Cells and Organelles;
The Cell Membrane
Book Reference: p.16-p.19
Do all membranes have the
same basic structure?
• Both the cell surface
membrane and the
membranes
surrounding certain
organelles have the
same basic structure.
Much of the
membrane is made up
of a 'sea' of
phospholipids with
protein molecules
'floating' in between
the phospholipids.
Where are proteins located
within the membrane?
• What is an
intrinsic
protein?
• What is an
extrinsic
protein?
• Why is it called
the fluid mosaic
model?
INTRINSIC 1:
Channel Proteins
• Allow movement
of substances,
such as glucose,
across the
membrane
• NO ATP
REQUIRED
INTRINSIC 2:
Carrier Proteins
• Actively
transport
substances, such
as minerals,
across the
membrane
• ATP is
REQUIRED
(a) Channel
VS
(b) Carrier
Proteins
Bilayer; Phospholipids
• What is the
bilayer?
• The phosphate
heads are polar
molecules and so
are water-soluble.
• The lipid tails are
non-polar and
therefore are not
water-soluble.
Why do phospholipids have
both a hydrophilic and a
hydrophobic part?
• The phosphate
heads are polar. Are
they water-soluble?
• The lipid tails are
non-polar. Are they
water-soluble?
What is a
polysaccharide?
• Clue: polymer;
monomer;
carbohydrate
• What is the
difference
between a
glycoprotein and a
glycolipid?
Glyco……what?
What is the role of
glycoproteins?
• They may help in
the recognition of,
and interaction
with, other cells.
They may also play
a part in the
recognition of
hormones and
foreign molecules.
What is the role of
cholesterol in the cell
membrane?
• Cholesterol is also
present in the
membrane. It
maintains the fluidity
and increases the
stability of the
membrane. Without
cholesterol the
membrane would easily
split apart
Cell membrane: Functions
1. Selectively permeable barrier.
2. Structural, keeping the cell contents
together.
3. Allows communication with other cells.
4. Allows recognition of other external
substances.
5. Allows mobility in some organisms, e.g.
amoeba.
6. The site of various chemical reactions.
Cells and Organelles;
Tissues
•
•
•
•
Some organisms do exist as
single cells - for example,
Amoeba,
but many organisms are
multicellular and consist of
from hundreds to billions of
cells.
The functions of the organism
are divided up amongst the
groups of cells, which become
specialised for particular
roles.
Specialised cells show division
of labour by being grouped
into tissues.
What is a Tissue?
Definition
• A tissue is defined as
a collection of cells,
together with any
extracellular
secretion, that is
specialised to perform
one or more particular
function. Tissues may
contain only one type
of cell, or several
types.
Website Reference:
www.s-cool.co.uk
go to Biology and then:
1.Cells and Organelles
2.Gas Exchange
3.Transport
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