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Topics in Depth

The Theme of Test Your Knowledge in Animal Nutrition and Digestion

Nutrition

1) Why are only some amino acids called essential?

2) Iron and potassium are included in many multi-vitamins, but they aren't vitamins. To what nutrient class do they belong?

3) Why can't vegetarians and herbivores survive on a diet of just corn and nuts?

4) Proper nutrition requires a diet that supplies an animal with:
a) Essential nutrients
b) Energy
c) Organic and inorganic molecules
d) Essential amino acids
e) All of the above

5) True or False. An animal doesn't have to eat carbohydrates to achieve proper nutrition, as long as it receives all of its essential vitamins and minerals.

From Start to Finish

1) What controls the pH of the stomach? What controls the pH of the small intestine?

2) Bile is not produced by the small intestine; rather it is produced by the       and stored in the      .
a. Pancreas/Gallbladder
b. Liver/Gallbladder
c. Liver/Pancreas
d. Large Intestine/Liver
e. Pancreas / Liver

3) What allows the villi and microvilli to absorb a large amount of nutrients?

4) Where does carbohydrate digestion begin? Where does fat digestion begin? What biological component is responsible for nutrient digestion in these areas?

5) What is the difference between nutrient active and passive transport into the blood stream?

Osmoregulation

1) Describe water movement in an isosmotic environment.

2) Why do nitrogenous wastes come from the digestion of protein, but not fats or carbohydrates?

3) Through osmosis, water flows from a       solution to one that is      .
a. Hyperosmotic / Hypoosmotic
b. Isoosmotic / Hypoosmotic
c. Hypoosmotic / Hyperosmotic
d. Intracellular / Extracellular
e. Hypoosmotic / Isoosmotic

4) Why won't camels excrete their nitrogenous wastes as ammonium?

5) Use what you know about osmosis to describe how reverse osmosis is used to purify water.

Water Balance and the Kidney

1) How does a longer descending Loop of Henle aid in water conservation?

2) What are the two critical components to the countercurrent multiplier system?
a. NaCl and H+
b. NaCl and urea
c. The vasa recta and collecting duct
d. The inner medulla and distal tubule
e. The descending and ascending Loops of Henle

3) Which is NOT a component in filtrate?
a. Small proteins
b. Ammonia
c. Red blood cells
d. Vitamins
e. Metabolized drugs

4) What are the four stages of excretion and where do they occur within the nephron?

5) As filtrate passes through the proximal tubule,       and       are removed.
a. Glucose / amino acids
b. Red blood cells / H+
c. Ammonia / H+
d. NaCl / water
e. Toxins / water

6) How does the structure of the vasa recta assist its function to maintain the inner medulla's high osmolarity?

Hormones

1. Cholecystokinin is released by      , while       causes secretin secretion.
a. sugar-containing chyme / acid
b. Acid / fatty acid-containing chyme
c. Peptide and fatty acid-containing chyme / acid
d. Peristalsis / fatty acid-containing chyme
e. Secretin / Gastrin

2. Why is gastrin usually secreted before secretin?

3. ADH release is stimulated by      , while       stimulates ANP release.
a. Hyperosmotic blood / low blood volume
b. Hypoosmotic blood / low blood pressure
c. Hyperosmotic blood / high blood pressure
d. Hypoosmotic blood / high blood pressure
e. None of the above.

4. Where and how does aldosterone work to increase blood volume?

5. From where is ANP secreted? What is it secreted in response to?

Answers

Nutrition

1) Why are only some amino acids called essential?
Of the 20 amino acids, half can be synthesized in the body by using nitrogen. The remaining "essential amino acids" are not synthesized in the body, and must be a part of an animal's diet.

2) Iron and potassium are included in many multi-vitamins, but they aren't vitamins. To what nutrient class do they belong?
Minerals. These are inorganic (don't contain a carbon atom) nutrients.

3) Why can't vegetarians and herbivores survive on a diet of just corn and nuts?
The essential amino acids must come from an animal's diet, and one type of plant doesn't contain all 8-9 of these amino acids. A diet with plenty of variety is necessary for proper nutrition.

