A B C D F E

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 significant Figure 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 Molecules 1.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 Molecules 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. – O 2 and CO 2 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.Temperature 2.Molecular Size 3.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 R 2 = how well points fit line Significance (P value) = is slope of line different from a slope of 0?

Regression Analysis

Regressions and Written Results Remember: the P value goes in parentheses at the end of the sentence that states the result R 2 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