EGG OSMOSIS LAB

10-10-1985

Warm-up

◦List 1 positive thing that happened to you this week

◦List 1 positive thing you look forward to this weekend! (woohoo!)

Homework Reminders◦MasteringBiology: due Monday, October 13 at 10:45 am

◦Chapter 5 tutorial◦Chapter 6 tutorial◦Chapter 6 questionsChapter 6 material may take up to 50 minutes….so do this ahead of time!

◦Lab Write-up: due Monday, October 13 in beginning of class

The chapter 7 worksheet is yours to work on...bring it 100% completed on Monday, and 5 extra points will be banked towards the Unit 3 Exam

Unit 3 Exam

Projected to be Thursday, October 16

Topics covered yesterday

◦Cell membrane◦Diffusion◦Osmosis

Today’s objectives

◦SWBAT qualitatively investigate osmosis in cells and explain that external environments can be hypotonic, hypertonic, or isotonic to internal environments of cells.

◦Science Practice #6: SWBAT perform data analysis and evaluation of evidence

Getting through cell membrane◦Passive transport◦Facilitated transport◦Active transport

AP Biology 2005-2006

Cell (plasma) membrane Cells need an inside & an outside…

separate cell from its environment cell membrane is the boundary

INfoodcarbohydratessugars, proteinsamino acidslipidssalts, O2, H2O

OUTwasteammoniasaltsCO2

H2O products

cell needs materials in & products or waste out

IN

OUT

Can it be an impenetrable boundary? NO!

AP Biology

Building a membrane How do you build a barrier that keeps

the watery contents of the cell separate from the watery environment?

Your choices

carbohydrates?

proteins?

nucleic acids?

lipids?

LIPIDS oil & water

don’t mix!!

AP Biology

Lipids of cell membrane Membrane is made of phospholipids

phospholipid bilayer

phosphate

lipid

hydrophilic

hydrophobic

inside cell

outside cell

AP Biology

Phospholipids It’s like this demented Rudolph looking thing has a split personality

It’s amphipathic!

AP Biology

Semi-permeable membrane Need to allow passage through the

membrane But need to control what gets in or out

membrane needs to be semi-permeable

So how do you build a semi-permeable membrane?

aa H2Osugar lipid salt NH3

AP Biology

Phospholipid bilayer What molecules can get through directly?

inside cell

outside cell

fats & other lipidscan slip directly through the phospholipid cell membrane, but…

what about other stuff?

lipid

salt

aa H2Osugar

NH3

AP Biology

Simple diffusion across membrane

inside cell

outside cell

Which way will lipid move?

low

high

lipid

lipid

lipid

lipid

lipid

lipid lipid

lipidlipid

lipid

lipid

lipid

lipid

lipid

AP Biology

Permeable cell membrane Need to allow more material through

membrane needs to be permeable to… all materials a cell needs to bring in all waste a cell needs excrete out all products a cell needs to export out

inside cell

outside cell

lipidsugaraaH2O

salt

“holes”, or channels, in cell membrane allow material in & out

NH3

AP Biology

Diffusion through a channel Movement from high to low

inside cell

outside cell

sugar

sugar

sugar

sugar

sugarsugar

sugar sugar

sugarsugarsugar

Which way will sugar move?

low

high

sugar

AP Biology

Semi-permeable cell membrane But the cell still needs control

membrane needs to be semi-permeable specific channels allow

specific material in & out

inside cell

outside cell

sugaraaH2O

saltNH3

AP Biology

How do you build a semi-permeable cell membrane? What molecule will sit “comfortably” in a

phospholipid bilayer forming channelsbi-lipid

membraneprotein channels

in bi-lipid membrane

what properties

does it need?

AP Biology 2005-2006

Why proteins? Proteins are mixed molecules

hydrophobic amino acids stick in the lipid membrane anchors the protein in membrane

hydrophilic amino acids stick out in the watery

fluid in & around cell specialized “receptor”

for specific molecules

AP Biology

Facilitated Diffusion Globular proteins act as doors in membrane

channels to move specific molecules through cell membrane

“The Bouncer”

open channel = fast transport

high

low

AP Biology

Active Transport

“The Doorman”

conformational changelow

high

Globular proteins act as ferry for specific molecules shape change transports solute from one side of

membrane to other protein “pump” “costs” energy

AP Biology

Getting through cell membrane Passive transport

diffusion of hydrophobic (lipids) molecules high low concentration gradient

Facilitated transport diffusion of hydrophilic molecules through a protein channel

high low concentration gradient

Active transport diffusion against concentration gradient

low high uses a protein pump requires ATP

AP Biology 2005-2006

Facilitated diffusion Move from HIGH to LOW concentration

through a protein channel passive transport no energy needed facilitated = with help

