Term
| Describe Diffusion Of Large Or Polar Molecules |
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Definition
| They cannot DIFFUSE across the membrane...includes amino acids, glucose, and other organic molecules. Need carrier proteins. |
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Term
| Carrier Proteins (3-main points) |
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Definition
Move large or polar molecules across the membrane.
--They are specific
--There may be competition for similar carriers or molecules
--They demonstrate saturation...have a max number of carriers |
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Term
| Competition Effect...Re: Transport Proteins |
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Definition
| Some proteins can transport more than one molecule, which will create a "competition effect" |
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Term
| Transport Maximum (Re: Transport Proteins) |
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Definition
| All carriers are in use: Transport rates increase with increased molecule concentration until saturation is met |
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Term
| Describe Facilitated Diffusion Of Glucose |
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Definition
| when [glucose] outside the cell is high and the [glucose] inside the cell is low...glucose can diffuse from outside the cell to inside the cell...but cannot simply diffuse through the membrane...needs transport proteins to do so |
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Term
| Name & Describe The 4 Glucose Transporters We Discussed |
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Definition
GLUT1--CNS
GLUT2--pancreatic beta cells and hepatocytes
GLUT3--Neurons
GLUT4--skeletal muscle & adipose tissue; can be inserted into the PM of skeletal muscle when stimulated |
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Term
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Definition
| When molecules are moved from a [LOW] to a [HIGH]...the opposite of diffusion. This requires energy. Often, these carrier-mediated proteins are called pumps. |
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Term
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Definition
| When the hydrolysis of ATP is directly responsible for the carrier protein function. The transport protein is also an ATPase enzyme that will hydrolyze ATP |
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Term
Secondary Active Transport
--[Hint: Na+] |
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Definition
| When the energy needed to transport molecules across their concentration gradient is derived from the energy stored in the SODIUM gradient |
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Term
Re: Secondary Active Transport
---What is Cotransport or Symport? |
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Definition
| Cotransport/Symport is when the other molecule is transported with Na+...this is the common way to transport glucose when [glucose] is higher inside the cell |
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Term
Re: Secondary Active Transport
--What is Countertransport/Antiport? |
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Definition
Countertransport/Antiport is when the other molecule is moved in the opposite direction of NA+
e.g. The Na-Ca exchanger...the uphill extrusion of Ca from a cell |
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Term
| Describe the Ca2+/ATPase Pump |
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Definition
--located on all cells and in the ER of striated muscle cells
--removes Ca2+ from the cytoplasm and moves it into the extracellular fluid or cisternae of the ER |
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Term
| Describe the [Ca2+] inside the cell vs. the [Ca2+] outside the cell |
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Definition
--Normal [Ca2+] in the cytoplasm is ~120nM
--Normal free [Ca2+] in the blood and extracellular fluid is 1.2mM |
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Term
| Describe the effects of an increase of intracellular [Ca2+] |
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Definition
| Triggers muscle contraction and neurotransmitter release (exocytosis) |
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Term
| Sodium Pump (Na+/K+ ATPase) |
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Definition
1) Found in all body cells
2) Most numerous transporter in cell membranes and the consumer of the majority of cellular ATP
3) ATPase enzyme pumps 3Na+ out of the cell and 2K+ into the cell
4) Serves three functions:
--provides energy for coupled transport of other molecules
--maintains osmolality
--permits the establishment and maintenance of a
trans-membrane electrical potential (voltage) |
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Term
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Definition
1) 3Na+ move from the cytoplasm and into the pump and bind
2) ATPase is activated to hydrolyze ATP to ADP & Pi
3) ADP is released, causing a shape change that allows 3Na+ to exit the pump and travel outside the cell
4) 2K+ enter the carrier from the outside, releasing Pi
5) Pump returns to original shape and releases 2K+ to the inside of the cell |
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Term
| Transport Across Epithelial Membranes--Absorption |
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Definition
| transport of digestive products across intestinal epithelium into the blood |
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Term
| Transport Across Epithelial Membranes--Reabsorption |
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Definition
| transport of molecules out of the urinary filtrate back into the blood |
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Term
| Transport Across Epithelial Membranes--Excretion |
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Definition
| transport of molecules to the outside of the body |
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Term
| Transport Across Epithelial Membranes--Trans-cellular Transport |
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Definition
| movement of molecules through the cytoplasm of the epithelial cells; typically one membrane carries out active transport--the other passive transport |
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Term
| Transport BETWEEN Cells Is Usually Blocked By What? |
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Definition
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Term
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Definition
Large molecules such as proteins, hormones, and neurotransmitters are secreted via exocytosis
--involves fusion of a vesicle with the plasma membrane
--requires ATP
Other molecules are taken into cells by endocytosis
--also requires ATP |
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Term
| Neurons in terms of Membrane Potentials |
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Definition
1) In neurons, the resting membrane potential is -70mV...which is close to EK.
2) Neurons can change their permeability to different ions, causing ions to move and change the membrane potential |
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Term
| Cell Signaling--Synaptic Signaling |
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Definition
| involves neurons secreting neurotransmitters across a synapse to target cells (post-synaptic neurons) |
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Term
| Cell Signaling--Autocrine Signaling |
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Definition
| some cells secrete molecules that act back onto the receptors of the same cells |
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Term
| Cell Signaling--Paracrine Signaling |
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Definition
| release of a chemical that affects nearby cells |
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Term
| Cell Signaling--Endocrine Signaling |
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Definition
| involves secretion of hormones into the extracellular space that are picked up by the bloodstream; these can reach multiple distant target cells |
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Term
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Definition
| STN: steroid hormones, thyroid hormone, and nitric oxide |
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Term
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Definition
EAI: epinephrine, acetlycholine, and insulin
-require the use of a second messenger |
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Term
| Second Messenger--what is it? |
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Definition
--A second messenger is involved with polar signal molecules
--once the polar molecule binds to the receptors on the PM, the second messenger is stimulated to activate and carryout a task that is determined by the type of signal molecule |
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Term
Second Messenger--cAMP
What is It and What Are The Activating Steps? |
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Definition
-Cyclic adenosine monophosphate
-Steps
1) A signaling molecule binds to a receptor on the PM
2) This activates adenyl cyclase, an enzyme that produces cAMP from ATP
3) cAMP activates other enzymes
4) Cell activities change accordingly |
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