Chapter 11: Water and the Major Minerals

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Recap of last lecture

• Heart Disease
• Fiber and bit more on carbos
• Study guide
• Old exam
• Review session

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26 Outline for today

• GM foods
• Vegetarianism
• Proteins
• Next time Cancer ??

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GM Foods

• Highly politicized subject (GM has been subject
  to various types of objection. It has been
  pronounced unnatural, held to pose an
  unjustifiable risk to the environment and to
  human health, and felt to bring us unacceptably
  close to being able to manipulate human genetic
  make-up.) (irrational fears)
• US, Europe vs. Developing nations
• More on opinions than science
• Can be considered modern version of plant
  breeding
• Involves putting a gene for desired trait into a
  plant genome. Usually available as seeds.

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What is genetic modification?

• Genetic modification (or 'GM sometimes
  opponents like to use genetically engineered)
  is the modification of genetic make-up of an
  organism usually in the context of plants.
• Strictly, it is a general term that covers many
  processes - some of these are new, some have been
  occurring since life began, and some have been
  strategically used for 10,000 years, since
  agriculture began.
• However, the term 'genetic modification' has more
  recently come to be used for the process of
  'genetic engineering', where newly developed
  processes of molecular biotechnology are employed
  to insert relatively few genes into an organism's
  genome.

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GM history

• The first major product was human insulin in
  1982, by bacteria for the treatment of diabetes.
• In 1990, the first GM food product, an enzyme
  employed in cheese making, was approved for use
  in the USA.
• In 1994 the first food product was sold
  commercially, the so-called FlavrSavr tomato,
  that had reduced activity of a gene essential for
  ripening.

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Safety

• Worldwide there have been no verifiable ill
  effects reported from the extensive consumption
  of products from GM crops over seven years by
  humans and livestock.
• The science is well defined, relatively
  straightforward, and should be safe if done
  responsibly (big bucks for the suppliers if it
  works right)

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GM foods - major advantages

• Improved yields
• Pest resistance
• Herbicide tolerance
• Majority of US corn, cotton, soy, canola crops
  are GM

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Benefits

• Economic
• Less pesticide/herbicide use
• Pharming (making medicine in plants/animals
  rather than bacteria or factories)
• Increased crop yields
• Increased plant food properties (missing
  essential amino acids, vitamins etc

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• Increasing amount of available iron, zinc in rice
• Introducing beta-carotene (Vitamin A) into rice,
  cassava, sweet potatoes
• Adding Lys to maize/corn, canola, soybeans
• Adding essential amino acids to potatoes

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• The most widely used transgenic pest-protected
  plants express insecticidal proteins derived from
  the bacterium  Bacillus thuringiensis  (Bt),
  especially cotton
• Soy, maize, canola and other minor crops, have
  been eaten on a regular basis by hundreds of
  millions of people and animals. In this time,
  there has been no substantiated case of harm
  arising from consumption of food from GM crops.

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Concerns

• Spread of GM plants via seeds, pollen
• Effects on diversity of wildlife, weeds etc.
• Human health
• Potential environmental effects
• Potential unanticipated allergic responses
• Spread of pest resistance or herbicide tolerance
  to wild plants
• Inadvertent toxicity to benign wildlife

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Traditional Methods of generating new plants with
desired characteristics

• Selecting for variability within existing
  populations arising from genetic recombinations
  resulting from sexual reproduction. It is
  noteworthy that most modern crops have been so
  altered using this technique that it is difficult
  to identify their wild progenitors. Variability
  in dog breeds provides another example of the
  results of this type of GM.
• Crossing closely related species. For example,
  modern bread wheat has arisen from two sequential
  crossings of, in total, three species.
• Isolating mutants. For example, herbicide
  resistant canola has been developed from plants
  that appeared spontaneously in Canadian fields

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GM Methods

• Isolation of a gene using enzymes that cut
  nucleotide polymers in precise locations
  identified by their nucleotide sequence. These
  are called restriction enzymes and the
  polymerase chain reaction or PCR, to aid the
  isolation of desired DNA fragments.
• The movement of the desired gene(s) into another
  organism. Genes are usually moved into other
  organisms by exploiting natural pathogens whose
  mode of infection involves the injection into the
  host of genetic material.
• This gene transfer occurs into a single cell.
  When genetically modifying plants or animals, an
  entire organism must then be regenerated from
  this single cell. Plants have the useful trait of
  totipotency, whereby cells from the adult plant
  have the ability to regenerate into new adults -
  thus a range of cell types can be used for gene
  manipulations.

