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IB HL Biology > D.1 Human nutrition > Flashcards

D.1 Human nutrition Flashcards

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1
Q

What is a balanced diet?

A

A diet that contains the accepted and defined proportions of carbohydrates, fats, proteins, vitamins, minerals, and water essential to maintain good health.

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2
Q

What are the causes of malnutrition and what can it lead to?

A

-Malnutrition may be caused by a deficiency, imbalance or excess of nutrients in the diet.

-
There are many reasons that may cause a person not to eat a balanced diet: poverty, wars, droughts, other natural disasters, living in a remote place, or simply not caring about what you eat.

-Whatever the reason, a diet lacking in an essential element may lead to severe deficiencies, illness or even death.

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3
Q

What is a nutrient?

A

-Any chemical substance that can be used by the human body.

-Some nutrients are essential for the health and survival of humans.

-The body is incapable of synthesising these molecules from other substances already present in the body and they must therefore be contained in a balanced diet.

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4
Q

What are the four categories that essential nutriants are grouped into?

A

-Minerals

-Vitamins

-Amino acids

-Fatty acids

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5
Q

Examples of minerals

A

Phosphorus, calcium, magnesium, iron

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6
Q

Examples of vitamins

A

Vtamins A, C, D, K

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7
Q

Examples of amino acids

A

Histidine, tryptophan and others

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8
Q

Examples of fatty acids

A

Certain omega-3 and omega-6 fatty acids

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9
Q

What does the body do with non-essential nutrients?

A

-Our body takes in other non-essential nutrients such as fructose or dietary fibre.

-Fructose can be made by our body and as such it cannot be considered as essential.

-Dietary fibre aids in the digestive process.

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10
Q

What happens if the body does not get all its essential nutrients (a deficiency)?

A

It can cause malnutrition

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11
Q

Other than a lack of essential nutrients, what can cause malnutrition?

A

-An imbalance of nutrients.

-An excess of nutrients.

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12
Q

Examples of the different types of malnutrition and what causes them

A

For example, a deficient intake of proteins can lead to kwashiorkor, a disorder that causes oedema, irritability, anorexia, ulcerating skin, and an enlarged liver.

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13
Q

What is the difference between malnutrition and starvation?

A

-Malnutrition is a consequence of an unbalanced diet.

-A person can eat a lot of food but still be malnourished.

-However, when an individual simply does not have enough to eat this can lead to starvation.

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14
Q

What is the difference between essential and non-essential nutrients?

A

-Essential nutrients cannot be synthesised by the human body.

-Non-essential nutrients can be replaced by another compound, or can be made by the human body.

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15
Q

Why are certain fatty acids considered to be essential?

A

Because the human body cannot synthesise certain fatty acids.

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16
Q

Give examples of essential fatty acids

A

Omega-3 and omega-6 fatty acids

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17
Q

Why are omega-3 fatty acids needed in the body?

A

For numerous normal body functions, such as controlling blood clotting and building cell membranes in the brain.

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18
Q

Why are omega-6 fatty acids needed in the body?

A

They lower LDL cholesterol (the “bad” cholesterol) and reduce inflammation, and they are protective against heart disease.

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19
Q

What is the chemical name for omega-3 and 6?

A

These fatty acids are chemically known as: alpha-linolenic acid (omega-3), and linoleic acid (omega-6).

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20
Q

What do the numbers 3 and 6 in omega-3 and omega-6 refer to?

A

The numbers refer to the first double bond counting from the CH3 (Methyl, position 1) group of the fatty acid.

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21
Q

Diagram of alpha-linolenic acid (omega-3)

A
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22
Q

Diagram of linoleic acid (omega-6)

A
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23
Q

What foods can omega-3 fatty acids be found in?

A

Fatty fish (such as salmon); some vegetable oils, such as soybean, rapeseed, flaxseed; and in Brussels sprouts, kale, spinach, walnuts.

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24
Q

What foods can omega-6 fatty acids be found in?

A

Safflower, corn, cottonseed, and soybean oils.

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25
Q

Protein synthesis requires ___

A

20 different L-amino acids

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26
Q

How many amino acids are considered essential in humans?

