Nutrition: Carbohydrates

What happens when blood glucose levels increase?

* When blood glucose levels INCREASE, pancreas releases more insulin. Insulin lowers blood glucose by facilitating the uptake of glucose into many kinds of cells * When there is more blood glucose than necessary, insulin stores it as glycogen * Once muscles and liver reach their glycogen storage max., excess glucose is converted into fat.

Glycosidic Bond:

A condensation reaction chemically joins monosaccharides together by a glycosidic bond. The hydroxyl group (-OH) from one monosaccharide interacts with a hydrogen group (-H) of another monosaccharide, resulting in the loss of one water molecule.

Soluble dietary fiber:

tends to dissolve or swell in water. Readily broken down by bacteria in the colon.

Glucose:

the most abundant monosaccharide in the body. Its primary function is to provide cells a source of energy (ATP).

Glycogenesis:

the process that insulin stimulates in order to store excess glucose as glycogen.

Starch Digestion:

Begins in the mouth. Salivary glands release the enzyme salivary (alpha) amylase and create DEXTRINS. Dextrins enter the stomach, leave unchanged, and go into the small intestine where they encounter pancreatic (alpha) amylase. Transforms the dextrins into the disaccharide MALTOSE. Maltose finishes the digestion by hydrolyzing the last remaining chemical bond in maltose, resulting in two glucose molecules. DIGESTION IS ENTIRELY IN SMALL INTESTINE.

How do hormones regulate blood glucose and energy storage?

Blood glucose fluctuates throughout the day, depending on when/what you eat. Cells need energy 24/7 so pancreatic hormones insulin and glucagon work to maintain blood glucose levels

Galactose:

Body uses galactose to make certain components of cell membranes and synthesize lactose. The majority of galactose is converted to glucose and used as a source of energy.

What type of carbohydrates supply energy and nutrients/fiber that the body needs?

Complex

Diverticular Disease

Condition of the large intestine. Chronic constipation can cause areas along the colon wall to become weak, and as a result, protruding pouches (diverticula) can form. Affects 50% of adults by the age of 70.

Complex Carbohydrates:

Consist of many monosaccharides bonded together in a variety of arrangements. Includes oligosaccharides and polysaccharides

Disaccharides:

Consist of two monosaccharides bonded together. The most common are lactose (galactose and glucose), maltose (glucose and glucose), and sucrose (fructose and glucose).

How does dietary fiber help prevent Diverticulitis?

Dietary fiber helps prevent the formation of diverticula by increasing fecal mass, making bowel movements easier.

How are Carbohydrates digested, absorbed, and circulated in the body?

Digestive enzymes break down the glycosidic bonds that hold disaccharides and starches together. Ultimate goal of carbohydrate digestion is to break down large, complex molecules into small, absorbable monosaccharides. This process requires a series of enzymes produced in the salivary glands, pancreas, and small intestine.

Fasting HYPOglycemia:

Not associated with eating. Occurs when the pancreas releases too much insulin, even when food has not been consumed. Caused by pancreatic tumors, medications, illnesses, etc.

Functions of Monosaccharides:

Once absorbed, monosaccharides circulate directly to the liver, where the majority of galactose and fructose is converted into other compounds (usually glucose). MOST IMPORTANT ROLE: ability to transform the energy contained in glucose into ATP

How is Glucose produced?

Photosynthesis

Carbohydrates come mainly from what type of sources?

Plant

Oligosaccharides:

Present in foods like dried beans, soybeans, peas, and lentils. Oligosaccharides are components of cell membranes and allow cells to recognize and interact with each other.

Insoluble dietary fiber:

Remains relatively unchanged. Most abundant insoluble dietary fiber in food is cellulose (ex. whole grain flour, wheat bran, whole grain cereal, seeds, veggies). Insoluble fiber can help alleviate constipation

What type of carbohydrates are quick energy sources but do not supply nutrients or fiber?

Simple

Monosaccharides:

Single-sugar molecules made up of carbon, hydrogen, and oxygen atoms

Three most common polysaccharides:

Starch, glycogen, and dietary fiber

What is commonly known as table sugar?

Sucrose

What forms are carbohydrates taken in?

Sucrose, lactose, maltose, fructose, and starch/glycogen

What is the major kind of simple sugar, and is the basic source of energy for all living things?

Sucrose/glucose

What happens after disaccharide and starch digestion is complete?

The resulting monosaccharides (glucose, galactose, and fructose) are readily absorbed from small intestine into blood.

Reactive HYPOglycemia:

When the pancreas over-responds to high blood glucose levels following the consumption of food. Release of too much insulin results in very low blood glucose.

What is known as milk sugar?

lactose

Fructose:

naturally occurring monosaccharide found primarily in honey, fruits, and veggies. Majority comes from foods made with high-fructose corn syrup.

What is a Carbohydrate?

An organic compound made up of one or more sugar molecules.

How many monosaccharides does Poly have?

10+

How many monosaccharides does Oligo have?

3-10

What percent of carbohydrates should our food be?

