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1. 1
Proteins
(amino acids)
Normal body
functions
and health
Obesity
Human
diseases
Chapter 6:
Protein and Amino Acids
mm2k.com* proteins can come from different sources: red meat, white meat (fish and bairds), legumes
* proteins/AA are the main contributor to building up of muscles and other prots. in the body

2. A. The Chemist’s View of Proteins
• Proteins are made from 20 different amino acids, 9 of
which are essential.
• Each amino acid has an amino group, an acid group, a
hydrogen atom, and a side group.
-It is the side group that makes each amino acid unique:
size, shape, and electrical charge
• The sequence of amino acids in each protein determines
its unique shape, function and complexity.

3. -carbon
R
R =
= R
R = -CH2COOH
R = CH3
proteins ar the
main source of
nitrogen in the
diet

4. The Chemist’s View of Proteins
• Amino Acids
– Nonessential (dispensable) amino acids are ones the
body can create, given the amino group and carbon
back‐bone sources
– Essential (indispensable) amino acids must be supplied
by the foods people consume.
– Conditionally essential amino acids: nonessential but
become essential under certain conditions
• Tyrosine
• Glutamine
* it is made from one of the essential AA "phenylalanine"
*any defect in the process of conversion --> affect the amount of produced tyrosine
* e.g., in phenylketonuria: lacking the enzyme that does the conversion from
phenylalanine to tyrosine
> those indv. must consume tyrosine in their diet
>those indv. must watch the amount of consumed phenylalanine that can
accumulate in the blood causing brain damage.
the body can't produce them
at all or in sufficient amounts
*used by the
immune system
as source of
energy
* become
essential when
indv is sick, and
a higher amount
of Glu is needed

5. made from Meth
*the one in red boxes are branched-chain AA
* the ones in pink boxes are conditionally essential AA
*most of prot. supplements contain Val, Iso, Leuc, b/c they are stimulate muscle prot. synthesis

6. The Chemist’s View of Proteins
• Proteins
– Amino acid chains are linked by peptide bonds in
condensation reactions.
• Dipeptides: have two amino acids bonded together.
• Tripeptides: 3 amino acids bonded together.
• Polypeptides: >3 amino acids bonded together.
– Amino acid sequences are all different, which allows
for a wide variety of possible sequences.

7. Condensation rxn:

8. The Chemist’s View of Proteins
• Proteins
– Protein Shapes:
• Dependent on the amino acid composition
> Hydrophilic side groups are attate to water.
> Hydrophobic side groups repel water.
– Protein denaturation is the uncoiling of protein that
changes its ability to function.
• Proteins can be denatured by heat and acid.
• After a certain point, denaturation cannot be
reversed.
the primary structure
found in outside of
the prot.
found inside of the
prot.
those
properties
determine how
prot. folds
(tertiary
stuctre), in turn
determine
prot. function

9. Human insulin
Hemoglobin
Quaternary Structuresinteraction of
several polyeptides
together

10. B. Digestion and Absorption
• Proteins in diets need to be digested and
absorbed.
• In the Stomach
• Protein is denatured by hydrochloric acid.
• Pepsinogen (a proenzyme): converted into its
active form pepsin by hydrochloric acid.
• Pepsin cleaves proteins into smaller
polypeptides.
help to increase the surface
area of enzymatic action

11. * most of the
enzymes are
produced in
inactive form
b/c it prevent
internal
digestion of
the
compartment
walls.
* there are
many
digestive
enzymes b/c
most of them
are selective
to type of
peptide bond.
know the names of all
enzymes and the function
of only pepsin and trypsine

12. Digestion and Absorption of Protein
• Protein Digestion
–In the Small Intestine
• Proteases hydrolyze protein into short peptide
chains (oligopeptides), which contain 4 to 9
AAs.
• Peptidases split tri- and dipeptides into AAs.

13. Protein Absorption
– Transporters / carrier proteins (?) on membranes of
mucosal cells transport AAs and a few peptides into
the cells of the intestine.
– Absorbed amino acids are
• Used by intestinal cells: synthesis of proteins or
necessary compounds, energy
• Excess is transported to the liver
– Taking enzyme supplements or consuming
predigested proteins is unnecessary
they need to be carried b/c of they are hydrophobic, b/c of their low concentration
gradient within the intestinal lumen, and b/c of the selective property of the cell
membrane
tripeptides at max
e.g., glutathion: antioxidant
it might be nesessary only when parts of the
intestine are removedd due to cancer tratment

14. Points to remember &
understand:
•Proteins differ from other macronutrients: they
contain nitrogen; and are more complex
•Proteins are important because of the amino acids
they contain
•Amino acids can be designated as essential, non-
essential or conditionally essential
•Dietary proteins need to be digested and
absorbed before our bodies can use them