A

9

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27
Q

What are the nine essential amino acids?

A

-Phenylalanine

-Valine

-Threonine

-Tryptophan

-Methionine

-Leucine

-Isoleucine

-Lysine

-Histidine.

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28
Q

How can tyrosine be synthesized?

A

Tyrosine can be synthesised by the human body when phenylalanine is present in the diet.

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29
Q

Which group of people can arginine not be synthesized by?

A

Infants, so it must be present in their diet as well.

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30
Q

Why are tyrosine and arginine called conditionally essential amino acids?

A

Because they can be synthesised under some conditions but not others.

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31
Q

Tyrosine and arginine are called ___

A

Conditionally essential amino acids.

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32
Q

What happens if one of the essential amino acids is missing from the diet?

A

-Most human proteins require all 20 amino acids so if one of the essential amino acids is missing from the diet certain proteins cannot be synthesized.

-One form of malnutrition is protein deficiency. Its symptoms are fluid retention in the tissues (edema) and it is often visible in the abdominal area (swollen belly).

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33
Q

Diagram showing some of the roles of amino acids

A
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34
Q

Lack of essential amino acids affects the ___

A

Production of proteins.

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35
Q

What is the significance of the ‘6’ in an omega-6 fatty acid?

A

It denotes the first double bond between the 6th and 7th C atom starting from the CH3 (methyl group).

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36
Q

Diagram showing the composition of main elements found in the body by mass

A
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37
Q

Need to know table: The specific elements found in the body.???

A
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38
Q

What is iron needed for?

A

The functioning of hemoglobin.

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39
Q

Descibe the structure of iron atoms (in relation to hemoglobin).

A

Iron atoms are the central atom in the non-protein, heme group of haemoglobin.

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40
Q

Arsenic in the human body

A

-The human body contains arsenic.

-Arsenic, which has a poisonous reputation, may be a necessary ultra-trace element for humans.

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41
Q

Describe the need for iodine in the body

A

-It is needed for the synthesis of thyroid hormones, which can increase basal metabolic rate, affect protein synthesis, and help regulate long bone growth (in combination with growth hormone) and maturation of neurones.

-An iodine deficiency, which is quite common in areas where there is no or very little iodine in the diet, can result in goitre and severe retardation in children.

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42
Q

What are calcium and phosphorus needed for?

A

-They are necessary for the formation of bones and teeth.

-Calcium is also necessary for muscle contraction.

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43
Q

What are sodium and potassium needed for?

A

They are involved in the propagation of the nerve impulse.

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44
Q

What are vitamins?

A

Chemically diverse carbon compounds that cannot be synthesized by the body.

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45
Q

Why are vitamins needed in the diet?

A

They cannot be synthesized by the human body and must therefore be included in the diet.

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46
Q

What are the two groups that vitamins are divided into?

A

Water-soluble and fat-soluble vitamins

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47
Q

Why are there many symptoms of vitamin deficiency?

A

Because vitamins take part in many metabolic processes.

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48
Q

What happens when water- and fat-soluble vitamins are taken to excess?

A

-Water-soluble vitamins, when taken to excess, will be excreted in the urine.

-Fat-soluble vitamins can be stored in the body, but can cause problems when taken in excess.

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49
Q

Which disorder can be caused by an iodine deficiency?

A

Stunted long bone growth

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50
Q

Which vitamins can be found in eggs?

A

Vitamins A, B, D and K

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51
Q

Info about vitamin A

A

Chemical name: Retinol

Fat soluble

Daily requirement for an average male: 900 μg

Food sources: Liver, leafy vegetables, carrots, fish, soya milk, milk.

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52
Q

Info about vitamin B1

A

Chemical name: Thiamine

Water soluble

Daily requirement for an average male: 1.2 mg

Food sources: Oatmeal, brown rice, vegetables, potatoes, liver, eggs.

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53
Q

Info about vitamin B1

A

Chemical name: Thiamine

Water soluble

Daily requirement for an average male: 1.2 mg

Food sources: Oatmeal, brown rice, vegetables, potatoes, liver, eggs.

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54
Q

Info about vitamin B12

A

Chemical name: Cyanocobalamin

Water soluble

Daily requirement for an average male: 2.4 µg

Food sources: Meat and other animal products.

