Exam 1

Identify the Acceptable Macronutrient Distribution Range (AMDR) for carbohydrates.

45 to 65 carbohydrates 25 to 35 fats 10 to 35 proteins

Define chyme

A soupy liquid made of a mixture of *gastric juice* and partially digested food.

When fat is present in the intestine, the gallbladder contracts to squirt bile into the intestine to emulsify the fat. How does the gallbladder get the message that fat is present?

Fat in the intestine stimulates cells of the intestinal wall to release the hormone cholecystokinin (CCK). This hormone travels by way of the blood to the gallbladder and stimulates it to contract, which releases bile into the small intestine. Cholecystokinin also travels to the pancreas and stimulates it to secrete its juices, which releases bicarbonate and enzymes into the small intestine. Once the fat in the intestine is emulsified and enzymes have begun to work on it, the fat no longer provokes release of the hormone, and the message to contract is canceled. (By the way, fat emulsification can continue even after a diseased gallbladder has been surgically removed because the liver can deliver bile directly to the small intestine.)

Classify carbohydrates as monosaccharides, disaccharides, oligosaccharides or polysaccharides.

Monosaccharides- single sugars such as glucose, fructose, and galactose Disaccharides- pairs of monosaccharides such as maltose, sucrose, and lactose Polysaccharides- large molecules (most dietary fibers, starch)

Name the six major classes of nutrients and identify which are organic

Macronutrients: -Carbohydrates (organic, energy-yielding) -Lipids (organic, energy-yielding) -Proteins (organic, energy-yielding) Micronutrients: -Vitamins (organic, NOT energy-yielding) -Minerals (inorganic, NOT energy-yielding) Other: -Water (inorganic, NOT energy-yielding)

Identify the energy-providing nutrients and calculate the energy available from foods.

Macronutrients: Carbohydrates-4kcal Protein-4kcal Fat-9kcal Other: Alcohol-7kcal

Define essential nutrients

Must consume through our diets (food) e.g. Vitamin D

Explain the mechanical processes of digestion in order of occurrence in the digestive tract.

Peristalsis pushes the digestive controls along. Stomach action involves circular, longitudinal, and diagonal muscles. Segmentation is contractions by circular muscles that contract and squeeze contents to promote mixing with digestive juices. Sphincter contractions open and close passageways. This prevents reflux and controls the passage of contents.

fermentable fiber

Type of fiber that enters the large colon undigested, where it is acted on by the bacteria of the gut. Formerly called insoluble fiber.

viscous fiber

Types of fiber characterized by their ability to form a gel solution when combined with liquid. Formerly called soluble fiber.

Describe the anatomy of the absorptive system

Villi are the fingerlike projections within the folds of the small intestine that move in a wave-like pattern to trap nutrients. Microvilli are the microscopic hairlike projections on each villi. Crypts are the tubular glands that lie between the intestinal villi. Goblet cells are located between the villi and secrete a protective thick mucus.

gastric juice contains

hydrochloric acid, pepsin, gastric lipase, intrinsic factor

Define microvilli

increase a cell's surface area for absorption

List the accessory organs and their secretions which assist in the breakdown of food.

1. Saliva- Salivary glands moistens food 2. Gastric Juice-Gastric glands secrete mucus to protect the walls of the stomach 3. Pancreatic Juice- contains intestinal enzymes and bicarbonate 4.Bile-produced by the liver, stored in the gall bladder, and acts as an emulsifier to suspend fat. 5. Small Intestine - enzymes on surface of small intestine finish digestion and is now ready to be absorbed.

List the enzymes used in the digestion of carbohydrates.

Amylase starts to work in the mouth, hydrolyzing starch to shorter polysaccharides and to the disaccharide maltose. Maltase breaks maltose into two glucose molecules. Sucrase breaks sucrose into one glucose and one fructose molecule. Lactase breaks lactose into one glucose and one galactose molecule.

