Question

small lipids like short-chain fatty acids water (H20) electrolytes (K+, Na+, Cl-) small peptides small carbohydrates like glucose (C6H12 06)

Answer 1

Answer:

Small lipids like short chain fatty acids.

Explanation:

- Simple diffusion is a passive transport (no energy required) in which molecules move from area of higer concentration to area of lower concentration.

- Cell membrane is a semipermeable (selectively permeable) lipid bilayer that contains protein molecules in between. Thus, fat soluble (lipophilic or non-polar or hydrophobic) molecules like alcohol, fatty acids and oxygen can easily diffuse across the cell membrane. Hydrophilic (polar or ionic) molecules like urea, glucose cannot pass easily across the cell membrane.

- Thus, small lipids like short chain fatty acids can easily pass across the cell membrane by simple diffusion as they are fat soluble, non polar, lipophilic molecules.

- Small carbohydrates like glucose are water soluble (hydrophilic or polar) hence not transported across the cell membrane by simple diffusion.

- Molecules like water and small peptides and ions like Na+, K+, Cl- are polar hence cannot be transported by simple diffusion across cell membrane.