Answer:
"As a molecule moves through the plasma membrane it passes through <em>a hydrophilic layer of phospholipid heads then a hydrophobic layer of phospholipid tails and then another hydrophilic layer of phospholipid heads".</em>
Explanation:
Biological membranes are formed by two lipidic layers, proteins, and glucans.
Lipids characterize for being amphipathic molecules, which means that they have both a hydrophilic portion and a hydrophobic portion at the same time. These molecules have a lipidic head that corresponds to a negatively charged phosphate group, which is the polar and hydrophilic portion. They also have two lipidic tails that correspond to the hydrocarbon chains -the apolar and hydrophobic portion- of the fatty acids that esterify glycerol.
Membrane lipids are arranged with their hydrophilic polar heads facing the exterior and the interior of the cells, while their hydrophobic tails are against each other, constituting the internal part of the membrane.
Through this lipidic bilayer, some molecules can move from one side of the cell to the other, which happens because of concentration differences. When this occurs, molecules must pass through the hydrophilic layer of phospholipid heads then through the hydrophobic layer of phospholipid tails and then again through another hydrophilic layer of phospholipid heads.
Tentacles of an octopus as well limbs of a lizard are analogous structures.
Analogous structures or organs perform the same function in different organisms that bear no resemblance to each other anatomically. Analogous structures are formed as a result of convergent evolution, i.e. different structures evolving for the similar function and thus having similarity. Tentacles of an octopus as well as limbs of a lizard are used for the similar function, i.e. locomotion in this case.
On the other hand, homologous structures result from divergent evolution. Homologous organs contain a similar basic structure but perform distinct functions in different organisms.
To learn more about Homologous organs here
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Chemical weathering is caused by rain water reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts. These reactions occur particularly when the water is slightly acidic.
Answer:
That would be option D. A motor.
Explanation:
