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Proteins

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Is a High-Protein Diet Harmful? Low in plant foods (fiber), vitamins, phytochemicals. Intake of animal protein increases risk for heart disease (high in saturated ... – PowerPoint PPT presentation

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Title: Proteins


1
Proteins
2
Functions of Protein Building Body Constituents
  • All cells contain protein
  • Many are primarily protein
  • All body cells break down
  • Protein is needed for continual repair and
    rebuilding

3
Functions of Protein Maintaining Fluid Balance
  • Fluid flows from capillary bed into extracellular
    space (spaces between cells) to nourish those
    cells
  • Protein stays in the blood vessels (too large to
    move through vessel walls)
  • Protein in the capillaries attracts fluid back
    into the blood
  • If there is inadequate protein, extremities swell
    as fluid leaves bloodstream

4
Functions of Protein Acid-Base Balance
  • Proteins help regulate acid-base balance in the
    blood
  • pH measures acidity or alkalinity (base)
  • pH of 7 neutral
  • pHlt7 acid
  • pHgt7 alkaline or base
  • Proteins pump ions in and out of cells to
    regulate pH
  • Proteins serve as buffers compounds that
    maintain acidity within a narrow range

5
Functions of Protein Hormones
  • The bodys messenger system
  • Regulate body functions including metabolic rate
    (thyroid hormone) and blood glucose (insulin and
    glucacon)

6
Functions of Protein Enzymes
  • Speed chemical reactions
  • Genetic errors may result in lack of a key enzyme
  • Example galactosemia, PKU

7
Functions of Proteins Immune Function
  • White blood cells
  • Antibodies

8
Functions of Protein Can be Converted to Glucose
  • Maintain blood sugar for brain and red blood
    cells
  • Brain uses 19 of the bodys energy at rest
  • Amino acids can be converted to glucose
    (gluconeogenesis)

9
Functions of Protein Energy
  • Provides little energy to the body except in
    prolonged exercise
  • Only carbon backbone used
  • Deamination
  • Liver removes amine group
  • Nitrogen converted to urea and excreted by the
    kidneys
  • Inefficient and expensive energy source

10
Protein Structure
  • Carbohydrates and lipids contain carbon,
    hydrogen, oxygen
  • Proteins contain carbon, hydrogen, oxygen and
    nitrogen
  • Building blocks of proteins are amino acids

11
Amino Acid
NH2 O
R C C
OH H
  • R group
    Acid group
  • Amine group

12
Features Common to all Amino Acids
  • Central carbon
  • Amino or amine group
  • Acid group

13
Amino Acids Differentiated by
  • Side group (R group)
  • 20 different side chains
  • 20 different amino acids

14
Amino Acids
  • Nine essential amino acids
  • The body cannot make in sufficient quantities
  • Must consume in diet
  • Eleven non-essential amino acids
  • Body can produce from other amino acids

15
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16
Protein Turnover
  • Protein undergo breakdown and synthesis
  • Responds to change
  • Amino acid can be recycled

17
Proteins
  • Very large molecules
  • 1000s of amino acids joined together with
    peptide bonds

Myglobin ?
18
Protein Shape
  • Determined by amino acid sequence
  • Different amino acids joined ? different shapes
  • Different shapes ? different functions

19
Protein Synthesis
  • DNA contains coded instructions
  • Copies of codes are transferred to the cytoplasm
    (via mRNA)
  • Amino acids added one at a time with aid of tRNA

20
Protein Synthesis
21
Protein Organization
SH
SH
CH2
CH2
H O CH
H2O H O CH H N C
OH H N C OH H N
C N C OH CH
H O
CH H O CH3
H2O CH3
  • Peptide bond
  • Dipeptide
  • Tripeptide
  • Oligopeptide

22
Denaturation
  • Changes in protein shape
  • Non-functioning protein
  • Not biologically active
  • Denaturing agents
  • Acid
  • Alkaline substances (bases)
  • Heat
  • Agitation
  • Enzymes

23
Denaturation of Proteins
  • Heat/acid/alkaline/enzymes
  • Results in alteration of the
    proteins three
  • dimensional structure

24
Protein Deficiency Protein-Energy Malnutrition
  • Kwashiorkor the disease that the first child
    gets when the new child comes
  • Older child is converted from breast milk to
    protein-deficient diet
  • Moderate energy deficit with severe protein
    deficit
  • Often overlaid with infections

25
Symptoms of Kwashiorkor
  • Apathy, listlessness, withdrawal
  • Protein lacking for brain development
  • Lack energy for interaction
  • Failure to grow, poor weight gain
  • Protein unavailable for building tissue
  • Change in hair color
  • Melanin (a protein) gives hair color, not made

26
Symptoms of Kwashiorkor (cont)
  • Fatty infiltration in the liver
  • Lipoproteins are not made, fats accumulate, liver
    enlarges, abdomen protrudes
  • Massive edema in the abdomen and legs
  • Protein unavailable to maintain fluid balance
  • Some subcutaneous fat tissue