15. C. Proteins in the Body
• Proteins are versatile and unique
• The synthesis of protein is determined by genetic
information.
• DNA (gene)
• DNA is transcribed to messenger RNA, mRNA
(Transcription, in the Nucleus)
proteom: the 30000 type
of prots. an average indv.
have in their body

16. • Protein is constantly being broken down and
synthesized in the body (Protein Turnover).
–Nitrogen Balance
• Synthesis
• Breakdown (Proteolysis)
• Excretion
a measure of how efficiently the
body uses the prots. it consumes

18. • Protein Synthesis
– Sequencing errors: altered proteins.
• e.g., sickle-cell anemia: incorrect AA sequence
interferes with the cell’s ability to carry oxygen.
–Nutrients and Gene Expression - Cells regulate
gene expression to make the type of protein
needed for that cell.
–Regulation by nutrients
–Protein Synthesis/Degradation?
–Nutritional Regulation of Protein Turnover?
–Nutritional Genomics and Proteomics?
= although that all cells have the same genetic material
(DNA), but diff genes get expressed in diff cells

19. Consequences of Defects in
Protein Synthesis

20. Functions of Proteins
1)Building Materials for Growth and Maintenance
• Collagen: filled with minerals to provide
strength to bones and teeth.
• Replaces tissues including the skin, hair, nails,
and GI (gastrointestinal) tract lining
2)Enzymes: facilitate anabolic (building up) and
catabolic (breaking down) chemical reactions
–Digestive enzymes
–Enzyme in metabolism: e.g. formation of
glucose from AAS

21. 3)Hormones regulate body processes and some
hormones are proteins.
• Blood glucose & Metabolism: Insulin & glucagon.
• Metabolism: Thyroxin
promotes the appearance
of glucose in blood
produced in thyroid
gland
NOT ALL
HORMONES ARE
PROTEINS !!

22. Functions of Proteins in the Body
4)Regulators of Fluid Balance
• Plasma (?) proteins attract water, and
maintain volume of body fluids to prevent
edema
• Edema can happen because
–Excessive protein losses caused by kidney
diseases, inflamation or large wounds
–Inadequate protein synthesis caused by
liver disease
–Inadequate protein intake
• Maintain the composition of body fluids
the swelling of the body
the blood
vessles become
permable -->
plasma proteins
leak out of the
blood vessels
into
the tissues
(between the
cells)

23. Blood

24. p. 182
Edema

25. Functions of Proteins
5)Acid-Base Regulators
–Act as buffers by keeping solutions acidic or
alkaline
• Acidosis: high acidity in blood & body fluids.
• Alkalosis: high alkalinity in blood & body fluids.
6)Transporters (?)
–Lipids, vitamins, minerals & oxygen in the body
–Act as pumps in cell membranes, transferring
compounds from one side of the cell membrane
to the other
the -ve charge of prots. balance the acidic H+

26. Fig. 6-10a, p. 183
Key:
Cell
membrane
Outside
cell
Inside
cell
Transport
protein
The transport protein picks up
sodium from inside the cell.
Sodium
Potassium
Membrane
transport

27. Functions of Proteins
7) Antibodies (immunoglobulins)
–Fight antigens fragment of bacteria and viruse
–Provide immunity to fight an antigen more
quickly the second time exposure occurs
8) Source of energy and glucose if needed
• Other Roles
• Blood clotting: fibrin
• Vision: Opsin in the retina
Without sufficient protein,
though, the body cannot
maintain its army of antibodies to
resist infectious diseases, thus
indv. with malnutrition are more
susceptible to diseases.
only when there is no sufficient carbohydrates/
calories in the body (NOT GOOD)

28. D. A Preview of Protein Metabolism
–Protein Turnover and the Amino Acid Pool
• Continual making & breaking down of protein.
• Pattern of AA pool is fairly constant,
irrespective of intake and/ or rate of protein
breakdown.
–Exogenous amino acids
–Endogenous amino acids
–Nitrogen Balance: balance of protein intake and
output
• used to estimate protein requirement
dietary AA: digestion and absorption of prots.
made by the body: making
nonessential AA from essential AA

29. • Protein turnover & nitrogen balance go hand in
hand.
–Zero nitrogen balance is nitrogen equilibrium,
• N intake = N output in urine
• Protein synthesis = protein breakdown
–Positive nitrogen balance: nitrogen consumed>
nitrogen excreted.
• Growing infants, children, adolescents, pregnant
women, people recovering from protein deficiency
or illness
–Negative nitrogen balance: nitrogen excreted >
than nitrogen consumed
• Burns, injuries, infections, fever
• Protein synthesis < protein breakdown

