Notes: Cellular Processes (Part 1) Cell Energy CELL ENERGY, PHOTOSYNTHESIS, AND CELLULAR RESPIRATION

Part 1: How Organisms Obtain Energy Cells are in constant motion, making proteins, breaking apart molecules for energy, growing, and splitting. This unit will cover how energy is harvested from the sun through photosynthesis and stored in sugar molecules. Then the cell breaks down glucose molecules as needed to release that stored energy. The free energy is in a molecule called ATP.

1. Transformation of Energy Chemical reactions occur constantly in cells. Assembling or breaking down macromolecules, sending genetic information where it’s needed, and transporting molecules into or out of the cell all require energy. Thermodynamics is the study of the flow of energy in the universe.

1. Transformation of Energy A. 1st Law of Thermodynamics – energy cannot be created nor destroyed, just converted from one form to another.

1. Transformation of Energy B. 2nd Law of Thermodynamics – energy cannot be converted without the loss of some usable energy, usually in the form of heat energy. Heat: The energy graveyard

1. Transformation of Energy C. Autotrophs are living organisms that make their own food. Most use the sun as their energy source through the process of photosynthesis.

1. Transformation of Energy D. Chemoautotrophs are a type of autotroph that do not use the sun, instead using hydrogen sulfide as it energy source in a process called chemosynthesis.

1. Transformation of Energy E. Heterotrophs must acquire energy through eating food. They are not able to fully utilize all of the energy they ingest due to the 2nd Law of Thermodynamics, losing some energy to heat.

2. Metabolism All of the chemical reactions within a cell are referred to as metabolism. A. Reactions that build larger molecules from atoms or smaller molecules require energy, called anabolic reactions.

2. Metabolism B. Reactions that tear apart large molecules into atoms or smaller molecules release energy, called catabolic reactions.

2. Metabolism C. Photosynthesis requires carbon dioxide, water, and light energy, which will be converted into chemical energy stored in the glucose molecules made. Since energy is required and larger glucose molecules are being built, photosynthesis is an anabolic reaction.

2. Metabolism D. Cellular respiration uses oxygen and breaks apart glucose, releasing energy, carbon dioxide, and water. Since energy is released and larger molecules are being broken apart, cellular respiration is a catabolic reaction.

3. ATP: the Unit of Cellular Energy Adenosine triphosphate (ATP) is the currency for energy within the cell. Just as we use dollars in America or Euros in Europe to pay for the things we want, cellular reactions that require energy will need “payment” in the form of ATP.

3. ATP: the Unit of Cellular Energy A. ATP Structure: Recall that “tri” means three, so triphosphate means there are three phosphate groups on each ATP molecule. The phosphate groups are bonded with ribose, a five carbon sugar that is chemically the same as glucose (C6H12O6) but shaped differently. The ribose is bonded with adenine, which is also used in DNA molecules. Circle the adenine below. Squiggly line around the ribose. Box the triphosphates.

3. ATP: the Unit of Cellular Energy B. ATP is matter, not energy, but it releases energy by breaking off one of its three phosphate groups. Recall that “di” means two. When only two phosphates remain, the molecule is called Adenosine diphosphate (ADP).

3. ATP: the Unit of Cellular Energy C. The constant adding of a third phosphate (building larger molecule, requires energy, anabolic) or removing of a third phosphate (tearing apart larger molecules, releases energy, catabolic) is the cycle of energy within a cell.