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Slides from J.A. Gatehouse
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Slides from J.A. Gatehouse
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SELECTABLE AND SCREENABLE MARKERS FOR PLANT
TRANSFORMATION
 
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Organic foods
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Vegetarianism

• The major controversies concerning protein and
  nutrition probably are those of vegetarianism,
  plant food complementation, amino acid
  supplementation and how much protein we need in
  our diets (e. g. do we need more for exercise).

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Vegetarian-based diets are more healthy

• lower caloric intake and increased fiber
• lower fat (especially saturated fat) intake
• anti-cancer compounds in some plant foods (e. g.
  broccoli)
• vegetarians are likely to have lower incidence of
  obesity, hypertension (high blood pressure),
  heart disease, digestive disorders and cancer.

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Concerns

• The less animal (including seafood, dairy, egg)
  products in the diet the greater the potential
  chance for a nutritional deficiency.
• Strict vegetarian diets tend to be low in Ca,
  vit. D, B-12, Zn, riboflavin and essential amino
  acids, and possibly iron.

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VEGETARIAN DIET PLANNING

• The key point is variety
• Make sure that there are ample
• Legumes (proteins, vitamins, Fe)
• Grains (B1, Fe, minerals, protein)
• Green leafy vegies. ( Ca, riboflavin, carotene
  (vit ,Fe, Zn
• Nuts (B vitamins, proteins, Fe)

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• If we are short of amino acids we break down
  muscle protein (and other less essential
  proteins) as an initial source of amino acids for
  more vital proteins.
• Plant proteins tend to be short in Lys, Met, Trp

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Making an Essential Amino Acid

• Phenylalanine
  Tyrosine
• (Essential AA) phenylalanine
  hydroxyase (Nonessential AA)

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Quality of Protein

• High quality protein or complete protein
• Contains ample amount of all 9 essential AA
• Low quality protein
• Deficient or low in one or more essential AA
• All-or-none principle

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Limiting Amino Acid
C is the limiting amino acid in this example

• CCCCC
• AAAAAAAA CAR CAR CAR
• RRRRRR CAR CAR
• 
  R
• A A
  A

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Complementary Protein

• Food 1 Food 2
• CC CCCC
• AAAA AA CAR CAR CAR
• RRR RRR CAR CAR CAR

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Complementary Protein
Beans (legumes)
Grains Nuts/seeds
Vegetables
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• Corn is short in Trp, Lys
• Wheat is short in Ile, Lys, Met
• Rice is short in Lys
• Potato is short in Met
• Beans are short in Trp (excess Lys)

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• Legumes (beans, peas, soybeans) are short in Met
  and high in Lys
• Cereals are short in Lys
• Most animal foods are high in Lys.
• Complementary food groups are
• Grains Legumes (e.g. corn beans)
• Grains milk products (rice or wheat milk)
• Seeds Legumes (e.g. sesame garbonzos)
• In general mixing some animal protein (including
  fish and dairy) with that of plant origin
  significantly raises the protein quality.

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Turnover and Metabolism of amino acids
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Denaturation of Proteins
Functional

• Heat/acid/alkaline/enzymes
• Result in alteration of the proteins three
  dimensional structure

Non-functional
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Digestion of Protein in the Stomach

• Proteins are denatured by the cooking and the
  stomach acid
• Gastrin (hormone) stimulates the release of
  pepsinogen from the chief cells in the stomach
• Pepsinogen is converted to pepsin by the acid in
  the stomach
• Pepsin (an enzyme produced in the stomach) breaks
  down proteins into peptides

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Digestion of Protein in the Small Intestine

• Stimulates the release of hormone CCK
• Pancreas releases the protein splitting enzymes
  trypsin, chymotrypsin, and carboxypeptidase into
  the duodenum
• The enzymes will break peptides into smaller
  peptides and amino acids
• Peptides and amino acids are ready for absorption

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Protein Absorption

• Active absorption
• Whole proteins are eventually broken down to
  amino acids
• Many different amino acid transport mechanisms
• Amino acids are sent to the liver via portal
  circulation

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RDA for Protein

• 0.8 gm of protein / kg of healthy body weight
• For high quality protein our minimum needs are
  estimated at .46g/kg.
• Taking variable digestibility and quality into
  consideration leads to a value of 0.8g/kg.

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RDA for Protein

• Increased by 10-15 gm /day for pregnancy
• Endurance athletes may need 1.5 - 2 gm/kg healthy
  weight
• About 8-10 of total kcals
• Most of us eat more than the RDA for protein
• Excess protein cannot be stored as protein