Download Cell Boundaries

Chapter 7-3
Cell Boundaries
Part 1 (of 4)Notes
I. Cell Membranes: ALL cells have one!
A. Outer boundary of the cell
B. Functions
1) Separates a cell from other cells
2) Protection and support
3) Controls what enters and exits the cell
to maintain homeostasis
C. Structure: MOSTLY A LIPID BILAYER, with proteins and carbs
scattered throughout.
1) 2 layers of phospholipids
a) polar head: forms outsides (bread) of bilayer
Described as hydrophilic: water loving, attracts water
b) non-polar tail: forms inside (PB&J) of bilayer
Described as hydrophobic: water fearing, avoids water
(polar)HEAD
Hydrophilic
(nonpolar) TAIL
Hydrophobic
2) Proteins with carbohydrate chains are wedged between
Phospholipid molecules.
a) Proteins act as pores, channels or pumps to move
substances into or out of cell.
b) Carbohydrates are markers which are used for cell
identification.
D. Selectively permeable:
allows CERTAIN substances to pass through
 The structure allows it to be selective.
Ex. Glucose can
pass through
Things soluble in Lipids
can pass (Ex. Alcohol)
Protein pores
allow small thing
insoluble in lipids
pass( Ex. H20)
– Molecules can pass through IF :
– They are soluble in lipids, they can easily pass
through bilayer (ex. Alcohol, CO2, O2, steroids)
– If they are NOT soluble in lipids (water, gulcose
amino acids, ions:
May be small enough to get through protein pores
(ex. water)
 May be able to go through a protein channel (ex.
Glucose)
 May be able to get pushed through by a protein
pump Ex. Na+(sodium ion), K+(potassium ion)


Examples of substances that need to pass
into cell:
– 1. water 2. glucose 3.oxygen

Examples of substances that need to pass
out of cell:
– 1. carbon dioxide
2. water
II. Cell Walls
A. Found in:
1) Plants 2) Algae 3) Bacteria 4) Fungi
(Have both cell membrane AND cell wall)
B. NOT IN ANIMAL CELLS
C. Function: EXTRA Support and protection, and gives extra
strength to cells
D. Composed of fibers of carbohydrates:
Plants
1. Cellulose in _____________
2. Chitin in _______________
Fungi
Eubacteria
3. Peptidoglycan in ___________________
REVIEW QUESTIONS

How does water move through the cell membrane?
_______________
Through
PROTEIN pores

What does semi-permeable mean?
Only allows certain substance through
___________________________________

Phospholipid
What molecule is the lipid bilayer made of? ___________

Head
tail
Which part is polar? _______Which
is nonpolar?_________



How does one cell recognize that a cell is part of that tissue
or organ? _____________
Carbohydrate chain
What is a substance that is soluble in lipids, that would pass
through the lipid bilayer of the cell membrane
Alcohol
easily?_______
False –animal cells don’t
True or False: All cells have cell walls? ______________

In Da Club - Membranes & Transport:
Crash Course Biology #5 - YouTube