Discuss How E.Coli Lac Operon Is Controlled Bradford Uni Assignment

827 words - 4 pages

Essay 7- The Lac Operon
Practice Essays
Molecular Genetics
Semester 2
Year 2 Biomedical Science
Serat-E Ali
“Discuss how the Escherichia coli lac operon is controlled.”
It is well known that bacterial do not express all their genes all the time to save resources. However the bacteria need to respond quickly to changes in the environment, these changes can be met by grouped genes which encode proteins that work together known as operons. E.coli is one of the most studied organisms worldwide, especially the study of its operons. E.coli can digest the sugar lactose, the genes which it needs to do this are inducible by the inducer, lactose. E.coli only needs the proteins to digest lactose when lactose is present. The lac operon consists of a few key genes for proteins, this proteins include: B-galactosidase, lactose permease and A-tranacetylase, which are translated from LacZ, LacY and LacA genes respectively.
B-galatosidase is an enzyme which cleaves lactose into galactose and glucose, it also catalyses the isomerisation of lactose to allolactose, a compound important in regulating the expression of the lac operon. Lactose permease Is a membrane bound proteins that brings lactose into the cell, and A-tranacetlyase rids the cell of toxic thiogalatosides that are taken up by the permease. In E.coli in a medium containing glucose, only a low concentration of each of these three proteins is produces as glucose is favoured over lactose. However in the presence of lactose and absence of glucose there are about 3,000 molecules of b-galactosidase per cell. The genes mentioned above, are transcribed into mRNA’s: these mRNA’s have short half-lives so the transcripts for these must be made continually in order for the enzymes to be produced. When lactose is no longer present production of mRNA is stopped and the mRNA already present is broken down so no more protein is made. On the lac operon there is also a lacl- gene present, this is the regulatory gene which is located close to the structural gene. Lacl- codes for a repressor molecule which controls the negative control of the lac operon system. The promoter for lacl- is weak so only a few repressor molecules are made, however these repressor molecules are made constitutively and bind to the operator. Once bound to the operator the lac repressor prevents transcription of mRNA as RNA polymerase cannot bind to the promoter when the repressor is bound to the operator (the operator modulates the expression of the gene). The lac repressor binds to the DNA sequence of the operator and overlaps the sequence to which the RNA polymerase binds. When the repressor is bound to the operator RNA polymerase cannot bind to the promoter and so no mRNA is produced and transcription cannot occur.
When E.coli grows in the presence of lactose as the only carbon source, some lactose is converted to allolactose by B-galatosidase. Allolactose binds to the lac repressor and changes its shape, the lac repressor loses its affinity to the operator, with no repressor bound to the operator, RNA polymerase is free to make polycistronic mRNA for lacZ, lacY and lacA which is translated by ribosomes into functional proteins. We now understand that the lac repressor protein exerts a negative control on the lac operon, preventing transcription, but there is also a positive control system which functions to turn on the expression of the operon. This system ensures that the operon is expressed at high levels only if lactose is the only carbon source, not if glucose Is present. More energy can be obtained from glucose than other sugar so cells do not waste energy on using lactose if glucose is present. if lactose is present and glucose is absent then a protein called Catabolite activator protein (CAP) binds to cAMP to form a CAP-cAMP complex, this complex is the positive regulator molecule. The CAP-Camp complex binds to the CAP site which is upstream of the site at which RNA polymerase binds to the promoter. CAP then helps RNA polymerase to bind and start transcription. However when glucose is present then it reduces the amount of cAMP in cells to be low. Adenylate cyclase makes cAMP, and when glucose is present Adenylate cyclase no longer works. This prevents the CAP-camp complex from forming. The operon has 4 different state: when no glucose and no lactose present, when no lactose but glucose present, when glucose and lactose both present and finally when there is only lactose.
In conclusion it is key to understand how the lac operon inducible system works within E.coli. Study of these operons leads to advancement in study of the human genome too, and applicable traits. Lac operon is a prime example of how bacterial ensure the conservancy of resources by turning off and on expression of genes dependent on need. As this gene regulation in bacteria is not fully understood, understanding how these genes are regulates helps us to understand how genes are regulated in higher organisms like humans.


In this essay I will discuss how the doctrine of consideration is - law - assignment

1997 words - 8 pages Assignment In this essay I will discuss how the doctrine of consideration is too firmly fixed to be conquered by promissory estoppel. The doctrine of cconsideration has been a necessary component in contract law for the last number of years. Without its presence within a case, agreement or settlement it will be deemed not legally enforceable. Consideration is to contact law as Elvis is to rock and roll: the King”.[footnoteRef:1]Over the years

How is Chinese Cinderella similar to Disney's Cinderella - High School 9 - Assignment

920 words - 4 pages Sana Shariflou How is Chinese Cinderella similar to the story of Cinderella? Chinese Cinderella is a biography of Adeline Yen Mah and her emotional and physical childhood journey in which she lived her story similar to Disney’s Cinderella. Chinese Cinderella holds many similarities to Disney’s Cinderella hence the name Chinese Cinderella. This can be seen in the characters and their resemblance with Disney’s version of the fairy tale and

time management: how important time management is to our lives - creative thinking - assignment

438 words - 2 pages The Importance of Time Management George Osoro The Importance of Time Management Time has an infinite measure that only goes forward and never back. It is an important element in our lives and the world is based on a time system. Even the ancient people knew the importance of time just as we do. All living things die as time passes on. And this makes time very precious to all living things, most importantly humans. Many can agree with me

