overview cellular respiration overview cellular respiration catabolic pathways recall this is breaking down of complex molecules 2 types of pathways fermentation – partial pathway requires no oxygen c

NADH and FADH2 donate electrons to the series of electron carriers in the ETC • The final electron acceptor is Oxygen. creating water as a by product of cell resp.[r]

Overview cellular respiration

Anaerobic fermentation in yeast

Anaerobic fermentation humans

Cellular respiration is aerobic

Cellular Respiration

• Cellular respiration is the process of

oxidizing food molecules, like glucose, to carbon dioxide and water

• The energy released is trapped in the form

of ATP for use by all the

energy-consuming activities of the cell

NAD+ and FAD

• 1 Each metabolic reaction in cellular respiration

is catalyzed by its own enzyme

2 As a metabolite is oxidized, NAD+ accepts two electrons and a hydrogen ion (H+);

results in NADH + H+

3 Electrons received by NAD+ and FAD are

high-energy electrons and are usually carried

to the electron transport system

FAD and NAD

Respiration has four distinct

• Glycolysis is the anaerobic catabolism of glucose

• It occurs in virtually all cells

• In eukaryotes, it occurs in the cytosol

• C6H12O6 + 2NAD+ -> 2C3H4O3 + 2

NADH + 2H+

Glycolysis is enzyme driven

• Shockwave – observe the step by step

process as you look at your book as well

as the animation

http://instruct1.cit.cornell.edu/courses/biomi290/ASM/glycolysis.dcr

• Glycolysis

• glycolysis

Summary of yield

• The net yield from each glucose

molecule is 2 NADH, 2ATP and 2

molecules of pyruvate

• An initial investment of 2 ATP yields 4 ATP and 2 NADH or a net gain of 2 ATP and 2 NADH

Energy from glycolysis

• If molecular oxygen is present the pyruvate enters the mitochondria

Mitochondria

• Mitochondria are membrane-enclosed

organelles distributed through the cytosol

of most eukaryotic cells

• Their main function is the conversion of

the potential energy of food molecules into ATP

• between the two is the intermembrane space

• the inner membrane is elaborately folded with

shelflike cristae projecting into the matrix

• a small number (some 5–10) circular molecules

of DNA

• Prior to entering the Krebs Cycle, pyruvate must

be converted into acetyl CoA

• This is achieved by removing a CO2 molecule from pyruvate and then removing an electron to reduce an NAD+ into NADH

• An enzyme called coenzyme A is combined with the remaining acetyl to make acetyl CoA which

is then fed into the Krebs Cycle The steps in the Krebs Cycle are summarized below:

Transition of pyruvate to acetyl CoA

• We are now back at the beginning of the Krebs Cycle Because glycolysis produces two pyruvate molecules from one glucose, each glucose is processes through the

kreb cycle twice

• For each molecule of glucose, six

NADH2+, two FADH2, and two ATP

To review

• Krebstca

• FADH yields 2 ATP

• You will need this information as we discuss the electron transport chain

Electron transport chain overview

• Krebstca (if can’t open go to bio home page at the bottom of page )

Harvesting the nrg

• So far we have from glycolysis and the Kreb’s cycle: (per molecule of glucose) ATP by substrate phosphorylation

NADH and FADH2 – (which account for most of the nrg stored from the

metabolism of glucose )

Electron Transport Chain

Key points

• Protons are translocated across the membrane, from

the matrix to the intermembrane space

• Electrons are transported along the membrane, through

a series of protein carriers

• Oxygen is the terminal electron acceptor, combining with electrons and H+ ions to produce water

• As NADH delivers more H+ and electrons into the ETS,

the proton gradient increases, with H+ building up

outside the inner mitochondrial membrane, and OH-

inside the membrane.

• http://www.wiley.com/legacy/college/boyer

/0470003790/animations/electron_transport/electron_transport.swf

• (follow electron transport )

• respiration info (go to electron transport chain)

• Animations (should be mcgraw hill)

Key Points to remember

• 1 NADH and FADH2 donate electrons to the series of electron carriers in the ETC

• The final electron acceptor is Oxygen

creating water as a by product of cell resp

Points cont

• At certain steps along the chain, electron transfer causes electron carrying protein complexes to move Hydrogen ions from the matrix to the intermembrane space storing energy as a proton-motive force (hydrogen gradient)

• Animation of Chemiosmosis Proton

Pumping

• Electron transport system:

(follow NADH and FADH2 as well as

counting number of ATP made.)

Related Metabolic Pathways

• Without oxygen electronegetive oxygen to pull the electrons down the transport

chain, oxidative phosphorylation ceases

• Fermentation provides another avenue for the synthesis of ATP

• Fermentation regenerates ATP by

transferring electrons are transferred to pyruvate

• The miracle of fermentation

Process of alcohol fermentation

• Fermentation consists of glycolysis plus

reduction of pyruvate to either lactate or alcohol and CO2

• NADH passes its electrons to pyruvate

instead of to an electron transport system;

• NAD+ is then free to return and pick up more electrons during earlier reactions of glycolysis

lactic acid fermentation

• pyruvate is used as the

direct acceptor of the

hydrogens removed

from NADH The end

product is a molecule

of lactic acid Lactic

acid [or lactate] is a

common by-product of

anaerobic respiration

in muscle cells

Advantage of Fermentation

• provides quick burst of ATP energy for muscular activity

Disadvantage of Ferm

• lactate is toxic to cells

lactate changes pH and causes muscles

to fatigue lactate is sent to liver, converted into pyruvate; then respired or converted into glucose

• Two ATP produced per glucose molecule during fermentation

Go through this site and do review

questions

• Cell Respiration: Introduction

• General & Human Biology