12_Nutrients

Work Sheet 12

Overview of Nutrients

1. Define: essential nutrient, protein quality, ideal protein, essential amino acid, vitamin.

Essential Nutrient: substance which must be provided for everyone at every age for health maintenance.

Essential amino acids- cannot be synthesized by the body and must be obtained in the diet. (Arg, His, Ile, Leu, Lys, Met, Phe, Thr, Trp, Val)

Non-essential amino acids- can be synthesized by the body.

"Ideal protein"- would have an amino acid composition that provides the exact balance of amino acids required for the normal adult.

Biological Value- measure of the ability of a protein to provide essential amino acids to tissues, ability to be successfully digested..

2. List the forms and identifying characteristics of each of the forms of malnutrition.

1. Obesity- caloric intake in excess of expenditure.

Risks: cardiovascular disease, hypertension and diabetes.

2. Nutritional imbalance-overconsumption of one or more nutrients.

Risks: not many, but remember L-Trp.....

3. Undernutrition:

(a) Protein-calorie malnutrition-inadequate nourishment

Risks: starvation

(b) Kwashiorkor-diet with a low protein/energy ratio, usually based on corn

Risks: failure to thrive and develop

3. List and define the energy providing nutrients, their major functions in the body and the number of calories (Kcal) furnished by each.

1. Carbohydrates: C, H and O, provide 4 Kcal/g and are the major energy source for the world's population.

(a) Available Carbohydrates: starch in plants and glycogen in animals.

In the human diet- starch, sucrose and lactose are the most important available dietary carbohydrates.

(b) Unavailable Carbohydrates: fiber

Complex plant material comprised primarily of cellulose, lignin and pectins that resist digestion in the human body.

2. Proteins: provides 4 Kcal/g and furnish essential amino acids for the synthesis of body proteins.

3. Lipids: consist primarily of C and H

(a) Triacylglycerols (triglycerides)- body's main energy source, 9 Kcal/g. Storage form of fat for fuel in the body, 95-98% of ingested fat from food is stored in adipose cells.

(b)Phospholipids- ingested in small amounts and present in the body as constituents of cell membranes.

4. Ethanol is unique among dietary caloric sources in addition to providing a source of energy it has potent pharmacological and biochemical properties. Ethanol furnishes 7 Kcal/g, over 90% of ingested ethanol is metabolized in the liver through oxidation.

4. Discuss the significance of ethanol as fuel and low vs. high alcohol intake.

Ethanol is unique among dietary caloric sources in addition to providing a source of energy it has potent pharmacological and biochemical properties. Ethanol furnishes 7 Kcal/g, over 90% of ingested ethanol is metabolized in the liver through oxidation.

Risks: calories consumes as ethanol in excess of daily requirements are deposited as fat.....

at high doses (> 50% of calories) ------> weight loss, water soluble vitamin deficiencies, interference with metabolic pathways, reduced liver function.

5. For each of the 9 water soluble vitamins, list:

(a) major function(s)

(b) RDA (recommended daily allowance).

See Table in lecture notes.

Vitamins of Carbohydrate and Nitrogen Metabolism

1. Explain how nicotinamide adenine dinucleotide (NAD⁺) and nicotinamide adenine dinucleotide phosphate (NADP⁺) containing enzymes function in energy producing pathways.

How Does NAD+ Work as an Electron Carrier:

2. Explain how flavin adenine dinucleotide (FAD) containing enzymes function in energy producing pathways.

How Does FAD Work as an Electron Carrier:

3. List key metabolic pathways in which NAD⁺, NADP⁺ and FAD participate.

NADH Key Metabolic Pathways: glycolysis, citric acid cycle, respiratory chain, amino acid metabolism

FADH2 Key Metabolic Pathways: amino acid deamination, purine degradation, citric acid cycle, fatty acid oxidation

4. Compare and contrast dietary and metabolic sources of niacin and riboflavin.

Metabolic Sources of NAD⁺:

Tryptophan is converted to NAD⁺.

Metabolic Sources of FAD:

Not synthesized by mammals.

5. Identify the key metabolic pathways in which vitamin B₆ dependent enzymes participate.

Key Metabolic Pathways: glycogenolysis, transamination, decarboxylation