Plasma Membrane & Cellular Transport

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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 food food waste waste waste waste food

Cell Transport

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

Plasma Membrane

Boundary between the cell and its environment 1. Allows nutrients into the cell 2. Removes wastes and excess materials 3. 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 Parts

Phosphate heads – hydrophilic (like water), outside and inside membrane Fatty Acid Tails – hydrophobic (fear water), inside membrane, like OREO cream Cholesterol – prevents fats from sticking together, stabilize membrane Transport proteins – move molecules into and out of cell Identification proteins – outside cell, “nametag” Support proteins – inside cell for framework, “skeleton”

Membrane Model Lab

Purpose: 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 Gummy Worms / Twizzlers= proteins Toothpicks = fatty acid chains Candy Corn= cholesterol

Inside cell #3 #1 #2 Outside cell

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. Osmosis movement of water across a membrane http://schools.moe.edu.sg/chijsjc/Biology/Diffusion&osmosis/osmosis.gif

Passive Transport – no energy required

2. Diffusion molecules 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 Diffusion movement of molecules from high concentration to low concentration with help of membrane transport proteins Low concentration High concentration http://www.biology.arizona.edu/CELL_BIO/problem_sets/membranes/graphics/CHANNEL.GIF

Passive Transport

Active Transport

Requires energy

Moves molecules against concentration gradient Moves from area of low concentration to high concentration Examples: 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/KingdomPr otista/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 (cm 3 )

Day Length (mm)

Gummy Bear Lab

Width (mm) Depth (mm) Volume (mm 3 ) Mass (grams) 1 2 3 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.

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

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Healthy plant cells are crisp due to TURGOR PRESSURE

Transport in Plants

Wilted plant cells are flaccid due to lack of water

Transport, again

Draw this in your notes Over time, water level changes to make water concentrations equal on both sides of tube TIME Diffusion of water across a semi-permeable membrane = osmosis