substances that can pass through cell membranes by diffusion include?
oxygen
Substances that can pass through cell membranes by diffusion include:
1. Small non-polar molecules: Small molecules that are hydrophobic (water-insoluble) and non-charged can easily diffuse through cell membranes. Examples include oxygen (O2), carbon dioxide (CO2), and lipid-soluble vitamins (such as vitamins A, D, E, and K).
2. Water: While water molecules are polar, they can diffuse through cell membranes via a process called osmosis. This occurs due to the presence of special water channels called aquaporins in the membrane.
3. Lipids: Lipid-soluble substances, such as steroids and some hormones, can diffuse through the cell membrane due to their ability to dissolve in the lipid bilayer.
4. Small uncharged molecules: Some small uncharged polar molecules, such as ethanol (alcohol) and urea, can diffuse through the cell membrane to some extent.
5. Gases: Gases, such as nitrogen (N2) and carbon monoxide (CO), can freely diffuse through the cell membrane due to their small size and non-polar nature.
It's important to note that the ability to diffuse across the cell membrane also depends on factors like concentration gradients, membrane permeability, and the presence of transport proteins.
Substances that can pass through cell membranes by diffusion include small, nonpolar molecules. Here's how you can determine this information:
1. Understand the concept of diffusion: Diffusion is the spontaneous movement of particles from an area of higher concentration to an area of lower concentration. It occurs due to the random motion of particles.
2. Learn about the composition of the cell membrane: The cell membrane is composed of a phospholipid bilayer, which consists of two layers of phospholipids. Each phospholipid has a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail.
3. Consider the nature of substances that can freely diffuse: The cell membrane is selectively permeable, meaning it allows only certain substances to pass through easily. Diffusion across the cell membrane primarily depends on the characteristics of the substance, such as size, charge, and polarity.
4. Focus on small, nonpolar molecules: Small, nonpolar molecules, such as oxygen (O2), carbon dioxide (CO2), and lipids (fats), can freely diffuse across the cell membrane. These molecules are hydrophobic and can easily pass through the hydrophobic region of the phospholipid bilayer.
It's important to note that larger molecules, charged ions, and polar molecules have difficulty crossing the cell membrane through simple diffusion and require specialized transport mechanisms like facilitated diffusion or active transport.