Lactose

Definition

Lactose is a disaccharide sugar composed of two monosaccharides: glucose and galactose. It is primarily found in milk and dairy products and serves as an important source of energy for many organisms. Lactose is unique because it requires the enzyme lactase for its digestion, which can lead to lactose intolerance in individuals who do not produce sufficient amounts of this enzyme.

5 Must Know Facts For Your Next Test

1. Lactose makes up about 2-8% of milk's composition, varying by species, with human breast milk having the highest concentration.
2. The digestion of lactose begins in the small intestine, where lactase breaks it down into its constituent monosaccharides, glucose and galactose.
3. Lactose intolerance occurs when there is insufficient lactase enzyme, leading to digestive issues like bloating, gas, and diarrhea after consuming dairy products.
4. Some individuals may develop lactose intolerance later in life due to a decrease in lactase production as they age.
5. Lactose can also be found in dairy alternatives, where it may be added or removed depending on the product's formulation.

Review Questions

• Explain how lactose is digested in the human body and the role of lactase in this process.
  • Lactose digestion occurs mainly in the small intestine, where the enzyme lactase breaks down lactose into its two monosaccharides: glucose and galactose. This process is crucial because only these simpler sugars can be absorbed into the bloodstream. If lactase is insufficient, lactose remains undigested, leading to discomfort and symptoms associated with lactose intolerance.
• Discuss the impact of lactose intolerance on dietary choices and nutritional intake for affected individuals.
  • Lactose intolerance can significantly affect an individual's dietary choices, often leading them to avoid milk and dairy products to prevent uncomfortable symptoms. This avoidance may create challenges in obtaining adequate calcium and vitamin D, which are commonly found in dairy. As a result, those with lactose intolerance may need to seek alternative sources of these nutrients or consider lactose-free dairy options.
• Analyze the evolutionary advantages that might be associated with lactose tolerance in certain populations.
  • Lactose tolerance has evolved in certain human populations, particularly those with a history of dairy farming. The ability to digest lactose into adulthood offers significant nutritional advantages, such as access to a rich source of calories and nutrients from milk. This adaptation likely provided these populations with a survival advantage during periods of food scarcity or harsh conditions, enabling them to thrive where others could not. Consequently, areas with a history of dairying show higher frequencies of lactase persistence among their adult populations.

Related terms

glucose:

A simple sugar and a primary source of energy for cells; it is one of the two monosaccharides that make up lactose.

galactose:

A monosaccharide that combines with glucose to form lactose; it plays a crucial role in various biological processes.

lactase: An enzyme produced in the small intestine that breaks down lactose into glucose and galactose for easier absorption.