Session 1 ILO's - Nutrition, diet and body weight

Question 1

List the components of daily energy expenditure

Answer 1

Energy:
• To support our basal metabolism - Basal Metabolic Rate (BMR)

• For voluntary physical activities

• Required to process the food we eat (diet-induced
thermogenesis).

Question 2

State the approximate daily energy expenditure for an adult male and female

Answer 2

With moderate physical activity:
• 70kg adult male ~12,000 kJ /day
• 58kg adult female ~9,500 kJ /day

Question 3

Define the Basal Metabolic Rate

Answer 3

i) The BMR is the energy required to maintain the resting activities of the body:

1. Maintenance of cells - ion transport & biochemical reactions
2. Function of organs
   30% - skeletal muscle (never fully relaxed)
   20% - brain/CNS
   20% - liver
   10% - heart
   20% - ‘other’
3. Maintaining body temperature
   Between 36.5-37.5

Question 4

Give approximate values to BMR and describe how it can be calculated

Answer 4

A rough estimate of BMR (in kcal/24hr) = 24 x weight in kg.
~7,000 kJ in a 70kg adult man (70 kg) and
~5,800 kJ for women (58 kg).

(1kcal = 4.18kj)
So from kcal to kj = x 4.18
From kj to kcal = / 4.18

Question 5

List 5 factors affecting basal metabolic rate

Answer 5

Factors affecting BMR:

•Body size (surface area)
•Gender
(males higher than female)
•Environmental temperature (increases in cold)
•Endocrine status
(increased in hyperthyroidism)
•Body temperature
(12% increase per degree)

Question 6

Define the energy required for voluntary physical activity

Answer 6

• Depends on intensity and duration of activity
- Reflects energy demands of:

• Skeletal muscle
• Heart muscle
• Respiratory muscles

Question 7

Explain how you can obtain a rough estimate of the daily energy required for physical activity, depending on the level of activity done

Answer 7

• 30% of the BMR for a sedentary person ( approx 30 kJ/Kg/day)

• 60-70% of the BMR for a person who engages in ~2hr of moderate exercise a day (approx 65 kJ/Kg/day)

• 100% of the BMR for a person who does several hours of heavy exercise a day. (approx 100kJ/Kg/day)

Question 8

Define Diet-induced thermogenesis

Answer 8

• The energy require to process food:
• Metabolic rate increases, following the ingestion of food
• Because energy is required to digest, absorb, distribute and store nutrients.

Question 9

Give approximate values for diet-induced thermogenesis

Answer 9

~10% of the energy content of the ingested food.

Question 10

List the essential components of the diet and explain why they are essential.

Answer 10

• Carbohydrate – provides energy needed for cell function.

• Protein - needed to supply essential amino acids.

• Vitamins & Minerals - needed to prevent signs and symptoms of deficiency states.

• Lipid - needed to supply essential fatty acids, reduces bulk of diet.

• Water - needed to replace water lost in sweat, urine, faeces and breath.

• Unrefined carbohydrate (Fibre) - required for normal GI tract function.

Question 11

Explain the clinical consequences of protein deficiency

Answer 11

• Protein deficiency results in an inadequate intake of essential amino acids.
• This leads to a reduced rate of synthesis of proteins and other nitrogen containing compounds.

Question 12

Explain the clinical consequences of protein & energy deficiency/starvation in adults

Answer 12

In adults: (3)

Energy deficiency/starvation:
- Causes weight loss due to subcutaneous fat and muscle wasting
- Complain of cold and weakness
- Infections of the GI tract & lungs are common

Protein deficiency: (3)

• Leads to symptoms of fatigue and weakness
• Recurrent viral or bacterial infections
• Brittle nails and dry skin etc.

Question 13

Explain the clinical consequences of energy deficiency/starvation in children

Answer 13

Energy deficiency: (7)

• Marasmus = type of protein-energy malnutrition, most commonly seen in children under 5
• Child looks emaciated (abnormally thin or weak)
• Obvious signs of muscle wasting and loss of body fat
• No oedema
• Hair is thin and dry
• Diarrhoea is common
• Anaemia may be present

Question 14

Explain the clinical consequences of protein deficiency in children (7)

Answer 14

Protein deficiency: (7)

• Kwashiorkor = typically in a young child displaced from breastfeeding by a new baby and fed a diet with some carbohydrate, but a very low protein content, such as cassava.
• The child is apathetic (showing or feeling no interest, enthusiasm, or concern), lethargic and anorexic (loss of appetite).
• Distended abdomen owing to hepatomegaly (enlarged liver) and/or ascites (accumulation of fluid in peritoneal cavity).
• The serum albumin is always low
• Anaemia is common
• There is generalised oedema and typically “pitting oedema
• Insufficient amino acids for the liver to make a normal level of blood proteins such as albumin, ultimately leading to oedema

Question 15

What are the signs and symptoms / clinical consequences of protein and energy deficiency in humans? (8)

Answer 15

ONGIIIAF

• Growth failure (height and weight below normal).

