A

B

CD

FE

Review

• What is a good hypothesis and how does it differ from a prediction?

• Appropriate Figures and Figure Legends

• Discrete vs. Continuous variables

• Mean vs. Median

• P-value• Statistically significantFigure 1. The absorption (in optical density) of

ethanol (treatment) and water (control) after each solution was soaked in onion for 15 minutes. Data are means +/- 1 standard error.

Scientific Citations

• Paraphrasing a paper: Paraphase (Joseph et al. 1991).

Lab Presentations• Lab Presentations will begin in 4 Weeks.

• Start thinking about Your Lab Presentation:– Presentation Groups must be composed of 2 or 3 People,

No More!– Page 75 lab

• The Best 10 Presentation Abstracts in the Entire General Biology I Lab, will receive 10 Bonus Points!– Read Appendix E on Abstracts.– I will pick the Top 2 Abstracts from my 2 labs. – 10 Points is A LOT!!

Lab Exercise 4

Introduction To Cell Biology II:

Membrane Transport

The Movement of Molecules1. Diffusion

The passive movement of like molecules (or ions) down a concentration gradient.

2. Osmosis The movement of water molecules across a selectively

permeable membrane, a pressure gradient, or both.

3. Active Transport The transport of molecules across a selectively

permeable membrane that goes against the concentration gradient, and thus requires an input of energy (often ATP).

The Movement of MoleculesOverview of the two possibilities

Passive transport

Diffusion Facilitated diffusion

Active transport

ATP

Fig. 7.17

“Downhill”“Uphill”

Aquaporin

Diffusion• The tendency of molecules to move from an area of

higher concentration to an area of lower concentration.• Diffusion is a mechanism of passive transport.

– No Energy is required for diffusion to occur.– O2 and CO2 are both molecules that move across cell

membranes via diffusion.

Diffusion• If there is no concentration gradient, the substance is in

dynamic equilibrium, and no net movement occurs.

• The Rate of Diffusion depends on:1. Temperature2. Molecular Size3. Concentration Gradient

Solutions• Solutions are composed of 2 parts:

1. Solvent the dissolving agent.

2. Solute the substance that is

being dissolved.

Example: Salt Being Dissolved In Water:

Water is the Solvent.Salt is the Solute.

Salt Water is the Solution!

Osmosis• The diffusion of water across a selectively permeable

membrane is a special case of passive transport called osmosis.

– Water moves from a solution with lower solute concentrations to a solution with higher solute concentrations.

• The direction of water movement (osmosis) is determined by the difference in the TOTAL solute concentrations in the solutions.

Osmotic Concentration• The concentration of all solutes in a solution.• When a selectively permeable membrane separates 2

solutions, each solution can be identified as either:– Hypotonic or Hypoosmotic

• The solution with the lower solute concentration.

– Hypertonic or Hyperosmotic • The solution with the higher solute concentration.

– Isotonic or Isoosmotic• The solute concentrations in both solutions are the same.

Water channel proteins: Aquaporins

• Membrane-spanning protein• allows for osmosis

Osmotic Concentrations

Turgor Pressure

• Positive pressure exerted against a cell wall due to differences in osmotic pressure, maintains cell rigidity

Regression Analysis

• Examines influence of indep. variable on depen. variable

• Gives equation of line that best fits data points

• R2 = how well points fit line

• Significance (P value) = is slope of line different from a slope of 0?

Regression Analysis1 2

34

Regressions and Written Results• Remember: the P value goes in parentheses at the end

of the sentence that states the result

• R2

• How well data points fit regression line• The % of variability in “Y” (depend. var.) that is

explained by “X” (independ. var.)• P value

• A significant difference between the slope of your regression line and a slope of 0

• Indicates whether “X” has a significant effect or impact on “Y”

T-test vs. Regression• When should you use a T-test and when

should you use a regression analysis?

• T-test Review• Paired vs. unpaired

Next Week

• Quiz • Lab Report 3 Due• Lab 5

– Intro to Cell Physiology I: Plant Pigments