Chapter 11Nutrition: Food for ThoughtDo you think about the foodthat goes into your body and how it affects you?

How can you interpret the various nutrition informationfound in the press?

What are trans fats?Good carbs vs. bad ones?

11.1

Food Production Utilizes Natural Resources

Kilograms of grain per 1 kg of food

Square meters of land per 1 kg of food

11.1

World Average Meat Consumption

11.1

Other Natural Resource Impacts of Food Production

• Water • Pumping water for irrigation depletes aquifers• Rivers dry up down stream if irrigating upstream• Increased BOD from fertilizer runoff

• Pollution• Waste from crop residues and livestock• Insecticide and herbicide contamination

• Land• Erosion of topsoil• Lost of forest when cleared for farmland

Malnutrition is caused by a diet lacking in the proper mix of nutrients, even though the energy content of the food eaten may be adequate.

Undernourishment is experienced when the daily caloric intake is insufficient to meet the metabolic needs of a person.

Although there are cases of malnourished and undernourished people in the U.S., 68% of the adult population is classified as overweight with almost half of that population classified as obese.

Obesity and its related adverse health effects are overtaking smoking as the No. 1 cause of death in the United States.

11.2

Useful Terms

Remember: Calories are often used to express the energy released when food is metabolized.

1 calorie (cal) is the amount of energy required to raise the temperature of 1.0 g of water by 1 oC.

This is a small quantity of energy, so we typically use kilocalories (kcal):

1 kcal = 1,000 cal

The dietary Calorie (C) is also 1,000 cal.

And 1 cal = 4.184 J11.2

A Typical Food Label Tells Us:

Caloric Content

Total Fats

Total Carbohydratesand Proteins

What do these things mean at the microscopic level?

What are saturated/unsaturated fats, fiber, sugars, and cholesterol?

11.2

11.2

We are what we eat!

Composition of the human body

11.3

Fats and OilsProperties of fats: greasy, slippery, soft, low-melting, water insoluble solids.

Butter, cheese, cream, whole milk, and certain meats and fish are loaded with them. All of these products are of animal origins.

But margarine and some shortenings are evidence that fats can also be of vegetable origin. Oils, such as those obtained from olives, corn, or nuts, exhibit many of the properties of animal-based fats, but in liquid form.

Stearic acid: condensed formula CH3(CH2)16COOH

Stearic acid: ball-and-stick molecular formula

11.3

Fatty acids are characterized by two structural features:

1. A long hydrocarbon chain generally containing an even number of carbon atoms (typically 12 to 24)

2. A carboxylic acid group (-COOH, or –CO2H) at the end of the chain.

11.3

Fats are triglycerides that are solid at room temperature, whereas oils are triglycerides that are liquid at room temperature.

A triglyceride is simply an ester of three fatty acid molecules and one glycerol molecule.

glycerol

Triglycerides belong to the lipid family, a class of compounds that includes cholesterol and other steroids, including some complex compounds such as lipoproteins that contain fatty segments.

C

O

OHCH3(CH)16

C

O

OHCH3(CH)16

C

O

OHCH3(CH)16

+ triglyceride

11.3

The formation of a triglyceride is made from 3 molecules of stearic acid and one glycerol molecule:

Ester formation was covered in Chapter 9

Ester functional group

CC

C

H OH

H

HHH

HO

OH+

C

O

OHCH3(CH)16

C

O

OHCH3(CH)16

C

O

OHCH3(CH)16

CC

C

H O

H

HHH

OC

O

CH3(CH)16

CO

CH3(CH)16

O

CO

CH3(CH)16

+ 3 H2O

glycerol

stearic acid

11.3

Types of Lipids

11.3

Saturated fatty acids contain only C-to-C single bonds between the carbon atoms.

A fatty acid is unsaturated if the molecule contains one or more C-to-C double bonds between carbon atoms.

CH3(CH2)16COOH

Stearic acid, a saturated fatty acid

CH3—(CH2)7—CH=CH—(CH2)7—COOH

Oleic acid, a monounsaturated fatty acid

CH3—(CH2)4—CH=CH—CH2—CH=CH—(CH2)7—COOH

Linoleic acid, a polyunsaturated fatty acid

CH3—CH2—CH=CH—CH2—CH=CH—CH2—CH=CH—(CH2)7—COOH

Linolenic acid, a polyunsaturated fatty acid

11.4

Saturated and Unsaturated Fats

Partially Hydrogenated Fats

11.4

CH3(CH2)4—CH=CH—CH2—CH=CH—(CH2)7COOH + H2

CH3(CH2)4—CH2—CH2—CH2—CH=CH—(CH2)7COOH

Hydrogenation reduces C=C bonds to C-C bonds; H2 is added across the double bond. A metal catalyst is required.