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55
Q

Info about vitamin B2

A

Chemical name: Riboflavin

Water soluble

Daily requirement for an average male: 1.3 mg

Food sources: Dairy products, bananas, green beans, asparagus.

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56
Q

Info about vitamin B3

A

Chemical name: Niacin

Water soluble

Daily requirement for an average male: 16 mg

Food sources: Meat, fish, eggs, many vegetables, mushrooms, tree nuts.

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57
Q

Info about vitamin B5

A

Chemical name: Pantothenic acid

Water soluble

Daily requirement for an average male: 5 mg

Food sources: Meat, broccoli, avocados.

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58
Q

Info about vitamin B5

A

Chemical name: Pantothenic acid

Water soluble

Daily requirement for an average male: 5 mg

Food sources: Meat, broccoli, avocados.

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59
Q

Info about vitamin B6

A

Chemical name: Pyridoxine

Water soluble

Daily requirement for an average male: 1.3–1.7 mg

Food sources: Meat, vegetables, tree nuts, bananas.

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60
Q

Info about vitamin B6

A

Chemical name: Pyridoxine

Water soluble

Daily requirement for an average male: 1.3–1.7 mg

Food sources: Meat, vegetables, tree nuts, bananas.

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61
Q

Info about vitamin B7

A

Chemical name: Biotin

Water soluble

Daily requirement for an average male: 30 µg

Food sources: Raw egg yolk, liver, peanuts, leafy green vegetables.

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62
Q

Info about vitamin B9

A

Chemical name: Folic acid

Water soluble

Daily requirement for an average male: 400 µg

Food sources: Leafy vegetables, pasta, bread, cereal, liver.

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63
Q

Info about vitamin C

A

Chemical name: Absorbic acid

Water soluble

Daily requirement for an average male: 50 - 90 mg

Food sources: Many fruits, especially citrus and vegetables, liver.

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64
Q

Info about vitamin D

A

Chemical name: Cholecalciferol(D3), Ergocalciferol (D2)

Fat soluble

Daily requirement for an average male: 10 µg

Food sources: Fish, eggs, liver, mushrooms.

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65
Q

Info about vitamin E

A

Chemical name: Tocopherols

Fat soluble

Daily requirement for an average male: 15 mg

Food sources: Many fruits and vegetables, nuts and seeds.

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66
Q

Info about vitamin K

A

Chemical name: Phylloquinone

Fat soluble

Daily requirement for an average male: 120 µg

Food sources: Leafy green vegetables such as spinach, egg yolks, liver.

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67
Q

What is malnutrition a result of?

A
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67
Q

What is malnutrition a result of?

A

-Any deviation from a normal healthy diet.

-It is not be confused with starvation, which is a severe deficiency in caloric energy intake.

68
Q

What are the three main causes of malnutrition?

A

-Deficiency, a diet lacking in one or more particular nutrients.

-Imbalance, a diet that has an inadequate intake of a particular nutrient.

-Excess, a diet that has a disproportionate intake of e.g. carbohydrates, fats or proteins.

69
Q

Map showing global malnutrition rates

A
70
Q

Malnutrition in high-income countries

A

-Even in nations with a high wealth status, cases of malnutrition have been documented.

-In affluent societies it can be caused by an excessive intake of fats and refined carbohydrates.

-Such a diet combined with lack of exercise can lead to obesity.

71
Q

What is apetite controlled by?

A

-By the appetite control centre in the hypothalamus (ACC).

-The centre regulates our desire to eat.

72
Q

Explain how the appetite control center in the hypothalamus (ACC) regulates our desire to eat

A

-When the stomach is empty, ghrelin is released, stimulating appetite.

-When food is ingested, the release of peptide PYY3-36 from the small intestine (along with insulin from the pancreas and leptin from adipose tissue) inhibit appetite.

73
Q

Diagram showing which factors and hormones influence the ACC in the hypothalamus

A
74
Q

What would happen without appetite control?

A

We could easily overeat, which would cause elevated blood glucose levels.

75
Q

Which factor or hormone is released by the small intestine to inhibit appetite?

