![emmanolan112](/avatars/34695.jpg)
emmanolan112
14.06.2021 •
Biology
Explain the lac operon. How does it work when lactose is present and when lactose is not present. What about the presence of glucose?
Solved
Show answers
More tips
- F Food and Cooking Learn How to Make Ice Cream at Home - Step by Step Guide...
- H Health and Medicine When can it be said that a person has a normal pulse?...
- A Art and Culture When Will Eurovision 2011 Take Place?...
- S Style and Beauty How to Choose the Perfect Hair Straightener?...
- F Family and Home Why Having Pets at Home is Good for Your Health...
- H Health and Medicine How to perform artificial respiration?...
- H Health and Medicine 10 Tips for Avoiding Vitamin Deficiency...
- F Food and Cooking How to Properly Cook Buckwheat?...
- F Food and Cooking How Many Grams Are In a Tablespoon?...
- L Leisure and Entertainment Carving: History and Techniques for Creating Vegetable and Fruit Decorations...
Answers on questions: Biology
- E English QUESTION 27 aggressively If an adult model acted aggressively toward the Bobo doll in Albert Bandura s classic study, children acted toward it. If the model didn...
- B Biology The energy in molecules has been stored in the 1.protons 2.Bonds 3.electrons 4.neutrons...
- E English Anyone watch n.i.g..g.a lodian...
Ответ:
The lac operon is an operon used to transport and metabolize lactose. In the presence of lactose, it functions as an inducer, it binds to the Lac I repressor protein and generate a conformational change that decreases its affinity for the operon region. Thus, the operon region is left free, the RNA polymerase can transcribe the structural genes.
Explanation:
An Operon is a group of structural genes whose expression is regulated by the same control elements and genes. The lac operon is an operon used to transport and metabolize lactose in Escherichia coli bacteria. Lactose is a disaccharide formed by the union of a glucose molecule and a galactose molecule (monomers). Upon breaking the glycosidic bond of lactose, both monomers are released and become available for use for energy. Remember that glucose is the main source of energy, and bacteria will always prefer to metabolize glucose rather than any other sugar, which they will only metabolize as an alternative energy source if glucose is not available.
The operon consists of several structural genes:
Lac z gene: encodes the enzyme β-galactosidase, which catalyzes the hydrolysis of lactose into glucose and galactose.Gene lac y: encodes the protein galactoside permease, for the transport of lactose into the bacterium.Promoter: region of DNA upstream of the above-mentioned genes that controls their expression, and where RNA polymerase binds to carry out gene transcription (synthesis of RNA from DNA that involves the expression of a gene).Operator: region of DNA located between the promoter and the beginning of the structural genes, which is recognized by the repressor protein Lac I.Repressor gene: encodes the Lac I repressor protein, which binds to the operator region and thus prevents transcription of genes under the control of this promoter. When the repressor is removed from the operator (in the presence of inducer which is lactose), RNA polymerase is ready to bind and start transcription.So, the lac operon is under a type of negative regulation, where genes can always be transcribed, except when the Lac I repressor protein is bound to the operator region. The promoter of the lac I gene is constitutive, so the Lac I protein is permanently expressed and remains bound to the operator, preventing the transcription of structural genes. That is, preventing the action of the lac operon in the absence of lactose. However, in the presence of lactose, it functions as an inducer of the operon. It is able to bind to the Lac I repressor protein and generate a conformational change that decreases its affinity for the operon region. Thus, the operon region is left free, the RNA polymerase can freely transcribe the structural genes, the enzyme β-galactosidase is synthesized which can degrade lactose to glucose plus galactose (and thus metabolize the lactose in the medium).
It should be clarified that in reality, the true inducing molecule of the lac operon is allolactose, an isomer of lactose obtained by a transglycosylation occasionally carried out by β-galactosidase. But usually to simplify terms, lactose is referred to as the inducer.
So, the lac operon is always inactive unless there is lactose in the medium. As mentioned, E. coli prefers glucose, so the lac operon will not be activated in the presence of lactose if glucose is present in the medium. If both glucose and lactose are present in the medium, the repressor is inactivated, so the operon is transcribed but at a basal (low) level due to the presence of glucose.
Ответ:
without atoms, the chemical elements wouldn't exist. then, molecules, then proteins, then life itself. basically we're made out of atoms just like everything else.