AP Biology 2005-2006

Active transport Cells may need molecules to move

against concentration situation need to pump against concentration protein pump requires energy

ATP

Na+/K+ pump in nerve cell membranes

AP Biology

Active transport

using ATPusing ATP

Many models & mechanisms

AP Biology 2005-2006

Osmosis is diffusion of water Water is very important, so we talk about water

separately Diffusion of water from

high concentration of water to low concentration of water across a

semi-permeable membrane

AP Biology

Concentration of water Direction of osmosis is determined by

comparing total solute concentrations Hypertonic - more solute, less water Hypotonic - less solute, more water Isotonic - equal solute, equal water

hypotonic hypertonic

water

net movement of water

AP Biology

Managing water balance Cell survival depends on balancing

water uptake & loss

freshwater balanced saltwater

AP Biology

Managing water balance Isotonic

animal cell immersed in isotonic solution blood cells in blood no net movement of water

across plasma membrane water flows across

membrane, at same rate in both directions

volume of cell is stable

Egg Osmosis Lab

An unfertilized egg is a very big cell

Purpose of lab

Given two different solutions and an egg as a cell, you will determine whether the solutions are hypotonic or hypertonic

MethodsCorn syrup Distilled water

2 replicates 2 replicates

Why is having replicates important in scientific research?

What are our hypotheses & predictions?

MethodsCorn syrup Distilled water

2 replicates 2 replicates

Hypothesis and predictions

◦Hypothesis: The tonicity of a solution will affect the mass of the egg.

◦Null Hypothesis: The tonicity of a solution will not affect the mass of the egg

◦Predictions: If a solution is hypertonic, then the eggs will ____________mass over time

If a solution is hypotonic, then the eggs will ________________ mass over time If a solution is isotonic, then the eggs will ______________________ mass over time.

Procedures1. Each group will go back one at a time to record the

final egg mass. When your group is done, please throw away the egg and thoroughly rinse the beakers and place them in the spots as directed by Dr. Cao.

2. Please work efficiently so that we can get all the data collected in a timely manner.

3. Everyone in a group has a role

4. While your group waits to record data, work on your Chapter 7 (cell membrane) worksheet. It will be checked for completion on Monday, and an extra 5 points will be banked to the Unit 3 exam…so it is both a study guide and extra credit.

5. We will pool our data as a class and analyze them together.

6. Lab write ups are due Monday, October 13 in the beginning of class.

Group roles:Person 1: Water 1 EggPerson 2: Water 2 EggPerson 3: Syrup 1 EggPerson 4: Syrup 2 EggPerson 5: Cleans beakersEveryone: records data on data sheet

Class data

https://docs.google.com/a/cms.k12.nc.us/spreadsheets/d/1OzawI2hsiCfxxlIfpl09-u329R9iZp1jhVsT_pA94sQ/edit#gid=0

Data analysis

-In science, it is important to quantify the trends that we see in our data

-Statistics allows us to test our hypotheses and determine whether our data show a significant relationship in the variables in which we are studying

-P-values tell us whether a result is significant or not.

-A small p-value (typically ≤ 0.05) indicates strong evidence against the null hypothesis, so you reject the null hypothesis and accept the other hypothesis.

Hypothesis and predictions◦Hypothesis: The tonicity of a solution will affect the mass of the egg.

◦Null Hypothesis: The tonicity of a solution will not affect the mass of the egg

◦Predictions: If a solution is hypertonic, then the eggs will ____________mass over time

If a solution is hypotonic, then the eggs will ________________ mass over time If a solution is isotonic, then the eggs will ______________________ mass over time.

If P > 0.05, then we can reject the null hypothesis.

Simple Linear Regression◦ Quantifies the linear

relationship between the independent and dependent variables

ANOVA

  df SS MS FSignifica

nce F

Regression 1 5356.965659 5356.965659 87.958259342.77E-

10

Residual 29 1766.201438 60.90349785

Total 30 7123.167097      

  Coefficients Standard Error t Stat P-valueLower 95%

Upper 95%

Lower 95.0%

Upper 95.0%

Intercept 72.12116476 1.776126889 40.6058628 4.13467E-2768.4885

875.7537

568.4885

875.7537

5

0 -0.010743771 0.001145562 -9.378606471 2.77133E-10 -0.01309 -0.0084 -0.01309 -0.0084

Things to consider in conclusion…◦Which solutions were hypertonic and hypotonic? What evidence do you have in your data that supports this?

◦Someone observed in class that the water solutions had ‘stuff’ in it…what do you think it could be and why is it in the water?

◦Why is it important to consider the solution tonicity when it comes to cellular shape?