Today is Monday, October 12 th, 2015 Pre-Class: Today is our first look at the cell. First, choose...

Today is Monday,October 12th, 2015

Pre-Class:Today is our first look at the cell. First, choose one of the

following to answer in your notes:

1. What do the terms diffusion, osmosis, or passive/active transport mean to you?

2. Have you ever had Aquafina or Dasani water? Why is it different from Poland Spring, for example? Do you know the name of the

process?

Also, take a worksheet from the Turn-In Box and get a paper towel for your pair.

In This Lesson:Cell Membranes

and Cell Transport

(Lesson 3 of 5)

Today’s• Cell membrane [Part 1]

– Form• Brief aside on blood type• Cell transport [Part 2]

– Function• Doodling on whiteboards

– Yes, you will be making pictures.• Where is this in my book?

– Academic: P. 182-189– Honors: P. 79 and following…

http://www.greatscopes.com/objectives.jpg

By the end of this lesson…

• You should be able to describe the structure and function of the cell membrane.

• You should be able to identify the direction and energy-intensive movement of particles or water.

But First, a Word About Size…

• Ye Olde BioScale

• What It Looks Like• Scale of the Universe

Osmosis and DiffusionPre-Class

• What did you come up with?– We will talk about the details of these

processes today and later in the week.• One other thing…

– When you hear me mention an organic molecule today, raise your hand.• Keep your ears open!

The Cell Membrane• Like the “shell” of the cell.• Also called the plasma membrane.• Double layer of phospholipids called a

bilayer.

http://api.ning.com/files/bjQpqLaT64H6U9Rm1cTtQzE8e7iMnMN*e7NCiUPA*ly2QfxrMD-yIx3-4bZ494uPFWMBd4jtn3cnGophzG2Rj1i*8RZJLtZh/et2.jpg

• Separates the cell’s cytoplasm from the extra-cellular matrix.• ECM

• Which one is outside, which is inside?

Permeability

• Some things are “impermeable:”– Raincoats, balloons, brick walls.

• Some things are “permeable:”– Air, water.

• Some things are “semi-permeable:”– Nets, gates, cell membranes.

• Semi-permeability is sometimes called selective permeability.

The Phospholipid Bilayer• Most plant and animal cells

have a double-layered cell membrane called a phospholipid bilayer.– The phospholipid bilayer acts

as its own gate.• Because the cell is in and

made of water, a polar substance, the non-polar tails stay on the inside of the layer.– This polar/non-polar deal

makes the phospholipid amphipathic.http://textbookofbacteriology.net/themicrobialworld/phospholipid_bilayer.jpg

Polar ----------->

Non-Polar

Polar ----------->

PPhospholipids?

• Fun fact: A phospholipid is actually just like a triglyceride molecule…

• …but it’s usually unsaturated…

• …missing a fatty acid chain (diglyceride)…

• …and with a phosphate group.

Glycerol

Molecule

Fatty Acid

Chains

http://bioweb.wku.edu/courses/biol115/wyatt/biochem/lipid/P-lipid.gif

What It Looks Like

http://micro.magnet.fsu.edu/cells/plasmamembrane/images/plasmamembranefigure1.jpg

Modeling the Cell Membrane

• Time for a class bonding experience.– The Classroom Cell!

http://farm1.static.flickr.com/76/174946884_64a0b8b304.jpg

http://textbookofbacteriology.net/themicrobialworld/phospholipid_bilayer.jpg

• So to summarize, you are a phospholipid.• You have a polar [hydrophilic] “head” (your

upper body) and a non-polar [hydrophobic] “tail” (your legs).• The desks are like the imaginary dividing line

between polar and non-polar.

PolarNon-Polar

PolarNon-Polar

Now for the Proteins

• Membrane proteins are embedded in some places in the cell membrane. They might have one of many jobs:– Marker Proteins– Receptor Proteins– Enzymes– Transport Proteins

http://library.thinkquest.org/C004535/media/cell_membrane.gif

And we return to the model…

• More “Classroom Cell!”

Embedded Protein!

There’s more…

• Attached to some proteins are carbohydrates (remember them?) that help in cell-cell recognition.

And we return to the model one last time…

• More “Classroom Cell!”

Okay, one last thing…

• Cell membranes are fluid.– What does this mean?

• The cell’s phospholipids and embedded proteins flow around the membrane and are in motion.– Called the Fluid Mosaic Model.

• A certain lipid (actually, a steroid) can slow down or stop this fluidity.– Do you know what it is?

http://www.herdaily.com/blogimg/health/c----.bmp

Fluid Mosaic Model

• Remember, it moves!

Challenge Question• We know that carbohydrates are attached

to proteins in the cell membrane so that other cells can identify them.

