Warm-Up Warm-Up organellesorganelles

11/8/1111/8/11

Why would plants need to have both Why would plants need to have both chloroplasts and mitochondria? (Look at chloroplasts and mitochondria? (Look at function for each)function for each)

Have out animal and plant drawings to be Have out animal and plant drawings to be stampedstamped

Cell Membranes vs. Cell WallsCell Membranes vs. Cell Walls Cell Membranes Cell Membranes

regulate what regulate what

comes into and comes into and

out of cellsout of cells Cell Walls Cell Walls

provide provide

protection and protection and

support for support for

the cellthe cell

Phospholipids make up Phospholipids make up cell membranescell membranes

Polar “head” that is attracted to water

Non-polar “tails” that are not attracted to water but are attracted to other phospholipid tails

Phospholipids make up cell Phospholipids make up cell membranesmembranes

Water molecules

Water

Polar head faces out towards water because of the attraction

Nonpolar tails face inward so they are protected from water

Electron micrograph of Electron micrograph of cell membranecell membrane

Inside cell layer

Outside cell layer

Membranes are picky!!!Membranes are picky!!!

Membranes are Membranes are semi-permeablesemi-permeable because because they only let certain molecules throughthey only let certain molecules through

Small and non-polar molecules can pass Small and non-polar molecules can pass through easily (water, oxygen, carbon through easily (water, oxygen, carbon dioxide)dioxide)

Large and polar molecules cannot pass Large and polar molecules cannot pass through without help (starch, glucose, through without help (starch, glucose, proteins, amino acids, ions)proteins, amino acids, ions)

Diffusion and OsmosisDiffusion and Osmosis

Diffusion-Diffusion- The movement of particles from The movement of particles from a region of higher concentration to a a region of higher concentration to a region of lower concentration, caused by region of lower concentration, caused by the random motion of particles.the random motion of particles.

Osmosis-Osmosis- The diffusion of The diffusion of waterwater across a across a semi-permeable membrane towards the semi-permeable membrane towards the side with higher solute concentration.side with higher solute concentration.

Why does osmosis happen?Why does osmosis happen?Two factors cause osmosis:Two factors cause osmosis:1.1. A semipermeable membrane allows water A semipermeable membrane allows water

molecules to move back and forth through molecules to move back and forth through the membrane, but not solute moleculesthe membrane, but not solute molecules

2.2. Water molecules “stick” temporarily to any Water molecules “stick” temporarily to any dissolved solute molecules. dissolved solute molecules.

As a result, water molecules spend more time As a result, water molecules spend more time and accumulate on the side of the membrane and accumulate on the side of the membrane with the higher concentration of dissolved with the higher concentration of dissolved solutes. solutes.

SolutionsSolutions

SoluteSolute- the substance dissolved in a - the substance dissolved in a solutionsolution

SolventSolvent- the substance in which a solute - the substance in which a solute is dissolvedis dissolved

ExampleExample In a solution of salt dissolved in water:In a solution of salt dissolved in water:

Salt is the solute; water is the solventSalt is the solute; water is the solvent

Types of SolutionsTypes of Solutions

hypertonic solutionhypertonic solution- a solution with a - a solution with a higherhigher solute concentration than what it is compared solute concentration than what it is compared with.with.

hypotonic solutionhypotonic solution- a solution with a - a solution with a lowerlower solute concentration than what it is compared solute concentration than what it is compared with.with.

isotonic solutionisotonic solution a solution with an equal a solution with an equal solute concentration to what it is compared solute concentration to what it is compared with. with.

Visual ExamplesVisual Examples

Solution is hypotonic to cell.Cell is hypertonic to solution.

Solution is hypertonic to cell.Cell is hypotonic to solution.

Solution is isotonic to cell.Cell is isotonic to solution.

Facilitated diffusionFacilitated diffusion

The movement of molecules across a cell The movement of molecules across a cell membrane from an area of higher membrane from an area of higher concentration to an area of lower concentration to an area of lower concentration with the help of a carrier concentration with the help of a carrier protein. This transport does NOT require protein. This transport does NOT require energy to happen. Moving large energy to happen. Moving large molecules.molecules.

Passive transportPassive transportPassive transportPassive transport happens spontaneously across happens spontaneously across

the cell membrane. It does NOT require any the cell membrane. It does NOT require any cellular energy (ATP) because molecules cellular energy (ATP) because molecules move DOWN their concentration gradients move DOWN their concentration gradients (from high to low concentration).(from high to low concentration).

There are two types of passive diffusion:There are two types of passive diffusion:

1.1. Simple diffusionSimple diffusion:: molecules pass directly molecules pass directly through the lipid bilayer.through the lipid bilayer.

2.2. Facilitated diffusionFacilitated diffusion:: molecules are too big to molecules are too big to pass through the lipid bilayer. They bind to a pass through the lipid bilayer. They bind to a carrier proteincarrier protein to diffuse across the to diffuse across the membrane. membrane.

Passive transportPassive transportSimple diffusionSimple diffusion Facilitated diffusionFacilitated diffusion

Carrier protein

Co

ncen

tration

Grad

ient

3 steps in facilitated 3 steps in facilitated diffusiondiffusion

1. Particle binds to one side of carrier protein

2. Carrier protein changes shape

3. Particle diffuses to other side of membrane

Active transportActive transport

The movement of molecules across a cell The movement of molecules across a cell membrane from an area of low membrane from an area of low concentration to an area of higher concentration to an area of higher concentration (“up” or “against” the concentration (“up” or “against” the concentration gradient). Active transport concentration gradient). Active transport requires the use of energy (ATP).requires the use of energy (ATP).

Starch/Iodine Lab- Lab set up due Starch/Iodine Lab- Lab set up due WednesdayWednesdayStarch/Iodine Lab- Lab set up due Starch/Iodine Lab- Lab set up due WednesdayWednesday

• How does the size of molecules affect their How does the size of molecules affect their diffusion across a semi-permeable membrane?diffusion across a semi-permeable membrane?

• Create two experimental procedures to Create two experimental procedures to demonstrate question (pictures or words)demonstrate question (pictures or words)– Must keep solutions separateMust keep solutions separate– Iodine solution (water with 10 Iodine solution (water with 10 dropsdrops of iodine) of iodine)– Hypothesis is your prediction on what will happenHypothesis is your prediction on what will happen

• Which molecule will moveWhich molecule will move• Where will the color change take placeWhere will the color change take place

Homework:Homework:

Section 7.3 assessment questions, due Section 7.3 assessment questions, due Wednesday Wednesday