Microbio UNIT 3

chemical reactions

making or breaking of bonds between atoms

a change in chemical energy occurs during a chemical reaction

endergonic reaction

absorb energy

exergonic reaction

release energy

synthesis reactions

atoms, ions, or molecules combine to form new, larger molecules

A + B —> AB

anabolism

synthesis of molecules in a cell

decomposition reactions

a molecule is split into smaller molecules, ions, or atoms

AB —> A + B

Catabolism

decomposition reactions in a cell

Exchange Reactions

are part synthesis and part decomposition

NaOH + HCl —> NaCl + H2O

Reversible Reactions

can readily go in either direction

each direction may need special conditions

A + B ←- AB

—>

Metabolism

the sum of the chemical reactions in an organism

Catabolism

provides energy and building blocks for anabolism

Anabolism

uses energy and building blocks to build large molecules

Role of ATP in Coupling Reactions

Metabolic Pathway

sequence of enzymatically catalyzed chemical reactions in a cell

determined by enzymes

Enzyme components

biological catalysts

apoenzyme

cofactor

holoenzyme

biological catalysts

specific for a chemical reaction, not used up in that reaction

apoenzyme

protein

cofactor

nonprotein component

coenzyme: organic cofactor

holoenzyme

apoenzyme plus cofactor

components of a holoenzyme

Important coenzymes

NAD+

NADP+

FAD

Coenzyme A

Mechanism of enzymatic action

Oxidoreductase

oxidation-reduction reactions

transferase

transfer functional groups

hydrolase

hydrolysis

lyase

removal of atoms without hydrolysis

isomerase

rearrangement of atoms

ligase

joining of molecules, uses ATP

Factors Influencing enzyme activity

temperature (37) and denature proteins (unfolded proteins)

pH (5)

substrate concentration

inhibitors

competitive inhibtor

temporary

competitive inhibitor has a similar shape to the normal substrate and the molecules compete for the active site

noncompetive inhibitors

permanent

product binds to regulatory site and permanently changes the shape of the active site

oxidation

removal of electrons

reduction

gain of electrons

redox reaction

an oxidation reactions paired with a reduction reaction

How is ATP generated?

by the phosphorylation of ADP

ADP + energy + P —> ATP

substrate level phosphorlyation

energy from the transfer of a high energy PO4- to ADP generates ATP

C-C-C + P + ADP —> C-C-C + ATP

Oxidative Phosphorylation

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

Carbohydrate Catabolism

3 steps

1) Glycolysis

2) Krebs cycle

3) Oxidative phosphorylation

glycolysis

the oxidation of glucose to pyruvic acid produces ATP and NADH

2 ATP are used

glucose is split to form 2 glucose-3-phosphate

Energy Conserving stage of glycolysis

2 glucose-3-phosphate oxidized to 2 pyruvic acid

4 ATP produced

2 NADH produced

Glucose + 2 ATP + 2 ADP + 2 PO4- + 2 NAD + —>

2 pyruvic acid + 4 ATP + 2 NADH + 2 H+

Pentose phosphate pathway (alternatives to glycolysis)

uses pentose and NADPH

operates with glycolysis

B. subtitles, E. coli

Net gain of 1 molecule of ATP / glucose molecule

Entner-Doudoroff pathway (alternatives to glycolysis)

produces NADPH and ATP

does not involved glycolysis

Pseudomonas, Rhizobium, Agrobacterium

Net gain of 1 ATP / glucose molecule

Intermediate step

pyretic acid (from glycolysis) is oxidized and decarboxylated

Krebs cycle (TCA or Citric Acid Cycle)

oxidation of acetyl CoA produces NADH and FADH2

electron transport chain

series of carrier molecules oxidized and reduced as electrons pass down the chain

chemiosmosis

energy released used to produce ATP

aerobic respiration

the final electron acceptor in the electron transport chain is molecular oxygen (O2)

anaerobic respiration

the final electron acceptor int he electron transport chan is not O2. Yields less energy than aerobic respiration because only part of the Krebs cycle operates under anaerobic conditions.

