pyruvic acid (from ) is oxidized and...

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

• Pyruvic acid (from __________) is oxidized and decarboyxlated

Intermediate Step

Figure 5.13.1


Krebs Cycle

Figure 5.13.2

• Oxidation of acetyl CoA produces NADH, FADH2 & ATP

• Energy from acetyl CoA bonds transferred to ___?

• Where in the cell does the Kreb cycle occur

• Prokaryotes?

• Eukaryotes?


• Five types of reactions in Krebs cycle

• Anabolism of citric acid (1)

• Isomerization reactions (2,7,& 8)

• Redox reactions (3,4,6, & 8)

• Decarboxylations (3 & 4)

• Substrate-level phosphorylation (5)

The Krebs Cycle

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Figure 5.19

The Krebs Cycle


• Results in:

• Two molecules of ATP

• Two molecules of FADH2

• Six molecules of ______

• Four molecules of _____

The Krebs Cycle

What is the overall reaction for cellular respiration?


• A series of carrier molecules that are, in turn, oxidized and reduced as _________ are passed down the chain.

• Energy released can be used to produce ATP by _______________.

The Electron Transport Chain


• Most significant production of ATP

• Stepwise release of energy from series of ______ reactions

• ETC consists of series of membrane-bound carrier molecules that pass electrons from one to another and ultimately to _________________

• Energy from electrons used to pump protons (H+) across the membrane, establishing a ___________

• Located in cristae of eukaryotes and in the cytoplasmic membrane of prokaryotes

Electron Transport


• Four categories of carrier molecules

• Flavoproteins

• Ubiquinones

• Metal-containing proteins

• Cytochromes

• In aerobic respiration

• _________ serves as final electron acceptor to yield water

• In anaerobic respiration

• ___________________ serve as the final electron acceptor

Electron Transport


• Electrochemical gradient across memebranes

• because one or more chemicals is in higher concentration on one side of membrane

• Cells use energy released in redox reactions of ETC to create electrochemical gradient

• known as proton gradient

• has potential energy known as _______________

• H+ ions cross the membrane through _____________ (protein channels) that phosphorylate ADP to ____

• = ____________ phosphorylation

• because proton gradient created by oxidation of components of ETC

• A total of __________ of ATP are formed from one molecule of glucose

Chemiosmosis


Electron Transport


Chemiosmosis


Chemiosmosis

Figure 5.16.2


• Aerobic respiration: final electron acceptor = molecular oxygen (O2).

• Anaerobic respiration: final electron acceptor is not O2.

• Yields less energy

Respiration

C6H12O6 + 6O2 6CO2 + 6H2O + 38ATP + Heat

Glucose reduced to carbon dioxide


Pathway Eukaryote Prokaryote

Glycolysis Cytoplasm Cytoplasm

Intermediate step Cytoplasm Cytoplasm

Krebs cycle Mitochondrial matrix Cytoplasm

ETC Mitochondrial inner membrane

Plasma membrane


• Energy produced from complete oxidation of 1 glucose using aerobic respiration

Pathway ATP

produced NADH

produced FADH2

produced

Glycolysis 2 2 0

Intermediate step 0 2

Krebs cycle 2 6 2

Total 4 10 2


• ATP produced from complete oxidation of 1 glucose using aerobic respiration

• 36 ATPs are produced in eukaryotes. How many in prokaryotes?

Pathway By substrate-level phosphorylation

By oxidative phosphorylation

From NADH

From FADH

Glycolysis 2

Intermediate step

0

Krebs cycle 2 18

Total 4 30 4


Anaerobic respiration

Electron acceptor Products

NO3–

NO2–, N2 + H2O

SO4– H2S + H2O

CO32 – CH4 + H2O


• Essential function – regeneration of NAD+ for glycolysis

• When is NAD+ regenerated in aerobic respiration?

• Releases energy from oxidation of organic molecules

• Does not require oxygen

• Does not use the ______________

• Uses an organic molecule as the __________________

• Not as efficient as respiration

Fermentation


Fermentation


Fermentation

Figure 5.19

•Fermentation products are considered ______ ________ by the cell


Fermentation

Figure 5.18b


Fermentation

Figure 5.23


• Lipid Catabolism

• Protein Catabolism

Other Catabolic Pathways


Lipid Catabolism

Figure 5.20

An enzyme that breaks down

lipids is called ?


Protein Catabolism

Protein Amino acids Extracellular proteases

Krebs cycle Deamination, decarboxylation, dehydrogenation

Organic acid

An enzyme that breaks down a protein is called?


Protein Catabolism


Protein Catabolism

Figure 5.22


Biochemical tests

Figure 10.8

• Used to identify bacteria.


• Photo: Conversion of light energy into _____________________

• Light-dependent (light) reactions

• Synthesis: Fixing carbon into _______________

• Light-independent (dark) reaction, Calvin-Benson cycle

• Oxygenic: 6 CO2 + 12 H2O + Light energy C6H12O6 + 6 O2 + 6 H2O

• Anoxygenic: CO2 + 2 H2S + Light energy [CH2O] + 2 A + H2O

Photosynthesis


Light-Dependent Reactions


• As electrons move down the chain, their energy is used to _______________ across the membrane

• Photophosphorylation uses proton motive force to generate ATP

• Photophosphorylation can be cyclic or noncyclic

Light-Dependent Reactions


Noncyclic Photophosphorylation

Figure 5.24b


• Do not require light directly

• Use ATP and NADPH generated by light-dependent reactions

• Key reaction is carbon fixation by Calvin-Benson cycle

• CO2 is used to form glucose (C6H12O6)

Light-Independent Reactions


Metabolic Diversity

• Halobacterium uses bacteriorhodopsin, not chlorophyll, to generate electrons for a chemiosmotic proton pump.


Metabolic Diversity Among Organisms

Nutritional type Energy source Carbon source Example

Photoautotroph Light CO2 Oxygenic: Cyanobacteria plants.

Anoxygenic: Green, purple bacteria.

Photoheterotroph Light Organic compounds

Green, purple nonsulfur bacteria.

Chemoautotroph Chemical CO Iron-oxidizing bacteria.

Chemoheterotroph Chemical Organic compounds

Fermentative bacteria.

Animals, protozoa, fungi, bacteria.


• Anabolic reactions are synthesis reactions

• Require energy and source of metabolites

• Use energy derived from ATP from catabolic reactions

• Glycolysis, the Krebs cycle, and the pentose phosphate pathway provide

• 12 basic precursor metabolites

• all macromolecules and cellular structures are made from these

Other Anabolic Pathways


• Polysaccharide Biosynthesis

Metabolic Pathways of Energy Use


• Lipid Biosynthesis

Metabolic Pathways of Energy Use


Anabolic Pathways – Amino Acid Biosynthesis


Anabolic Pathways – Nucleotide Biosynthesis


• Many anabolic pathways are the reversal of the catabolic pathways

• Reactions that can proceed in either direction are amphibolic.

Amphibolic pathways

Figure 5.32.1


Amphibolic pathways

Figure 5.32.2


Metabolism

pyruvic acid (from ) is oxidized and...

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