The number of double bonds in the fatty acid decreases, and it is transformed from an oil into a semisolid fat.

The hydrogenation can be controlled to yield products with desired melting point, softness, and spreadability.

Trans fats

11.4

In a trans isomer, H atoms are on the opposite side of the double bond.

In a cis isomer, H atoms are on the same side of the double bond.

* Both acids have the same chemical formula.

11.5

What’s a Carbohydrate?

Carbohydrates are compounds containing carbon, hydrogen, and oxygen. The best known dietary carbohydrates are sugars (like glucose) and starch.

A single sugar,or monosaccharide

Starch

alcohol groups

A disaccharide

11.5

Carbohydrates have a 2:1 ratio of H to O atoms (like water)

Single sugars have the formula C6H12O6 – ringed structures containing either 4 or 5 carbon atoms and one oxygen atom.The single sugars are also called monosaccharides.

and refer to the 3-D position of the –OH group(or –CH2OH group) at the indicated carbons.

is pointing down, is up: the fructose is shown in an atypical, upside down position.

When many sugars are linked together you have polysaccharides, which are natural polymers:

11.5

Because the single sugars can be either or , two different linkages arise.

When glucose polymerizes,

an – linkage makes starch

and a – linkage makes cellulose.

11.5

Starch is the primary carbohydrate component of several foods such as potatoes.

Cellulose is the primary fibrous component in the cell walls of plants.

Glycogen is the polysaccharide form of carbohydrate that is stored in our bodies; this is our storehouse of energy.

Polysaccharides

We humans are able to digest starch, but we lack the enzymes required to digest cellulose.

Sweetness Value of Natural and Synthetic Sweeteners

11.6*There is concern about the health impacts of the amount of sweeteners that people consumer per day .

Proteins

11.7

Proteins are an essential part of every living cell. They are also major components in hair, skin, and muscle; and they transport oxygen, nutrients, and minerals through the bloodstream.

Many of the hormones that act as chemical messengers are proteins, as are all the enzymes that catalyze the chemistry of life.

Proteins are polyamides or polypeptides, polymers made up of amino acid monomers. The great majority of proteins are made from various combinations of the 20 different naturally occurring amino acids.

Examples of different amino acids

11.7

Proteins are made of amino acids. The general formula for an amino acid includes four groups attached to a carbon atom: (1) a carboxylic acid group, -COOH; (2) an amine group, -NH2; (3) a hydrogen atom, -H; and (4) a side chain designated as R:

They differ from one another by the different R groups

Two amino acids can link together via a peptide bond:

11.7

Peptide bondThe two molecules join, expelling a molecule of water.

The process may repeat itself over and over, creating a peptide chain.

Once incorporated into the peptide chain, the amino acids are known as amino acid residues.

Proteins

11.7

• Protein formed depends both on the amino acids present and the sequence of those amino acid residue in the peptide • Food needs to be ingested regularly to replenish the protein in the body, and these are constantly broken down and reconstructed • Some amino acids (essential amino acids) cannot be synthesized by humans, so must be ingested in our diet

11.8

Vitamins are defined by their properties:

• They are essential in the diet, although required in very small amounts

• They all are organic molecules with a wide range of physiological functions

• They generally are not used as a source of energy, although some of them help break down macronutrients

11.8

Minerals (either ions or inorganic compounds) are essential for good health.

The important, essential minerals are shown on this periodic table.

In the body, metallic elements typically exist as cations (positive charge), and the nonmetals usually occur as anions (negative charge).

11.9

Energy from the Metabolism of Food

C6H12O6 + 6 O2 6 CO2 + 6 H2O + Energy

(chlorophyll acts as a catalyst)

The breaking of chemical bonds in glucose and oxygen molecules requires the absorption of energy.

But a greater amount of energy is released as carbon dioxide and water are formed. There is a net release of energy; it is an exothermic reaction.

11.9

The basal metabolism rate (BMR) is the minimum amount of energy required daily to support basic body functions.

11.10

What are some of the notable differences between these two USDA healthful diet recommendations?

MyPyramid (“Steps to a Healthier You”) and MyPlate

11.10

www.MyPyramid.gov

What are some of the notable differences between these two USDA healthful diet recommendations?

11.11

11.11

Carbon Footprint for Food to Reach Grocery Store in Great Britain:

11.11

Carbon Dioxide Emissions for Food Production: