structures and fiber

Question 0

List the monosaccharides and disaccharides and describe their basic structures.

Answer 0

Monosaccharides are single-sugar molecules that are made up of carbon, hydrogen, and oxygen atoms in the ratio of 1:2:1. C6H12O6.
All are referred to as hexose.
*glucose (6 sided ring, -OH on C #4 faces down)
*galactose (6 sided ring, -OH on C #4 faces up)
*fructose (5 sided ring)
Disaccharides consist of two monosaccharides. C12H22O11; reflects the loss of the water molecule.
*lactose= galactose + glucose
*maltose= glucose + glucose
*sucrose= fructose + glucose

Question 1

Describe how CHO intake (type, % of kcal) has changed in the US over the past century.

Answer 1

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Question 2

Identify complex CHO polysaccharides.

Answer 2

Polysaccharides: >10 mono-

• starch: glucose molecules. Corn, rice, wheat.
• amylose: linear; bonded together by a-1,4 glycosidic bonds
• amylopectin: branched; bonded together by a-1,4 & a-1,6 (occur at branch points)
• glycogen: found in the liver & skeletal muscles.
• liver glycogen: glucose is directly released into the blood
• muscle glycogen: fuel physical activity. Lacks enzymes.
• dietary fiber: cannot be digested. B-glycosidic bonds that are resistant to digestive enzymes.

Question 3

Identify oligosaccharides.

Answer 3

3-10 monosaccharides. Most common in foods.

• raffinose: galactose + glucose + fructose
• stachyose: 2 galactose + glucose + fructose

Question 4

Explain how mono- are used in the body other than as a fuel source.

Answer 4

Building blocks for nucleic acids (the pentose in DNA/RNA, ribose)

Question 5

How is a glycosidic bond formed?

Answer 5

Formed by a condensation rxn between two glucose molecules. one sugar of C1 -OH group and C4 -OH group of the second sugar.

Question 6

Identify, compare & contrast cellulose, glycogen, amylose & amylopectin

Answer 6

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Question 7

Why can’t cellulose be digested in the SI like starches?

Answer 7

Although starch and fiber are both made up of glucose molecules

Question 8

Compare and contrast insoluble and soluble fibers and their effects in the GI tract.

Answer 8

Soluble dietary fiber, pectin, tends to dissolve or swell in water and helps soften fecal matter, delay gastric emptying,and promotes growth of friendly bacteria in the colon.
insoluble dietary fiber, cellulose, remains relatively unchanged. Passes intact through the GI tract, which helps to increase fecal weight and volume.

Question 9

Discuss several health benefits from consuming dietary fiber.

Answer 9

Fiber cannot be digested in the human small intestine. This is because fiber contains B-glycosidic bonds that are resistant to digestive enzymes. Fiber passes from the small to the large intestine relatively intact. LI bacteria then begin to break down the fiber producing gas, lipids and other substances.

• Nourishes the cells that line the colon, promotes selective growth of beneficial intestinal bacteria.
• protects against cardiovascular disease, obesity, type 2 diabetes

Question 10

Explain how fiber in the diet might influence blood glucose or cholesterol levels.

Answer 10

Delayed gastric emptying may also help lower blood glucose levels. The viscous fiber may bind with dietary fat and cholesterol in the GI tract, making it less likely to be absorbed.

Question 11

Discuss the relationship between diverticular disease and the consumption of dietary fiber.

Answer 11

Diverticular disease: hard, dry feces, results in diverticula (protruding pouches in the colon)
Insufficient fiber intake. Dietary fiber helps prevent the formation of diverticula by increasing fecal mass, making bowel movements easier.