Respiration

Glycolysis + NAD+ —> ATP + NADH

Glycolysis location in Eukaryotes

cytoplasm

Glycolysis location in Prokaryote

cytoplasm

Intermediate step location in Eukaryotes

mitochondria

Intermediate step location in Prokaryotes

cytoplasm

Krebs cycle location in Eukaryotes

mitocondrial matrix

Krebs cycle location in Prokaryotes

cytoplasm

ETC in Eukaryotes

Mitochondrial inner membrane

ETC in Prokaryotes

plasma membrane

Carbohydrate Catabolism

ATP produced from compete oxidation of one glucose using aerobic respiration

Fermentation

any spoilage of food by microorganism (general use)

any process that produces alcoholic beverages of acidic dairy products (general use)

a large scale microbial process occurring with or without air (commonly used in industry)

Fermentation requirements

does not require oxygen

does not use the Krebs cycle or ETC

uses an organic molecule as the final electron acceptor

Alcohol fermentation

produces ethanol + CO2

lactic acid fermentation

produces lactic acid

Homolactic fermentation

produces lactic acid only

Heterolactic fermentation

produces lactic acid and other compounds

Microbial Growth

increase in number of cells, not cell size

-populations

-colonies

Physical requirements of microbial growth

temperature (minimum, optimum, and maximum growth temperature)

pH

osmotic pressure

Chemical requirements of microbial growth

carbon

Nitrogen, sulfur, and phosphorus

trace elements

oxygen

organic growth factor

Psychrotophs

grow between 0 C and 20-30 C

cause food spoilage

pH

most bacteria grow between pH 6.5 and 7.5

molds and years grow between pH 5 and 6

acidophilus grow in acidic environments

hypertonic envrionemts

or an increase in salt or sugar, cause plasmolysis

Extreme or obligate halophiles

require high osmotic pressure

Facultative halophiles

tolerate high osmotic pressure

barophiles

can survive under extreme pressure and will rupture if expoed to normal atmospheric pressure

Plasmolysis

water leaves the cell due to a high NaCl concentration on the outside of the cell

Oxygen requirements

most cells have developed enzymes that neutralize these chemicals

• superoxide dismutase, catalase

if a microbe is not capable of dealing with toxic oxygen, it is forced to live in oxygen free habitats

as oxygen is utilized it is transformed into several toxic products

singlet oxygen (O2)

superoxide ion (O2-)

peroxide (H2O2)

hydroxyl radicals (OH-)

biofilm

microbial communties

form slime or hydrogels

• bacteria attracted by chemicals via quorum sensing

share nutrients

sheltered from harmful factors

Obligate aerobes

an organism that cannot grow without oxygen and needs oxygen at atmospheric levels

facultative anaerobes

can grow with or without oxygen

• can switch between aerobic and anaerobic respiration to grow

Obligate anaerobes

do not use oxygen for cellular respiration and cannot grow in the presence of oxygen

Aerotolerant anaerobes

do not use oxygen for respiration, but can grow if oxygen is present

Microaerophlies

an organism that uses oxygen for cellular respiration, but at a concentration lower than in the atmosphere

• require oxygen in small amounts

Organic Growth Factors

vitamins

amino acids

purines

pyrimidines

biofilms

microbial communities

form slime or hydrogels

• bacteria attracted by chemicals via quorum sensing

• share nutrients

• sheltered from harmful factors

Biosafety levels

1) no special precautions

2) lab coat, gloves, eye protection

3) biosafety cabinets to prevent airborne transmission

4) sealed, negative pressure

• exhaust air is filtered twice

Reproduction in Prokaryotes

binary fission

budding

conidiophores (actinomycetes)

fragmentation of filaments

Lag phase

cells are visibly active by are not mature enough to divide

very few cells

exponential growth/ log phase

cells are live and reproducing rapidly

stationary phase

the amount of live cells = the number of dead cells

death phase

a limiting factors intensify cells die exponentially

direct method of measuring microbial growth

plate counts

filtration

direct microscopic count

indirect method of measuring microbial growth

turbidity

the pour plate method

1) inoculate empty plate

2) add melted nutrient agar

3) swirl to mix

4) colonies grow on and ion solidified medium

the spread plate method

1) inoculate plate containing solid medium

2) spread inoculum over surface evenly

3) clones grow only on surface of medium

direct microscopic count

hemacytometer: has channels, small amount of liquid

enumeration of bacteria:

• viable colony count

• direct cell count: count all cells present, automated or manual

Turbidometry

most simple

degree of cloudiness, turbidity, reflects the relative population size