7-3: Cell Boundaries
1
CELL WALL
• Strong supporting layer around the
membrane
• May be present in plants, protists, fungi,
and many prokaryotes
• Main function: to provide support and
protection for the cell
2
3
CELL WALL
4
CELL MEMBRANE
• Regulates what enters and leaves the cell;
provides protection and support
• Made up of two phospholipid layers called
a lipid bilayer
• Referred to as a “fluid mosaic model”
• http://www.dnatube.com/video/360/FluidMosaic-Model
5
Cell membrane TEM 436,740X
6
7
8
Cell Membrane Proteins
• Recognition Proteins: cell-to-cell
recognition
• Receptor Proteins: recognize and respond
to different extracellular molecules,
generating specific responses within cell
• Transport (Channel & Carrier) Proteins:
allow specific molecules and ions to pass
through the membrane
9
DIFFUSION THROUGH CELL
BOUNDARIES
• Process by which molecules move from areas of
higher concentration to areas of lower
concentration (examples: oxygen, carbon
dioxide, water)
• Continues until equilibrium is reached; particles
will still continue to move
• No energy is required by the cell
10
11
12
OSMOSIS
•
Diffusion of water through a selectively
permeable membrane
•
Some water molecules can pass through
cell membrane but most need channel
proteins
•
Selectively permeable membrane - some
substances can pass and some cannot
13
14
Effects of Osmosis on the cell
1.Isotonic: concentration is the same on
both sides of the cell. (Normal Cell)
2.Hypertonic: The solution, in which the cell
is in, has higher solute concentration than
the cell. (Skinny Cell)
3.Hypotonic: The solution, in which the cell
is in, has lower solute concentration than
the cell. (Swollen Cell)
15
16
Image source: mywellnesswarehouse.com
FACILITATED DIFFUSION
• Process that helps large molecules that can’t
pass through the membrane by osmosis
(example: glucose, amino acids)
• Protein molecules act as channels for large
molecules to pass from one side of the
membrane to the other side
• No energy is required by the cell
17
18
19
ACTIVE TRANSPORT
• Process which does require energy to
transport materials across the cell
membrane
• Movement of molecules against the
concentration differences
• Types of active transport consist of:
– Endocytosis
– Exocytosis
20
Endocytosis
• Occurs by infoldings, or pockets, of the
cell membrane
• Phagocytosis= “cell eating” cytoplasm
surrounds a particle and package it within
a food vacuole
• Pinocytosis= “cell drinking” tiny pockets
form along the cell membrane, fill with
liquid and then pinch off to form vacuoles
within the cell
21
22
23
24
Exocytosis
• removal of contents from the cell.
Ex: Contractile vacuoles
25
26