1. C e l l M e m b r a n e Homeostasis Lipid Bilayer Membrane Proteins
Structure
Barrier
Membrane Proteins
Proteins in Lipids
Types of Proteins

2. Homeostasis
Maintenance of stable internal conditions in a changing environment.
Must maintain
homeostasis
to live

3. Homeostasis All living things respond to their environment.
How do you respond to hot weather? Cold weather?

4. H o m e o s t a s I s
Cells maintain by controlling movement across cell membrane
Some materials allowed through; others not = gatekeeper

5. Cell membrane

6. Structure Lipid bilayer Barrier
Sea of phospholipids
Phosphate “head” = Polar = charge at each end, likes h20
two fatty acid “tails”= nonpolar = ????????

7. Lipid bilayer
Barrier ~ only small, nonpolar substances can pass

8. Membrane proteins

9. Membrane proteins Some. . . Face outside Face inside
Stretch across and face both ways
~Polar portion attracted to water on either side
~Non polar portions attracted to interior

10. Membrane proteins
Cell-surface markers
“name tag”
Chain of sugars (carbohydrates)
Attached to surface by
glycoproteins  (proteins attached to Carbohydrate, help cells work together)

11. Membrane proteins Enables sensing Once it of binds, this surroundings
Receptor proteins
Enables sensing of
surroundings
by binding to
substances
outside cell
Receptor proteins
Once it
binds, this
causes
changes to
occur
inside cell

12. Membrane proteins
Enzymes
Assist w/
chemical
rxns inside cell

13. Membrane proteins Aid in the mvmt of substances in & out of cell
Transport proteins
Aid in the mvmt of
substances in & out of cell
Why do some substances need help moving thru the membrane?
Only small, nonpolar substances can pass. The nonpolar middle repels any polar & large substances!