A

PYY3-36

PYY3-36 is a peptide released by cells in the intestines in response to feeding. In the blood, gut, and other elements of periphery, PYY acts to reduce appetite, as it signals the hypothalamus that the stomach is full.

76
Q

What is leptin?

A

A satiety hormone made in adipose tissue.

Leptin is a hormone made by adipose cells that helps to regulate energy balance by acting on the hypothalamus, inhibiting hunger (causing a sensation of satiety).

77
Q

What is the body mass index (BMI) and what is it useful for?

A

-It is a value used to determine whether a patient is within normal parameters of mass or weight.

-It is quite a useful tool to decide whether you are under- or overweight, but must be used with care, as there are other factors to be kept in mind, such as the proportion of muscular and adipose tissues.

78
Q

How is the BMI calculated?

A

The BMI is the body mass (in kilograms) divided by the square of the body height (in metres).

79
Q

When is someone considered overweight and obese?

A

-When their BMI is between 25.1 and 29.9 kg m-2.

-Obesity is associated with BMI values above 30.0 kg m-2.

80
Q

What is a limitation of BMI?

A

-BMI is a rather coarse measurement.

-Muscles have a high mass density so some professional athletes can have BMI values above 30 without being considered to be obese.

81
Q

Map showing global obesity prevalence

A
82
Q

What are the consequences of an unhealthy diet?

A

-An unbalanced diet is unhealthy, or in other words, it can make you ill.

-Two common consequences of such a diet are type II diabetes and coronary heart disease (CHD) which includes hypertension (high blood pressure).

83
Q

What is type II diabetes?

A

-Type II diabetes, also known as late-onset diabetes or non-insulin-dependent diabetes mellitus (NIDDM), is the most common form of diabetes.

-In individuals with this condition the beta cells in the pancreas still produce insulin.

-However, these patients develop insulin resistance, which means that the insulin receptors on the cells are no longer stimulated by insulin.

84
Q

What are the probable causes of type II diabetes?

A

-High levels of fatty acids in the blood because of diets high in fat but low in fiber.

-Being overweight, especially obesity, is associated with a lack of exercise.

-Genetic makeup that influences fat metabolism.

85
Q

What are the symptoms of type II diabetes?

A

-Increased (elevated) glucose levels in the blood urine.

-Frequent need to urinate (may lead to excessive thirst).

-Tiredness and fatigue.

-Some loss of weight.

86
Q

What can diabetes increase your chances of developing?

A

CHD (coronary heart disease)

87
Q

What are hypertension and CHD?

A

-Hypertension is blood pressure above the norm.

-Coronary heart disease (CHD) is a disease in which a substance called plaque builds up inside the coronary arteries.

-These arteries supply blood with oxygen to the heart muscle.

88
Q

Meditteranean diets and CHD

A

-There is a correlation between certain diets and the incidence of CHD.

-Some diets, for example Mediterranean, include a high intake of vegetables, fruit, whole grain products, and lower amounts of fish and red meat.

-As a result populations in, for example, Greece, Italy and Japan have relatively low rates of CHD.

89
Q

Describe the correlation between CHD and intake of saturated fatty acids

A

-There is a strong correlation between a high incidence of CHD (including hypertension) and a high intake of saturated fatty acids.

-Saturated fatty acids can be deposited inside the arteries.

-If the deposits combine with cholesterol they may lead to atherosclerosis, which leads to hypertension or can cause angina and heart attacks.

-In a “chicken and egg” scenario, hypertension also can cause damage to blood vessels, increasing the risk of developing even more atherosclerotic plaques.

90
Q

Diagram showing how plaque formation in the arteries can lead to hypertension

A
91
Q

Correlation and causation in type II diabetes

A

-The causes of type II diabetes are not fully understood but there is a strong correlation of risk with being overweight and diet.

-However, many other factors can play a role in the development of type II diabetes: gender, socioeconomic status, culture and ethnic group.

92
Q

What happens at the cellular level in Type II diabetes patients?

A

-Insulin production is normal

-Cellular receptors have inactive or reduced activity

-Type II diabetes, also known as late-onset diabetes or non-insulin-dependent diabetes mellitus (NIDDM), is the most common form of diabetes. In individuals with this condition, the beta cells in the pancreas still produce insulin.

