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IB Standard level Biology Dulwich College Shanghai
Option A: Human Nutrition
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 274-282
Green book  pg. 191-203
A1.1 Define nutrient = a chemical substance found in foods that is used in the
human body.
A1.2 List the type of nutrients that are essential in the human diet, including
amino acids, fatty acids, minerals, vitamins and water. Essential nutrients are
those that cannot be synthesised by the body. Carbohydrates are not included
because in certain traditional human diets energy is obtained from other sources
without ill effect.
A1.3 State that non-essential amino acids can be synthesized in the body from
other nutrients.
A1.4 Outline the consequences of protein deficiency malnutrition. Protein
deficiency is shortage of one or more essential amino acids. The consequences are
lack of blood plasma proteins and subsequent tissue fluid retention, with swelling
of the abdomen. Development of children is likely to be both mentally and
physically retarded.
A1.5 Explain the causes and consequences of phenylketonuria (PKU) and how early
diagnosis and special diet can reduce the consequences. It is caused by a mutation
of a gene for an enzyme that converts the essential amino acid phenylalanine to
tyrosine.
A1.6 Outline the variation in the molecular structure of fatty acids, including
saturated fatty acids, cis and trans unsaturated fatty acids, monounsaturated and
polyunsaturated fatty acids.
A1.7 Evaluate the health consequences of diets rich in the different types of
fatty acid.
A1.8 Distinguish between minerals and vitamins in terms of their chemical nature.
Limit this to minerals being elements in ionic form and vitamins being organic
compounds.
A1.9 Outline two of the methods that have been used to determine the
recommended daily intake of vitamin C. Include brief details of one method
involving human subjects and another involving small mammals.
A1.10 Discuss the amount of Vit. C that an adult should consume per day, including
the level needed to prevent scurvy, claims that higher intake give protection
against upper respiratory tract infections, and the danger of rebound malnutrition.
Rebound malnutrition can occur when a normally adequate intake of a vitamin
follows a period of excessive intake and excretion.
A1.11 List the sources of vit. D in human diets.
A1.12 Discuss how the risk of vit. D deficiency from insufficient exposure to
sunlight can be balanced against the risk of contracting malignant melanoma.
A1.13 Explain the benefits of artificial dietary supplementation as a means of
preventing malnutrition, using iodine as an example.
A1.14 Outline the importance of fibre as a component of a balanced diet.
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 274
Green book  pg. 191
A1.1 Define nutrient = a chemical substance found in foods that is used in the
human body.
 Read the relevant sections in your textbooks and make sure you have a clear
definition in your notes.
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 274
Green book  pg. 191
A1.2 List the type of nutrients that are essential in the human diet, including
amino acids, fatty acids, minerals, vitamins and water. Essential nutrients are
those that cannot be synthesized by the body. Carbohydrates are not included
because in certain traditional human diets energy is obtained from other sources
without ill effect.
Tasks:
1.  Read the relevant sections in the books and list the essential nutrients.
Maybe make a mnemonic to remember them all.
2. Define ‘Essential nutrient’
3. Explain why carbohydrates are not classed as essential nutrients.
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 274
Green book  pg. 191
A1.3 State that non-essential amino acids can be synthesised in the body from
other nutrients.
 Read the relevant sections in the books.
 Describe the difference between an essential and a non-essential amino acid.
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 274
Green book  pg. 192
A1.4 Outline the consequences of protein deficiency malnutrition. Protein
deficiency is shortage of one or more essential amino acids. The consequences are
lack of blood plasma proteins and subsequent tissue fluid retention, with swelling
of the abdomen. Development of children is likely to be both mentally and
physically retarded.
 Read the relevant sections of the text books.
 Define malnutrition.
 Discuss the consequences of protein deficiency malnutrition.
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 274 (research question)
Green book  pg. 192
A1.5 Explain the causes and consequences of phenylketonuria (PKU) and how early
diagnosis and special diet can reduce the consequences. It is caused by a mutation
of a gene for an enzyme that converts the essential amino acid phenylalanine to
tyrosine.
The green book gives a better explanation of phenylketonuria.
Make a bullet pointed list of causes, consequences and diagnosis of
phenylketonuria.
