Metabolic Fuels & Other Dietery Componenets

Question 1

Metabolic

Answer 1

Refers to the sum of the chemical reactions that take place within each cell of a living organism.

There is a sequence of chemical reactions: a particular molecule is converted into some other molecule or molecules in a defined fashion.

Question 2

Dietary components are metabolised in cells through 4 main pathways:

Answer 2

Biosynthetic- anabolic
Fuel storage- anabolic
Oxidative processes- catabolic
Waste disposal- either catabolic or anabolic

Question 3

Anabolic

Answer 3

synthesise larger molecules from smaller components

Anabolic pathways require energy which essentially comes from catabolic pathways in the form of ATP

This process produces ADP and Pi

Actions of insulin are anabolic

Question 4

Catabolic

Answer 4

break down larger into smaller

This process releases energy in the form of ATP and CO2 and heat

This process requires oxygen

Question 5

Xenobiotics

Answer 5

Compounds considered foreign to the body- not required as have nutritional value

Question 6

Biosynthetic pathways

Answer 6

Forms body components such as proteins

Question 7

Fuel storage pathways

Answer 7

Energy storing products

Question 8

Fuel oxidative pathways

Answer 8

Energy rich molecules are broken down with the release of energy

Question 9

Macronutrients

Answer 9

Enzymes require these to function

Cofactors are macronutrients

Cofactors include thymine (TPP)

Thymine is required to allow acetyl coA to enter the Krebs cycle and in the conversion of 5C to 4C

High carbohydrate requirement of the body means high requirement of TPP

Question 10

Adipose tissue

Answer 10

85% fat, storage of energy-rich molecules

Insulin increases the uptake of glucose by the adipose tissue to then store it as storage compounds such as triglycerides

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Question 11

Liver

Answer 11

metabolically active (e.g. Gluconeogenesis, removal of toxins)

Metabolism of xenobiotics to get them into a state for the removal of these foreign compounds out of the body

The liver also takes up lactate and converts it to pyruvate

Insulin promotes the synthesis of fatty acids in the liver which then move into adipose tissue for storage

Question 12

Muscle

Answer 12

Activity-uses fuel to provide kinetic energy

Question 13

3 main deuterium energy sources

Answer 13

● Carbohydrates

● Lipids

● Proteins

Question 14

Energy currency of the cell is

Answer 14

ATP

Question 15

Proteins

Answer 15

● Amino acids in chains
● Carbon
● Oxygen
● Hydrogen
● Nitrogen (16% by weight)

Question 16

Lipids

Answer 16

● Triacylglycerols
(triglycerides)
● 3 fatty acids esterified to one glycerol moeity
● More reduced than other energy sources
● “saturated” with hydrogen

Question 17

Storage of Dietary Fuels

Answer 17

● Fat - Adipose tissue (only 15% water)

● Carbohydrate – as glycogen in liver and muscles

● Protein - Muscle (80% water)

Question 18

What happens to excess energy intake?

Answer 18

Store as triglycerides in adipose (approx 15kg),

Store as glycogen (up to 200g in liver & 150g in muscle), 80g in the liver after overnight fast,

Store as protein in muscle (approx 6kg).

Question 19

The oxidative system

Answer 19

The oxidative system (aerobic) is the primary source of ATP supplied to the body at rest and during low intensity activities and uses primarily carbohydrates and fats as substrates.

Question 20

Basal Metabolic Rate (BMR)

Answer 20

Energy needed to stay alive at rest

A measure of the energy required to maintain non-exercise bodily functions such as;
● respiration,
● contraction of the heart muscle,
● biosynthetic processes,
● repairing & regenerating tissues,
● ion gradients across cell membranes

BMR = 1kcal/kg body mass/hr (24kcal/kg/day), an adult requires approximately 0.8g/kg ideal body weight protein per day

Question 21

Conditions essential for measuring BMR

Answer 21

• Post-absorptive (12 hour fast)
• Lying still at physical and mental rest
• Thermo-neutral environment (27 – 29oC)
• No tea/coffee/nicotine/alcohol in previous 12 hours
• No heavy physical activity previous day
• Establish steady-state (~ 30 minutes)

If these conditions are not met, referred to as REE

Question 22

Factors decreasing BMR

Answer 22

● Age (as you get older, BMR decreases)
● Gender (female have lower BMR since they have less metabolically active tissues)
● Dieting/Starvation
● Hypothyroidism (less thyroid hormone = lower BMR)
● Decreased muscle mass

Question 23

How do thyroid hormones affect BMR

Answer 23

Thyroid hormones regulate metabolic rate, core body temperature, appetite, sympathetic activity and more

Question 24

How do muscle cells affect BMR?

Answer 24

Muscle cells require more energy to maintain than fat cells, so people with a higher muscle to fat ratio tend to have a higher BMR.

As we get older, we tend to gain fat and lose muscle. This explains why the BMR tends to decrease with age.

