Complete set of notes for this element in the Bristol A100 Pre-clinical course. This is everything you need to know to achieve 90% marks. It is presented in a simple question, simple answer layout. If you have any questions or if anything doesn’t make sense, email me at mh14782@my.bristol.ac.uk....
Table of Contents
ELEMENT 7 – NUTRITION & METABOLIC DISEASES ............................................................. 1
7.1: Selection of and Adequate Diet ........................................................................................... 1
7.2: Energy Balance and Bodyweight Control.............................................................................. 2
7.3: Dietary Carbohydrate I ........................................................................................................ 4
7.4: Dietary Carbohydrate II ....................................................................................................... 5
7.5 & 7.6: Dietary Lipids ............................................................................................................. 7
7.7 & 7.8: Dietary Protein ......................................................................................................... 12
7.9 & 7.10: Vitamins, Minerals and Trace Elements .................................................................. 16
ELEMENT 7 – NUTRITION & METABOLIC DISEASES
7.1: Selection of and Adequate Diet
• What is nutrition? The provision of macro and
micronutrients to support life
• What are the 3 macronutrients? Carbohydrates, fats and
proteins
• What are the 3 micronutrients? Vitamins, minerals and
trace elements
• What else is essential in the diet? Water and fibre
• What are the approximate percentages body Dietary reference values (As % of total)
composition of an average person?
Component Percentage composition
Water 60%
Fat 20%
Protein 15%
Mineral 5%
Carbohydrate <1%
• Which component is the most variable and how does it vary? Fat. It is the main factor contributing
to being overweight and varies with gender (women have more) and increases with age
• What is the basic metabolic rate, BMR? It’s the energy used by the body at rest, in kJ/min.
• When is the BMR measured? Awake, lying down, at a constant temperature, 12 hours after their
last meal
• What % of total energy consumption can be attributed to the BMR? 50-70%
• What is the thermic effect of food? The energy required for the digestion and absorption of food.
Energy is needed to synthesise enzymes and for gut motility.
• What % of total energy consumption can be attributed to the thermic effect of food? About 5-10%
• What is the physical activity ratio, PAR? A ratio used to determine the intensity of exercise. PAR =
metabolic rate during exercise/basic metabolic rate
• What is the PAR for sleeping? 0.9, which means that your metabolic rate is less when you sleep than
your BMR.
• What factors determine our energy requirements?
1. BMR
2. Thermic effect of food
, 3. Physical activity
4. Age
5. Gender
6. Disease
7. Pregnancy/lactation
• What is the respiratory quotient, RQ? The ratio of carbon dioxide produced to oxygen used in the
complete oxidation of a nutrient to carbon dioxide and water. RQ = CO2/O2
• What can be determines using the RQ? What fuel the subject is using, because their overall RQ will
be similar to the value of the RQ of a particular nutrient. In other words, if the RQ is close to 0.7, say,
then you know the subject is oxidising mostly fats, because the RQ of fats is 0.7.
• Prove that the RQ of carbohydrates is 1. The overall equation for the oxidation of carbohydrates is
C6H12O6 + 6O2 à 6H20 + 6CO2, therefore in molar terms 6CO2/6O2 = 1
• What methods are used in order to measure the RQ of a nutrient?
1. Indirect calorimetry – when you measure how much oxygen a
person is using and how much carbon dioxide is released
using an apparatus that keeps the system closed (see picture)
2. Doubly-labeled water technique – uses 2H218O, measuring
how much 2H is released (as water) and how much 18O is
released (as water or carbon dioxide)
• Which macronutrient has the most energy per gram and why? Fat
because it is very anhydrous (as its lipophilic/hydrophobic) and very reduced and therefore you get
more energy when you oxidise it.
7.2: Energy Balance and Bodyweight Control
• What common molecule are all macronutrients oxidised to before entering the TCA? Acetyl-CoA
• What happens to energy in our
diet/how much of it actually goes to
useful work and production of ATP? See
flow chart
• What is the largest fuel store in the
body? Fats, by far. You have about 14kg of
fat, but only about 0.5kg of
carbohydrate
• In the simplest terms, how do you put on
weight? Energy stored = energy intake – energy expended. Therefore when energy intake > energy
expended, you store energy and therefore put on weight.
• What methods are used to estimate how overweight you are?
1. BMI
2. Skinfold thickness - uses a caliper, which estimates fat content based on thickness of skin
3. Conductivity – fat conducts electricity differently to water and other body parts
4. Imaging
5. Waist: hip ratio
• What problems are there with using BMI as a measure of obesity?
1. Not good for short or tall individuals
2. Doesn’t differentiate between whether weight is due to muscle or fat (i.e. a muscly athlete
may appear obese)
3. Doesn’t comment on the site of the adipose tissue, as obesity in the abdomen is more
dangerous than if fat deposits in the limbs.
,• What two body shapes are there, described as pear
shaped and apple shaped? Gynoid (pear shaped – more
common in women **remember because you’d think
“guynoid” would be for guys, but its not, it’s common in
women**) and Android
• Which is more dangerous? Android, because it leads to fat
deposition around the abdomen, which is inherently
more dangerous than around the waist.