Causes
Consequences
Diagnosis
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 275
Green book  pg. 192-193
A1.6 Outline the variation in the molecular structure of fatty acids, including
saturated fatty acids, cis and trans unsaturated fatty acids, monounsaturated and
polyunsaturated fatty acids.
Tasks:
1. Draw diagrams in your green book to represent the structure of a generalised
fatty acid.
2. Now draw diagrams to represent the following structures:
saturated fatty acids
cis and trans unsaturated fatty acids
monounsaturated fatty acids
polyunsaturated fatty acids
For each diagram give a description of that particular structure and an example.
Fatty acids have the same general structure, but there is variation in the bonds
between carbon atoms. Saturated fats have no double bonds: all possible valences
have been occupied. A mono-unsaturated fatty acid has C=C double bond, whereas
as polyunsaturated fatty acid has two or more C=C double bonds.
There is also variation in the structure of unsaturated fatty acids. cis- isomers
have the hydrogen atoms on the same side of the C=C double bond, whereas transisomers have the hydrogen atoms on opposite sides. Most trans- fats are created
artificially. In unsaturated fatty acids, the omega-number indicates the position
of the first double bond, from the CH3 group. An omega-3 fatty acid has the C=C
double bond at the third bond along the chain.
(i) Hydrogenation is a process which is used to create trans- fatty acids from cisfatty acids.
(ii) Hydrogen is used to saturate some of the double bonds in an oil, making solid
fats from liquid oils: making margarine from vegetable oil.
(iii) Although this has benefits with regard to storage and mass-production, it has
health effects.
(iv) Oleic acid (CH3(CH2)7CH=CH(CH2)7COOH) is an omega-9 fatty acid. It is a
component of olive oil in its cis- form. Its isomer, elaidic acid (trans-oleic acid) is
found in hydrogenated vegetable oil.
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 275 (research question)
Green book  pg. 193
A1.7 Evaluate the health consequences of diets rich in the different types of
fatty acid.
Tasks:
1. Follow the link below and watch the animation on cholesterol:
http://www.healthscout.com/animation/68/31/main.html
2. Describe the relationship between HDL’s and cholesterol and LDL’s and
cholesterol.
3. Complete the table below:
Fatty acid
Omega-3
Trans fats
Saturated fats
Source and
examples
Possible effects
Evidence
2/25/2011 2:53:00 PM
Components of the human diet
Ref:
Orange book  pg. 276
Green book  pg. 194
A1.8 Distinguish between minerals and vitamins in terms of their chemical nature.
Limit this to minerals being elements in ionic form and vitamins being organic
compounds.
Task:
Write a statement to describe the difference between minerals and vitamins and
give an example of each.
List some essential vitamins and minerals, their sources and functions in the body.
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 276
Green book  pg. 194
A1.9 Outline two of the methods that have been used to determine the
recommended daily intake of vitamin C. Include brief details of one method
involving human subjects and another involving small mammals.
Tasks:
1. Define ‘RDI of vitamin C’.
2. Outline the 2 methods used to determine the RDI of vitamin C.
3. List functions of vitamin C.
4. Describe experiments carried out in guinea pigs to assess RDI of vitamin C.
5. Describe experiments carried out on humans during world war II to assess RDI
of vitamin C.
Vitamin C (ascorbic acid) is essential in the human diet. It maintains mucus
membranes as a component of collagen, and promoted healing and skin growth.
Deficiency of vitamin C can lead to scurvy, characterized by bleeding hair follicles,
gums and liver spots on the skin. In extreme cases it can be fatal.
Recommended Daily Intakes (RDI) of vitamin C have been set at 45-60mg day-1.
These levels were determined based on a number of experiments into levels of
vitamin C that gave optimum benefit.
Humans and guinea pigs cannot synthesise vitamin C, so it
is possible to measure the effects of varying vitamin C
doses in carefully controlled experiments.
Human trials: observe the symptomatic effects of varying
doses of vitamin C supplementation.
Conscientious
objectors from WWII volunteered to take part in a
series of medical trials in Sheffield over a four-year
period. In one of these, 20 volunteers were used to
measure the effects of varying vitamin C concentrations.
