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DochEvi [55]
2 years ago
9

A list of some aspects of cell theory is below. 1. All living cells must have a cell wall. 2. All living cells require oxygen fo

r survival. 3. The basic unit of life is a cell. Which of the aspects above are included in cell theory? A) 1 only B) 1 and 3 Eliminate C) 2 and 3 D) 3 only
Biology
1 answer:
NeX [460]2 years ago
6 0
D. 3 only is the answer
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How does the mRNA leave the nucleus?
Zina [86]
I hope this helps you very much you’re welcome !

6 0
2 years ago
A set or structures inside the nucleus that contains the directions for how 10 to make a new organisin. -​
NNADVOKAT [17]

Answer:

DNA

Explanation:

The nucleus is a central placed organelle in eukaryotic cells. It is said to contain the "blueprint of life" known as the DNA. The DNA is a structure located in the nucleus of the cell that encodes information necessary for the growth and development of the organism.

This information encoded by the deoxyribonucleic acid (DNA) of the cell includes how the organism will reproduce, hence, DNA is called the blueprint of life.

3 0
2 years ago
Describe the probable effects on gene expression in the lac operon of each mutation: a. Mutation in the lac operator that delete
Stella [2.4K]

Answer:

a. Reduces represor binding.

b. Constitutive expression of the operon.

c. Stronger promoter if it is more similar to the consensus sequence. Weaker promoter if less similar.

Explanation:

The lac operon is an operon required for lactose transport and metabolism in enteric bacteria such as <em>Escherichia coli</em>. <u>It is regulated by glucose and lactose availability</u> and consists of the following structural genes:

  • Lac z gene: encodes the enzyme β-galactosidase, which catalyzes the hydrolysis reaction of lactose into glucose and galactose.
  • Gene lac y: encodes the protein galactoside permease involved in the transport of lactose into the bacterium.
  • Lac a gene: encodes the enzyme thiogalactoside transferase, which catalyzes the transfer of the acetyl group of acetyl coenzyme A to 6-OH of a thiogalactoside acceptor. This gene is not related to lactose metabolism.
  • Promoter: region of DNA recognized by RNA polymerase for transcription.
  • 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 (lac I): encodes the Lac I repressor protein, which recognizes the operator region, where it binds. It prevents the transcription of genes under the control of this promoter but stimulates the binding of RNA polymerase. When the repressor is absent (in the presence of inducer which in this case will be lactose or IPTG), RNA polymerase will begin transcription.

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 operon region, for which it has a high affinity. In this case, the promoter of the lac I gene is constitutive, so the Lac I protein is permanently expressed and remains bound in tetramer form to the operon region, preventing the transcription of structural genes.

Since lactose is the 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, <u>RNA polymerase can freely transcribe the structural genes and β-galactosidase can degrade lactose to glucose plus galactose</u>. <u>In the absence of lactose, the Lac I repressor protein maintains its high affinity for the operator region, preventing RNA polymerase from transcribing the structural genes</u>. In this way, the system remains closed with consequent energy savings for the bacterium.

As a final clarification, actually the true inducing molecule of the lac operon is called allolactose, an isomer of lactose obtained by a transglycosylation occasionally carried out by β-galactosidase.

a. When there is a mutation in the lac operator that deletes most of the operator, then the repressor Lac I can no longer bind and RNA polymerase will begin transcription.

b. When there is a mutation in the Lac I gene that eliminates the binding of repressor to operator, then this protein can not produce the repression so there would be a constitutive expression of the operon.

c. Since the promoter us a region of DNA recognized by RNA polymerase for transcription, if there is a mutation here it will generate a stronger promoter in the case that this part is similar to a consensus sequence (the most commonly encountered nucleotides found at a certain location). In the case that it is less similar, then it will generate a weaker promoter.

7 0
3 years ago
The net energy yield from this pathway, where glucose is broken down through several steps forming pyruvate, is ________ molecul
stepan [7]

Answer:

2 molecules of ATP and 2 molecules of NADH

Explanation:

Glycolysis is the first step of cellular respiration (break down of glucose to extract energy) which occurs in the cytoplasm. Glycolysis is a pathway common to all living organisms- prokaryotes and eukaryotes, as it does not require oxygen to occur.

Glycolysis occurs in two major phases (ten steps) requiring 10 enzymes catalyzing each step; the energy-requiring phase and the energy-requiring phase.

In the energy-requiring phase, the starting molecule (glucose) gets rearranged in a series of chemical reactions, and two phosphate groups gets attached to it producing fructose-1,6-bisphosphate which is unstable, This modified sugar then splits in half due to its instability to form two different but inter-convertible phosphate-bearing three-carbon sugars (Dihydroxyacetonephosphate, DHAP and Glyceraldehyde-3-phosphate, G3P). Because the phosphates used in these steps come from 2 ATP molecules, 2 ATP molecules get used up in this phase

All the DHAP molecules get converted to G-3-P in order to enter the next phase.

In the energy-recovering phase, the 3-carbon sugar (G3P) is converted into another three-carbon molecule called pyruvate, through a series of reactions. In these reactions, two ATP and 1 NADH molecules are made. This recovery phase occurs twice (one for each of the two isomeric three-carbon sugars, DHAP and G3P). Hence, a total of 4 ATP and 2 NADH molecules are produced in this phase.

Overall, Glycolysis converts one glucose (six-carbon) molecule to two pyruvate (three-carbon) molecules and a net release of 2 ATP molecules (4 overall - 2 used) and 2 NADH molecules.

3 0
2 years ago
Which is not part of the earth system biosphere hydrosphere atmosphere hellosphere
kondor19780726 [428]

hellosphere. This is not an actual part of the "spheres" on Earth

Hope this helps

4 0
3 years ago
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