Cell Membranes and Transport1-2- Water and Polarity1-3 – Acids, Bases and Buffers 1-4 – Biological Molecules: Lipids1-5 – Cell Membranes1-6 – Surface Area-Volume Ratio

The unique properties of water make life as we know it possible.

Transport across membranes is just one process in our bodies that is greatly affected by WATER.

Water and It’s role in biological Systems

describe how the polarity of the water molecule results in hydrogen bonding

Polar bonding Unequal sharing of electrons (+) and (-) charges on the molecule

Polarity creates Hydrogen bonds H bonds are relatively

weak

Animation of Covalent and Polar bonds (scroll down on the page when it opens)

There’s strength in numbers!

Unique Properties of Waterdescribe the role of water as a solvent, temperature regulator, and lubricant

1. “Universal Solvent”

Dissolves all polar and ionic molecules.

HydrophobicVs Hydrophilic?

Hydrophobic Interactions:Oil cannot interact with the polar

regions of H2O and actually interfere with the H bonds between H2O molecules.

interfering (breaking) with the H bonds requires ENERGY

When given the chance, oil droplets will cluster, reducing the surface area exposed to the H2O. (therefore using less ENERGY to break the H bonds)

*** the H Bonds “force” the oil droplets to stay together.

2. Temperature Regulation by Water--another process our bodies use water for!

1. High specific heat (the amount of Energy needed to raise 1gm of water 1oC)

2. High heat of vaporization 3. High heat of fusion

“Water is Life” – Mr. Anderson

with Bozeman science.

Acids, Bases and pHdifferentiate among acids, bases, and buffers

pH measures the [ ] of the H+ compared with OH-

PURE H2O : Neutral, therefore pH 7

[H+] = [OH-]

** the pH scale is a log scale; a change in pH from 7 to 6 means there are 10x more H+ ions than in the neutral solution.

Acids

Dissociate to donate H+ ionspH < 7[H+] > [OH-]

Bases

molecules that release OH- ions

therefore pH > 7

(ex. NaOH)

[H+] < [OH-]

Controlling pH in the BodyBUFFERS are molecules that can either pick up or release

hydrogen (or hydroxide) ions Eg. pH is too low: HCO3

- + H+ --> H2CO3

(bicarbonate) (carbonic acid)

pH is too high: H2CO3 + OH- HCO3- + H2O

(excess of OH-)

Cell Membranes “gate keepers”

1. Isolate from outside

2. Control entry and exit

3. Communicate with others

4. Bare identification (I’m one of you!)

you tube cell membranes (lots of other links for passive/active transport, etc

Cell Walls NB** Cell walls are

different from cell membranes

Stiff, non-living Made of complex

carbohydrates Cellulose for plants Chitin for fungi Chitin-like frame for

bacteria Used for support and

protection Very porous; entry only

controlled by size

Which of these statements are true comparing cell walls with membranes?

Walls Membranes

A Non-living Living

B Plants and bacteria only

Animals only

C Control entrance by size only

Control entrance by many factors

D Made with cellulose Made with lipids

E Contain pores Contain pores

Fluid Mosaic Model A phospholipid

bilayer with proteins scattered through it

“fluid” because the proteins seem to “float” around the bilayer

Hydrophilic heads on the outside

Hydrophobic tails on the inside

PHOSPHOLIPIDS – one type of Lipid

Watch Mr. Anderson – Bozeman Science on LIPIDS

Lipids

Glycerol + Fatty Acids

Saturated fatty acids

Unsaturated

Fatty acids

Hydrophobic layer is a barrier to H2O soluble molecules (but makes it less fluid)

Cholesterol in the bilayer is even less permeable to H2O soluble molecules (but makes it less fluid)

“Protein Mosaic” Membrane proteins will interact with the

hydrophobic and hydrophilic layers of the bilayer Some proteins will protrude into the cytoplasm,

some into the extracellular space, others into both

Glycoproteins Membrane

proteins that have a carbohydrate chain attached

Often seen in proteins that protrude outside the cell

Glycolipids Membrane lipids

that have a carbohydrate chain attached

Both glycoproteins and glycolipids OFTEN function in cell-to-cell communication and/or recognition

What does the “fluid” in “fluid mosaic model” refer to? A. The structure of the cell membrane B. The structure of the cell wall C. The fact that the membrane is made up

mostly of water D. The fact that the membrane is always

changing, so it seems to be “fluid” E. The fact that the membrane is made up

of lipids, and they tend to “flow”

What does “mosaic” mean? A. a picture B. a lipid C. a bunch of different things clumped

together on a background D. a type of protein that lets things into

the cell E. No idea!

Which of the following is not true regarding this diagram?

A. 1a and 1b are fatty acids

B. 3 is a phosphate group

C. 5 is the hydrophobic end of the molecule

D. 6 is the hydrophobic end of the molecule

E. this is a type of lipid

Which one is a: 1. Phospholipid 2. Glycolipid 3. Cholesterol

3 major membrane Protein Categories: 1. Transport proteins Regulated, fast method for specific molecules to

enter and exit Channel proteins Carrier proteins

2. Receptor Proteins When activated, set off enzymatic

sequences inside the cell

3. Recognition Proteins “identification tags”

Membrane Transport - RATE Depends on:

Gradient (concentration, electrical or pressure)

Size of molecule Lipid solubility # of transporters

Diffusion The random net movement of molecules from an

area of high concentration to an area of low concentration.

(this is following the “concentration gradient”)

Osmosis The diffusion of WATER across a selectively

permeable membrane (this is also following the “concentration gradient”

and does not require energy)

Osmotic Effects Isotonic solution

Same solute concentration

Cell is happy (no net loss or gain of water)

HYPERtonic solutions

[Solute] is greater outside the cell than inside the cell

Cell is not happy It will crenate (shrink)

HYPOtonic solutions Solute concentation

is less outside the cell than inside

Cell is not happy Cell will lyse

Why are cells so small? (why don’t we grow them larger?)animation that shows

comparison of SA and Volume

calulating SA/V ratios WS

(that crazy guy with the pink shirt/yellow tie explains SA/Vol ratio)

Active transport Often against the

concentration gradient Therefore,

REQUIRES ENERGY

(ATP --> ADP + P) Uses transporter

proteins

Endocytosis - 3 types

PhagocytosisLarge particles

2. Pinocytosis Liquid and smaller particles

only

Receptor-mediated Endocytosis Uses receptors to

bind first to the desired molecules, then gathers them together before enclosing them in a membrane