Glycogen

Glycogen is the principal storage form of glucose in animal cells. In humans, the most glycogen is found in the liver (10% of the liver mass), whereas muscles only contain a relatively low amount of glycogen (1% of the muscle mass). In addition, small amounts of glycogen are found in certain glial cells in the brain.

Sometimes called “animal starch” for its resemblance with starch found in plants, it is stored in liver and muscle cells and can be converted to glucose if needed. In the liver this conversion is regulated by the hormone glucagon. Under certain conditions, between meals for instance, liver glycogen is an important source of blood glucose. Muscle cell glycogen appears to be only for local use. Glycogen is the primary glucose (energy) storage mechanism. It is stored in the form of granules in the cytosol which is where glycolysis takes place. These granules contain both glycogen and the necessary enzymes for its conversion into glucose.

Glycogen is a highly branched glucose polymer. It is formed of small chains of 8 to 12 glucose molecules linked together with &alpha (14) bonds. These small chains are in turn linked together with &alpha (16) bonds. A single molecule of glycogen can be made of up to 120,000 molecules of glucose. It is generated from glucose by the enzyme glycogen synthase. This process is called glycogenesis. The addition of a glucose molecule to glycogen takes two high energy bonds: one from ATP and one from UTP. Its breakdown into glucose, called glycogenolysis, is mediated by the enzyme glycogen phosphorylase. It’s highly branched.

Glycogen is a quick storage vehicle for the body to keep large amounts of glucose when it is not needed by the body. It is classed as a polysaccharide. Although much like amylopectin, glycogen contains more branched chains and has a higher molecular weight. It is stored in both the liver and muscles, but the liver store is more readily available for energy and blood sugar level maintenance, while the muscle store is mostly used for muscle fuel.

Glycogen stores of readily available glucose to supply the tissues with an oxidizable energy source are found principally in the liver, as glycogen. A second major source of stored glucose is the glycogen of skeletal muscle. However, muscle glycogen is not generally available to other tissues, because muscle lacks the enzyme glucose-6-phosphatase.

The major site of daily glucose consumption (75%) is the brain via aerobic pathways. Most of the remainder is utilized by erythrocytes, skeletal muscle, and heart muscle. The body obtains glucose either directly from the diet or from amino acids and lactate via gluconeogenesis. Glucose obtained from these two primary sources either remains soluble in the body fluids or is stored in a polymeric form, glycogen. Glycogen is considered the principal storage form of glucose and is found mainly in liver and muscle, with kidney and intestines adding minor storage sites. With up to 10% of its weight as glycogen, the liver has the highest specific content of any body tissue. Muscle has a much lower amount of glycogen per unit mass of tissue, but since the total mass of muscle is so much greater than that of liver, total glycogen stored in muscle is about twice that of liver. Stores of glycogen in the liver are considered the main buffer of blood glucose levels.

