Which of the following solutes moves by simple diffusion

Which of the following solutes moves by simple diffusion? [mark all correct answers] a. carbon dioxide b. estrogen c. glucose d. oxygen e. steroids Check Answer

The correct answer and explanation is:

The correct answers are:
a. Carbon dioxide
b. Estrogen
d. Oxygen
e. Steroids

Explanation:

Simple diffusion is a passive transport mechanism where molecules move from a region of higher concentration to a region of lower concentration without the need for energy or the assistance of transport proteins. Simple diffusion occurs through the phospholipid bilayer of the cell membrane, and the ability of a substance to pass through depends on factors like its size, polarity, and solubility in lipids.

1. Carbon dioxide (CO2): CO2 is a small, nonpolar molecule that can easily pass through the lipid bilayer. Since it is small and nonpolar, it can diffuse across the membrane without the need for a transport protein.
2. Estrogen: Estrogen is a steroid hormone that is lipid-soluble. Lipid-soluble substances easily diffuse across the hydrophobic lipid bilayer, making estrogen capable of moving through the membrane via simple diffusion.
3. Oxygen (O2): Like carbon dioxide, oxygen is a small, nonpolar molecule that can diffuse across the lipid bilayer. Its nonpolarity allows it to pass easily through the cell membrane without the need for transport proteins.
4. Steroids: Steroids are also lipid-soluble molecules. Being hydrophobic, they can dissolve in the lipid bilayer and diffuse across the membrane. This includes both synthetic steroids and natural steroid hormones like cortisol and testosterone.

On the other hand, glucose is a polar molecule and relatively large. It cannot diffuse across the membrane via simple diffusion. Instead, it requires facilitated diffusion, where specific transport proteins like GLUT (glucose transporter) help it pass through the membrane.

The ability of these substances to move by simple diffusion is governed by their physical and chemical properties, which determine their ease of movement across the cell membrane.