The Cell Membrane a.k.a. Plasma Membrane

1
The Cell Membrane a.k.a. Plasma Membrane

• Biology 11

2
The Cell Membrane

• The living cell has to maintain an internal
  balance. (homeostasis)
• The plasma membrane is selectively permeable it
  allows some substances to cross membrane but
  blocks others.

3
The Fluid Mosaic Model
4
Phospholipids

• The plasma membrane is made of 2 layers of
  phospholipids.
• Phospholipids have a phosphate group head
  attached to a lipid tail. The head is
  hydrophilic (water loving) and the tail is
  hydrophobic (water hating).
• The tails always face inward to avoid contact
  with the water inside and outside of the cell.

5
Chemistry of a Phospholipid
6
A Fluid Membrane

• There are no chemical bonds between the
  phospholipid molecules they are free to move
  around laterally.
• Proteins are found throughout the plasma membrane
  that can also move around, like icebergs in a sea
  of phospholipids ?

7
Membrane Carbohydrates

• Carbohydrates can also be attached to the outer
  surface of the plasma membrane.
• Carb. attached to a phospholipid glycolipid
• Carb. attached to a protein glycoprotein

8
Membrane Animations

• Cell Membrane Tutorial!
• Kirk Animation!

9
Video

• http//learning.aliant.net/index2.asp
• mcobb_at_staff.ednet.ns.ca
• 488KCH

10
Reading Review

• Lets Read!!!

11
Cell Transport

• Solution Types
• See pages 52-53

12
Definitions

• Two parts of a Solution
• Solute
• Solvent

13
Osmosis

• The diffusion of water across a semi-permeable
  membrane.
• Animation

14
Isotonic

• A solution that has the same concentration of
  solutes as the cell.
• Therefore there is no net movement of water
  molecules.

15
Hypotonic

• A solution that has a lower concentration of
  solutes than the cell.
• There will be a net movement of water into the
  cell.

16
Hypertonic

• A solution that has a greater concentration of
  solutes than the cell.
• There will be a net movement of water out of the
  cell.

17
Red Blood Cells

• Cytolysis The bursting or rupture of a cell.

18
Q.O.T.D.

• Q Why cant doctors find a cure for the flu
  virus?
• A Influenza is a tricky customer!
• Viral ? not bacterial
• RNA virus ? not DNA

19
How flu viruses are classified
20
Plant Cells
21
Q.O.T.D.

• Q Are red blood cells alive?
• A
• Mature RBCs lack a nucleus all organelles
  (such as mitochondria, golgi etc)
• Do not have DNA, therefore cannot build protein
• Do not respire
• Limited repair abilities
• Only last 100-120 days
• FYI
• Humans have 20-30 trillion RBCs!
• Each RBC contains 270 million
• molecules of hemoglobin!

22
Passive vs. Active Transport

• Biology 11

23
Passive Transport

• Passive Transport Movement of materials across
  the cell membrane going with the concentration
  gradient (from a region of greater concentration
  to a region of lesser concentration).
• Cell uses no energy to transport particles!

24
Passive transport examples

• a) Osmosis specific type of diffusion (can you
  remember the definition??)
• b) Facilitated diffusion Process by which
  molecules diffuse across a cell membrane with the
  aid of transport proteins. This is for particles
  that cannot dissolve into the lipid bi-layer or
  are too large to pass through.

25
Active Transport

• Molecular Active Transport Movement of
  materials across the cell membrane going against
  the concentration gradient (from a region of
  lesser concentration to a region of greater
  concentration).
• Requires energy from cell!

26
Active transport cont

• Molecular active transport involves protein
  pumps.
• Examples of active transport
• Cells in Gills of marine fish actively pump out
  salts.
• Root cells of plants often take in large
  quantities of ions.

27
Bulk Membrane Transport

• Active transport (requires energy)
• Two types
• Endocytosis
• Exocytosis
• Animation

28
Endocytosis

• Endocytosis The process by which the plasma
  membrane engulfs and takes in substances from a
  cells environment. Common in unicellular
  organisms.
• 2 types
• i) Phagocytosis Form of endocytosis in which
  large solid particles are taken into the cell.
  Example WBCs engulfing harmful bacteria
• ii) Pinocytosis Form of endocytosis in which
  small liquid droplets are taken into the cell.
  a.k.a. cell drinking

29
Exocytosis

• Exocytosis Cell products or wastes are enclosed
  in vesicles and released to outside of cell.
• Reverse process of endocytosis.
• Examples secretion or elimination of waste

30
Lets Review

• Vocabulary Review
• Diagram Review

31
Test 2 Thursday April 7th

• Chemistry of the Cell (pages 32-42 class notes)
• Organic compound (definition)
• Proteins, Carbohydrates and Lipids
• Links to cell organelles
• Cell Transport (Pages 47-57 class notes)
• Structure and function of the cell membrane
• Osmotic solutions
• Active / passive transport
• Bulk membrane transport

32
Q.O.T.D.

• Q How intelligent is an octopus?
• A Lets see ?