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Morgarella [4.7K]
3 years ago
11

Following repolarization, the neuron may become slightly hyperpolarized before it re-establishes its resting membrane potential.

Hyperpolarization is due to a difference between how the voltage-gated Na+ and K+ channels work. What is this difference?
Biology
1 answer:
RoseWind [281]3 years ago
3 0
<h2>Membrane potential </h2>

Explanation:

  • Membrane potential represents charge difference across the membrane, all biological cells are negative inside (cytoplasm) and positive outside (due to difference in ionic distribution)  
  • In a typical neuron cell membrane potential of cytoplasm is negative at rest (when no stimulus is applied) hence called resting membrane potential
  • Resting membrane potential of excitable cells is established by Na+ and K+pump
  • Repolarization starts with the efflux of K+ by the opening of voltage gated K+ channels
  • Voltage gated K+ channels starts to open when voltage gated Na+ channels becomes inactive
  • Hyperpolarization occurs due to excessive efflux of K+ by voltage gated K+ channels
  • Additional efflux of K+ occurs due to slow inactivation of voltage gated K+ channels
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With incomplete dominance a likely ratio of phenotypes in the F2 generation resulting from a monohybrid cross between two true-b
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Answer:

A) 1:2:1

Explanation:

Incomplete dominance is an effect observed in the organisms in which the neither of the two alleles controlling a trait is dominant or recessive instead produces a phenotype formed by the mixture of the effect of the two alleles.  Therefore in incomplete dominance, a new trait is produced which is formed by both the alleles.

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Thus, Option-A is the correct answer

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4 0
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Following antigenic stimulation, phosphorylation of _________ relieves inhibition of the transcription factor
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Answer: zap70, ITAM.

Explanation:

An antigen is any substance that is capable of stimulating an immune response by activating lymphocytes, which are the body’s infection-fighting white blood cells. Examples of antigens could be proteins that are part of bacteria or viruses or components of serum and red blood cells from other individuals, all of them are foreign antigens originated outside the body. However, there can also be autoantigens (which are self-antigens), originated within the body. In normal conditions, the body is able to distinguish self from nonself. <u>And the antigens that represent a danger induces an immune response by stimulating the lymphocytes to produce antibody or to attack the antigen directly</u>. This is called an antigenic stimulation of the immune system.

ZAP-70 (Zeta-chain-associated protein kinase 70) is a protein that is part of the T cell receptor, thereby it plays a critical role in T-cell signaling. When the TCR (receptor of T cells) is activated by the presentation of the specific antigen through the MHC, a protein called Lck acts to phosphorylate the intracellular CD3 chains and the ζ chains of the TCR complex, allowing the binding of the cytoplasmic tyrosine kinase, ZAP-70. Lck then phosphorylates and activates ZAP-70, which in turn phosphorylates another molecule in the signaling cascade called LAT (short for Linker of Activated T cells), a transmembrane protein that serves as an anchor site for several other proteins. The tyrosine phosphorylation cascade initiated by the Lck culminates in the intracellular mobilization of calcium ion (Ca2+) <u>and the activation of important signaling cascades within the lymphocytes.</u> These include the Ras-MEK-ERK pathway, which is based on activating certain transcription factors such as NFAT, NFκB and AP-1. These transcription factors regulate the production of of certain gene products, most notably cytokines such as interleukin-2 that promote the long-term proliferation and differentiation of activated lymphocytes.

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So, ZAP-70 is a protein tyrosine kinase with a role in T-cell receptor signal transduction. During T-cell activation, ZAP-70 binds to ITAM and becomes tyrosine phosphorylated. The binding of ZAP-70 to the phosphorylated ITAM is able to activate its kinase activity, <u>and relieves the inhibition of the transcription factor which regulates genes that are involved in the immune reaction</u>.

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