Chapter 9 Cellular respiration-1

Chapter 9 Cellular respiration-1 - Oxidation of glucose The...

Info iconThis preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon
Oxidation of glucose When glucose burns, energy is released as heat and light: C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 0 + 686 kcal/mol The same equation applies to the metabolism of glucose by cells, but the reaction is accomplished in many separate steps so that much (~50%) of the energy can be captured as ATP. The majority of this energy is released in oxidation-reduction (redox) reactions, with the energy initially captured by a molecule called NADH, and then the energy of NADH supplies the energy for production of ATP. The most common fuel in organisms is glucose. Other molecules are first converted into glucose or other intermediate compounds.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Transferring electrons: oxidation-reduction (redox) reactions High energy Low energy Low energy High energy The gain of one or more electrons is called reduction . The recipient is called the oxidizing agent and is said to be reduced. The loss of electrons in called oxidation. The donor is called the reducing agent and is said to be oxidized. Such redox reactions transfer a lot of energy. Much (but not all – think Second Law) of the energy liberated by the oxidation of the reducing agent is captured in the reduction of the oxidizing agent. H + H + H + H +
Background image of page 2
Gain or loss of hydrogen atoms Transfer of hydrogen atom (H + + e - ) involve transfer of electrons. Oxidation: AH 2 A loss of H atoms and electrons Reduction: B BH 2 gain of H atoms and electrons Redox : AH 2 + B A + BH 2 When the transfer of electrons in this redox reactions is complete, the high-energy product is the reduced one, the BH 2 . In the burning and the metabolism of glucose, glucose is the reducing agent (the donor of electrons), and O 2 is the oxidizing agent (and the ultimate recipient of the electrons). However, in metabolism, many reactions transfer electrons to produce a collection of high-energy “BH 2 ”compounds.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Oxidatively stepping along functional groups
Background image of page 4
Even further to CO 2
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
NAD The coenzyme NAD (nicotinamide adenine dinucleotide) is a key electron carrier in biological redox reactions. NADH + H + + ½ O 2 NAD + + H 2 O + 52.4 kcal/mole. As you will see, the reaction with oxygen (cellular respiration) actually takes place, producing ~2.5 ATP (12 kcal/mole each) in the process! ½ O 2 H 2 O Oxidizing agent
Background image of page 6
The reaction NAD + + 2H NADH + H + involves transfer of two hydrogen atoms, but what is actually transferred is an H - (a proton and two electrons) and a free proton (H + ) Thus, NAD exists in two forms, oxidized (NAD + ) and reduced (NADH + H + ). The former is “low energy”, the latter “high energy”. NAD (nicotinamide adenine dinucleotide)
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
ATP: Adenosine triphosphate ATP is composed of a purine base, a 5-carbon (ribose) sugar, and three phosphate groups. It is a high-energy molecule, the result of repulsion by the negative charges on each phosphate group. ATP is produced during breakdown of high energy molecules. Hydrolysis of ATP + H 2 O ADP + P i releases 12 kcal/mol to drive otherwise endergonic reactions.
Background image of page 8
Aerobic vs. Anerobic metabolism Three processes: Glycolysis Cellular respiration Fermentation
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Five pathways Starting with glucose, ultimately produced by
Background image of page 10
Image of page 11
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/19/2011 for the course LS 2 taught by Professor Pires during the Spring '08 term at UCLA.

Page1 / 41

Chapter 9 Cellular respiration-1 - Oxidation of glucose The...

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online