Weeks 1-6: No vitamin C in foods, but all given 70mg supplement
Weeks 7-end (8
months): 3 kept on 70mg per day, 7 were given 10mg per day and 10 were given no
vitamin C at all. Measurement: periodic incisions were made on volunteer’s thighs,
and healing time and strength of healed tissue
were observed. Blood and urine vitamin C
concentrations were recorded. Outcomes: no ill
effects were recorded in the 70mg or 10mg
groups. The 0mg group developed scurvy within 6-8
months and some serious side effects were
recorded, including one who experienced heart
problems, which were rectified after he was given
vitamin C. Another example of a human trial took
place in a prison in Iowa, and the outcome was similar, with a recommended intake
of around 30mg day-1.
Guinea pig trials: observe the effect of vitamin C concentration on collagen
structure
after periods of varying vitamin C supplementation and measurement of
blood and urine vitamin C levels, guinea pigs were sacrificed and the structure of
collagen fibres observed. Guinea pigs with restricted vitamin C showed weaker
collagen.
(Source: Stephen Taylor, Bandung International school)
2/25/2011 2:53:00 PM
A1 Components of the human diet
Ref:
Orange book  pg. 276
Green book  pg. 194-195
A1.10 Discuss the amount of Vit. C that an adult should consume per day, including
the level needed to prevent scurvy, claims that higher intake give protection
against upper respiratory tract infections, and the danger of rebound malnutrition.
Rebound malnutrition can occur when a normally adequate intake of a vitamin
follows a period of excessive intake and excretion.
Tasks:
1. Go to the website below to read about vitamin C.
http://healthyeatingclub.com/info/books-phds/books/foodfacts/html/data/data4i.html
2. State the RDI of vitamin C and levels needed to prevent scurvy (Take notes on
symptoms of scurcy).
3. State why some organisations claim intake should be set to a higher dose.
4. Define ‘rebound malnutrition’ in reference to vitamin C.
Recommended Daily Intakes (RDI) of vitamin C have been set at 45-60mg day-1.These are
based on controlled experiments using human and animal subjects.
There is some debate on whether the RDI should be higher, with experts such as:
Nobel-winner Linus Pauling suggesting that megadoses (1000mg or more) are required per
day.
The Vitamin C Foundation recommends 3 doses of 1000mg per day.
The evidence for the efficacy of these recommendations is not strong, yet some have
suggested it can boost the immune system, prevent upper respiratory tract infections,
decrease susceptibility to cancer and speed healing and recovery from illness. Large-scale,
randomised and controlled trials of these claims have not taken place.
Some adverse effects of high dose vitamin C regimes can include intestinal problems and
acidosis, but there is little data to suggest long-term harm. It has also been suggested
that rebound malnutrition can occur as a result of systemic conditioning during long
periods of high-dose supplementation: the body is accustomed to excreting large amounts
of vitamin C and this continues once supplementation stops, leading to deficiency. The
evidence for these claims is also weak.
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 278
Green book  pg. 195
A1.11 List the sources of vitamin D in human diets.
Read the relevant pages and list the sources of vitamin D.
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 278
Green book  pg. 196
A1.12 Discuss how the risk of vitamin D deficiency from insufficient exposure to
sunlight can be balanced against the risk of contracting malignant melanoma.
Tasks:
1. State the deficiency disease caused by a lack of vitamin D in children and adults
and describe the symptoms of each.
2. State the trigger for vitamin D production in the skin and describe the risks
involved from over exposure to sunlight.
3. Describe the proposed link between vitamin D in the diet and cancer.
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. not covered
Green book  pg. 196
A1.13 Explain the benefits of artificial dietary supplementation as a means of
preventing malnutrition, using iodine as an example.
Tasks:
1. Define artificial dietary supplementation.
2. Describe the role of Iodine in the body and discuss symptoms of an iodine
deficient diet.
3. Explain how countries are addressing Iodine deficiency by use of artificial
dietary supplementation.
2/25/2011 2:53:00 PM
A1
Components of the human diet
Ref:
Orange book  pg. 278
Green book  pg. 196
A1.14 Outline the importance of fibre as a component of a balanced diet.
Tasks:
1. Name 2 categories of fibre.
2. State the recommended daily intake of fibre in grams.
3. State 4 functions of fibre in the body.