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.
Answer:
Alcohol fermentation
Explanation:
When oxygen availability is low, the cell can't perform aerobic respiration to breakdown glucose. Instead, anaerobic respiration must be performed. This occurs in cells which consume large amounts of energy, such as muscle cells. Anaerobic respiration produces much less energy than aerobic respiration
One type of anaerobic respiration formed by yeast is called alcohol fermentation (also called ethanol fermentation). This begins with glycolysis, where one molecule of glucose is broke down into 2 molecules of pyruvate. The energy from this reaction generates 2 molecules of ATP, and converts NAD+ to NADH.
Then, the two molecules of pyruvate are further broke down into 2 acetaldehydes (releasing two molecules of carbon dioxide as a by-product). These two molecules of acetaldehyde are then converted into tw molecules of ethanol, using the H ions from NADH, converting it back to NAD+. See the attached picture
This process is taken advantage of to brew beer and wine.
Emperor penguins have the ability to 'recycle' their own body heat. The arteries and veins lie close together so that blood is pre-cooled on the way to a penguin's feet, wings and bill and warmed on the way back to the heart. Emperors' feet are adapted to the icy conditions
Answer:
Pineal gland
Explanation:
The suprachiasmatic nucleus is the paired nucleus made of about 1000 neurons each in the hypothalamus. The suprachiasmatic nucleus is involved in maintaining the endogenous clock or the internal clock.
The suprachiasmatic nucleus controls the circadian rhythm by controlling the amount of melatonin. The melatonin is produced by the pineal gland from the serotonin and tryptophan precursors. The hypothalamus thus controls the amount of the melatonin by regulating the pineal gland.
Thus, Pineal gland is the correct answer.