Making Ketone Bodies from Fat Fragments

An inadequate supply of carbohydrate can shift the body's energy metabolism in a precarious direction. With less carbohydrate providing glucose to meet the brain's energy needs, fat takes an alternative metabolic pathway; instead of entering the main energy pathway, fat fragments combine with one another, forming ketone bodies. Ketone bodies provide an alternative fuel source during starvation, but when their production exceeds their use, they accumulate in the blood, causing ketosis. Because most ketone bodies are acidic, ketosis disturbs the body's normal acid-base balance. To spare body protein and prevent ketosis, the body needs 50 to 100 grams of carbohydrate a day. Dietary recommendations urge people to select abundantly from carbohydrate-rich foods to provide for considerably more.

Explain the role of enzymes in the digestion of food.

As a catalyst, the enzyme itself remains unchanged. The enzymes involved in digestion facilitate a chemical reaction known as hydrolysis—the addition of water (hydro) to break (lysis) a molecule into smaller pieces. Enzymes are often identified by the organ they come from and the compounds they work on. Gastric lipase, for example, is a stomach enzyme that acts on lipids, whereas pancreatic lipase comes from the pancreas (and also works on lipids).

Bile

Bile is not an enzyme; it is an emulsifier that disperses fats in watery solutions, which gives the digestive enzymes access to them.

Carbohydrate Digestion in the stomach

Carbohydrate digestion ceases in the stomach. The activity of salivary amylase diminishes as the stomach's acid and protein-digesting enzymes inactivate the enzyme. The stomach's digestive juices contain no enzymes to break down carbohydrates. Fibers are not digested, but because they linger in the stomach, they delay gastric emptying, thereby providing a feeling of fullness and satiety. Carbohydrate digestion begins again in the small intestine.

Define cholecystokinin

Cholecystokinin is a hormone that is released in response to chyme in the duodenum. It then triggers the release of pancreatic juice from the pancreas, and bile from storage in the gallbladder.

Fat and protein take longer to digest than carbohydrate does. When fat or protein is present, intestinal motility slows to allow time for its digestion. How does the intestine know when to slow down?

Cholecystokinin is released in response to fat or protein in the small intestine. In addition to its role in fat emulsification and digestion, cholecystokinin slows GI tract motility. Slowing the digestive process helps maintain a pace that allows all reactions to reach completion. Hormonal and nervous mechanisms like these account for much of the body's ability to adapt to changing conditions.

Identify the Daily Value and DRI for fiber and methods to increase fiber in the diet.

DRI 14g per 1000 calorie diet

The stomach normally maintains a pH between 1.5 and 1.7. How does it stay that way?

Food entering the stomach stimulates cells in the stomach wall to release the hormone gastrin. Gastrin, in turn, stimulates the stomach glands to secrete the components of hydrochloric acid. When pH 1.5 is reached, the acid itself turns off the gastrin-producing cells; they stop releasing gastrin, and the glands stop producing hydrochloric acid. Thus, the system adjusts itself. Nerve receptors in the stomach wall also respond to the presence of food and stimulate the gastric glands to secrete juices and the muscles to contract. As the stomach empties, the receptors are no longer stimulated, the flow of juices slows, and the stomach quiets down.

Identify the hormones involved in digestive and absorptive processes.

Stomach has a hormone called gastrin nerve receptors respond to presence of food. as the stomach empties so the nerve cells stop responding. 1. Gastrin - Stomach 2. Secretin - hormone produced by cells in duodenum wall 3. Cholecystokinin - hormone produced by cells of intestinal walls

List the major uses of glucose in the body.

Storing Glucose as Glycogen Using Glucose for Energy Making Glucose from Protein Making Ketone Bodies from Fat Fragments Using Glucose to Make Fat

Discuss the hormones used by the body to maintain normal blood glucose concentration.

