Answer:
The process of passage of different molecules, solutes, and liquids, through the phospholipid bilayer in human cells, and really in all animal cells, is highly dependent on a tight coordination between chemical, and thermodynamic balances, that will collaborate in these elements being able to pass, or not pass, through a cell´s membrane, and activate other mechanisms within the cell when their passage is not possible. Unlike what was once believed, that transport proteins were like buses parked at the membrane and waiting to be loaded with molecules to later remove themselves from the membrane and carry their load into the cytoplasm, scientific research has found that this is definitely so, and that transport proteins do not come off the layer to transport molecules. They are permanently anchored to the membrane and through a series of second messenger systems, energy produced by the passage of certain ions like potassium and sodium, and other such processes, these transport proteins become activated, allow the passage of molecules and change them in such a way that they can be taken into the cell in vesicles, or, they will anchor them to second messengers, who will be responsible for carrying the molecule inside.
From the list of words given and the two sentences down below, which are two reasons why the earlier believed models for transport proteins are not correct would be:
1. Integral membrane proteins are embedded stably in the membrane and protrude from one or both side based on their hydrophobic, or hydrophilic, regions. These sides will not switch because of the disbalance that would be created if the two sides had to be switched chemically to allow them to pass to the opposie sides.
2. For protein to traverse a membrane, movement of its hydrophilic regions through the interior of the membrane would be required, which would be highly endergonic and hence thermodynamically improbable.
Solution:
Phospholipid lipids is that contribute to the structure and function of the cell membrane.
Lipids all have one thing in common - they do not mix well with water. You can see this quite well if you try to combine oil and water. No matter how much or how hard you shake them together, they remain separated. This can be useful for organisms. For example, ducks produce lipids in their feathers, allowing the water to roll right off their backs and helping the ducks stay afloat.
Phospholipids are made up of two fatty acids (long chains of hydrogen and carbon molecules), which are attached to a glycerol 'head.' The glycerol molecule is also attached to a phosphate group, and this is the hydrophilic part of the molecule. The 'tail' ends of the fatty acid chains opposite the glycerol is the hydrophobic part of the molecule
The most important function for a phospholipid is to form the phospholipid bilayer. In this bilayer, the phospholipids are arranged so that all the hydrophillic heads are pointing outward and the hydrophobic tails are pointing inward. This arrangement comes about because the areas both outside and inside your cell are mostly water, so the hydrophobic tails are forced in.
THis is the required answer.
It's the sodium ion.
When a neural impulse is fired in both neurons, it is always cause by an excited electron in one neuron moving to the other neuron to destabilize the balance of ions trying to keep them at equilibrium. This action either depolarizes or hyper-polarizes the membrane. If it does, then sodium ions--the key deficient ones--can flow into that region of low charge and maintain that state of low charge, keeping the cell membrane stable.
Answer:
A. BY, or YB
Explanation:
This question is depicting a phenomenon in inheritance called CODOMINANCE, which is a type of non-mendelian inheritance in which two alleles of a gene both express themselves in that gene. In this question, the allele for blue color (B) is codominant with the allele for yellow color (Y).
This means that an individual that has a blue phenotype will possess the genotype BB while an individual that has a yellow phenotype will possess the genotype YY. Hence, in an heterozygous state in which both alleles combine to produce a simultaneous blue and yellow phenotype, the genotype will be BY or YB.
Answer:
The correct answer is 3: "<em>High levels of Ca2+ are expected to be found </em><em>within the sarcoplasmic reticulum</em>".
Explanation:
Muscular contraction is a highly regulated process that depends on free calcium concentration in the cytoplasm. Amounts of cytoplasmic calcium are regulated by <u>sarcoplasmic reticulum</u> that functions as a storage of the ion.
When a nerve impulse reaches the membrane of a muscle fiber, through acetylcholine release, the membrane depolarizes producing the entrance of calcium from <u>extracellular space</u>. The impulse is transmitted along the membrane to the sarcoplasmic reticulum, from where calcium is released. At this point, <em>tropomyosin is obstructing binding sites for myosin on the thin filament</em>. The calcium channel in the sarcoplasmic reticulum controls the ion release, that activates and regulates muscle contraction, by increasing its cytoplasmic levels. When <em>calcium binds to the troponin C</em>, <em>the troponin T alters the tropomyosin by moving it and then unblocks the binding sites,</em> making possible the formation of <em>cross-bridges between actin and myosin filaments.</em> When myosin binds to the uncovered actin-binding sites, ATP is transformed into ADP and inorganic phosphate.
Z-bands are then pulled toward each other, thus shortening the sarcomere and the I-band, and producing muscle fiber contraction.
