Unit 2.2 Check and Reflect Target Knowledge : 1.I can predict the movement of molecules across a gradient. 2.I know the difference between active and passive transport. 3.I can describe the cell membrane as a fluid mosaic model. 4.I can explain semi-permeability. 5.Explain the role of macromolecules (lipids and protein) in cell transport. Target Vocabulary 1.cell membrane 2.lipid bilayer 3.diffusion 4.equilibrium 5.osmosis 6.facilitated diffusion 7.active transport 8.concentration 9.isotonic 10.hypotonic

Cell Membranes Osmosis and Diffusion

Functions of Membranes 1.Protect cell 2.Maintain homeostasis 3. Selectively permeable - allows some molecules in, others are kept out

Homeostasis internal condition of cellsBalanced internal condition of cells Also calledAlso called equilibrium controlling what enters & leaves the cellMaintained by cell membrane controlling what enters & leaves the cell

hydrophilic Polar heads are hydrophilic “water loving ” hydrophobic Nonpolar tails are hydrophobic “water fearing” Phospholipid Bilayer Makes membrane “Selective” in what crosses

Fluid Mosaic Model: “Proteins floating in a sea of lipids”

Proteins Are Critical to Membrane Function

Blood-Brain Barrier Allows some substances into the brain, but screens out toxins and bacteria Substances allowed to cross include: water, CO 2, Glucose, O 2, Amino Acids, Alcohol, and antihistamines. HIV and bacterial meningitis can cross the barrier.

Solutions Solutions are made of solute and a solvent Solvent – The liquid part. It does the dissolving. Solute – The thing being dissolved. Salt and sugar are solutes.

Methods of Transport Across Membranes 1. Diffusion 2. Osmosis 3. Facilitated Diffusion 4. Active Transport

Methods of Transport Across Membranes 1. Diffusion -passive transport - no energy used 2. Osmosis - Passive transport of water across membrane 3. Facilitated Diffusion – Needs a helper to get things across 4. Active Transport- requires energy to transport molecules against a concentration gradient – energy is in the form of ATP

Diffusion Movement of molecules from an area of high concentration to an area of low concentration. Movement from one side of a membrane to another, without help.

Diffusion

Diffusion of Liquids

Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW)

Facilitated Diffusion Does NOT require energy Uses transport proteins to move things from high to low concentration Examples: Glucose or amino acids moving from blood into a cell.

Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins.

Facilitated Diffusion This is a helper.

Active Transport Requires energy (ATP) Moves materials from LOW to HIGH concentration AGAINST the concentration gradient.

Osmosis Diffusion of water across a membrane. Moves from HIGH water amount (low solute) to LOW water amount (high solute). Diffusion across a membrane Semipermeable membrane

You could think of it this way… In osmosis, water FOLLOWS salt!! This is sometimes an easier way to remember this concept.

Salt Where is the water moving? The water is moving out of the cell. Why? Remember wherever salt is water follows! SALT

Light blue = Salt Dark blue = water

There is a lot of salt outside of the cell. What will happen? Why?

What will happen if there is a lot of salt inside of the cell?

Red Onion Cells Normal In Salt Water What happened to the cytoplasm and cell membrane?

Diffusion of H 2 O Across A Membrane High H 2 O potential (amount) and Low solute concentration Low H 2 O potential (amount) and High solute concentration

Osmosis: Draw this

Three Forms of Transport Across the Membrane

Question Why does eating popcorn make you thirsty? Popcorn is very salty and may cause water to leave the cells of your mouth and through due to diffusion. This makes a person thirsty.

When a sea urchin egg is removed from the ocean and placed in freshwater, the egg swells and bursts. Which of these causes water to enter the egg? A.Coagulation B.Sodium Pump C.Active Transport D.Osmosis D

The picture shows a cell model and the solutions associated with it. In this situation the cell model will — A.Gain mass B.Shrink C.Increase in solute content D.Start to vibrate B

Which of these best explains why a freshwater aquarium would be a dangerous habitat for saltwater fish? A The tissues of the saltwater fish would absorb too much acid. B The cells of the saltwater fish would lose too much water. C The organ systems of the saltwater fish would consume too much energy. D The cells of the saltwater fish would gain too much water. D

On a hot summer day, a road-crew worker perspires and then feels thirsty as her body temperature increases. This response is an example of – A.Releasing enzymes B.Maintaining homeostasis C.Decreasing respiration D.Assimilating proteins B

Think/Pair/Share Work with a partner to create different situations that can be classified as diffusion. Do the same for osmosis.

Another Video: Active Transport Video: sandTheCell/ActiveTransport.mov sandTheCell/ActiveTransport.mov Diffusion Video: nsandTheCell/Diffusion.mov nsandTheCell/Diffusion.mov