The maintenance of normal blood glucose depends on foods and hormones. When blood glucose falls below normal, food can replenish it, or in the absence of food, glucagon can signal the liver to break down glycogen stores. When blood glucose rises above normal, insulin can signal the cells to take in glucose for energy. Eating balanced meals that provide abundant carbohydrates, including fibers, and a little fat help slow down the digestion and absorption of carbohydrate so that glucose enters the blood gradually. Eating at regular intervals also helps the body maintain a balance between the extremes.

Pancreatic secretions contain a mixture of enzymes to digest carbohydrate, fat, and protein. How does the pancreas know how much of each type of enzyme to provide?

The pancreas does know what its owner has been eating, and it secretes enzyme mixtures tailored to handle the food mixtures that have been arriving recently (over the past several days). Enzyme activity changes proportionately in response to the amounts of carbohydrate, fat, and protein in the diet. If a person has been eating mostly carbohydrates, the pancreas makes and secretes mostly carbohydrases; if the person's diet has been high in fat, the pancreas produces more lipases; and so forth. Hormones from the GI tract, secreted in response to meals, keep the pancreas informed as to its digestive tasks. The day or two lag between the time a person's diet changes dramatically and the time digestion of the new diet becomes efficient explains why dietary changes can "upset digestion" and should be made gradually.

Why don't the digestive enzymes damage the pancreas?

The pancreas protects itself from harm by producing an inactive form of the enzymes.* It releases these proteins into the small intestine, where they are activated to become enzymes. In pancreatitis, the digestive enzymes become active within the infected pancreas, causing inflammation and damaging the delicate pancreatic tissues.

pancreatic juice and intestinal enzymes

The pancreatic juice contains enzymes that act on all three energy nutrients, and the cells of the intestinal wall also possess digestive enzymes on their surfaces. In addition to enzymes, the pancreatic juice contains sodium bicarbonate

Define secretin

The presence of chyme stimulates the cells of the duodenual wall to release the hormone secretin into the blood. When secretin reaches the pancreas, it stimulates the pancreas to release its bicarbonate-rich juices. Thus, whenever the duodenum signals that acidic chyme is present, the pancreas responds by sending bicarbonate to neutralize it.

As the chyme enters the small intestine, the pancreas adds bicarbonate to it so that the intestinal contents always remain at a slightly alkaline pH. How does the pancreas know how much to add?

The presence of chyme stimulates the cells of the duodenual wall to release the hormone secretin into the blood. When secretin reaches the pancreas, it stimulates the pancreas to release its bicarbonate-rich juices. Thus, whenever the duodenum signals that acidic chyme is present, the pancreas responds by sending bicarbonate to neutralize it. When the need has been met, the cells of the duodenal wall are no longer stimulated to release secretin, the hormone no longer flows through the blood, and the pancreas no longer receives the message and stops sending pancreatic juice. Nerves also regulate pancreatic secretions.

Carbohydrate Digestion in the mouth

The salivary enzyme amylase starts to work in the mouth, hydrolyzing starch to shorter polysaccharides and to the disaccharide maltose. In fact, you can taste the change if you chew a piece of starchy food like a cracker and hold it in your mouth for a few minutes without swallowing it—the cracker begins tasting sweeter as the enzyme acts on it. Because food is in the mouth for a relatively short time, very little carbohydrate digestion takes place there.

Carbohydrate Digestion in the small intestine

The small intestine performs most of the work of carbohydrate digestion. A major carbohydrate-digesting enzyme, pancreatic amylase, enters the intestine via the pancreatic duct and continues breaking down the polysaccharides to shorter glucose chains and maltose. The final step takes place on the outer membranes of the intestinal cells. There specific enzymes break down specific disaccharides: -Maltase breaks maltose into two glucose molecules. -Sucrase breaks sucrose into one glucose and one fructose molecule. -Lactase breaks lactose into one glucose and one galactose molecule. At this point, all polysaccharides and disaccharides have been broken down to monosaccharides—mostly glucose molecules, with some fructose and galactose molecules as well.

