Transcript Essential amino acids

Option D: Human Physiology
D.1 Human Nutrition
D.1
• Essential idea: A balanced diet is essential to
human health.
Watch at home:
Components of the Human Diet
Nutrients are chemical substances found in
food that are used in the body
Nutrition Information:
Food energy: from carbohydrates, proteins, fats.
Units: food calories (kcal) or kilojoules (1kcal = 4.18kJ)
daily needs vary by individual based on gender, age, size and activity.
Fats (lipids) can be saturated or unsaturated.
Trans fats are particularly unhealthy.
Sodium (salt): keep it low.
Carbohydrates are polymers of sugars (an energy source).
Sugars are absorbed easily into the blood
Dietary fiber (cellulose) cannot be digested (healthy).
Proteins are polymers and sources of amino acids.
They are used to build new proteins in cells.
Vitamins are organic compounds that are essential in small
amounts in the diet.
Minerals are mineral ions (elements) that are also essential.
http://www.wolframalpha.com/input/?i=big+mac+nutrition
D.1.U1 Essential nutrients cannot be synthesized by the body, therefore they have to be included in
the diet.
Nutrient: a chemical substance found in foods that used in the body.
Essential Nutrients
Cannot be replaced or
synthesized by the body, so must
be taken in the diet.
Non-essential Nutrients
Can be replaced or synthesized
by the body, so are not necessary
in the diet.
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•
•
•
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• Carbohydrates/sugars (energy could
come from proteins or fats)
• Other minerals and some vitamins
• Saturated fatty acids
• Some amino acids.
Water
Minerals
Some vitamins
Some unsaturated fatty acids
Some amino acids
Dietary fiber is also necessary, though as it is
not absorbed it is technically not a nutrient.
Image: 'La Boqueria'
http://www.flickr.com/photos/9147703@N03/2803305840
Found on flickrcc.net
D.1.U2 Dietary minerals are essential chemical elements. AND D.1.U3 Vitamins are chemically
diverse carbon compounds that cannot be synthesized by the body.
Vitamins & Minerals
Minerals are inorganic elemental ions found in food.
Vitamins are complex
organic compounds
(contain C, H and O).
Some can be made by
the body, but others are
essential in the diet.
http://en.wikipedia.org/wiki/Vitamin_C
http://tinyurl.com/35d6qyq
Eye function/vision, maintenance of
epithelial tissues (hair, skin, lining of organs)
Coenzymes (assist enzymes), digestion, red
blood cell maturation, nervous system
http://whqlibdoc.who.int/publications/2004/9241546123.pdf
http://www.youtube.com/watch?v=dcw1m31zuTE
Understanding Vitamin D
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter25/animation_
_b_vitamins.html
http://www.youtube.com/watch?v=onSPZ0aBUKM
D.1.A1 Production of ascorbic acid by some mammals, but not others that need a dietary supply
Vitamin C is a compound called ascorbic acid.
Function: Immune system, healing (It is needed to synthesize collagen
fibers that form part of many tissues in the body), antioxidant.
Majority of plants and animals,
including most mammals, can
synthesize vitamin C.
All cases studied so far show a
mutation in GLO gene (codes for
the enzyme L-gulono--lactone
oxidase) is responsible. This
enzyme catalyzes the final reaction
in synthesizing vitamin C.
D.1.A1 Production of ascorbic acid by some mammals, but not others that need a dietary supply
The mutation in the GLO
gene has occurred several
times in evolutionary
history.
Those, including humans,
that cannot synthesize
vitamin C must consume it.
D.1.U6 Malnutrition may be caused by a deficiency, imbalance or excess of nutrients in the diet.
Malnutrition may be caused by a deficiency, imbalance or excess of
nutrients in the diet.
Malnutrition can be the result of a poor diet:
• Diets low in quantity – low protein and calorie content
• Unbalanced diets – fail to provide essential nutrients or contain
excess fats and refined carbs
Behavioral and physiological disorders can also be a cause of
malnutrition.
A deficiency in vitamin C can cause a
variety of symptoms that are
collectively known as scurvy. Includes
general weakness, anemia (vitamin C
helps in the absorption of iron), gum
disease, and skin hemorrhages.
https://www.nlm.nih.gov/medlineplus/ency/article/000355.htm
https://www.nlm.nih.gov/medlineplus/ency/article/000355.htm
http://whqlibdoc.who.int/publications/2004/9241546123_chap7.pdf
Nature of Science – Falsification of theories with one theory
being superseded by another
It was thought that scurvy only affected humans because
laboratory attempts to induce symptoms in mice and rats failed.
This was disproven in 1907 when scientists, Holst and Frolisch,
published their paper on scurvy in guinea pigs. This was
somewhat unpopular with the scientific community as nutrient
deficiencies were not yet known.
They successfully developed an animal model by feeding guinea
pigs a diet of whole grains. Having an animal model allowed for
the study of the factors that led to scurvy as well as the
preventative value of different foods. They cured the guinea pigs
of scurvy by feeding them cabbage and lemon juice.
What are some of the examples of
science denialism mentioned in
the video?
How do they relate to IB Biology
topics we have studied so far?
What do you think are reliable
sources of information regarding
health and nutrition?
