Background Lecture and Nutrition, Diet & Body Weight

Question 1

What is metabolism?

Answer 1

A set of processes which derive energy and raw materials from foodstuffs and use them to support repair, growth and activity of the tissues of the body to sustain life.

Question 2

What are catabolic processes?

Answer 2

Those that break down molecules to release energy in the form of ‘reducing power’ (oxidative - release H atoms), which drives anabolism?

Question 3

What is anabolism?

Answer 3

A set of processes which use energy and raw materials to make larger molecules for growth and maintenance.

Question 4

Fuel molecules are metabolised to provide what?

Answer 4

Building block materials, organic precursors, biosynthetic reducing power and energy for cell function.

Question 5

What is energy?

Answer 5

The capacity to do work, whether it be biosynthetic, transport or specialised, such as mechanical, electrical or osmotic work.

Question 6

What is the standard international unit for energy and how is this different when discussing nutrition?

Answer 6

Joules/kJ, but ‘calories’ are more commonly used by patients when referring to kilocalories. 1kcal = 4.2kJ.
Fat has the most, then alcohol, carbohydrates and proteins.

Question 7

What happens to the excess if energy intake>energy required?

Answer 7

It may be stored as growth with the synthesis of new tissue as a means of repair, or new material for children or pregnant women. Alternatively it is stored as adipose tissue.

Question 8

How long can a person survive with just water?

Answer 8

20-70 days.

Question 9

Energy exists in interconvertible forms, which type is used predominantly by the body?

Answer 9

Chemical bond energy drives energy requiring activities. It is used directly without prior conversion to heat, as man in isothermal.

Question 10

Which type of reactions release energy and which require it?

Answer 10

Endergonic reactions, found in anabolism, require energy whereas exergonic reactions found in catabolism release it.

Question 11

How can you tell which reactions will be spontaneous?

Answer 11

Mostly catabolic reactions with free energy(delta G)<0. Transition stage does need to be reached first though.

Question 12

How are standard free energy changes measured?

Answer 12

In kJ/mol or kcal/mol under standard conditions of 1 Atmosphere of pressure, 25 degrees celcius with 1 Molar concentrations of reactants/products and offer at a pH of 7.
It does not indicate rate.

Question 13

How is energy released from chemical bonds?

Answer 13

Via oxidation reactions - removal of electrons &/ protons.

Question 14

What happens when fuel molecules are oxidised?

Answer 14

Electrons/protons are transferred to carrier molecules e.g. Nicotinamide adenine dinucleotide or Flavin adenine dinucleotide.
H carriers are complex and contain B vitamins; they are converted to their reduced form by adding 2Hs (then 1 H+ dissociates into solution - not with FAD).

Question 15

What is meant by a ‘high energy’ bond of hydrolysis?

Answer 15

The phosphodiester bond in adenosine triphosphate(ATP), where energy is stored and released from when it is hydrolysed to make ADP + Pi.

Question 16

What’s the importance of cycles in metabolism?

Answer 16

There is a finite number of ADP and H carrier molecules in their reduced state, so these must be recycled to maintain a constant concentration in the cytosine or energy can’t be captured properly from exergonic reactions.

Question 17

Why is it important that ATP is stable in the absence of specific catalysts?

Answer 17

So the flow of energy can be controlled.

Question 18

When ATP concentrations are high, what does this mean for metabolic reactions?

Answer 18

Anabolic pathways are activated (converse is true for catabolic processes).

Question 19

What does adenylate kinase do?

Answer 19

Catalysts reaction when high concentrations of low energy signal ADP.
2ADP –> ATP + AMP

Question 20

Name two polymer macromolecules that energy may be stored in when supply exceeds demand.

Answer 20

Glycogen and triacyglycerol.

Question 21

What is skeletal muscle’s reserve of high energy stores that can be used immediately?

Answer 21

Creating phosphate.

Question 22

What does creating kinase do and how is it used as a diagnostic marker?

Answer 22

Catalysed reaction: creatine + ATP PCr + ADP. When ATP concentration is high, ‘phosphate bond energy’ may be stored in PCr.
Creating kinase is a marker of MI as it’s made of 2 subunits with different isoform combinations in different tissues. CK in a specific combination is released from damaged cardiomyocytes and may be seen in the blood after a few hours.

Question 23

What is creatinine and how is it used?

Answer 23

Creatinine is the product of the spontaneous breakdown of PCr/Cr at a constant rate and is excreted via the kidneys.
It can be used as a measure of muscle mass, as excretion per 24hrs is proportional to muscle mass of an individual. Also the concentration in urine is a marker of dilation and it can be used to measure true urinary loss of many substances, e.g. pregnancy hormones.

Question 24

Name the 7 essential components of nutrition and explain their purpose.

Answer 24

Carbohydrates - supply energy
Water - keeps hydrated
Fibre - necessary for normal function of GI tract
Vitamins - essential for life
Minerals - electrolytes to establish gradient/signal etc.
Protein - supply energy and amino acids
Fats - supply energy and essential fatty acids

Question 25

What’s the general formula of carbohydrates?

