Plasma Membrane & Cellular Transport http://www.i-sup2008.org/images/venue_transport.jpg
Feb 25, 2016
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