finalexam

Final Exam

Fall, 2001

Multiple choice questions.
Correct answers marked in bold.

1. In the placenta, how many cell membranes must an O₂ molecule cross in order to pass from a hemoglobin molecule in the mother's blood to a hemoglobin molecule in the blood of the fetus?

A) zero

B) two

C) four

D) six

2. Tendons are composed of

A) loose connective tissue

B) fibrous connective tissue

C) muscle tissue

D) cartilage

3. Myelin is

A) part of a flower that generates megaspores

B) glial cell membrane wrapped around an axon

C) near-sighted vision

D) muscle protein related to hemoglobin

4. Which of the following hormones is the direct cause of ovulation in humans?

A) progesterone

B) follicle-stimulating hormone (FSH)

C) luteinizing hormone (LH)

D) human chorionic gonadotropin (HCG)

5. Which of the following is an example of a tropic hormone?

A) gonadotropin-releasing hormone (GnRH)

B) anti-diuretic hormone (ADH)

C) epinephrine

D) none of the above

6. Which of the following statements is true of the human circulatory system?

A) blood pressure is higher in the pulmonary vein than in the pulmonary artery

B) pulmonary vein carries oxygenated blood

C) atrioventricular (AV) node is the pacemaker of the heart beat

D) a blood cell in the aorta can return to the aorta by passing through the heart only once

7. In mammals, which of the following normally occurs when the diaphram contracts?

A) alveoli collapse to a smaller volume

B) pressure in the lungs becomes more negative

C) air is expired from the lungs into the atmosphere

D) diaphragm rises from the abdomen into the thorax

8. What is the condition of the majority of voltage-gated Na-channels during the depolarizing phase of an action potential?

A) activation gate closed; inactivation gate closed

B) activation gate open; inactivation gate closed

C) activation gate closed; inactivation gate open

D) activation gate open; inactivation gate open

9. At a chemical synapse, which is the correct sequence of events leading to the generation of a postsynaptic potential (PSP)?

A) binding of neurotransmitter to receptor Ca⁺² influx fusion of vesicles with cell membrane

B) binding of neurotransmitter to receptor fusion of vesicles with cell membrane Ca⁺² influx

C) Ca⁺² influx fusion of vesicles with cell membrane binding of neurotransmitter to receptor

D) Ca⁺² influx binding of neurotransmitter to receptor fusion of vesicles with cell membrane

10. Ca⁺² ions play which role inside a contracting muscle fiber?

A) allow troponin to bind tropomyosin

B) allow tropomyosin to bind actin

C) transmit action potential across gap separating cell membrane and sarcoplasmic reticulum

D) cause the sarcoplasmic reticulum to release ATP

11. During accomodation, the human visual system is adjusting

A) dietary requirement for vitamin A

B) sensitivity to light intensity

C) sensitivity to light wavelength

D) distance at which objects are in focus

12. The rods and cones of the human retina both absorb light energy and convert it into an electrical potential. However, the way in which rods and cones detect light differs in all of the following regards, except

