Lecture 22: ENERGY BALANCE IN CELLS AND ORGANISMS Flashcards
What is in the first law of thermodynamics?
The total energy within a system is constant, energy can neither be created or destroyed, energy can be converted and biology relies on energy conversions
Where does energy first come from?
The sun
Where does energy from the sun go?
To plants for photosynthesis
What is released from photosynthesis?
Oxygen
What is oxygen used for?
Respiration
What is the result of respiration?
Energy to use in anabolism, movement and transport
What is the result of using energy?
Heat, carbon dioxide and water
What goes into the body?
Food and oxygen
What is within food?
Chemical energy (carbohydrates, fats and proteins) and nutrients (vitamins and minerals)
What is food digested to?
Glucose, fatty acids, proteins, vitamins and minerals
What is there a balance between in the body?
Storage and metabolism
What is stored?
Triacylglycerol (TAG’s) and glycogen
What is involved in metabolism?
Glycolysis, beta oxidation and the citric acid cycle
What comes out of the body?
Heat, carbon dioxide and water
What happens in anabolism?
ATP is broke down into ADP and Pi when doing cellular work (high energy phosphate bond is broken by hydrolysis)
What happens in catabolism?
ADP and Pi combine to make ATP using energy from food
what happens in metabolism?
Carbon compounds in food are oxidised to form ATP
What is the energy balance in the body (perfect)?
Energy intake (food) = energy expended (basal metabolism and activities)
What is the energy balance in reality?
Energy intake = energy expended + energy stored
What is energy stored?
Weight gain
What can weight loss be achieved by?
Reducing energy intake (eat less and/or take certain drugs), increasing activities and increase basal metabolism
What is basal metabolism?
Energy required for maintenance of life
What is leptin?
A hormone which helps control appetite and weight
What are the units of energy?
Joules (J)
What is 1 joule?
The energy required to push against 1 newton of force for 1 metre
What is 1 cal?
4.184J
What is 1 Cal?
4.184kJ
What is daily dietary intake and energy expenditure usually measured in?
MJ
How is energy content of food measured?
Using calorimetry
What is the Atwater factor of fat?
38kJ/g
What is the Atwater factor of carbohydrate?
17 kJ/g
What is the Atwater factor of protein?
17 kJ/g
What is the Atwater factor of ethanol?
29kJ/g
Why is not all the energy in food available?
Losses I faces - fibre (cellulose), nitrogen is not oxidised (excreted in urine) so we have to adjust for these factors
What does direct calorimetry rely on?
Measuring heat output from an individual
What is direct calorimetry good for determining?
Basal metabolic rate (BMR)
What is indirect calorimetry based on?
Oxygen consumption and carbon dioxide production measured using a respirometer.
What is associated with every litre of oxygen consumed?
A certain amount of energy (20.9 kJ)
What does indirect calorimetry allow to be calculated?
Energy expenditure for a range of activities and the respiration exchange ratio (RER)
What is the RER formula?
RER=carbon dioxide produced/oxygen consumed
What can RER determine?
What fuel is being used
What is involved in maintenance of life?
Muscle contractions, nerve conduction, ion transport, synthesis of macromolecules and maintenance of body heat
What is basal metabolic rate usually defined as?
Energy expenditure at rest
What factors affect BMR?
Gender, age, body size and composition, genetics, hormonal status, stress levels, disease status and certain drugs
What is BMR increased by?
Athletic training, late stages of pregnancy, fever, drugs (caffeine) and hyperthyroidism
What is BMR decreased by?
Malnutrition, sleep, drugs (beta blockers) and hypothyroidism
What is the RER value for sugar?
1
What is the RER value for fats?
0.7
