Some substances can cross the cell-surface membrane of a cell by simple diffusion through the phospholipid bilayer. Describe other ways by which substances cross this membrane.

Other ways that substances can cross the plasma membrane include facilitated transport, where molecules or ions must interact with a channel/carrier protein to be transported across the membrane, down a concentration gradient, which doesn't require energy. Another method is active transport, where molecules are moved via protein pumps, which requires energy in the form of ATP, and which may move up a concentration gradient. In addition, water may move across membranes via osmosis, from high to low water potential, via aquaporins or water channels. Alternatively, substances contained within vesicles may exit the cell via fusion of the vesicular membrane with the plasma membrane, leading to the release of its contents to the extracellular space. Extracellular material may also enter the cell via phagocytosis, which involves the cell membrane surrounding and engulfing the substance, to form an intracellular vesicle or vacuole.

Answered by Sophia H. Biology tutor

18348 Views

See similar Biology A Level tutors

Related Biology A Level answers

All answers ▸

What are the risks and benefits concerning genetic modification of crops?


Why do humans have a double circulatory system?


How are glucose molecules absorbed in the gut?


a) Explain how an action potential is passed across a synapse b) Label the graph below with the steps of action potential generation c) The graph shows the results of a study on two groups taking different medication, is the difference significant?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences