10Feb_11

10Feb_11 - Biological Science I Tuesdays and Thursdays...

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Biological Science I Tuesdays and Thursdays 8:00-9:15, HCB 102 Mondays 5:15-6:15, KIN 1024 10 February 2010 – Lecture 11 REVIEW FROM LAST LECTURE 1. ATP powers cellular work by coupling exergonic reactions to endergonic reactions a. A cell does three main kinds of work: a.i. Chemical a.ii. Transport a.iii. Mechanical b. To do work, cells manage energy resources by energy coupling, the use of an exergonic process to drive an endergonic one c. Most energy coupling in cells is mediated by ATP d. The Structure and Hydrolysis of ATP d.i. ATP (adenosine triphosphate) is the cell’s energy shuttle d.ii. ATP is composed of d.ii.1. ribose (a sugar) d.ii.2. adenine (a nitrogenous base) d.ii.3. and three phosphate groups d.iii. The bonds between the phosphate groups of ATP’s tail can be broken by hydrolysis d.iv. Energy is released from ATP when the terminal phosphate bond is broken d.v. This release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves 2. How ATP Performs Work a. The three types of cellular work (mechanical, transport, and chemical) are powered by the hydrolysis of ATP b. In the cell, the energy from the exergonic reaction of ATP hydrolysis can be used to drive an endergonic reaction c. Overall, the coupled reactions are exergonic d. ATP drives endergonic reactions by phosphorylation, transferring a phosphate group to some other molecule, such as a reactant e. The recipient molecule is now phosphorylated 3. The Regeneration of ATP a. ATP is a renewable resource that is regenerated by addition of a phosphate group to adenosine diphosphate (ADP) b. The energy to phosphorylate ADP comes from catabolic reactions in the cell c. The chemical potential energy temporarily stored in ATP drives most cellular work 1
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Biological Science I Tuesdays and Thursdays 8:00-9:15, HCB 102 Mondays 5:15-6:15, KIN 1024 10 February 2010 – Lecture 11 1. Overview: Life Is Work To perform their many tasks, living cells require energy from outside sources. Energy enters most ecosystems as sunlight and leaves as heat. In contrast, the chemical elements essential for life are recyled. Photosynthesis generates oxygen and organic molecules that the mitochondria of eukaryotes (including plants and algae) use as fuel for cellular respiration. Cells harvest the chemical energy stored in organic molecules and use it to regenerate ATP, the molecule that drives most cellular work. Respiration has three key pathways: glycolysis, the citric acid cycle, and oxidative phosphorylation. 2. Catabolic pathways yield energy by oxidizing organic fuels. Catabolic metabolic pathways release the energy stored in complex organic molecules. Electron transfer plays a major role in these pathways.
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10Feb_11 - Biological Science I Tuesdays and Thursdays...

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