Human nutrition

Question 1

nutrient

Answer 1

a chemical substance found in foods that is used in the human body

Question 2

classes of nutrients

Answer 2

carbohydrates, proteins, lipids, vitamins, minerals and water

Question 3

essential nutrients

Answer 3

• cannot be synthesised by the body

- must be ingested as part of the diet

Question 4

Non-essential nutrients

Answer 4

can be made by the body or have a replacement nutrient which serves the same dietary purpose

e.g. Carbohydrates are not considered essential nutrients as human diets can obtain energy from other sources without ill effect

Question 5

causes of malnutrition

Answer 5

caused by an improper dietary intake of nutrients:
e.g. overnutrition (too much) or undernutrition (not enough)

caused by the inadequate utilisation of nutrients by the body – e.g. due to illness or disease

Question 6

malnutrition

Answer 6

health condition caused by a deficiency, imbalance or excess of nutrients in the diet

Question 7

symptoms of malnutrition

Answer 7

stunted growth (height too short regarding the age)
wasting (undernutrition)
obesity (over nutrition)

Question 8

energy content of food

Answer 8

estimated by burning a sample of known mass and measuring the energy released via calorimetry

Combustion of the food source causes the stored energy to be released as heat, which raises the temperature of water

Energy (joules) = Mass of water (g) × 4.2 (J/gºC) × Temperature increase (ºC)

Question 9

errors in calorimetry

Answer 9

caused by the unwanted loss of heat to the surrounding environment;

The food sources should be burnt at a constant distance from the water to ensure reliability of results

The initial temperature and volume of water should also be kept constant

Question 10

comparing energy content

carbohydrates, lipids (fats) and proteins

Answer 10

Carbohydrates - preferentially used as an energy source because they are easier to digest and transport

Lipids- can store more energy per gram but are harder to digest and transport (hence are used for long-term storage)

Protein metabolism produces nitrogenous waste products which must be removed from cells

Question 11

amino acids

Answer 11

20 in total

monomeric building blocks from which proteins are constructed

Lack of essential amino acids affects the production of proteins

Question 12

Conditionally non-essential amino acids

Answer 12

can be produced by the body, but at rates lower than certain conditional requirements (e.g. during pregnancy or infancy) – they are essential at certain times only

Question 13

phenylketonuria

Answer 13

genetic condition that results in the impaired metabolism of the amino acid phenylalanine

autosomal recessive disease caused by a mutation to the gene encoding the enzyme phenylalanine hydroxylase

Phenylalanine hydroxylase (PAH) normally converts excess phenylalanine within the body into tyrosine

In PKU patients, the excess phenylalanine is instead converted into phenylpyruvate (phenylketone)
result = a toxic build up of phenylketone in the blood and urine (phenylketonuria)

Question 14

diagnosis of PKU

Answer 14

Untreated PKU can lead to brain damage and mental retardation

Infants with PKU are normal at birth because the mother is able to break down phenylalanine during pregnancy

Diagnosis is made by a simple blood test for elevated phenylalanine levels shortly after birth

Question 15

treatment of PKU

Answer 15

enforced strict diet to restrict the intake of phenylalanine and prevent its build up within the body

low-protein diet

diet supplemented with a medical formula containing precise quantities of essential amino acids

Question 16

essential (cis)-polyunsaturated fatty acid

Answer 16

Alpha-linolenic acid (an omega-3 fatty acid)

linoleic acid (an omega-6 fatty acid)

humans lack the enzyme required to introduce double bonds at the required position of the carbon chain

found in fish, leafy vegetables and walnuts

Question 17

significance of fatty acids

Answer 17

modified by the body to make important lipid-based compounds (such as signalling molecules)

fatty acid deficiency may be linked to impaired brain development (e.g. depression) and altered maintenance of cardiac tissue (e.g. abnormal heart function)

Question 18

Fats and cholesterol

Answer 18

cannot dissolve in the bloodstream, are packaged with proteins (to form lipoproteins) for transport

Low density lipoproteins (LDLs) carry cholesterol from the liver to the body (hence raise blood cholesterol levels)

High density lipoproteins (HDLs) carry excess cholesterol back to the liver for disposal (hence lower blood cholesterol levels)

Question 19

fatty acids and cholesterol in the bloodstream

Answer 19

Saturated fats increase LDL levels within the body, raising blood cholesterol levels

Trans fats increase LDL levels and lower HDL levels, significantly raising blood cholesterol levels

Cis-polyunsaturated fats raise HDL levels, lowering blood cholesterol levels

Question 20

high cholesterol levels

Answer 20

harden and narrow arteries (atherosclerosis)

highgh levels of LDL = LDL particles form deposits in the walls of the arteries
The accumulation of fat within the arterial wall leads to the development of plaques which restrict blood flow

coronary arteries become blocked=coronary heart disease (CHD) + heart attacks and strokes

Question 21

vitamins

Answer 21

chemically diverse carbon compounds that cannot be synthesised by the body

function as cofactors, antioxidants or hormones

absence may cause a deficiency disease

Question 22

categories of vitamins

Answer 22

Water soluble vitamins, any excess is lost in urine (e.g. vitamins B, C)