31. Proteins in the Body
• A Preview of Protein Metabolism
–Amino Acids
• Make Proteins or nonessential AAs (?)
• Make other compounds
–Tyrosine: Neurotransmitters epinephrine
and norephinephrine.
–Tyrosine: melanin pigment & metabolic
hormone thyroxine.
–Tryptophan:
»Niacin, and serotonin (neurotransmitter).
• Energy and Glucose: no storage of proteins
regulates sleeping

32. Proteins in the Body
• A Preview of Protein Metabolism
–Deaminating Amino Acids
• Nitrogen-containing amino groups are removed.
>Ammonia is released into the bloodstream.
–Ammonia is converted into urea by the liver.
–Kidneys filter urea out of the blood.
>Carbon backbone is used in other metabolic
pathways: glucose, fat
–Using Amino Acids to Make Fat
• Excess protein is deaminated and converted
into fat; Nitrogen (NH3) is excreted.
keto acid
toxic compound

33. Deamination of AAs

34. Transamination & synthesis
of non-essential amino acids
Can essential amino acids be made by this process?
What will happen if dietary supply of EAA is not adequate?
e.g.,glutamic acide.g., pyruvate e.g., alanine e.g., alpha ketoglutarate
No
to break down the prots. in the muscles and other tissues in the body

35. Preview of Protein
Metabolism: Urea synthesis

36. Fig. 6-14, p. 187
Bloodstream
To bladder and
out of body
Kidney
Urea
Bloodstream
Urea
Liver
Ammonia (NH3)
+
CO2
Amino acids
Urea
Liver disease:
high ammonia
Kidney disease:
high urea
a measure of [ammonia] and [urea]
in the blood can determin a defect in
liver or kidney

37. Preview of Protein Metabolism
 Excreting urea
 Liver releases urea into blood
Kidneys filter urea out of blood
 Liver disease
 Kidney disease
 Protein intake and urea production
Water consumption
Implication for weight loss diets
* high consumption of
prot. --> high production
of urea
* excretion of urea
needs high amount of
water for solivilbiization

38. Points to remember &
understand:
• Link between genetic information and
protein synthesis
–DNA, gene, mRNA, tRNA, rRNA
–Consequences of ‘mistakes’ in the process
• Functions of proteins
–Protein turnover and nitrogen balance
• Fates of amino acids: deamination,
transamination, keto acids, ammonia, urea

39. E. Protein in Foods
• Protein Quality: All proteins are not the same
1) Digestibility
• Depends on protein’s food source
–Animal proteins are 90-99% absorbed.
–Plant proteins are 70-90% absorbed.
> Soy and legumes are 90% absorbed.
• Other foods consumed at the same time can
affect digestibility e.g., eating fibers can reduce the transient
time / accibility time for the enzymes to the
prots. --> less digestion

40. Protein in Foods: protein quality
2) Amino Acid Composition
• The liver can produce nonessential AAs.
• Cells must dismantle to produce essential AAs
if they are not provided in the diet.
• Limiting amino acids (?)
–Reference Protein is the standard by which
other proteins are measured.
• Based on their needs for growth and
development, preschool children are used to
establish this standard.
essential AA
‫ﻳﻔﻜﻚ‬
The rationale behind this: if a protein will
effectively support a young child’s growth and
development, then it will meet or exceed the
requirements of older children and adults.

41. Protein in Foods
Protein Quality
–High-Quality Proteins
• Contains all the essential AAs
>Animal foods contain all the essential AAs.
>Plant foods: diverse in content & tend to be
missing one or more essential AAs.
–Complementary Proteins: combining plant foods
that together contain all the essential AAs
• Used by vegetarians

42. Assessing Protein Quality
• Scarcity of proteins in some regions of the world
–not in Canada
• Measures of Protein Quality (Appendix D)
–1) Amino Acid scoring
–2) Protein digestibility-corrected amino acid
score (PDCAAS)
–3) Biological Value (BV)
–4) Net Protein Utilization (NPU)
–5) Protein Efficiency Ratio (PER)
READ
THAT!!!
* how many of EAA are present in the food
* even if have high score might not be a good quality b/c it
might have poor digestibiity
Animal:100%, Soy:94%,
other plants 50-60%

43. Protein Regulation for Food Labels
–Food labels must list protein quantity in grams
–% Daily Values is not required but reflects
quantity and quality of protein using PDCAAS.
must be indicated if product is marketed
to children or has specific claim

