#### Transcript Energy

```Energy
THE ABILITY TO DO WORK
Cells use energy for:
 Movement
 Muscles, flagella wiggling
 Making and breaking chemical bonds.
 Joining A.A. into protein.
 Pumping things into and out of cells
 Pumping ions out of cells
 Pumping wastes out of blood in kidney.
Energy is measured in calories
 1 calorie is the energy needed to raise 1 gram of water
1 degree Celsius.
 1 ml of water weighs 1 gram.
 So 40ml water weighs ?
Calculating energy into calories.
 Multiply the amount of water [in grams] heated
 Times the increase in temperature in C.
 Practice:
 50 ml water changes from 22C up to 30C
 How many calories was absorbed by the water?
More calculations
Init T
Final T
ml
13
48
15
2
23
40
17
38
22
Change
Calories
Burning releases the energy stored in wood
How would you release the energy stored in
food?
Measuring the energy in food
 We will burn food and heat up water.
 We will calculate the amount of energy given off by
the food we burn. [calories]
 We will mathematically adjust the amount of energy
so that it represents 1g of food. [calories/g]
 This is done so different types of food or different
amounts of food can be compared.
Calorimeter measured the energy.
Comparing the energy in 2 foods
 To get the data adjusted so it represents the same
amount of food we do a simple calculation.
 Divide the calories released by the weight of food
burned up.
 By dividing calories by the weight of the food we get
calories per gram.
Sample calculations
 A kidney bean weighs 2.3g.
 It is burned up and the ashes weigh .6g
 1.7 g of bean were lost.
 The burning bean heated 40ml of water from 17C up
to 31C.

note: [14ml H2O = 14g of H2O]
 The water is 14C hotter.
 14C x 40g water
 560 calories / by 1.7g
=
560 calories.
=
329 calories/gram
Calculations
Temp C
Initial
Final
Change
Water (g)
calories
12
35
23
40 ml
920
Mass
Initial
Final
change
2.1 g
.8 g
1.3 g
Calories/gram
920/1.3
708 cal/g
Kilocalories…..kcal food calories
 1 kcal has 1000 calories
 To convert calories into kcal……….
 Divide calories by 1000.
 2300 calories = 2.3 kcal.
```