 
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116 terms

Lch50

Chapter 4

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Which of the following is not a monosaccharide?
A) Galactose
B) Fructose
C) Lactose
D) Glucose
C – Lactose
Major fructose sources include
A) milk and cheese.
B) fruits and honey.
C) fruits and vegetables.
D) breads and cereals.
B – fruits and honey
Simple sugars in large quantities have been shown to
A) cause obesity.
B) promote tooth decay.
C) cause diabetes mellitus.
D) cause hyperactivity.
B – promote tooth decay
The process that plants use to make glucose from carbon dioxide and water in the presence of the sun’s heat and light is called
A) biosynthesis.
B) anabolism.
C) photosynthesis.
D) glycogenesis.
C – photosynthesis
What is the major monosaccharide found in the body?
A) Glucose
B) Fructose
C) Galactose
D) Sucrose
A – Glucose
Glucose also is known as
A) levulose.
B) ribose.
C) maltose.
D) dextrose.
D – dextrose
Which of the following is not a Metabolic Syndrome risk indicator?
A) High blood pressure
B) High HDL cholesterol
C) Elevated glucose
D) Elevated triglycerides
B – High HDL cholesterol
Of the following, which is a major source of sucrose?
A) Alcohol
B) Fruits
C) Grains
D) Sugar cane
D – sugar cane
Which of the following is true about carbohydrate digestion?
A) Carbohydrate digestion is assisted by cooking, which softens tough skins.
B) Carbohydrate digestion begins in the stomach.
C) Chewing food does not assist in carbohydrate digestion.
D) Saliva production does not influence starch digestion.
A – Carb digestion is assisted by cooking, which softens tough skins
What enzyme is responsible for carbohydrate digestion in the small intestine?
A) Salivary amylase
B) Bicarbonate
C) Pancreatic proteases
D) Pancreatic amylase
D – Pancreatic amylase
Amylase is
A) an enzyme that digests protein.
B) a branched chain of glucose units.
C) an enzyme that digests starch.
D) a straight chain of glucose units.
C – an enzyme that digests starch
Which of the following shows the process of starch digestion?
A) Starch to lactose to galactose
B) Starch to maltose to glucose
C) Starch to glycogen to glucose
D) Starch to sucrose to fructose
B – starch to maltose to glucose
Glucose is absorbed via ______ absorption.
A) passive
B) facilitated
C) active
D) participatory
C – active
Lactose intolerance is caused by
A) a milk allergy.
B) lactase deficiency.
C) milk bacteria.
D) intestinal bacteria.
B – lactase deficiency
The major symptoms of lactose intolerance are
A) gas, abdominal pain, and distention.
B) a rash, sneezing, and stuffy nose.
C) a headache and chest pain.
D) nausea and vomiting.
A – gas, abdominal pain, distention
The main function of glucose is to
A) serve as raw material to build tissue.
B) work with enzymes to carry out chemical reactions.
C) repair tissue.
D) supply energy.
D – supply energy
Which organ will first receive sugars after they are absorbed into the blood?
A) Kidney
B) Heart
C) Liver
D) Pancreas
C – liver
Which of the following hormones corrects a hyperglycemic state?
A) Insulin
B) Epinephrine
C) Cortisol
D) Glucagon
A – insulin
When insulin is released, it causes
A) the liver to break down glycogen and release glucose into the blood.
B) muscle and fat cells to increase glucose uptake.
C) fat breakdown in fat tissue.
D) the liver to make glycogen from protein.
B – muscle and fat cells to increase glucose uptake
Which of the following hormones is released to correct a hypoglycemic state?
A) Insulin
B) Testosterone
C) Estrogen
D) Glucagon
D – Glucagon
Which of the following hormones is released during stressful times to increase blood glucose levels, making more energy available for use?
A) Insulin
B) Epinephrine
C) Glycogen
D) Progesterone
B – Epinephrine
The glycemic load takes into account the glycemic index of the food and the amount of
A) carbohydrate consumed.
B) glucose absorbed.
C) insulin released from the pancreas.
D) glycogen stored.
A – carbohydrate consumed
For which of the following is glucose most critical as an energy source?
A) Muscles
B) Brain
C) Liver
D) Heart
B – Brain
Amylose is
A) a long, straight glucose chain.
B) branched glucose chains.
C) a long, straight fatty acid chain.
D) branched amino acid chains
A – long straight glucose chain
The major storage sites for glycogen are
A) muscles and liver.
B) kidney and muscles.
C) liver and kidney.
D) liver and pancreas.
A – muscles and liver
Dietary fibers primarily are
A) polysaccharides.
B) polypeptides.
C) disaccharides.
D) monosaccharides.
A – polysaccharides
Which of the following is not true of dietary fibers?
A) They are mostly polysaccharides.
B) The bonds between sugar units cannot be broken by human digestive enzymes.
C) They cannot be absorbed by the small intestine.
D) They are absorbed in the large intestine.
D – They are absorbed in the large intestine
Which of the following is not a viscous (soluble) fiber?
A) Lignin
B) Gums
C) Pectin
D) Mucilages
A – Lignin
Viscous (soluble) fibers
A) increase stool size significantly.
B) are not readily fermented by intestinal bacteria.
C) do not dissolve in water.
D) can lower blood cholesterol.
D – can lower blood cholesterol
A reasonable and recommended goal for daily dietary fiber intake is how many grams?
A) 10 to 12
B) 15 to 30
C) 20 to 34
D) 25 to 38
D – 25 to 38
John Fibernugget wants to increase his fiber intake. Which of the following would be the safest way for him do this?
