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.
after the evolution of the first living cells, fermentation wasn't needed, because aerobic respiration was now doable, since there was more oxygen in the air now. also, as the temperature increases, it becomes more energy consuming to conduct fermentation over aerobic respiration.
Hope this helps :)
The correct answer is - C. -1.9 C degrees.
The sea ice in the polar oceans needs little lower temperatures to start forming than what it would need if it was't forming on a saline water. The freshwater starts freezing as the temperature goes bellow 0 C degrees, but that is not the case with the saline water. The saline water, because of the salt that prevents the freezing to a certain point, needs temperature of -1.9 C degrees to start freezing. Once this temperature is reached, the salt can not prevent the freezing anymore, so the water on the polar oceans starts to freeze.
Answer:
a maybe correct me if im wrong
