Micro Bio 2

Louis Pasteur showed

Alcohol and CO₂ are produced in grape juice while yeast cells increase in number and sugar decreased

In 1897, Eduard Buchner, a German chemist

showed that crushed yeast cells could convert sugar to ethanol

All cells need to accomplish two fundamental tasks

Synthesize new parts

Harvest energy to power reactions

metabolism

Sum of chemical reactions in a cell

Catabolism

Processes that degrade compounds to release energy

Cells capture to make ATP

Anabolism or biosynthesis

Assemble subunits of macromolecules

Use ATP to drive reactions

Exergonic reactions:

reactants have more free energy than products

Endergonic reactions:

products have more free energy than reactants

enzyme

speed up conversion of substrate into product by lowering activation energy

ATP

ribose, adenine, three phosphate groups

Substrate-level phosphorylation

a direct metabolic process producing ATP by transferring a high-energy phosphate group from a substrate molecule to ADP, occurring independently of the electron transport chain.

Oxidative phosphorylation

the final, oxygen-dependent stage of cellular respiration in mitochondria, where NADH and \(FADH_{2}\) are oxidized to drive ATP synthesis.

Photophosphorylation

Light hits chlorophyll, energizing electrons that move through an electron transport chain (ETC). This electron flow pumps protons (\(H^{+}\)) across the thylakoid membrane, creating a gradient that drives ATP synthase to produce ATP

oxidized

Substance that loses electrons

reduced

Substance that gains electrons

When electrons move from molecule that has low affinity for electrons (energy source) to a molecule that has high affinity for electrons

 energy is released

More energy released when

difference in electronegativity (affinity for electrons) is greater

Precursor metabolites are

intermediates of catabolism that can be used in anabolism

Precursor metabolites characteristic

Serve as carbon skeletons for building macromolecules

the electrons carried by NADPH

used in biosynthesis

Central metabolic pathways

oxidize glucose to CO₂

Catabolic, but precursor metabolites and reducing power

can be diverted for use in biosynthesis

Glycolysis

Splits glucose (6C) to two pyruvate molecules (3C)

Generates modest ATP, reducing power, precursors

Pentose phosphate pathway

Primary role is production precursor metabolites, NADPH

Tricarboxylic acid (TCA) cycle

With transition step, oxidizes pyruvate; releases CO2

Generates reducing power, precursor metabolites, ATP

Respiration (or cellular respiration)

transfers electrons from glucose to electron transport chain (ETC) to terminal electron acceptor

Electron transport chain generates proton motive force

Harvested to make ATP by oxidative phosphorylation

Fermentation

recycles electron carriers in a cell that cannot respire so that it can continue to make ATP

Fermentation characteristic

Use of pyruvate or a derivative as terminal electron acceptor to receive H from NADH

Fermentation characteristic 2

Regenerates NAD+ so that glycolysis can continue

ATP Generated by Substrate-Level Phosphorylation in Aerobic respiration

2 in glycolysis (net)
2 in the TCA cycle 

ATP Generated by Substrate-Level Phosphorylation in Fermentation

2 in glycolysis (net) 

ATP Generated by Oxidative Phosphorylation aerobic respiration

34

ATP Generated by Oxidative Phosphorylation in Fermentation

0

1)the ATP yield of anaerobic respiration 1 than that of aerobic respiration 2 than that of fermentation

less

2)the ATP yield of anaerobic respiration 1 than that of aerobic respiration 2 than that of fermentation

more

cofactor

Some enzymes require the assistance of an attached non-protein component

Coenzymes

organic cofactors that help some enzymes transfer certain molecules or electrons from one compound to another

Coenzymes characteristic

Derived from certain vitamins

Enzymes have narrow range of optimal conditions effected by

Temperature, pH, salt concentration

10 degrees Celsius

increase doubles speed of enzymatic reaction up to maximum

Enzyme activity controlled by

regulatory molecule binding to allosteric site

Regulatory molecule/allosteric inhibitor

Distorts enzyme shape, prevents or enhances binding of substrate to active site

Regulatory molecule/allosteric inhibitor is usually

end product of metabolic pathway

In competitive inhibition,

inhibitor binds to active site and blocks substrate

In non-competitive inhibition

inhibitor binds to a site other than the active site

Pentose Phosphate Pathway

Breaks down glucose and Produces NADPH and ribose-5-phosphate

Pentose Phosphate Pathway characteristic

Product glyceraldehyde-3-phosphate can enter glycolysis

Transition Step 1

CO₂ is removed from pyruvate

Transition Step 2

Electrons transfer to NAD Plus reducing it NADH

Transition Step 3

2-carbon acetyl group joined to coenzyme A to form acetyl-CoA

The transition step

Links previous pathways to TCA cycle

Tricarboxylic Acid (TCA) Cycle

Completes oxidation of glucose

TCA produces __ co2

2

TCA produces ___ ATP

2

TCA produces __ NADH(2 cycles)