• Impaired physical development (tiredness, weakness and poor exercise tolerance due to reduced muscle mass).

• Impaired mental development (low IQ).

• Negative nitrogen balance due to Nin < Nout

• Oedema due to reduced albumin synthesis in the liver.

• Increased risk of infection due to reduced immunoglobulin synthesis.

• Anaemia due to reduced haemoglobin synthesis.

• Fatty liver due to reduced lipoprotein synthesis (so you fat can’t be transported from the liver, so it accumulates there)

Question 16

List the 9 essential amino acids (naming the pneumonic) & 3 a.a. that you need more of in children & pregnancy

Answer 16

If learnt, this huge list may prove truly valuable:

I - Isoleucine
L - Lysine
Th - Threonine
H - Histidine
L - Leucine
M - Methionine
P - Phenylalanine
T - Trytophan
V - Valine

Conditionally essential:
C - Cystine
A - Argenine
T - Tyrosine

Question 17

Determine the Body Mass Index of a patient and interpret the value.

Answer 17

Question 18

Define obesity

Answer 18

• Obesity is a chronic condition characterised by excess body fat.
• It is usually defined on the basis of determination of the Body Mass Index (BMI).

Question 19

Describe the factors involved in the regulation of body weight.

Answer 19

The balance between energy input and energy expenditure.

• Energy intake = expenditure = body weight stable

• Energy intake exceeds expenditure = energy stores (fat) will increase

• Energy expenditure exceeds intake = energy stores deplete

Question 20

List 6 chronic diseases for which obesity is a risk factor.

Answer 20

• Hypertension
• Cardiovascular disease
• Type 2 diabetes
• Gall bladder disease
• Osteoarthritis
• Cancer

Question 21

Define cell metabolism and explain its functions.

Answer 21

Metabolism is the set of processes which derive energy and raw materials
from food stuffs
and use them to support repair, growth and activity of the tissues of the body,
in order to sustain life

Question 22

Explain the functions of cell metabolism

Answer 22

Cells metabolise nutrients to provide:

• Energy/ATP for cell function and the synthesis of cell components

• Building block molecules that are used in the synthesis of cell components needed for the growth, maintenance, repair and division of the cell.

• Organic precursor molecules that are used to allow the inter- conversion of building block molecules (e.g. acetyl~CoA).

• Biosynthetic reducing power used in the synthesis of cell components (NADPH).

(Functions: support repair, growth, activity of the tissues to sustain life)

Question 23

Describe the relationship between catabolism and anabolism.

Describe anabolism

Answer 23

• Use energy released from
  catabolism (ATP) and intermediary metabolites to:
• Build larger molecules from smaller ones
• Reductive (use H released in catabolism)

Question 24

Describe the relationship between catabolism and anabolism.

Describe catabolism

Answer 24

• Break down larger molecules into smaller ones (intermediary metabolites)
• Release large amounts of free energy
• Oxidative (release H atoms) - ‘reducing power’

Question 25

Describe the relationship between catabolism and anabolism.

Answer 25

Anabolic pathways use the energy (ATP) and intermediary metabolites released from
catabolism to build larger molecules from smaller ones.

Question 26

What processes are catabolism used for?

Answer 26

• Oxidative pathways
• Detoxification
• Fuel mobilisation

Question 27

What processes are anabolism used for?

Answer 27

• Biosynthetic pathways
• Fuel storage

Question 28

Explain why cells need a continuous supply of energy.

Answer 28

Cells need a constant supply of energy to do work. This work generates and maintains the biological order that helps keep them alive.

Cells need energy continuously to be able to do various types of work:
1. Biosynthetic work
2. Transport work - maintain ion gradients & nutrient uptake
3. Specialised functions i.e. mechanical work in muscle contraction etc.

Question 29

List the fuel molucules that can be used by cells.

Answer 29

• Glucose
• Fatty acids
• Amino acids
• Ketone bodies
• Lactate
• Glycerol
• Alcoho

Question 30

What does oxidation involve?

Answer 30

• Loss of electrons (e-) / H-atoms (H+ + e-)

OR

• The addition of oxygen

Question 31

What does reduction involve?

Answer 31

• Addition of electrons (e-) / H-atoms (H+ + e-)

OR

• The removal of oxygen

Question 32

What is a redox reaction?