A) Eating enriched grains such as Rice Krispies and Saltines
B) Increasing his meat intake
C) Reading the labels of grain products and buying those labeled "wheat flour"
D) Eating more fruits and vegetables and not removing the edible peels
D – eating more fruits and vegetables and not removing the edible peels
Which of the following foods would have the most fiber?
A) Kidney beans
B) English muffins made with enriched flour
C) Orange juice
D) Corn flakes
A – kidney beans
When eating a high-fiber diet one should
A) restrict fluid intake.
B) not be concerned about consuming large amounts.
C) avoid foods that are not whole grain.
D) increase fluid intake.
D – increase fluid intake
How many grams of carbohydrate, per day, must humans consume to avoid ketosis?
A) 75
B) 100
C) 130
D) 250
C – 130
The World Health Organization recommends limiting added sugar intake to ______ percent of our total kcalories.
A) 10
B) 15
C) 20
D) 25
A – 10
Which of the following breakfasts would be highest in carbohydrate?
A) Grapefruit half, 2 fried eggs, 3 bacon slices, 1 slice of toast with butter, coffee
B) 8 ounces orange juice, 2 cups Cream of Wheat with 2 tablespoons sugar, English muffin with jelly, 1 cup whole milk
C) 8 ounces orange juice, 2 bran muffins, 8 ounces nonfat yogurt, coffee
D) 1 cup whole milk, 2 ounces sausage, 2 fried eggs, 1 slice of toast with butter
B
Medical conditions related to metabolic syndrome are
A) Type 1 diabetes, coronary artery disease, and cancer.
B) Type 1 diabetes, coronary artery disease, and stroke.
C) Type 2 diabetes, coronary artery disease, and stroke.
D) Type 2 diabetes, coronary artery disease, and cancer.
C – Type 2 diabetes, coronary artery disease, and stroke
All of the following are characteristic of Type 2 diabetes mellitus except
A) arises most commonly in adulthood.
B) caused by insensitivity of fat and muscle cells to insulin.
C) often associated with obesity.
D) the least common form of diabetes.
D – the least common form of diabetes
The most important dietary approach for the treatment of Type 2 diabetes mellitus is to
A) lose body fat.
B) eat regular meals.
C) maintain a constant ratio of carbohydrate to protein to fat throughout the day.
D) avoid sugar.
A – lose body fat
A disaccharide is formed by the chemical bonding of
A) two monosaccharides.
B) two polysaccharides.
C) one monosaccharide and one polysaccharide.
D) two oligosaccharides.
A – 2 monosaccharides
Low blood glucose that follows a meal high in simple sugars
Reactive hypoglycemia
Fibers that either dissolve or swell in water and are fermented by bacteria in the large intestine
Viscous (soluble) fibers
Low blood glucose that follows a day or so of fasting
Fasting hypoglycemia
A form of diabetes prone to ketosis
Type 1
High blood glucose; above 125 mg/100 ml blood
Hyperglycemia
Known as complex carbohydrates
Polysaccharide
A simple sugar
Monosaccharide
Class of sugars formed by chemically linking two monosaccharides
Disaccharide
A form of diabetes in which ketosis is not commonly seen
Type 2
Fibers that mostly do not dissolve in water and are not fermented by intestinal bacteria
Nonfermentable (insoluble) fibers
The blood glucose response of a given food compared to a standard
Glycemic Index
A simple carbohydrate with the chemical composition (CH2O)n
Sugar
Low blood glucose; below 40-50 mg/100 ml blood
Hypoglycemia
A viscous fiber containing chains of galacturonic acid and other monosaccharides; characteristically found in between plant cell walls
pectin
A viscous fiber consisting of chains of galactose, monnose, and other monosaccharides; characteristically found in seaweed
mucilages
a nonfermentable fiber made up of a multi-ringer alcohol structure
lignins
A fiber that is not easily metabolized by intestinal bacteria
nonfermentable or insoluble fiber
a fiber that is readily fermented by bacteria in the large intestine
viscous or soluble fiber
fiber added to foods that has been shown to provide health benefits
functional fiber
alcohol derivative of glucose that yields about 3 kcal/g but is slowly absorbed from the small intestine; used in some sugarless gum and dietetic foods
sorbitol
alcohol derivative of the five-carbon monosaccharide, xylose
xylitol
Estimate of the amount of a sweetener that an individual can safely consume daily over a lifetime
Acceptable daily intake
alternative sweetener that yields no energy to the body; 300 times sweeter than sucrose
saccharin
alternative sweetener made of two amino acids and methanol; about 200 time sweeter than sucrose
aspartame
Disease caused by a defect in the liver’s ability to metabolize the amino acid phenylalanine into the amino acid tyrosine; untreated, toxic by-products of phenylalanine build up in the body and cause mental retardation
phenylketonuria
Alternative sweetener that has chlorines in place of three hydroxyl groups on sucrose; 600 times sweeter than sucrose
sucralose
general-purpose, nonnutritive sweetener that is approximately 7000 to 13000 times sweeter than table sugar. It has a chemical structure similar to aspartame’s
neotame
Alternative sweetener that yields no energy to the body; 200 time sweeter than sucrose
acesulfame K
Alternative sweetener derived from South American shrub; 100 to 300 times sweeter than sucrose
stevia
starch-digesting enzyme from the salivary glands or pancreas
amylase
An enzyme made by absorptive cells of the small intestine; this enzyme digests maltose to two glucoses
maltase
