Energy Systems

Nutrition

I. Nutrients: substances needed for growth, metabolism and bodily functions.

A. Micronutrients: nutrients required by humans in small amounts to orchestrate a wide variety of physiological functions, but are not made by the organism.

• Water

• Fiber

• Vitamins

• minerals

B. Macronutrients: nutrients that provide calories or energy and are required in large amounts.

*Carbohydrates

*Lipids (fats)

*Proteins

1. Carbohydrates: serve important functions related to energy metabolism and exercise.

*contain C, H and O at a ratio of 1:2:1 (CH2O)n

*end with “ose”

a. Monosaccharides: bodies main energy source. (glucose, fructose, galactose)

b. Disaccharides: the combination of “two” monosaccharides (double sugar).

*each disaccharide contains glucose

Ex. glucose + fructose =sucrose

*formed by dehydration synthesis (condensation reaction) from the removal of water.

c. Polysaccharides: three or more sugars combined.

i. Plant polys:

*Starch- found in seeds, grains and corn cells (complex carbs.)

*Fiber- (cellulose) a non-starch found in plant cell walls.

ii. Animal Polys: glycogen, formed by glucogenesis, is stored in mammalian muscle and liver.

2. Lipids (oils, fats and waxes): consist primarily as triacylglycerols having a glycerol and 3 fatty acid chains. Found in adipose tissue and skeletal muscle.

Lipids Role in the Body

*Energy Reserve

*Thermal insulation

*Energy reserve

*Transport of fat soluble vitamins

*Hunger suppressor

a. Saturated vs. Unsaturated Fatty Acids

i. Saturated: contain only single bonds between carbon atoms, all other bonds attach to hydrogen.

ii. Unsaturated: contain one or more double bonds along the carbon chain.

3. Proteins: contain carbon, hydrogen, oxygen and nitrogen.

Proteins Role in the Body

*tissue synthesis (anabolism)

*constituents of plasma membranes

*globular proteins make up enzymes

a. Amino Acids: the building blocks of proteins joined by peptide bonds. The body requires 20 diff. amino acids.

i. Essential Aminos: 8 aminos that are not synthesized in the body and must be ingested.

ii. Nonessential Aminos: the remaining 12 aminos manufactured by the body.

II. Recommendations for a Balanced Diet

A. Food Energy Content: is the amount of energy obtained from food through cellular respiration

Energy Values Per 100 grams of:

• Carbs. = 1600 kilojoules (kJ)

• Lipids = 3700 (kJ)• Proteins = 1700 (kJ)

*one food calorie equals about 4.184 (kJ)

Recommended Dietary Intakes

Atheletes

*Carbs. – 500-700g

Non-Athletes

*Carbs. – 300g

*Fats – 65g

III. Carbohydrate and Fat Metabolism

A. Metabolism: set of chemical reactions in living organisms to maintain life.

1. Catabolism: breaks down organic matter.

2. Anabolism: uses energy to construct cellular components.

B. The Pancreas: serves as an endocrine and exocrine gland and regulates blood sugar levels and aids in digestion.

1. Islets of Langerhans: clusters of cells within the pancreas.

a. Beta cells: make up ¾ of the islet cells and secrete insulin.

b. Alpha cells: secrete glucagon.

2. The Role of Insulin: increases glucose uptake by cells. Exercise increases glucose uptake into skeletal muscle.

a. Glycogenesis: Insulin activates enzymes for the synthesis of glycogen.

b. Lipogenesis: insulin inhibits catabolism of fatty acids to convert excess glucose into triacylglycerols.

3. The Breakdown of Glycogen

a. Glycogenolysis: glucagon and adrenaline stimulate the breakdown of glycogen in the liver to increase blood glucose levels during long periods of exercise and times of fasting.

b. Lipolysis: the breakdown (catabolism) of adipose tissue by glucagon and adrenaline to increase blood sugar.

IV. Nutrition and Energy Systems

A. Generalized Animal Cell:

*ribosomes

*rough ER

*golgi complex

*lysosomes

*nucleus

*mitochondrion

B. Cellular Respiration: the release of energy from organic compounds in cells.

1. Mitochondria: the site of cellular respiration.

2. Adenosine Triphosphate: (ATP) the energy currency of the cell.

*the removal of the outermost phosphate releases energy (7.3 kCal) for cellular activity.

ATP ADP

a. Phosphocreatine system: (ATP-CP) re-synthesizes ATP by the hydrolysis of phosphocreatine (PCr).

*phosphate is removed from PCr and added to ADP to reform ATP.

*this occurs at the onset of intense exercise without oxygen.

3. Stages of Cellular Respiration: C6H12O6 + 6O2 6CO2+6H2O+36 ATP

a. Glycolysis: (anaerobic phase)

*takes place in the cytoplasm

*glucose is split into two pyruvates

*yields 4 ATP with a net gain of 2 ATP

i. Lactic Acid Fermentation: if O2 is deficient the pyruvates are converted into lactic acid.

*ATP production is limited, resulting in muscle fatigue.

b. Aerobic system: in the presence of oxygen pyruvate is processed within the mitochondria.

i. Pyruvates combine with 2 coenzyme A molecules to form acetyl-CoA.

ii. Krebs Cycle: Occurs in the matrix where acetyl-CoA is broken down to CO2 and H+. H+ combine with electron carriers NAD and FAD.

iii. Electron transport chain: occurs in the cristae and is used to transport electrons from NADH and FADH2.

*H+ pumped across the membrane diffuse back in to generate 32 ATP (oxidative phosphorylation).

*Oxygen acts as the final H+ acceptor to form H2O.

*occurs at a rate of 10,000,000 ATP per/sec in working muscle cells!

iv. Beta Oxidation: Triacylglycerol is hydrolized to form fatty acids and glycerol that can be used as an energy source for cellular respiration.

* glycerol enters glycolysis to form pyruvate.

* Fatty acid chains are transformed into acetyl-CoA that enter the Krebs cycle.

* O2 must be present for this to occur.

C. What role does each energy system (ATP-PCr, glycolytic and aerobic) play during exercise?

1. ATP-PCr: supplies the immediate energy for short, explosive movements. Ex. Sprint, swinging a bat.

2. Glycolytic: supplies energy after the initial 10 sec. of exercise. Used in multiple sprint sports (soccer, hockey).

3. Aerobic System: supplies long term energy when exercise extends longer than 2-3 minutes.

D. Oxygen Deficit: diff. between the amt. of O2 consumed during exercise and the amt. that would have been consumed if aerobic resp. occurred immediately.

*this reflects the amt. of energy supplied to muscles by the anaerobic systems.

*trained athletes have a smaller O2 deficit.

E. Oxygen Dept. (EPOC) excess post-exercise oxygen consumption

*represents the amt. of O2

consumed in recovery after exercise that is above the resting level.