Supplemental Instruction BIOL 212

4/7/2021 Module 3 Exam Review (Ch. 46, 11, 47, 21) *I encourage you to work through this worksheet in addition to reviewing your own notes, lecture videos, homework problems, and other SI worksheets to prepare for Exam 3. Chapter 46: Chemical Signals Learning Objectives

¨ Distinguish between the 5 types of signaling mechanisms.

¨ Evaluate the physical and chemical properties of different classes of hormones that affect

the location of their receptors on the target cell.

¨ Compare and contrast the different signaling pathways.

¨ Describe the 4 steps in cell-cell signaling that occur when the hormone reaches its target

cell.

1. Which of the following is an example of endocrine signaling?

a. Interleukin-1 is produced during the inflammatory response and proceeds to bind to receptors found on the cell that produced it. Autocrine (act on same cells that secrete)

b. Oxytocin is produced in the posterior pituitary and acts on the cells of the mammary glands during milk production.

c. Dopamine is released from nerve cells and diffuses across the synapse to another neuron. Neural signal (neurotransmitters diffuse between neurons)

d. Steroids, such as testosterone, are secreted by the testes and stimulate spermatogenesis. Paracrine (diffuse locally to act on nearby cells)

2. When hormones circulate throughout the ___bloodstream___, they affect only certain “target” cells and tissues. The presence of an appropriate __receptor___ dictates which cells will be able to respond to the hormone.

3. How do steroid hormones differ from polypeptide hormones and most amino acid derived hormones?

a. Steroid hormones are lipid soluble and cross plasma membranes readily. i. Polypeptide hormones and most amino-acid derived hormones are not

lipid soluble and can’t enter cells. b. Polypeptide and amino-acid-derived hormones are longer lived in the bloodstream

and thus exert greater signal amplification. c. Polypeptide hormones are the most structurally complex and induce permanent

changes in target cells. d. Only steroid hormones bind to receptors in the plasma membrane.

4. Predict what would happen to the hormone response if an individual had mutations that changed the DNA sequence of its hormone-response element.

a. The hormone-receptor complex would fail to bind to the hormone-response element. This means that we will most likely not observe an effect on the target cell – because gene expression will not change.

Chapter 11: Cell-Cell Interactions Learning Objectives

¨ Differentiate between the mechanism of action of lipid-soluble and lipid-insoluble

hormone signals.

¨ Illustrate the steps in cell-cell signaling.

¨ Identify the functions of different types of signals.

¨ Identify the mechanisms that different types of signal receptors use to transduce an

incoming signal to the interior of the cell.

¨ Recognize the importance of crosstalk between signal transduction pathways.

¨ Predict the impact that a mutated or dysfunctional protein would have on the pathway

that it is part of.

¨ Connect the 4 steps in cell signaling to each of the examples provided. For example, what

part of the apoptosis pathway can be considered signal processing.

¨ Identify the types of receptors (cell surface and intracellular) that a cell uses to receive

signals from the environment.

¨ Describe the role of cAMP in signal transduction.

¨ Illustrate key events in the signaling pathway for EGF, epinephrine, and estrogen. How is

the signal received and transmitted? What is the final response for each pathway?

¨ Compare and contrast the different pathways.

1. What type of cell-cell junction acts as a cell communication portal in plant cells?

a. Plasmodesmata

b. Tight junctions – adjacent animal cells c. Desmosomes d. Gap junctions

2. How are G proteins activated?

a. When an intracellular receptor binds the signaling molecule b. When they bind GTP c. When they hydrolyze GTP to GDP d. They are always active

3. Which of these statements is false?

a. The sensitivity of a hormone may change over time. b. The interaction between hormones and receptors can be

blocked by drugs. c. Multiple second messengers can be involved in triggering a

cell’s response. d. Lipid-insoluble hormones form a hormone-receptor

complex to bind to DNA.

4. Explain the five steps (shown in diagram on the right) that occur in response to a hormone binding to receptor-tyrosine kinases (a type of enzyme-linked receptors).

1. A hormone binds to two RTK subunits, causing them to form a dimer.

2. Conformational change in RTK, turning on its catalytic activity. This allows the RTK to phosphorylate itself using ATP in the cell.

3. Proteins in the cell bind to the phosphorylated RTK, forming a bridge between the receptor and Ras (a membrane protein – a G protein). This activates the Ras and it exchanges the bound GDP for a GTP.

