CHAPTER 5

Microbial Metabolism Metabolism- collection of controlled biochemical reactions in microbes 8 Elementary Statements – Acquires nutrients – Energy from metabolism – Use enzymes – Energy stored in ATP – Construct large building blocks – Link blocks together – Grow by making cell structures – Reproduce at doubled size

Basic Chemical Reaction Catabolism and Anabolism – Metabolism= Catabolism + Anabolism – Catabolic/ Anabolic Pathway Oxidation and Reduction Reactions – Oxidation-Reduction aka Redox Reaction – Electron carrier molecules ATP Production and Energy Storage – Phosphorylation – Phosphorylating ADP to ATP

Basic Chemical Reaction The Role of Enzymes in Metabolism – Naming and classifying Enzymes – The make up of Enzymes – Enzyme Activity Temperature pH Enzyme and Substrate Concentration Inhibitors (competitive or noncompetitive)

Carbohydrate Catabolism Glycolysis – 3 stages of glycolysis Cellular Respiration – Synthesis of Acetyl-CoA – The Krebs Cycle – Electron transport – Chemiosmosis – Pentose Phosphate Pathway – Entner-Doudoroff Pathway

Catabolism Pathways There are two important pathways for the catabolism of glucose: – the pentose phosphate pathway – and the Entner-Doudoroff pathway.

Pentose Phosphate Pathway The pentose phosphate pathway is used primarily for the production of precursor metabolites used in anabolic reactions, Precursor metabolites, often produced in catabolic reactions, are used to synthesize all other organic compounds. The pathway reduces two molecules of NADP+ to NADPH and nets a single molecule of ATP from each molecule of glucose.

Entner-Doudoroff Pathway a series of reactions that catabolize glucose to pyruvic acid using different enzymes. Like the pentose phosphate pathway, the Entner-Doudoroff pathway nets uses only a single molecule of ATP for each molecule of glucose

The Catabolic Process In the first step of fat catabolism, enzymes called lipases hydrolyze the bonds attaching the glycerol to the fatty acid chains. Subsequent reactions further catabolize the glycerol and fatty acid molecules. Glycerol is converted to DHAP, which as one of the substrates of glycolysis is oxidized to pyruvic acid.

Protein Catabolism Since proteins are too large to cross the cytoplasmic membranes, prokaryotes typically conduct the first step in the process of protein catabolism outside the cell by secreting proteases (enzymes that split proteins into their constituent amino acids.) Once broken down, the amino acids are transported into the cell.

Photosynthesis Photosynthetic organisms capture light energy with pigment molecules called chlorophylls. – Chlorophyll molecules are composed of a hydrocarbon tail attached to a light-absorbing active site centered around a magnesium ion (Mg2+). Cells arrange numerous molecules of chlorophyll and other pigments within a protein matrix to form light-harvesting matrices called photosystems that are embedded in cellular membranes called thylakoids

Amino Acid Biosynthesis Some organisms, including humans, cannot synthesize certain amino acids, called essential amino acids; they must be acquired in the diet. – One extreme example is Lactobacillus, a bacterium that ferments milk and produces some cheeses. Amino Acid Biosynthesis is the reverse of the catabolic reactions. A cell moves the amine group from one amino acid and adds it to a metabolite, producing a different amino acid. This process is called transamination.