Energy balance in cells and organisms Flashcards
First law of thermodynamics
Energy interconversion - total energy within system is constant, energy neither created or destroyed however can be converted, biology relies on energy conversions
Energy balances in cells and organism process
Energy coming from sunlight is used by plants in photosynthesis resulting in oxygen being produced, some of the energy is utilised to form ATP energy molecules. When humans consume plants, another metabolic process can occur and potential energy can be released from chemical compounds converting some carbon into CO2 and gaining some energy
What are synthetic processes?
Synthetic processes (interconversion of molecules) generate a range of chemical compounds and variably inherit various amounts of chemical energy which can be utilised in other metabolic processes
Energy balances in the human body
We consume food molecules which contain various amounts of chemical energy. Food molecules are quite complex hence need to be broken down so components can be utilised = digestion. Digestion generates heat energy. Various metabolic processes take place such as glycolysis which cause an interconversion of these chemical compounds releasing energy (ATP) for cellular work
Interrelationship between anabolism and catabolism
Catabolism is the breakdown of food into its basic constituents and the oxidation of the basic building blocks to provide energy
Anabolism is the energy driven synthesis of these building blocks back into molecules and macromolecules that are assembled to form cells
Energy balances in body
In an ideal system the Eintake=Eexpended (basal metabolism + activities) however Eintake= Eexpended + Estored where Estored is potentially weight gain which causes an energy imbalance
How can weight loss be achieved?
Weight loss can be achieved by reducing energy intake (eat less/take certain drugs), increasing activities and increasing basal metabolism (energy required for maintenance of life)
What is peptide leptin?
Peptide leptin is made in fat cells and circulates in the blood, signals to brain that there is enough energy stored in the body hence controls hunger
What is direct calorimetry?
Calorimeters relies on measuring heat output from individual, good for determining BMR (individual at rest)
Provides ways of making various measurements such as BMR
What is indirect calorimetry?
What is going on in chemical reactions under catabolic processes, based on O2 consumption and CO2 production measured using a respirometer, a certain amount of energy is associated with energy litre of O2 consumed. Useful to determine for individuals what the principle fuel load is (lipids, carbohydrates etc)
What can we calculate with indirect calorimetry?
Allows calculation of energy expenditure for a range of activities and allows calculation of the respiration exchange ration (RER)
RER= CO2 produced/O2 consumed
What is Basal Metabolism?
Energy required for maintenance of life is the energy required for muscle contractions, nerve conduction, ion transport, synthesis of macromolecules and maintenance of body heat
Can be measured using respirometers
How does BMR differ in individuals?
Factors such as gender, age, body size, genetics, hormones, stress, disease status, certain drugs
Can be increased by athletic training, pregnancy, fever, drugs (caffeine), hyperthyroidism or decreased by malnutrition, sleep, drugs (beta-blockers), hypothyroidism
