Unit 4 MICROBIAL METABOLISM

cell respiration and enzyme activites

CHEMICAL REACTIONS AND ENERGY; In microorganisms, most chemical compounds

neither combine with one another automatically nor break apart automatically.

A spark called the energy of activation is needed. These reactions proceed in the presence of

biological catalysts. The catalyst speed up chemical reactions but

remain unchanged during the reaction. The catalyst work by lowering the required

amount of activation energy for the chemical reaction.

In microorganisms, the catalysts are enzymes

Enzymes

Enzymes: speed chemical reactions by lowering the energy of activation by forming a complex with their substrate at the active site

Active site: a small region on the surface of the enzyme, where the substrate binds.

Substrate: A reactant in an enzymatic reaction

When the substrate binds to the enzyme, the active site undergoes a slight change in shape that facilitates the reaction is called induced fit model

Only a small amount of enzyme is needed in a cell because the enzymes are not used up

Every cell reaction requires its specific enzyme, therefore, they are named for the substrates by adding the ending "ase" ex lipase, lactose

Factors affecting enzymatic speed:

1. moderate temperature and pH are best: as temp increases, enzyme activity increases... enzyme activity declines rapidly when enzymesare denatured (destroyed) at certain temperatures and pH

2. Amount of active enzyme affects speed3. Enzymes can be inhibited: regulated by other

molecules4. Cofactors help enzymes: many enzymes require

an inorganic ion or nonprotein cofactor (coenzyme) to function ex vitamins, NAD,FADH2

Cellular Respiration; is the process by which microorganisms obtain the energy available in carbohydrates.

They take the carbohydrates into their cytoplasm, and through a complex series of metabolic processes, they break down the carbohydrate and release energy.

CELL RESPIRATION

Microorganisms such as cyanobacteria can trap the energy in sunlight through the process of photosynthesis and store it in the chemical bonds of carbohydrate molecule.

The principal carbohydrate formed in photosynthesis is glucose.

Other types of microorganisms such as nonphotosynthetic bacteria, fungi and protozoa are unable to perform this process.

These organisms must rely upon preformed carbohydrates in the environment to obtain the energy necessary for their metabolicprocesses.

CELL RESPIRATION:

6O2 + C6H12O6 —> 6CO2 + 6H2O + energy

A fuel molecule such as glucose is oxidized to font carbon dioxideand water.

Energy is captured through the formation of up to 36 to 38 ATPsper molecule of glucose.

It is the process by which cells extract free energy from the energy stored in chemical bonds of food molecules (glucose)

Microbial life can exist only where molecules and cells remain organized, and energy is needed by all microorganisms to maintain organization.

Every activity taking place in microbial cells involves both a shift of energy and a measurable loss of energy.

Thus considerable more energy must be taken into the system than is necessary to simply carry out the actions of microbial life.

Three Metabolic Stages of Cellular Respiration include: 1. Glycolysis 2. kreb cycle 3. electron transport and oxidative

phosphorylation

This is done in a series of catabolic pathways featuring redox reactions and using oxygen as the final electron acceptor

The energy released is used to regenerate the cell's supply of A TP

ATP donates the energy to various energy-requiring processes suchas metabolic reactions, active transport, muscle contractions, or production of new polymers

Glycolysis:

a. Occurs in cytosol outside mitochondriab. Converts the 6-carbon glucose into 2 3-carbon

pyrvic acid moleculesc. 4 ATP are made, but due to a deficiency of 2ATP

the step generates a positive 2 ATPd. If oxygen is present then the reaction will

proceed to the kreb cycle, if oxygen is absent it will proceed to fermentation

e. Fermentation occurs in cytosol, has a net gain of 2ATPper glucose and is only 2.1% efficient

Transition reaction

Between glycolysis and kreb cycle is a Transition reaction in which pyruvate (pyruvic acid) is converted to acytyl CoA and 2 CO2 are removed

Kreb Cycle:

Is located within the mitochondria! matrix Completes glucose oxidation by breaking down

a pyruvic acid derivative (acetyl CoA ) into CO2 Is a circular set of reactions because the reaction

is ongoing, never reaching an end point

Requires 2 turns of the kreb cycle per glucose (each turn releasing: 2 CO2, 3 NADH, 1 ATP, 1 FADH2

NADH and FADH2 are coenzymes

. Oxidative phosphorylation:

a. Accounts for most ATP produced during respiration (32 to 34)

b. Includes electron transport chain made of electron carriers molecules built into the inner mitrochondrial membrane

c. Oxygen pulls energized electrons harvested during glycolysis and kreb cycle down the electron transport chain to a lowerenergy state.

d. This exergonic slide of electrons is coupled to A TP synthesis

e. Electron transport accepts electrons from glucose during glycolysis and transition reaction and kreb cycle...usually NAD+ carries these electrons.

f. The electrons them drop off the supply of energy needed to pump the H+ ions from the matrix to the intermembrane space of he mitochondria (which is chemiosmosis)

g. The NAD+ and FAD then return to pick up more hydrogen (both reusable)

When NADH delivers electrons, it has enough energy to make: 3 ATP .

When FADH2 delivers electrons, it has enough energy to make; 2 ATP

Chemiosmosis: ability of some membranes to use H+ ions gradient to drive ATP formation

Oxidative phosphorylation: refers to the production of ATP as a result of energy released by electron transport system