44. F. Health Effects and Recommended
Intakes of Protein
• Protein deficiencies arise from
–protein-deficient diets and
–energy-deficient diets.
• Worldwide malnutrition problem, especially for
young children. Other groups?
• High-protein diets have been implicated in several
chronic diseases
no enough energy--> body brake up its
prots. and use them as source of energy
at places of war, developing
countries, homeless people, elder
pople

45. • Protein-Energy Malnutrition (PEM); also called
protein-kcalorie malnutrition (PCM)
• Chronic PEM: the child is short for his/ her
age and
• Acute PEM: child is thin for his/her height
• Maramus, kwashiorkor, or a combination of
the two

46. PEM
Copyright © 2013 by
Nelson Education Ltd.
Table 6.3, p. 187*liver is the place of lipid metabolism
* child has no prot. necessary --> can't take up the lipids from
the liver--> lpid accumulation in liver --> liver enlargement

47. Health Effects & Recommended Intakes of
Protein
• PEM
– 1. Marasmus:
– Chronic PEM
‘Little old people’
–2. Kwashiorkor: Acute PEM
• Older infants and young children,
18 months to 2 years of age
prot. deficiency
prot. and/or energy
deficiency
Kwashiorkor is a Ghanaian word that refers to the birth position of
a child and is used to describe the illness a child develops when
the next child is born. When a mother who has been nursing her
first child bears a second child, she weans the first child and puts
the second one on the breast. The first child, suddenly switched
from nutrient-dense, protein-rich breast milk to a starchy, protein-
poor cereal, soon begins to sicken and die. Kwashiorkor typically
sets in between 18 months and 2 years
Without proteins to
maintain fluid balance, the
child’s limbs and abdomen
become swollen with
edema—a distinguishing
feature of kwashiorkor.

48. Health Effects and Recommended
Intakes of Protein
• PEM
–Infections
• Lack of antibodies to fight infections
• Fever
• Fluid imbalances and dysentery
• Anemia
• Heart failure and possible death
–Dysentery, measles worsen condition
elevated energy requirement

49. • Rehabilitation of PEM:
– Nutrition intervention must be cautious, slowly
increasing protein.
• Programs involving local people work
better.

50. Health Effects and Recommended
Intakes of Protein
• Negative Health Effects of Protein
–Limitations
–Heart Disease
• Foods high in animal protein also tend to
be high in saturated fat.
• Homocysteine levels increase cardiac
risks.
• Arginine may protect against cardiac risks.
*byproduct of
methionine
(AA)
metabolism
* is not
incorporated to
any prot.
factors that increase the levels of Homocysteine: coffee, smoking, alcohol
act by decreasing the levels of Homocysteinein the
blood, and regulate blood pressure

51. Health Effects and Recommended
Intakes of Protein
• Health Effects of Protein
–Cancers
• High protein intake vs. high fat intake
–Adult Bone Loss (Osteoporosis)
• High protein intake associated with increased
calcium excretion.
–Animal vs. vegetable proteins
• BUT: Inadequate protein intake affects bone
health
e.g. red and processed meats are linked to colon cancer
animal prots. helps more
excretion in comparison
to vegetable ones
no enough prots. to make collagen,
the matrix for building tissues

52. –Weight Control
• High-protein foods are often high-fat
foods.
• Protein at each meal provides satiety.
–Kidney Disease
• Does not seem to cause kidney disease
but indvs. with compromised kidney function should reduce their
consumption of prots.

53. Recommended Intakes of Protein
• Daily protein intake
– Supply of essential AAs
– Source of N for synthesis of non-essential AAs
• Recommended Intakes of Protein
– 10-35% energy intake (AMDR)
– Protein RDA: 0.8 g/kg/day; athletes: 1.2-
1.7g/kg/day
• Assumptions
–People are healthy;
–Protein is of mixed quality.
–The body will use protein efficiently.
also can be used to synthesis nucleic
acid, glutamic acid
KNOW
THOSE
RANGES,
AND IF
GIVEN
THE
WEIGHT
DETERMI
N THE
RECOMON
DED
INTAKE!!!

54. p. 194

55. Health Effects and Recommended
Intakes of Protein
• Recommended Intakes of Protein
–Adequate Energy
• Must consider energy intake
• Must consider total grams of protein
–Protein in abundance is common in the U.S.
and Canada.

56. Protein and Amino Acid
Supplements
 Protein powders
 Muscle work vs. protein supplements
Athletic performance
 Whey protein
 Impact on kidneys
 Amino acid supplements
 Potential risks associated with intake
Lysine: herpes
 Tryptophan: pain and sleep

57. Nutritional Genomics
 Nutrigenomics
 Nutrients influence
gene activity
 Nutrigenetics
 Genes influence
activity of nutrients
 Human genome

58. Fig. H6-3, p. 201