The cell membrane is composed of a phospholipid bilayer containing proteins and carbohydrates. Choose ALL of the statements that accurately reflect the structure and its function.

1. Membrane proteins may be enzymes to catalyze metabolic reactions within the cell.

2. Membrane proteins may contain cholesterol to serve as identification tags for other cells.

3. Channel proteins allow a specific molecule to cross the cell membrane that is unable to cross the
phospholipid bilayer unassisted.

4. Receptor proteins bind to ligands, initiated cell signaling pathways.

5. Molecules that are large or nonpolar must use membrane proteins for transport

The believe that the 2 answer choices are 1 and 3

option 1,3, and 4

-Membrane proteins may be enzymes to catalyze metabolic reactions within the cell.

-Channel proteins allow a specific molecule to cross the cell membrane that is unable to cross the phospholipid bilayer unassisted.

-Receptor proteins bind to ligands, initiated cell signaling pathways.

Explanation:

I did the assignment on USATestprep and got them right.

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explanation:

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answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.