Mitochondria
• Found in all eukaryotic cells.
• Responsible for energy production.
Chloroplasts
• Found only in eukaryotic cells such as plants
and algae.
• Site of photosynthesis.
Cytoskeleton
Cytoskeleton
• Made of long, thin,
protein filaments.
– Three sizes
• Microfilaments
• Intermediate filaments
• Microtubules
• Provides internal cell
structure.
• Anchor and connect
organelles.
• Move parts and products.
What is the
nature of cell
membranes?
Plasma Membrane
• Fluid mosaics of phospholipids, proteins and
carbohydrates.
Plasma Membrane
• Phospholipids provide basic architecture.
– Have hydrophilic tails and hydrophobic heads.
Plasma Membrane
• Proteins act as
channels,
recognition
molecules,
carrier proteins,
etc.
• Carbohydrates
help connect
cells and play a
role in
identification.
Diffusion
• Net
movement of
molecules
from areas of
high
concentration
to areas of
low
concentration.
• No energy
required.
Diffusion
Double click the image to play movie
Osmosis
• Type of diffusion.
• Movement of water across semipermeable membrane from
area of high water concentration to area of low water
concentration.
Effect of osmosis on cells in various
solutions
• Hypotonic solutions
– High concentration of
water in extracellular
fluid compared to
inside the cells
causes net movement
of water into the cell.
– Results in increased
cell size.
– Can cause cell to
burst.
Effect of osmosis on cells in various
solutions
• Isotonic solutions
– Concentrations of
water inside and
outside of the cell
are equal.
– Results in no net
movement of water.
– Cell size remains
the same.
Effect of osmosis on cells in various
solutions
• Hypertonic
solutions
– Concentration of
water in cell
exceeds that
outside of cell.
– Results in net
movement of water
out of the cell.
– Cell shrinks.
Membrane transport
• Large or hydrophilic
substance cannot pass
freely through the
membrane.
• To move them through
the membrane, must
have channel proteins or
carrier proteins.
Passive Transport: Ion Channels
• Ions are hydrophilic and the channel must be
open for the ion to pass through the channel.
• Selective for each ion.
• Ion moves down concentration gradient.
Passive Transport: Facilitated
diffusion
• Molecule enters protein carrier.
• Induces protein shape change allowing molecule to
exit the carrier.
Passive Transport: Facilitated
diffusion
• Selective for each molecule.
• Molecule moves down concentration gradient.
Passive Transport: Facilitated
diffusion
Double click the image to view movie
Active Transport
• Uses carrier protein.
• Moves molecules against their concentration
gradient.
• Requires ATP as an energy source.
Active Transport
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Active Transport
Endocytosis
• Cells absorb outside material by inverting plasma
membrane to form a vesicle that encases the
material.
Exocytosis
• Moving molecules, particles, and other substances
contained in vesicles across the plasma
membrane and out of the cell.