Module 4: Carbohydrates - Plant-Derived Energy Nutrients

Insulin is produced in and released from the __________.

Pancreas

Most dietary __________ passes through the digestive system without being digested and absorbed.

Fiber

__________ is a key hormone produced by the alpha cells of the pancreas that plays an important role in regulating blood glucose levels during times of fasting.

Glucagon

Which of the following statements is correct?

Gluconeogenesis generates glucose from noncarbohydrate sources, such as amino acids, when blood glucose levels are low

The body can either use __________ for energy, convert it to glycogen, or store it as fat.

Glucose

__________ is the most abundant sugar molecule and the preferred source of energy for the brain.

Glucose

As part of the response to increased blood glucose after a meal, insulin triggers the number of __________ on the cell membranes in the body to be increased.

Glucose Transporters

Animals store glucose polysaccharides in the form of __________.

Glycogen

__________ is the storage form of glucose in the liver and muscles of humans and animals.

Glycogen

An overnight fast causes decreases in blood glucose levels. Maintaining normal blood glucose levels is important to prevent hypoglycemia. In healthy individual, glucagon helps to maintain normal blood glucose levels. Rank the events in the sequence they follow from a lower blood glucose level to a normal blood glucose level.

- Blood glucose levels fall. - When blood pressure levels are low, glucagon is secreted from the pancreas into the bloodstream. - Glucagon targets the liver and stimulates glycogenolysis to release glucose into the bloodstream. - Gluconeogenesis in the liver is activated and converts amino acids and other noncarbohydrate sources to glucose, which is released into the bloodstream.

Hormones That Have No Effect on Blood Glucose Levels

- Cholecystokinin - Ghrelin

These are absorbed by the mucosal cells lining the small intestine and enter into the bloodstream

- Galactose - Glucose - Fructose

Hormones That Raise Blood Glucose Levels

- Glucagon - Epinephrine - Norepinephrine

Fiber is a polysaccharide that gives plants their structure, and the bonds that hold the fiber molecules together are difficult to digest by the human body. Fiber plays an important role in a healthy diet by promoting healthy passage of stool and by helping to prevent many digestive and chronic diseases.

- Humans do not produce enzymes in the small intestine that can break down fiber - Fiber is important for adding bulk to stool and making it easier to eliminate stool as long as water intake is adequate - Fermentation of fiber by gut bacteria results in production of certain molecules which can be used by cells of the large intestine for energy

Enzymes that are responsible for breakdown of disaccharides

- Maltase - Lactase - Sucrase

Enzymes that are responsible for breakdown of starches

- Salivary amylase - Pancreatic amylase

__________ are a category of nutrient compounds consisting of long chains of sugar molecules.

Complex carbohydrates

__________ consist of two molecules of sugar joined together.

Disaccharides

In a healthy individual, insulin is secreted in levels sufficient to maintain a normal blood glucose level following a meal. Rank the steps to indicate the effects of insulin to bring blood glucose levels to normal following a meal.

Higher blood glucose levels --> Normal blood glucose levels - Blood glucose levels rise following the digestion of a carbohydrate-rich meal. - Insulin is secreted from the pancreas into the bloodstream. - Insulin increases the number of glucose transporters on the cell membranes to allow the transport of glucose into the cells. - Insulin stimulates the liver to store excess glucose as glycogen and stimulates glycogenesis in the muscle cells. - Insulin stimulates lipogenesis in the adipose tissue.

__________ occurs when blood glucose levels drop to lower-than-normal levels.

Hypoglycemia

Hormones That Lower Blood Glucose Levels

Insulin

__________ is a key hormone produced by the beta cells of the pancreas that plays a key role in regulating blood glucose levels after a meal.

Insulin

In response to insulin or glucagon, either glycogenesis or gluconeogenesis, respectively will take place in the __________.

Liver

__________ are a category of single sugar molecules that are absorbed easily in the small intestine.

Monosaccharides

Glucose is stored as glycogen in the liver and in __________.

Muscles

__________ Are a category of sugars that contain either one or two molecules.

Simple carbohydrates

Plants store glucose as polysaccharides in the form of __________.

Starch

Carbohydrate digestion begins in the mouth and ends with the elimination of dietary fiber that the colon bacteria cannot ferment through the large intestine. Review the steps of carbohydrate digestion in the focus figure. Trace the digestion of carbohydrates through the gastrointestinal tract by labeling the steps in the order they occur after you take your first bite of a piece of bread.

Step 1 - Salivary enzymes break down starch in the bread into smaller chains and the disaccharide maltose Step 2 - Salivary amylase is inactivated by stomach acid Step 3 - Pancreatic amylase breaks down starch into the disaccharide maltose Step 4 - Enzymes of the small intestine digest disaccharides into monosaccharides Step 5 - Some dietary fiber in the bread is fermented by bacteria; the rest passes through the large intestine to be eliminated

__________ is a type of simple carbohydrate composed of a glucose molecule and a fructose molecule.

Sucrose