Answer:
A, the sun.
Explanation:
The sun powers the water cycle and many others.
Answer:
response to stimuli / tropism
Explanation:
The plants and animals always respond to stimuli. It is an innate character of all living things. When a bright light falls on the eye, it closes immediately. This is responding to the stimuli. When someone touches the leaves of touch-me-not plants it closes its leaves due to the external stimuli.
The plants respond to the light. Because it does photosynthesis in the presence of light. Therefore, the leaves and branches of the plants always bend towards the light. This process is called phototropism.
Similarly, the roots of the plants move towards gravity under the ground. This is called geotropism.
Besides phototropism and geotropism, other types of stimuli are there - hydrotropism(response to the water), chemotropism(response to certain chemicals).
That's why the plants growing on the windowsill move towards outside where light comes.
The goal of the Voyager project was A: to explore the moon.
Answer:
E) Improve membrane fluidity
Explanation:
Cholesterol constitutes the basic structural element of the skeleton of cell membranes. Without their reinforcement, the membranes would become extremely fluid and lose their consistency. Cholesterol is found in the esterified membranes in its hydroxyl group (OH): with fatty acids, mainly oleic and linoleic, or as cholesterol sulfate. The cholesterol-sulfate polar group is disposed on one of the faces of the membrane that interacts with other polar groups in that area, while its bulky hydrophobic portion is embedded between the apolar parts of the lipids that form the membrane skeleton and They fulfill many other functions, among which the reduction in the permeability of protons and sodium ions, and their participation in signal transmission. Cholesterol is also essential in phagocytosis processes carried out by cells to capture many nutrients and, in general, for the function of cleaning up organic waste produced by macrophages.
The membranes must have a fluid structure so that the integrated proteins can move "horizontally" to interact with their ligands and with other proteins. The fluidity is given by unsaturated fat. With the excess of saturated fat, the membranes become rigid, but only with the necessary unsaturated fat the membranes are extremely fluid and very sensitive to temperature changes. Cholesterol stabilizes the structure of the membranes; In order for them to have the correct structure, they must have the correct proportions of saturated, unsaturated fats and cholesterol. The membranes produced in the laboratory without cholesterol are unstable to temperature changes, drastically modifying their fluidity against the small temperature changes that occur in the physiological range.
In addition to its functions in cell membranes, cholesterol is an important product that metabolism uses as a raw material to make other compounds:
*Bile salts
*Sex hormones
*Hormones of the adrenal cortex (corticosteroids)
*Vitamin D (Calciferol)