• What do you think might happen if a cell lost its carbohydrate receptors in your body?

Blood Type

• For a look at how important these small signal molecules are, we’ll look at blood type.– Anyone know their blood type in here?

• We’re going to keep blood type simple for today, so let’s assume there are only four total blood types:– A, B, O, and AB.

Blood Type• Each red blood cell (except O) has a specific

kind of receptor on it (in this case called an antigen).

http://lomalindahealth.org/health-library/graphics/images/en/19450.jpg

White Blood Cells• You also have white blood cells (leukocytes)

– they’re like angry policemen in your blood vessels.

http://www.journaldunet.com/science/biologie/dossiers/07/immunite/lymphocyte.jpg

Receptor Receptor

Receptor

Receptor

Receptor Receptor

Receptor

Receptor

Receptor

Receptor Receptor

Receptor

Receptor

Receptor

Receptor

Receptor

Receptor

Blood Type

• The wrong type of blood cell receptors causes agglutination (clumping) .– Example: My dad has Type A blood. If you give

him Type B blood, the white blood cells will treat it as an invader.

– Type O blood has no antigens so anyone can receive it.• More on blood when we get to the Genetics unit.

Micro Assignment

• Tear a small piece of paper out of your notebook, write your name on it, and answer this question:– Which organic molecules play a role in the cell

membrane? What roles do they play?

Molecular Transport [Part 2]

Question:You have a sealed container holding

one liter of pure oxygen (O2). You set the container on a table and leave it

alone. After one week, are the oxygen molecules moving? Why or

why not?

http://www.electronichealing.co.uk/resources/Image/oxygen_drops.jpg

Molecular Movement

• Molecules are always in motion.– Gas, liquid, and solid.

• Molecules only stop moving at absolute zero.

• So, even after a week (or two or three), the oxygen molecules would still be bouncing around.

Predictive Doodling

• Today we’re going to do something I’m calling “Predictive Doodling.”

• It’s like the Challenge Questions we do on the whiteboards, only you’ll be drawing instead of writing.

• I’ll give you the “before,” you give me the “after.”

Before• Your whiteboard is a square container of water.• The dots are dissolved solutes.• What happens next? Talk to your partner – then

draw it.

Diffusion Analogy

• Imagine for a second that at the beginning of class I jammed all of you into the corner of the room.

• Then, I just said, “Okay, relax,” and let you do what you wanted.– Would all of you stay put or would you spread

out?

Note Organizer

• Use this Cell Transport worksheet in place of your notebook for now…

Now let’s take a look atwhat the science says…

• Diffusion is the passive “spreading out” of particles of a substance until the particles are spread out equally.– “Passive” meaning “no energy required.”– Diffusion is a form of passive transport.– Heat generally makes diffusion go faster.– Let’s try a little demo or two…

Diffusion Demos

• Diffusion in Water• Diffusion in Air

Diffusion

http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion.gif

Concentration Gradient• Concentration refers to the amount of a substance in a

certain area.• Particles diffuse down their concentration gradient.

– What does that mean?• In passive transport, particles always go from an area

of high concentration to an area of low concentration.• Fun Fact: Passive transport occurs in part to satisfy the

second law of thermodynamics, AKA entropy.

Concentration Gradient

Warning:SteepGrade

High

Low

Concentration Gradient

HighConcentration

LowConcentration

Concentration Gradient

In Passive Transport, particles move from areas of high concentration to areas of low concentration.

Substance

Predictive Doodling Again• The line in the middle is permeable to

water, but not to solute. What happens next?

Osmosis• Osmosis is basically the same thing as diffusion,

only with water molecules and some form of a barrier.– Osmosis is another form of passive transport.

• Just like in diffusion, in osmosis, water moves from areas of high water concentration to low water concentration.

• Or, water moves from areas of low solute concentration to areas of high solute concentration.

Osmosis

• Which drink has more liquid in it?

ICE

ICE

ICEICE

Drink A Drink B

Osmosis in a U-Tube

http://www.biologycorner.com/resources/osmosis.jpg

Which side has more water on it?

Side A Side B

Osmosis in Carrots

• Remember when I put the carrots in these beakers?– They were roughly equal carrots at the time.

• For the carrot in the salt water, there is more solute outside the carrot than inside the carrot.– Which way does the water go?– What kind of change can we expect to find in

the carrots?

Tonicity

• Hypertonic solution– Relatively more solute than surroundings.

• Water flows TOWARD a hypertonic solution.

• Hypotonic solution– Relatively less solute than surroundings.

• Water flows AWAY FROM a hypotonic solution.

• Isotonic solution– The same amount of solute as the surroundings.

