1. Tues 10/15
Cell Communication Quiz is THURSDAY!

2. ATP: An Important Source of Energy for Cellular Processes
***REVIEW***
ATP: An Important Source of Energy for Cellular Processes
One phosphate molecule, adenosine triphosphate (ATP), is the primary energy-transferring molecule in the cell
ATP consists of an organic molecule called adenosine attached to a string of three phosphate groups
They most likely know this molecule’s general structure from their Biology I course. Emphasize yet again that breaking a bond requires energy (as in removing one of those phosphates) while bond formation releases energy.

3. The most common secondary messengers include: a. cyclic AMP
Between the receptor molecule that is activated and signal-transduction pathway that is to be activated, there may be a second messenger.
(Note-The hormone or signal that attaches the to the receptor site is called the first messenger.)
The most common secondary messengers include:
a. cyclic AMP
b. Calcium ions and inositol triphosphate.

7. cAMP: (second messenger)
Example: When epinephrine binds to its receptor site, there is a corresponding increase in the amount of cAMP found in the cell.
cAMP is a derivative of ATP. An enzyme (adenylyl cyclase) in the plasma membrane causes this reaction to occur.
In this example, epinephrine activates a receptor site, that in turns activates the G-protein. The G protein now activates adenylyl cyclase which then makes cAMP from ATP.
cAMP activates the epinephrine pathway which ultimately increases the amount of glucose in the blood stream.

8. Consider this pathway: epinephrine G-protein-linked receptor G protein adenylyl cyclase cAMP. Identify the second messenger.
A) cAMP
B) G protein
C) GTP
D) adenylyl cyclase
E) G-protein-linked receptor .

9. A
The second messenger is cAMP. The first messenger is epinephrine.

10. Calcium ions and Inositol Triphosphate (IP3):
Some signal molecules in animals induce responses by increasing amount of Ca++ in the cytosol.
Used in muscles, nerves, & certain hormones.
Most of the time Ca++ in the cytosol is low because it is pumped into the E.R., mitochondria, & out of the cell.
The release of Ca++ from E.R. reservoirs involves diacylglycerol (D.A.G.) and inositol triphosphate (IP3).
D.A.G and IP3 are made by the cleavage of certain kind phospholipid in the plasma membrane.
This is done when the G protein activates enzyme phospholipase C.
Phospholipase C cleaves a plasma membrane in two to make D.A.G. and IP3.
IP3 will then move to the E.R. and bind with a IP3-gated calcium channel to allow Ca++ to flow out.

11. Ca++ will now combine with a protein called calmodulin.
Once activated calmodulin will activate the biochemical pathway it is intended to activate.
Usually by activating a kinase or phosphatase.

14. Protein phosphorylation is commonly involved with all of the following except
A) regulation of transcription by extracellular signal molecules.
B) enzyme activation.
C) activation of G-protein-linked receptors.
D) activation of receptor tyrosine kinases.
E) activation of protein kinase molecules.

15. C
The activation of the G-protein linked receptor are some sort of signal like a hormone, neurotransmitter, or ligand. It does not involve protein phosphorylation.

16. Types of cellular responses:
1. Ultimately activating an enzyme
2. Synthesis of a particular enzyme or protein

17. 1. Activating an enzyme:
Usually when cAMP, Ca++ or IP3 is activated it will interact with a specific enzyme to start the cascading effect.

18. Different kinds of cells have different collections of proteins
These different proteins allow cells to detect and respond to different signals
Even the same signal can have different effects in cells with different proteins and pathways
Pathway branching and “cross-talk” further help the cell coordinate incoming signals
Blockage of a signal transduction pathway or a defective pathway can be deleterious, preventative, or prophylactic. 18

20. Signal transduction pathways benefit cells for all of the following reasons except
A) they help cells respond to signal molecules that are too large or too polar to cross the plasma membrane.
B) they enable different cells to respond appropriately to the same signal.
C) they help cells use up phosphate generated by ATP breakdown.
D) they can amplify a signal.
E) variations in the signal transduction pathways can enhance response specificity.

