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Chapter 12 Study Guide -- Jyoti

by: Markiesha Notetaker

Chapter 12 Study Guide -- Jyoti BIO 2600

Marketplace > Wayne State University > Biology > BIO 2600 > Chapter 12 Study Guide Jyoti
Markiesha Notetaker
GPA 3.4

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About this Document

These are notes from Chapter 12. Information from this study guide will be on Exam 3 as well as the final. Notes are taken both from lecture notes and the book. Hope it helps!
Intr To Cell Biology
Dr. Jyoti Nautiyal
Study Guide
Biology, cellular biology
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This 6 page Study Guide was uploaded by Markiesha Notetaker on Monday April 18, 2016. The Study Guide belongs to BIO 2600 at Wayne State University taught by Dr. Jyoti Nautiyal in Winter 2016. Since its upload, it has received 171 views. For similar materials see Intr To Cell Biology in Biology at Wayne State University.


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Date Created: 04/18/16
  Chapter 12 Study Guide      How things move throughout the membrane  Small uncharged molecules   ● Examples are O2 and carbon dioxide. They are able to dissolve through the membrane  by themselves  2. Uncharged polar molecules   ● They can go through the membrane if they are small enough   ● Examples are water and ethanol  3. Charged molecules   ● These cannot go through the membrane, no matter how small     Concentrations of ions in the cell  Sodium is most plentiful outside the cell  Potassium is most plentiful inside of the cell  Sodium is balance with negative Chlorine (outside the cell)   Potassium is balanced by other ions and proteins inside the cell.     Concentration gradient and Membrane potential influence   For uncharged molecules, only concentration gradients affect them.   For charged molecules, both concentration gradients and membrane potentials influence them.  The inside of the cell is usually negative and tends to pull positive ions into the cell and push  negative ions out.   Concentration and voltage gradients work together  ● Example) Sodium which is positively charged and more abundant outside of the cell so  the concentration gradient wants it to come into the cell as well as the voltage difference  since the inside of the cell is usually negative   Concentration and voltage gradients work against each other  ● Example) Potassium is more abundant inside of the cell so the concentration gradient  wants it to go out but the voltage difference would favor for it to stay inside.     Osmosis   Water moves towards areas of high solute concentration (low water).   Some cells eliminate excess water using vacuoles that discharge water contents to the exterior.   Hypotonic­ concentration of solute is higher in cell causing water to flow inside  Hypertonic­ concentration of solute is higher inside the cell, causing the water to flow outside  Isotonic concentration of solute is the same inside and outside the cell           Transporters  Have conformational changes when transferring solutes across the membrane  Very specific to the type of solute it binds     Passive Transport Proteins  Example is glucose uniporter   Glucose is uncharged and the direction that it is transferred can go both ways.   This is based solely on concentration gradient because it is uncharged.  ● When glucose is abundant outside of the cell, the sugar binds to the transporter and is  released inside of the cell   ● When blood glucose levels are low, liver cells produce lots of glucose (inside the cell)  and then glucose is transported out of the cell     Active Transport Proteins (pumps)  These carry solutes against their electrochemical gradient.  1. ATP­driven pumps­ hydrolyzes ATP to drive uphill transport   a. Sodium potassium pump  2. Coupled Pumps­ uses energy from transporting a solute downhill to transport a solute  uphill   a. Sodium glucose pump   3. Light­driven pumps­ found mostly in bacteria and uses light energy to drive uphill  transport   a. Bacteriorhodopsin     Coupled Pump  Example is Glucose­Sodium pump  ● A glucose uniporter pumps glucose passively from the cytosol into the blood  ● A sodium­glucose symporter also pumps sodium and glucose from the gut lumen into  the cytosol (glucose going up its concentration gradient, and sodium   ● The symporter is located at the apical side (from inside of the gut lumen)   ● The uniporter is located at the basal and lateral domains of the plasma membrane.   ● This is driven by the ATP­driven sodium pump that makes sodium go outside of the cell       Sodium potassium pump (ATP driven)  Transports sodium out of the cell and carries potassium in   The pump keeps the sodium concentration about 10­30 times lower in cell than outside. The  concentration gradient works together with the membrane potential to pull sodium back into the  cell.   1. Sodium is inside cell. Bind to pump  2. Pump hydrolyzes ATP to change confirmation   3. New confirmation lets sodium outside of the cell  4. Potassium bind to the pump  5. Pump dephosphorylates   6. Ejects potassium and returns to original confirmation     3 sodiums are pumped outside and 2 Potassiums a ​re pumped inside     Calcium Pump (ATP driven)   Calcium is more abundant outside of the cell but is very important because an influx of calcium  in the cytosol is used to trigger cell processes. ATP driven pumps drive calcium outside of the  cytosol     H pumps (ATP driven)  Plants, fungi, and bacteria utilize hydrogen pumps to pump hydrogen out of the cell, making the  medium outside of the cell acidic.   In lysosomes, there are H pumps that makes the protons go inside thus making it more acidic.               Ion Channels    Channels allow passive movement of small water­soluble molecules into or out of the cell.   Ion channels  ● Permits some inorganic ions to pass but not others.   ● Ion channels are not always open (gated)   ● These do not undergo conformational changes   ● This is only passive transport     Membrane potential   The plasma membrane contains potassium leak channels that randomly open and close.  Potassium has a tendency to move out of the cell, leaving the inside of the cell negative.   ● In animal cells the resting membrane potential is a reflection of the potassium gradient  across the membrane because of the leak channels that leave the membrane realy  permeable to potassium     Types of Ion Channels   1. Voltage gated­ opened by membrane potential   2. Ligand gated­ controlled by binding of some molecule   3. Mechanically gated­ opened by a mechanical force   a. Example) hearing     Ion channels and cell signaling   A neuron needs to receive, integrate and transmit signals.     Action Potentials  1. he plasma membrane d ​epolarizes ​gets less negative) and causes Sodium channels to  open, allowingsodium into the cell causing the inside of the cell to depolarize more.   2. Membrane potential goes from ­60 to +40   3. At +40 the sodium channels adopt an inactivated state until the membrane potential is  back to resting value  4. Voltage gated potassium channels allow for the membrane to go back to resting value  by allowing​otassium to flow out of the cel​    5. Once back at a resting value does sodium pumps take a close state rather than an  inactivated state  Calcium channels help to release Neurotransmitters   The presynaptic and post synaptic clefts are separated by a synaptic cleft (about 20 nm). The  electrical signal is converted into a chemical signal known as a neurotransmitter. These are  stored in synaptic vesicles.   1. Some vesicles fuse with plasma membrane of the presynaptic cleft, releasing their  neurotransmitter into the cleft.   This secretion involves a calcium channel.   When a neuron is about to pass on the signal, it is stimulated and that part of the axon is  depolarized. This depolarization opens up Calcium channels, which are concentrated in the  presynaptic nerve terminal.   Calcium is much more concentrated outside of the cell so when the channels open, the calcium  rushes into the nerve terminal.   ● The increase in calcium concentration triggers the fusion between the vesicles and the  membrane.   ● Ach is let out into the cleft, and binds to receptors on the postsynaptic cleft that allow for  sodium channels to open, eventually causing an action potential.   ● Calcium ions are removed from knob and ach is no longer let out of the knob.   ● Choline is taken back up into the presynaptic knob.     Excitatory or inhibitory Neurotransmitters   Excitatory­ acetylcholine and glutamate   ● These allow for an influx of sodium which depolarizes the PM and activate the  postsynaptic cell   Inhibitory­ GABA and glycine   ● These allow for chlorine to get inside of the cell which makes it more polarized and the  action potentials cannot start        


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