Answer 32

A reaction that has an oxidation reaction component and reduction reaction component (when an oxidative process is being coupled to a reductive process)

Question 33

Why are redox reactions important?

Answer 33

• Redox reactions are important because they are the principal sources of energy on this planet, both natural/biological and artificial

Question 34

Describe what happens in a redox reaction.

Answer 34

• You take in fuels that are in quite a reduced state (they are high in carbon and hydrogen)
• Cells release the energy from fuel molecules by oxidation reactions

(- Oxidation reactions can’t happen in isolation, they need to be coupled with a reduction reaction )

The oxidation part:

• Oxidation involves the removal of electrons (e-) / H-atoms (H+ + e-)

OR

• The addition of oxygen
• When fuel molecules are oxidised, H-atoms are removed from them

The reduction part:

• This involves the transfer of these H atoms (removed from fuels) to H-carrier molecules (that become reduced)
• The reduction reaction consists of the production of reduced forms of Hydrogen carrier molecules
• That reducing power/energy carried in those hydrogen carrier molecules is used for:

-ATP Production (NADH + H+) (FADH2) - in oxidative phosphorylation

• Biosynthesis (NADPH)
• In that process, the H-carrier molecules go back to their oxidised form, and you have a cycle.

Question 35

What are H carrier molecules comprised of?

Answer 35

B vitamins

Question 36

State the oxidised and reduced form of:
- NAD
- NADP
- FAD

Answer 36

Question 37

Explain the roles of redox reactions and H-carrier molecules in metabolism

Answer 37

Redox reactions are a way of harnessing the reducing power, to then power other reactions and it uses H-carrier molecules to do this
1. Directly e.g. use of NADPH in biosynthesis
2. Indirectly e.g. mitochondrial system to couple NADH to the produce ATP = key!

Question 38

Name the H-carrier molucules

Answer 38

NAD, NADP, FAD

Question 39

Explain the roles of H-carrier molecules in metabolism.

Answer 39

• When fuel molecules are oxidised, you are generating reducing power, which is carried by H-carrier molecules, in the form of electrons and protons
• Basically, the purpose of them is to act as carriers of reducing power.
• This reducing power is used for:
• ATP Production (NADH + H+) (FADH2) - in oxidative phosphorylation
• Biosynthesis (NADPH)

Question 40

What kind of molecules are H-carrier molecules?

Answer 40

Co-enzymes and co-factors

Question 41

Explain the biological roles of ATP

Answer 41

• ATP is an energy currency molecule, with the energy being stored in the phosphate bond and can be used to drive all sorts of chemical processes of a cell
• Carrier of free energy, not a store
• ATP is a high energy signal. If ATP is high, anabolic pathways are activated

Question 42

Explain the biological roles of creatine phosphate and other molecules containing high energy of hydrolysis phosphate groups.

Answer 42

In muscle cell creatine and creatine phosphate are related by the following reversible reaction catalysed by the enzyme creatine kinase:

Creatine phosphate + ADP ↔ ATP + creatine

When the concentration of ATP is high it can be used to drive the synthesis of creatine phosphate from creatine. ATP can then be regenerated by the reverse reaction when its concentration falls.
Creatine phosphate can thus act as a small store of free energy in muscle cells (skeletal and cardiac). This store is important in the first few seconds of vigorous muscle activity such as sprinting.

• That energy is available for cells to use, at very short notice (high energy, quick release, immediate)

Question 43

Explain why creatine phosphate kicks in sometimes

Answer 43

• Normally, excess energy is stored in the form of polymer macromolecules of fuel molecules ie glycogen, triglyceride
• These fuel molecules can go through oxidation in order to generate energy but this takes time
• when demand increases and metabolic activity increases very quickly, ie in sprinting, your muscles run out of ATP very very quickly and not enough oxygen is getting yo the muscles to generate energy by oxidative phosphorylation
• Thus other molecules take over the ATP production for a short period of time, and they act as a high energy store
• The most important one is creatine phosphate

Question 44

Explain the roles of high-and low-energy signals in the regulation of metabolism

Answer 44

Cells have sophisticated pathways that enable them to switch between anabolic pathways and catabolic pathways, depending on the energy status of the cells.

High energy signals cause the cell to switch to anabolic pathways to begin storing the energy as fuel molecules and for repair

Low energy signals will cause the activation of catabolic pathways, which leads to more energy production.

