Chapter 4 - The Carbohydrates, Sugars, Starches and Fibers Flashcards

1
Q

Carbohydrate

A

Compounds composed of carbon, oxygen and hydrogen arranged as monosaccharides or multiples of monosaccharides. Most, but not all, carbohydrates have a ratio of one carbon molecule to one water molecule.

Carbo = carbon ( c), hydrate = with water (H2O)

All plant foods—whole grains, vegetables, legumes, and fruits—provide ample carbohydrate.

Our bodies receive glucose from carbs for immediate energy use and convert some glucose into glycogen for reserve energy.

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2
Q

Chemistry of Carbs

A

The dietary carbohydrate family includes:

  • Monosaccharides: single sugars
  • Disaccharides: sugars composed of pairs of monosaccharides
  • Polysaccharides: large molecules composed of chains of monosaccharides

Monosaccharides and disaccharides (the sugars) are sometimes called simple carbohydrates, and polysaccharides (starches and fibers) are sometimes called complex carbohydrates.

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3
Q

Monosaccharide

A

Simple sugars. C6H12O6

These are simple carbohydrates. All have the same number and kinds of atoms. These differ in their arrangements of atoms, and the chemical differences account for the differing sweetness of each.

Mono = one Saccharides = sugar.

The most important sugars in nutrition:

Glucose
Fructose
Galactose

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4
Q

Glucose

A

Provides nearly all the energy the human brain uses daily.

Monosaccharide. Sometimes known as blood sugar in the body or dextrose in Foods.

Serves as an essential energy source for all the body’s activities. Significance to nutrition is tremendous.

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5
Q

Fructose

A

Monosaccharide. Intensely sweet. Sweetest of the sugars.

The arrangement of the atoms stimulates the taste buds on the tongue to produce sweet sensations.

Naturally in fruit and honey. Other sources include soft drinks, desserts, and high fructose corn syrup.

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6
Q

Galactose

A

Monosaccharide. Occurs naturally on foods as a simple sugar only in very small amounts.

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7
Q

Disaccharide

A

Pairs of three monosaccharides linked together. Glucose occurs in all three. The second member of the pair is fructose, galactose, or another glucose.

Whitney, Eleanor Noss; Rolfes, Sharon Rady. Understanding Nutrition (p. 98). Cengage Textbook. Kindle Edition.

Di = two.

These carbohydrates are put together and taken apart by condensation and hydrolysis

  • Maltose (glucose + glucose)
  • Sucrose (glucose + fructose)
  • Lactose (glucose + galactose)
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8
Q

Condensation

A

To make a disaccharide.

Links two monosaccharides together.

A hydroxyl (OH) group from one monosaccharide and a hydrogen atom (H) from the other combine to create a molecule of water (H2O). The two originally separate monosaccharides link together with single oxygen (O).

In this chemical reaction, water is released and two molecules combine to form one larger product

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9
Q

Hydrolysis

A

A chemical reaction in which one molecule is split into two molecules, with hydrogen (H) added to one and a hydroxyl group (OH) to the other.

Hydro = water and lysis = breaking.

To break a disaccharide in two this chemical reaction occurs.

A molecule of water (H2O) splits to provide the H and OH needed to complete the resulting monosaccharide.

Commonly occurs during digestion.

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10
Q

Maltose

A

Disaccharide.

Composed of two glucose units.

Sometimes known as malt sugar. Produce whenever starch breaks down – in human digestion and the fermentation of alcohol. Only a minor part of a few foods including barley.

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11
Q

Sucrose

A

Disaccharide.

Composed of glucose and fructose.

Commonly known as table sugar, beet sugar or cane sugar. Also occurs in many fruits, some vegetables and grains.

Sweetest of the disaccharides because it contains fructose.

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12
Q

Lactose

A

Disaccharide.

Combination of galactose and glucose.

Principle carbohydrate of milk. Known as milk sugar.

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13
Q

Polysaccharide

A

Slightly more complex, containing many glucose units and, in some cases, a few other monosaccharides strung together.

Three types are important to nutrition: glycogen, starches, and fibers.

Glycogen is a storage form of energy in the body; starch is the storage form of energy in plants; and fibers provide structure in stems, trunks, roots, leaves, and skins of plants.

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14
Q

Glycogen

A

Polysaccharide.

An important storage form of energy in the body. Built of glucose units.

Found to only a limited extent in meats and not at all in plants. Food is not a significant source of glycogen.

Role is storage of glucose for future use in the liver and muscles. When our body sends hormonal messages to “release energy” enzymes respond by attacking the many branches of glycogen making a surge of glucose available

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15
Q

Starch

A

Polysaccharide.

Storage form of energy in plants.

