+ february 7, 2014 objective: to create a model of the cell membrane to explain the structure of the...

+February 7, 2014

Objective:To create a model of the cell

membraneTo explain the structure of the cell

membrane

Journal: What does it mean to have a phobia of something? What is an example of a phobia?

+Key Terms

What do you think are the definitions of the following words?HydrophobicHydrophilic

+Key Terms Defined

Hydrophobic: Literally means fear of waterMolecules that are hydrophobic repel

water and try to stay away from water

Hydrophilic: Literally means water lovingMolecules that are hydrophilic are

attracted to water and tend to be found next to water

+Phospholipids

The structure of the phospholipid molecule generally consists of two hydrophobic tails and a hydrophilic head.

+Phosphate Head

Hydrophilic

Polar (has a charge)

Made of phosphate

+Two Fatty Acid Tails

Hydrophobic

Nonpolar (doesn’t have a charge)

Made of fatty acids

+Structure of the Cell Membrane

Phospholipids make up the cell membrane of cells.

+Phospholipid Cell Membrane Activity

Both inside and outside the cell contain water, so how do you think phospholipids are arranged to make a cell membrane?

Keep in mind that phospholipids contain hydrophilic heads and hydrophobic tails.

+Cell Membrane Structure

Phospholipids form a double layer called a Phospholipid Bilayer with the phosphate groups on the outside and the fatty acid tails in the middle

This happens because there is water inside and outside of the cell, so the water loving phosphate end is always by the water

+Structure Determines Function

The cell membrane structure helps it regulate what can and cannot pass through the phospholipid bilayer

+Selectively Permeable

The cell membrane is selectively permeable, meaning that not everything can go across it.Only certain things can get into the

cell and only certain things can leave the cell

+What can pass through the membrane?

This allows only small, nonpolar substances to pass directly through the phospholipid bilayer

All other substances are repelled by the nonpolar fatty acids, so they cannot go directly through the phospholipid bilayer

+Other Ways to Pass Through the Phospholipid Bilayer

The cell needs to let other things in and out of the cell so it uses membrane proteins to allow specific substances across the membrane at specific times

Membrane proteins can be found on top of or within the phospholipid bilayer

http://www.youtube.com/watch?v=LKN5sq5dtW4

+Types of Membrane Proteins

+Receptor Proteins

Found on the outside of your cells

Enable a cell to sense its surroundings by binding substances outside the cell Allows the cell to react

to its surroundings

+Cell-Surface Proteins

Similar to a nametag

Protein attached to a chain of carbohydrates attached to the cell membrane used to identify each type of cell

+Transport Proteins

Allows certain necessary substances that cannot pass through the cell membrane into and out of the cell

+Transport Proteins

Channel Proteins: Serve as a tunnel through the lipid bilayer that allow SPECIFIC ions, sugars, and amino acids to pass through the membraneEx: The channel for sodium ions does

not allow sugars to pass through

+Transport Proteins

Carrier Proteins: Only transport substances that fit within their binding site through the cell membraneCarrier protein binds to a specific substance

on one side of the cell membrane, changes shape and allows the substance out on the other side of the cell membrane

+Daily Activities

Day 1 – Egg Lab

Begin Cell Membrane Model

Homework: Cell Membrane Labeling Worksheet

+February 7, 2014 Objectives:

To differentiate between osmosis and diffusion

To describe how molecules can move down a concentration gradient

Journal: What do you think the following words

mean? Equal Concentration Diffuse

If the Monksville dam broke, what would happen to the water in the Monksville Reservoir?

+Cell Transport

+Passive Transport Vocabulary

Equilibrium: when there is an equal number of molecules on both sides of the cell membrane

Concentration: the amount of a particular substance in a given volume

Concentration Gradient: When there is a higher concentration of a substance on one side than the other

Diffusion: When a substance moves from an area of higher concentration to an area of lower concentration

+Types of Transport

Passive Transport: does not require energy to move substances across the cell membrane

Active Transport: requires energy to move substances across the cell membrane

+Passive Transport

When substances enter or leave the cell by diffusing across the cell membrane down their concentration gradient

The direction the substances move depends on the concentration gradient

+Types of Passive Transport

Simple Diffusion

Facilitated Diffusion

Osmosis

+Simple Diffusion

When small, nonpolar (uncharged) substances pass directly through the phospholipid bilayer from an area of higher concentration to an area of lower concentration

Ex: If there is more oxygen outside the cell than inside the cell, it will diffuse across the lipid bilayer and into the cell.

+

+Facilitated Diffusion

Substances that cannot pass directly through the membrane are helped to diffuse through the membrane using transport proteins

+Osmosis

Facilitated diffusion of water from an area of higher concentration to an area of lower concentration

Allows the cell to maintain water balance as their environment changes

+Water Channels

Since water is a polar substance, it does not directly diffuse across the cell membrane

So the cell has specific protein channels that only allow water to pass through called aquaporins

+Predicting Water Movement

The direction the water moves depends on the concentration of the cell’s environment

+Hypertonic

Water moves out of the cell

There is more solute outside the cell than inside the cell

The cell loses water and shrinks

+HypotonicWater moves in

There is more solute inside the cell than outside the cell

Cell gains water and expands

+Isotonic

There is the same concentration of water inside the cell and outside the cell

Equilibrium is reached

Cell stays the same size

+Daily Activities

Egg Lab Day 2 – Place eggs in various solutions

Finish Cell Membrane Model

+February 11, 2014

Objectives:To differentiate active transport from active

transportTo describe how active transport moves

molecules

Journal:How is active different than passive?

+Active Transport

Transport of substances against their concentration gradients

Requires energy usually in the form of ATP

+Use of Carrier Proteins as Pumps

Carrier proteins require energy to pump substances across their concentration gradient

+Sodium-Potassium Pump

Sodium ions inside the cell bind to the carrier protein which changes shape and releases sodium ions outside the cell membrane

As a result a phosphate group is released from the pump, returning the channel protein to its original shape, and releasing potassium ions inside the cell

For every three sodium ions pumped out, two potassium ions are brought inside

This prevents sodium from building up inside the cell, which would cause the cell to burst due to osmosis bringing in too much water

+Vesicles

Large substances are too big to cross the membrane in channel proteins so they use vesicles

Vesicle membranes are lipid bilayer, so they can bud off from the cell membrane or fuse with it to move large substances in or out of the cell

+Endocytosis

The movement of large substances into a cell using a vesicle

The cell membrane forms a pouch around the substance that closes and then pinches off inside the cellPinocytosis: also known as cellular

drinking, engulfing liquid particlesPhagocytosis: engulfing solid particles

+Exocytosis

The movement of large substances out of a cell using a vesicle

Vesicles inside the cell fuse with the cell membrane and are released outside the cell

Used to transport proteins modified by the Golgi apparatus, excrete wastes, or remove bacteria

+Daily Activities

Day 3 – Finish Egg Lab