1. Energy Cells use oxygen in cellular respiration, which harvests chemical energy from food molecules. The waste products are CO 2 and H 2 O Cells are able to convert about 40% of the chemical energy stored in foods to energy for cellular work. The other 60% generates heat. This explains why exercise makes you hot! Sweating helps release this excess heat.

2. Energy Energy - the capacity to do work. Kinetic energy - energy of motion. Potential energy – stored energy. Chemical energy – potential energy available for release in a chemical reaction

3. Energy Transformations Thermodynamics – the study of energy transformations. 1 st law of thermodynamics – (law of energy conservation) Energy can be transferred, and transformed, but it cannot be created or destroyed.

4. Energy Transformations 2 nd law of thermodynamics – during every energy transfer or transformation, some energy becomes unstable & unusable (most often it converts to heat). –Heat is a disordered form of energy, an its release makes the universe more random. Entropy – a measure of this disorder. –Energy conversions increases the entropy (disorder) of the universe.

6. Chemical Reactions Exergonic reaction – “energy outward” a chemical reaction that releases energy. Example: Wood burning – as the cellulose (a polysaccharide) burns, each of the glucose molecules rich in potential energy release this energy in the form of heat and light.

7. Chemical Reactions Cellular respiration – an exergonic chemical process that uses oxygen to convert the chemical energy stored in food molecules to a form of chemical energy (ATP) that the cell can use to perform work.

8. Chemical Reactions Endergonic reactions – “energy inward” yield products that are rich in potential energy. Example: Photosynthesis, starts with energy-poor reactants (CO 2 and H 2 O) and, using energy absorbed from sunlight, produces energy-rich sugar molecules.

9. Chemical Reactions Metabolism – (metabole = change) the total of an organism’s chemical reactions (exergonic & endergonic). Metabolic pathway – a series of chemical reactions that either builds a complex molecule or breaks one down.

10. Chemical Reactions Energy coupling – the use of energy released from exergonic reactions to drive endergonic reactions. –All cells have this ability. –ATP molecules are key to this ability.

11. ATP drives cellular work ATP (adenosine triphosphate) Energy storing molecule that powers nearly all forms of cellular work. –Adenosine = a nitrogenous base adenine + ribose sugar. –Triphosphate = a chain of 3 phosphate groups.

12. ATP drives cellular work The 3 phosphates are negatively charged causing a mutual repulsion. This allows the triphosphate chain to be easily broken by hydrolysis. When a bond between the 3 phosphates is broken, one phosphate group leaves, energy is released, and ADP (adenosine diphosphate) remains.

14. ATP drives cellular work The hydrolysis of ATP is an exergonic reaction – it releases energy. The removed phosphate is transferred to some other molecule, a process called phosphorylation. Phosphorylation is an endergonic reaction. The two together form energy coupling.

15. 3 Types of cellular work Chemical – the phosphorylation of reactants provides energy to drive endergonic synthesis of products.

16. 3 Types of cellular work Mechanical – the transfer of phosphate groups to special motor proteins in muscle cells causes the proteins to change shape and pull on actin filaments, in turn causing the cells to contract.

17. 3 Types of cellular work Transport – ATP drives the active transport of solutes across a membrane against their concentration gradient by phosphorylating membrane proteins.

18. ATP drives cellular work ATP drives all 3 types. Work can be maintained because ATP is a renewable resource that cells regenerate. –Working muscle cells consume and regenerate 10 million ATP molecules each second!