This is an essay assignment relating to student loan debt and how it affects young adults. - Current Issues - Assignment

834 words - 4 pages of 50 states cut higher education funding to help budgets. Cuts continue to this day. When cuts occur , the schools either decrease operational costs or pass it on in tuition. · Cost of technology - technology is more important these days than it was 30, 20, even 10 years ago. On campus technology for every student is a large factor. How to Cut Costs: If you look at the bigger picture when wanting to cut tuition costs for colleges, there are

Questions pertaining to the assignment of analyzing the website Cardswap and how effective it is - Consumer Behavior TWU - Assignment

642 words - 3 pages amount on the gift card. 6. What is the value of a customer to CardSwap? How much should Poptia be willing to pay to recruit a customer? The value of a customer to CardSwap is extremely important. Without customers, the site there would be no one to sell or buy gift cards and the site would be useless. Poptia should be willing to pay a small percentage. I believe that the advertising I the METRO is pointless. Readers are not going to pay

2018 NFL Mock Draft- Picks 1-20 - Lunch - Essay

929 words - 4 pages rusher, so they grab Davenport at #14. 15.Arizona Cardinals- Calvin Ridley, WR, Alabama | Larry Fitzgerald is bound to retire any season now, and the Cardinals have Sam Bradford as their hopeful bridge or even franchise QB. The Cardinals grab the best receiver in the draft. 16.Baltimore Ravens- Josh Jackson, CB, Iowa | This is a potentially controversial move, but the Ravens get a CB who fits nicely with their defensive scheme who plays the game

Pot Prohibition

1878 words - 8 pages controlling the market and making billions of untaxed dollars. So the theory is that when you eliminate the underground marijuana industry, all the cartels and gangs will stop dealing and doing those illegal activities because it is no longer profitable to them because it is now federally regulated. So the question that is raised is how those gangsters would, and the people who cause the violent crimes associated with the underground market, stop

Anthropology 110- Review chapter 9 - Anthropology 110 - Chapter 9 Study guide

707 words - 3 pages and collecting data about people, cultures, and natural environments. Field work is conducted in the wild of our everyday surroundings rather than in the semi-controlled environments of a lab or classroom. Ethnology: the study of how and why recent cultures differ or are similar; cross-cultural Ethnohistory: studies based on descriptive materials about a single society at more than one point in time (information from a variety of sources ex

problem question on child law with detailed plan - undergrad - child law

474 words - 2 pages CHILD LAW ASSIGNMENT PLAN STATE the law, EXPLAIN the law and APPLY the law · What are the judges going to rely on? The courts stand point. Always decide who the parent is first. Bring in human rights issues. Different acts apply to different bits Advise Salman 1. Parenthood and Parental Responsibility. · Who is a parent in law? Re G quote baroness hale on who is a parent. · Who is the mother? S 33(1) HFEA 2008 · Who is the father? Legal

critical reflection of a personal academic journey using the MBTI - University of Gloucestershire - Essay

3345 words - 14 pages understanding for my inferior function has shown me how it manifests my personality. If I have a question about an upcoming assignment I never speak up and ask it because I think it is a stupid question and I do not want to look stupid in front of teachers or peers. This leads me to procrastination, as I cannot move forward with an assignment without a clear idea of what I need to do. In furtherance of my personal growth I need to avoid obsessing over my

Of mice and men

772 words - 4 pages Group Assignment: MGM 3101 (Group1)Semester 1 2014/2015Lecturer: DrHaslindaHashimRoom: E102Phone: ext 7890Email:ACTIVITY 1Topic: Environments of Business OrganizationsMain Task: To apply the understanding of knowledge learned in class to real life examples and situations that happen in the workplace through the development of term papers.a. Each group is requested to choose one established organization and arrange for an interview with one

There are over millions of robots in the world that created a great universal purpose. - U of M SCMS - There are over millions of robots in the

586 words - 3 pages Deema Hujeir Technology Paper SCMS – 4510 – 001 Dr. Bradford Eichhorn November 23, 2018 Robotics There are over millions of robots in the world that created a great universal purpose. Whether we realize it or not, robotics plays a big role in making our daily lives better because robots are much faster, easier, more accurate, uncomplaining, and tireless. Nowadays using robotics is more efficient and capable of serving humans in a much more

Governance, procurment and commission - Undergraduate - Health and social care

1003 words - 5 pages improvement (5000 words - One element of assessment with 100% weighting and 40% pass mark). Module learning outcomes You will need to demonstrate you meet the following module learning outcomes in your assignment. Knowledge and Understanding  Discuss UK government processes related to corporate and clinical governance of health and social care  Analyse quality management and quality assurance in relation to governance in health and social care

personal statement for all english classes - eshs english 12 - essay

814 words - 4 pages pursue further academic studies is fueled by the enriching experience I have had at the University of Bradford. Being surrounded by intellectually engaging individuals from diverse backgrounds and an academically rigorous course has stimulated my passion even more. My current degree course is a combination of Economics and a range of characteristics of Finance (e.g. Macroeconomics, Microeconomics, Financial Economics, Economics and Finance of

The Social Crisis of Social Media - Debate class - Argument Essay

1024 words - 5 pages Rague 2 A Social Crisis Mackenzie Rague LAC 210 University of Southern Maine Portland, Maine Most people believe that social messaging is more of a benefit than a consequence, but using social media can be harmful. Social media is something most kids, teens, and even some adults are using all the time. It has become a part of our generation’s lives. Having people on their phones all day long is not only disappointing, but also damaging. Instead