Biology Option a Food ib notes

5/28/2018 Biology Option a Food ib notes

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3/8/2014 A1 Components of the Human Diet | BioNinja

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A.1.5 Explain the causes and consequences of phenylketonuria (PKU) and how early diagnosis and a special diet can reduce the

consequences

Causes and Consequences of Phenylketonuria:

A genetic mutation changes the gene coding for tyrosine hydroxylase, which is responsible for metabolising phenylalanine into tyrosine

Phenylalanine is instead converted into phenylpyruvic acid, resulting in a high level of ketones in the blood and urine

Over time, this may result in brain damage and mental retardation

Diagnosis and Treatment of Phenylketonuria:

Diagnosis can be made by a simple blood test for the levels of phenylalanine this test is conducted shortly after birth

As PKU results in the build up of phenylalanine in the bloodstream, it is treated by following a special diet that is low in protein

Diet should include fruits, grains, vegetables and special formula milk and must be undertaken from early in li fe or else symptoms wil l

appear

Symptoms may include tremors, seizures, eczema, skin rashes and eventually brain damage (mental retardation)

A.1.6 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

Fatty acids all have the same general structure, but there may be variation in the bonding between the carbon atoms

Saturatedfatty acids have nodouble bonds between carbon atoms

Monounsaturatedfatty acids have a singledouble bond between two carbon atoms

Polyunsaturatedfatty acids have multipledouble bonds between carbon atoms

In cisisomers, hydrogen atoms attached to the double-bonded carbon atoms are on the sameside

In transisomers, hydrogen atoms attached to the double-bonded carbon atoms are on differentsides


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A.1.7 Evaluate the health consequences of diets rich in the different types of fatty acid

Saturated fats and (trans) polyunsaturated fatty acids raise levels of LDL cholesterol, leading to a higher risk of atherosclerosis and

coronary heart disease (CHD)

Monounsaturated and (cis) polyunsaturated fatty acids raise levels of HDL cholesterol and inhibit LDL cholesterol, lowering the risk of

atherosclerosis and CHD

Unsaturated fats are essential nutrients (cannot be synthesised by the body), saturated fats are not

All types of fatty acid consumed as part of the dietary intake will cause weight gain and increase risks of heart disease if taken in

excessive amounts

Comparison of the Different Types of Fatty Acids

A.1.8 Distinguish between minerals and vitamins in terms of their chemical nature

Mineralsare usually inorganic elementsin ionic form examples include sodium (Na+), potassium (K+) and iodine (I)

Vitaminsare organic compoundsmade by plants or animals examples include retinol (vitamin A) and calciferol (vitamin D)

A.1.9 Outline two methods that have been used to determine the recommended daily intake of vitamin C

Retrospective Research:

An older method used was to identify sufferers of vitamin C diseases (e.g. scurvy) and determine their levels of vitamin C

This was an inexact method for determining dietary requirements as it was based on preventing disease, not promoting cellular functions

Clinical Trials:


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More recent attempts at determining the recommended daily intake of vitamin have involved undertaking experimental studies

This has included testing cell cultures, guinea pigs and finally humans (during WWII, some objectors volunteered to participate in trials)

The purpose of these tests are to identify cellular function and disease onset at different daily dosages of vitamin C

A.1.10 Discuss the amount of vitamin C that an adult should consume per day, including the level needed to prevent scurvy, claims that

higher intake gives protection against upper respiratory tract infections, and the danger of rebound malnutrition

Common sources of vitamin C (ascorbic acid) include citrus fruits, orange juice and vitamin C tablets

The recommended daily allowance (RDA) of vitamin C will vary between individuals according to age and gender

The recommended daily intake (RDI) of vitamin C has been set at 65 90 mg (this is based on the highest RDA and thus covers all

individuals)

This intake has been determined based on the levels required to ensure no person is at risk of a deficiency disease (i.e. scurvy)

However, there is significant debate as to whether the daily intake should be higher (> 1000 mg), in order to achieve beneficial effects

