MYTUTOR SUBJECT ANSWERS

383 views

What are the functions of the cell membrane?

The cell membrane separates the intracellular and extracellular environments. The lipid bilayer only allows small polar molecules (such as O2 or CO2), small hydrophobic molecules (fatty acids, steroid hormones) and water to cross. However charged ions and molecules, and large molecules (including proteins) cannot just diffuse across the membrane; they can only be transported across by other cellular mechanisms. They can be allowed to cross by a specific membrane protein. e.g. a glucose transporter protein makes the membrane selectively permeable to glucose. This means that molecules and ions can be at different concentrations inside and outside the cell, allowing gradients across the membrane (this is important in neurones for example). The cell membrane also helps to communicate extracellular signals into the cell, usually via a sequence of interactions between different proteins, known as ‘signalling pathway’. Specific enzymatic modification of some of the lipids in cell membranes can transmit a signal into a cell. Membrane proteins can be receptors for an extracellular signal such as a protein (growth factor) or hormone (insulin). Activation of a receptor in the membrane activates a signalling pathway inside the cell. Components of cell membranes allow cell-cell recognition; e.g. sperm and egg recognition in fertilisation. In prokaryotic cells, which do not have intracellular organelles, the cell membrane is an important environment for the necessary reactions of the cell, e.g. the electron transport chain.
Francesca D. A Level Biology tutor, GCSE Biology tutor, A Level Chemi...

9 months ago

Answered by Francesca, an A Level Biology tutor with MyTutor


Still stuck? Get one-to-one help from a personally interviewed subject specialist

158 SUBJECT SPECIALISTS

£20 /hr

Bethan P.

Degree: Biochemistry (Bachelors) - Bristol University

Subjects offered:Biology

Biology

“I hope to inspire students to work a passionate attitude and facilitate their learning and development.”

MyTutor guarantee

£24 /hr

Benjamin W.

Degree: Medicine (Bachelors) - Oxford, Balliol College University

Subjects offered:Biology, Science+ 9 more

Biology
Science
Maths
Human Biology
History of Art
Chemistry
.UKCAT.
.BMAT (BioMedical Admissions)
-Personal Statements-
-Medical School Preparation-

“I am a friendly first year medical student studying at Oxford University, and having a fantastic time! I have always been interested in science, in particular human biology (the heart and the brain are my favourites) to A-level standa...”

£20 /hr

Oliver G.

Degree: Chemistry with Medicinal Chemistry (MChem) (Masters) - Newcastle University

Subjects offered:Biology, Chemistry

Biology
Chemistry

“My name is Oliver. I'm a third-year chemistry student and I'm ready to help you improve your grades.”

MyTutor guarantee

About the author

Francesca D.

Currently unavailable: for new students

Degree: Molecular and Cellular Biochemistry (Masters) - Oxford, Oriel College University

Subjects offered:Biology, Science+ 2 more

Biology
Science
Maths
Chemistry

“Hello! I have just finished my undergraduate Master’s degree in Biochemistry at the University of Oxford. In October, I will be starting a DPhil researching a treatment for Ebola (I’m very excited!). My passion for science came from so...”

MyTutor guarantee

You may also like...

Posts by Francesca

What are the functions of the cell membrane?

What is a pathogen?

Other A Level Biology questions

What is meant by the phrase saltatory conduction?

What is the difference between competitive and non-competitive inhibition of enzymes?

What different forms of RNA are found in a cell and what are their functions?

How is the structure of alveoli suitably adapted for efficient gas exchange?

View A Level Biology tutors

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this. Dismiss

mtw:mercury1:status:ok