A) the isomer of retinal used to absorb light

B) the opsin protein that is complexed to retinal

C) the wavelength of light absorbed by the retinal/opsin complex

D) the sensitivity to light intensity

13. Which of the following is not true of a sporophyte?

A) arises by fertilization

B) composed of diploid cells

C) grows in cell number by mitosis

D) generates gametes by meiosis

14. In plants, phototropism refers to

A) formation of sidebranches by axillary buds

B) opening of stomata at the light of day

C) bending of a shoot towards light

D) requirement for sunlight to photosynthesize sugar

15. In plants, which tissue blocks the passage of water through the apoplastic pathway?

A) endodermis

B) guard cells

C) vascular cambium

D) plasmodesmata

16. What happens to most of the water absorbed by a plant's roots?

A) used (with CO₂) to synthesize sugar

B) used to hydrolyze ATP to ADP

C) evaporates from leaves to atmosphere

D) returned to soil by osmosis

17. With respect to the microvilli of the intestine, all of the following statements are true except

A) absorb nutrients from digested food

B) tens or hundreds per epithelial cell

C) located on basal side of epithelium

D) extend into the intestinal lumen

18. The striations seen in striated muscle are composed of

A) individual muscle cells within the muscle

B) individual myofibrils within the muscle cell

C) ordered array of cytoskeletal proteins within the muscle cell

D) tubules connecting muscle cell membrane to the sarcoplasmic reticulum

19. Which of the following medical conditions results from an abnormality in the self-tolerance of the immune system?

A) allergy

B) autoimmune disease

C) immunodeficiency disease

D) rejection of a transplanted organ

20. Release of epinephrine into the blood causes all of the following responses except

A) body's own proteins are broken down into glucose

B) release of glucose into the blood

C) reduced blood flow to digestive system

D) heart beat increases in rapidity and force

21. Which of the following statements is not true of shivering?

A) characteristic of many endothermic animals

B) involves asynchronous muscle fiber contractions

C) converts [part of] the chemical energy of ATP into heat

D) reduces heat loss to the surrounding environment

22. Why does immunization reduce one's likelihood of catching the disease in question?

A) mast cells release histamine in response to the immunization

B) plasma cells secrete antibodies in response to the immunization

C) immune system produces memory cells specific to that antigen

D) immunoglobulin genes rearrange for greater specificity to that antigen

Questions 23-27 are short-answer essay questions. Answers are shown in italics.

23. Membrane physiology

A. [8 pts]

In animal cells, the cell membrane contains a protein called the 'Na/K pump'. Describe the molecular events that (i) activate the pump and (ii) result from activation of the pump. Be certain to distinguish these activities with respect to the two sides of the cell membrane.

1. The Na/K pump is activated by the hydrolysis of ATP to ADP and phosphate.

2. The Na/K pump transports Na⁺ ions from the cytoplasm to the extracellular space, and transports K⁺ ions from the extracellular space to the cytoplasm.

B. [6 pts]

Cell membranes contain Na-channel proteins that are specific for Na⁺ ions. Assuming that the channel is open, what two factors determine the direction that Na⁺ ions flow through the channel?

1. Na⁺ ions diffuse down their concentration gradient [from outside to inside].

2. Na⁺ ions flow towards the side of the cell membrane that is negatively charged [at rest, the inside].

C. [7 pts]

Define osmosis, and explain why osmosis plays a significant role in any one of the biological processes discussed in this course.

Osmosis is the flow of water between adjoining compartments that differ in osmolarity, i.e. total solute concentration. This flow is directed from the compartment with the lower solute concentration to the compartment with the higher solute concentration.

We have discussed many examples of osmosis in BIO214. For instance, nearly all fish maintain an internal osmolarity different from that of the surrounding water. Saltwater fish live in a hyperosmotic environment and are constantly losing water through their gills by osmosis, whereas freshwater fish live in a hypoosmotic environment and are constantly taking up water through their gills by osmosis. Both kinds of fish must rely upon drinking and/or excretion to compensate for the effects of osmosis.

24. Hormones

A. [5 pts]

What is the distinction between an endocrine gland and an exocrine gland?

An endocrine gland secretes hormones into the blood [via the interstitial fluid].

An exocrine gland secretes into a duct or tube that carries the secretion away from the gland.

B. [3 pts]

Estrogen and progesterone are derivatives of a naturally occuring chemical found in all animal cells. What chemical is it?

cholesterol

C. [8 pts]

Name (i) the two halves of the adrenal gland and (ii) the class of hormones that each one produces. Note: to receive full credit, it must be clear which structure produces which hormones.

The adrenal medulla secretes catecholamines [= epinephrine + norepinephrine]

The adrenal cortex secretes corticosteroids [= glucocorticoids + mineralocorticoids]

D. [5 pts]

In plants, the hormone auxin is responsible for apical dominance. Describe apical dominance.

In apical dominance, a shoot apical meristem secretes auxin which is transported down the shoot and inhibits the growth of axillary buds.

25. Comparative biology

A. [8 pts]

Vertebrate animals have a closed circulatory system in which oxygenated blood is transported from the respiratory organs to the remainder of the body. However, the oxygenated blood follows a different route in a fish and in a mammal. Explain this difference in anatomical terms.

In fish, blood leaving the heart passes through the gills - where it becomes oxygenated - and then flows directly through blood vessels to the remainder of the body.

In mammals, blood is oxygenated in the lungs (pulmonary circuit), and must return to the left side of the heart before it is pumped out through blood vessels to the remainder of the body (systemic circuit).

B. [3 pts]

The human eye can only sense certain wavelengths of electromagnetic radiation, commonly referred to as 'visible light'. Describe an example of some other animal species whose photoreceptors can sense a wavelength that we can not see.

We discussed two examples. First, the rattlesnake (and other pit vipers) have photoreceptors that detect infrared wavelenths. Second, insects have photoreceptors that detect ultraviolet (UV) wavelengths.

C. [10 pts]

Name the four basic divisions of plants, and use the table below to show which of these groups reproduce by means of pollen and/or flowers.

Plant Division	Do they make pollen? Circle correct answer.	Do they make flowers? Circle correct answer.
bryophytes	YES NO	YES NO
pteridophytes	YES NO	YES NO
gymnosperms	YES NO	YES NO
angiosperms	YES NO	YES NO

26. Interfacing with the environment

A. [7 pts]

Most fish live in water whose osmolarity differs significantly from the osmolarity of their own bodily fluids. Choosing either a freshwater fish or a saltwater fish, describe two physiological processes that help the fish to maintain its internal osmolarity.

Freshwater fish

drinks only small quantitites of water

excretes large quantities of dilute urine

uses active transport to absorb salt ions through its gills

Saltwater fish

drinks large quantities of water

excretes small quantities of concentrated urine

uses active transport to excrete salt ions through its gills

B. [7 pts]

Mammals elevate their body temperature by generating heat. Describe (1) an adaptation of the body surface that helps a mammal to retain body heat when exposed to a cold environment, and (2) an adaptation of the body surface that helps a mammal to lose excess body heat when exposed to a hot environment.

Mammals have several adaptations of the body surface to retain body heat, including fur and subcutaneous fat, both of which serve as thermal insulation. Another adaptation is the ability to reduce blood flow to the skin by means of vasoconstriction when the outside environment is cold.

_________________________________________________________________________________

Mammals also have adaptations of the body surface to facilitate the loss of excess body heat. One example is sweating, which leads to cooling by evaporation. Another adaptation for heat loss is the ability to increase blood flow to the skin by means of vasodilation when the outside environment is warm.

C. [7 pts]

Some animals respire by breathing air with lungs while other animals respire by ventilating water over gills. Describe two features of the respiratory surface that are characteristic of both lungs and gills, and that facilitate the exchange of O₂ and CO₂ with the environment.

Both lungs and gills have a large respiratory surface area over which O₂ and CO₂ can be exchanged.
The respiratory surfaces of both lungs and gills are composed of flat, thin cells (= squamous epithelia) underlaid by a dense network of capillaries. As a result, O₂ and CO₂ only have to diffuse a short distance to be exchanged between the blood and outside environment.

27. Nerve and muscle

A. [3 pts]

Define the term sensory neuron.

A sensory neuron is a nerve cell that transduces an external stimulus into an electrical signal that can be processed by the remainder of the nervous system.

B. [3 pts]

Define the term interneuron.

An interneuron is a nerve cell that interacts exclusively with other neurons.

C. [3 pts]

Define the term motor neuron.

A motor neuron is a nerve cell that synapses with a non-neural 'effector' cell, like a muscle fiber or gland cell.

D. [6 pts]

Define the term motor unit.

A motor unit is a group of muscle fibers (= muscle cells) that are innervated by the same motor neuron. The entire motor unit contracts in synchrony when that motor neuron sends an excitatory signal.

E. [6 pts]

The drawing below represents an action potential. Name the labeled phases of the action potential in the spaces provided.

I. __depolarizing phase________

II. __repolarizing phase________

III. __undershoot______________

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