Answer:
The main function of the RB protein is to inhibit the transition from the G1 to S phase. Its activity depends on its phosphorylation state: if RB is not phosphorylated (active state), it is bound to the transcription factor E2F, preventing its translocation to the nucleus and the activation of genes necessary for DNA synthesis; and if it is phosphorylated, by cyclin-CDK complexes, E2F is released and cell proliferation occurs.
Explanation:
Retinoblastoma (Rb) was the first tumor suppressor described and, as we know today, mutations in its structure determine a large number of cancers. Structurally, we speak of a large and multifunctional protein; which is organized in different domains. The activity of this protein is regulated, mainly, by phosphorylation at multiple sites described over the years and is involved in control mechanisms of the cell cycle, apoptosis and senescence.
Much more because you have a weather nation over the other.
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Answer:
The cell membrane is semipermeable because allows only certain molecules to pass through.
Explanation:
Semipermeability is a common property of cell membranes, due to their predominantly lipid composition, which gives them a hydrophobic character.
The cytoplasmic membrane is constituted by a double layer of lipids, in addition to structural proteins and glucides, which prevent the entry of polar or charged molecules. This characteristic allows lipids and small molecules without charge to pass freely through it.
Regarding the other options:
<em> A. Cell membranes are associated with lysosomes, structures that contain enzymes. However, this characteristic is not related to semipermeability.</em>
<em> C. They allow the passage of small molecules - devoid of charge - through them.</em>
<em> D. Not all non-polar molecules pass through, as some need a transporter.</em>
