do now - montville township public schools · to explain what role each macromolecule has in...
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Do Now
▪ What is the role of the cell membrane?
▪ How do you think it is able to perform this function?
Membrane and Transport
Chapter 5
Objectives
▪ To identify the components of the cell membrane
▪ To explain what role each macromolecule has in creating the membrane structure
Cell Membranes
▪ Maintain an internal environment that is different from the external environment.
▪ Regulates what molecules enter and exit the cell.
▪ “Selectively Permeable”
▪ Membranes are composed of a phospholipid bilayer.
Phospholipid Bilayer
▪ Lets break down the word.– Phospho- phosphate group– Lipid- fat– Bilayer- 2 layers
Phospholipid Bilayer
▪ The phospholipid bilayer is said to be a “Fluid Mosaic Model”.
Membrane Structure
Main Components:
- Phospholipids: primary structural component- Proteins: framework, transport, receptors, enzymes- Carbohydrates (attached to glycoproteins): cell to cell recognition - Cholesterol: stabilizes the membrane and keeps it “fluid”
Membrane Structure
Homework
Due Monday: Read and Outline 5.1-5.6
POGIL
▪ Popsicle Partners▪ This activity is an introduction of this chapter and will cover a LOT of
material. We will spend more time on each section so don’t worry if you are confused, however please call me over if you have any questions!
Pogil Review
Do Now
Objectives
SWBAT
- Differentiate between passive and active transport.- Determine which type of transport allows us to uptake molecules
necessary for life.
Types of Transport
What are the different types of molecules that need to get into and out of our cells for our survival?
Types of Transport
1. Passive Transport:a. requires NO energyb. molecules move down a
concentration gradient
2. Active Transport:a. requires energyb. molecules go against the
concentration gradient
Diffusion
- Molecules spread out evenly in an available space creating dynamic equilibrium.
- Molecules that are small and nonpolar can diffuse easily across the membrane.- Ex: Red blood cells with Oxygen
and Carbon Dioxide
Facilitated Diffusion
- Large or polar molecules must cross the membrane via a transport protein. (they are still moving down the concentration gradient)
Facilitated Diffusion
- Uses proteins- Channel Proteins: provides a passageway for large and/or charged
molecules to pass through. - Carrier/Gated Proteins: change shape to allow large/and or charged
molecules to pass through.
Factors affecting the Rate of Diffusion
- State of matter- Gas > liquid > solid
- Heat- warmer temp increases speed of
molecular interactions- Size of molecules
- bigger = slower
Osmosis
- Diffusion of water across a membrane
- Determined by molecules that are present in the solution
*Why are the water molecules the only ones moving??
Do Now
- Get with your lab partner from yesterday.- When you get to your table, turn on the hot plate. Each hot plate
should have ONE beaker of water that is filled half way on it.- Send one partner to obtain your beaker and baggie from the center
table.- Send the other partner to obtain goggles.- Make your observations about the colors you see in the beaker and
the baggie. - Perform the Benedict’s test on the water surrounding the baggie in
the beaker. Record your results and begin to answer the questions.
Objectives
1. Explain osmoregulation using real world examples.2. Compare and contrast isotonic, hypertonic, and hypotonic cells.
Osmosis
● Water always flows via osmosis from HIGH water concentration to LOW water concentration through a semi permeable membrane.
● Can move right through the phospholipids from high to low concentration (slow process)
● Aquaporins- Integral membrane proteins that allow rapid diffusion of water into and out of cells
Tonicity
- ability of a solution to cause a cell to gain or lose water.- depends on concentrations of solutes that cannot cross the
membrane relative to the concentration of solutes in the cell.
● Many organisms are able to maintain water balance within their cells by osmoregulation● This process prevents excessive uptake or excessive loss of water.● Plant, prokaryotic, and fungal cells have different issues with
osmoregulation because of their cell walls.
Questions to think about
- What would happen if you put a salt water fish into a fresh water lake?
