MBB 110

MBB 110 2nd Part

Energy Generation/Transport
For eukaryotes, mitochondria generates energy.
For prokaryotes, cell membrane performs energy synthesis
Glycolysis
ATP is needed
Glucose  Pyruvate
Net production of 2 ATP
Citric acid cycle
Substrate level phosphorylation
Electron Transport Chain
Occurs in cell membrane
Sequence involve repair organization
Anaerobic respiration: NOT O2
Aerobic respiration: O2 final acceptor
ATP is produced by the Proton Motive Force Chemiosmosis
H+ accumulates outside, OH- inside resulting in energized state
When H+ enters, ATP is generated

*Heterotrophy (i.e., chemoheterotrophy) is the use of an organic compound as a source of carbon and energy.
*Lithotrophy is the use of an inorganic compound as a source of energy.

Energy-Generating Metabolic Pathways
1) Aerobic respiration
a) Heterotrophic reduced carbon compounds as energy sources (carbs, fats, proteins)
8 ATP (Glycolysis) 30 ATP (Krebs, ETC)
b) Chemolithotrophic including C1 metabolism
> derive energy from oxidation of inorganic compounds
> derive cellular carbon from CO2
2) Anaerobic respiration
a) Also Heterotrophic and Chemolithotrophic types but does not use up O2
3) Fermentation

Usual (SLP-meditated ATP)
Substrate-level phosphorylation
Results in formation of ATP by direct transfer P to ADP

Unusual (PMF-driven ATP)
Proton motive force
Transport of H+ ions across membrane cause catalysis of ATP from ADP by ATP synthases on membrane
*Phototrophy
- process by which organisms trap light energy (photons) and store it as chemical energy in the form of ATP and/or reducing power in NADP
*Photosynthetic phototrophy entails the use of chlorophyll to proceed with phototrophy

Photosynthetic phototrophy
Oxygenic photosynthesis
Anaerobic anoxynogenic photosynthesis
Aerobic anoxynogenic photosynthesis

*Anoxygenic photosynthesis is the phototrophic process where light energy is captured and converted to ATP, without the production of oxygen.

Nonphotosynthetic phototrophy
Rhodopsin mediated phototrophy
Bacteriorhodopsin
Halorhodopsin
Proteorhodopsin
Denitrification
NO3 NO2NO N2O N2
Sulfate reduction
CH3COO- +SO42- + 3H+  H2S+2CO2+2H2O
Methanogenesis
4H2 + CO2  CH4 + 2H2O
Acetanogenesis
4H2 + 2CO2  CH3COOH + 2H2O

Extremophile Tolerance
Temperature Tolerance
Process causing irreversible thermo inactivation of enzymes: depending on pH
Inactivating reactions may include deamidation of Asn residues
Hydrolysis of polypeptide chain at Asp residues
Elimination of cysteine residues, as well as certain conformational structures’
More Cystein-Cystein residues
Replacement of Asn to Thr/Ile more heat resistant
Asn to Asp less heat resistant
Heat shock proteins
Hydrophobic core is resistant to denaturation
More salt bridges on surface
Increased expression of nuclear proteins
Increased chaperone activity to correlate to level of Hsp70 expression increase protective enzymes in de novo protein synthesis
More stable DNA with high [K+] and other org mol against osmotic stress
(+) Histones keep DNA tightly wound
Increased G:C content of ribosomes
Strong divalent bonds between lipid units
Saturated fatty acids
More Beta pleated sheets

*Reverse DNA gyrase: promotes supercoiling to prevent double helix hydrolysis

Salt Tolerance

1st: passive in w/c cytoplasmic content would always equal in the medium
Ion movement (K+ moving in direction opposite to water flow) through channels sensitive to osmotic pressure.
Water movement through aquaporin-like channels
Efflux if NaClext increase
Influx if NaClext decrease
2nd: use of compatible solutes uptake or de novo synthesis glycerol in yeast cells
3rd: changing cell physiology to control movement of H2O to exist w/ ionically dilute cytoplasm

*Archaea (osmolytes) not used by other organisms. Stabilize macromolecules from denaturation
Stability in the cell and their lack of strong interactions w/ cellular components
Movement/accumulation of solutes  induction of stress protein (chaperonin) & transcriptional regulation of key enzymes
High osmolarity  osmosensors (products of SIn1 and Sho1 genes)
SIn1 protein contain extracellular sensor domain, histidine kinase domain & receiver
Low [Na+ ] decreased uptake, increase Na+ efflux

Acid Tolerance

Efficient proton-ion pumps
Acid tolerant proteins
Greater [Acidic amino acids]
Fold to protect salt bridge from acid hydrolysis

Base Tolerance
Na+ instead of H+ to drive membrane pumps
Antiport protein pumps

Radiation Tolerance
Multiple copies of genetic material
Rapid and high fidelity mutation repair mechanisms

Biological Membranes
Organized assemblies consisting of proteins + lipids
They have various fxn’s in the cell
Separate them from environment
Selectively permeable
Regulate molecular and ionic composition of intracellular medium by pumps and gates
Internal membrane for organelles (Eukaryotes)
Control flow of information between cells and environment (receptors to stimuli)
Ex. Movement of bacteria to food
Ex. Perception of light
Energy conversion process in bio systems contain arrays of enzymes & proteins
Photosynthesis
Oxidative phosphorylation

Common Features of Biological Membranes
1) Sheet like structure: consists of proteins and lipids w/c occasionally have carbohydrates
2) Amphiphile membrane lipid: have hydrophilic and hydrophobic moiety that spontaneously form biomolecular sheets in aqueous media
3) Specific protein functions: serves as pumps, gates, receptors, etc.
4) Noncovalent assemblies: held together by noncovalent interactions cooperative in nature
5) Asymmetric membranes: inside and outside faces are different
6) Fluid structures: 2-dimensional sol’n of oriented proteins and lipids that diffuse rapidly

3 major kinds of membrane lipids
1) Phospholipid
-most abundant
2) Glycolipid
-sugar containing lipids (fatty acid + sugar unit)
3) Fatty acids

*Cholesterol- abundant in eukaryotic plasma membranes but not present in most prokaryotes.
*Membrane proteins: responsible for most dynamic process carried out by membranes, mediate fxns (transport, communication, energy transduction)

Microbial Physiology
Study of microbial life
Nutrition
Transport
Growth
Metabolism
Regulation
Secretion
Endospore production
Signal communication
Taxis/Quorum sensing

Carbon
A typical cell (50% C); major element in all classes of macromolecules
Organic: source of heterotrophs
Inorganic (CO2): source for autotrophs during photosynthesis; e- acceptor during methanogenesis & acetogenesis.
Nitrogen
A typical cell (12% N)
Important element in proteins & nucleic acids + other
Organic: amino acids, peptides, N-cmpd
Inorganic: NH4, NO32-, and N2