BIOL1008 Lecture Notes - Lecture 4: Basal Metabolic Rate, Lipid Droplet, Caffeine
Energy and Metabolism
Energy for the body
Food contains chemical energy in the bonds that
constitute carbohydrate, fat, protein and alcohol
Following digestion, the glucose, fatty acids etc.
can be used as fuel for cells
Cells must convert these fuels to ATP in order to
capture the energy and then use it
These reactions occur in a part of the cell called
mitochondria
Conversion of fuels to ATP requires oxygen and
liberated heat
Basic concepts (units of measurement)
Calorie (cal)= 4.2 J
Joule(J)= 0.24 cal
Kilocalorie (kcal)= 1000cal (often called calorie in popular media)
Kilojoule= 1000J
Different fuels supply different amounts of energy
Fat supplies the most
Then alcohol
Carbohydrates and protein
What is the body fuel
Metabolic rate or heat production can be determined by
oHow much oxygen (O2) is consumed
oHow much carbon dioxide is exhaled
Different fuels need different amounts of O2
oRatio of CO2 produced to O2 consumed
Respiratory quotient (RQ) or
Respiratory exchange ratio (RER)
How can we tell what fuel the body is using?
Fixed relationship between amount of fuel burnt (oxidised), oxygen consumed, and
the heat liberated
Same relationship if fuel is burnt (oxidised) in a test tube, or in the cell of a human
Carbohydrate as fuel
oGlucose + oxygen CO2 + water + heat
oRQ= 6/6 = 1
Fat as fuel
oFat (triglyceride) + oxygen CO2 + water + heat
oRQ= 57/80= 0.7
Mostly burning carbohydrates
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Body Energy Stores of Lean 70-kg man
oVast majority of fuel stores is
fatty tissue triglycerides
oCarbohydrates- glycogen from
liver and muscle
oRelatively low storage of
carbohydrates
Fuel use depends on duration and intensity of exercise
Rest and low intensity exercise
oMixture of carbohydrates and fat
High intensity exercise
oExclusively carbohydrate
Components of energy metabolism
Where does energy go
oResting (RMR) or basal metabolic rate (BMR)
oThermogenic effect of food
oExercise and physical activity
oNon exercise activity (NEAT)
Energy balance occurs when energy from fats, carbohydrates, protein and alcohol
are balanced by the above
Most energy is used to simply keep your body functioning
Resting or “basal” metabolic rate
Sum total of energy needed to keep body going (idling engine)
Conditions for measurement
oAt rest
oFasting
oThermal neutral zone (no energy for warming-up or cooling down)
oAdult (children are growing- energy demand)
oMostly just when you wake up
Magnitude of Resting/ basal metabolic rate
50-60% of total daily energy expenditure
Most of BMR used by small organs
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Document Summary
Food contains chemical energy in the bonds that constitute carbohydrate, fat, protein and alcohol. Following digestion, the glucose, fatty acids etc. can be used as fuel for cells. Cells must convert these fuels to atp in order to capture the energy and then use it. These reactions occur in a part of the cell called mitochondria. Conversion of fuels to atp requires oxygen and liberated heat. Kilocalorie (kcal)= 1000cal (often called calorie in popular media) Metabolic rate or heat production can be determined by: how much oxygen (o2) is consumed, how much carbon dioxide is exhaled. Different fuels need different amounts of o2: ratio of co2 produced to o2 consumed. Fixed relationship between amount of fuel burnt (oxidised), oxygen consumed, and the heat liberated. Same relationship if fuel is burnt (oxidised) in a test tube, or in the cell of a human. Carbohydrate as fuel: glucose + oxygen co2 + water + heat, rq= 6/6 = 1.
