Answer:
Its A
Explanation:
It takes about 4 years for light from this star to reach earth. Depends on the the Distance of the star. As our sun is 149.6 million km away from the Earth it takes total 8 minutes 20 seconds.
It takes light 8 minute to reach from surface of sun to earth.
However, light produced in the core of the sun takes thousands to millions of years to get to the surface.
A light-year is the distance light travels in one Earth year. One light-year is about 6 trillion miles (9 trillion km).
Answer:
A useful model for enzyme action is the Lock and Key model.
Explanation:
The Lock and Key model or theory was first postulated by <u>Emil Fischer</u> in 1894. It is used to represent the enzyme and its specific substrate. The enzyme (lock) is specifically activated by the substrate (key) through its active site (key hole) to produce a catalyzed reaction. If the keys are too small or too big for the key hole, it will not produce any reaction.
The Double Helix model by Watson and Crick is used to represent the DNA present in an individual. This is made up of <u>two strands of DNA</u> bounded by hydrogen bonds. In between these bonds are nitrogenous bases <u>adenine (A), guanine (G), thymine (T), and cytosine (C).</u>
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The Ball and Socket model represents body joints, specifically the hip and the shoulder joints. The shape of the <u>head of the joint is spherical</u> and <u>fits into a cup-like depression of the receiving bone</u>. The <u>range of motion </u>of this joint is usually <u>wide</u> and has <u>one central point</u>.
The Amino Acid Chain model, also known as polypeptides, are linked together by a <u>peptide bond</u>. A peptide bond is produced by hydrolysis. The chain usually <u>starts with the amino group and ends with the carboxyl group</u>.
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The answer is <span>B.a wildfire breaks out in a forest, removing all remaining shelters for tree squirrels
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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)
<span> How does pulmonary circulation work? In my example below, we will start with the blood not reaching the heart yet. The heart beats around 75 beats a minute. Deoxygenated blood is in the veins, going to the heart. Note that veins will always carry deoxygenated blood, excluding the pulmonary veins. The deoxygenated blood goes into the heart through the superior or inferior vena cava, and goes into the right atrium. It then gets pumped into the right ventricle, and gets pumped through the pulmonary arteries to the lungs to get oxygenated. The blood, now oxygenated, comes back to the heart through the pulmonary veins, into the left atrium. The blood gets pumped from the left atrium to the left ventricle, where it gets pumped through the aorta to all of the body systems. The red blood cells travel through capillaries, which is where most of the gas exchange occurs between body cells and red blood cells. Red blood cells have no nuclei. When the red blood cells are no longer red, but blue due to lack of oxygen, they go back to the heart to get pumped to the lungs, and enter the heart through the superior or inferior vena cava. The cycle starts over. Just like the veins, arteries always carry oxygenated blood, excluding the pulmonary arteries. Also, the right side of the heart will have deoxygenated blood, or blue blood, and the left side of the heart will have oxygenated blood. </span>