Built of glucose units. Long, branched or unbranched chains of hundreds or thousands of glucose molecules linked together. Giant starch molecules are packed side by side in grains such as wheat or rice, in root crops and tubers such as yams and potatoes, and in legumes such as peas and beans.

When humans eat a plant, the body hydrolyzes the starch to glucose and uses the glucose for energy. Grains are the richest food source of starch.

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16
Q

Fibers

A

Polysaccharide.

The structural parts of plants and thus are found in all plant-derived foods—vegetables, fruits, whole grains, and legumes.

Composed of a variety of monosaccharides and other carbohydrate derivatives.

The bonds between their monosaccharides cannot be broken down by digestive enzymes in the body.

Because dietary fibers pass through the body undigested, they contribute no monosaccharides, and therefore little or no energy.

Researchers often sort dietary fibers into two groups according to their solubility; soluble and insoluble.

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17
Q

Soluble fibers

A

Dissolve in water, form gels (viscous) and are easily digested by bacteria in the colon (fermentable)

Commonly found in oats, barley, legumes, and citrus fruits, soluble fibers are most often associated with protecting against heart disease and diabetes by lowering blood cholesterol and glucose levels,

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18
Q

Insoluble fiber

A

Does not dissolve in water, do not form gels (non-viscous) and are less readily fermented.

Found mostly in whole grains (bran) and vegetables, insoluble fibers promote bowel movements, alleviate constipation, and prevent diverticular disease.

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19
Q

Functional fibers

A

added to foods or used in supplements

20
Q

Resistant starches

A

Escape digestion and absorption in the small intestine and classified as dietary fiber

21
Q

Lignin

A

Indigestible substances are found in woody parts of vegetables such as carrots and broccoli. It is a non-polysaccharide form of fiber or non-carbohydrate. Research suggests potential to prevent disease caused by the overproduction of radicals

22
Q

Phytic acid

A

Not a dietary fiber, but often found in fiber-rich foods.

A nonnutrient component of plant seeds; also called phytate (FYE-tate).

Phytic acid occurs in the husks of grains, legumes, and seeds and is capable of binding minerals such as zinc, iron, calcium, magnesium, and copper in insoluble complexes in the intestine, which the body excretes unused.

23
Q

Digestion and absorption of carbs

A

Break into small molecules - chiefly glucose - for the body to absorb and use.

The large starch molecules require extensive breakdown; the disaccharides need only be broken once and the monosaccharides not at all.

When a person eats foods containing starch, enzymes hydrolyze the long chains to shorter chains, the short chains to disaccharides, and, finally, the disaccharides to monosaccharides. This process begins in the mouth.

24
Q

The mouth - carb digestion

A

The salivary enzyme amylase starts to work, hydrolyzing starch to shorter polysaccharides and to the disaccharide maltose.

25
Q

Stomach - carb digestion

A

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

26
Q

The small intestine - carb digestion

A

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

27
Q

Large intestine - carb digestion

A

Only the fibers remain in the digestive tract. Fibers in the large intestine attract water, which softens the stools for passage.

28
Q

Carbohydrate absorption

A

Glucose is unique in that it can be absorbed to some extent through the lining of the mouth, but for the most part, nutrient absorption takes place in the small intestine.

Glucose and galactose enter the cells lining the small intestine by active transport; fructose is absorbed by facilitated diffusion.

As the blood from the small intestine circulates through the liver, cells there take up fructose and galactose and most often convert them to compounds within the same metabolic pathways as glucose.

29
Q

Lactose intolerance

A

A condition that results from the inability to digest the milk sugar lactose.

Symptoms include bloating, gas, abdominal discomfort and diarrhea.

Normally, the intestine cells produce enough of the enzyme lactose to ensure that the disaccharide lactose is digested and absorbed. Lactase activity is greatest after birth when infants rely on their mother’s milk and steadily declines into adulthood. Only a small percentage (about 30%) retain enough lactose to effectively digest and absorb lactose.

Differs from a milk allergy that is caused by an immune reaction to the protein in milk.

Managing lactose intolerance requires some dietary changes, although total elimination of milk products usually is not necessary as it contains important nutrients and minerals like calcium, vitamin D and B vitamin riboflavin.

30
Q

Gluconeogenesis

A

When a person does not replenish glucose by eating carbs protein can be broken down to glucose to fuel the brain and other special cells.

The making of glucose from a noncarbohydrate source.

31
Q

Protein-sparing action

A

The action of carbohydrate (and fat) in providing energy that allows the protein to be used for other purposes.

32
Q

Storing glucose as Glycogen

A

Glycogen After a meal, blood glucose rises, and liver cells link excess glucose molecules by condensation reactions into long, branching chains of glycogen.

