Explain how a cell synthesizes protein.



Protein synthesis vivaExplain how a cell synthesizes protein.DNA forms RNADoes so because DNA in nucleus of cell but most functions are carried out in cytoplasm, so forms intermediary RNAProcess called transcriptionRNA diffuses from nucleus through nuclear pores into cytoplasm, controls protein synthesisHow is RNA synthesized?2 strands of DNA molecule separate temporarily1 strand is used a templatecode triplets in DNA cause complementary code triples (codons) in RNA, that control the sequence of amino acids in proteinthese codons control the sequence of amino acids in protein to be synthesized What is RNA polymerase?RNA polymerase ‘activates’ RNA nucleotides – creates high energy phosphate bonds from ATPAssembly of RNA moleculePromotor: DNA strand immediately ahead of the initial gene. It is a sequence of nucleotides the RNA polymerase can recognize and attach to. Essential step for initiating formation of RNA moleculeRNA polymerase attaches – unwinds & separates DNARNA breaks and forms bonds to grow RNA chainWhen at end of DNA gene, encounters chain-terminating sequence, causing polymerase and newly formed RNA chain to break away, polymerase then recycled, RNA chain leaves nucleusWhat is the role of mRNA, tRNAMessenger RNA (mRNA) – carries the genetic does to the cytoplasm for controlling the type of protein formed.Transfer RNA (tRNA) – transports activated amino acids to the ribosomes to be used in assembling the protein molecule.Ribosomal RNA – forms ribosomes, the physical and chemical structures on which protein molecules are actually assembled. How is it regulated?Genetic regulationoperon of cell: area of DNA strand called an operonrepressor proteins: bind to middle of promotor region to prevent attachment of RNA polymerase.Activator protein: operator lies adjacent by ahead of promotor, attracts RNA polymeraseRegulatory genes control the operonsEnzyme regulationenzyme inhibition: feedback loopsenzyme activation: normally inactive enzymes become activated when neededmay be influenced from second messengers, intracellular receptors eg hormone receptorsreceptor-hormone diffuses into nucleus, combination binds specific points on DNA, activates transcription processEg via protein kinasesWhat is post translational modificationafter the polypeptide chain is formed, it ‘folds’ into its biological form and can be further modified to the final protein by one or more of a combination of reactions that include:hydroxylation, carboxylation, glycosylation, phosphorylation or amino acid residues, cleavage of peptide bonds, further folding/packagingWhat is a gene?a nucleic aicd called deoxycribnucelic acid (DNA) which controls the formaltion of ribonucleic acid (RNA) then spreads throughout the cell to control the formation of a specific protein. In cell nucleus, large numbers of genes are attached end on end in long double-stranded helical molecules of DNAComponents: phosphoric acid, sugar called deoxyribose, 4 nitrogenous gases (2 purines, adenine and guanine, and 2 pyrimidines, thymine and cytosine)What is genetic polymorphism?genetic variation that results in different phenotypic expression within the one species. ................
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