Quick Review! Nucleus Nuclear membrane Nuclear Pore Nucleolus Chromatin Ribosome ER- rough & smooth Golgi Complex Centriole Microtubules Cell membrane Cytoplasm Vesicle Lysosome Mitochondria What are the parts of an animal cell?

Plasma Membrane Two key components of the membrane: *phospholipids *proteins

The plasma membrane is semi-permeable (selectively permeable) It controls what goes into and out of the cell Why would the membrane need to be semi-permeable??

Homeostasis “Resistance to Change” The maintenance of internal environments while external conditions vary. Why is it important for the cell membrane to maintain homeostasis? –Cells work best when they are surrounded by constant conditions. Extreme “environments” are not well tolerated.

Two forms of transport: Passive Transport No energy needed WITH the gradient (high to low) Examples: –Diffusion –Osmosis Active Transport ENERGY used AGAINST the gradient Examples: –Endocytosis –Exocytosis

Phospholipids The phospholipids line up to form a double membrane Small, uncharged particles are able to pass right between the phospholipids This is called simple diffusion

Proteins There are also proteins embedded between the phospholipids. These proteins function as gates, allowing larger or charged molecules to get in/out of the cell Only molecules which are “recognized” are allowed thru these proteins This is facilitated diffusion

What makes diffusion occur? Simple Diffusion occurs when molecules in a high concentration area move to an area of low concentration. In Facilitated Diffusion molecules move across a membrane with the help of transport proteins. –Examples: Glucose and Amino Acids

Passive transport: Diffusion Lower Concentration Higher Concentration Molecules collide – pass thru membrane Common Examples: oxygen molecules & water molecules

Passive Transport: Osmosis The movement of water Water moves TOWARDS the molecules Think of it as “water wants to dissolve stuff” Which way will water move in each case?

Passive Transport: Osmosis ISOtonic HYPERtonic HYPOtonic Iso = normal Hyper = moreHypo = less

The effect of osmosis on cells HYPERTONIC ISOTONIC HYPOTONIC

Passive transport: osmosis Osmosis Which way will water move?

Hypertonic or Hypotonic?

Lesson 2 Begins

Crossing the Plasma Membrane Figure 3.8 Active transport AGAINST the gradient requires energy!

Active Transport Endocytosis –Pino- –Phago- Exocytosis Figure 3.9 IN OUT

Crossing the Plasma Membrane Passive Transport Active Transport

Crossing the Plasma Membrane Passive Transport No energy needed WITH the gradient Diffusion Osmosis Active Transport ENERGY used AGAINST the gradient Endocytosis Exocytosis

Post test What is the job of the plasma membrane? What is semi-permeable? What is the difference between active transport and passive transport? What is osmosis? What will happen to a cell when placed in a hypertonic solution? Hypotonic solution?

Name the organelle and the function! Name the organelle and the function!