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BS 161 Final Exam Study Guide

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by: Sarah Struble

BS 161 Final Exam Study Guide BS 161

Marketplace > Michigan State University > Biology > BS 161 > BS 161 Final Exam Study Guide
Sarah Struble
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About this Document

Includes: Everything you need to know for the final! Review of all chapters and new material (Transcription, Translation, Gene Regulation in Prokaryotes and Eukaryotes, and Cell Signaling) Key i...
Cell and Molecular Biology
D. Koslowsky, J. Merrill
Study Guide
50 ?




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1 review
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"Clutch. So clutch. Thank you sooo much Sarah!!! Thanks so much for your help! Needed it bad lol"
Mr. Raheem Shields

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This 8 page Study Guide was uploaded by Sarah Struble on Monday December 14, 2015. The Study Guide belongs to BS 161 at Michigan State University taught by D. Koslowsky, J. Merrill in Fall 2015. Since its upload, it has received 290 views. For similar materials see Cell and Molecular Biology in Biology at Michigan State University.


Reviews for BS 161 Final Exam Study Guide

Star Star Star Star Star

Clutch. So clutch. Thank you sooo much Sarah!!! Thanks so much for your help! Needed it bad lol

-Mr. Raheem Shields


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Date Created: 12/14/15
BS 161 Final Study Guide Macromolecules to Remember Carbohydrates: • • Amino Acids: - Protein backbone: • Nucleic Acids: • RNA: OH on 5-Carbon ring (sugar) • DNA: H on 5-Carbon ring • Lipids: • fatty acid: • triglyceride: • phospholipid: Transcription: Key Ideas: • DNA—> RNA • DNA is used as a template to make RNA • Differences in Prokaryotes and Eukaryotes: • bacteria lack nuclei, DNA is not in a separate compartment of cell, so transcription and translation occur together is one compartment • eukaryotes: have nuclei which contains the genetic info of a cell. machinery for replication is found within the nuclei. Transcription and translation are separate. transcription happens in the nucleus where the DNA is found, then the RNA is moved out of the nucleus for translation to occur. - two types of chromatin: euchromatin (DNA that is expressed) and heterochromatin (inactive DNA) - only euchromatin is associated with transcription - in eukaryotes, transcription is activated by histone acetylation • 3 Types of RNA: • mRNA: RNA that contains information for protein synthesis. • tRNA: VERY IMPORTANT IN TRANSLATION. it transports the amino acids to the ribosome, positions each amino acid at the correct place on the elongating polypeptide chain. Involved in translating the nucleotide code into amino acids • rRNA: major component of ribosomes. Ribosomes are made of mRNA and protein • Transcription Process: • Need DNA template • Need ATP, GTP, CTP, and UTP • Need RNA polymerase • DNA Template - Structure of a gene promotor: defines the start of transcription • • terminator: defines end of transcription • Initiation: requires a promotor that recruits the RNA Polymerase and other transcription factors. • General transcription factors: help RNA pol bind, need specific transcription factors to lead to high level of transcription, bind to TATA box • direction of transcription is “downstream” • RNA polymerase- can only add ribonucleotides to 3’ end (like DNA Polymerase), it can initiate strand synthesis (unlike DNA Polymerase) - moves along the template strand of DNA in the 3’ to 5’ direction • Elongation: step where RNA Pol is moving along DNA template, assembling the RNA, adding nucleotides to the 3’ end. As it moves along DNA, it continues to untwist the double helix (exposing 20 bases at a time), DNA double helix can reform behind it, displacing the new RNA molecule from its template • Termination: RNA Pol encounters a terminator sequence that tells RNA Pol to stop. • prokaryotes: once it reaches terminator sequence, it stops, releasing both RNA and DNA • eukaryotes: end of gene is signaled by Polyadenylation Signal (AAUAAA) which tells RNA to terminate. • RNA Processing: only in eukaryotes: transcription produces a primary transcript that is processed to form a mature RNA • 5’ end is “capped” (5’ cap is unique to mRNAs) • 3’ end is polyadenylated • RNA Splicing: Removal of introns Translation: Key Ideas • RNA—> protein • requires a lot of energy! • mRNA is read as sequence of 3 bases called codons • each codon specifies one amino acid there is redundancy (several codons may specify • the same single amino acid, but no codon codes for more than one amino acid) • tRNAs read the codon sequence to assemble the protein • anticodon is unique to each tRNA, anticodon reads the mRNA by pairing with the mRNA codon • 3’ end of tRNA is the amino acid attachment site • Aminoacyl-tRNA Synthetases: enzyme that attaches a specific amino acid to a specific tRNA • the carboxyl end of amino acid is linked to the tRNA • result is aminoacyl-tRNA (charged amino acid): requires 1 ATP • Ribosomes bring the mRNAs and tRNAs together for protein synthesis • each ribosome has binding site for mRNA and three binding sites for tRNA • P site: holds the tRNA carrying the growing polypeptide chain • A site: holds tRNA with next amino acid to be added to chain • E site: (exit site) discharged tRNAs leave the ribosome at this site • Translation Steps • Initiation: bringing all parts together. large and small subunits of ribosome assemble with mRNA and aminoacyl-tRNA, initiator tRNA Elongation: adding each amino acid to chain. tRNA comes into the A site. Amino acids • form new peptide bonds and the whole structure moves over. tRNA from A site goes to P site. tRNA from P site goes to E site where it is released. • Termination: ribosome encounters a stop codon, which causes the ribosome to disassemble. polypeptide is released from tRNA and tRNA is released from ribosome • Translation begins in cytoplasm, but for proteins that need to go somewhere else will