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

Double click the image to view movie

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.