Microbiology Lecture 6

Front 1

What are the energy and C sources?
1.photoautotroph
2.photoheterotroph
3.chemoautotroph
4. chemoheterotroph

Back 1

Carbon Source, Energy Source
1. CO2, light
2. Organic, light
3. CO2, chemicals
4. Organic, chemicals

Front 2

What are Growth factors?

Back 2

Growth factors – specific, low molecular weight compounds that cannot be synthesized by the cells
• Three most common types:
• Vitamins
• Amino acids
• Purines and pyrimidines

Front 3

What is responsible for the lipid bilayers high degree of permeability?

Back 3

The lipid bilayer is hydrophobic—
responsible for the high degree of
selective permeability.

Front 4

What is Passive diffusion?

Back 4

a phenomenon in which molecules move from an area of high concentration to an area of low concentration because of random thermal agitation
1. Requires a large concentration gradient for significant levels of uptake
2. Limited to only a few small useful molecules (e.g., glycerol,H2O, O2, and CO2)

Front 5

What is Facilitated diffusion?

Back 5

a process that involves a carrier molecule (permease) to increase the rate of diffusion; net effect is limited to movement from an area of higher concentration to an area of lower concentration
1. Requires a smaller concentration gradient than passive diffusion
2. The rate plateaus when the carrier becomes saturated
(i.e., when it is binding and transporting molecules as rapidly as possible)
3. Generally more important in eucaryotes rather than procaryotes

Front 6

What are Active transports? Where does it get its energy from(2)?

Back 6

Active transport uses cell energy to move solutes against a concentration gradient.
• Solute-specific transmembrane proteins are used.
•Most organic and inorganic nutrients are taken into cells by active transport mechanisms.
• Energy is from ATP or proton gradients

Front 7

What are the Three Classes of Membrane Transport Systems?

Back 7

Simple transport- Driven by energy in the proton motif force
Group translocation- Chemical modification of the transported substance driven by phosphoenolpyruvate.
ABC transporter- Binding of proteins inside and energy comes from ATP

Front 8

ATP-Binding Cassette transporters (ABC transporters) Consist of what three kinds of proteins?

Back 8

Hydrophobic transmembrane protein

ATP hydrolyzing protein – attached to the inner side of the transmembrane protein

Periplasmic solute-binding protein – in the periplasmic space or anchored to the membrane

Front 9

What is the Ion-coupled transport system?

Back 9

Ion-coupled transport system (simple transport systems) uses a hydrogen ion (H+) i.e., proton motive force (pmf), or some other cation, i.e., chemiosmotic potential, to move solutes against a concentration gradient.

Front 10

What are Symporters?

Back 10

Symporters- carry amino acids, sugars, or anions that are accompanied by a proton or sodium ion.

Front 11

What are Antiporters?

Back 11

Antiporters – energy from a proton gradient is used to move a proton inward and a cation such as Na+ outward, creating a Na+ gradient.

Front 12

What is The phosphotransferase system (PTS)?

Back 12

The phosphotransferase system (PTS) is involved in transporting sugars into the cell. It uses energy from phosphoenolpyruvate (PEP) and 5 different enzymes.

Front 13

What are the steps of The phosphotransferase system?

Back 13

(Cytoplasm) PEP transfers a phosphate to Enzyme 1 which transfers it to HPr
HPR transfer the phosphate to enzyme IIA(attached to membrane now) which passes it to enzyme IIb.
Enzyme IIb passes it to Enzyme IIc which places it on the glucose as it is being transported inside creating Glucose-6-phosphate

Front 14

What is Iron uptake important for?

Back 14

Many microbes produce chelating agents called siderophores that form iron–chelate complexes which are soluble.

Front 15

What is Enterobactin? How does it enter the cell?

Back 15

Enterobactin is a siderophore produced
by E. coli. It chelates Fe3+ through
oxygen molecules on the catechol rings.
• The complex is bound by a binding protein, transferred to a specific receptor on the cell envelope, and transported across the membrane by an ABC system.

Front 16

High versus low affinity transporters

Back 16

High affinity transporters for low nutrient concentration

Low affinity transporter for high nutrient concentration
nutrient scavenging