• No net water change.

Isotonic Solutions

• Water does not experience a net movement in isotonic solutions.– There is no concentration gradient.

Substance

No concentration gradientNo net movement of water

And now, I present to you…

• …the key to EVERYTHING!!!!!!*– *osmosis-related.

• Draw this in your notebook. Make it BIG.

Hypotonic HypertonicH2O Flow

What’s the connection?

http://upload.wikimedia.org/wikipedia/commons/thumb/e/e3/Erythrozyten_und_Osmotischer_Druck.svg/450px-Erythrozyten_und_Osmotischer_Druck.svg.png

Blood hypotonic, surroundings hypertonicIsotonic solutionsBlood hypertonic, surroundings hypotonic

Osmosis Videos

• Egg Osmosis• Onion Osmosis• Gummi Bear Osmosis

Osmosis in Plant Cells

http://upload.wikimedia.org/wikipedia/commons/thumb/a/ab/Turgor_pressure_on_plant_cells_diagram.svg/2000px-Turgor_pressure_on_plant_cells_diagram.svg.png

Osmosis in Plant Cells

• As we will soon learn, plant cells are good at holding water.

• If they’re placed in a hypertonic solution, however, they lose water and wilt.– Their cells undergo plasmolysis.

• Place them in a hypotonic solution and they will swell slightly, like a garden hose with water.– Their cells become turgid.– In animal cells, without a cell wall, the cell may burst

in a process called cytolysis.

Osmosis in Kidneys

http://classes.midlandstech.edu/carterp/Courses/bio211/chap25/Slide18.GIF

Osmosis in Kidneys

• The proximal Loop of Henle is the part of the nephron (kidney component) responsible for re-absorbing water from urine.

• With this in mind, would you guess that desert animals have larger or smaller Loops of Henle than other animals?

Osmosis in Kidneys

http://www.answersingenesis.org/assets/images/articles/cm/v26/i3/rats.jpg

Osmosis in Merriam’s

Kangaroo Rats

http://www.bio.davidson.edu/Courses/anphys/1999/Chisholm/nephron1copy.wc2.jpg

One last note…

• If you buy a car for $1000 and sell it for $3000, how much profit did you make?• $2000

• If you take two steps forward and three steps back, how many steps have you moved forward?• -1

• These are examples of net gains and losses.• How many steps did you take (total)?• 5 (but this is not your net steps)

One last note…

• Remember that question we did about oxygen gas molecules?

• Molecules, especially of liquids and gases, constantly move or vibrate. They do this without adding any energy.

• Even after diffusion or osmosis has stopped, the molecules are still moving.

Equilibrium

• For things like diffusion and osmosis, eventually the solutes reach a point where there is no net change in molecule movement.– This is equilibrium.

• We call it “dynamic equilibrium” because the molecules are still moving, but there is no net change in concentration or movement.

Equilibrium

• When dynamic equilibrium is reached, diffusion and osmosis stop.– Molecular motion continues, though.

1.0% Sugar

0.50%Sugar

0.75%Sugar

0.75%Sugar

WATER

WATERWATER

WATER

Net Water Flow Inward No Net Water Flow

Osmosis Practice Problems

• First, let’s do these as a class.• Then, log-in to Quia.• Take the quiz labeled Osmosis Practice

Problems.– These aren’t easy. That’s why this isn’t graded

and we’ll be taking it a few times.– I encourage you to work together.

By the way…

• Dasani and Aquafina use a process called reverse osmosis.– They make water go from high solute

concentration to low solute concentration – the opposite direction!

– This is part of their purification process.– Why do they do this? Because their water is

actually just purified tap water!

Closure [Part 1]

• Find a blank sheet in your notebook for a nice little concept map of what we’re doing!

Closure [Part 2]

http://trendliest.files.wordpress.com/2008/09/1b442cec-5d9e-4d51-89ff-7b3e0ab55e9a_450.jpg

What’s wrong with this picture?Diffusion

Diffusionand Membranes

• Diffusion occurs across the cell membrane without much trouble for small molecules.

• For some things, water included due to the non-polar inner section of the membrane, diffusion can’t really happen well.

• Some molecules are too large or charged or polar/non-polar to just fit right through.– They need help.

Facilitated Diffusion

• When a molecule needs help to diffuse, (but does NOT need energy), the process is called facilitated diffusion.

• Basically it just means that a special channel protein had to let the molecule in because it couldn’t fit elsewhere.

