BIO 130 Block 3 First Day of Notes
BIO 130 Block 3 First Day of Notes Bio 130, 15017
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Bio 130, 15017
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This 4 page Class Notes was uploaded by Bennett Notetaker on Monday March 14, 2016. The Class Notes belongs to Bio 130, 15017 at University at Buffalo taught by James Lafountain in Spring 2016. Since its upload, it has received 471 views.
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Date Created: 03/14/16
Bio Block 3 03/22/2016 ▯ (Notes for PowerPoint #9) ▯ Gene Expression: path from genetic coding to the gene product (how to get something from DNA) Protein Synthesis RNA Synthesis Mutations Genetic defects in metabolic enzymes ▯ Pathway for expressing a gene: Transcription of DNA occurs in the nucleus (conversion of code of DNA to RNA) Then, the translation of mRNA takes place within the cytoplasm (leads to making a protein called polypeptide) o Ribosomes can make any kind of protein o This process is also known as decoding o Protein synthesis happens during interphase, which is where growth and duplication of cell parts happens. Biosynthesis also happens at this time Go cells have to engage in synthesis in order to restore proteins that get drained out over time and create specific proteins for different process KEY IS THAT PROTEINS ARE THE GENE PRODUCTS DURING THIS STAGE AND ALL CELLS ARE NANO_SCALE PROTEIN FACTORIES The focus of this pathway of gene expression are the end products=proteins because they carry the second most percent of mass in a human cell following directly after water Protein folding: amino acid monomers are linked together by peptide bonds and folded into 3 dimensional shapes (function only occurs when protein folds properly) o What controls how a protein folds? The interaction of amino acid R groups The interaction between the polypeptide chain ant the physical/chemical properties of the microenvironment where it exists These interactions influence the 3 dimensional shape CYTOSOL: or intracellular fluid or cytoplasmic matrix is the liquid in a cell, it’s separated into different compartments by membranes (plasma membrane and organelle membranes). About 67% of the body’s water content is accounted for by the cytosol A peptide bond is the linkage of two amino acids through the loss of water and they react in a ribosome which creates a covalent bond aka a peptide bond Ribosomes: are the peptide bond makers of cytosol o Has large and small subunits o These subunits bind to mRNA o Ribosomes are RNP particles The mechanism of translation happens in a step-wise order that uses all elements of “translation machinery” o mRNA o Ribosome subunits o Amino-acylated tRNAS o Either (1)-completely in the cytosol or (2)-in association with endoplasmic reticulum (will be discussed more in later lectures maybe) What is an amino-acylated tRNA? t=Transfer RNA (20 different species) which helps incorporate amino acids to polypeptide chains tRNA is said to be charged when an amino acid is attached at OH. If it’s not attached it’s known as ‘uncharged’ Uncharging is linked to the formation of peptide bonds during translation The amino acid is linked to the stem of tRNA You start with codons and the anticodons are complementary to those codons (A to U and G to C) Linear sequence of amino acids o Incorporated into polypeptide which governed by the linear sequence of nucleotides in mRNA in which the ribosome translates o Specificity in translation is determined by GENETIC CODE, the 3 letter code words called codons that exist in the open reading frame of mRNA Genetic Code: the sequence of nucleotides that encodes the information for amino acids in a polypeptide chain o The set of 64 triplets of bases (codons)=DNA that correspond to the 20 amino acids in proteins and signals for initiation=RNA (1 codon) and termination (3 codons) of polypeptide synthesis o The 60 other code words are specific for an amino acid o UAA, UGA, and UAG are all STOP codons because ribosomes stop translating when they encounter a stop codon making these the terminal ends of mRNA Initiation complex o First small subunit o Then large subunit o Next mRNA o Finally met-tRNA which occupies the P site and A site which is unoccupied at initiation Elongation o val-tRNA binds by matching anticodon with GUG codon- moves into A site and peptide bond forms linking val 2 and 1 o di-peptide(met-val) is made when peptide bond is made o enzymatic activity of Ribosome catalyzes peptide bond o Elongation continues when ribosome moves to the right causing val-tRNA to occupy P site as A site becomes unoccupied this is called translocation o Then leu-tRNA shifts to P site fills A site o Ultimately the P site is moving towards the A site this continues until it reaches a stop codon causing dissociation of small and large subunits from mRNA Transcription: conversion of genetic (base) sequence of polynucleotides in DNA into RNA transcripts o Happens in cell nucleus and there are 3 types mRNA carries the genetic code for synthesis of proteins rRNA structural and functional components of ribosomes tRNA helps incorporate amino acids into polypeptide chains o RNA polymerase binds to the promoter of a gene within the DNA, only one strand of double-stranded DNA provides a template for transcription of mRNA. The one is complementary o List of participants in transcription: RNA polymerase Accessible template DNA Pool of ribonucleotides (A,U,G,C) Rate of transcription is about 50 nucleotides per second o Key principle: Default state of most genes is called DORMANCY or are to be transcriptionally inactive DNA-histone interactions cause DNA to be inaccessible to RNA polymerase To activate, you need transcription bubbles and accessibility of polymerase to promoters This is accomplished by chromatin remodeling DNA MUST BE FREED FROM NUCLEOSOMES FOR TRANSCRIPTION TO TAKE PLACE o Nucleus at interphase Peripheral “barrier” is the nuclear envelope Chromatin is dispersed into interphase state The transportation of mRNA happens through nuclear pores which are small openings in the membranous envelope that functions as a barrier between the cytoplasm and the nucleoplasm 3,000 to 4,000 pores per interphase nucleus Nucleo-cytoplasmic transport occurs through nuclear pores Into the nucleus is 60,000 protein molecules Out of the nucleus is 50-150 mRNA molecules, 10-20 ribosome subunits, and 1000 tRNAs ▯ ▯