This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Bonds in cellulose that make it resistant to digestion is: 
Select and explain. 
A. b1-4, B. a1-6, C. b1-6, D. a1-6
A: b1-4
Answer: A: b1-4 
Explanation: Cellulose is the chief constituent of plant cell walls. It is insoluble and consists of b-D -glucopyranose units linked by b,1-4 bonds to form long, straight chains strengthened by cross-linking hydrogen bonds. Mammals lack any enzyme that hydrolyzes the b1 -4 bonds, and so cannot digest cellulose. Ref: Harper 28th edition, chapter 14.