Nature of Life on Earth

Question 1

What is a chemoorganotroph?

Answer 1

Obtain energy from organic compounds.

Question 2

What is a chemolithotroph?

Answer 2

Obtain energy from inorganic compounds.

Question 3

What is a phototroph?

Answer 3

Contain pigments that allow them to use light as an energy source.

Question 4

What is an autotroph?

Answer 4

Use CO2 as their carbon source.

Question 5

What is a heterotroph?

Answer 5

Use organic carbon as their carbon source.

Question 6

How do thermophiles take heat in terms of their membranes? (3)

Answer 6

1. Thermophilic bacteria membranes are rich in saturated fat. 2. Thermophilic archea membranes are constructed from isoprene units bonded to glycerol phosphate by either linkages. 3. Overall structure of archea membrane is a lipid monolayer.

Question 7

What is a psychrophile?

Answer 7

Show growth temperature optima below 15 C.

Question 8

How can life survive the cold?

Answer 8

Organic gels or extracellular polysaccharides substances (EPS) facilitate microbial survival and even activity.

Question 9

How do extracellular polysaccharides substances (EPS) work? (3)

Answer 9

1. Depress the freezing point, allowing more water to retain in the ice. 2. Can modify the shape of an inhabitable ice pore to cellular advantage to prevent direct ice crystal damage to cell wall. 3. May provide a buffer against high salt concentrations of the surrounding brine.

Question 10

What do cytoplasms contain that prevent ice crystallization?

Answer 10

Cryoprotectants (glycerol).

Question 11

Do most psychrophiles contain Cryoprotectants (glycerol)?

Answer 11

No.

Question 12

How do psychrophiles take the cold in terms of proteins? (2)

Answer 12

1. Proteins have greater amounts of alpha helices vs. beta sheets. 2. The alpha helix structure is more flexible than beta sheet structure.

Question 13

How do psychrophiles take the cold in terms of their membranes? (2)

Answer 13

1. Rich in unsaturated fatty acids. 2. Unsaturated fatty acids help to maintain fluidity at low temperatures.

Question 14

What are some environments in which psychrophiles exist?

Answer 14

1. Glaciers. 2. Polar Lakes. 3. Permafrost.

Question 15

How do thermophiles take heat in terms of their proteins? (3)

Answer 15

1. Changes in amino acid allows for more ionic and hydrophobic interactions. Leading to more stable structures. 2. Some hyperthermophiles produce intra-cellular solutes that stabilize proteins. 3. Others produce chaperones which help protein folding.

Question 16

What is a Solfataras (fumaroles)?

Answer 16

An opening in Earth’s (or any other astronomical body’s) crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide.

Question 17

What bacteria are present at Yellowstone?

Answer 17

Thermophilic cyanobacteria.

Question 18

What did Thomas Brock do?

Answer 18

Isolated Thermus Aquaticus which became the original source of Taq DNA polymerase for PCR.

Question 19

What is the energy source for chemosynthesis-based food chains?

Answer 19

The oxidation of sulfur.

Question 20

What is a thermophile?

Answer 20

Most growth occurs around 60 C.

Question 21

What pH is neutral?

Answer 21

7.

Question 22

What raises the acidity of a solution?

Answer 22

Adding Hydrogen.

Question 23

How does active regulation help organisms survive at a low pH?

Answer 23

Pump hydrogen ions out of the cell at a constantly high rate and/or consume protons inside the cell.

Question 24

How does passive regulation help organisms survive at a low pH?

Answer 24

Enforce the cell membrane against an unfavorable environment.

Question 25

What three ways of passive regulation help organisms survive at a low pH?

Answer 25

1. Secretion of a biofilm to slow down the diffusion of molecules into the cell. 2. Secreting buffer molecules that help to maintain intracellular pH. 3. Changing their cell membrane to incorporate substances that protect the cell.

Question 26

How does Thermoplasma acidophilum survive hot acidic conditions?

Answer 26

Has ether linkages and a lipid that would form a monolayer.

Question 27

What is an Alkaliphile?

Answer 27

Microorganisms that grow optimally at pH values above 9.

Question 28

What may protect Halophiles from UV radiation?

Answer 28

Carotenoids.

Question 29

What are two classic environments for Halophiles?

Answer 29

1. Great Salt Lake. 2. Dead Sea.

Question 30

How do Halophiles survive in high salt environments (in low water activity environments)?

Answer 30

They must increase their internal solute concentrations in order to obtain water from the surrounding environment.

Question 31

How can Halophiles increase their internal solute concentrations?

Answer 31

1. Pumping inorganic ions into the cell from the environment. 2. Synthesizing or concentrating an organic solute.

Question 32

How do Halobacterium maintain their solute concentration?

Answer 32

Their membranes contain bacteriorhodopsin (light-reactive) proteins. UV light activates BP, which acts as a proton pump, driving ATP synthesis and salt pumps.