The Need for Energy Chapter 9.1
Cell Energy • Energy is essential to life • All living things must be able to obtain energy from the environment in which they live • Define energy: • The ability to do work
Energy is captured in 2 different ways • EUKARYOTES ONLY • Autotrophs- make their own food sunlight • Plants, photosynthetic bacteria, some protists Heterotrophs- obtain food from an outside source animals, fungi, some bacteria and protists FOOD=ENERGY
CHEMICAL ENERGY • Living things must use chemical energy to do work • Page 222- paragraph on working • Chemical energy found in 2 places: • 1. electrons- changing energy levels • 2. chemical bonds- making and breaking bonds.
Chemical bonds and energy • Making bonds stores energy. • Endergonic • Breaking bonds releases energy • exergonic
ATP • Energy is stored in the chemical bonds of a molecule that can be used quickly and easily by the cell • Adenosine triphosphate • Primary energy molecule used by living things
The enormous amount of activity that occurs inside each of the approximately one hundred trillion human cells is shown by the fact that at any instant each cell contains about one billion ATP molecules. This amount is sufficient for that cell’s needs for only a few minutes and must be rapidly recycled. Given a hundred trillion cells in the average male, about 1023 or one sextillion ATP molecules normally exist in the body. For each ATP “the terminal phosphate is added and removed 3 times each minute” (Kornberg, 1989, p. 65). • The total human body content of ATP is only about 50 grams, which must be constantly recycled every day. The ultimate source of energy for constructing ATP is food; ATP is simply the carrier and regulation-storage unit of energy. The average daily intake of 2,500 food calories translates into a turnover of a whopping 180 kg (400 lbs) of ATP (Kornberg, 1989, p. 65).
ATP structure • Made of: • 1. one 5 carbon sugar named RIBOSE • 2. one nitrogen base called ADENINE • 3. three phosphate groups.
The phosphates of ATP • Phosphate groups are charged particles • In the phosphate bonds is where the energy is stored • The energy of ATP becomes available to a cell when the molecule is broken down • When a phosphate bond in broken, and a phosphate is released for energy, the molecule of ATP becomes a molecule of ADP “adenosine DIPHOSPHATE”
Figure 9.2 page 223 • The formation and breakdown of ATP is cyclic • The addition and release of a phosphate group on adenosine diphosphate creates a cycle of ATP formation and breakdown
Phosphorylation • Adding a phosphate group (ADP to ATP) is called phosphorylation. • This requires energy • Endergonic • Occurs in mitochondria
Dephosphorylation • Releasing the phosphate group is exergonic • Gives off energy • Ex. ATP to ADP
Making more ATP • As long as phosphate groups are available, the cell can make more ATP • “what is ATP and how does it work” 2:45 • http://www.youtube.com/watch?v=bbtqF9q_pFw • 9:35 video “The ATP cycle” http://www.youtube.com/watch?v=AhuqXwvFv2E&feature=related