21. C
Signal transduction pathways benefit cells for all of the following reasons except cannot help cells use up phosphate generated by ATP breakdown.

22. Apoptosis
Cells that are infected, damaged, or have reached the end of their functional life span often undergo “programmed cell death” = Apoptosis
“cell suicide”
Cellular agents chop up DNA and organelles, cell shrinks & becomes lobed, cell parts are packaged in vesicles then engulfed & digested.
Protects neighbor cells
from damage

23. Apoptosis Control
Triggered by signals that activate a cascade of “suicide” proteins in cell destined to die.
Most of these proteins are in all cells but in inactive form, regulation occurs at level of protein activity.
Signal can originate from outside or inside the cell (nucleus=DNA damaged, ER=protein misfolding)
Essential to development & maintenance
Involved in degenerative diseases (Parkinson’s, Alzheimer’s, Cancer) & webbed fingers and toes.

24. To sum it all up…. Epinephrine Example

25. Why are these pathways so important for researchers and doctors to understand???

26. Body cells take up more glucose.
Figure 45.13
Insulin
Body cells take up more glucose.
Beta cells of pancreas release insulin into the blood.
Liver takes up glucose and stores it as glycogen.
STIMULUS: Blood glucose level rises (for instance, after eating a carbohydrate-rich meal).
Blood glucose level declines.
Homeostasis: Blood glucose level (70–110 mg/100mL)
STIMULUS: Blood glucose level falls (for instance, after skipping a meal).
Blood glucose level rises.
Describe the actions that occur when blood glucose levels decline and when they rise. Glucagon and insulin are paired hormones that work together to maintain blood glucose levels between 70 and 110 mg/100mL
Liver breaks down glycogen and releases glucose into the blood.
Alpha cells of pancreas release glucagon into the blood.
Glucagon

27. Out of Balance: Diabetes Mellitus
Diabetes mellitus is perhaps the best-known endocrine disorder.
It is caused by a deficiency of insulin or a decreased response to insulin in target tissues.
It is marked by elevated blood glucose levels.
Ask students to explain how a lack of insulin leads to elevated levels of glucose in the blood. Then ask them to suggest reasons this increased level of glucose is harmful to the person with diabetes.

28. Out of Balance: Diabetes Mellitus
Type 1 diabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells.
Type 2 diabetes mellitus (non-insulin-dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors.
Type 1 has in the past been referred to as Juvenile Diabetes. Just as a point of interest, the incidence varies from 8 to 17 per 100,000 in Northern Europe and the U.S. with a high of about 35 per 100,000 in Scandinavia to a low of 1 per 100,000 in Japan and China.

29. Action of Insulin
When insulin receptors respond properly to the presence of insulin, the result is the transport of glucose from outside the cell to inside the cell via transport protein. People with Type I diabetes do not produce sufficient insulin to maintain a proper level of glucose transport. The disorder is typically treated by providing the patient with insulin.

30. Ever heard of “a runner’s high”?
Our body manufactures endorphins which are made by the pituitary gland and bind to the receptors in the brain that relieve pain and produce euphoria during times of stress, such as intense exercise.
Opiates such as morphine and heroin are structured similarly, thus can bind with the receptors . These “bindings” are actually those electrostatic attractions we call IMFs.
This is a good time to point out that students need illustrative examples for each and every major unit of study. Help them choose these illustrative examples!

31. The boxed regions are shaped similarly!
Carbon
Nitrogen
Hydrogen
Sulfur
Natural endorphin
Oxygen
Morphine
Have students compare the boxed portion of each diagram. What’s alike? What’s different?
(a) Structures of endorphin and morphine

32. (b) Binding to endorphin receptors
Pain killer!
The brain receptors “bind” with either with similar results.
Natural
endorphin
Morphine
“Bind” is in quotes because…you guessed it…it’s not a chemical bond that is “binding” these molecules to the receptor but an IMF that attracts them. Those electrostatic attractions can indeed induce shape changes which can impact molecular function.
Endorphin
receptors
Brain cell
(b) Binding to endorphin receptors