Carbohydrates Flashcards
example of starches
Grains, corn, rice, barley, vegetables, beans, and wheat
example of sugars
Sweets (candy), sugar (cane sugar), fruit, and milk
Monosaccharides
They define the single sugar units of glucose, fructose, and galactose and represent the absorbable forms of carbohydrates for the body.
Disaccharides
They define pairs of sugar units
the three nutritionally important disaccharides are
sucrose, maltose, and lactose.
Polysaccharides
They define glucose chains longer than 10 units in length, but they can be as large as several thousand glucose units in length.
Oligosaccharides
They define sugar units ranging from 3 to 10 units in length and are largely indigestible to humans.
___________________________________________ represent the three nutritionally important monosaccharides to humans
glucose (aka dextrin or dextrose), fructose, and galactose
what are monosaccharides composed of?
carbon, hydrogen, oxygen
which monosaccharides are hydrocarbons?
Glucose, Galactose, and Fructose
C6H12O6 is the molecular structure of which monosaccharides?
Glucose, Galactose, and Fructose
examples of sucrose
cane sugar, brown sugar, and date sugar.
example of maltose
corn syrup, brown rice syrup, and molasses.
sucrose is made of _____ and _______
glucose and fructose
maltose is made of _______ and _______
1 glucose and 1 glucose
lactose is made of _________ and _________
glucose and galactose
example of Fructo-oligosaccharides
Jerusalem artichoke, leeks, onions, and asparagus
examples of Galacto-oligosaccharides
Soybeans and human breast milk
examples of Inulin
Chicory root, sugar beets, leeks, asparagus, and banana
prebiotics
oligosaccharides made from enzymes from intestinal bacteria that serve as food for our large intestinal bacteria
Amylose
A straight-chain and digestible form of starch containing glucose molecules.
Amylopectin
A branched-chain and digestible form of starch containing glucose molecules.
Because enzymes digest from open ends of a structure, ____________ will digest to the absorbable monosaccharide form of glucose faster than ________.
amylopectin, amylose
both amylose and amylopectin are digestible and make up approximately ___% and ____% of the digestible starches found in vegetables, grains, pasta, rice, and beans, respectively
20%, 80%
Greater levels of ___________ result in a faster and a greater spike in blood sugar than a similar compound with more ________.
amylopectin, amylose
Soluble Fiber
A type of dietary fiber that dissolves in water to form a gel, associated with heart health benefits and glucose control.
Examples of soluble fiber include
pectins, gums, and mucilages that originate from the inside of the plant cell
soluble fibers are sometimes called ________ fibers
fermentable
Soluble fibers are found in
at bran, oatmeal, beans, fruits and vegetables
why does fiber aid in weight loss?
It can delay gastric emptying (from the stomach) and it promotes an overall feeling of fullness, thereby potentially reducing caloric intake.
why can fiber reduce the risk of heart disease?
It can bind to cholesterol particles. It can prevent its absorption and help remove this compound from the body.
Insoluble Fiber
A type of dietary fiber that does not dissolve in water, associated with promoting bowel regularity.
insoluble fiber (water insoluble) form the structural parts of plants and include compounds like ___________, _____________, and ___________,
cellulose, hemicellulose, and lignin
why does insoluble fiber help the digestive tract?
It adds bulk and draws water into the GI tract. It improves regularity in the large intestine to avoid constipation and other bowel-related health problems (e.g., hemorrhoids).
foods containing insoluble fiber
Whole-grain wheat
Celery
Brown rice
Quinoa
Apple peels
Broccoli
a grain kernel consists of three parts:
the bran, germ, and endosperm
The ______ is the outermost layer of the kernel and is designed to protect the kernel from the environment.
the bran
the bran contains…….
B vitamins, antioxidants, and fiber.
the _______ is the embryo of the kernel and contains B vitamins, minerals, some protein, and healthy fats.
germ
The ____________ is the largest portion of the kernel. It contains starchy carbohydrates, some protein, and small amounts of vitamins and minerals.
endosperm
____________ is a large molecule with a pinwheel orientation centered around a protein core (glycogenin), and it can range from 100 to over 30,000 glucose units
glycogen
why can’t muscle glycogen be used to help preserve blood glucose during times when blood sugar levels decrease?
because muscles cells, unlike liver cells, lack a specific enzyme called glucose 6-phosphatase, which helps create a free glucose molecule from glucose 6-phosphate, a compound that is formed when stored glycogen is broken down for energy
Normal carbohydrate storage in muscle cells is approximately _______ grams per kilogram (____ g/lb.) of muscle tissue
15 g/kg or 6.8 g/lb
liver cells store approximately ____ grams per kilogram (____g/lb.) of tissue
50 g/kg or 22.7 g/lb
blood glucose stores range between ___ to ____ grams in a small adult, to about ____ to ___ grams in a very-large male.
3 to 5, 10 to 15
Triglycerides
The primary storage and transportable form of fats in the body, composed of three free fatty acids bound to a glycerol backbone.
Ketones
A group of incompletely metabolized fat fragments that are normally produced during fat metabolism in the absence of adequate carbohydrates.
Gluconeogenesis
A metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as lactate, glycerol, and glucogenic amino acids.
Bolus
A mass of food that has been chewed and is now ready to initiate the swallowing process.
Duodenum
It is the first section of the small intestine where some digestion occurs. It is located immediately after the stomach and leads into the jejunum.
Chyme
The partially digested, semi-fluid mass of food expelled by the stomach to the duodenum.
Jejunum
It is the second section of the small intestine where digestion and absorption occur. It is located immediately after the duodenum and leads into the ileum.
Ileum
It is the final section of the small intestine where lots of absorption occurs. It is located immediately after the jejunum and leads into the large intestine.