When blood glucose falls, the liver cells break down glycogen by hydrolysis reactions into single molecules of glucose and release them into the bloodstream.

The liver stores about one-third of the body’s total glycogen and releases glucose into the bloodstream as needed.

Muscle cells can also store glucose as glycogen (the other two-thirds), but muscles hoard most of their supply, using it just for themselves during exercise.

The brain maintains a small amount of glycogen, which is thought to provide an emergency energy reserve during times of severe glucose deprivation.

Glycogen holds water and, therefore, is rather bulky. The body can store only enough glycogen to provide energy for relatively short periods of time—less than a day during rest and a few hours at most during exercise.

For its long-term energy reserves, for use over days or weeks of food deprivation, the body uses its abundant, water-free fuel, fat.

33
Q

Insulin

A

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 muscles and fat cells

34
Q

Epinephrine

A

Another hormone that signals the liver cells to release glucose is the “fight or-flight” hormone.

When a person experiences stress, epinephrine acts quickly to ensure that all the body cells have energy fuel in emergencies. Among its many roles in the body, epinephrine works to release glucose from liver glycogen to the blood.

35
Q

Homeostasis

A

The bodies tendency to regulate internal systems to be a state of balance. For example, the body must maintain blood glucose within certain limits to nourish cells properly. This is regulated by two hormones: insulin and glucagon. Insulin moves glucose from the blood into the cells. Glucagon brings glucose out of storage when needed. After a meal blood glucose rises and insulin is secreted to usher glucose into cells. Most take what they need except the liver and muscles can assemble glucose into long, branching chains for storage. The over can convert extra glucose to fat. This process brings elevated blood glucose levels down to normal levels. When blood glucose falls specialized cells on the pancreas release glucagon onto the blood that signals the lover to break down glycogen stores and release glucose into the blood system. This system allows the body to keep blood glucose levels in homeostasis.

36
Q

Using glucose for energy

A

Glucose fuels the work of most of the body’s cells. Inside a cell, a series of reactions can break glucose into smaller compounds that yield energy when broken down completely to carbon dioxide and water.

37
Q

Glucose and glycogen

A

These two carbohydrates - glucose and its storage form glycogen - provide about half of all the energy muscles and other body tissues use. The other half of the body’s energy comes mostly from fat.

38
Q

Glucose to make fat

A

After meeting its immediate energy needs and filling its glycogen stores to capacity, the body must find a way to handle any extra glucose.

When glucose is abundant, energy metabolism shifts to use more glucose instead of fat. If that isn’t enough to restore glucose balance, the liver breaks glucose into smaller molecules and puts them together into the more permanent energy-storage compound—fat.

Fat cells can store seemingly unlimited quantities of fat.

39
Q

Cellulose

A

Non-starch polysaccharide. Dietary fiber that can also be a functional fiber when consumed as s supplement to alleviate constipation.

40
Q

Hemicelluloses

A

Non-starch polysaccharide. Non digestible and present in plants cell walls. It is a dietary fiber that is either soluble or insoluble.

41
Q

Ketosis

A

An undesirable high concentration of ketone bodies in the blood and urine.

With less carbohydrate consumption for energy fats can be used as an alternative metabolic pathway.

Fat fragments combine with one another forming ketone bodies that provide an alternate food source during starvation, but their production exceeds their use and they accumulate in the blood stream causing ketosis.

Ketones are acidic and the accumulation disrupts the acid-base balance in the body.

42
Q

Hypoglycemia

A

blood glucose drop below normal

experience the symptoms of hypoglycemia: weakness, rapid heartbeat, sweating, anxiety, hunger, and trembling. Most commonly, hypoglycemia is a consequence of poorly managed diabetes: too much insulin, strenuous physical activity, inadequate food intake, or illness that causes blood glucose levels to plummet. Hypoglycemia in healthy people is rare.

43
Q

Ketone bodies

A

Provide an alternate 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.

44
Q

Diabetes

A

Insulin is either inadequate or ineffective.

A chronic disorder of carbohydrate metabolism.

In type 1 diabetes, the less common type, the pancreas fails to produce insulin. - genetic, varial after effects

In type 2 diabetes, the more common type of diabetes, the cells fail to respond to insulin. This condition tends to occur as a consequence of obesity.

When blood glucose levels are higher than normal, but below the diagnosis of diabetes, the condition is called prediabetes.

45
Q

Making ketone bodies from fat fragments

A

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.

46
Q

Glycemic Index

A

A method of classifying foods according to their potential for raising blood glucose.

47
Q

Glycemic response

A

Refers to how quickly glucose is absorbed after a person eats, how high blood glucose rises, and how quickly it returns to normal. Slow absorption, a modest rise in blood glucose, and a smooth return to normal are desirable (a low glycemic response).