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