Question 25

Factors affecting BMR/ REE

Answer 25

● Body weight (BMI)
● Hyperthyroidism
● Low ambient temp.
● Fever/infection/chronic disease

Question 26

Equations for estimating BMR in health

Answer 26

• Harris Benedict Equations (1919)
• Schofield Equations (1985)
• Henry equations (2005)

Rough estimate: ~1kcal/kg body mass/hour

Question 27

Example of Henry equation (Henry, 2005).

Answer 27

Equation for estimating basal metabolic rate from gender, age and weight; (formulae & examples are for interest);

Example: (70 kg X 16) + 545 = 1665 kcal/day (BMR)

Slide. 48

Question 28

Henry equation (2005)- with or without height

Answer 28

in the clinical setting height can be difficult to obtain or include in calculations, & other variables may negate the advantage of including height

Adjust for metabolic stress

Adjust for activity and maybe diet-induced thermogenesis (DIT), for example in healthcare;

Question 29

Starvation- overnight fast

Answer 29

● ↓insulin
● Glycogenolysis

The brain requires about 150 g of glucose a day.

After an overnight fast the liver only has about 80g glycogen

During a longer period of fasting/starvation, glucose must be formed from non-carbohydrate sources - gluconeogenesis

Question 30

Starvation- 2-4 days

Answer 30

● ↓insulin
● ↑cortisol
(Lipolysis & proteolysis)

Gluconeogenesis uses
● Lactate
● Amino acids
● Muscle
● Intestine
● Skin
● Glycerol- ● Fat breakdown

Question 31

Starvation- >4days

Answer 31

● Liver → ketones from fatty acids,

● Brain adapts to using ketones,

● ↓BMR = accommodation.

Question 32

Define Malnutrition

Answer 32

A state of nutrition with a deficiency, excess or imbalance of energy, protein or other nutrients, causing measurable adverse effects

Question 33

Adverse effects of malnutrition

Answer 33

Adverse effects are on tissue/body form (shape, size, composition), body function and clinical outcome.

Question 34

Re-feeding syndrome:

Answer 34

● Re-distribution of phosphate, potassium, magnesium etc due to insulin

● Switch back to carbohydrates as the main fuel which requires phosphate and thiamine.

Question 35

Micronutrients

Answer 35

-Trace elements and vitamins

● Co-factors in metabolism
● Gene expression
● Structural components
● Antioxidants

Question 36

Essential vitamins

Answer 36

Vitamin c
Vitamin B12
Vitamin B1
Vitamin D

Question 37

Vitamin C

Answer 37

● Ascorbic acid
● Fruit and vegetables
● Heat labile
● Collagen synthesis
● Improve iron absorption
● Antioxidant

Question 38

Vitamin B12

Answer 38

● Protein synthesis
● DNA synthesis
● Regenerate folate
● (and therefore – cell division)
● Fatty acid synthesis
● Energy production

Question 39

Vitamin B1

Answer 39

Helps with energy production in your body

Question 40

Vitamin D

Answer 40

Increases the amount of calcium and phosphorus your body absorbs from foods.

Question 41

Prudent diet

Answer 41

● 5+ servings fruit/veg
● Base your meals around starchy carbohydrate foods,
● no more than 5% of the energy we consume should come from free sugars
● 0.8g/kg/day protein
● The average man should have no more than 30g saturated fat a day, & women 20g.
● Adults should have no more than 2.4g of sodium per day, which is equal to 6g of salt.
● Men and women are advised not to regularly drink more than 14 units of alcohol a week (over >3 days).
● Avoid excess dietary supplementation
● Adequate Calcium

Question 42

Dietary energy sources

Answer 42

Carbohydrates (4kcal/g),
Protein (4kcal/g),
Alcohol (7kcal/g)
Lipid (9kcal/g - gives the most energy per gram)

Question 43

Alcohols

Answer 43

typically ethanol, highly energetic

Question 44

Factors increasing BMR

Answer 44

high BMI
hyperthyroidism
low ambient temperature
fever/infection
pregnancy (due to increase in weight and thyroid hormone)
exercise

Question 45

Daily energy expenditure (DEE)

Answer 45

Energy to support our BMR and our physical activity + energy required to process food we eat (diet induced thermogenesis)

Question 46

Storage of excess energy

Answer 46

• Stored as triglycerides (excess lipid) (approx 15kg)

• Stored as glycogen (excess glucose) (approx 200g in liver & 150g in muscle)

• Stored as protein (approx 6kg)

• Carbohydrates account for 30% of ATP production at rest

• Lipids account for 70% of ATP production at rest

• Proteins are often used in longer periods of starvation

Question 47

ATP

Answer 47

• ATP > Energy utilisation (biosynthesis or macromolecules, muscle contraction, active ion transport and thermogenesis)

ADP + Pi > Respiration (energy production from carbohydrate, lipid & protein, O2 IN and CO2 OUT > ATP