Brush Border
The wall of the small intestine, composed of villi and microvilli, that enhance the region’s surface area for the final stages of digestion and absorption.
Villi
These are small, finger-like projections located on the walls of the intestine that extend into the intestinal tract that serve to increase the body’s surface area for absorption of nutrients.
Hepatic Portal Vein
The vein that transports blood from the spleen, stomach, pancreas, and the intestinal tract to the liver.
Cirrhosis
A liver disease marked by the replacement of healthy liver tissue with scar tissue that is a result of alcohol abuse.
Non-Alcoholic Fatty Liver Disease
The development of a fatty liver resulting from excessive quantities of fats being deposited from causes that exclude alcohol.
Glycogenolysis
The process of breaking down the glycogen molecule into its individual glucose units for entry into the energy pathways.
glucagon
a hormone also released from the pancreas responsible for telling the liver to release glucose into the bloodstream. It promotes glycogenolysis and gluconeogenesis, and it also inhibits lipogenesis.
Catabolic
The breakdown of nutrients to release energy.
Any excess carbohydrates not used for immediate energy production can be stored as ________ within the ________ and ______
glycogen within the muscle and liver
excess carbohydrates that can’t be stored as glycogen can be converted to ______
triglycerides
chyme is neutralized by ___________
sodium bicarbonate
Once absorbed, all monosaccharides enter the __________________ for transportation to the liver.
hepatic portal vein
____________ feeds directly into the energy pathways, while only about 35 to 45% of the absorbed ____________ is oxidized in the energy pathways
glucose, fructose
_____ to ______% of the fructose taken into the cell becomes converted to glucose for glycogen synthesis.
40-50%
Fructose intakes need to be consumed in quantities over ___________ a day for there to be any measurable detriment to human health.
100 g
the average American consumes roughly _____ grams of fructose per day
55 grams
function of glucagon
hormone responsible for telling the liver to release glucose into the bloodstream
why can’t insulin physically enter a cell?
Insulin is protein-based and cell membranes are fat-based, essentially repelling anything that is water soluble, like protein. Therefore, insulin, acting like a key, binds to specialized receptors, acting like locks that are embedded within the cell membrane
The presence of exercising hormones like ______________ and ___________________ in circulation bind to receptors in the pancreas to inhibit much of the production of insulin.
norepinephrine, epinephrine
why does exercising inhibit insulin production?
this occurs because exercise is a catabolic event that relies on the release of stored energy to use for work and insulin is an anabolic hormone that normally functions to build energy stores and prevents their breakdown or release.
If insulin is suppressed during exercise, yet needed to move glucose into cells, then why do individuals ingest carbohydrates (e.g., drinks or food) during exercise?
certain cells like muscle, liver and fat cells rely on that insulin-mediated glucose uptake (IMGU) pathway for moving nutrients into the cell during resting conditions, but when insulin production and release is suppressed (i.e., during exercise), these cells rely on a second, non-insulin mediated glucose uptake (NIMGU) pathway to help move glucose into the cell.
During exercise, epinephrine, norepinephrine, and glucagon levels all increase to stimulate _________________ and _________________ from the liver into the blood.
glycogenolysis and glucose release
red blood cells can only use _________ as fuel
glucose
___________ is tasked with preserving both blood sugar and liver glycogen, considering how the liver is the only organ that can release glucose into circulation.
Cortisol
what scenarios can elevate cortisol levels?
prolonged exercise, glycogen depletion, or carbohydrate/ caloric restriction
function of cortisol
stimulates lipolysis to slow carbohydrate utilization rates, but it also strives to produce much-needed glucose via gluconeogenesis.
what is cortisol made of?
primarily from amino acids that originated as muscle tissue, or from protein food sources, if they are ingested around the same time the glucose manufacture occurs (e.g., during exercise)
The glycemic index (GI score)
is a relative ranking of a food’s effect on blood glucose 2 hours after the consumption of that food.
what is the GI score of glucose?
100
what is the reference for the glycemic index?
glucose
low GI foods are classified as foods with……
scores under 55
medium GI foods are classified as foods with scores between _________
scores between 56 and 69
high GI foods are classified as foods with scores __________
scores above 69
what simple sugars have a relatively low GI score?
sucrose and fructose
what lowers fructose’s GI score?
Fructose is absorbed more slowly and needs conversion to glucose in the liver.
(RDA) for carbohydrates for adults aged 19 years and older is set at ___________
130 grams per day
Acceptable Macronutrient Distribution Range (AMDR) for carbohydrates is set at ______to ______% of the total caloric intake daily
45-65%
how much sugar does the average American consume in a year?
150 to 170 pounds of refined sugars per adult per year
what is the maximum allowed amount of sugar a day?
no more than 12 added teaspoons
American heart association recommendations for sugar
limit of 6 added teaspoons (women) and 9 added teaspoons (men)
science in the Public Interest (CSPI) recommendations for sugar
limit 100 kcal or 6 ½ teaspoons (women) and 150 kcal or 9 ½ teaspoons (men)
current USA added sugar intake
13% of total caloric intake
(22 to 28 teaspoons per day)
Recommended USA added sugar Intake
< 10% of total caloric intake
(≤ 12 teaspoons of added sugar)
USDA total carbohydrate recommendations
Total carbohydrates should range between 45 and 65% of total calories.
USDA fiber recommendations
Fiber: 14 grams per 1,000 calories (28 grams per day for women and 35 grams per day for men)
USDA added sugar recommendations
Limit added sugar to less than 10% of total caloric intake with no more than 12 teaspoons of added sugar per day.
World Health Organization (WHO) carbohydrate recommendations
Reduce free sugar daily intake under 10% of total kcal, with additional benefits attained by reducing intake to under 5% or about 25 grams (6 teaspoons).