Vitamin C is a potent antioxidant that is also involved in detoxification and some claim that higher doses may boost the immune system,

speed recovery from injury and protect against upper respiratory tract infections

Others suggest that taking larger doses would promote rebound malnutrition, whereby the body adjusts to a larger intake and responds

poorly whenever dosages drop back to normal levels

Neither claims are currently well supported by large-scale, controlled trials and so the evidence for these claims must be considered

weak

A.1.11 List the sources of vitamin D in human diets

Vitamin D can be produced by the skin in response to sunlight, but can also be sourced in a diet containing any of the following:

Cereal (fortified)

Oily fish (e.g. tuna)

Milk (fortified)

Egg (specifically yolk)

Liver

Yogurt

A.1.12 Discuss how the risk of vitamin D deficiency from insufficient exposure to sunlight can be balanced against the risk of contracting

malignant melanoma

UV light causes the skin to synthesise vitamin D, where it is stored in the liver for when UV levels are low (i.e. during the winter seasons)

Insufficient sun exposure may lead to skeletal deformities (i.e. rickets) due to insufficient vitamin D levels

However high levels of UV l ight can damage skin cells and cause skin cancers (malignant melanomas), so exposure must be limited

Using sun block and covering skin with clothing will prevent UV radiation reaching the skin, inhibiting vitamin D production

Certain diets (e.g. vegans, vegetarians) are more likely to result in a lack of vitamin D, so that such people need more exposure to

sunlight

Individuals with darker skin pigmentation produce vitamin D more slowly, but are better protected against skin cancers

Certain ethnicities may be at a greater risk of vitamin D deficiency due to cultural or religious practices (e.g. Muslims wearing a burqa)

Including vitamin D supplements in the diet can reduce the risk of vitamin D deficiency without requiring sun exposure

Vitamin D Deficiency Causing Rickets

A.1.13 Explain the benefits of artificial dietary supplementation as a means of preventing malnutrition, using iodine as an example

Excess vit c in the body is excreted in urea (later through urine)


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Artificial supplementation ensures a population has sufficient access to essential nutrients, even when the natural dietary supply may be

limited

Iodine is necessary for thyroxine production and an iodine deficiency wil l lead to goitre (enlarged thyroid) and mental retardation

Dietary supplementation is usually achieved via the production of iodised salt, as few foods are rich in iodine (mainly found in marine

food)

The cost to supplement these products is minimal compared to the cost of treating and caring for iodine deficient individuals

A.1.14 Outline the importance of fibre as a component of a balanced diet

Dietary fibre includes the components of foods which cannot be digested by the human body (predominantly cellulose)

Dietary fibre is an important part of a balanced diet as it plays an important role in human health:

Provides bulk in food, ensuring the continuous passage of materials through the digestive tract

Stimulates peristaltic contractions to enable the digestive system to pass food

Helps regulate blood sugar and reduces blood cholesterol

Lowers risk of appendicitis and intestinal cancer

Helps prevent constipation


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3/8/2014 A2 Energy in Human Diets | BioNinja

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A2 Energy in Human Diets

A.2.1 Compare the energy content per 100 g of carbohydrate, fat and protein

Fats contain more than twice as much energy per 100 grams than carbohydrates and proteins

Carbohydrates: 1,760 kJ per 100 g

Proteins: 1,720 kJ per 100 g

Fats: 4,000 kJ per 100 g

A.2.2 Compare the main dietary sources of energy in different ethnic groups

Dietary energy can come from a range of sources (carbohydrates, proteins or fats), but for the bulk of the population, the

primary source is crops

Most populations wil l supplement this with meat (primarily cattle in Western nations, chicken and fish in Eastern cultures)

Independent island nations may rely on fish as their main dietary source of energy

Dietary Energy Sources (Carbohydrates) Across the Globe

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A.2.3 Explain the possible health consequences of diets rich in carbohydrates, fats and proteins