4) e

5) True or False. An animal doesn't have to eat carbohydrates to achieve proper nutrition, as long as it receives all of its essential vitamins and minerals.
False. Carbohydrates are an essential part of proper nutrition. They are broken down into sugar compounds that become an important energy source for proper cellular function. 

From Start to Finish

1) What controls the pH of the stomach? What controls the pH of the small intestine?
The acidic pH of the stomach is regulated by the parietal cells. They secrete hydrochloric acid and create an acidic environment where pepsin and other enzymes function properly. The small intestine is pH neutral because the pancreas secretes HCO3-.

2) b

3) What allows the villi and microvilli to absorb a large amount of nutrients?
These structures increase the surface area of the epithelial cells, allowing for more nutrient absorption.

4) Where does carbohydrate digestion begin? Where does fat digestion begin? What biological component is responsible for nutrient digestion in these areas?
Carbohydrate digestion begins in the oral cavity with salivary amylase. Fats remain relatively untouched until the small intestine where the bile and pancreatic lipase breaks them down into single fatty acids.

5) What is the difference between nutrient active and passive transport into the blood stream?
Active transport requires energy and allows nutrients to be absorbed despite the concentration gradient, allowing for more absorption. Passive transport does not require energy, and absorption occurs along the concentration gradient.

Osmoregulation

1) Describe water movement in an isosmotic environment.
In an isosmotic environment, water will move across a membrane at equal rates so the net amount of water on each side remains constant.

2) Why do nitrogenous wastes come from the digestion of protein, but not fats or carbohydrates?
Nitrogenous wastes are made up of nitrogen ions. Nitrogen is found in proteins, but not fats or carbohydrates.

3) a

4) Why won't camels excrete their nitrogenous wastes as ammonium?
Camels need to conserve water at all costs because of their dry environment. Ammonium is a highly toxic ion and can only be stored at very low concentrations, with plenty of water. When the nitrogenous waste is excreted, precious water goes with it.

5) Use what you know about osmosis to describe how reverse osmosis is used to purify water.
Reverse osmosis refers to the process by which external pressure prevents water from moving into a more dilute environment. When drinking water has a relatively high concentration of ions, scientists can purify it by pushing those solutes out, leaving pure water.

Water Balance and the Kidney

1) How does a longer descending Loop of Henle aid in water conservation?
The descending Loop of Henle is responsible for reabsorption of water, and therefore increasing urine osmolarity. When the Loop dips into the kidney's inner medulla where the interstitial fluid osmolarity is quite high, more water can be reabsorbed and conserved.

2) e

3) c

4) What are the four stages of excretion and where do they occur within the nephron?
Filtration – Glomerulus
Reabsorption – Proximal tubule, Loop of Henle
Secretion – Distal tubule, Collecting duct
Excretion – Ureter, urethra

5) a

6) How does the structure of the vasa recta assist its function to maintain the inner medulla's high osmolarity?
The blood of the vasa recta flows counter to that of the filtrate through the Loop of Henle. Because it is highly permeable to both salt and water, the vasa recta will remove excess water (coming from the descending Loop) and NaCl (coming from the ascending Loop) from the interstitial fluid. It therefore maintains the concentration gradient set up by the countercurrent multiplier system, and prevents the fluid from becoming too dilute or concentrated.

Hormones

1) c

2) Why is gastrin usually secreted before secretin?
Gastrin stimulates the release of HCl from the parietal cells and pepsinogen from the chief cells in the stomach. This acidic chyme is what stimulates the release of secretin in the small intestine.

3) c

4) Where and how does aldosterone work to increase blood volume?
Aldosterone works at the nephron's distal tubule and collecting duct, and increases the amount of water and NaCl that is reabsorbed back into the blood. Not only does it increase the blood volume, but it also increases blood pressure.

5) From where is ANP secreted? What is it secreted in response to?
ANP is secreted from the heart atria in response to low blood pressure or volume.

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