-However, these patients develop insulin resistance, which means that the receptor cells are no longer stimulated by insulin.

93
Q

What is the most extreme form of malnutrition?

A

Starvation

94
Q

What is starvation caused by?

A

A severe reduction in caloric energy intake.

95
Q

What can prolonged starvation cause?

A

-Organ damage and death if caloric energy intake is not restored in time.

-Initially, the glycogen stores in the liver are mobilised, but once they are depleted the body has to resort to other sources of energy.

96
Q

What is catabolysis?

A

-The loss of muscle and adipose tissue mass is caused by the body’s need for caloric intake and to protect the vital systems such as the nervous system and heart muscle.

-The body breaks down muscles and lipids to generate energy and amino acids.

-This process is known as catabolysis.

97
Q

Vitamin deficiency as a result of starvation

A

Vitamin deficiency is a common result of starvation, and can lead to anaemia (vitamin B12 deficiency), beriberi (vitamin B1 deficiency), pellagra (vitamin B3 deficiency), and scurvy (vitamin C deficiency).

98
Q

What is anorexia?

A

A medical term for lack of appetite.

99
Q

What is anorexia nervosa?

A

-A type of anorexia. It is an eating disorder characterized by food restriction and an irrational fear of weight gain.

-Many patients suffering from anorexia nervosa do not lose their appetites but their intake of food is very limited.

100
Q

What is anorexia nervosa caused by?

A

It has many variant causes and is often accompanied by an unrealistic body self-perception.

101
Q

What does anorexia nervosa lead to?

A

-It can lead to excessive weight loss.

-Anorexia nervosa leads to electrolyte imbalance, skeletal and heart muscle reduction, reduced blood pressure and a slower heart rate.

-The body can become covered in a fine growth of thin hair.

-In female patients it can also lead to reduced or absence of menstrual cycles.

-Extreme cases can lead to death.

102
Q

Anoreoxia nervosa causes breakdown of ___

A

Heart muscle

103
Q

What is the first process that occurs in starvation?

A

Glycogen reserve used up.

104
Q

Why can anorexia nervosa be life-threatening?

A

There is heart muscle breakdown.

105
Q

What is vitamin C and what is its need in the body?

A

-Vitamin C is also known as L-ascorbic acid.

-Humans and some animals cannot synthesise this compound.

-Vitamin C is needed for the production of collagen, the most abundant protein in the animal kingdom, found in skin, connective tissues, tendons and blood vessels.

106
Q

Why can vitamin C not be synthesized by some animals?

A

Because they have a mutation in the GLO gene which codes for an enzyme that is needed for the last step in the synthesis of L-Ascorbic acid.

107
Q

What can vitamin C deficiency cause and who is it common in?

A

A vitamin C deficiency can cause scurvy, a disease that was common amongst sailors in past centuries because of a lack of citrus fruits in their diets.

108
Q

___ are a good source of dietary vitamin C.

A

Citrus fruits

109
Q

What animals require vitamin C in their diet?

A

All the primates and some smaller monkeys.

110
Q

What are the main symptoms of scurvy?

A

-Bleeding gums, gingivitis or loose teeth

-Lack of energy

-Mood swings or depression

-Chronic joint pain

-Suppressed immune system

-Slow wound healing and bruising

111
Q

Beeding gums, gingivitis or loose teeth as symptoms of scurvy

A

Vitamin C is necessary for the synthesis of collagen, which builds and maintains tissue.

112
Q

Lack of energy as a symptom of scurvy

A

Loss of weight and extreme fatigue.

113
Q

Mood swings and depression as symptoms of scurvy

A

Irritability and rapid changes in mood may indicate a severe deficiency. Depression is common.

114
Q

Chronic joint pain as a symptom of scurvy

A

Bleeding in the joints causes constant pain.

115
Q

Suppressed immune system as a symptom of scurvy

A

Frequent diseases.

116
Q

Slow wound healing and bruising as a symptom of scurvy

A

Bruising occurs easily and wounds take a long time to heal.