27
Kwashiorkor Treatment
  • Cure infections, parasites
  • Adequate protein, energy, vitamins, minerals
  • Successful if in time

28
Fig. 6.10
29
Marasmus
  • Starving to death
  • Often younger infants
  • Insufficient protein, energy, nutrients
  • skin and bones appearance
  • Little or no subcutaneous fat
  • Reduced brain growth

30
Marasmus
  • Little or no breast-feeding
  • Formula overdiluted, unsanitary water
  • Can occur in adults as well as infants and
    children

31
Marasmus Treatment
  • Large amounts of energy and protein
  • Permanent retardation common
  • Poor brain growth in the first year of life

32
Effect of High Protein Diet
  • Generally low in
  • Dietary fiber
  • Some vitamins
  • Some minerals
  • Phytochemicals
  • Generally high in
  • Saturated fat

33
Is a High-Protein Diet Harmful?
  • Low in plant foods (fiber), vitamins,
    phytochemicals
  • Intake of animal protein increases risk for heart
    disease (high in saturated fat)
  • Excessive intake of red meat is linked with colon
    cancer
  • Burden on the kidney
  • Increase calcium loss
  • National Academy of Sciences recommend no more
    than 2 x RDA for protein

34
Protein in Foods
35
Plant Protein
  • Provide protein, minerals, and dietary fiber
  • Contain no cholesterol
  • Limited saturated fats
  • Allow a few weeks for the GI tract to adjust to
    the higher fiber
  • Availability of Beano

36
Protein Digestion Cooking
  • Cooking food can be a first step in protein
    digestion
  • Cooking denatures and softens proteins and
    softens tough connective tissue in meat
  • Cooking makes protein-rich foods easier to chew,
    swallow, digest
  • Also makes protein-rich foods safer to eat

37
Digestion of Protein in the Stomach
  • Proteins are denatured by cooking and acid in the
    stomach
  • Gastrin stimulates the release of acid and pepsin
  • Pepsin is activated and breaks down proteins into
    peptones (shorter chains of amino acids)

38
Digestion of Protein in the Small Intestine
  • Proteins stimulate the release of CCK
  • Pancreas release the protein splitting enzymes
    trypsin, chymotrypsin, and carboxypeptidase into
    the duodenum
  • The enzymes will break peptones into smaller
    peptides and amino acids
  • Peptides and amino acids are ready for absorption

39
Protein Absorption
  • Active absorption
  • Whole proteins are broken down at the microvilli
    surface and within the absorptive cells
  • 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

40
Amino Acid Metabolism
  • Amino acids are used to synthesize new body
    proteins
  • If not used to synthesize new proteins
  • Deamination liver removes amino group
  • Nitrogen is converted to urea
  • Kidneys flush nitrogen from the body

41
RDA for Protein (adults)
  • Promotes equilibrium
  • 0.8 gm of protein / kg of healthy body weight
  • 154 lb. 70 kg
  • 2.2 kg/lb.
  • 70 kg x 0.8 g protein 56 g protein
  • kg healthy body wt

42
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
  • New DRI for protein coming

43
Fig. 6.9
44
Individual Amino Acid Supplement
  • Supplement may cause imbalances and toxicities
  • Body is designed to handle whole proteins
  • Supplement can overwhelm the absorptive mechanism
  • Excess of one AA can hamper absorption of other
    AAs

45
Dietary Protein
  • High-quality
  • complete
  • Low-quality
  • incomplete
  • All-or-none principle in protein synthesis
  • Limiting amino acid
  • Complementary protein

46
Limiting Amino Acid
C is the limiting amino acid in this example
  • CCCCC
  • AAAAAAAA CAR CAR CAR
  • RRRRRR CAR CAR

  • R
  • A A
    A

47
Complementary Protein
  • Food 1 Food 2
  • CC CCCC
  • AAAA AA CAR CAR CAR
  • RRR RRR CAR CAR CAR

48
Complementary Protein
Beans (legumes)
Grains Nuts/seeds
Vegetables
49
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50
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51
Soy
  • Soy protein is similar to animal protein (used in
    school lunches)
  • High in linoleic acid and some ?-linolenic acid
  • Calcium source and bone health
  • Isoflavones
  • Heart disease
  • Cancer

52
Vegetarian Diets
  • Why become a vegetarian?
  • Ethical reasons
  • Health reasons
  • As a group, vegetarians are thinner and healthier
    than meat eaters
  • Religious reasons

53
Types of Vegetarians
  • Vegans eat only plant foods
  • Fruitarians eat only the seed-bearing parts of
    plants
  • Lactovegetarians use dairy products
  • Lactoovovegetarians use dairy products and eggs

54
The Vegetarian Diet Pyramid
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