Chapter 4: Carbohydrates Flashcards
CHO
Consists of carbon, hydrogen, and oxygen.
Found in sugars, starches, and cellulose.
Primary energy source for moderate to intense exercise.
Found in the body as glucose (in the blood) and glycogen (storage form in muscle and liver).
Largest amount found in muscle with smaller amounts being found in the liver
Classified as monosaccharides, disaccharides, and polysaccharides.
Polysaccharides
Starch, fiber, and glycogen
Starch
Found in grains, legumes, and tubers
Fiber
Human body lacks the enzymes needed to break down fiber (indigestible).
Found in grains, legumes, seeds, fruits, and vegetables/
Processed grains have most of fiber removed.
Helps clean digestive tract and feeds good bacteria.
Fiber supplements
Functional fiber: added to foods to make the texture more solid.
Glycogen
Storage form of glucose.
Disaccharides
Two sugar molecules.
Sucrose, lactose, maltose
Monosaccharides
One sugar molecule.
Glucose, fructose, galactose
How are CHO classified?
Sugars/simple/highly processed CHO/bad
Starches/complex CHO/good
Digestion
Breakdown dietary CHO into disaccharides and then monosaccharides.
Begins in the mouth and stomach, predominantly occurs in small intestine.
Absorption
Movement of molecules from small intestine to blood (hepatic portal vein through carrier proteins).
Carrier molecules are limited and can only increase slightly if you consume lots of CHO that exceeds carriers available.
If CHO exceeds carriers, then it won’t be absorbed and will pass into large intestine which can lead to gas and bloating before being secreted.
Transportation
Monosaccharides transported from small intestine to the liver via portal vein (not part of circulation yet; must reach heart in order to be put into circulation).
Some glucose will remain in liver, and some will be pumped to heart to be put into circulation.
Liver converts all fructose and galactose to glucose to then be put into circulation.
CHO transported in the blood as glucose and stored in cells as glycogen.
Metabolism
All the physical and chemical changes that take place within our cells.
What are the five processes of glucose metabolism?
Regulation of blood glucose concentration
Immediate use of glucose for energy
Storage of glucose as glycogen
Use of excess glucose to make fatty acids
Productions of glucose from lactate, amino acids, or glycerol
Insulin
Secreted in response to hyperglycemia (high blood sugar).
Secreted from pancreas (beta cells) and transports glucose from blood into cells.
Increase in insulin blood = increase in glucose carrier proteins = allows more glucose to enter cells.
What areas of the body can take up glucose without the helps of insulin?
Brain and liver.
Exercising muscle cells can take up glucose without insulin as well.
Glucagon
Secreted in response to hypoglycemia (low blood sugar).
Secreted from pancreas (alpha cells) leads to liver glycogen converted to glucose and released into the blood.
Glycemic index (GI)
Ranking based on the blood glucose response of a particular food compared to a reference food.
Classification of CHO based on glycemic response (effect on blood glucose and insulin concentrations)
Response is determined for 2-3 hours after consumption.
High GI = blood glucose and insulin concentrations rise quickly (highly refined starchy foods and vegetables).
Low GI = blood glucose and insulin concentrations rise slowly (legumes, beans, and nonstarchy vegetables)
What factors determine the energy process used to metabolize glucose?
Energy need of cell, enzymatic capability, energy state, hormonal status, training history, and intensity of exercise.
Fast twitch muscle fibers prefer to use CHO via anaerobic glycolysis.
Slow twitch muscle fibers prefer to use CHO via aerobic metabolism.
Glycolysis
Breakdown of glucose to create ATP.
Occurs in anaerobic glycolysis (anaerobic process) and oxidative phosphorylation (aerobic process).
What happens if we don’t need all the glucose in our body?
Glucose can be stored as glycogen for later use.
If energy need of cell is low, stored as glycogen (mostly stored in skeletal muscle (400g) and liver (90g)).
Insulin favours glycogen storage.
Glycogen depletion favours glycogen storage.
How are fatty acids synthesized?
Products of glucose metabolism can be used to synthesize fatty acids.
Glucose can be indirectly stored as fat.
Not likely to occur if training because glycogen storage is favoured.
Fatty acid synthesis more likely to occur in sedentary people who overconsume kcal and CHO because they have more CHO than they can store as glycogen (stored as fat).
Lipogenesis
Process of converting glucose into fat for storage.
Takes place in liver or fat cells (adipocytes)
Where are fatty acids stored?
Adipose tissue
How can glucose be made from other sources?
Can produced from lactate, amino acids, and glycerol through a process called gluconeogenesis.
