars can react with carboxylic acids and their derivatives to form esters118
4906061156phosphorylationa phosphate ester is formed by transferring a phosphate group from ATP one a sugar119
4906061157glycoside formationis the basis for building complex carbohydrates and requires the anomeric carbon to link to another sugar120
4906061158disaccharidesform as result of glycosidic bonding between two monosaccarides subunits.121
4906061159sucroseglucose- alpha- 1,2-fructose122
4906061160lactosegalactose- beta- 1,4 - glucose123
4906061161maltoseglucose- alpha- 1,4- glucose124
4906061162celluloseis the main structural component for plan cell walls and is a main source of fiber in the human diet125
4906061163starchesinclude amylose and amylopectin and function as a main energy storage form for plants126
4906061164glycogenfunctions as a main energy storage form for animals127
4906061165Phospholipidsare amphipathic and form the bilayer of biological membranes. They contain a hydrophilic head and hydrophobic tails. The saturation of the fatty acid tails determine the fluidity of the membrane128
4906061166glycerophospholipidsare phospholipids that contain a glycerol backbone129
4906061167sphingolipidsare phospholipids that contain a sphingosine or sphingoid backbone130
4906061168types of sphingolipids131
4906061169sphingomyelinsare the major class of sphingophospholipids and contain a phosphatidylcholine or phosphatidylethanolamine head group. They are a major component of the myelin sheath.132
4906061170glycosphingolipidsare attached to sugar moieties instead of a phosphate group.133
4906061171gangliosidescontain oligosaccharides with at least one terminal N-acetylneuraminic acid134
4906061172Waxescontain long-chain fatty acids esterified to long-chain alcohols. They are used as protection against evaporation and parasites in plants and animals.135
4906061173Terpenesare odiferous steroid precursors made from isoprene, a five-carbon molecule (C5H8).136
4906061174Terpenoidsare derived from terpenes via oxygenation or backbone rearrangement.137
4906061175steroidscontain three cyclohexane rings and one cyclopentane ring. Their oxidation state and functional groups may vary.138
4906061176steroid hormoneshave high-affinity receptors, work at low concentrations, and affect gene expression and metabolism.139
4906061177cholesterolis a steroid important to membrane fluidity and stability; it serves as a precursor to a host of other molecules140
4906061178prostaglandinsare autocrine and paracrine hormones that regulate cAMP levels. they have powerful effects on muscle contraction, body temperature, they sleep-wake cycle, and pain. They are unsaturated carboxylic acids derived from arachidonic acid and contain one 5 carbon ring.141
4906061179vitamin Aalso called carotene is metabolized to retinal for vision and retinoic acid for gene expression in epithelial development.142
4906061180vitamin Dalso called cholecalciferol is metabolized to calcitriol in the kidney's and regulates calcium and phosphorus homeostasis in the intestine (increasing calcium and phosphate absorption), promoting bone formation . A deficiency of vitamin D causes rickets.143
4906061181vitamin Ealso called tocopherols and act as biological antioxidants. Their aromatic rings destroy free radicals, preventing oxidative damage.144
4906061182vitamine K(phylloquinone and menaquiones) is important for formation of prothrombin, a clotting factor. It performs post-translational modifications on a number of proteins, creating calcium-binding sites.145
4906061183triacylglycerolsare the preferred method of storing energy for long-term use. They contain one glycerol attached to three fatty acids by ester bonds and are very hydrophobic. The carbon atoms in lipids are more reduced than carbohydrates, giving twice as much energy per gram during oxidation.146
4906061184adipocytesare animal cells specifically used for the storage of large triacylglycerol deposts147
4906061185saponificationis the ester hydrolysis of triacyglycerols using a strong base, like sodium or potassium hydroxide148
4906061186micelleis a soap that act as surfactants that can dissolve a lipid-soluble molecule in its fatty acid core and washes away with water because of its shell of carboxylate head groups149
4906061187DNAis a macromolecule that stores genetic information in all living organisms150
