BIO 311C Lecture Notes - Lecture 14: Chemical Potential, Resting Potential, Active Transport

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2 Oct 2016

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Document Summary

Membranes need to be permeable for cells to communicate with other cells and for gas exchange to occur. Non polar small things can pass through a membrane easily: ex: hydrocarbons, co2, o2, small lipids. Some polar molecules can go through a membrane (but only really small polar things: ex: water, but these polar molecules move really slowly. It is really hard for ions to pass through the membrane because they are covered in water molecules (in a hydration shell) Aquaporin transmembrane channel: allow water to quickly pass through the membrane. Osmosis: water moves from high water potential to low water potential, water potential is the amount of free water molecules that are free to interact with solutes. Isotonic- same amount of solute in both solutions. Hypertonic- one solution has more solute than the other. Hypotonic- one solution has less solute than the other. Transport proteins are substance specific only let one particular thing to pass.

Related Questions

Cell Membranes Lab Report

Diffusion

Compare the following terms: solvent, solute, andsolution.

Go to Lab, Section I, Exercise 1 to explore the factorsinfluencing the rate of diffusion and complete the following:

Predict how molecular mass and temperature may affect theoutcome of this experiment.

Record the data from information in the Lab in the tablebelow.

Time (min)	Diameter (mm)
Time (min)	5Â°C MB	5Â°C PP	23Â°CMB	23Â°C PP
0
15
30
45

Construct a line graph of the data from the table above. Yourgraph should include labeled axes, units, and a legend indicatingwhich treatment is presented. Sign, date and prepare an image ofyour graph and include it with this lab report.

Osmosis

Go to Lab, Section II, Exercise 2 to view a demonstration ofosmosis and answer the following questions:

Describe the net movement of water in osmometer 1.

How is the movement of water molecules related to theconcentration gradient of the solution?

Go to Lab, Section II, Exercise 3 to observe the effect ofsolute concentration on the rate of osmosis. Answer the followingquestions:

Was the net movement of water in bags 1 to 4 into or out of thebags?

Explain the results from bags 4 and 5.

Selective Permeability of Membranes

Go to Lab, Section III, Exercise 4 to learn about theimportance of selectively permeable membranes, then complete thetable and answer the following questions:

	Contents of Beaker
	0 Min	30 Min
Starch
Chloride ion

Which substances diffused through the dialysis membrane?

How does dialysis tubing model the selective permeability of aplasma membrane?

Tonicity

Go to Lab, Section IV, Exercise 5 and 6 to observe plasmolysisin Elodea cells and tonicity in red blood cells. Summarizethe concept of tonicity using blood and Elodea cells asexamples. Your description should incorporate these terms: turgid,plasmolysis, hemolysis, and crenation.

Cells	Isotonic Solution	Hypertonic Solution	Hypotonic Solution
Elodea
RBC

Based on your previous work, reproduce the table below and drawan illustration of a single cell in each box. Include arrows toshow the direction of water flow relative to each cell and dots tosymbolize solutes. Sign, date and prepare an image of your drawingand include it with this lab report.

Cells	Isotonic Solution	Hypertonic Solution	Hypotonic Solution
Elodea
RBC

Summary Questions

Compare diffusion and osmosis. Give an example of each.

2. In which direction will osmosisoccur if a 15% sugar solution is separated from a 25% sugarsolution by a selectively permeable membrane?

3. Why did osmosis, but not diffusionof sucrose molecules, occur across the dialysis membrane containing20% sucrose solution?

4. You are having a party and thecelery is limp. What might you do to make the celery crisp (turgid)again? What will occur in the cells?

5. A small amount of fertilizer(mineral salts) will stimulate plant growth, but over fertilizationcan kill plants? Why?

6. Michael adds sugar to his coffee.Explain what in this drink is the solvent, solute, and solution.

7. You add a cube of sugar to yourdrink. How could you speed up the diffusion of sugar moleculeswithout stirring?

8. How is dynamic equilibriumestablished within a solution?

amberdeer449

1. Which of the following best describes a condition where a membrane separates two solutions that are NOT in equilibrium?

a rainbow

B	equilibrium

C	a homogeneous solution

D	neighboring solutions that have unequal concentrations of molecules

2. In this lab, we will use dialysis tubing to....

A	simulate biological membranes

B	separate blood from urine

C	turn starch blue

D	turn starch brown

3. Biological membranes have different types of pores and channels, and different permeability to small molecules depending on size and charge. In this lab, you can assume that the dialysis tubing we are using are permeable to....

starch

B	water and potassium iodide

C	complex sugars

D	small animals

4. Kinetic energy is a property of the atom, and also of more complex structures such as molecules. You can actually see kinetic energy of non-living things in action under the microscope. When we visualize this, we call what we see...

diffusion

B	Brownian motion

osmosis

D	all of the above

5. One word to describe the effect of water diffusion across a membrane, which alters the water pressure on one side of the membrane with respect to the other is....

osmosis

lysis

aquaporin

D	equilibrium

6. Suppose that you place a red blood cell in a hypertonic solution containing penetrating molecules. In this environment, you would expect the cell to eventually

A	swell and burst

shrink

C	remain the same in size

D	photosynthesize

7. For the "egg lab", what is the main objective?

A	to determine which egg has more mass

B	to determine which egg is hypertonic to the other

C	to determine which solution the egg is placed in is hyper- or hypo-tonic solution

D	to determine which egg is isotonic with the egg

8. The main difference between a 'prediction' and a 'hypothesis', is that predictions....

A	are framed as an "if...then...because" statement

B	are framed as a general statement

C	are framed as an "always....true" statement

D	are framed as an "correct....incorrect" statement

9. Read each of the following procedural steps for plasmolyzing Elodea sprig and then select the correct order below.

Locate a region of healthy cells and sketch a few adjacent cells

Sketch the plasmolyzed cell

While touching one corner of the coverslip with a piece of Kimwipe to draw off the
water, add a drop of concentrated salt solution to the opposite corner

Obtain a leaf from an Elodea or Water sprite plant

A	4, 2, 3, 1

B	3, 1, 4, 2

C	2, 3, 1, 4

D	4, 1, 3, 2

BIO 311C Lecture Notes - Lecture 14: Chemical Potential, Resting Potential, Active Transport

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