micro exam two slides based study guide

ATP

Energy currency; couples catabolism to anabolism.

Enzyme

Biological catalyst that lowers activation energy.

Enzyme specificity

Active site fits particular substrate(s) and reaction(s).

Gene-enzyme relationship

Genes encode enzyme amino acid sequences.

Apoenzyme

Inactive protein portion of a holoenzyme.

Cofactor

Nonprotein helper required by some enzymes.

Coenzyme

Organic cofactor; NAD+, NADP+, FAD, or CoA.

Holoenzyme

Active apoenzyme plus its cofactor.

Enzyme activity factors

Temperature, pH, substrate, inhibitors, denaturation.

Enzyme saturation

All active sites occupied; rate plateaus.

Denaturation

Loss of protein shape and normal function.

Competitive inhibition

Inhibitor competes for the active site.

Competitive inhibition reversal

More substrate can overcome it.

Sulfanilamide

Competitive inhibitor that mimics PABA.

Noncompetitive inhibition

Inhibitor binds allosterically and changes enzyme shape.

Feedback inhibition

End product inhibits an earlier pathway enzyme.

Aerobic carbohydrate catabolism

Glycolysis, transition step, Krebs cycle, ETC.

Glycolysis location

Cytoplasm of prokaryotes and eukaryotes.

Glycolysis conditions

Occurs with or without oxygen.

Glycolysis net yield

2 pyruvate, 2 ATP, 2 NADH.

Glycolysis preparatory stage

Uses 2 ATP; glucose becomes 2 PGAL.

Glycolysis payoff stage

2 PGAL become 2 pyruvate; makes 4 ATP and 2 NADH.

Transition step

Pyruvate oxidized and decarboxylated to acetyl-CoA.

Transition-step yield

2 acetyl-CoA, 2 NADH, 2 CO2 per glucose.

Krebs cycle

Oxidizes acetyl-CoA; captures electrons in NADH and FADH2.

Krebs-cycle yield

6 NADH, 2 FADH2, 2 ATP, 4 CO2 per glucose.

Aerobic respiration total before ETC

4 ATP, 10 NADH, 2 FADH2 per glucose.

Electron transport chain

Electron flow powers proton pumping across a membrane.

ATP synthase

H+ flow through it drives ATP production.

Aerobic terminal electron acceptor

O2; reduced to H2O.

NADH ATP yield

3 ATP in this course's convention.

FADH2 ATP yield

2 ATP in this course's convention.

Krebs cycle location

Mitochondrial matrix in eukaryotes; cytoplasm in prokaryotes.

ETC location

Inner mitochondrial membrane in eukaryotes; plasma membrane in prokaryotes.

Anaerobic respiration

Respiration using a final electron acceptor other than O2.

Fermentation

No Krebs cycle or ETC; organic final electron acceptor.

Fermentation uses

Food and beverage production, spoilage, microbial identification.

Light-dependent reactions

Make ATP by photophosphorylation.

Light-independent reactions

Use carbon fixation to make organic molecules.

Carbon fixation

CO2 incorporated into organic molecules.

Oxygenic photosynthesis

Cyanobacteria; produces oxygen.

Anoxygenic photosynthesis

Green and purple sulfur bacteria; no oxygen production.

Thylakoid

Folded cyanobacterial plasma membrane for light reactions.

Noncyclic photophosphorylation

Electrons leave chlorophyll; NADPH formed.

Cyclic photophosphorylation

Electrons return to chlorophyll; makes proton motive force.

Calvin-Benson cycle

Most common CO2-fixation pathway.

Rubisco

Enzyme attaching CO2 to RuBP.

Calvin-cycle glucose requirement

Six turns make one glucose and regenerate six RuBP.

Asepsis

Absence of significant contamination.

Sterilization

Removal of all microbial life, including endospores.

Disinfection

Removal of pathogens from inanimate objects.

Antisepsis

Removal of pathogens from living tissue.

Degerming

Physical removal of microbes from a small area.

Bacteriostasis

Inhibition of growth without killing.

Decimal reduction time

D-value; time to reduce a population by 90%.

D25°C = 1 minute

At 25°C, 1 minute causes a 90% reduction.

Resistant microbial forms

Bacillus/Clostridium endospores and Mycobacterium.

Control-treatment factors

Organism type, microbe number, environment, infection risk.

Antimicrobial targets

Membranes, proteins, nucleic acids.

Membrane damage

Leaks cell contents and disrupts normal function.

Protein damage

Denatures proteins and stops their function.

Nucleic-acid damage

Prevents replication or gene expression.

Boiling

100°C for 10 minutes kills most microbes, not necessarily endospores.

Autoclave

Steam at 121°C, 15 psi, 15 minutes; kills endospores.

Flash autoclave

135°C for 3 minutes.

Autoclave requirement

Steam must contact the surface.

Heat-sensitive tape

Shows autoclave exposure conditions.

Pasteurization

Reduces pathogens and spoilage microbes; not sterilization.

Batch pasteurization

63°C for 30 minutes.

HTST pasteurization

72°C for 15 seconds.

UHT pasteurization

140°C for 3 seconds.

Thermal death time

Time needed to kill all microbes at a specified temperature.

Refrigeration

Inhibits microbial growth.

Deep-freezing

Inhibits growth; usually does not sterilize.

Lyophilization

Freeze-drying; removes water and prevents metabolism.

High pressure

Denatures proteins.

Desiccation

Water removal that prevents metabolism.

Osmotic pressure

Draws water out of cells; causes plasmolysis.

Membrane filtration

Removes microbes from heat-sensitive liquids.

HEPA filter

Removes microbes from air.

Dry heat

Oxidizes cell components; 170°C for 2 hours.

Ionizing radiation

X rays, gamma rays, electron beams; breaks DNA.

Hydroxyl radical

Generated from ionized water; damages DNA.

UV radiation

Nonionizing radiation near 260 nm; forms thymine dimers.

Microwaves

Kill mainly by heating.

Phenol

Denatures proteins and disrupts membranes; irritating.

Phenolics

Phenol derivatives with greater germicidal activity and less irritation.

Lysol

Phenolic disinfectant containing compounds such as paracresol.

Iodine tincture

Iodine dissolved in aqueous alcohol.

Iodophor

Iodine combined with organic molecules; less irritating.

Chlorine oxidizes proteins

Mechanism of chlorine disinfectants.

Bleach

Hypochlorous acid or sodium hypochlorite.

Chloramine

Chlorine combined with ammonia.

Chlorine concentration

About 500 ppm kills most microbes.

Alcohol antiseptics

Ethanol or isopropanol; denature proteins.

Alcohol concentration

70% works best because water is required.

Alcohol limitation

Evaporates quickly; does not kill endospores.

Heavy metals

Ag, Hg, Cu; bind proteins but can be toxic.

Surfactants

Soaps and detergents emulsify oils; limited germicidal action.

Quats

Cationic NH4+ detergents that disrupt membranes.