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Chapter 22: Problem 108

Cows can digest cellulose, but humans can’t. Why not?

Short Answer

Expert verified
Cows can digest cellulose because they have a complex ruminant digestive system with a four-chambered stomach, which contains microorganisms that produce cellulase enzymes to break down cellulose into simple sugars for energy. In contrast, humans have a monogastric digestive system and lack the necessary enzymes and microorganisms to break down cellulose, making it indigestible for them.

Step by step solution

01

Understanding Cellulose

Cellulose is a complex carbohydrate, a long chain of glucose molecules linked together by beta-1,4-glycosidic bonds. It is the main component of plant cell walls and is very difficult to break down because most animals lack the enzymes (cellulases) necessary to break these bonds.
02

Examining Digestive Systems

Cows and humans have different types of digestive systems. The human digestive system is a monogastric system, meaning it has a single-chambered stomach. In contrast, cows have a complex ruminant digestive system with a four-chambered stomach (rumen, reticulum, omasum, and abomasum).
03

Exploring Rumen and Microorganisms

In cows, the rumen is essentially a fermentation vat, where large amounts of microorganisms (mostly bacteria and protozoa) live. These microorganisms produce enzymes called cellulases that are capable of breaking down cellulose into simple sugars for energy.
04

Role of the Microorganisms in Cows

When cows eat plant material containing cellulose, it goes into the rumen, where microorganisms ferment and break down the cellulose into short-chain fatty acids and other compounds, which are absorbed into the bloodstream and used for energy.
05

Lack of Cellulases in Humans

Humans lack both rumen and microorganisms to break down cellulose because they do not naturally produce cellulase enzymes in their digestive system. Consequently, humans cannot break down cellulose efficiently, and there is limited energy extraction from cellulose present in plant-based foods. In conclusion, cows can digest cellulose due to their complex ruminant digestive system that contains microorganisms capable of producing cellulase enzymes to break down the beta-1,4-glycosidic bonds of cellulose. On the other hand, humans cannot digest cellulose because they have a monogastric digestive system and lack the enzymes required to break down cellulose.

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Most popular questions from this chapter

Aspartame, the artificial sweetener marketed under the name NutraSweet, is a methyl ester of a dipeptide: a. What two amino acids are used to prepare aspartame? b. There is concern that methanol may be produced by the decomposition of aspartame. From what portion of the molecule can methanol be produced? Write an equation for this reaction.

Polychlorinated dibenzo-p-dioxins (PCDDs) are highly toxic substances that are present in trace amounts as by-products of some chemical manufacturing processes. They have been implicated in a number of environmental incidents—for example, the chemical contamination at Love Canal and the herbicide spraying in Vietnam. The structure of dibenzo-pdioxin, along with the customary numbering convention, is The most toxic PCDD is 2,3,7,8-tetrachloro-dibenzo-p-dioxin. Draw the structure of this compound. Also draw the structures of two other isomers containing four chlorine atoms.

Esterification reactions are carried out in the presence of a strong acid such as \(\mathrm{H}_{2} \mathrm{SO}_{4} \cdot \mathrm{A}\) carboxylic acid is warmed with an alcohol, and an ester and water are formed. You may have made a fruity-smelling ester in the lab when studying organic functional groups. Name the carboxylic acid that is necessary to complete the following esterification reaction.

Alcohols are very useful starting materials for the production of many different compounds. The following conversions, starting with 1-butanol, can be carried out in two or more steps. Show the steps (reactants/catalysts) you would follow to carry out the conversions, drawing the formula for the organic product in each step. For each step, a major product must be produced. (See Exercise \(68 . )\) (Hint: In the presence of \(\mathrm{H}^{+},\) an alcohol is converted into an alkene and water. This is the exact reverse of the reaction of adding water to an alkene to form an alcohol.) $$ \begin{array}{l}{\text { a. } 1 \text { -butanol } \longrightarrow \text { butane }} \\ {\text { b. } 1 \text { -butanol } \longrightarrow 2 \text { -butanone }}\end{array} $$

Which of the following polymers would be stronger or more rigid? Explain your choices. a. The copolymer of ethylene glycol and terephthalic acid or the copolymer of \(1,2\) -diaminoethane and terephthalic acid $\left(1,2 \text { -diaminoethane }=\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\right)$ b. The polymer of \(\mathrm{HO}-\left(\mathrm{CH}_{2}\right)_{6}-\mathrm{CO}_{2} \mathrm{H}\) or that of c. Polyacetylene or polyethylene (The monomer in polyacetylene is ethyne.)
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