• Which cancers are thought to be linked with obesity?
Breast, colorectal, pancreatic, oesophageal.
• How quickly do you lose weight in food deprivation?
About 2kg in the first week as glycogen stores with
associated water are depleted. Then about 0.3kg/week as fat stores are used. Fats are a lot denser
and have more energy per gram so you lose weight more slowly.
• What treatments, both lifestyle and interventional, are there for obese patients?
Lifestyle Interventional
Change in diet (less fat & sugar, replacing Gut lipase inhibitor – blocks uptake of fat in
them for lower energy foods) the gut, leading to fat in the stool
(steatorrhoea), which causes some
unpleasant side effects.
Increase exercise Increase BMR – using thyroid hormones or
by stimulating brown adipose tissue
Appetite decreasing drugs (none in UK)
Surgery (bariatric gastric bypass)
• Why are white fat cells described as being an important endocrine organ? Because white adipose
tissue secretes hormones and cytokines.
• What is a cytokine? A small protein molecule involved in cell signalling
• Give three examples of cell regulator molecules/hormones that white adipose tissue secretes and
give their function.
1. Leptin – decreases appetite and increases energy expenditure. It’s a molecule released to try
and regulate/normalise how much fat stores you have. If you have a lot of fat, you’ll produce
a lot of leptin, have a suppressed appetite/expend more energy and in theory lose weight. If
you have too little fat stores, leptin isn’t produced a lot, so you have a larger appetite,
putting on weight. The reason this doesn’t work is because its thought that obesity leads to
leptin insensitivity.
2. Adiponectin – regulates fatty acid breakdown
3. Resistin – causes high levels of LDLs (that’s bad à CV disease)
• What is a dietary reference value (DRV)? The amount of nutrient required to maintain health
• What types of DRVs are there?
1. Estimated average requirement – enough nutrient for 50% of the population
2. Reference nutrient intake – enough for 97.5% of the population
3. Lower reference nutrient intake – enough for 2.5% of the population
• What’s the difference between the recommended daily amount (RDA) and guideline daily amount
(GDA)?
o RDA = the intake level that would meet 97.5% of healthy individuals
o GDA = a system set up in ’98 to help consumers understand nutritional information on
packets. They are a guide, as opposed to the RDA, which is a target.
• In what ways do the government make it easy to ascertain whether a food item is healthy or not?
Food labeling with ingredients and amounts of macronutrients, traffic light system and GDA/RDA
systems.
, 7.3: Dietary Carbohydrate I
• What’s the relationship between carbohydrate in diet and development? Poorer countries tend to
eat more carbohydrate because it’s more easily available.
• What is starch made of and what is the difference between these two molecules? Amylose and
amylopectin. Amylose is straight chained with its glucose monomers connected by α1,4-glycosidic
bonds. Amylopectin is branched and also has α1,6-glycosidic bonds at the branch points.
• Why is insoluble fibre important in the diet? It absorbs water, making stools softer, preventing
constipation.
• Why is soluble fibre important? It makes it less easy to absorb cholesterol
• In what way is fibre thought to protect against bowel tumours? Some bacteria in the gut can
digest/ferment some fibre to form volatile fatty acids, including butyric acid, which is thought to
protect against bowel cancer.
• Why do people who consume large amounts of sugar alcohols like sorbitol suffer from flatulence?
Its badly absorbed, and is fermented in the large bowel by bacteria, producing gas.
• What type of sweetener cant sufferers of phenylketonuria consume? Aspartame, because they are
unable to metabolise phenylalanine.
• How are polysaccharides digested? Rapidly digestible starch (RDR) and slowly digestible starch (SDS)
are digested by amylase in the small intestine. Resistant starch (RS) and non-digestible starch (NDS)
are fermented by the gut microflora, producing gas and flatulence.
• Why can’t cellulose be digested? It contains β1,4-glycosidic bonds, which isn’t acted on by amylase
• How are disaccharides digested? By disaccharidases, found on the brush border of the small
intestine.
• How are monosaccharides digested? They don’t need to be, they’re directly absorbed.
• What does the isomaltase enzyme do? Cuts the 1,6 linkages of α-limit dextrin
• What does the glucoamylase enzyme do? It’s a brush border enzyme, cutting the 1,4 linkages of α-
limit dextrin
• How does variation in digestibility occur in starch products? The way they’re processed and/or
cooked
• What is the glycaemic index? It’s a measure
of the relative increase in blood glucose
levels of standard 50g amounts of
carbohydrate containing foods compared to
glucose (i.e. change in blood glucose when
you eat test food compared to glucose). It
tells you something about digestibility
because the easier it is to digest, the faster
it will increase the blood glucose, the higher
the GI. GI = area under curve test food/area
under curve glucose.
• What are diabetes sufferers told with
regards to GI of the food they eat? That its
better to eat foods with a lower GI, because otherwise their blood glucose concentrations will spike
and they will become hyperglycaemic a lot more easily.
• How is glucose and galactose absorbed?
1. Via a secondary active transport mechanism – its absorbed via symport with sodium.
2. It then diffuses into the blood via a GLUT 2 transporter
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