lesson 5: cell signaling with hormones (26.1 - 2; 26.8 - 9; 5.13 - 5.16)

What two types of signals does the body use to communicate?

Chemical Signals (Hormones from the Endocrine System) and Electrical Signals (Neurons from the Nervous System).

What is homeostasis?

Regulation of the internal body environment.

What system does the Endocrine System coordinate with in communication?

Nervous System.

How do hormones and neurons affect different responses in the body?

Hormones - Travel through the bloodstream; long-term processes (growth, metabolism, reproduction). (longer response time needed)

Neurons - Extremely quick response (immediate) to external stimuli.

What differentiates a target cell from a non-target cell?

A receptor that recognizes the specific signal.

What are neurosecretory cells?

Neurons that release chemicals (hormones) into the bloodstream.

What are the three stages of hormone signaling?

1. Reception - Signal/Hormone binds to Target Cell.

2. Signal Transduction - Convert signal from one form to another.

3. Response - Change in a cell's behavior.

Where are hormone receptors located on the cell?

There are both water-soluble hormones (bind to plasma membrane) and lipid-soluble hormones (which pass through the plasma membrane).

How does a water-soluble hormone work?

-Signal binds to receptor on plasma membrane, after traveling through bloodstream.
-Excites relay molecule activation.
-Can induce cellular response or creation of protein (gene regulation in the nucleus).

-They are hydrophilic (proteins); and mostly produced by endocrine glands.

How does a lipid-soluble hormone work?

-Hydrophobic, so it will pass through the plasma membrane, and then bind to a receptor.
-Signaling molecule will then pass to hormone receptor complex.
-DNA - Transcription - Translation
-Cellular Response: Activation of a Gene & a New Protein

-EX: Steroid

Why can steroid hormones pass through the plasma and nuclear membranes?

The phospholipid bilayer is permeable to lipid-soluble molecules (hydrophobic), as the interior of the plasma membrane, is hydrophobic, as well.

What organ secrets insulin and glucagon?

Pancreas

How are insulin and glucagon a negative feedback loop?

Lower and Raise Glucose to 'normal' levels, and then secretion of hormones yields.

What are the target cells of Insulin and what does it do?

Used majorly by liver and muscle cells (uptake & storage); lowers blood glucose level to normal.

What are the target cells of Glucagon?

Liver cells release stored glucose; increases blood glucose level to normal.

What is Diabetes?

Disease where body is unable to produce/ use enough insulin.

What is the difference in signaling defects between Type I and Type II Diabetes?

Type I Diabetes - Insulin is Absent.
Type II Diabetes - Insulin Signaling is Defective.

What condition occurs if too much insulin is produced or injected?

Hypoglycemia (low blood sugar)

What is activation energy and what does it do?

It serves as an energy barrier that must be overcome in order for a reaction to occur. This is the amount of energy reactants must absorb before a chemical reaction will start.

What do enzymes do?

Lower the activation energy needed to start the reaction.

They are biological catalysts that increase the rate of a reaction WITHOUT being consumed.

What is another word for a reactant?

A substrate; a specific reactant on which an enzyme acts.

Are enzymes always proteins?

No.

Where does a substrate bind to an enzyme?

Active Site (induced fit).

What conditions do most enzymes work best at?

-Optimal pH (usually b/w 6-8)
-Temperature can vary; but excessive heat/too acidic/basic pH can denature (unfold) the protein, changing it's function.

What are co-factors?

A non-protein substance, such as (minerals) zinc, iron, and vitamins, that helps enzymes convert substrate to product.

What is induced fit?

A change in shape of an enzyme's active site induced by a substrate.

What does a noncompetitive inhibitor do?

Binds to a site other than the active site; alters the enzyme's function by changing it's shape.

What does a competitive inhibitor do?

competes directly with the substrate for the active site; reduces the rate of reaction

What is feedback inhibition?

The process in which a stimulus produces a response that opposes the original stimulus.

What may be the issue if a cell is not relaying a signal?

-Too little of the signal molecule.
-Issues with the receptor.
-Molecule is structurally defective.
-If lipid soluble, cannot enter the nucleus.

What do androgens stimulate?

The growth of facial hair in humans.

How do glucagon and insulin differ?

Insulin causes some cells to take up glucose, whereas glucagon causes some cells to secrete glucose.

Which of the following hypothetical situations might result in a blood sugar level that is too high?

-An individual has an autoimmune disorder that destroys the beta cells of the pancreas.
-An individual's insulin receptors are defective.

A target cell that is affected by a particular steroid hormone would be expected to have...

an intracellular receptor protein that binds the hormone.

What does the hormone receptor complex do?

Serve as a gene activator.

A mutation in the gene for hormone A causes it to be unable to bind to its receptor protein. What do you predict will likely happen?

The receptor protein will not be activated and therefore will not initiate a signal transduction pathway.

In their mechanism of action, a difference between lipid-soluble and water-soluble hormones is that _____.

lipid-soluble hormones may enter the nucleus of the target cell, whereas water-soluble hormones do not.

Controlled studies conducted by scientists at University of California-Berkeley and described in module 26.3 of your text have shown that __________.

atrazine-exposed male frogs have decreased fertility over the control group.

Atrazine and BPA are called endocrine disruptors because they mimic the action of __________.

estrogen

A single hormone can...

affect two cells differently.

What would you predict to be different at the cellular level between estrogen-dependent and estrogen-independent cancer?

Estrogen-dependent cells have receptors, whereas estrogen-independent cells do not (do not require estrogen signal to grow).

Explain how the body maintains normal blood glucose level during a period of fasting.

Glycogen is produced as a result of low blood sugar during a period of fasting, which then signals cells to release stored glucose (break down glycogen stores) (liver, muscle cells), and increase the blood glucose levels to normal.

Stimulus - Low Blood Sugar

Explain how the body maintains normal blood glucose level after a sugary snack.

Insulin is released by beta cells of the pancreas, which signals cells to bring in glucose from the blood, to drop blood sugar back to normal ('glucose set point').

Stimulus - High Blood Sugar

What is an apoenzyme?

An enzyme that is lacking (not bound to) its cofactor.

What is a holoenzyme?

apoenzyme + cofactor (active enzyme)

To know if an inhibitor is competitive or non-competitive, you need to know what?

Where it binds on the enzyme.