an enzyme made by absorptive cells of the small intestine; this enzyme digests sucrose to glucose and fuctose
sucrase
an enzyme made by absorptive cells of the small intestine; this enzyme digests lactose to glucose and galactose
lactase
Primary lactose maldigestion occurs when production of the enzyme lactase declines for no apparent reason. Secondary lactose maldigestion occurs when a specific cause, such as long-standing diarrhea, results in a decline in lactase production. When significant symptoms develop after lactase intake, it is then called lactose intolerance
lactose maldigestion
a condition in which symptoms such as abdominal gas and bloating appear as a result of severe lactose maldigestion
lactose intolerance
pouches that protrude through the exterior wall of the large intestine
diverticula
a pronounced swelling of a large vein, particularly veins found in the anal region
hemorrhoid
the condition of having many diverticula in the large instestine
diverticulosis
an inflammation of the diverticula caused by acids produced by bacterial metabolism inside the diverticula
diverticulitis
partial breakdown products of fat that contain three or four carbons
ketone bodies
the condition of having a high concentration of ketone bodies and related breakdown products in the bloodstream
ketosis
a hormone produced by the pancreas. Among other processes, insulin increases the synthesis of glycogen in the liver and the movement of glucose from the bloodstream into body cells
insulin
a hormone made by the pancreas that stimulates the breakdown of glycogen in the lover to glucose; this ends up increasing blood glucose.
Glucagon
A hormone also known as adreneline; it is released by the adrenal glands (located in each kidney) and various nerve endings in the body. It acts to increase glycogen breakdown in the liver, among other functions
epinepherine
low blood glucose, above 125 mg/ 100mL of blood for non-diabetics
hypoglycemia
the blood glucose response of a given food, compared to a standard (typically, glucose or white bread). Glycemic index is influenced by starch structure; fiber content; food processing; physical structure; and micronutrients in the meal, such as fat
Glycemic index (GI)
What kind of GI raises blood sugar the most?
high
What kinds of foods have a higher GI?
Highly processed
Adequate intake for fiber
25g/ day for women and 38g/ day for men
Average fiber intakes in North America
13g/ day for women and 17g/day for men
Upper limit of calories from added sugars
25%
The World Health organization suggests that added sugars provide no more than _________ of daily calorie intake
10% or 50g
On average Americans eat _____ of added sugar contributing to ______ of their daily calorie intake
83g 15%
erosions in the surface of a tooth caused by acids made by bacteria as they metabolize sugars
dental caries
causes hyperactivity in children
high sugar intake
a form on diabetes prone to ketosis and that requires insulin therapy
type 1
a form of diabetes characterized by insulin resistance and often associated with obesity, Insulin therapy can be use but is often not required
type 2
primary treatment goal for type 2 diabetes
weight loss
a condition in which a person has poor blood glucose regulation, hypertension, increased blood triglycerides, and other health problems. This condition is usually accompanied by obesity, lack of physical activity, and a diet high in refine carbohydrates. Also called syndrome X
Metabolic syndrome
People with this disease are 5 times more likely to develop diabetes and 2 times more likely to develop cardiovascular disease
metabolic syndrome
when the pancreas produces plenty of insulin, but the cells in the body do not react to it
insulin resistance.
Dietary fiber
a. raises blood cholesterol levels
b. speeds up transit time for food through the digestive system
c. causes diverticulosis
d. causes constipation
b
When the pancreas detects excess glucose, it releases the
a. enzyme amylase
b. monosaccharide glucose
c. hormone insulin
d. hormone glucagon
c
cellulose in a(n)
a. indigestible fiber
b. simple carbohydrate
c. energy-yielding nutrient
d. animal polysaccharide
a
Digested white sugar is broke down into _____ and _____
a. glucose, lactose
b. glucose, fructose
c. sucrose, maltose
d. fructose, sucrose
b
Starch is a
a. complex carbohydrate
b. fiber
c. simple carbohydrate
d. gluten
a
Fiber content of the diet can be increased by adding
a. fresh fruits
b. fish and poultry
c. eggs
d. whole grains and cereals
e. both a and d
e
Which form of diabetes is most common?
a. type 1
b. type 2
c. type 3
d. gestational
b
The recommended daily intake of fiber is approximately ______g
a. 5
b. 30
c. 100
d. 450
b
lactose intolerance is the result of
a. drinking high-fat milk
b. eating a large amount of yogurt
c. low lactase activity
d. a high-fiber diet
c
One of the components of metabolic syndrome is
a. high body weight
b. high waist circumference
c. low blood sugar
d. low blood pressure
b
Insulin directs the _____ to store ____ as ______
liver glucose glycogen
Directs muscles, adipose, and other cells to remove glucose from the bloodstream by taking it into those cells
insulin
When blood sugars falls, ______ is released by the pancreas
glucagon
produced by bacteria fermentation of soluble fibers in the large intestine
flatulence
Type of fiber that supplies mass to feces
insoluble or non-fermentable
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