Facilitated Diffusion

http://bbwiki.tamu.edu/images/8/8d/Facilitated_diffusion.jpg

Channel Protein

http://upload.wikimedia.org/wikipedia/commons/thumb/2/2f/Ion_channel.png/350px-Ion_channel.png

Facilitated Diffusion Example

• Nerve cells:

http://www.columbia.edu/cu/psychology/courses/1010/mangels/neuro/neurosignaling/ChannelsPump.gif

Facilitated Diffusion Example

Practice Problems

• Use your computer for the following activities and quiz in this order:– Diffusion/Osmosis Battleship [Quia]

• Play till you win– Osmosis Virtual Lab [Paper]

• More information next slide…– Osmosis Practice Problems [Quia]

Osmosis Virtual Lab

• Visit this website:– http://www.glencoe.com/sites/common_assets/science/

virtual_labs/LS03/LS03.html– Found in Biology Links – can be run from my website too

(Osmosis Virtual Lab).• Use the simulation to run through the various osmotic

scenarios shown on your worksheet.– Note: If you run this from my website and not from the

Glencoe site, you won’t get the “directions” on the left side of the screen, but you won’t need ‘em, really.

• Don’t turn in the lab today – it’s a study tool for now.

Osmosis Gizmo• [Log-in Instructions]• You’re looking for the Osmosis gizmo• Also open Quia for the Osmosis Gizmo in a new

tab.• When finished with the lab, open the Quia

activity called Osmosis Gizmo Lab Cloze.

Active Transport

• In short, active transport is the movement of a substance up or against its concentration gradient.– Substance moves from a low concentration

area to a high concentration area.• This requires energy!

Concentration Gradient

HighConcentration

LowConcentration

Concentration Gradient

Passive Transport

Substance

Concentration GradientHighConcentration

LowConcentration Concentra

tion Gradient

Active Transport

Sub

stan

ce ENERGYNEEDED!

Active Transport

http://www.biology4kids.com/files/art/cell2_active1_240x180.gif

Paths for Active Transport• Three processes using the membrane:

– Molecular Transport: Pumping stuff in/out using membrane proteins.

– Endocytosis: Bringing stuff into the cell in cell membrane packages.• Phagocytosis: “Cell eating” – bringing in solids (big stuff)• Pinocytosis: “Cell drinking” – bringing in liquids (small

dissolved stuff)– Exocytosis: Dumping stuff out of the cell in cell

membrane packages.• Fun fact: Endo-/exocytosis are sometimes called

vesicular transport.

One Way: Using a Pump• A pump uses a channel protein in the membrane.• Called “Molecular Transport” by your book.

http://www.soton.ac.uk/maths/img/research/applied/Scheme_sodium-potassium_pump-en.png

Endocytosis/Exocytosis

http://www.linkpublishing.com/exocytosis5.jpg

Active Transport

• These two main processes of active transport (pumps or endo/exocytosis) are important!

• Used in signaling:– Exocytosis/Endocytosis: Chemical Signaling

• Hormones– Molecular Transport: Electrical Signaling

• Nervous System

For Example:Protein Receptors

http://upload.wikimedia.org/wikipedia/commons/2/2f/Second_messenger_pathway.png

How this is used…

http://www.topicsplanet.com/wp-content/uploads/2009/09/10703.jpg

Came up when I Googled

“Beta Blockers”http://www.dr...b.com/images/ha.jpg

Heroin addict

Video!

• CrashCourse – Membranes and Transport

A “Big-Picture” Example: Neurons

• Whenever a nerve cell transmits an impulse (called an action potential), cell transport occurs.

• You won’t need to know this for this class, but here’s a look at how it works.– Just in case you were thinking cell transport

isn’t that important.

A “Big-Picture” Example: Neurons

1. Neurons exist in a “resting state” making them negative. To keep this negative charge, the neuron actively pumps out Na+ ions. It pumps in some K+ ions.

2. The neuron’s Na channels open, allowing Na+ ions to diffuse into the cell, making the cell more positive.

3. Eventually, changes in voltage potentials cause K channels to open, allowing K+ to diffuse out of the cell, making the cell more negative and eventually returning the cell to normal.

4. The neuron’s action potential travels down the axon to the axon terminal. There, the neuron allows Ca2+ ions to diffuse into the cell, which releases neurotransmitters by exocytosis into the synaptic cleft.

5. The process continues in the next neuron (or until a muscle is reached). The first neuron returns to resting state and the process repeats.

A “Big-Picture” Example: Neurons

http://4.bp.blogspot.com/_G7_c3nIq9A4/TLkLBPp0CWI/AAAAAAAAACM/E_fRxEwm-H0/s1600/myelinsheaths.gif

Closure

• Part 1: Let’s finish the cell transport concept map!

• Part 2: TED: Ethan Perlstein - Insights into Cell Membranes Via Dish Detergent

• Part 3: WhipAround