Chapter 11 Powerpoint - Chemistry | University of Missouri

download report

Transcript Chapter 11 Powerpoint - Chemistry | University of Missouri

Chapter 11
Nutrition: Food for Thought
Do you think about the food
that goes into your body
and how it affects you?
How can you interpret the
various nutrition information
found in the press?
What are trans fats?
Good carbs vs. bad ones?
Food Production Utilizes Natural Resources
Square meters of
land per 1 kg of food
Kilograms of grain
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
11.1
Useful Terms
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
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 J
11.2
A Typical Food Label Tells Us:
Caloric Content
Total Fats
Total Carbohydrates
and Proteins
What do these things mean at
the microscopic level?
What are saturated/unsaturated
fats, fiber, sugars, and
cholesterol?
11.2
We are what we eat!
Composition of the human body
11.2
Fats and Oils
Properties 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
O
one glycerol molecule.
C
CH3(CH)16
OH
O
+
C
CH3(CH)16
OH
triglyceride
O
glycerol
C
CH3(CH)16
OH
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.
11.3
Ester functional group
The formation of a triglyceride is made from 3 molecules of stearic acid
and one glycerol molecule:
C
H
OH
HO
C
C
H
CH3(CH)16
H
C
H
OH
+
H
glycerol
OH
CH3(CH)16
O
O
C
C
O
OH
C
H
O
CH3(CH)16
O
CH3(CH)16
O
C
C
H
C
H
CH3(CH)16
O
H
O
H
C
O
C
CH3(CH)16
OH
stearic acid
+ 3 H2O
Ester formation was covered in Chapter 9
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
11.3
Saturated and Unsaturated Fats
11.4
Partially Hydrogenated Fats
Hydrogenation reduces C=C bonds to C-C bonds; H2 is added
across the double bond. A metal catalyst is required.
CH3(CH2)4—CH=CH—CH2—CH=CH—(CH2)7COOH + H2 
CH3(CH2)4—CH2—CH2—CH2—CH=CH—(CH2)7COOH
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.
11.4
Trans fats
In a cis isomer, H atoms
are on the same side of the
double bond.
In a trans isomer, H atoms
are on the opposite side of
the double bond.
* Both acids have the same chemical formula.
11.4
What’s a Carbohydrate?
Carbohydrates are compounds containing carbon, hydrogen,
and oxygen. The best known dietary carbohydrates are
sugars (like glucose) and starch.
Starch
A single sugar,
or monosaccharide
A disaccharide
alcohol
groups
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 b refer to the 3-D position of the –OH group
(or –CH2OH group) at the indicated carbons.
 is pointing down, b is up: the fructose is shown
in an atypical, upside down position.
11.5
When many sugars are linked together you have
polysaccharides, which are natural polymers:
Because the single sugars can
be either  or b, two different
linkages arise.
When glucose polymerizes,
an  – linkage makes starch
and a b – linkage makes
cellulose.
11.5
Polysaccharides
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.
We humans are able to digest starch, but we lack the
enzymes required to digest cellulose.
11.5
Sweetness Value of Natural and Synthetic Sweeteners
*There is concern about the health impacts of the amount
of sweeteners that people consumer per day .
11.6
Proteins
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
11.7
Two amino acids can link together via a peptide bond:
The two molecules join,
expelling a molecule of water.
Peptide bond
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.
11.7
Proteins
• 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
11.7
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).
11.8
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.
11.9
What are some of the notable differences between these two
USDA healthful diet recommendations?
11.10
MyPyramid (“Steps to a Healthier You”) and MyPlate
www.MyPyramid.gov
What are some of the notable differences between these two USDA
healthful diet recommendations?
11.10
11.11
Carbon Footprint for Food to Reach Grocery Store in Great Britain:
11.11
Carbon Dioxide Emissions for Food Production:
11.11