SECOND MIDTERM EXAM
MULTIPLE CHOICE [4 points/question]
Correct answer in bold.
1. Which of the following must be acquired from the environment by a heterotroph, but not by an autotroph?
A) H2O
B) O2
C) ATP
D) carbon skeletons
2. Gastric glands secrete all of the following compounds except
A) bicarbonate ions (HCO3-)
B) hydrochloric acid (HCl)
C) pepsinogen
D) mucus
3. Bile salts work in combination with which enzyme to bring about the digestion of fat?
A) amylase
B) lipase
C) pepsin
D) trypsin
4. Which of the following organs does not synthesize any enzyme(s) that digest carbohydrates?
A) salivary gland
B) stomach
C) pancreas
D) small intestine
5. Which of the following statements most accurately describes the velocity of blood as it proceeds through the circulatory system?
A) Blood flows when the heart is contracting, and stops when the heart is relaxed.
B) Blood slows down from artery to capillary; speeds up from capillary to vein.
C) Blood speeds up from artery to capillary; slows down from capillary to vein.
D) Blood slows down continuously from artery to capillary to vein.
6. The majority of the CO2 in the human bloodstream is transported in which chemical form?
A) CO2 bound to hemoglobin
B) CO2 dissolved in blood plasma
C) bicarbonate ion (HCO3-) dissolved in the blood plasma
D) carbonic anhydrase in the cytoplasm of the red blood cell
7. In the gills of a fish, countercurrent exchange is possible because
A) Water moves anterior-to-posterior; blood flows anterior-to-posterior.
B) Water moves anterior-to-posterior; blood flows posterior-to-anterior.
C) Water moves posterior-to-anterior; blood flows anterior-to-posterior.
D) Water moves posterior-to-anterior; blood flows posterior-to-anterior.
8. In animals, which kind of tissue lines the lumen of a gland?
A) epithelial tissue
B) muscular tissue
C) nervous tissue
D) connective tissue
9. When a mammal breathes air or a shark swims with its mouth open, they are both performing which of the following behaviors?
A) countercurrent exchange
B) vasoconstriction
C) ingestion
D) ventilation
10. Freshwater fish display all of the following traits. Which of these traits does not help to maintain the fish's water balance?
A) secretion of ammonia through gills
B) absorption of salt ions through gills
C) excretion of large quantities of dilute urine
D) limited ingestion of water into the digestive system
Short-Answer Questions - correct answers in italics.
11. Blood pressure
A. [5 pts]
Blood pressure rises and falls with each heartbeat. Which heart chamber(s) are contracting when the blood pressure is highest? [If no chambers are contracting, write 'None'.]
Right and left ventricles
B. [5 pts]
What force keeps the blood pressure elevated when the heart relaxes between contractions?
The arteries are stretched by blood pressure during heart contraction. The elastic recoil of the artery walls keeps the blood pressurized while the heart is relaxed.
C. [5 pts]
How does blood pressure specifically affect the movement of H2O in or around a typical capillary?
Blood pressure is greater than the hydrostatic pressure of interstitial fluid, and thus tends to force water out of all capillaries.
[Not required for credit: Blood pressure is also responsible for the movement of blood through the capillaries from the arteries towards the veins.]
D. [5 pts]
What is the role of blood pressure in the excretion of urea by the kidney?
In the kidney, blood pressure forces water and its small solutes - including urea - from the blood plasma into the lumen of Bowman's capsule (the blind end of a nephron) in the process called filtration. The filtrate passes through slits between the capillary endothelial cells.
12. Respiration
During respiration, the human body acquires O2 from the atmosphere and transports it to tissues that need O2. Answer the following questions with respect to this process.
A. [10 pts]
Describe and number in order each cell membrane that an O2 molecule must cross when passing from the air to reach hemoglobin in the blood. For complete credit, you must accurately name each cell and (when applicable) identify its membranes as being apical, lateral, or basal.
1. Apical membrane of the alveolar epithelial cell.
2. Basal membrane of the alveolar epithelial cell.
3. Basal membrane of the capillary endothelial cell.
4. Apical membrane of the capillary endothelial cell.
5. Cell membrane of the red blood cell.
B. [3 pts]
How does the O2 molecule cross these cell membranes? [mark one]
_XX__ Simple diffusion across the lipid bilayer.
_____ Facilitated by a transport protein in the lipid bilayer.
C. [3 pts]
O2 molecules that enter the bloodstream in the lung are carried directly from the lung to the heart. Which is the first heart chamber they enter?
Left atrium
D. [4 pts]
The graph below shows the dissociation curve for O2 bound to hemoglobin in blood. Assume that:
(1) The partial pressure of O2 in arteries is 100 mm Hg.
(2) The partial pressure of O2 in the liver is 20 mm Hg.
(3) The blood flowing through the liver reaches equilibrium in terms of O2 release.
(4) There is no Bohr shift.
What percentage of the O2 will be released from hemoglobin as blood passes through the liver?
_65_ %
13. Digestion
During digestion, the human body acquires glucose from digesting food and provides it to tissues in need of glucose. Answer the following questions with respect to this process.
A. [8 pts]
Describe and number in order each cell membrane that glucose molecule must cross when passing from digesting food to the blood plasma. For complete credit, you must accurately name each cell and (when applicable) identify its membranes as being apical, lateral, or basal.
1. Apical membrane of the intestinal epithelial cell.
2. Basal membrane of the intestinal epithelial cell.
3. Basal membrane of the capillary endothelial cell.
4. Apical membrane of the capillary endothelial cell.
B. [3 pts]
How does glucose cross these cell membranes? [mark one]
_____ Simple diffusion across the lipid bilayer.
_XX__ Facilitated by a transport protein in the lipid bilayer.
C. [3 pts]
Most of the glucose molecules that enter the blood in the digestive system are carried to the heart. Which is the first heart chamber they enter?
Right atrium
D. [6 pts]
If a human being were injected with concentrated glucose to raise the blood glucose concentration to 0.2%, their body would respond by rapidly bringing the glucose concentration back down to 0.1% (= normal).
Describe the sequence of cellular events that account for this response.
In response to elevated blood glucose, the beta cells of the pancreas secrete the hormone insulin into the bloodstream. Insulin causes cells to absorb glucose from the blood, and convert it into glycogen. This decreases the blood glucose concentration.
14. Animal tissues
A. [9 pts]
Three different epithelia are depicted below. What is the anatomical classification of each epithelium?
A1. __simple cuboidal_________
A2. __stratified squamous_____
A3. __simple columnar________
B. [5 pts]
The epithelial cells lining your small intestine have a unique structure (not found anywhere else in the body) on their apical surface. Name and describe these structures.
The epithelial cells lining the small intestine have microvilli on their apical surface. Microvilli are small, finger-shaped projections of the apical cell membrane.
C. [6 pts]
Describe the cellular organization and chemical composition of cartilage.
The cartilage cells [chondrocytes] are separated from one another by a rubbery extracellular matrix.
This extracellular matrix is composed of collagen fibers embedded in a gel primarily composed of chondroitin sulfate.