Chapter 4: Carbohydrates

Question 1

CHO

Answer 1

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.

Question 2

Polysaccharides

Answer 2

Starch, fiber, and glycogen

Question 3

Starch

Answer 3

Found in grains, legumes, and tubers

Question 4

Fiber

Answer 4

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.

Question 5

Glycogen

Answer 5

Storage form of glucose.

Question 6

Disaccharides

Answer 6

Two sugar molecules.
Sucrose, lactose, maltose

Question 7

Monosaccharides

Answer 7

One sugar molecule.
Glucose, fructose, galactose

Question 8

How are CHO classified?

Answer 8

Sugars/simple/highly processed CHO/bad
Starches/complex CHO/good

Question 9

Digestion

Answer 9

Breakdown dietary CHO into disaccharides and then monosaccharides.
Begins in the mouth and stomach, predominantly occurs in small intestine.

Question 10

Absorption

Answer 10

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.

Question 11

Transportation

Answer 11

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.

Question 12

Metabolism

Answer 12

All the physical and chemical changes that take place within our cells.

Question 13

What are the five processes of glucose metabolism?

Answer 13

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

Question 14

Insulin

Answer 14

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.

Question 15

What areas of the body can take up glucose without the helps of insulin?

Answer 15

Brain and liver.
Exercising muscle cells can take up glucose without insulin as well.

Question 16

Glucagon

Answer 16

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.

Question 17

Glycemic index (GI)

Answer 17

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)

Question 18

What factors determine the energy process used to metabolize glucose?

Answer 18

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.

Question 19

Glycolysis

Answer 19

Breakdown of glucose to create ATP.
Occurs in anaerobic glycolysis (anaerobic process) and oxidative phosphorylation (aerobic process).

Question 20

What happens if we don’t need all the glucose in our body?

Answer 20

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.

Question 21

How are fatty acids synthesized?

Answer 21

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).

Question 22

Lipogenesis

Answer 22

Process of converting glucose into fat for storage.
Takes place in liver or fat cells (adipocytes)

Question 23

Where are fatty acids stored?

Answer 23

Adipose tissue

Question 24

How can glucose be made from other sources?

Answer 24

Can produced from lactate, amino acids, and glycerol through a process called gluconeogenesis.

Question 25

Gluconeogenesis

Answer 25

Producing glucose from other sources (small amounts)

Question 26

What fuel sources can be used in as energy source for exercise?

Answer 26

Creatine phosphate, CHO, fats, and proteins

Question 27

How is the fuel source used determined?

Answer 27

Depends on intensity and duration of exercise.
Very high intensity anaerobic exercise uses creatine (creatine phosphate system).
High intensity anaerobic exercise uses CHO (anaerobic glycolysis)
Moderate to high aerobic exercise uses CHO (oxidative phosphorylation)

Question 28

Where does CHO used for exercising muscle come from?

Answer 28

Stored muscle glycogen
Glucose that is brought into the muscle from the blood.

Question 29

Where does glucose in the blood come from?

Answer 29

Comes from the liver in 3 processes…
1) the breakdown of liver glycogen
2) the production of glucose from other sources (gluconeogenesis)
3) the ingestion, digestion, and absorption of CHO as food or fluids

Question 30

What source of energy does exercising muscle prefer to use first?

Answer 30

CHO stored as glycogen.
Even when blood glucose is available.
Exercising muscle will use muscle glycogen before blood glucose.

Question 31

What is muscle glycogen depletion associated with?

Answer 31

Fatigue which occurs in exercise that is 60+ mins in duration if no CHO is consumed during this time.

Question 32

What process does exercising muscle mimic?

Answer 32

Exercise has insulin like effect meaning it stimulates the uptake of glucose from the blood by skeletal muscle.

Question 33

How is homeostasis maintained during exercise?

Answer 33

Glucagon regulates blood glucose levels through 2 processes…
1) glycogenolysis: stimulates release of glucose by liver
2) gluconeogenesis: stimulates liver to make glucose from other sources

Question 34

What can occur with regular aerobic training?

Answer 34

Increases the capacity for CHO metabolism.
Increases aerobic capacity of muscle by increasing number and size of mitochondria, oxidative enzyme activity, muscle glycogen stores (20-30% more), and enhanced oxidative capacity increases fat utilization.

Question 35

What can occur when training in low or depleted CHO state?

Answer 35

Intended to enhance fat metabolism.
May increase mitochondrial function.
May be difficult to train with low CHO stores.
May compromise/suppress immune system.

Question 36

How is glucose metabolism controlled during exercise?

Answer 36

Controlled by the hormone glucagon which is stimulated when blood glucose is low. Insulin secretion is suppressed.
It stimulates breakdown of liver glycogen and gluconeogenesis.
Higher intensity exercise creates stress within the body that stimulates the SNS and releases stress hormones catecholamines and cortisol.
Catecholamines epinephrine and norepinephrine stimulate glycogen breakdown (glucose from liver) and glucogenogenesis.
Cortisol stimulates breakdown of proteins into amino acid that may be used in gluconeogenesis.

Question 37

How does exercise intensity affect CHO metabolism?

Answer 37

Intensity and duration have substantial effect on metabolism based on metabolic rate and source of fuel used.
As exercise intensity increases percentage energy from CHO increases and proportion of energy from fat decreases.
CHO is main source of energy for moderate to high intensity exercise.