Fat soluble vitamins can be stored within the body (e.g. vitamins A, D, E, K)

Question 23

ascorbic acid

Answer 23

vitamin C

In mammals- functions as a potent antioxidant, plays an important role in immune function

involved in the synthesis of collagen (a structural protein), synthesis of lipoproteins

made internally by most mammals from monosaccharides, except humans

Question 24

ascorbic acid deficiency

Answer 24

scurvy - a general weakening of normal immune function

Question 25

Vitamin C deficiency symptoms

Answer 25

S kin discolouration, bruising
H emorrhaging 
A naemia
D ental issues
E xhaustion 
S welling of joints

= S H A D E S

Question 26

Vitamin D deficiency

Answer 26

In the absence vitamin D, Ca & P are not absorbed, but excreted in the faeces

affects bone mineralisation

causes :
rickets (deformation of bones)
osteomalacia (softening of bones)

Question 27

vitamin D

Answer 27

involved in the absorption of calcium and phosphorus
contributes to bone mineralisation

stored by the liver for when levels are low

Individuals with darker skin pigmentation produce vitamin D more slowly and hence require greater sun exposure

Question 28

Symptoms of Vitamin D Deficiency (Rickets)

Answer 28

B one fragility 
A trophy/ muscle weakening
D dental problems
G growth retardation 
E enlargement of liver
S keletal deformities

= B A D G E S

Question 29

minerals

Answer 29

chemical elements required as essential nutrients by organisms

essential – e.g. C, H, O, N, S

deficiency= disorder

Question 30

functions of minerals

Answer 30

Major constituents of structures such as teeth and bones (e.g. Ca, P, Mg)

Important components of body fluids (e.g. Na, K, Cl)

Cofactors for specific enzymes or components of proteins and hormones (e.g. Fe, P, I)

Question 31

minerals and plant development

Answer 31

Magnesium - component of chlorophyll (required for photosynthesis)

Potassium -an inorganic salt found within the sap of a plant (maintains water potential)

Calcium - important for plant root and shoot elongation

Question 32

appetite control

Answer 32

situated in the centre of hypothalamus

controlled by hormones produced in the pancreas, stomach, intestines and adipose tissue

hormones send messages to the appetite control centre of the brain (within the hypothalamus)

Hormonal signals either trigger a feeling of hunger (promote feasting) or satiety (promote fasting)

Question 33

release of hormone

Answer 33

Stretch receptors in the stomach and intestine become activated when ingested food distends these organs

Adipose tissue releases hormones in response to fat storage

The pancreas will release hormones in response to changes in blood sugar concentrations

Question 34

hormones that either stimulate or inhibit the appetite

Answer 34

trigger a hunger response: ghrelin (from stomach) and glucagon (from pancreas)
trigger a satiety response include leptin (from adipose tissue) and CCK (from intestine)
Hint: Ghrelin Grows Hunger ; Leptin Lowers Hunger

Question 35

Obesity

Answer 35

more likely to suffer from hypertension (abnormally high blood pressure)

Excess weight places more strain on the heart to pump blood, leading to a faster heart rate and higher blood pressure
High cholesterol diets will lead to atherosclerosis, narrowing the blood vessels which contributes to raised blood pressure
Hypertension is a common precursor to the development of coronary heart disease (CHD)

type II diabetes (non-insulin dependent)
occurs when fat, liver and muscle cells become unresponsive to insulin (insulin insensitivity)
This typically results from a diet rich in sugars causing the progressive overstimulation of these cells by insulin
Hence overweight individuals who have a high sugar intake are more likely to develop type II diabetes

Question 36

starvation

Answer 36

As the body is not receiving a sufficient energy supply from the diet, body tissue is broken down as an energy source
This leads to muscle loss (as muscle proteins are metabolised for food) and eventually organ damage (and death)

Question 37

anorexia nervosa

Answer 37

Blood flow is reduced and blood pressure may drop as heart tissue begins to starve
The heart may also develop dangerous arrhythmias and become physically diminished in size

Question 38

a deficient intake of proteins

Answer 38

kwashiorkor

a disorder that causes oedema, irritability, anorexia, ulcerating skin, and an enlarged liver.

Question 39

omega-3 fatty acids functions in body

Answer 39

controlling blood clotting and building cell membranes in the brain

Question 40

conditionally essential amino acids

Answer 40

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

Arginine cannot be synthesised by infants so it must be present in the diet as well.

Question 41

iron

Answer 41

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

Question 42

arsenic

Answer 42

necessary ultra-trace element for humans

Question 43

iodine

Answer 43

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

Question 44

Sodium and potassium

Answer 44

propagation of the nerve impulse.

Question 45

Calcium

Answer 45

muscle contraction

Question 46

anaemia

Answer 46

(vitamin B12 deficiency),

Question 47

beriberi

Answer 47

vitamin B1 deficiency

Question 48

pellagra

Answer 48

vitamin B3 deficiency

Question 49

scurvy

Answer 49

vitamin C deficiency)