- IV fluids usually contain dissolved solutes in them such as salt or sugar. What would happen if you were given an IV of pure water?
- Have you ever dumped salt on a slug? What happens? Why?
Tonicity
Types of Solutions
- Solutions and cells are relative to each other and are name based on the amount of solute dissolved in solution.
3 Types:
1. Isotonic: solutes are equal (therefore water is equal) 2. Hypertonic: higher solute content ( less free water)3. Hypotonic: lower solute content (more free water)
* These solution differences will have an overall effect on diffusion and osmosis.
Blood CellPlant Cell
Isotonic Solution
Cellular Structure and Function
▪Water and dissolved substances diffuse into and out of the cell at the same rate.
11,397x
Blood Cell
HypOtonic Solution▪Solution with a higher concentration of water, and a lower concentration of solute compared to the cell.
▪For a cell in this solution water diffuses into the cell, cell swells/bursts Plant Cell
13,000x
Plant Cell
HypERtonic Solution▪Solution with a higher concentration of solute and a lower concentration of water compared to the cell.
▪ If a cell is place in this solution water diffuses out of the cell, cell shrivels Blood Cell
13,000x
Think about it again...
- What would happen if you put a salt water fish into a fresh water lake?
- IV fluids usually contain dissolved solutes in them such as salt or sugar. What would happen if you were given an IV of pure water?- The IV would be hypotonic to your blood cells and cause
them to lyse.- Have you ever dumped salt on a slug? What
happens? Why?- The salt is hypertonic to the slug and causes the slug cells to
shrivel up and “crenate”
The fresh water would be hypotonic to the fish, causing lysis of the cells.
DO NOW
- Take out your tonicity homework.- Did you have any questions about it?- Do you have any questions about any other parts of this chapter so
far?- Also take out your onion plasmolysis lab.
Objectives
- Explain how active transport differs from passive transport and give examples of how it is used in our cells.
- Get clarification on anything you don’t understand for the quiz.
Onion Plasmolysis
Normal Cell:
Onion Plasmolysis
- Cell exposed to a salt solution:
- What was the solution relative to the cell? What did this cause the cell to do?
Onion Plasmolysis
If we were to add pure water back to the cell, what should happen over time?
Why? What type of solution is pure water relative to the cells currently?
Another example...
Elodea Plasmolysis
Normal cell After Salt Was Added
Active Transport
- Requires ATP- Usually goes AGAINST the
concentration gradient.- Requires proteins in order to
“pump” the molecules across the membrane.
- (*Think of a salmon swimming upstream)
Example of Active Transport
- The “Sodium Potassium Pump”- The membranes of our neurons attempt to maintain a “charge” and are said
to be “polarized”- When a stimulus disrupts that charge and ion concentrations change, the
neuron triggers an impulse- Active transport is then required to “repolarize the membrane” and
reestablish the original ion concentrations- *This requires that ions be moved against the concentration gradient and
therefore require proteins and ATP.
Sodium Potassium Pump
Sodium Potassium Pump Animation
http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html
Action Potentials and neural impulses (in case you are interested!)
http://highered.mheducation.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html
Vesicular Transport
- Uses vesicles to move substances into and out of the cell.
- Endocytosis: transport of substances into the cell (endo-enter)- Pinocytosis- transports fluids into the cell- Phagocytosis- transports solids into the cell
- Exocytosis: transport of substances out of the cell (exo-exit)- Ex: after a nerve impulse is sent along a single
neuron, it communicates to the next neuron via “neurotransmitters” which are released through exocytosis.
Neural Synapse
Review
- Membrane structure and function (study quiz)- All macromolecules and their purpose- Properties of phospholipids
- Passive Transport- Diffusion- Facilitated Diffusion- Osmosis
- Tonicity and osmoregulation- Active Transport
- Sodium potassium pump- Vesicular transport
- Labs- Dialysis Lab- Onion Plasmolysis Lab