45-65%

Fiber:

A diverse group of plant polysaccharides that cannot be digested in the small intestine. Undigested fiber passes to the large intestine, where intestinal bacteria breaks it down producing gas and more. Dietary fiber promotes selective growth of beneficial intestinal bacteria, which helps inhibit growth of other, disease-causing bacteria

Glycemic index (GI):

A rating system based on a scale of 0-100 that can be used to compare the glycemic response of various foods. 50g of pure glucose will produce a value of 100, so foods that are similar to that are considered high GI foods. Limitation: the amount of carbohydrate found in a typical serving of food is not taken into account. Rather, GI values are based on a standard amount of carbohydrate (50g), which may or may not represent the amount a person would normally eat. Response: glycemic load (GL)

Glycemic Load (GL):

A rating system used to categorize the body's glycemic response to foods that takes into account the glycemic index (GI) as well as the amount of carbohydrate typically found in a single serving of that food

HYPOglycemia:

Abnormally low level of blood glucose

Lactose:

Abundant carbohydrate in milk, and is the only disaccharide that has a BETA glycosidic bond between the monosaccharides

How insulin promotes energy storage:

After a meal more glucose may be available than needed. Body stores the excess energy contained in glucose for later use. Insulin promotes the storage of excess energy from glucose in the form of glycogen and body fat. It also stimulates protein synthesis and inhibits the breakdown of muscle.

What are the two forms of starch?

Amylose and amylopectin. Both consist entirely of glucose molecules; only difference is the arrangement.

Diverticulitis:

Diverticula that have become infected or inflamed. Symptoms: cramping, diarrhea, fever, and possible bleeding from rectum.

How is GL calculated?

Dividing the glycemic index (GI) of a food by 100, and then multiplying it by the grams of carbohydrates in one serving.

What does carbohydrates supply?

Energy (glucose)

What in the body break down simple sugars?

Enzymes

Alpha bond:

Faces down

Beta bond:

Faces up

Dietary fiber:

Fiber that occurs naturally in plants. Found in a variety of plant foods (ex. whole grain, legumes, veggies, fruits.) Different foods contain different types of D.F. Fiber is often classified according to its solubility in water.

Maltose:

Formed during starch digestion. Not common in food, but important for the production of beer

Sucrose:

Found in many plants, and is especially abundant in sugar cane and sugar beet

What is known as fruit sugar?

Fructose

How can I ensure adequate fiber intake?

Fruits, veggies, and foods made from whole grain. Nutritional value of grains is greatest when all three components (bran, germ, and endosperm) are all present. BRAN: contains most of the fiber. GERM: supplies vitamins/minerals. ENDOSPERM: mostly starch

What is known as blood sugar?

Glucose

How insulin lowers blood glucose:

Glucose enters cells via facilitated diffusion, meditated by carrier proteins known as glucose transporters (some of these require insulin to transport glucose across cell membrane, others do not.) After a person eats carb-containing food, blood glucose levels rise, causing pancreas to release more insulin. When insulin encounters cells with insulin responsive glucose transporters, it binds to insulin receptors on the surface of cell membranes. This allows glucose to enter the cell.

Three most common monosaccharides:

Glucose, fructose, galactose (each contains SIX carbon atoms)

If more carbohydrates are eaten than what is needed for energy, the unused portion is stored in the liver/tissues as what?

Glycogen

What is the richest source of starchy foods?

Grains - nearly 70% of their weight is starch

Lactose intolerance:

Inability to digest lactose, caused by a lack of the enzyme lactase. When they consume lactose, it enters the large intestine undigested. Bacteria break down the lactose, producing several by-products, including gas.

HYPERglycemia:

Insulin-responsive glucose transporters have difficulty transporting glucose across cell membranes, causing glucose to accumulate in the blood. A person has impaired glucose regulation, or sometimes diabetes.

Amylose:

Linear (unbranched) chain of glucose molecules held together by an (alpha) 1,4 glycosidic bond

Polysaccharides:

Made of many monosaccharides bonded together by glycosidic bonds.

What is known as malt sugar?

Maltose

Carbohydrates play an important part in what process?

Metabolic, and of the synthesis and energy production of protein and fat

Simple Carbohydrates:

Monosaccharides and disaccharides (because of their small size)

Fiber:

Not a required dietary component, but is an important part of a healthful diet

Glycogen:

The body stores small amounts of glucose in the form of glycogen. Many tissues store small amounts, but majority is found in the liver and skeletal muscles. Highly branched arrangement of glucose molecules--branch points in glycogen provide an advantage b/c enzymes can hydrolyze multiple glycosidic bonds simultaneously. Therefore, glycogen can be broken down quickly when energy is needed. * Body turns to glycogen when glucose availability is low. When liver glycogen is broken down, the glucose is released directly into blood. But muscle lacks enzyme needed to release glucose into the blood, so instead, that glucose is used to fuel physical activity

Glycemic response:

The change in blood glucose following the ingestion of a specific food

Photosynthesis:

The process through which plants synthesize glucose. To store this important source of energy, plants convert glucose to starch.

What happens when blood glucose levels decrease?

To increase glucose availability, glucagon stimulates the breakdown of glycogen stored in the liver.

Amylopectin:

highly branched arrangement of glucose molecules. alpha 1,4 glycosidic bond (linear portions), as well as (alpha) 1,6 glycosidic bonds (branch points)