6

TCA produces__ FADH2 (1 cycle)

2

in prokaryotes TCA NADH can produce how much ATP

18

in prokaryotes TCA FADH2 can produce

4 atp

Peter Mitchell in 1961

Proposed Electron transport chain uses reducing power of NADH, FADH2 to generate proton motive force

ATP synthase uses energy of proton motive force to generate ATP

Energy pumps protons across membrane(Prokaryotes)

cytoplasmic membrane

Energy pumps protons across membrane(Eukaryotes)

inner mitochondrial membrane

glycolysis location

Cytosol

Pyruvate oxidation location and krebs cycle location

Matrix

ETC location

inner membrane

Quinones

Lipid-soluble; move freely in membrane

Can transfer electrons between complexes

Cytochromes

Contain heme, molecule with iron atom at center

Several types; can be used to distinguish bacteria

Flavoproteins

Proteins to which a flavin is attached

FAD, other flavins synthesized from riboflavin

Spatial arrangement in membrane

shuttles protons to outside of membrane

When hydrogen carrier accepts electron from electron carrier it

picks up proton from inside cell (or mitochondrial matrix)

When hydrogen carrier passes electrons to electron carrier

protons released to outside of cell (or intermembrane space of mitochondria)

ETC First part

Oxidation

ETC Last part

phosphorylation

Complex I (NADH dehydrogenase complex)

• Accepts electrons from NADH, transfers to ubiquinone

• Pumps 4 protons

succinate to fumarate

Oxidation process that gives protons to complex 2

Complex II (succinate dehydrogenase complex)

• Accepts electrons FADH₂, “downstream” of those carried by NADH

• Transfers electrons to ubiquinone

Complex III (cytochrome reductase)

Accepts electrons from ubiquinone from Complex I or II

4 protons pumped; electrons transferred to cytochrome c

Complex IV (cytochrome c oxidase complex)

• Accepts electrons from cytochrome c, pumps 2 protons

• Transfers electrons to terminal electron acceptor (O₂

complex V(ATP synthase)/chemiosmosis

acts as a turbine as Protons flow down their gradient back into the matrix, catalyzing the phosphorylation of ADP to ATP.

Tremendous variation:

even single species can have several alternate carriers

Aerobic respiration in E. coli

Can use 2 different NADH dehydrogenases
Lack equivalents of complex III or cytochrome c

proton motive force products

Uses energy to add phosphate group to ADP

1 ATP formed from entry of approximately 3 protons

1)Can synthesize terminal 1 that uses 2 as terminal electron acceptor

oxidoreductase

2)Can synthesize terminal 1 that uses 2 as terminal electron acceptor

nitrate

In Eukaryotes

1 ATP for NADH

In glycolysis 2 NADH

2 ATP

In prokaryotes Transition step 1 NADH can produce

3 ATP

E. coli is

facultative anaerobe

Streptococcus pneumoniae characteristic

lacks electron transport chain so only use fermentation

ATP-generating reactions are

only those of glycolysis

chemolithotrophs

Prokaryotes unique in ability to use reduced inorganic compounds as energy sources like H2S, NH3, or sulfur

Chemolithotrophs 1

Hydrogen bacteria oxidize hydrogen gas.

Chemolithotrophs 2

Sulfur bacteria oxidize hydrogen sulfide.

Chemolithotrophs 3

Iron bacteria oxidize reduced forms of iron.

Nitrifying bacteria group 1

one oxidizes ammonia forming nitrite

Nitrifying bacteria group 2

another oxidizes nitrite producing nitrate

Chemolithotrophs extracted electrons

Pass electrons to an electron transport chain that generates a proton motive force.

Energy of gradient is used to make ATP

Thermophilic chemolithotrophs

grow near hydrothermal vents of the deep ocean and obtain energy from reduced inorganic compounds from the vents.

chemolithotrophs characteristic

incorporate CO2 into an organic form.

photosynthesis reactants

6 CO₂ + 6 H₂O + light