Question

which statement about the plasma membrane is incorrect?* 1 point
it is selectively permeable.
it is composed of two layers of glycoprotein molecules.
it contains receptors for specific signalling molecules.
the plasma membranes of adjacent cells are held together by desmosomes.
what is the name of the \active\ mechanism that ensures that there is a 1 point
higher concentration of sodium ions in the extracellular fluid than in the
intracellular fluid?
facilitated diffusion
the sodium - potassium pump
secondary active transport
osmosis

Explanation:

For the first question:

• The plasma membrane is selectively permeable.
• It contains receptors for specific signaling molecules.
• Desmosomes hold adjacent cells' plasma membranes together.
• But it is composed of two layers of phospholipid molecules (not glycoprotein molecules).

For the second question:

• Facilitated diffusion and osmosis are passive processes.
• Secondary active transport is not the main mechanism for maintaining sodium gradient.
• The sodium - potassium pump (an active transport mechanism) actively transports sodium out of the cell to maintain a higher extracellular sodium concentration.

Answer:

First question: It is composed of two layers of glycoprotein molecules.
Second question: The sodium - potassium pump.