Today is Monday, October 12 th , 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)
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Today is Monday, October 12 th, 2015 Pre-Class: Today is our first look at the cell. First, choose one of the following to answer in your notes: 1. What.
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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.
• 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
• 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…
• 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.
• 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
• 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.