117
Q

Animal model for scurvy

A

-In 1907 two Norwegian scientists, Axel Holst and Theodor Frølich, published a paper describing an animal model using guinea pigs, for scurvy.

-The study was controversial because it went against existing and accepted theories on the causes and prevention of scurvy.

-Their work falsified earlier theories which suggested that scurvy was specific to humans.

-It also paved the way for other studies that can be used to calculate how much of a particular nutrient should be ingested per day without endangering your health.

118
Q

What is RDA and how is the RDA for vitamin C calculated?

A

-RDA is recommended daily amount.

-The recommended level of vitamin C for humans is about 50 mg per day.

-Animal studies are often used to calculate this.

119
Q

Describe how a study to find the RDA using animals could be conducted

A

-Guinea pigs, which cannot manufacture vitamin C, are fed diets containing different levels of vitamin C, while all other nutrients and conditions are controlled.

1) A control group (group 0) does not receive any foods containing vitamin C.

2) Other groups (groups 1 to 10) get increasing levels of a daily supplement of vitamin C in their diet, e.g. group 1 gets 10 mg of vitamin C per day, group 2: 20 mg vitamin C per day, etc.

3) The control group will start to develop symptoms of scurvy.

4) Perhaps also groups 1 and 2 may show some symptoms, but above a certain daily supplement of vitamin C, e.g. 30 mg per day, the guinea pigs do not show the common symptoms of scurvy.

5) The data collected this way can be used to calculate the amount of vitamin C required by a human.

120
Q

What is the independent variable in the guinea pig study on the effect of vitamin C daily supplements?

A

The amount of vitamin C the animals receive per day.

(The dependent variable is the symptoms of scurvy.)

121
Q

What is PKU?

A

Phenylketonuria (PKU) is a genetic disease.

122
Q

How does PKU occur?

A

-A gene coding for phenylalanine hydroxylase, an enzyme that catalyses the hydroxylation of phenylalanine to tyrosine, is mutated.

-This results in the inability to convert phenylalanine into tyrosine. PKU is inherited as an autosomal recessive trait which means that patients with PKU have two recessive (mutated) alleles.

-As the enzyme can no longer catalyse the last and rate limiting step, phenylalanine accumulates in the body.

123
Q

How common is PKU?

A

It occurs in about 1 in 10,000 births.

124
Q

Why is early diagnosis of phenylketonuria important?

A

Because it is treatable by dietary means.

125
Q

What are the medical consequences of PKU?

A

-Intillectual disability

-Reduced growth of the head

-Lack of skin and hair pigmentation

-Seizures

126
Q

Testing for PKU

A

-PKU needs to be detected and diagnosed within 24 hours of birth. The Guthrie test is used for this purpose.

-Up until that time, phenylalanine and tyrosine levels in the infant are normal as a result of the normal metabolism of its mother.

127
Q

What diet do patients with PKU need to maintain?

A

-A diet low in phenylalanine.

-The high phenylalanine foods shown on the left should be avoided.

128
Q

Diagram showing which foods can be eaten safely (right) and will allow a PKU patient to live a normal life

A
129
Q

Why can children with PKU not consume aspartame?

A

The artificial sweetener aspartame contains phenylalanine, so children with PKU cannot eat chewing gum or drink any soft drink that contains this sweetener.

130
Q

What is the substrate for phenylalanine hydroxylase?

A

Phenylalanine

Phenylalanine hydroxylase is an enzyme that catalyses the hydroxylation of phenylalanine to tyrosine. In phenylketonuria (PKU), a gene coding for phenylalanine hydroxylase is mutated. This results in the inability to convert phenylalanine into tyrosine. Phenylalanine therefore accumulates in the body.

131
Q

Why is vitamin D needed in the body?

A

-Vitamin D (calciferol) is needed for the absorption of calcium in the digestive system.

-Calcium is needed to build healthy bones, therefore a vitamin D deficiency can lead to softening or malformation of the bones.

-Vitamin D or calcium deficiency can lead to defective bone mineralization, causing softening of the bones –> osteomalacia/rickets

132
Q

What is vitamin D deficiency and how is it different in children and adults?

A

This condition is known as osteomalacia in adults (milder condition) or rickets in children (more serious condition).

