Principals of Biology II, Biol 102 (Vogt)
Exam Number Three
November 23, 1999
Name_____________________________________________
ID#_______________________________________________
Instructions:
Write your name and ID# on this page.
Questions are matching, or require short answers.
Be specific. Be brief. Write clearly (if I can not read it, it must be wrong).
Record your answers on the test.
DO NOT EXCEED THE SPACE PROVIDED.
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
IF YOU FINISH EARLY, GO OVER YOUR ANSWERS AGAIN!!!
If your mind goes blank, go ahead to the next question and the next question until you can answer questions again. Go back to unanswered questions when your mind starts working again.
HOW TO DETERMINE / LEARN YOUR SCORE.
- Graded exams will be returned.
- Correct answers will be posted on the course web site, November 30 December 5 (Final is 12/8).
- Scores will be posted on the class Web Page (a link from the syllabus), identified by your ID number; UNLESS YOU NOTIFY ME THAT THIS IS NOT ACCEPTABLE.
-I will display a graph that will allow you to determine your approximate grade (letter). Note: final course grade will be based on total numerical score of all exams.
1. Provide 3 DIFFERENT examples of chemical communication in organisms.(3 points)
1. ANS: odor molecules / olfaction / pheromones (many other possibilities)
2. ANS: neurotransmitters
3. ANS: hormones
2. Provide a definition of "hormone". (2 points)
ANS: Regulatory chemical, released by one cell, into the blood stream, to act on a target cell, causing a response in the target cell
3. What is the relationship between the endocrine system and the circulatory system? (2 points)
ANS: Hormones are released into the circulatory system
________________________________________________________________________
The figure below depicts the physical anatomy of an endocrine pathway involving a peptide hormone.
4. In the figure above, what molecular mechanism assures that ONLY ONE of the 4 cells shown is a "Target Cell". (2 points).
ANS: Only the target cell expresses a receptor for the hormone.
5. FACTOID: Peptide Hormones (such as FSH) CAN NOT pass through membranes while Steroid Hormones (such as Testosterone) CAN.
TASK 1: Compare the mechanism of RELEASE of a PEPTIDE HORMONE vs. a STEROID HORMONE (2 points) :
ANS: Peptide is stored in vescicle, release involves fusion of vesicle to membrane, releasing peptide hormone out of cell. Steroid is synthesized to a membrane soluble form, and diffuses out of the cell.
TASK 2: Compare the ACTION ON A TARGET CELL of a PEPTIDE HORMONE vs. a STEROID HORMONE (2 points):
ANS: Peptide acts on cell surface receptor, activating second messenger response inside cell. Steroid enters cell, binds to cytosolic receptor, complex moves to nucleus where it binds to DNA to influcence gene expression.
6. Define or explain the word "Homeostasis" (2 points).
ANS: The regulation of a of a physiological state around some set point. Maintaining the internal equilibrium of the body.
7. What is the function of "negative feedback" in the endocrine system (3 points).
ANS: Negative feedback keeps things in ballance, keeps things from "running away". Maintaines homeostasis.
8. Give an example of "positive feedback" at work in the endocrine system (2 points).
ANS: Estrogen stimulates GnRH/LH-FSH and LH-FSH stimulates estrogen synthesis/release leading to ovulation
9. The schematic below is missing the NEGATIVE FEEDBACK step.
TASK: Add the arrow that establishes negative feedback in this system. (2 points)
10. Regarding the above drawing...
1. Where in the testis are Interstitial Cells located (1 point)?
ANS: Between seminiferous tubules.
2. What do Interstitial Cells Produce (2 points)?
ANS: Testosterone (as indicated in above figure)
11. Regarding the above drawing (3 points),
1. What TYPE OF CELL produces/releases GnRH?
ANS: Neuroendocrine cell
2. What is the NAME of the TISSUE that contains GnRH releasing cells?
ANS: Hypothalamus
3. What is the NAME of the TISSUE that contains LH and FSH releasing cells?
ANS: Pituitary
12. FACTOID 1: The Ovarian Cycle initiates when FSH activates a primary oocyte to enter the cycle.
FACTOID 2: Certain Birth Control Pills contain a mixture of Estrogen and Progesterone.
QUESTION: Consider the above schematic; why would ingesting a mixture of Estrogen/Progesterone PREVENT Pregnancy? (4 points)
ANS: P/E inhibits release of GnRH
no GnRH, no FSH
with no FSH, no activation of primary oocytes (as stated above) and there will be no oocyte to be fertilized, thus no possibility of a pregnancy.
