L8 : Energy and Metabolism in the Extremes

Question 1

What is life?

Answer 1

Life is self-sustaining chemical system capable of Darwinian evolution

Question 2

What are the components of Darwinian evolution?

Answer 2

• Variation
• Differential survival
• Heritability

Question 3

What is metabolism?

Answer 3

Exploitation of free energy

Sum of all chemical reactions in the cell that convert energy

Question 4

What are the 2 environmental requirements for life?

Answer 4

1. Building blocks of the right type
2. Energy source and system to use it

Question 5

What elements are essential for bacterial growth?

Answer 5

• Source of energy
• Source of carbon
• Source of electrons
• Nutrients
• Water

Question 6

What is heterotrophy and autotrophy?

Answer 6

Obtain carbon for organic compounds (eg. sugars)

Obtain carbon from inorganic compounds (eg CO2)
- plants = photo
- oxidation = chemo

Question 7

What is catabolism and anabolism?

Answer 7

Catabolism = provides energy
- Fermentation/respiration

Anabolism = uses energy
- Production of biomass

Question 8

What are diazotrophs?

Answer 8

N2 fixers essential to providing biologically available N to the biosphere

Question 9

What trace elements are required for bacterial growth?

Answer 9

Cu, Mn, Co, Zn in uM or nM amounts

Some require specific growth factors (vitamins, AAs)

Question 10

What is the significance of lanthanide group in organisms?

Answer 10

Recently discovered group of organisms rely on lanthanide group for growth

Question 11

What are the domains of life?

Answer 11

• Bacteria
• Archaea
• Eukaryotes

Question 12

How are bacteria and archaea characterized?

Answer 12

Morphologically simple, genetically and metabolically diverse

Question 13

How are eukaryotes characterized?

Answer 13

Comparatively extremely diverse but limited in certain aspects

Question 14

What is the basic energy profile of a chemical reaction?

Answer 14

Reactants to products
Transition state (high energy intermediate)
Requires activation energy to overcome kinetic barrier

Question 15

What is Gibbs free energy?

Answer 15

/\G = /\H - T/\S

/\G = -ve
- Spontaneous, reaction releases energy

Question 16

What is enthalpy in chemical reactions?

Answer 16

Reflects energy stored in bonds

More energy released when product has stronger bonds than reactant

Question 17

What is entropy in chemical reactions?

Answer 17

Measure of disorder in system

More energy released when product is more random (less organized)

Question 18

What does /\Go describe?

Answer 18

Change in energy of reactants and products under standard conditions

Question 19

What are standard conditions typically defined as?

Answer 19

298K
1atm
1M concentration of reactants + products
pH = 7.0

Question 20

What does the Arrhenius equation relate to?

Answer 20

Most reactions being more complicated

Question 21

What is the difference between transition state and intermediates?

Answer 21

Transition state is the peak energy state during a reaction
Intermediates are species formed before reaching products

Question 22

What is the equation for rate at equilibrium?

Answer 22

Keq = e ^ ( -/\Go / RT )

Question 23

What does K represent in chemical reactions?

Answer 23

Rate of reaction

Question 24

How does an enzyme affect the transition state?

Answer 24

Enzyme lowers activation energy (energy of transition state), increasing rate k

Question 25

What does a 5 kJ/mol change in deltaGo equate to?

Answer 25

Roughly a 10-fold change in Keq

Question 26

What is the Nernst equation?

Answer 26

/\Go = -nFEo

Question 27

What factors are needed for the Nernst equation?

Answer 27

- Electrons transferred (n) - Reduction potential of reaction (Eo)

Question 28

Define electronegativity.

Answer 28

Electron density is biased Atoms of more electronegative elements draw electron density away from less electronegative ones Highest is F

Question 29

What must the sum of oxidation numbers equal?

Answer 29

The charge of the compound/ion

Question 30

What is the oxidation state of atoms in elemental form?

Answer 30

Zero

Question 31

General rules for species rich in H?

Answer 31

Relatively reduced Act as electron donors (reducing agents) Oxidised in redox reactions

Question 32

General rules for species rich in O?

Answer 32

Relatively oxidised Act as electron acceptors (oxidising agents) Reduced in redox reactions

Question 33

What is reduction potential?

Answer 33

Measure of tendency of a chemical species to acquire electrons and be reduced

Question 34

What reference is used in electrochemistry?

Answer 34

Standard hydrogen electrode (SHE)

Question 35

What is the reaction and reduction potential of SHE?

Answer 35

2H+ + 2e- -> H2 Eo(red) = 0.0V

Question 36

How to calculate Eo of reaction?

Answer 36

Eo (reduction) + Eo (oxidation)