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.