(Not the absolute concentrations of these molecules that are important, but the ratios between oxidised and reduced forms)

Question 45

Give 5 examples of high energy signals and what they cause

Answer 45

• ATP
• NADH
• NADPH
• FADH2

This will cause the cell to switch to anabolic pathways to switch to storing the energy as fuel molecules and for repair

Question 46

Give 5 examples of low energy signals and what they cause

Answer 46

• ADP
• AMP
• NAD+
• NADP+
• FAD

Activation of pathways that will lead to more energy production (Catabolic pathways)

Question 47

Describe what AMP is and how it works

Answer 47

• It is a low energy signal
• Adenylate kinase (myokinase) gets switched on when energy levels are dropping
• Myokinases takes 2 molecules of ADP, one of them gets converted to ATP, and the other gets converted to AMP
• AMP is a really important signal for switching on metabolic pathways, like glycolyis (thus it increases ATP generation (by glycolysis))
• AMP (and ADP) is also an important activator of AMP dependent kinase that regulates gene expression switching from anabolic to catabolic pathways

Question 48

What is creatine kinase often used as?

Answer 48

• Used clinically as a marker for muscle damage.
• When you get muscle damage, it gets released and starts to appear in serum
• Used to be used as a marker for cardiac muscle damage (e.g. myocardial infarction – but it is not very specific and has been superseded by cardiac specific troponin tests)

Question 49

Describe how creatinine is a useful clinical marker.

Answer 49

Measurements of the concentrations of creatinine in blood and urine can also be used as an indicator of kidney function since the kidney is normally very efficient at removing creatinine from the blood. Thus, an abnormally high blood creatinine with low urinary creatinine concentration may indicate reduced kidney function.

Question 50

List the major roles of the following tissues in whole body energy metabolism: CNS, heart muscle, skeletal muscle, liver & adipose tissue.

Answer 50

CNS
• Energy from glucose (also ketone bodies under certain conditions).
• No fuel storage therefore requires continuous supply of fuels and oxygen.

Heart Muscle
• Energy from glucose, lactate, fatty acids or ketone bodies.
• No fuel storage therefore requires continuous supply of fuels and oxygen.

Skeletal Muscle
• Energy from glucose, fatty acids or ketone bodies.
• Stores glucose as glycogen and some triacylglycerol.
• Muscle protein can be used in emergency.
• Can oxidise glucose to lactate under anaerobic
conditions.

Liver
• Energy from fatty acids, amino acids or alcohol. Can use galactose and fructose.
• Stores glucose as glycogen.
• Makes glucose from lactate, glycerol and amino acids.
• Makes ketone bodies, cholesterol and triacylglycerol.

Adipose tissue
• Energy from glucose or fatty acids.
• Stores fuel in the form of triacylglycerol.

Question 51

Mr D. a 56 year-old man was admitted to hospital for an exploratory abdominal operation. While surgery was in progress he suffered a coronary thrombosis (blockage of one or more of the coronary arteries), which led to cardiac arrest. Cardiac resuscitation managed to restart his heart after ~2 min and the surgery was concluded. Subsequent recovery was uneventful although there was evidence of cerebral dysfunction (e.g. loss of memory) and permanent damage to an area of his myocardium (heart muscle).
Explain, in outline, why cardiac arrest affects the heart and central nervous system more rapidly than it affects skeletal muscle.

Answer 51

Cardiac muscle and the central nervous system are functionally highly specialized tissues that do not contain significant stores of fuel or oxygen. In addition, they have very limited capacity for anaerobic metabolism. Thus, they require a continuous supply of fuel and oxygen that comes to them via the circulatory system.

Skeletal muscle is also a functionally highly specialized tissue. However, it does store significant amounts of fuel (glycogen) and oxygen (myoglobin). In addition, it has a limited capacity (~5 min) for anaerobic metabolism.

Any disruption in the supply of fuel and oxygen to the heart and CNS, such as that caused by a cardiac arrest, rapidly affects their ability to maintain intracellular ATP levels. This leads to reduced functional activity, failure to maintain ionic gradients (especially of Na+ and K+) and reduced membrane stability. This may produce permanent structural damage.

Skeletal muscle is less sensitive to the short-term disruption of its blood supply caused by a cardiac arrest as it has supplies of fuel and oxygen and can metabolise anaerobically for a few minutes. However, skeletal muscle will also eventually lose its ability to function if its blood supply does not return to normal.

Question 52

List the 9 essential amino acids (naming the pneumonic) & 3 a.a. that you need more of in children & pregnancy

Answer 52

If learnt, this whole list may prove truly valuable

I - Isoleucine
L - Lysine
Th - Threonine
H - Histidine
L - Leucine
M - Methionine
P - Phenylalanine
T - Trytophan
V - Valine

(Extras)
C - Cystine
A - Argenine
T - Tyrosine