Ch 5 - Microbial Metabolism Stephanie Lanoue Learning Objectives 5-1 Define metabolism, and describe the fundamental differences between anabolism and catabolism. 5-2 Identify the role of ATP as an intermediate between catabolism and anabolism.

Opening Discussion What is Metabolism? Take a moment to formulate your response. You may use google but answer in your own words. These chemical reactions provide ________ and create substances that sustain life. There are 2 types of chemical reactions that sustain metabolism: catabolic and anabolic.

Catabolic versus Anabolic Reactions Catabolism refers to the ______ _______ of complex molecules into simpler substances. These type reactions usually release energy. 2. Anabolism refers to reactions in which simpler substances are ___________ to form more complex molecules. These type reactions usually require energy.

Catabolic and Anabolic Reactions continued Metabolism (and metabolic pathways) are determined by _________. Question - What are enzymes? Take a minute to google. Try to formulate a definition in your own words. Be prepared to share.

Enzymes Learning Objectives continued 5-3 Identify the components of an enzyme. 5-4 Describe the mechanism of enzymatic action. 5-5 List the factors that influence enzymatic activity.

Enzymes continued Chemical reactions ______ enzymes. Enzymes act as: Biological catalysts _________ the rate of reaction Naming of Enzymes Enzymes are substrate specific, adding “ase” to the substance. For example: Lipases, Lipids Sucrases, Sucrose Ureases, Urea Proteases, Proteins Dnases, DNA Dehydrogenase, remove a hydrogen Phosphatase, remove a phosphate

How Do Enzymes Work in Chemical Reactions Steps (see image below) 1 – 2. Substrate contacts the enzyme's _____ site to form an enzyme-substrate complex 3- 4. _______ is transformed and rearranged into products, which are released from the enzyme 5. Enzyme is unchanged and can react with other substrates A – any substance an enzyme reacts with Question: What is a substrate? Products Substrate Active site Enzyme–substrate complex

Enzyme Specificity and Efficiency Enzymes have ________ for particular substrates Substrate Enzyme Substrate Figure 5.3b The mechanism of enzymatic action.

Coenzymes and Cofactors Most enzymes consist of two molecular components: A holoenzyme consisting of a ________ portion (or apoenzyme) 2. And a ___-protein portion (or cofactor). The cofactor can be an inorganic (or non-carbon based) component. Example: Iron, zinc, etc. Or an organic component (also known as a co-enzyme). Example: B12 Substrate Coenzyme Apoenzyme (protein portion), inactive Cofactor (nonprotein portion), activator Holoenzyme (whole enzyme), active

Enzyme Activity Factors Influencing Enzyme Activity: ________________ pH Discussion Question – What is pH? Answer – The measure of a substances acidity or alkalinity in a solution

Enzyme Activity High temperature (40 C) ____________ proteins Question – What does denaturing mean?

Enzyme Activity (cont’d) pH H+ concentration (pH) changes protein three-dimensional structure (enzyme denaturation)

Enzyme Activity (cont’d) Generally, at _____ temperatures, enzymes undergo denaturation and loose their catalytic properties. And, at low temperatures, reaction rates decrease/ ________.

A New Discovery: Ribozymes Prior to 1982, it was believed that only protein molecules had enzymatic activity. But researchers working on microbes discovered a unique type of ____ called a ribozyme. Ribozymes are ___ protein enzymes in most ways - they can function as catalysts - they have active sites that _____ to substrates - and they are not used up in chemical reactions But they also: - cut and splice RNA - and are involved in protein synthesis at ribosomes

Review Questions 1. What is special about ribozymes versus regular protein enzymes? 2. What is an enzyme? 3. What is a catalyst?

Energy Most microorganisms use ___________ (sugars and starches) as their primary source of cellular energy. Sugar (and starch) can therefore be broken down to produce __________. This is of great importance in cell metabolism. The breakdown (catabolism) of sugar happens in different ways: Aerobic respiration (the Kreb’s Cycle) Anaerobic respiration Fermentation NOTE: microorganisms can also catabolize various lipids and protein for energy production

Carbohydrate Catabolism Learning Objectives 5-6 Explain the steps of the Krebs cycle. 5-7 Compare and contrast aerobic and anaerobic respiration. 5-8 Describe fermentation.

Catabolism Carbohydrate catabolism: Microorganisms oxidize carbohydrates as their primary source of _______ Glucose – most _________ energy source Energy is produced by two processes 1. Cellular Respiration (also known as just Respiration)* - is either aerobic (occurs in the presence of O2) or anaerobic (without O2) 2. Fermentation (does not require O2 but can happen in its presence) *not the same as breathing

Overview of Cellular Respiration (Respiration) Inside Cells The breakdown of carbohydrates to ________ energy Glycolysis - Intermediate step Krebs cycle Electron transport chain

Respiration - Step 1 Glycolysis Happens in the ____________. Requires 2 molecules of ATP to get started plus glucose (a 6 carbon-chain sugar). Glucose is split into two, 3 carbon sugars which are then converted into pyruvic acid. This splitting (oxidation) of glucose into pyruvic acid results in the additional production of ____ and an energy-containing molecule called NADH. Question: What is NADH ? An coenzyme that functions in the transfer of hydrogen ions (H-) and electrons NOTE: Glycolysis is also known as the Embden-Meyerhof pathway.

Respiration - Glycolysis (cont’d) Pyruvic acid cannot enter the Kreb’s Cycle ___________. But it is important because pyruvic acid (thru a series of steps), is turned into acetyl coenzyme A (or acetyl coA) which is needed for the Kreb’s Cycle

Figure 5.12 An outline of the reactions of glycolysis (Embden-Meyerhof pathway).

Respiration – Step 2 The Kreb’s cycle In eukaryotes, this happens in the _____________ (within the matrix). NOTE: in prokaryotes, happens in the _____________. Krebs cycle (most basic steps): Pyruvic acid (from glycolysis) is oxidized and decarboxylation (loss of CO2) occurs The resulting two-carbon compound attaches to coenzyme A, forming acetyl CoA and NADH Oxidation of acetyl CoA produces NADH, FADH2, and ATP, and liberates CO2 as waste

Figure 5.13 The Krebs cycle.

Respiration – Step 3 The Electron Transport Chain Electron transport chain (system) Occurs in the ________ membrane of prokaryotes; inner mitochondrial ___________ (cristae) of eukaryotes Series of carrier molecules are oxidized and reduced as electrons and are passed down the ”chain”

Respiration The Electron Transport Chain These carrier molecules (mentioned from previous screen) are classified into three main categories: flavoproteins cytochromes ubiquinones Take a moment to look at page 123 in your textbook. Answer these questions now: What are flavoproteins derived from? Cytochromes are proteins that contain what important chemical? Ubiquinones are also commonly referred to as this substance (sold over-the-counter at drug stores)? Answers: Flavin (a coenzyme derived from riboflavin); B2 Iron Coenzyme Q

Respiration An Overview of Chemiosmosis Energy released can be used to _________ ____ by chemiosmosis Question: What is chemiosmosis? Electrons (from NADH) pass down the electron transport chain while protons (positively charged particles) are pumped across the plasma membrane.

Respiration – Summary of All 3 steps The final electron acceptor in the electron transport chain is molecular _________ (O2) In aerobic prokaryotes, ___ ATP (from the entire process of all 3 steps - glycolysis, Kreb’s and electron transport chain). In eukaryotes, 36 ATP are produced. By-products include ____ and H2O Unnumbered Figure pg. 126