Answer 25

(CH2O) n - contains aldehyde or ketone groups (many OHs).

Question 26

What is an oligosaccharide?

Answer 26

3-12 sugar units joined by glycosidic bonds e.g. Dextrins

Question 27

What type of single sugar unit is glucose?

Answer 27

Hexose - 6 carbon atoms.

Question 28

Name the major dietary carbohydrates.

Answer 28

Starch (polymer for glucose storage in plants), sucrose (table sugar, glucose-fructose disaccharide), lactose (glucose-galactose), fructose, glucose (predominant sugar in human blood), maltose (glucose-glucose disaccharide) and glycogen (carbohydrate storage molecule in animals - polymer of glucose).

Question 29

Why can’t humans digest cellulose?

Answer 29

We do not have an appropriate enzyme for the beta-1,4 -glycosidic bonds.

Question 30

What are ‘essential amino acids’?

Answer 30

9 of the 20 amino acids used for protein synthesis in the body that can’t be made as themselves, so have to be obtained from diet.

Question 31

Name 4 of the 9 essential amino acids.

Answer 31

(If Learned This Huge List May Prove Truly Valuable)
Any 4 from:
Isoleucine, lysine, threonine, histidine, leucine, methionine, phenylalanine, tryptophan, valine.

Question 32

What does it mean if an amino acid is ‘conditionally essential’, can you give an example?

Answer 32

Need to be obtained from diet at times of high growth, e.g. during pregnancy or in children. Arginine, tyrosine and cysteine are examples.

Question 33

Why does fat contain more calories that the other food groups and what is another function, besides providing energy?

Answer 33

Triacylglycerols contain less oxygen (are more reduced) and so release more energy when oxidised.
They are also necessary for the absorption of fat soluble vitamins (A, D, E and K) and used to provide essential fatty acids - linolenic and linoleic acids.

Question 34

List some functions of mineral electrolytes?

Answer 34

Establish ion gradients, calcium and phosphorous for structure, signalling, enzyme cofactors and Fe is an essential component of haemoglobin.

Question 35

What are the health associations of diets low and high in fibre?

Answer 35

Diets low in fibre and linked with constipation and bowel cancer.
A high intake may reduce cholesterol and diabetes risk (because cholesterol is used to make bile salts, which fibre absorbed and it’s passed out through the faeces, instead of reabsorbed).

Question 36

What are DRVs?

Answer 36

Dietary reference values estimates the energy and nutrient amounts required by healthy groups of age groups in a population (also takes into account gender and physical activity).

Question 37

What are RNI, EAR and LRNI and what is there relationship?

Answer 37

Reference Nutrient Intake is used for proteins, vitamins and minerals.
Estimated Average Requirement is used for energy.
Lower Reference Nutrient Intake are values below which most would have insufficient amounts.
LRNI and RNI are both 2 standard deviations away from EAR on a graph with a Gaussian distribution.

Question 38

With moderate physical activity, what is the daily energy expenditure of the average 70kg male and 58kg female?

Answer 38

Male - 12,000kJ/day

Female - 9,500kJ/day

Question 39

What is daily energy expenditure a sum of?

Answer 39

BMR - basal metabolic rate - maintenance of cells, functions of organs (skeletal muscle ~ 30%), maintaining body temperature - affected by external temperature, body size, gender, age and endocrine status.
DIT - diet induced thermogenesis - energy required to process food.
PAL - physical activity level - depends on duration and intensity, reflecting the demands of heart, skeletal and respiratory muscles.

Question 40

What is obesity and name some of the chronic conditions it is a risk factor for?

Answer 40

Excessive fat accumulation in adipose tissue which impairs health - usually BMI>30. Associated risk of some cancers, cardiovascular disease and type 2 diabetes.

Question 41

What is BMI and what are some flaws of the system?

Answer 41

Body Mass Index used clinically to evaluate weight (kg/m2). Major weakness with muscular individuals being wrongly classified - may alternatively use waist:hip ratio.
<18.5 is underweight, then up to 24.9 is desirable, to 29.9 overweight, 30 upwards in obese, >35 - clinically so.

Question 42

Evidence has shown that body fat distribution is relevant, because ‘apple shaped’ fat around the abdominal viscera is associated with increased risk of what?

Answer 42

Insulin resistance, hyperinsulinism, type 2 diabetes, hypertension, hyperlipidaemia, stroke and premature death.

Question 43

How is malnutrition linked to Kwashiorkor disease?

Answer 43

Damage from low energy intake and deficiency diseases of nutrients come with low protein in the diet resulting in insufficient blood protein synthesis.Starling’s law of the capillary shows that a decrease in plasma’s oncotic pressure may lead to oedema.

Question 44

Why may blood metabolites be measured?

Answer 44

Readily obtained, inexpensive and available to compare to normal ranges.