4906061188Nucleosidescontain 5 carbon sugar bound to a nitrogenous base. Nucleotides are nucleosides with one to three phosphate groups added151
4906061189Nucleotidesadenosine (A), cytosine (C), guanine (G), thiamine (T), and uracil (U)152
4906061190Watson-Crick modelbackbone is comprised of alternating sugar phosphate groups and is always read 5' to 3' there are two strands with antiparallel polarity wound into a double helix purines (A and G) pain with pyrimidines (C, U, and T). A-T has two hydrogen bonds while G-C has three hydrogen bonds. In RNA A-U via two hydrogen bonds153
4906061191Chargaff's rulestate that purines and pyrimidines are equal in number in a DNA molecule and that because of base-pairing the amount of adenine equals the amount of thymine and so on154
4906061192Z-DNAcontains a zig-zag shape and is usually observed with high GC content or high salt concentrations.155
4906061193B-DNAis most common and forms a right handed helix156
4906061194Denaturation of DNAis caused by heat, alkaline pH, and chemicals like formaldehyde and urea. Removal of these conditions may cause reannealing of the DNA157
490606119546the number of chromosomes in human cells158
4906061196Organization of Eukaryotic ChromosomeDNA is wound around histone proteins to form nucleosomes. Together the DNA and histones make up chromatin which can be divided into heterochromatin (dense, silent DNA that is dark under light spectroscopy) and euchromatin (less dense, active DNA that is light under light spectroscopy). Telomeres are at the end of chromosomes and have a high G-C content to prevent unraveling. Centromeres are located in the middle of the chromosome and hold sister chromatids together until they are separated during anaphase in mitosis.159
4906061197replisomeis a set of specialized proteins that assist the DNA polymerase160
4906061198Helicaseshelp to unwind DNA at the origin of replication to produce two replication forks161
4906061199single stranded DNA binding proteinsprotect unwound strands of DNA from reannealing162
4906061200supercoilingcauses torsion strain on the DNA molecule which can be released by DNA topisomerase II (DNA gyrase) which creates nicks in the DNA163
4906061201Semiconservative replicationone old parent strand and one new daughter strand is incorporated into each of the two new DNA molecules164
4906061202Primaseinserts a small RNA primer to begin replication. Without and adjacent nucleotide DNA cannot be synthesized165
4906061203DNA polymerase III / DNA polymerase alpha and deltafor Prokaryotes and Eukaryotes respectively, aids in synthesizing a new strand of DNA. They read the template DNA 3' to 5' and synthesize the new strand 5' to 3'166
4906061204leading strandrequires only one primer and is synthesized continuously in its entirety167
4906061205lagging strandrequires many primers and is synthesized in discrete sections called Okazaki fragments168
4906061206DNA polymerase I / RNase Hfor prokaryotes and Eukaryotes respectively, aids in the removal of the RNA primers169
4906061207DNA ligasefuses DNA strands together to create one complete molecules170
4906061208DNA replication prokaryote vs eukaryote171
4906061209oncogenesdevelop from mutations of proto-oncogenes, and promote cell cycling. They may lead to cancer.172
4906061210cancerunchecked cell proliferation with the ability to spread by local invasion or metastasize173
4906061211Tumor repression genescode for proteins that reduce cell cycling or promote DNA repair; mutations of tumor suppressor genes can also lead to cancer174
4906061212Proofreadingduring replication DNA polymerase proofreads its work and excised incorrectly matched bases, the daughter strand is identified by its lack of methylation and corrected accordingly175
4906061213mismach repairoccurs during the G2 phase of cell cycle using the genes MSH2 and MLH1176
4906061214nucleotide excision repairfixes helix-deforming lesions of DNA (such as thymine dimers) via a cut-and-patch process that requires and excision endonuclease177
4906061215base excision repairfixes nondeforming lesion of the DNA helix (such a cytosine deamination) by removing the base, leaving an apurinic/apyrimidinic (AP) site. An AP endonuclease then removes the damaged sequence, which can be filled in wit the correct bases178