How would you evaluate evidence
presented to you including some
of the statements he made in this
video?
http://www.ted.com/talks/michael_specter_the_danger_of_science_denial.html
D.1.A3 Lack of Vitamin D or calcium can affect bone mineralization and cause rickets or
osteomalacia.
Vitamin D can be synthesized in the skin. This can only occur when skin is exposed
to ultraviolet light (290-310 nm)
http://www.endocrinesurgery.net.au/vitamin-d/
D.1.A3 Lack of Vitamin D or calcium can affect bone mineralization and cause rickets or
osteomalacia.
Individuals with darker skin have good protection against UV
radiation, but produce less vitamin D.
A deficiency of vitamin D can lead to rickets in children
• bones near growth plates do not mineralize properly
• Leads to irregular, thick and wide bone growth
• Children do not reach optimal height & legs are often bowed
in or out at the knees
A deficiency of vitamin D can lead to osteomalacia in adults
• Means “soft bones” – bone matrix is weak
http://www.endocrinesurgery.net.au/vitamin-d/
http://www.leeds.ac.uk/yawya/bioarchaeology/Deficiency
D.1.U4 Some fatty acids and some amino acids are essential.
Fatty Acids
• High-density energy storage
• Usually solid at room temp
• Animal products, palm and
coconut oil
• High contribution to
coronary heart disease (CHD)
Image: 'Öl2'
http://www.flickr.com/photos/67499195@N00/2071538655
Found on flickrcc.net
CH3(CH2)nCOOH
• Usually oils at room temp
• Usually plant sources, e.g.
olive oil
• Lower contribution to CHD
Fatty Acids
CH3(CH2)nCOOH
High-density (efficient) energy storage
Metabolism of fatty acids in cell respiration skips glycolysis.
Coenzyme A* cuts off carbon atoms from the fatty acid in the link
reaction and carries them to the Krebs cycle.
Therefore: longer chains are a greater store of potential energy.
*Coenzymes assist enzymes and are made using vitamins. It’s all connected!
Fatty Acids
Important components of the plasma membrane
http://en.wikipedia.org/wiki/Cell_membrane
CH3(CH2)nCOOH
Fatty Acids
Have other diverse functions.
Triglycerides are efficient energy stores.
g
l
y
c
e
r
o
l
fatty acids
saturated
mono-unsaturated
poly-unsaturated
Lipid Hormones
• Steroid hormones, such as
testosterone and cortisol, are
made using lipids.
• Hormones are chemical
messengers.
http://en.wikipedia.org/wiki/Triglyceride
D.1.U4 Some fatty acids and some amino acids are essential.
Essential fatty acids: Two fatty acids, omega-3 and omega-6, are
required in our diet because we lack the enzymes to make them.
Omega-3 and omega-6 are
needed throughout the
body but are needed in
larger quantities for brain
and eye development.
D.1.U4 Some fatty acids and some amino acids are essential.
phenylalanine
hydroxylase
D.1.U4 Some fatty acids and some amino acids are essential.
Essential amino acids:
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Tryptophan
Valine
Threonine (only if phenylalanine is not in the diet)
Arginine (required in the diet of infants)
D.1.U5 Lack of essential amino acids affects the production of proteins.
Protein-deficiency malnutrition
Kwashiorkor: “The disease of the first child
when the second is born.”
https://www.youtube.com/wat
ch?v=GALbEobxEsc
Caused by a lack of essential amino acids as a result of extremely low
protein intake (such as when breastfeeding ceases for one child and the
diet switches to low-protein sources of energy).
Essential amino acids are therefore not available to make new proteins enzymes, pumps, antibodies – that are necessary for normal cell
function, growth and immunity.
Edema (severe swelling) results as fluids gather in tissues and cannot be
returned to the blood effectively. Growth is severely stunted and mental
development can be impaired.
Risk factors:
• Extreme poverty, overpopulation, large family sizes
• Drought, war, poor infrastructure
http://en.wikipedia.org/wiki/Kwashiorkor
D.1.A2 Cause and treatment of phenylketonuria (PKU).
Phenylketonuria (PKU)
Inherited, progressive, degenerative.
Cause
Autosomal recessive, disease-causing allele:
mis-sense base-substitution mutation on the gene
for the enzyme phenylalanine hydroxylase.
Result
Phenylalanine (Phe) cannot be metabolized into
tyrosine. Phe builds up in the brain, and competes
with other amino-acids related to transport.
Effect
Mental development is retarded.
Detection
http://en.wikipedia.org/wiki/Phenylketonuria
Heel-prick (Guthrie test) of newborns to test
concentration of Phe and Phe:Tyr ratio.
Phenylketonuria (PKU)
Inherited, progressive, degenerative.
Detection
Heel-prick (Guthrie test) of newborns to test
concentration of Phe and Phe:Tyr ratio.
https://youtu.be/4V9wIWKsZwE
Treatment
Strict low-Phe diet: no dairy, meat, breastmilk, nuts
or aspartame (artificial sweetener).
Tyrosine supplements may be needed.
http://en.wikipedia.org/wiki/Neonatal_heel_prick
There is no cure for PKU.
Genetic counseling would be sought by prospective
parents who suffer from or are suspected carriers of
the disease-causing PKU allele.
http://youtu.be/CEiOYSYhnhY