Chapter 10 - Environmental Factors

Question 1

osmotic pressure

Answer 1

Cells subject to this, as the wall is permeable. Water will generally move in the direction necessary to try and equilibrate the cell’s solute concentration to the solute concentration of the surrounding environment.

Question 2

passive diffusion

Answer 2

plasma membrane is freely permeable to water. Water wants to move from areas of low concentration to higher concentration.

Question 3

hypotonic

Answer 3

If the solute concentration of the environment is lower than the solute concentration found inside the cell. Water will flow inside from outside

Question 4

What happens in a hypotonic state?

Answer 4

Cell will swell and increase internal pressure. If not rectified, cell will lyse and burst.

Question 5

Hypertonic

Answer 5

If the solute concentration of the environment is higher than the solute concentration found inside the cell. Water will flow out of the cell.

Question 6

What happens in a hypertonic state?

Answer 6

The cell will dehydrate. Long periods of dehydration can cause permanent damage to the plasma membrane.

Question 7

mecahnosensitive channels

Answer 7

Located in plasma membrane. open as the membrane stretches due to increase pressure, allows solutes to leave the cell and lower the osmotic pressure - hypotonic state

Question 8

Halophiles

Answer 8

Require high levels of sodium chloride to grow - a concentration above 0.2 M - take in both K and Cl ions to offset hypertonic environment. Their cellular components all require presence of high concentrations of both K and Cl to function.

Question 9

pH

Answer 9

Describes as the negative logarithm of the hydrogen ion concentration of a solution, expressed in molarity. 0 Acidic 14 Basic. Each represents a tenfold in hydrogen concentration.

Question 10

Cell walls and pH

Answer 10

Cells prefer a pH that is similar to their internal environment

Question 11

Neutrophiles

Answer 11

Neutral lovers - prefer a pH in the range of 5.5 to 8.0

Question 12

Acidophiles

Answer 12

Acid lovers - prefer pH in range of 0 to 5.5. They utilize mechanisms to maintain internal pH and transport cations (K) into the cell, decreasing H+ movement into the cell. Also use proton pump to pump H+ out.

Question 13

Aklaliphiles

Answer 13

Alkaline Lovers - prefer pH in range of 8.0 - 11.5. Must pump protons in, in order to maintain pH. Typically employ antiporters which pump protons in and Na out.

Question 14

Temperature

Answer 14

Has the biggest effect on enzymes and their activity. Optimal Temp leads to fastest metabolism and growth rate. Bacterium growth range is typically around 30 degrees.

Question 15

Psychrophiles

Answer 15

Cold Lovers - optimum of 15 degrees C or lower, growth range of -20 to 20. Most found in oceans. Evolved enzymes that can function at low temps, and modified PM.

Question 16

Psychrophiles Plasma Membrane

Answer 16

Increased amount of unsaturated and shorter-chain fatty acids.

Question 17

Cryoprotectants

Answer 17

Located in psychrophiles - special proteins or sugars that prevent development of ice crystals that might damage the cell.

Question 18

Psychrotophs

Answer 18

Cole Tolerate - Range of 0-35 degrees C, optimum at 16 degrees or higher.

Question 19

Mesophiles

Answer 19

Most common to us - optimal at 37 degrees C and range of 20 - 45. Almost all human microflora and pathogens fall into this category.

Question 20

Thermophiles

Answer 20

Heat Lovers - Range of 45 - 80 degrees, optimum of 60 degrees.

Question 21

Hyperthermophiles

Answer 21

Very Hot Lovers - Optimal 88 - 106 degrees C, min of 65 and max of 120.

Question 22

Chaperone Proteins

Answer 22

Present in both Thermophiles and Hyperthermophiles - present on enzymes to provide heat stability to resist denaturing and unfolding.

Question 23

Plasma Membrane of Hyperthermophiles and Thermophiles

Answer 23

Contain more saturated fatty acids, with increased melting points

Question 24

Oxygen Concentration

Answer 24

Requirement of O2 relates to type of metabolism used. Energy generation is tied to the movement of electrons through the ETC, where final acceptor can be O2 or non-o2 molecule.

Question 25

Aerobic Respiration

Answer 25

use O2 as the final electron acceptor.

Question 26

Obligate Aerobes

Answer 26

Require the presence of atmospheric oxygen (20%)

Question 27

Microaerophiles

Answer 27

Require o2, but at a lower level than normal atmospheric levels - only grow at levels of 2-10%

Question 28

Anaerobes

Answer 28

Organisms that can grow in the absence of O2.

Question 29

Facultative Anaerobes

Answer 29

Most versatile - able to grow in the presence or absence of O2 - switch their metabolism to match environment. Would prefer aerobic environment because it provides greatest amount of E and faster growth.

Question 30

Aerotolerant Anaerobes

Answer 30

Grow in presence of absence of O2 - Have no preference

Question 31

Obligate Anaerobes

Answer 31

Only grow in absence of O2, find Oxygenated environments to be toxic.

Question 32

What dictates the ability to live in an oxygenated environment?

Answer 32

presence/absence of several enzymes that can handle O2 byproducts

Question 33

Reactive Oxygen Species - ROS

Answer 33

Oxygen by products

Question 34

Superoxide Dismutase - SOD

Answer 34

Protection from ROS, breaks down superoxide radicals

Question 35

Catalase

Answer 35

Protection from ROS, breaks down hydrogen peroxide.

Question 36

barophiles

Answer 36

pressure lovers - microbes that have adapted to prefer and even require high pressures. Have increased unsaturated fatty acids in their plasma membranes, as well as shortened fatty acid tails.

Question 37

Deionococcus radiodurans

Answer 37

bacterium capable of completely reassembling its DNA after exposure to massive doses of radiation.

Question 38

What does UV do to DNA?

Answer 38

Attaches thymine bases next to one another on DNA, inhibits replications and transcription.

Question 39

Enzyme photolyase

Answer 39

repair limited damage, split apart thymine dimers