4906061216Recombinant DNAis DNA composed of nucleotides from two different sources179
4906061217DNA cloningintroduces a fragment of DNA into a vector plasmid. A restriction enzyme cuts both the plasmid and the fragment which are left with sticky ends. Once the fragment binds to the plasmid it can be introduced into a bacterial cell and permitted to replicate, generating many copies of the fragment of interest.180
4906061218DNA librairiesare large collections of known DNA sequences181
4906061219genomic librariescontain large fragments of DNA, including both coding and noncoding regions of the genome. They cannot be used to make recombinant proteins or for gene therapy182
4906061220cDNA librariescontain smaller fragments of DNA and only include the exons of genes expresses by the sample tissue. They can be used to make recombinant proteins or for gene therapy183
4906061221Genomic vs cDNA libraries184
4906061222hybridizationis the joining of complementary base pair sequencing.185
4906061223PCRis an automated process by which millions of copies of a DNA sequence can be created from a very small sample by hybridization186
4906061224agarose gel electrophoresismethod of separating DNA molecules by size187
4906061225southern blottingcan be used to detect the presence and quantity of various DNA strands in a sample. After electrophoresis, the sample is transferred to a membrane that can be probed with single-stranded DNA molecules to look for a sequence of interest188
4906061226DNA sequencinguses dideoxyribonucleotides with terminate the DNA chain because they lack a 3' -OH group. The resulting fragments can be separated by gel electrophoresis and the sequence can be read directly from the gel189
4906061227gene therapyis a method of curing genetic deficiencies by introducing a functional gene with a viral vector190
4906061228transgenic miceare created by integrating a gene of interest into the germ line or embryonic stem cells of a developing mouse. These mice can be mated to select for the transgene191
4906061229chimerasare organisms that contain cells form two different lineages (such as mice formed by integration of transgenic embryonic stem cells into a normal mouse blastocyst)192
4906061230knockout miceare created by deleting a gene of interest193
4906061231Central dogmaDNA -> RNA -> proteins194
4906061232Start codonAUG195
4906061233Stop codonUGA, UAA, UAG196
4906061234Redundancy/wobbleOccurring in the third-base of a codon allows mutations to occur without effects in the protein197
4906061235Silent mutationNo effect on protein synthesis198
4906061236Nonsense mutationAlso called truncation are mutations that produce a premature stop codon199
4906061237Misssense mutationProduces a codon that codes for a different amino acid200
4906061238Frameshift mutationResult from a nucleotide addition or deletion and change the reading frame of subsequent codons201
4906061239Structural differences between RNA and DNASubstitution of arrival sugar for deoxyribose Substitution of uracil for thymine Single-stranded instead of double-stranded202
4906061240mRNACarries the message from DNA in the nucleus via transcription of the gene; travels into the cytoplasm to be translated203
4906061241tRNABrings in amino acids, recognizes the codon on the mRNA using its anti-codon204
4906061242rRNAMakes up the ribosome; enzymatically active205
4906061243Helicase and topoisomeraseUnwind double stranded DNA206
4906061244RNA polymeraseBinds to the TATA box within the promoter region of the gene (25 base pairs upstream from the transcribed base)207
4906061245hnRNAIs synthesized from the DNA template (antisense) strand208
4906061246Post transcriptional modificationsA 7-methylguanylate triphosphate cap is added to the 5' end A poly-A tail is added to the 3' end Splicing is done by the snRNA and snRNP's in the splicosome. Introns are removed in a lariat structure and exons are ligated together209
4906061247Polycistronic genesA post translational modification that can increase variability of gene products by starting transcription in different sites within the gene leads to different gene products210
4906061248Alternative splicingA posy translational modification that can increase variability of gene products by combining different exonerated in a modular fashion to acquire different gene products211

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