Food

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Food

• Food is chemicals
• The human body is chemicals
• Diet is a major issue for Americans and is
  intimately linked to health
• Three main classes of food
• Carbohydrates
• Fats
• Proteins
• Need all three
• First a partial detour into Chapter 15.3 to 15.8

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Carbohydrates

• Composed of carbon, hydrogen, and oxygen
  (Cx(H2O)y)
• Monosaccarides (e.g., glucose) cannot be split up
  any more (Figure 15.3, 15.4)
• Disaccarides (e.g., sucrose table sugar) can by
  hydrolyzed to two monosaccarides (Figure 15.5)

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Polysaccarides Starch and Cellulose

• Are polymers
• Polymers consist of many repeating units of the
  same thing
• Polyethylene long chain
• CH3CH2CH3, where n is very big
• Polysaccarides are made up of repeating
  monosaccaride units

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Starch and Cellulose

• Starch is main energy storage system of plants
• Starch is one polymer of glucose
• Cellulose is another (Figure 15.6)
• Cellulose is structural material for plants
• Humans cannot digest it, but some animals can
  (e.g., cows and grass)

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Carbohydrates are Fuels

• Have a high energy content
• Recall the rocket fuel demo
• Humans have evolved to like sugar - aided
  survival
• But now this is a liability
• Sugar foods are empty calories that provide
  little nutritive value

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How Human Body Uses Sugars

• Glucose and other monosaccarides can go directly
  into the bloodstream from the intestines
• Sugar must be first hydrolyzed to split its two
  units into glucose
• Lactose, another sugar, requires a special enzyme
  to break down
• Some adults lack this enzyme, leading to lactose
  intolerance

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Complex Carbohydrates

• Bread, flour, cereals, and pasta have complex
  carbohydrate starches
• Should be our primary energy source
• Starch is hydrolyzed to glucose
• Glucose is then oxidized via complex reactions to
  produce energy, CO2 and water

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Fats

• Probably worst to eat in excess
• Are from a class of compounds called lipids
• Lipids are soluble in organic solvents, but not
  in water
• Float on water
• Are esters of fatty acids and glycerol
  triglycerides
• Table 15.1

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Fats and oils

• Can be classified by degree of unsaturation (how
  many double bonds)
• Polyunsaturated means many double bonds
• Monounsaturated means one double bond
• Saturated fats have no double bonds
• Fats are stored throughout body in adipose tissue
  and also around organs for protection

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Unsaturation

• Unsaturated compounds (e.g.,unsaturated fats,
  alkenes) react with iodine and bromine
• Halogen adds to double bond
• Saturated compounds (e.g., saturated fats,
  alkanes) do not
• Iodine number is number of grams of iodine
  consumed by 100 g of fat or oil
• Higher iodine number means more unsaturated
• Animal fats have lower iodine numbers than
  vegetable fats (Butter 25 Peanut oil 85)

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Something You Already Know

• Too much fat in American Diet
• Some other countries have lower fat diets
• Recommended limits 10 of calories from saturated
  fats (worst) max, 10 monounsaturated, 10
  polyunsaturated

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Saturated Fats

• Thought to cause arteriosclerosis - calcified
  (calcium compounds) deposits on walls of arteries
• Plaque in arteries rich in cholesterol
• http//www.howstuffworks.com/cholesterol.htm

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Partially Hydrogenated Vegetable Oils

• Take polyunsaturated vegetable oil
• Chemically hydrogenate to replace double bonds
  with hydrogens
• More saturated fat
• Crisco and margarine are pretty much the same
• Butter vs margarine?
• Figure 16.7
• New York City passes trans fat ban

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Challenges with Diet Issues

• A lot of involved with food
• Expensive, difficult, and time consuming to do
  truly controlled studies of the effect of diet
• Result there is probably a lot more to know

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Artificial Fats

• May sell, but do they help you lose weight?
• Fats make things taste good - smooth feeling of
  ice cream or butter
• Olestra is ester of sucrose
• Cannot be digested, but feels like fat
• Cost 200M to develop
• Dissolves away vitamins A,D,E, and K
• Pdb model of olestra

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Proteins

• Are polymers of amino acids
• Amino acids consist of an amino group a
  carboxylic acid group (Table 15.3)
• H2N-R-COOH
• Joined together with peptide bond
• CONHC
• Figure 15.11

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Sequence of Amino Acids Determines Proteins

• Very complex combinations of amino acids are
  possible
• These make up proteins
• Proteins make up a large fraction of living
  organisms
• Do many useful things
• We eat proteins as well

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Structure of Proteins

• Shape of Proteins very important to function
  many, many exquisite machines
• CrystalMaker structure Figure 15.13, 15.14,15.15
• Have primary (bonds), secondary (coils), tertiary
  (folding of coils) structure
• Analogy phone cord (primary), phone cord coil
  (secondary), tangling of phone cord (tertiary)
• Structure is determined by contacts between
  peptide chains
• Major unsolved problem in biochemistry (many
  billions of )

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Protein Unfolding

• When protein loses tertiary structure (unfolds),
  it can no longer function
• Caused by chemicals, heat, and many other
  stresses
• Cooking partly involves unfolding
• Complex chemistry

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Genes (DNA) Provide Code for Proteins

• Crystalmaker DNA

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Proteins in Our Diet

• Essential amino acids cannot be synthesized by
  humans(table 15.3)
• Obtained from breaking down proteins in digestive
  tract
• Necessary for muscles, hair, enzymes, many other
  functions
• Animal foods have lots of protein
• Need to be careful to get these essential acids
  if vegetarian
• http//www.google.com/search?hlenieISO-8859-1q
  toomuchprotein3F

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Minerals

• Are inorganic nutrients, e.g., P,S,F,Ca,
• Look at cereal box
• Many minerals are important to life
• Iron for blood - transports oxygen
• Iodine for thyroid
• Calcium for bone

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Vitamins

• Organic compounds that are required to prevent
  specific diseases
• Vitamin C (Ascorbic Acid) prevents scurvy
• Is an antioxidant
• Linus Pauling Vitamin C
• Come in water soluble and fat soluble forms
• Fat soluble can be stored water soluble cannot
  (Vitamin C)

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Dietary Fiber

• Fiber composed of cellulose
• Cellulose absorbs water
• More frequent passage of waste through colon
• Lower colon cancer rate

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Food Additives

• Read the food label confusing
• What is all of that stuff there for?
• Compensate for loss of nutrients by food
  processing
• Add flavor, preserve (antioxidants), change
  texture etc.
• Remember that food is chemicals
• Regulated by FDA
• Two competing interests food producers and food
  consumers

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Additives continued

• Chemicals in Food?
• Natural chemicals vs. Artificial chemicals?
• Salt is salt sugar is sugar caffeine is
  caffeine
• But do need to worry about some chemicals in food
• Also chemicals formed during natural cooking
  process

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Acrylamide

• Recently found to form when starches and sugars
  are subjected to high temperatures
• Causes cancer in high concentrations in lab
  animals
• Found in deep fried foods
• Simple amide (crystalmaker)
• Notice relationship to protein linkage
• Another reason not to eat French Fries?
• No one knows about concentration dependence of
  carcinogenicity of acrylamide

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Nutritive Food Additives

• Thiamine, riboflavin,folic acid and niacin
  removed in processing of whole wheat
• So these additives are added to white flour to
  replace what was there in the first place
• Many processed foods need these additives to
  replace what was already there
• Lack of folic acid is implicated in certain birth
  defects