Plasma Membrane & Cellular Transport

http://www.i-sup2008.org/images/venue_transport.jpg

Cell Transport

A cell has to move food and wastes into and out of the cell. Materials must move through the plasma membrane which maintains homeostasis in the cell.

food

waste

food

foodfood

waste

waste

waste

Cell Transport

The Plasma Membrane surrounds the cell. How does it work?

Plasma Membrane

Boundary between the cell and its environment1. Allows nutrients into the cell2. Removes wastes and excess materials3. Maintains homeostasis: a stable internal

environment

Plasma Membrane

How does it work?1. Semi-permeable: only allows some

molecules in the cell, keeps others out

http://media3.washingtonpost.com/wp-dyn/content/photo/2006/10/15/PH2006101500491.jpg

Plasma Membrane

2. Fluid Mosaic Model: membrane is flexible, made of many pieces working together

http://www.youtube.com/watch?v=Qqsf_UJcfBc

Plasma Membrane

3. Phospholipid Bilayer: membrane is 2 layers, made of phosphates and fats (lipids) with proteins mixed in

Plasma Membrane PartsPhosphate heads – hydrophilic (like water), outside

and inside membraneFatty Acid Tails – hydrophobic (fear water), inside

membrane, like OREO creamCholesterol – prevents fats from sticking together,

stabilize membraneTransport proteins – move molecules into and out of

cellIdentification proteins – outside cell, “nametag”Support proteins – inside cell for framework,

“skeleton”

Membrane Model LabPurpose: What are the parts of a plasma membrane?Arrange your membrane parts to look like this section

of membrane. On your paper towel, label the inside and outside of the cell.

Marshmallows = phosphates Toothpicks = fatty acid chainsGummy Worms / Twizzlers= proteins Candy Corn= cholesterol

Inside cell

Outside cell#1 #2

#3

Membrane Model Lab

1. Draw model in your notes. Label proteins, lipids, phosphates, cholesterol, outside and inside of cell, hydrophobic portion.

2. What type of protein is each of the numbered arrows? How is each used?

3. Why are the marshmallows not attached to each other?

4. Where would cholesterol be found in the membrane? Why?

Model a membrane

1. Using bubble solution, show a flexible membrane. Why is this important?

2. Form an opening in the membrane with a circle of string, pop the inside. This is how a channel protein works. Move it around in the membrane. (Membrane is fluid)

3. What happens when a “wand” is pushed through the membrane?

Passive Transport

NO ENERGY required, moves molecules from high concentration to low concentration

1. Osmosismovement of water across a membrane

http://schools.moe.edu.sg/chijsjc/Biology/Diffusion&osmosis/osmosis.gif

Passive Transport – no energy required

2. Diffusionmolecules move from an area of high

concentration to low concentration

http://iweb.tntech.edu/mcaprio/diffusion-animated.gif

Passive Transport – no energy required

3. Facilitated Diffusionmovement of molecules from high concentration

to low concentration with help of membrane transport proteins

http://www.biology.arizona.edu/CELL_BIO/problem_sets/membranes/graphics/CHANNEL.GIF

High concentration

Low concentration

Passive Transport

Active Transport

Requires energyMoves molecules against concentration gradientMoves from area of low concentration to high

concentrationExamples:

gated channels, sodium/potassium pumps, endocytosis, exocytosis

Active Transport

Endocytosis and Exocytosis

http://media-2.web.britannica.com/eb-media/38/8038-004-A29C9C02.jpg

Active Transport

Example: Paramecium uses contractile vacuole to regulate water content

http://www.cartage.org.lb/en/themes/sciences/BotanicalSciences/MajorDivisions/KingdomProtista/Protists/paramecium.gif

Active Transport

Modeling Diffusion Lab

1. Make simulated agar cells in 3x3cm, 2x2cm, and 1x1cm cubes.

2. Immerse the cells in a “food” solution of sodium hydroxide (NaOH) for 10 minutes.

3. Pour off NaOH solution, rinse cells.4. Cut cells in half. Measure from outside in and record

distance NaOH penetrated into cell.Cell Side Size (cm) Distance Penetrated (cm)

Distance Not Penetrated (cm)

Diffusion Lab Questions

1. Which cell is most efficient in moving materials throughout its entire structure?

2. What are the limitations to cell size?3. How does the surface area relate to the

volume of each cell?Surface area = 6 x (side)2

Volume = length x width x height (cm3)

Gummy Bear Lab

Day 1: Measure L,W,D of bear. Place in a plastic cup and mass the bear and cup. Record in table. Fill ½ full with distilled water. Initial your cup. Place on tray. Write hypothesis of what will happen to bear overnight.

Day 2: Pour out water. Measure volume. Mass bear and cup. Record. Fill ½ full with salt water. Write hypothesis of what will happen to bear overnight.

Day 3: Pour out water. Measure mass of bear and cup. Write statement of what happened to bear from day 1 to day 3.

Day Length (mm)

Width (mm) Depth (mm)

Volume (mm3)

Mass (grams)

1

2

3

Solutions

Isotonic solution – equal concentrations of solute (salt) inside and outside cell

http://www.biologycorner.com/resources/isotonic.gif

Solutions

Hypotonic solution – less solute in solution, more solute in cell, WATER FOLLOWS SALT, cells swell

http://www.biologycorner.com/resources/hypotonic.gif

Solutions

Hypertonic solution – more solute in solution, less solute in cell, WATER FOLLOWS SALT, cells shrink

http://www.biologycorner.com/resources/hypertonic.gif

Osmosis in blood cells

http://aryatiabdul.files.wordpress.com/2008/07/osmosis2.gif

Solutions – how transport affects animals and plants

http://kentsimmons.uwinnipeg.ca/cm1504/Image130.gif

Transport in PlantsHealthy plant cells are crisp due to TURGOR PRESSURE

Wilted plant cells are flaccid due to lack of water

Transport, againDraw this in your notesOver time, water level changes to make water

concentrations equal on both sides of tube

TIME

Diffusion of water across a semi-permeable membrane = osmosis