have a signal peptide region. (Ribosomes are directed to ER by a signal recognition particle that brings ribosomes to a receptor protein in ER membrane) Gene Expression in Prokaryotes: • Genes are organized into operons: transcriptional unit under the control of a single promotor and operator - promotor: nucleotide sequence that enables the gene to be transcribed - operator: segment of DNA that a repressor binds to • the operon is transcribed as a polycistronic transcript coordinate control of gene expression • Tryptophan Synthesis • trp operon: consists of the operator, the promotor, and the genes they control • it can be switched on and off by trp repressor (repressor binds to operator, blocking RNA Pol from attaching to promotor which prevents transcription of the operon’s genes. This is reversible) repressor proteins are allosteric, change shape depending of binding of other molecules. • (trp repressor has two shapes: active and inactive) • trp repressor is synthesized as INACTIVE. to activate, it must bind to tryptophan • when concentrations of tryptophan are high, some of these molecules bind to the repressor protein the activate it. Then the repressor binds to operator to turn the operon off. Lac Operon • When lactose is present in the cell, allolactose (an inducer) binds to the repressor, which inactivates the repressor so the lac operon can be transcribed • When glucose and lactose are both present, and glucose levels are low, cAMP accumulates in the cell. when cAMP is abundant, it binds to CAP (an activator of transcription), which activates it so it attaches to the promotor and INCREASES its affinity for RNA Pol which increases the rate of transcription. • The lac operon is under dual control: negative control by lac repressor, positive control by CAP • repressor turns it on/off • CAP speeds it up or slows it down (if the repressor is inactive) • Two Types of Operons: Repressible operon: (trp operon) one that is inhibited when a specific small molecule binds • allosterically to a regulatory protein • Inducible operons: (lac operon) regulatory protein is synthesized as active (inhibotory), so the operon is off. Allosteric binding by an inducer molecule makes the regulatory protein inactive and the operon is turned on Gene Expression in Eukaryotes • Gene expression is coordinated by similar control elements promoting simultaneous transcription of related genes • Differs from bacterial because gene expression can be regulated at any stage: DNA Packaging, Transcription, RNA Processing, RNA transport out of nucleus, Translation, and Protein Activation DNA Packaging A. 1. Level one packaging: Nucleosome a) DNA double helix wrapped around histone core 2. Level Two Packaging: Solenoid • The way that DNA is packaged affects the gene expression. Chromatin structure must be relaxed/de-condensed in order to replicate (and therefor be expressed) DNAase cannot cut condensed chromatin • B. Transcription-Stage Regulation 1. Histone Acetylation • Two balancing enzymes: a) Histone Acetyltransferases (HATs): activate transcription b) Histone Deacetylases (HDACs): inhibitors, repressors of transcription, remove acetyl groups 2. DNA Methylation: reduces gene expression a) Methyltransferases: enzyme that add methyl groups to DNA bases, which inhibits transcription • Methylated DNA turns off transcription C. Fine-Tuning Transcription Initiation Mechanism for Gene Expression • General and specific transcription factors are essential for high levels of transcription • Enhancers are distal control elements. • An activator is a protein that binds to an enhancer to stimulate transcription of a gene • Also have repressors to inhibit the expression of a specific gene by blocking the binding of activators D. Post-Transcriptional Regulation • Cells can fine-tune gene expression in response to environmental changes without altering transcriptional patterns Alternative RNA splicing: specific regulatory proteins control intron-exon choices by 1. binding to regulatory sequences within the primary transcript E. Translation Regulation of Gene Expression 1. Initiation of translation can be blocked by regulatory proteins that bind to specific sequences/structures within untranslated RNA to prevent ribosome attachment F. Post-Translational Regulation Many proteins must undergo chemical modification before they are functional • • To mark a protein for destruction, cell attaches ubiquitin to it. Proteasome's recognize and degrade the tagged protein. Mutations making cell cycle proteins impervious to proteasome degradation can lead to cancer. Cell Signaling Direct Communication • • Gap junction: animal cells • Plasmodesmata: plant cells • Direct contact: adjacent plasma membrane • Paracrine Signaling • signal released from cell has effect of neighboring cell important in development • • Endocrine Signaling - hormones released and travel through circulatory to affect other places in the body • Synaptic Signaling - how our nerves work (animal cells only) • 3 Steps: 1. Reception Signal —> binds —> activates receptor • 2. Transduction • receptor passes signal into a pathway 3. Cellular Response • signal tells cell to do something • Molecular Switches (on/off) • 3 Main Ones: Ligand Binding (noncovalent): 1. - protein binds a small molecule, changes shape of protein - “allostery” - ex) Tryptophan Repressor, Lac Enzyme 2. Protein Phosphorylation (covalent): - covalent addition of a phosphate group to an amino acid - proteins that can phosphorylate a substrate: Kinases 3. GTP Binding and Hydrolysis: - functions similar to phosphorylation. GTP highly charged, binds, can change shapeChemical Signals: - hydrophobic: molecules can easily cross membrane - hydrophilic: molecules need help crossing membrane • Receptors in Plasma Membranes: - Most hydrophilic signal molecules bind to specific sites on receptor proteins in membrane - 3 Main Types: 1. Ion Channel Receptors 2. G-Protein Receptors 3. Enzymatic Receptors • G Protein-Coupled Receptor - vision - odor transduced signal Other Study Materials:


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