mean that 400 calories are available in the body because some of the food components are broken down and the body has to use energy to break that down ● We have carbohydrates which have to be broken down by various enzymes in the body but there’s also energy involved in that process so we are actually going to use some of
CHEM 181 the calories that are available in the food to digest and break down some of the components in the food ● Cooked foods generally are more easily metabolized because you have already pre digested them ● For example, cooked and raw carrots will result in the same amount of calories but this is not necessarily what happens in the body because you would have to expend more calories to break down and digest the raw carrots than the cooked carrots ● Well done steak provides more available calories than raw meat because the cooking process already has broken down some of the protein and fat, and thus is essentially pre-digested ● In tables, the number you see is available as measured in a calorimeter ● One cup of orange juice would be listed as 108 calories because it would be burned in a calorimeter and the amount of energy that is available 108 calories ● However, you would also be able to burn fudge and get 155 calories, not all that different ● A gram of dynamite would also burn 155 calories ○ The calorie content of a square of fudge is equal to that of a gram of dynamin because if you would burn these in a calorimeter, they will produce the same amount of energy ○ However, when you light a piece of dynamite, all of that energy, is released at once (hence, kinetics) ● Metabolism – the energy consumption by biochemical processes ○ Everything that goes on in our body takes some effort, all of which require energy that are sourced from food ● The Basal Metabolic Rate is the amount of energy that we would expand over a 24-hour period by doing nothing ○ The amount of energy that is needed, the total number of of calories that are needed to just keep you alive is the Basal Metabolic Rate ● “Burning calories” is somewhat a misnomer – you can’t burn a calorie as it is just a measure of energy, what we really mean is that we’re going to need energy and we’re going to be burning some food components in our body to produce that amount of energy and we equate the calorie content to certain amounts of food ○ You’re burning food components with their release of calories which can be measured by: ■ Placing people in a room that is thermally insulated from the outside, have them do some kind of activity and measure the temperature change in the room (temp. Change comes from the energy that is being expended from doing that activity) ■ Measuring the amount of oxygen that is inhaled and the amount of carbon dioxide that is exhaled because that is proportional to the “burning of calories” because any combustion process requires the combination of the food component with oxygen to release carbon dioxide and water so we can measure the intake of oxygen and the exhaled amount of CO2
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- Spring '11