Q: Which of the following best explains why plant cell walls are difficult for most animals to digest?

They are composed of cellulose, which forms strong $$eta-1$$,4-glycosidic bonds that most animals cannot break.

Question 1

Which of the following best explains why humans cannot digest cellulose efficiently, while ruminants can?

Accepted Answer

Humans lack the enzyme cellulase, which is required to break the $$eta-1$$,4-glycosidic bonds in cellulose.

Question 2

A cow is able to extract energy from plant cell walls primarily because:

Accepted Answer

Microbes in the rumen produce cellulase, which breaks down cellulose into volatile fatty acids.

Question 3

Which of the following volatile fatty acids (VFAs) produced in the rumen is primarily converted to glucose in the liver of ruminants?

Accepted Answer

Propionic acid

Question 4

Why do ruminants need to buffer their stomach acid less than omnivores?

Accepted Answer

Strong acids are not needed in the abomasum as much due to specialized digestion by microbes.

Question 5

Which of the following best describes the function of the abomasum in the ruminant digestive system?

Accepted Answer

It acts as the 'true stomach,' digesting microbial protein and bypass protein with strong acids and enzymes.

Question 6

A farmer notices that his cows are producing excessive gas after a diet change. Which dietary component is most likely responsible for this, and why?

Accepted Answer

Too much sugar, which leads to increased microbial fermentation and gas production in the rumen.

Question 7

Which of the following statements about the chewing motion of herbivores is correct?

Accepted Answer

Herbivores grind food side to side, rather than crush it up and down.

Question 8

Which muscle is more developed in herbivores compared to carnivores, and why?

Accepted Answer

The masseter muscle, because it is used for grinding plant material.

Question 9

In the context of ruminant digestion, what is the primary role of the reticulum?

Accepted Answer

It works with the rumen to trap and regurgitate partially digested food for rumination.

Question 10

Which of the following best explains why plant cell walls are difficult for most animals to digest?

Accepted Answer

They are composed of cellulose, which forms strong $$eta-1$$,4-glycosidic bonds that most animals cannot break.

Question 11

A ruminant is fed a diet high in cellulose but low in protein. Which of the following is a likely consequence?

Accepted Answer

Microbes in the rumen will have limited protein to synthesize microbial protein, potentially reducing the animal's protein intake.

Question 12

Which of the following is a correct sequence of events for the digestion of cellulose in a cow?

Accepted Answer

Cellulose enters the rumen → microbes ferment cellulose → VFAs are produced → VFAs are absorbed and used for energy.

Question 13

Why is it important for ruminants to regurgitate and re-chew their food (cud)?

Accepted Answer

It increases the surface area of plant material, enhancing microbial fermentation in the rumen.

Question 14

Which of the following best describes the fate of dead microbes in the ruminant digestive system?

Accepted Answer

They are digested as a source of protein in the abomasum and small intestine.

Question 15

A dairy cow is producing milk with a high lactose content. Which metabolic pathway is most directly responsible for the synthesis of lactose from volatile fatty acids?

Accepted Answer

Propionic acid is converted to glucose in the liver, which is then used to synthesize lactose.

Question 16

Which of the following is a real-world consequence of feeding ruminants a diet excessively high in simple sugars?

Accepted Answer

It can lead to excessive gas production in the rumen, causing discomfort and potential health issues.

Question 17

Which of the following best explains why cows do not fart but instead burp to expel gas?

Accepted Answer

Cows evolved a mechanism to burp quietly, exhaling gas through their lungs after it is produced in the rumen.

Question 18

Which of the following is NOT a volatile fatty acid produced by microbial fermentation in the rumen?

Accepted Answer

Lactic acid

Question 19

A ruminant is fed a diet with encapsulated 'bypass protein.' What is the main advantage of this dietary strategy?

Accepted Answer

It allows protein to escape microbial digestion in the rumen and be absorbed in the small intestine.

Digestive System Anatomy and Physiology of Ruminants

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