Chapter 7.2 Summary

Food stores chemical energy

• Energy is the ability to perform work
• Kinetic energy: energy of motion
• Not possible to destroy or create energy
• Energy can be converted from one form to another
• Potential energy: energy stored due to an object's position or arrangement
• Thermal energy: random molecular motion
• Chemical energy: energy from organic compounds
• It is the potential to perform work due to the arrangement of atoms within molecules
• Org. molecules such as carbs, fats, and proteins are rich in chemical energy
• Complex molecules are broken into smaller molecules with less chemical energy than the original substance
• Oxygen + Glucose => Water + Carbon Dioxide
• 40% of energy produced is used
• 60% is lost in the form of heat
• Lost heat helps you maintain body temperature
• Calorie: amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius
• Usually measured in kilocalories
• 1 Kilocalorie (kcal) = 1000 calories
• Cells use enzymes to break down organic molecules

Concept Check 7.2

1. Identify the types of energy you have at the top of a staircase and as you go down the stairs

At the top of the staircase you have potential energy and you have kinetic energy as you go down the stairs.

2. Explain how your body uses chemical energy during exercise.

During exercise the body breaks down organic compounds for their chemical energy. Since we use more energy than normal while exercising, our cells increase the rate of cellular respiration. That's why we give off much more heat during and after excercise.

3. If a food has 10 kcal of energy, how much could it increase the temperature of 100 g of water?

It can increase the temperature of 100 g of water by 100 degrees Celsius.