Answer:
B. The membrane lets certain substances move across it freely, while others must move through a “gate”.
Explanation:
Selective permeability is a property of cellular membranes that only allows certain molecules to enter or exit the cell. This is important for the cell to maintain its internal order irrespective of the changes to the environment. For example, water, ions, glucose and carbon dioxide may need to be imported or exported from the cell depending on its metabolic activity. Similarly, signaling molecules may need to enter the cell and proteins may need to be released into the extracellular matrix. The presence of a selectively permeable membrane allows the cell to exercise control over the quantum, timing and rate of movement of these molecules.
Everything in the universe was created when the Big Bang occurred and the universe is expanding
First one is A
Second one is B
Hope this helps !
<span>If it loses that 1 electron (0 electrons, 1 proton, 1 neutron) it become an ion that is positively charge because it has more protons than electrons. [Ignore the neutrons] </span>
<span>If it gains an electron (2 electrons, 1 proton, 1 neutron) it becomes an ion that is negatively charge because it has more electrons than protons </span>
<span>A molecule - when 2 or more "different" elements combine or when 2 or more of the "same" elements combine </span>
<span>1 proton 1 electron <----- that is considered to be neutral </span>
<span>3 protons, 3 electrons <----- neutral </span>
<span>5 protons 5 electrons <----- neutral </span>
<span>6 protons, 5 electrons <-- positive ion [more protons than electrons] </span>
<span>5 protons, 8 electrons <--- negative ion [more electrons than protons] </span>
It is always necessary to analyze research for bias
