AP biology lesson -- Plasma membrane transport and signalingNovember 13, 2014

During today’s webquest, you should strive to achieve these learning goals:

1)Understand the mechanisms of passive and active transport

2)Understand the role of active and passive transport in the ability of neurons to communicate with other neurons via action potentials.

3)Understand the general steps and mechanisms of signal transduction (make sure you know these for lipid soluble hormones and for signal molecules that bind G protein coupled receptors).

4)Understand had neurotransmitter receptor mediated signal transduction is involved in neuron action potentials.

I will not check whether or not you wrote answers. It’s up to you to decide how best to utilize these websites for learning. If it helps you learn, write the answers; if it helps you more to run animations again after contemplating answers, thenuse that technique!

You will have a unit test on Biology in Focus chapter 5, as well as the role of transport and signaling in neuron action potentials, muscle cell contraction, and lymphocyte activation on Tuesday, 11/18. Today’s lesson addresses only neurons. Tomorrow’s lesson will focus on muscle contraction and immune system activation via the white blood cells called T helper cells. If you don’t finish this lesson in class today, then please finish it at home.

Passive transport

  1. Carrier proteins are “specific”. What does this mean?
  1. What determines whether the direction of movement of a solute is into or out of a cell?
  1. How is facilitated diffusion like simple diffusion? How is it different?

Watch the animation. Keep in mind that even though water CAN move over the membrane without a channel, moving through the aquaporin channel increases its rate of diffusion by 100’s or 1000’s of times.

  1. Why is osmosis a specialized type of facilitated diffusion?
  1. Is the net movement of water during osmosis from a hypotonic environment to a hypertonic or vice versa?

Click the diamond to watch the animation once or twice, then try the questions. In the animation, osmolarity refers to the concentration of solute (high osmolarity means high solute concentration). Keep investigating until you understand the basis for all 5 answers!

(watch this excellent video at home because you can’t access youtube at school:

Active transport

  1. Exactly how was ATP involved in the movement of the Na+/K+ sodium potassium pump?

After watching both animations, answer the questions below.

  1. What is the role of ATP in activity of the sodium/potassion ion pump?
  1. How many Na+ ions are pumped out of the cell?
  1. How many K+ ions are pumped into the cell?
  1. Do these ions move with/down or against/up their concentration gradients?
  1. Due to the action of the pump, what is normally true about the concentration gradients of K+ and Na+ in a nerve cell which has many highly active sodium potassium pumps?
  1. After watching both of these videos, explain the role of active transport proton pumps during the electron transport chain segments of both the light reactions of photosynthesis and the final aerobic stage of cell respiration. Note that the energy for these proton pumps is provided by their binding to a negatively charged and energized electrons received from the previous step of each process.

Watch the two animations above; for the second animation, just watch until it stops. Don’t worry about the part that follows the “5 day free trial”—DON’T register! The section previous to the marketing ploy is what you need to know.

  1. What is the name for cell eating? ______For cell drinking? ______
  2. Give an example of each.
  1. Protists and very simple animals, the sponges, use a process called intracellular digestion to gain nutrition. Explain how this works (hint—lysosome is involved).

Watch the animation above then answer the following questions. Also, try answering the questions at the website, and re-watch the animation if needed to determine all the correct responses.

  1. What is a first messenter?
  1. What happens to an ion channel receptor when it binds a ligand, and what are the two possible outcomes of this change?
  1. What happens to a tyrosine kinase receptor when it binds its first messenger, and what are the possible outcomes of this change?
  1. What happens to a G-protein coupled receptor when it binds its first messenger, and what are the possible outcomes of this change?

After watching the animation above, answer these questions. Also, try answering the questions at the website, and re-watch the animation if needed to determine all the correct responses.

  1. Give an example of a lipid soluble first messenger.
  1. Where is the receptor for a lipid soluble first messenger?
  1. What is the role of the lipid soluble first messenger’s activatated receptor?
  1. What is the effect of every lipid soluble first messenger?

Note that the lipid soluble first messengers were hormones made in glands of the endocrine system, then transported through blood to all cells of the body, yet eliciting responses only in cells expressing the genes for their receptors!

  1. In the animation of two balloons connected by a membrane permeable to water, but not glucose, why did the concentrations in the two balloons become more similar, but not exactly the same? (hint: balloons don’t burst as easily as an animal cell membrane, but they’re not as rigid as a cell wall)
  1. In the balloons having high permeability for water, but only a low level of permeability for glucose, why did one balloon initially swell, but then return to the size of the other balloon?
  1. Exactly how was ATP involved in the movement of the Na+/K+ sodium potassium pump?
  1. Why are sodium-potassium ion pumps so important in neurons?
  1. What event triggers a neuron’s action potential? Hint—it’s partly signaling and partly passive transport.
  1. Where and when during an action potential is exocytosis employed? Is this active or passive transport?
  1. What is a voltage gated Na+ channel? Does it employ active or passive transport? Explain the opening and closing of the channel in terms of protein conformation.
  1. Why does an action potential travel (propogate) down an axon like a wave at a baseball game?

Receptor mediated signaling, as well as Passive & Active transport during action potentials of neurons

We must be able to apply our knowledge of cell signaling and cell transport to understanding the functions of neurons. First, watch these two bioflix movies at (username nadinebrown567 password 1conceptualchemistry1

How neurons workhow synapses work

Then watch the activities at chapter 37 of Finally, watch these animations

Now, try to answer these questions.

  1. Sketch a neuron (nerve cell), labeling dendrites, cell body, axon, and axon terminus.
  1. Note that in the last animation, a pressure or motion sensitive sensory neuron (like those in the skin and those in the cochlea of the inner ear) is explained, not a neurotransmitter activated neuron. What happens when the membrane of the dendrites of these neurons are disturbed?
  1. What does the closing of the Na+ channels after many Na+ ions have diffused into the cytoplasm tell you about the effect of a highly positively environment on these channel proteins? What about the K+ channels that open when the Na+ voltage gated channels close?
  1. What does it mean to say that neurons maintain a resting voltage (or potential)? Sketch this. What is the role of the sodium-potassion ion pump in maintaining the resting potential?
  1. Why does opening of pressure/motion sensitive Na+ channels initiate an action potential? Why do Na+ ions rush into the cell so rapidly? Why does the opening of K+ channels by depolarization restore the axon’s membrane voltage (potential)?
  1. In resting neuron, does the concentration gradient favor outwards or inwards movement of Na+? What about K+? Since the cell contains both voltage gated and constantly open Na+ and K+ channels, the Na+/K+ pump is required to maintain resting potential for neurons.
  1. What fraction of a human’s energy supply is used by the Na+/K+ pump?
  1. Active transport is used at the axon terminus when the neuron releases neurontransmitter into the synapse. How?
  1. In the post-synaptic neuron, how is receptor mediated cell signaling AND passive transport involved in continuing to transfer the message delivered by the pre-synaptic neuron?
  1. Explain the role of the neurotransmitter receptor (an ion channel activated by binding of the ligand neurotransmitter), the voltage gated Na+, and the voltage gated K+ channels allows the action potential to travel like a wave in a stadium (it’s called salutatory—jumping—conduction!).
  1. How did you learn that endocytosis is involved in neural transmission?