13. Referring to the above schematic...
What is the function of positive feedback in the ovarian cycle? (3 points)
ANS: LH/FSH stimulates estrogen release which stimulates more LH/FSH leading to hormone surge which leads to / stimulates ovulation (follicle swells and bursts, releasing oocyte
14. Describe the process of sperm formation in the male reproductive system. (4 points).
ANS: Spermatagonia undergo meiosis froming four spermatocytes which differentiate into mature sperm. This occurs in the seminiferous tubules
15. Describe the timing of MEIOTIC events in female (human) oogenesis (3 points).
ANS: Oogonia produced during embryogenesis enter meiosis, arresting in the early phase of the first meiotic division as primary oocytes. On a monthly cycle, one oocyte is activated (stimulated by FSH) and completes the first meiotic division to a secondary oocyte and a polar body (essentially a discarded nucleus). The secondary oocyte is released during ovulation. If fertilization occurs, the secondary oocyte nucleus undergoes the second meiotic division, discarding one of its chromosome sets as a second polar body.
16. FERTILIZATION: Describe the process that prevents multiple sperm from fertilizing the same egg? (3 points).
ANS: Sperm activation of egg causes release of corticle granules. In sea urchins, this "lifts" the fertilization membrane blocking sperm access to the egg membrane. In mammals, this hardens the fertilization membrane, blocking sperm from penetrating the fertilization membrane. Either way, additional sperm are blocked from contacting the egg membrane. Calcium serves as an intermediate between sperm binding and corticle granule activation.
17. FACTOID: Sexual reproduction requires either the coordination of male and female reproductive systems (males having mature sperm when females have fertilizable eggs), and in some cases males and females making physical contact (internal fertilization potentially dangerous because animals more often make physical contact to eat each other).
QUESTION (3 points): Considering it is possible for organisms to reproduce asexually,
WHAT IS THE BIOLOGICAL ROLE or VALUE OF SEXUAL REPRODUCTION?
ANS: Sexual reproduction follows meiosis and permits new combinations of genes to come toghether in the organism. Increased genetic diversity establishes a genetically diverse population which has some members presumably / potentially more fit to certain enviornmental conditions.
Q18-20 refer to the above figure...
18. What do the "N" and "2N" refer to? (2 points):
ANS: These are symbols that represent the number of chromosome copies.
19. Which letter(s) does the term "zygote" apply to? (2 points): ANS: C
20. Which letter(s) does the term "embryo" apply to? (2 points): ANS: C and D
The above illustration depicts early development in the Sea Urchin (Echinoderm deuterostome) and Human ( Chordate deuterostome).
21. For the Sea Urchin, identify (LABEL) the BLASTULA. (2 points)
ANS: The ball of cells. embryos 6, 7 or 8 would be acceptable.
22. What process does "GASTRULATION" refer to? (3 points)
ANS: invagination, formation of three germ layers
23. For EITHER sea urchin OR human, identify (LABEL above):
1. Cells giving rise to Ectoderm (2 points): ANS: Outer "shell" of embryo in final urchin embryo, epiblast in lower human figure.
2. Cells giving rise to Mesoderm (2 points): ANS: Loose cells inside urchin embryos 9-12. Loose cells between hypoplast and epiblast in lower human embryo.
24. During development, anatomical complexity is formed one-step-at-a-time. One of the first steps is to establish the three germ layers, ectoderm, mesoderm and endoderm.
QUESTION: Identify 2 tissues that derive from each germ layer (6 points, 1 point each)
Ectoderm: _____epidermis_______ & ____nervous system____
Mesoderm: _____muscle_________ & ____skeleton _________
Endoderm: _____liver___________ & ____intestine (epithelium)___
25. In the above figure, identify (LABEL) (4 points)
ANS: LOOK THIS UP IF YOU DONT KNOW
1. Dendrite
2. Cell Body (Soma)
3. Axon
4. Synapse
26. One neuron communicates to another neuron or to a muscle
via a ______synapse______________________________. (supply word(s), 2 points)
27. Within a neuron, a dendritic synapse communicates to an axonal synapse
via ________ionic current , electric current_____________. (supply word(s), 2 points)
You measure the voltage across the membrane of a nerve cell, and display it vs. time.
28. Define / Explain "Resting Potential" AND indicate (LABEL) the Resting Potential on the above plot (3 points).
ANS: The Trans-membrane voltage when the cell is at rest. Position #1.
29. An electric shock is applied to the nerve cell at the time indicated by the arrow (above drawing), and a rapid change in the membrane voltage is observed. This change in membrane voltage is called the ACTION POTENTIAL.
1. The Action Potential ONLY OCCURS in which part of the nerve cell? (2 points)
ANS: AXON
2. What process is responsible for the "rising phase" of the Action Potential (region #2 or #3 in plot above)? (2 points)
ANS: Inward movement of Na+ ions via voltage sensitive Na+ channels in axon.
30. What is the difference between an INTER-NEURON and a NEUROENDOCRINE (neurosecretory) CELL? (2 points)
ANS: interneuron release neurotransmitter onto post-synaptic neuron (has a synaptic ending)
neuroendocrine cell releases hormone into blood (no synapse at end of axon).
31. Explain the significance of the above drawing in the context of either hormone action or neurotransmitter action. (3 points)
ANS: Receptor and G-protein complex that is activated by either a hormone or a neurotrasmitter, leading to activation of a second messenger.
