the mechanism of enzymatic action

Copyright © 2010 Pearson Education, Inc.Figure 5.4a

The Mechanism of Enzymatic Action

Copyright © 2010 Pearson Education, Inc.Figure 5.7a–b

Enzyme Inhibitors: Competitive Inhibition


Enzyme Inhibitors: Competitive Inhibition Example-Sulfa drugs (sulfonamides) Discovered in the 1930s

Copyright © 2010 Pearson Education, Inc.Figure 5.9

Oxidation-Reduction


Representative Biological Oxidation


The Generation of ATP ATP is generated by the phosphorylation of ADP

1. Substrate-level Phosphorylation2. Oxidative Phosphorylation3. Photophosphorylation


Substrate-Level Phosphorylation

A chemical reaction where a phosphate group is transferred from one molecule to ADP. This requires a specific enzyme that can transfer the phosphate from this specific molecule to ADP.

ATP is produced this way during FERMENTATION Glycolysis (or alternative pathways) Krebs cycle


Oxidative Phosphorylation

Energy released from transfer of electrons (oxidation) from one compound to another (reduction) is used to generate ATP in the electron transport chain

An electron transport chain(ETC) couples a chemical reaction between an electron donor (such as NADH) and an electron acceptor (such as O2) to the transfer of H+ ions across a membrane, through a set of mediating biochemical reactions. http://en.wikipedia.org/wiki/Electron_transport_chain


Photophosphorylation

Light causes chlorophyll to give up electrons. The electrons go through a process similar to what happens during respiration (an electron transport chain and chemiosmosis occur). This process releases energy used to bond a phosphate to ADP producing ATP.

The ATP produced is used to produce food molecules (sugars-glucose).


Glycolysis

The oxidation of glucose to pyruvic acid produces ATP (Substrate level phosphorylation)and NADH

2 Stages: See next 2 slides

Copyright © 2010 Pearson Education, Inc.Figure 5.12, steps 1–5

Energy Using Stage of Glycolysis

2 ATP are used Glucose is split to form 2 glucose-3-phosphate

Copyright © 2010 Pearson Education, Inc.Figure 5.12, steps 6–10

ATP Creating Stage of Glycolysis

2 glucose-3-phosphate oxidized

to 2 pyruvic acid 4 ATP produced

Substrate-level phosphorylation 2 NADH produced


Preparatory Step Intermediate between Glycolysis and Krebs Cycle Pyruvic acid (from glycolysis) is oxidized and

decarboyxlated


The Krebs Cycle


Chemiosmotic Generation of ATP


Pathway Eukaryote Prokaryote

Glycolysis Cytoplasm Cytoplasm

Intermediate step Cytoplasm Cytoplasm

Krebs cycle Mitochondrial matrix Cytoplasm

ETC Mitochondrial inner membrane Plasma membrane

Comparing Eukaryotic and Prokaryotic Cellular Location of Catabolic Processes


Aerobic and Anaerobic Respiration

Aerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen (O2).

Anaerobic respiration: The final electron acceptor in the electron transport chain is not O2. Yields less energy than aerobic respiration because only part of the Krebs cycles operates under anaerobic conditions.


Electron Acceptor Products

NO3– NO2

–, N2 + H2O

SO4– H2S + H2O

CO32 – CH4 + H2O

Anaerobic Respiration


Fermentation

FERMENTATION Scientific definition: Releases energy from oxidation of organic molecules Does not use oxygen Does not use the Krebs cycle or ETC Uses an organic molecule (pyruvic acid) as the final

electron acceptor to form ‘end-products’ (acids and alcohols)

2 ATPs netted


Types of Fermentation


Catabolism of Organic Food Molecules


Photosynthesis

Conversion of light energy into chemical energy (ATP) which is used to synthsize nutrients (glucose)

Overall Summary Reaction? Compare and Contrast: Oxidative Phosphorylation

and Photophosphorylation.


Photosynthesis

Oxygenic:

Anoxygenic:

2 2

6 12 6 2 2

6 CO + 12 H O + Light energy

C H O + 6 H O + 6 O

2 2

6 12 6 2

6 CO + 12 H S + Light energy

C H O + 6 H O + 12 S


Nutritional Type Energy Source Carbon Source Example

Photoautotroph Light CO2 Oxygenic: Cyanobacteria plantsAnoxygenic: Green, purple bacteria

Photoheterotroph Light Organic compounds

Green, purple nonsulfur bacteria

Chemoautotroph Chemical CO2 Iron-oxidizing bacteria

Chemoheterotroph Chemical Organic compounds

Fermentative bacteriaAnimals, protozoa, fungi, bacteria.

Metabolic Diversity among Organisms


Amphibolic Pathways

the mechanism of enzymatic action

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