Transcript Cell Structure and Function

Cell Structure and
Function
The Cell Theory
• All living things are made of one or
•
•
more cells
All cells come from pre-existing cells
Cells are the basic unit for structure
and function of all organisms
Cell structure
• All cells are surrounded by a plasma (cell)
•
•
membrane
Cells contain organelles - small structures inside
cells that perform various jobs
All cells can be divided into two main categories:
Prokaryotic vs. Eukaryotic
Cells
Prokaryotic
Eukaryotic
- no nucleus
- Very small (1-10
- have a nucleus
- Larger 10-100um
um)
- Have very few
organelles
(some larger)
- Have many
organelles
Eukaryotic Cells
• Plant and animal cells are eukaryotic as
well fungi and protists (amoeba,
paramecium, etc)
• Plant and animal cells have important
differences (see diagrams)
Eukaryotic Cellular
Organization
• Single celled organisms (unicellular)
• Multiple celled organisms (multicellular)
- in multicellular organisms, cells
become specialized (do a particular
job)
Plasma (cell) membrane
• Consists of a double layer of lipids
• The outside and inside of the membrane is
hydrophilic (“water-loving”)
• The interior of the membrane is
hydrophobic (“water-fearing”)
• Substances must cross the membrane to
enter and exit the cell
Types of Membrane Transport
Passive Transport (requires NO energy)
• Moves substances from a high to a low concentration
• Diffusion & osmosis, facilitated diffusion
Active Transport (requires energy)
• Substances move from a low to a high concentration
• Endocytosis & exocytosis
Concentration gradient
• Passive transport
•
moves substances
WITH (or DOWN)
their concentration
gradient
Active Transport
moves substances
AGAINST their
concentration
gradients
PASSIVE TRANSPORT
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HIGH
LOW
ACTIVE TRANSPORT
Diffusion
• Movement of a
substance from a high
concentration to a low
concentration
QuickTime™ and a
TIFF (Uncomp resse d) de com press or
are nee ded to s ee this picture.
Osmosis
• Movement of water
from a high water
concentration to a low
water concentration
QuickTime™ and a
TIFF (Uncomp resse d) de com press or
are nee ded to s ee this picture.
Osmosis in Different Cellular
Environments
• Hypotonic - solution with
•
•
a lower solute
concentration than the
cytoplasm of the cell
Hypertonic - solution with
a higher solute
concentration than the
cytoplasm of the cell
Isotonic - has same solute
concentration as the
cytoplasm of the cell
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
• Turgor pressure - pressure (from water)
pushing against the cell wall of a plant
(makes plant cells firm)
• Plasmolysis - shrinking of the cytoplasm of
a cell caused by the loss of water (causes
plants to wilt)
Facilitated Diffusion
• Diffusion using
•
membrane protein
channels
Some substance must
use protein channels
since they cannot
pass through the lipid
layer of the
membrane
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Active Transport
• Requires the input of
•
energy to move a
substance against its
concentration gradient
(low to high)
Energy is used in the
form of ATP (energy
molecule produced in
mitochondria)
QuickTi me™ a nd a
TIFF (Uncompre ssed ) decomp resso r
are need ed to se e th is p icture.
Types of Active Transport: Endocytosis,
Exocytosis and Ion Pumps
• Endocytosis - cell takes in
•
•
substances too large to
pass through the
membrane
Exocytosis - cell gets rid
of large substances
Ion pumps - pump ions
against their
concentration gradient
See endocytosis and exocytosis in action