133
Q

What are two of the most important roles of vitamin D?

A

To maintain skeletal calcium balance by promoting calcium absorption in the intestines and maintaining calcium and phosphate levels for bone formation.

134
Q

What can happen if breastfeeding mothers have low vitamin D intake?

A

This can cause problems with the bone mineralisation of their infants.

135
Q

Diagram showing how vitamin D deficiency can cause rickets

A
136
Q

What foods is vitamin D found in?

A

Foods such as oily fish, particularly salmon, herring and tuna; egg yolk; liver; and dairy products including milk, cheese and butter.

137
Q

Exposure to the sun and vitamin D

A

-Exposing the human skin to UV light with a wavelength between 290-310 nm triggers the synthesis of vitamin D in the skin.

-Vitamin D is one of the few vitamins that can be made in the body and therefore does not really fit the definition of a vitamin.

-If your skin is exposed for a short time in the open air it is enough to supply your body with a daily dose of vitamin D.

-During winter time at very Northerly or Southerly latitudes, e.g. the north of Norway or in Patagonia, there is not enough sunlight to trigger the synthesis of vitamin D.

-Fortunately, a certain amount of vitamin D, which is fat soluble, can be stored by the liver.

138
Q

What is the reason that vitamin D is not, strictly speaking, a vitamin?

A

The human body can synthesise vitamin D by exposing the skin to UV light.

Vitamin D is one of the few vitamins that can be made in the body and therefore does not really fit the definition of a vitamin.

139
Q

Why is cholesterol important in the body?

A

-It is the precursor of bile acids, Vitamin D and steroid hormones such as progesterone and oestrogen.

-Furthermore, cholesterol protects the membrane integrity of animal cells.

-The presence of cholesterol in the cellular membrane enables the cell to change shape and move about.

140
Q

What is cholesterol in the blood an indicator of?

A

The risk of coronary heart disease.

141
Q

How much cholesterol does an average human liver produce per day?

A

-About 1g.

-In addition, some western diets add another 307 mg per day, which is above the recommended level by the Dietary Guidelines Advisory Committee.

142
Q

Table showing the recommended level of blood cholesterol that poses no elevated risk, as well as the elevated levels that do pose a risk for developing CHD

A
143
Q

The total cholesterol that is mentioned in the table is the sum of ___

A

Very Low Density Lipoprotein (VLDL), Low Density Lipoprotein (LDL) and High Density Lipoprotein (HDL).

144
Q

What is the only type of cholesterol that has been associated with an increased risk of developing CHD?

A

Only cholesterol contained in LDL.

145
Q

What are other factors (other than consumptino of cholesterol contained in LDL) that could play a role in being at risk for developing CHD?

A

Genetic factors or a lack of mobility.

146
Q

How can total blood cholesterol levels be changed?

A

Reducing the intake of dietary cholesterol can have a very limited effect on lowering total blood cholesterol levels, but drugs like statin have been shown to be far more effective.

147
Q

What are statins?

A

-A class of drugs used to lower cholesterol levels.

-The drug inhibits the enzyme HMG-CoA reductase, which catalyses the second step in the pathway from Acetyl CoA to cholesterol.

148
Q

What type of relationship is the relationship between saturated fat intake and total blood cholesterol levels?

A

A correlation and not a causal relationship.

149
Q

Which human organ synthesises cholesterol?

A

The liver.

150
Q

What is a balanced diet and what diet do most health departments reccomend?

A

-A balanced diet is a combination of foods that contains all essential and non-essential nutrients in the right proportion.

-The proportion is key here.

-Most health departments around the world have accepted that you should reduce your intake of fats in favor of increasing your intake of fruit and vegetables.

-The ‘wheel’ of foods shows the approximate proportion of the foods you should eat on a daily basis.

-The scientific evidence for this hypothesis is mainly based on epidemiological and statistical studies that look into the correlation between diet and the incidence of certain diseases such as CHD or various cancers.

151
Q

Picture of food wheel

A
152
Q

Recommended calorie intake

A

-Keeping your caloric intake to an accepted level is also healthy advice.

-In the International System of Units, energy is measured in joules (J).

