How many monosaccharide units define a disaccharide?
Two units.
What are derived carbohydrates called when they are sugar alcohols?
Sugar alcohols.
How are monosaccharides grouped by carbon count?
Trioses have 3 carbons, tetroses 4, pentoses 5, and hexoses 6.
Which functional group defines an aldose?
An aldehyde group.
Which functional group defines a ketose?
A ketone group.
Which monosaccharides are aldoses?
Glucose and galactose.
What structural forms can glucose, galactose, and fructose adopt?
Cyclic structures.
Why do monosaccharide isomers affect carbohydrate, amino acid, and lipid use?
Enzymes act on specific isomers.
Which three monosaccharide isomers are biologically significant in human metabolism?
α-D-glucose, β-D-fructose, and α-D-galactose.
What is glucose’s molecular formula?
C₆H₁₂O₆.
Which energy source do the brain and mature erythrocytes use?
Glucose only.
What are polyols?
Sugar alcohols formed by reducing a sugar’s aldehyde or ketone group to a hydroxyl group.
What joins the two monosaccharides in a disaccharide?
A glycosidic bond formed through the loss of one water molecule.
How does invert sugar differ structurally from sucrose?
Invert sugar is free glucose and fructose in a 1:1 ratio; sucrose chemically bonds them.
What are lactose’s two component sugars and their linkage?
Glucose and galactose joined by a β-1,4 glycosidic bond.
What causes lactose intolerance?
Insufficient lactase activity in the small intestine.
What happens to undigested lactose when it reaches the large intestine?
Bacteria ferment it, producing gas and organic acids.
What share of daily energy should carbohydrates provide?
45–60%.
How much energy does one gram of carbohydrate provide?
4 kcal.
How is the daily carbohydrate requirement in grams calculated?
Energy from carbohydrate in kcal divided by 4 kcal/g.
How do glucose and galactose enter intestinal cells during carbohydrate absorption?
By active transport.
How many monosaccharide units form an oligosaccharide, and how are they joined?
Three to ten units joined by glycosidic bonds.
What is the prebiotic effect of partly or fully indigestible oligosaccharides?
They support beneficial gut bacteria.
Which elements do carbohydrates contain?
Carbon, hydrogen, and oxygen.
What is the general formula for carbohydrates?
How many monosaccharide units do simple carbohydrates contain?
One or two units.
How many monosaccharide units do complex carbohydrates contain?
Three or more units.
What defines a carbonyl group?
A carbon atom double-bonded to oxygen, .
Which functional groups contain carbonyl groups, according to the statement?
Aldehydes, ketones, carboxylic acids, esters, amides, and acid anhydrides.
Which nucleic acid contains ribose?
RNA.
Which foods and products contain free glucose?
Fruits, sweetened beverages, glucose syrup, candies, biscuits, and cakes.
What is fructose’s alternate name?
Levulose.
Where is fructose metabolized?
In the liver.
Which glucose epimer is galactose?
The C-4 epimer.
What causes toxic effects in galactosemia?
Accumulation of galactose and galactitol.
What does oxidation of a hexose’s C-6 hydroxyl-bearing carbon produce?
A uronic acid.
Which four processes does the uronic acid pathway support?
Detoxification, glycosaminoglycan synthesis, vitamin C synthesis, and L- and D-sugar interconversion.
Why must humans obtain vitamin C from their diet?
Humans lack the final enzyme in the uronic acid pathway.
What happens to bilirubin during glucuronidation?
It combines with glucuronic acid, becomes water-soluble, and is excreted in urine.
How much energy do polyols provide per gram?
2–2.5 kcal/g.
What effect can polyol intake above 50 g cause?
Osmotic diarrhea.
Which monosaccharides form maltose, and what is their linkage?
Two glucose molecules linked by an α-1,4 glycosidic bond.
What role does maltose play in starch digestion?
It is an intermediate product of starch digestion.
Which monosaccharides form sucrose, and what is their linkage?
One glucose and one fructose linked by an α-1,2 glycosidic bond.
Where is sucrose found as table sugar?
In sugar cane and sugar beet.
How does invert sugar compare with sucrose in sweetness and crystal size?
It is sweeter at the same concentration and forms smaller crystals.
What percentage of human milk is lactose?
7–8%.
What percentage of cow’s milk is lactose?
4–5%.
What causes primary lactose intolerance?
A genetically programmed decline in lactase after weaning.
What causes secondary lactose intolerance?
Injury to the intestinal mucosa.
How can lactose intolerance be managed?
Limit lactose, use lactase supplements, or choose lactose-free or fermented dairy products.
At 2500 kcal per day, how many grams of carbohydrates correspond to 45–60% of energy?
281–375 g/day.
How can carbohydrates determine erythrocyte cell specificity?
They contribute to erythrocyte blood-group specificity.
What role does cellulose serve in plant cell walls?
It provides rigidity and protection.
What roles do lipopolysaccharides serve in Gram-negative bacterial membranes?
They are structural and antigenic components.
Which monosaccharides occur in GOS, FOS, and MOS, respectively?
Galactose; fructose and glucose; glucose.
Which beneficial bacteria do galactooligosaccharides promote as prebiotics?
Bifidobacteria and Lactobacilli.
Where are short-chain FOS found mainly?
In wheat and rye.
What is the recommended upper daily intake of FOS?
20 g.
Why do humans incompletely digest raffinose-family oligosaccharides?
Humans lack α-galactosidase.
How many sugar units are in verbascose?
Five.
Which glucose epimer is mannose?
The C-2 epimer.
What monosaccharides and linkage make up trehalose?
Two glucose molecules linked by an α-1,1 glycosidic bond.
Answer 13 questions on Carbohydrates I.
1. Regarding carbohydrate classification by monosaccharide-unit count:
2. Which statements describe the distinction between simple and complex carbohydrates?
Go over the full study guide for Carbohydrates I.
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