The pyloric sphincter opens to let out a little chyme, then closes again. How does it know when to open and close?

When the pyloric sphincter relaxes, acidic chyme slips through. The cells of the pyloric muscle on the intestinal side sense the acid, causing the pyloric sphincter to close tightly. Only after the chyme has been neutralized by pancreatic bicarbonate and the juices surrounding the pyloric sphincter have become alkaline can the muscle relax again. This process ensures that the chyme will be released slowly enough to be neutralized as it flows through the small intestine. This is important because the small intestine has less of a mucous coating than the stomach does and so is not as well protected from acid.

Carbohydrate Digestion in the large intestine

Within 1 to 4 hours after a meal, all the sugars and most of the starches have been digested. Only the nondigestible carbohydrates remain in the digestive tract.

Describe lactose intolerance.

a condition that results from the inability to digest the milk sugar lactose; characterized by bloating, gas, abdominal discomfort, and diarrhea. Lactose intolerance differs from milk allergy, which is caused by an immune reaction to the protein in milk.

Define nutrient density

a formula designed to help the consumer figure out how much energy and nutrition a food or drink provides his or her body

Insulin

a hormone secreted by special cells in the pancreas in response to (among other things) elevated blood glucose concentration. Insulin controls the transport of glucose from the bloodstream into the muscle and fat cells.

glucagon

a hormone secreted by special cells in the pancreas in response to low blood glucose concentration. Glucagon elicits release of glucose from liver glycogen stores.

Define gastrin

a hormone that stimulates secretion of gastric juice, and is secreted into the bloodstream by the stomach wall in response to the presence of food.

Define energy density

a measure of the energy (calories) a food provides relative to the amount of food; should eat more low energy-dense foods than high

Define kilocalorie

a unit of energy of 1,000 calories

Define villi

any of numerous minute elongated projections set closely together on a surface, typically increasing its surface area for the absorption of substances, in particular.

insoluble fiber

benefit GI health

soluble fiber

benefit heart disease, diabetes, cancers, and weight management

Define segmentation

churning of bolus

List the segments of the digestive tract in order from the mouth to the colon.

mouth esophagus stomach pyloric sphincter duodenum jejunum ilium ileocecal valve ascending colon transverse colon descending colon sigmoid colon rectum anus

mouth secretions

salivary amylase The saliva contains water, salts, mucus, and enzymes that initiate the digestion of carbohydrates.

Describe the 4 types of absorption that occur.

simple diffusion: Some nutrients such as water and small lipids are absorbed by simple diffusion. They cross into intestinal cells freely. facilitated diffusion: Some nutrients such as the water-soluble vitamins are absorbed by facilitated diffusion. They need a specific carrier to transport them from one side of the cell membrane to the other. Alternatively, facilitated diffusion may occur when the carrier changes the cell membrane in such a way that the nutrients can pass through. active diffusion: Some nutrients such as glucose and amino acids must be absorbed actively. These nutrients move against a concentration gradient, which requires energy.

Define energy yielding nutrients

the nutrients that break down to yield energy the body can use: carbohydrate, fat, protein

Define peristalsis

wavelike movement that propels the food through the digestive system.

Describe the major types of diabetes (Type 1, Type 2); how they develop, how they differ, and how they are treated

• Type 1 diabetes is the less common type with no insulin produced (b/c immune system destroys beta cells of the pancreas). Usually beings in childhood or early adulthood. Requires insulin Common symptoms: polydipsia (increased thirst), polyuria (increased urination), polyphagia (increased hunger) • Type diabetes 2 is the more common type where fat cells resist insulin. o Associated with obesity, hereditary, & aging o 90-95% of diabetics o Cells are resistant to insulin o (Pre-diabetes: impaired glucose tolerance, fasting blood sugar between 100-126mg/dl, & high risk of developing diabetes) • Gestational Diabetes is pregnant women who have never had diabetes before but have higher blood sugar (glucose) levels during pregnancy.