-The kilojoule (kJ) is most often used for food-related quantities.

-A widely used but older unit of energy is the kilocalorie (kcal or Cal). 1 kcal = 4.184 kilojoules.

-The accepted values for caloric intake are 11,300 and 8,800 kJ for men and women (respectively) between the ages of 31 and 50.

153
Q

What is the unit used to measure energy and food-related quantities?

A

-In the International System of Units, energy is measured in joules (J).

-The kilojoule (kJ) is most often used for food-related quantities.

-A widely used but older unit of energy is the kilocalorie (kcal or Cal). 1 kcal = 4.184 kilojoules.

154
Q

What are the Recommended Dietary Allowances (RDA) in children?

A

Total calorie intake value (TCV): 120 to 160 kcal/kg of weight.

b) Proteins: 10 to 15% of the total calorie value (TCV), 3g/kg of weight for children.

c) Carbohydrates: 35 to 60% of the TCV.

d) Fats: 35 to 50% of the TCV.

e) Fibre: age in years + 5g (i.e. a four-year-old needs 9g of fibre per day).

155
Q

Factors influencing reccomendations for dietary intake

A

-The accepted values for daily intake (11,300 and 8,800 kJ) for men and women (respectively) between the ages of 31 and 50 are averages.

-Other factors influence this number such as how active you are, e.g. running three to five times per week, or living a sedentary lifestyle.

-In the latter case your caloric intake should be less.

156
Q

Use of databases to track diet

A

-There are many databases that include information on the nutritional content of different foods.

-To keep track of your caloric intake many websites and apps are available.

157
Q

Examples of 2 websites and apps used to track caloric intake

A

Dietplan and MyFitnessPal

158
Q

How can the energy content in food be measured?

A

-By burning a known mass of the food to test.

-The burning food is placed under the test tube with water.

-The heat liberated by the burning food is absorbed by a known volume of water.

-The rise in temperature is recorded.

159
Q

How is the energy value of a food calculated?

A

The energy value is calculated as temperature rise × mass of water × specific heat capacity of water (4.184 joules/gºC or 1 calorie/gºC).

160
Q

Diagram showing an experiment to calculate energy content in a peanut

A
161
Q

Give an example of how you would find the energy content of a peanut

A

-For example: you place 20 g of water that is at 20ºC in the test tube.

-You burn a peanut, and the temperature of the water is now 65ºC.

-Calculate the energy content in 100 g of peanuts.
______________________________________________________
Change in temperature: 45ºC

Mass of water: 20 g

Mass of one peanut: 0.5 g

Specific heat capacity of water: 1 calorie/gºC

Energy in 1 peanut = 45ºC × 20 g × 1 calorie/gºC = 900 calories

Energy per g of peanut = 900 calories/0.5 g = 1,800 calories/g

Energy in 100 g peanuts = 180,000 calories = 180 Kcal = 753 kJ

162
Q

In an experiment to determine energy content in different foods, these were burnt under a test tube containing water and the change in temperature was recorded.

What must be kept constant in this experiment?

A

Volume of water.

To compare the energy in foods, the volume of water must be kept constant. One calorie is the amount of energy needed to raise the temperature of one gram of water by one degree Celsius.

163
Q

Table showing the nutritional profile in 100g of different pulses

A
164
Q

State one reason that treatment of obesity with leptin in humans has not been successful.

A

-Most obese individuals overproduce leptin and have a diminished response to it.

-Therefore, treating them with additional leptin has little or no effect on weight, but has shown side effects including skin irritation.

165
Q

Identify the reason for vitamin D not being considered to be a typical vitamin.

A

Because it can be synthesized by humans «in skin»

166
Q

Adaptations of villi for absorption

A

-Protein channels / membrane pumps

-Large number of mitochondria, producing ATP for active transport across the phospholipid bilayer from the lumen of the intestine.

167
Q

Evaluate human milk as an overall source of essential amino acids

A

-It contains all of the essential amino acids

-Human milk has the same or more of essential amino acids except histidine and lysine compared to cow milk

-«limitation» human milk contains less histidine than both hen egg AND cow milk

IB HL Biology (68 decks)

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