22 Flashcards
‘ First Law of Thermodynamics
The total energy within a system is constant
Energy can neither be created or destroyed
Energy can be converted
Biology relies on energy conversions
Energy can neither be _____ or _______
Energy can be _______
Created
Destroyed
Converted
Biology relies on
Energy Conversions
Energy balances in cells and organisms
Hybrid
Food consist is of
Chemical energy:
- carbohydrates
- fats
- proteins
Nutrients:
- vitamins, minerals, etc
Individuals diets…
…vary
Through digesition we have the realise of …
…carbon components as carbon dioxide
Digestion of food components down into smaller units such as:
- glucose
- fatty acids
- proteins
- vitamins and minerals
(Makes them easier to absorb and is then circulated to different tissues)
- this process generates a certain amount of heat
After molecules are digested into the smaller components:
- large range of metabolic processes
Metabolism: - glycolysis
- B-oxidation (lipids - manages their resources, whether they are stored or taken up in diet)
- citric acid cycle
ATP - cellular work
Storage
- TAGS
- glyciogen
Evolved to intercorperate compounds into forms that are important for varieties celluluar functions and release some of the potential energy and get it into the form of ATP - makes energy available for cellular work
Carbon compounds in food are oxidised to form
ATP
What compounds in food car oxidised to form ATP?
Carbon compounds
Energy balcances in the body - Eintake = Eexpended + Estored
E stored in principlely lipid = weight gain
Obesity amount adults - stored energy
Weight loss can be achieved by:
- reduced energy intake (eat less and/or take certain drugs)
- increasing activities
- increasing basal metabolism
What is basal metabolism
The energy required for maintenance of life
What is leptin?
The peptide leptin is made in the fat cells, circulates in blood and signals to brain that enough energy is stored in the body, hence controls ‘hunger’
Joule (J) =
energy required to push against 1 Newton of force for 1 metre
1 cal =
4.184 J
1 Cal (kilocalorie) - capital C =
4.184 kJ
Daily dietary energy intakes and energy expenditure usually measured as
MJ ie 1000 kJ
The energy content of foods can be measured by
The energy content of foods can be measured by calorimetry
Atwater factors
Fat = 38 kJ/g
Carbohydrate = 17 kJ/g
Protein = 17 kJ/g
Ethanol = 29 kJ/g
(- under experimental conditions purified material is completely combusted - then able to measure the energy released from doing that combustion process - how to measure Atwater factors (typical energy value))
Why not all the energy in food is available
Losses in faeces ie fibre (cellulose B-glycosidic linkage can’t be hydrolysed )
Nitrogen is not oxidised (excreted in urine)
Have to adjust for these factors
Not all energy from food is available
Yeah
Yap
- range of energy across materials
- people consuming higher levels of high energy compounds- there is a bigger energy input that has to be balanced against energy required for activities and storage
Measuring energy expenditure: direct calorimetry - whole body calorimeters - what does it rely on measuring? What’s it good for determining?
Indirect calorimetry - what is it based on? How does it work? How much head is produced per mole of O2?
- based on O2 consumption and CO2 production measured using a respirometer
- a certain amount of energy is associated with every litre if O2 consumed
- Heat produced per mole of O2 = 2813/6 = 469 kJ/mol
- As 1 mol of O2 at STP = 22.4L
469 kJ / 22.4L = 20.9 kJ/L
(STP = standard temperature and pressure)
What are the two things an indirect calorimetry allows for?
- allows for calculation of energy expenditure for a wide range of activities
- also allows calculation of the ‘respiration exchange ratio’ (RER)
‘respiration exchange ratio’ (RER)
- calculation of energy expenditure for a specific individual in a specific energy state
The more robust the energy…
… the more energy consumed
RER can determine fuel is being used
(What is the flex between carbohydrate and lipid material in the body)
B asal metabolism
Energy required for maintenance of life:
Muscle contractions
Nerve conduction
Ion transport
Synthesis of macromolecules
Maintenance of body heat
Usually defined as energy expenditure at rest - changes depending on individuals
‘Basal metabolic rate’
Factors affecting basal metabolism include:
gender, age, body size and composition, genetics, hormonal status, stress levels, disease status, certain drugs
Basal metabolism, increased by
Athletic training Late stage of pregnancy Fever Drugs eg caffeine Hyperthyroidism
Basal metabolism, decrease by:
- malnutrition
- sleep
- drugs ie B-blockers
- hypothyroidism
Respirometers
