Chapter 13: How Cells Obtain Energy from Food- Principles of Metabolism

Electron transfer plays a role in.....

Metabolism. The transfer of electrons during chemical reactions releases energy stored in organic molecules. The released energy is ultimately used to synthesize ATP.

FYI: Both NADH and NADPH are active carries of electrons

NADPH is an activated caries of electrons that participates in oxidation-reduction reactions.

Cellular Respiration

A cellular process that in a series of steps breaks down nutrient molecules (glucose and other organic molecules) with the accompanying production of ATP. Electrons from organic compounds are usually first transferred to NAD+. a coenzyme. As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration.

Most energy coupling in cells is mediated by

ATP. ATP is a primary source of energy in all living cells . it is a renewable source of energy that is regenerated by addition of a phosphate group to ADP (adenophaste). The energy to phosphorylate ADP comes from catabolic reactions in the cell. ATP cycle is a revolving door through which energy passes during its transfer from catabolic to anabolic pathways. ATP drives endergonic reactions by phosphorylation.

How do cells manage energy resources?

By energy coupling, the use of an exergonic process to drive an endergonic one. Activated carriers can store and transfer energy in a form that cells can use.

What constitutes a cell's metabolism?

Catabolic and anabolic pathways (together). During catabolism, a major portion of the energy is stored in the chemical bonds of food molecules is dissipated as heat. But some energy is converted to the useful forms of energy needed to drive the synthesis of new molecules in anabolic pathways.

Redox Reactions (oxidation-reduction reactions)

Chemical reactions that transfer electrons between reactants

In oxidation, a substance loses...., In reduction, a substance gains.....

Electrons (or is oxidized), electrons (or is reduced, the amount of positive charge is reduced).

Free Energy (G)

Energy released that is available to do work, such as driving a chemical reaction

True or False: NADPH and NADH have the same roles in the cell.

False, they have different roles. The relative concentrations of these carrier molecules influence their affinity for electrons.

What reactions are considered catabolic reactions?

Hydrolysis reactions: Degradative reactions; break the bonds of larger molecules forming smaller molecules; require the input of water to break bonds; reactions which release energy are exergonic reactions.

Coupled Reactions

Linked pair of chemical reactions in which free energy released by one reaction serves to drive another reaction

What involve electron transfers?

Oxidation and reduction

How do cells obtain energy?

Oxidation of organic molecules in catabolic pathways

Pyruvate is broken down in the absence of....

Oxygen by fermentation

Fermentation

Partial degradation of sugars or other organic fuel that occurs without the use of oxygen, to either lactate or alcohol and CO2.

Name two complementary processes in the living world:

Photosynthesis and cell respiration

FYI: Mechanical Model of Coupled Chemical Reactions

See Slide

FYI: Alcoholic and Lactic Acid Fermentation Chart

See attachment

FYI: Carbon atoms cycle continuously through the biosphere

See attachment

Fermentation Chart

See attachment

FYI: An overview of cellular respiration

See slide

FYI on cellular respiration

See slide attached to flashcard. See slide 19-20

Activated carriers

Small organic molecules that contain one or more energy-rich covalent bonds. The molecules diffuse rapidly and carry their bond energy. In a sense, cells use activated carriers like money to pay for the energetically unfavorable reactions (anabolic reactions). They store energy in an easily exchangeable form, either as a readily transferable chemical group (in ATP) or as readily transferable ("high energy") electrons (NADH and NADPH)

Which captures useful energy, stepwise oxidation or simple burning of the same fuel molecule?

Stepwise oxidation, see slide.

Glycolysis

Sugar splitting

What reactions are considered anabolic reactions?

Synthesis/Condensation Reactions: It forms covalent bonds between smaller substrate molecules; release one molecule of water for each bond formed; biosynthesis; require ATP; reactions that occur with the absorption and storage of energy are endergonic reactions.

Oxidative phosphorylation completes...

The catabolism of food molecules and generates the bulk of the ATP made by the cell.

How many stages does the breakdown of food occur in?

Three. See slide