Excess energy from carbohydrates, proteins or fats will all be converted and stored as fat, leading to obesity and an increased

risk of heart failure

A balanced diet is required in order to achieve sufficient intake of essential nutrients without the risk of unnecessary weight

gain

Carbohydrates

Carbohydrates are broken down into monosaccharide subunits for transport in the blood (blood sugar levels)

A sustained high intake of carbohydrates may lead to the development of diabetes, as the liver becomes less sensitive to

insulinIndividuals with diabetes may experience more frequent urination (polyuria), increased thirst and dizziness

Proteins

There are no major adverse health effects to a diet rich in protein, however excessive intake over a long period of time may

cause kidney problems

Deaminating proteins creates urea, and the kidneys will need to work overtime to flush out excess toxins, leading to

damage over time

Fats

Excessive fat intake is strongly correlated to an increase in blood pressure, atherosclerosis and the incidence of coronary

heart disease (CHD)

Atheromas (fatty deposits) develop in the arteries and significantly reduce the diameter of the lumen of the artery wall

needed for pulse flow

This may lead to the formation of clots in the artery, and if this occurs in the coronary arteries it may lead to a heart attack

A.2.4 Outline the function of the appetite control centre of the brain

Appetite is controlled by hormones (leptin, insulin, CCK) produced in the pancreas, small intestine and adipose tissue

These send messages to the appetite control centre of the brain (hypothalamus), causing a person to feel that they have

eaten enough (satiety)

The release of hormones can be triggered in a number of ways:

Stretch receptors in the stomach lining may become activated when the stomach is full

Adipose tissue may release hormones (leptin) in response to fat storage


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A.2.5 Calculate body mass index (BMI) from the body mass and height of a person

A.2.6 Distinguish, using the body mass index, between being underweight, normal weight, overweight and obese

Underweight below 18.5 Normal weight 18.5 to 24.9

Overweight 25 to 29.9 Obese above 30.0

Body Mass Index (Adult Male)

A.2.7 Outline the reasons for increasing rates of clinical obesity in some countries, including availability of cheap high-

energy foods, large portion sizes, increasing use of vehicles for transport, and a change from active to sedentary occupations

Clinical obesity describes a significant excess of body fat and is typically caused by a combination of two factors:

1. Increasing energy intake (more fats produced)

The affordability of sugar-rich, high-energy food can cause people to spurn more nutritional alternatives

People in developed countries are frequently being served larger portion sizes ('super-sizing')

2. Decreased energy expenditure (less fats consumed)

There is an increased reliance on vehicular transport in developed countries, reducing frequency of exercise

Advancements in technology (computers, robotics) have reduced the level of physical activity in a number of occupations

A.2.8 Outline the consequences of anorexia nervosa

Anorexia nervosa is an eating disorder in which individuals severely limit the amount of food they intake

It is most common in females with body image anxiety and is associated with the following heal th implications:

Malnutrition deficiency in essential nutrients due to inadequate eating patterns

Hormonal imbalance including changes in menstrual cycle and impairment of normal growth and development

Bone and muscle problems there is muscle and bone deterioration, resulting in reduced muscle mass and more fragile

bones


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Mental health issues development of mood swings, phobias and reduced mental focus

Anaemia can cause circulatory problems, including heart failure

Skin problems including discoloration and excess hair production

Immune disorders increased susceptibili ty to infections, diminished capacity for healing and repair

Death i f left untreated for a prolonged period, death may final ly result


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3/8/2014 A3 Special Issues in Human Nutrition | BioNinja

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A3 Special Issues in Human Nutrition

A.3.1 Distinguish between the composition of human milk and artificial milk used for bottle-feeding babies

A.3.2 Discuss the benefits of breastfeeding

Breastfeeding may have many benefits over bottle-feeding in helping a baby grow to be a big man, including:

Bonding may aid in mother-infant bonding and communication, reduces post-partum depression

Immunity colostrum and breast milk contain high levels of antibodies, protecting infant from infection

