Related to selective permeability

• The bimolecular phospholipid layer acts as a barrier to water soluble molecules such as glucose or amino acids , lipids soluble molecules can dissolve in the membrane
• Proteins in the membrane form channels or act as carriers to transport such molecules , these channels are selective due to specific shape and size
• Diffusion that occurs aided by protein channels and carriers is called facilitated diffusion
• Active transport using ATP from respiration allows movement against a concentration gradient , enzymes catalyse the reactions of active transport
• Cholesterol in the membrane affects its permeability and fluidity , it stabilises the membrane
• Unsaturated fatty acids ( less hydrogen ) increase permeability