Chapter 2: Comparative Nutrition and Digestive physiology

Question 1

across animal species, the process of digestion is basically the same, involving 3 steps:

Answer 1

• physical/ mechanical breakdown: chewing, tearing, grinding, mixing
• chemical breakdown: HCl, bile salts- emulsification
• enzymatic breakdown: pancreas, small intestine enzymes

Question 2

since proteins are too large to be absorbed intact, describe how they’re broken down during digestion

Answer 2

proteins –> polypeptides –> which are broken into tripeptides, dipeptides, and amino acids: these are small enough to be absorbed into the digestive tract

Question 3

Purpose of GI tract?

Answer 3

• assimilation of nutrients
• exclusion of unnecessary/ harmful substances
• no microbes can cross the intestinal barrier as normal living matter- intestine works hard to keep bacteria out.

Question 4

digestion of:

• proteins
• starches
• structural CHO (fibres)
• triglycerides

Answer 4

• proteins–> polypeptides –> peptides and amino acids
• starches –> sugars
• structural CHO (fibres) –> sugar fermentation (microbial)
• triglycerides –> fatty acids, mono and diglycerides

Question 5

Name 5 things that can vary in digestive physiology among species

Answer 5

1. mouth (eating)- specialized mouth structures
2. digestive tract (structures, fxns of digestive tract depend on diet)
3. absorption of nutrients (transporters etc can vary)
4. metabolism of nutrients (maintenance, production/ work)
5. excretion of waste products

Question 6

Feces is the ___ nutrients & non- nutrients, bacteria, and soughed cells

Answer 6

unabsorbed

Question 7

urine is the excretion of ____ nutrients & waste products; excretion of excess ___

Answer 7

absorbed

nitrogen

Question 8

what are the 3 different forms of urine?

Answer 8

1. ammoniotelic
2. ureotelic
3. uricotelic

Question 9

ammoniotelic

Answer 9

(ammonia)

• fish
• simplest form, very soluble
• toxic, but fish are in water, so don’t need to waste energy to get it to a less toxic form (just get rid of it into the water)

Question 10

ureotelic

Answer 10

(urea)

• mammals
• urine has been converted to a less toxic form (has to stay inside until can be excreted)

Question 11

uricotelic

Answer 11

(uric acid)

• birds and land reptiles
• highly concentrated, insoluble, less toxic nitrogenous waste

Question 12

Advantages for birds to excrete uric acid (less toxic form?)

Answer 12

1) less weight for flying
2) birds lay eggs; the uric acid builds up inside the egg before it hatches; since uric acids is insoluble, it doesn’t poison itself with the nitrogenous waste

Question 13

how do amphibians excrete nitrogenous waste?

Answer 13

• larvae= ammoniotelic: ammonia diffuses through membranes and is more water soluble than other nitrogenous waste
• adults= ureotelic: have bladder- urea is less toxic and needs less water that ammonia