4. Activated Ras activates a protein kinase by triggering a phosphorylation.

5. Active kinase starts a phosphorylation cascade. Continues until a response is triggered in the cell.

- First two steps are important to remember, it’s important to know that there’s activation of subsequent relay proteins in a signal transduction pathway (instead of specifics).

a. This sequence of protein modifications is a called a __phosphorylation____ cascade.

Chapter 47: Animal Reproduction Learning Objectives

¨ Compare and contrast gamete formation in males and females.

¨ Compare and contrast reproductive anatomy in males and females.

¨ Identify events at each stage of the female menstrual cycle.

¨ Explain the role that hormones play in the female menstrual cycle.

¨ Arrange events that establish pregnancy in the appropriate order keeping in mind the

action of hormones at each stage.

¨ Explain how the birth control pill works.

1. Compare and contrast spermatogenesis and oogenesis. (Location, # of cells produced,

etc.) a. Sperm are produced in the testes, eggs are produced in ovaries. b. Spermatogenesis produces four mature sperm (from one cell). Oogenesis

produces one large egg (from one cell). c. Both processes produce haploid gametes from diploid cells.

2. What happens in each of the two phases of the menstrual cycle (14 days each)?

Follicular (day 1-14): follicle (sac of supportive cells containing an egg) matures here.

- Days 1-7: period – uterus sheds its lining - Primary oocyte finish meiosis I during this phase. - Ovulation matures and releases secondary oocyte into oviduct. - Endometrium thickening

Luteal (day 15-28): begins with ovulation.

- Corpus luteum (: hormone-secreting structure) forms from ruptured follicle and degenerates if fertilization doesn’t occur.

a. What hormones are involved in each of these phases? Follicular:

1. FSH and LH stimulate ovary 2. Estrogen, FSH, LH cause ovulation 3. Estrogen stimulates endometrial thickening

Luteal:

4. Corpus luteum secretes progesterone 5. Stimulates endometrial thickening 6. Inhibits FSH and LH (no new follicle developing)

3. When a woman becomes pregnant, which step of the menstrual cycle does not occur?

I. Stimulation of follicles to eventually rupture and ovulate an oocyte. II. Corpus luteum lives longer than 10 days and continues to produce progesterone, which maintains the endometrium. III. Fertilized egg develops into an embryo that produces hCG. IV. Follicle cells reorganize to form the corpus luteum. V. Corpus luteum disintegrates after 7-10 days, halting progesterone production.

4. What hormone is detected by pregnancy tests? What is this hormone responsible for?

hCG (embryo is implanted in the uterine lining, its cells begin synthesizing and secreting hCG). This prolongs estrogen and progesterone production by the corpus luteum. Prevents corpus luteum from degenerating before the placenta is developed enough to produce estrogen and progesterone – then it degenerates.

Chapter 21: Genes, Development, and Evolution Learning Objectives

¨ Explain the mechanism underlying differential gene expression.

¨ Identify properties of stem cells. What make them different from somatic cells?

¨ Distinguish between different types of stem cells based on potency.

¨ Describe the role that morphogens play during development. What are these molecules?

How do they contribute to development?

¨ Identify roles of gap, pair rule and segment identity genes. Given a defect in the embryo,

be able to identify which genes are mutated?

1. List the important characteristics of stem cells. a. Self-renewal: The population of stem cells is maintained even when stem cells

divide. One daughter becomes committed to a pathway of differentiation, and the other daughter cell remains a stem cell.

b. Can be induced to become specialized cells. c. Play a big role in cell differentiation

2. Define the different levels of stem cell potency.

a. Totipotent: has the potential to form all adult cell types – complete individual b. Pluripotent: can form almost any cell types c. Multipotent: can form a limited cell types (Ex: Hematopoietic stem cells can

differentiate into different types pf blood cells)

3. Morphogens work in a concentration [dependent / independent] manner. Are they distributed uniformly throughout the embryo?

No.

4. In Drosophila, what morphogen is responsible for determining the anterior-posterior axis?

a. Bicoid – regulatory transcription factor i. Bicoid is required for head formation – turns on genes responsible for

forming anterior structures Morphogens: Molecules known as _____morphogens______ direct the setting up of the major body axes of the embryo

5. Explain the roles of:

(What do they do?) a. Gap genes: Subdivides the embryo into broad regions. b. Pair-rule genes: Divide the embryo up into segments. They are expressed in

alternating band – they correspond to a body segment that is forming along the embryo.

c. Homeotic genes: These gene products define front, middle, and rear subregions within the segments laid down by pair-rule genes.

d. Hox genes: Specify what type of adult structure will develop from each segment in the mature organism.