Gut motility breast milk is easier to digest than formula milk and stimulates digestive tract function and defecation

Maternal health improves weight loss, reduces risk of breast cancer and diabetes

Affordability breast milk is free and readily available (provided mother remains healthy)

Nutritional value more complete than formula milk, contains human proteins and more suitable fatty acids that are less

likely to cause allergies

A.3.3 Outline the causes and symptoms of type II diabetes

Causes:

Type II diabetes occurs when the body becomes less responsive to insulin due to a down-regulation of insulin receptors

in the liver

Consequently, the body becomes inefficient at lowering blood glucose levels after feeding

Type II diabetes may be caused by a genetic predisposition, dietary factors (high sugar intake) or a lack of exercise

(obesity)

Symptoms:

Hyperglycemia (high glucose content in blood)

Frequent urination (polyuria) and general thirst

Tiredness and blurred vision

Nerve damage and erectile dysfunction

Kidney and back pain

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Incidence:

Incidence of type II diabetes has been found to be higher in populations of Aboriginal Australians than those of non-

native descent

However it is currently unclear whether this is due to genetic factors or social factors (likely a combination of both)

Incidence of Type II Diabetes in the Australian Population

A.3.4 Explain the dietary advice that should be given to a patient who has developed type II diabetes

A person with type II diabetes needs to regulate their diet (calorie intake) and exercise in order to ensure a balanced energy

budget

Maintain a low fat diet in order to avoid weight gain

Consume complex carbohydrates to ensure gradual release of glucose into blood

Eat regular, small meals to ensure a steady supply of glucose into the bloodstream

Consume foods with a low glycemic index to avoid abrupt changes in blood glucose levels

A.3.5 Discuss the ethical issues concerning the eating of animal products, including honey, eggs, milk and meat

Arguments For:

Consuming animals or animal products may reduce problems of malnutrition or hunger

Certain nutrients may only be found in animal products (e.g. vitamin B12 in meat)

Many jobs may depend on cultivating and preparing animals, leading to an associated economic cost if stopped

Arguments Against:

Using antibiotics to improve the health of livestock may result in antibiotic resistance

Introducing growth hormones into the animal food supply can lead to side effects or allergies in humans

Maintaining animals as a food source requires a significantly larger ecological footprint compared with a plant diet

Agricultural practices can lead to the destruction of ecosystems and the loss of biodiversity

There can be inhumane treatment associated with animals raised for food (e.g. battery hens)

Kill ing animals for meat goes against some religious beliefs (particularly with regards to certain animal species)

Selective breeding to improve animal yield (e.g bee populations) can threaten the viability of native species

A.3.6 Evaluate the benefits of reducing dietary cholesterol in lowering the risk of coronary heart disease

Cholesterol is required for cell membrane structure and steroid synthesis, but very little (~20%) cholesterol comes from

the diet

High cholesterol diets can lead to atherosclerosis, as characterised by the deposition of fatty plaques and subsequent


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hardening of the arteries

However the risks are increased when high levels of saturated fats are combined in the diet

High levels of saturated fats also cause atherosclerosis, but also raise levels of LDL (low density lipoprotein) which

retains cholesterol in the body

Reducing dietary cholesterol levels will likely only be effective in lowering the risk of coronary heart disease if it is

combined with lower levels of saturated fats as part of a balanced diet

A.3.7 Discuss the concept of food miles and the reasons for consumers choosing foods to minimise food miles

Food miles are a measure of the distance food is transported from the site of production to the consumer

High food miles cause pollution and greenhouse gas emissions as a result of the increased fuel consumption involved

in transport

High food miles do not support local communities (as food is externally generated) and may lead to increased traffic

congestion

Produce with high food miles are less likely to be as fresh as local produce and are more likely to contain added

preservatives

Food miles do not take into consideration other environmental costs involved in food production (impact of machinery,

pesticides, etc.)

During a famine, high food miles may be justified on humanitarian grounds

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