Notes on the plasma membrane for Imperial College London's 1st year cell biology module from the Biochemistry BSc course, with summary notes for each learning outcome.
First year material from the plasma membrane chapter
January 26, 2021
6
2019/2020
Summary
Subjects
plasma membrane
phospholpid
phospholipid bilayer
membrane fluidity
amphiphilic
membrane proteins
membrane
proteins
channel proteins
cholesterol
hydration shell
flippases
micelle
bilayer
cytoskeleton
l
Connected book
Book Title:
Author(s):
Edition:
ISBN:
Edition:
More summaries for
Molecular Biology of The Cell, 7th Edition
Summary Molecular Biology of the Cell 2 (book) (WBFA007-04)
Summary Regenerative Medicine
All for this textbook (62)
Written for
Imperial College London (ICL)
Imperial College London
Cell Biology
All documents for this subject (1)
Seller
Follow
BioChemBeebs
Content preview
The Plasma Membrane
Learning outcomes:
How are membranes used by cells?
What are cell membranes made of?
What is an amphipathic lipid and how does its structure influence the properties of cell
membranes?
What are some roles that water plays in cell membrane function?
Are membrane lipids static? How can they move?
How can the lipid composition of cell membranes change with temperature?
How can a cell use membrane lipid asymmetry?
How can membrane proteins associate with the plasma membrane?
What is the significance of hydrophobic stretches in transmembrane proteins?
What is glycosylation and what are some functions of membrane protein glycosylation?
How are membranes used by cells?
Defines the boundaries around and within the cell – separates ICF and ECF
e.g. lipid bilayer prevents free movement of charged ions into the cell – movement
of ions regulated by hydrophilic protein channels
Maintains essential differences between cytosol and ECF – concentration gradients
e.g. sodium-potassium pump creates EC gradient – needed for depolarisation
Maintains essential differences between cytosol and environment inside organelles
e.g. proton gradient between mitochondrial membranes – needed for ATP synthesis
Involved in cell adhesion, cell signalling
Used as an attachment surface for cytoskeleton and ECM
What are cell membranes made of?
All biological membranes have a common general structure: lipid bilayer with membrane
proteins
The lipid bilayer: Basic structure for all cell membranes
Membrane proteins: determine cell membrane characteristics, perform specific tasks, vary
in structure and in association with the lipid bilayer
, What is an amphipathic lipid and how does its structure influence the properties of cell
membranes?
Amphipathic: a molecule which contains both a hydrophilic part and a hydrophobic part
Amphiphilic: a molecule which contains both a hydrophilic part and a hydrophobic part
(Amphipathic and amphiphilic are interchangeable)
All the lipid molecules in cell membranes are amphiphilic:
e.g. phospholipids (most abundant membrane lipid) have:
Hydrophilic head group containing a phosphate group
2 hydrophobic hydrocarbon tails
Hydrocarbon tails (usually fatty acids in animal, plant & bacterial cells):
Differ in length (normally 14-24 C atoms)
One tail typically has 1+ CIS double bond – kink in chain
Structure Properties Why?
Amphipathic nature Phospholipid bilayer Hydrophobic tails aggregate together to shield
spontaneously forms from water, hydrophilic heads exposed to water.
Bilayer > dispersed because dispersed
phospholipids force adjacent water molecules to
reorganize into ice-like cage structures around
the molecule. More ordered, entropy decreases,
free energy increases ∴ not feasible. If
Hydrophobic tails cluster together, free-energy
cost minimized because number of water
molecules that become more ordered decreases.
Sealed compartment Free edges in bilayer energetically unfavorable
spontaneously forms (results in ordering of water molecules). Bilayer
closes in on itself to avoid having free edges
forming sealed compartment
2 hydrocarbon tails Bilayer > micelle Micelle forms when amphiphilic molecule is cone-
shaped (i.e. head attached to one HC tail), bilayer
forms when amphiphilic molecule is cylindrical
(i.e. “ “ 2 HC tails).
Variable Longer tail = less fluid Longer tails (more C atoms in chain) form
length/saturation of membrane and VV stronger VDW interactions because there is a
hydrocarbon tails greater surface area for lipid tails to interact.
More C=C bonds = More double bonds (more kinked chain) means
more fluid membrane lipids don’t pack together as closely, weaker VDW
and VV interactions form.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller BioChemBeebs. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $8.49. You're not tied to anything after your purchase.
