Stress

Question 1

What is stress

Answer 1

Any deviation from optimal growth conditions that result in a reduced growth rate

Question 2

How do stress response systems interact together

Answer 2

By a complex of global regulatory networks

Question 3

Types of stress

Answer 3

Osmotic
Oxidative
PH
Thermal
Nutrient

Question 4

Osmotic stress happens when

Answer 4

Sudden change in solute conc
Hyper out
Hypo in

Question 5

Osmoregulation is

Answer 5

A process to minimise cell damage

Question 6

4 ways of osmoregulation

Answer 6

Controlling ions efflux and uptake
Accumulation of osmolytes
Osmosensors
Biofilms

Question 7

Osmolytes func and who

Answer 7

Proline, betaine , trehalose
Allow cell to retain water
Protect proteins from denaturation or aggregation
Reduce ROS

Question 8

Osmosensors are and lead to

Answer 8

Proteins that detect osmotic changes
Activation of some genes expression and metabolic adjustments

Question 9

Biofilm in osmotic stress

Answer 9

Physical barrier
Gradient of osmotic conditions
Metabolic interactions
Genetic adaptation like plasmid transfer

Question 10

Oxidative stress is
Due to

Answer 10

Imbalance between ROS and antioxidant mechanism
Disturbance in cells redox state
Aerobic metabolism or exogenously from enivironment

Question 11

The ROS

Answer 11

Superoxide anion o2-

Hydrogen peroxide h2o2
Hydroxyl radical HO’

Question 12

How ROS transfer to each other

Answer 12

O2&raquo_space; O2- by oxidase
O2-&raquo_space; H2O2 by superoxidase dismutase
H2O2&raquo_space; HO’ by peroxidase, most dangerous

Question 13

2 reactions

Answer 13

Haber Weiss&raquo_space; O2- + H2O2 > OH- +OH’ +O2
Fenton&raquo_space; fe2 + H2o2&raquo_space; Fe3 +OH ‘ + OH-

Question 14

How to regulate oxidative stress

Answer 14

Scavenger enzymes, no enzyme for hydroxyl
Redox signals by redox sensitive regulators

Question 15

The overall reaction

Answer 15

Oxygen to superoxide by oxidase
Then to hydrogen peroxide by SODs then to water by catalase or hydroxyl radical by peroxidase

Question 16

The genes of regulation in oxidative stress

Answer 16

SoxRS, respond to superoxide in all
OxyR respond to hydrogen peroxide in negative
PerR respond to hydrogen peroxide in positive
Transcriptional activators, upregulates genes concerned with antioxidative defense and repair mechanisms

Question 17

PH and acid tolerance mechanisms

Answer 17

PH homeostasis
Restriction of proton permeation
Consumption of protons
Alteration of cell membrane
Biofilm
Metabolic regulation
Protection and repair of macromolecules

Question 18

What are repair mechanisms in oxidative stress stimulated by redox sensitive regulators

Answer 18

Aa biosynthesis
Cell wall synthesis

Question 19

Ph homeostasis
Restriction of proton entry
Proton consumption

Answer 19

Proton pumps to pump protons out and import potassium and sodium to counterbalance acidification by antiporters

Less permeable membrane and modulated channel size

Consune excess ex urease combines with H+ to produce ammonia to neutralise the pH in heliobacter pylori

Question 20

Proton pump vs antiporter
Low pH vs High pH

Answer 20

Proton pump is unidirectional for protons

Antiporter is bidirectional for a range of ions

Low ph is high conc of protons, high ph is the opposite

Question 21

Altering membrane
Biofilm in pH
Metabolic
macromolecules repair

Answer 21

Change in integrity, fluidity and lipid composition to protect from proton influx

Protect and shield by extracellular matrix and interactions

Glycolysis increase by 70 percent

Chaperons protect misfolding and inhibit death signals

Question 22

Why glycolysis increase with low pH

Answer 22

ATP production and protons consumption
And fixing the NADH/NAD+ ratio
To compensate the damage

Question 23

What do some bacteria do to stabilise proteins and prevent their denature at low ph

Answer 23

Acid shock proteins

Question 24

High temp leads to
Low leads to

Answer 24

Denaturation
Disruption of membrane
DNA damage
Metabolic changes

Reduced metabolism and ice formation

Question 25

Mesophiles...leads to heat shock and ...leads to cold shock and code for..

Answer 25

40 15 Chaperons

Question 26

The signal controlling heat shock response is..HSP known as...help in..under Types according to molecular weight

Answer 26

Unfolded proteins Chaperone Proper folding Heat stress HSP70, HSP90, smallHSP

Question 27

HSR phases, induction

Answer 27

Induction, in stress but not lethal signal activated transcription factor to increase heat shock genes to overproduce heat shock proteins.

Question 28

HSR adaptation

Answer 28

Adaptation, protein structure stabalized and not unfolded, misfolded are not aggregated, refolding of misfolded or denatured, correct folding of new proteins

Question 29

HSR,Steady state

Answer 29

Balance between protein synthesis and degradation, sustained as long as stress us present

Question 30

Response to nutrient limitation

Answer 30

Starvation Stringent

Question 31

Starvation aim

Answer 31

Adapt till nutrients conditions improve

Question 32

Starvation steps 1

Answer 32

Express higher nutrient utilization systems to scavenge nutrients Degrade glycogen stored for energy, release enzymes to degrade complex molecules and gain nutrients from the environment

Question 33

Starvation steps rest

Answer 33

DNA condensation Ribosome degradation Endospore Altering amounts and types of lipid components Energy saving

Question 34

Why degrade ribosomes Who can form endospore energy consuming processes are

Answer 34

To gain nutrients Bacillus and clostridium DNA replication and cell division

Question 35

Bacteria in starvation can increase...in membrane or adjust its...by...to make the membrane more...and maintain...

Answer 35

Unsaturated fatty acids Thickness Changing length of fatty acid chains Fluid Integrity

Question 36

Stringent response

Answer 36

Depletion of amino acids, growth stops them metabolism adjustments to maintain protein synthesis accuracy

Question 37

How stringent response

Answer 37

Low DNA replication Low RNA accumulation esp stable ones r and t Low biosynthesis of carbs, lipids, peptidoglycans Shut down of transport of macromolecule precusors