Class notes micro 102

Microbial Metabolism
Catabolic and Anabolic Metabolism
Catabolic Metabolism

 Defined as the metabolic pathways that break down complex molecules into simpler ones

 Results in the release of energy, which is often used to produce ATP

 Examples of catabolic pathways include:

 Fermentation (but not all types, only those that result in energy release)

 Glycolysis

 Oxidation of fatty acids

 Citric acid cycle

Anabolic Metabolism

 Defined as the metabolic pathways that build up complex molecules from simpler ones

 Requires an input of energy, often in the form of ATP

 Examples of anabolic pathways include:

 Gluconeogenesis

 Lipogenesis

 Protein synthesis

Metabolic Pathways and Enzymes

 Catabolic and anabolic pathways are interconnected and rely on a complex network of enzymes to
function

 Many enzymes require cofactors (such as vitamins and minerals) to function properly

 The activity of enzymes can be affected by a variety of factors, including temperature, pH, and the
presence of activators or inhibitors

ATP Generation and Phosphorylation

 ATP is the primary energy currency of the cell

 ATP can be generated through a process called oxidative phosphorylation, which occurs during cellular
respiration

 ATP is produced when a third phosphate group is added to ADP, a reaction known as phosphorylation

Cellular Respiration and Energy Production

,  Cellular respiration is the process by which cells convert glucose and other molecules into ATP

 Cellular respiration can be aerobic (in the presence of oxygen) or anaerobic (in the absence of oxygen)

 Oxidative phosphorylation is the primary way that cells generate ATP during aerobic respiration

Factors Affecting Enzyme Activity

 Enzyme activity can be affected by a variety of factors, including:

 Temperature: enzymes have an optimal temperature at which they function best

 pH: enzymes have an optimal pH at which they function best

 Activators and inhibitors: molecules that increase or decrease enzyme activity

 Enzyme concentration: the amount of enzyme present in a given volume

 Substrate concentration: the amount of substrate (the molecule the enzyme acts on) present in a
given volume

Cellular Respiration: Aerobic vs Anaerobic

 Aerobic respiration requires the presence of oxygen and results in the production of a large amount of
ATP

 Anaerobic respiration does not require the presence of oxygen and results in the production of less ATP
than aerobic respiration

 Fermentation is a type of anaerobic respiration which occurs in the absence of oxygen and produces a
small amount of ATP through the breakdown of glucose or other carbohydrates.



Metabolic Pathways and Enzymes: Fermentation and Cellular Respiration
Fermentation

Types and Industrial Uses

 Alcohol fermentation: Commonly used in the production of alcoholic beverages and bread. It is carried
out by yeast and produces ethanol and carbon dioxide.

 Lactic acid fermentation: Important in muscle physiology and in food preservation (e.g., yogurt,
sauerkraut). It is carried out by bacteria and produces lactic acid.

Cellular Respiration

ATP Generation and Phosphorylation

 Substrate-level phosphorylation: Direct transfer of a phosphate group from a high-energy donor
molecule to ADP.

 Oxidative phosphorylation: Process that generates ATP using energy from the electron transport chain.
This process is coupled with the movement of protons across a membrane.