====================================================================
32. The figure above depicts a chemical synapse between two neurons.
TASK: Describe the events that will occur when the action potential (shown) arrives at the axonal ending (be as thorough as possible) (5 points).
ANS: short answer action potential arrives at ending, causes release of neurotransmitter which binds to and activates receptors in next cell. (partial credit awarded)
ANS: complete answer action potential arrives and ending, causing Calcium entry which activates the release of neuro transmitter which activates receptors in post-synaptic neuron which leads to the creation of ionic currents in post-synaptic dendrites.
ANS: could have drawn arrows in and numbered them in order of occurance
33. FACTOID: We catagorize neurons as SENSORY NEURONS, INTER NEURONS and MOTOR NEURONS. (3 points)
TASK 1. Identify (compare) the input signals of SENSORY NEURONS vs. MOTOR NEURONS. ANS: SN: enviornmental signal;MN: neurotransmitter
TASK 2. Identify (compare) the target cell types of SENSORY NEURONS vs. MOTOR NEURONS. ANS: SN: a neuron; MN: muscle cell
34. Muscle cells are called fibers. In skeletal muscle, these fibers are comprised of bundles of myofibrils which consist of contractile proteins. (3 points).
1. What are the names of the 2 main contractile proteins in muscle?
ANS: actin, myosin
2. Indicate (LABEL) these two proteins in the drawing above.
ANS: myosin = thick filaments, horizontal, between Z-lines
actin = thin filaments, horizontal between Z-lines
35. What is the rewarding quesiton? (an extracredit bonus for those who come to class).
Extra Credit (10 points each) (You may answer up to 3, and receive up to 30 additional points).
1. When your body temperature is lowered, thyroid hormone is released to stimulate metabolic activity. (1) Draw the hormone pathway that stimulates and regulates the release of thyroid hormone. (2) Identify where the environmental signal INPUT located.
ANS: TSHRH (hypothalamus) > TSH (pituitary) >TH (thyroid gland) >>> body, increase metabolic activity and back to hypothalamus to down regulate TSHRH release. Temperature information is input into TSHRH releasing neuroendocrine cells. Negative feedback is TH (and TSH) inhibiting release of TSHRH in the hypothalamus, as well as temperature adjusting to set point.
2. Neurons (all cells) maintain a voltage difference across their membrane, called the RESTING POTENTIAL. (1) What are the ionic and electrical distributions across the cell membrane and (2) how are they established?
ANS: Inside: high K+, low Na+, low Cl-, negative
Outside: low K+, high Na+, high Cl-, positive
negatively charged proteins inside cell drive out Cl- by electrostatic repulsion
Na+/K+ ATPase (pump) in cell membrane pumps out Na+ and pumps in K+, creating unequal concentrations.
3. During development, one of the first recognizable "tissues" is the precursor nervous system (neural tube) which forms just after gastrulation. Describe (with drawings if desired) the processes of neural tube formation.
ANS: notochord forms in mesoderm along midline of "body". Induces overlying ectoderm to fold up, forming neural tube which separates from ectoderm, dropping inward. Nervous system is thus derived from ectoderm.
4. Calcium (Ca++) is an important regulator of many cellular events, including muscle contraction. (1) Describe the mechanism by which Ca++ regulates muscle contraction, and (2) how Ca++ itself is regulated in the muscle.
ANS: Action potential arrives at nerve muscle synapse, released neurotransmitter activates receptors in muscle initiating action potential in muscle membrane. Muscle action potential stimulates the release of Ca++ from sarcoplasmic reticulum. Released Ca++ binds to troponin, causing tropomysin to be pulled away from myosin binding sites on actin, and thus permitting myosin-actin interactions (and contraction). Stop action potential, stop releasing Ca++, Ca++ ATPase pumps Ca++ back into sarcoplasmic reticulum, Ca++ leaves troponin, tropomysin blocks actin, preventing myosin interactions, muscle relaxes.
5. Sensory neurons convert environmental signals into neuronal activity (ionic currents). How is this accomplished in visual cells? How does "photo-transduction" work?
ANS: light converts retinal bound to rhodopsin from cis form to trans form, activating the receptor (rhodopsin) which activates a G-protein which activates a phosphodiesterase enzyme which degrades cGMP which was stimulating Na+ channels in the membrane of the photoreceptor cell, but degadation of cGMP now causes to stop.
7. What is a second messenger? Draw and describe the second messenger pathway that includes cAMP. What are some actions of cAMP?
ANS:
Second messengers are intracellular signals (chemicals) that continue the transfer of information conveyed by the hormone or neurotransmitter (or other external signal) to the inside of the cell, eliciting a response.
Activated alpha subunit of G-protein activates membrane bound adenylate cyclase to convert ATP to cAMP (second messenger).
cAMP binds to various protein targets inside cell, altering their activities. Common action is the activation of a protein kinase which transfers a phosphate from ATP to a protein, altering the property of that protein.