Energy

Question 1

What are the two methods for generating a proton gradient?

Answer 1

• photosynthetic electron transport chain

- oxidative electron transport chain

Question 2

ATPase

Answer 2

• found in the plasma membrane, inner mitochondrial membrane, thylakoid membrane etc.
• the energy from the flow of protons through it allow an inorganic phosphate to be joined to ADP forming ATP

Question 3

Energy Metabolism in Reverse

Answer 3

• ATP can also be spent to generate a proton gradient
• this is sometimes used to power active transport
• or when excess ATP is available

Question 4

Simple / Passive Diffusion

Answer 4

-molecules pass straight through the cells plasma membrane

Question 5

Facilitated Diffusion

Answer 5

• molecules move from a high concentration o a low concentration through a membrane protein
• no energy required

Question 6

Active Transport

Symporter

Answer 6

• secondary active transport

- the symporter protein pumps something else through the membrane with the target molecule in the same direction

Question 7

Active Transport

Anitporter

Answer 7

• primary active transport

- the antiporter pumps something else through the membrane with the target molecule but in the opposite direction

Question 8

What is oxidation?

Answer 8

-movement of electrons from a high potential energy in the electron donor (negative redox potential) to a lower potential energy in the electron donor (positive redox potential)

Question 9

What do cells need energy for?

Answer 9

• cells have a biochemical repatoire to use carbon and nitrogen sources to make the building blocks of the cell
• the building of polymers requires energy

Question 10

First Stage in Releasing Energy in Cells

Answer 10

• to obtain glucose
• cells will always respire glucose first if it is available
• in the absence of glucose they will make glucose first

Question 11

What are electron / hydrogen donors?

Answer 11

substances to be oxidised

Question 12

Electron Transport Phosphorylation

Answer 12

-flow of electrons from donors with a negative redox potential to acceptors with a more positive redox potential is coupled to synthesis of ATP from ADP and Pi

Question 13

Chemotrophy in General

Answer 13

ADP + Pi -> H2O + ATP

in this process, Xred + Aox -> Xox + Ared

Question 14

Chemoorganotrophy

Answer 14

• organic electron donors
• aerobes use oxygen and anaerobes use nitrate, sulphate or organic substances as electron acceptors
• usually use organic substances as carbon source

Question 15

Chemolithotrophs

Answer 15

• inorganic electron donors (i.e. H2, H2S, NH3)
• inorganic electron acceptors (i.e. O2, CO2, nitrate)
• usually use CO2 as carbon source

Question 16

Oxidation

Answer 16

-losing an electron or a hydrogen

Question 17

Reduction

Answer 17

-gaining an electron or a hydrogen

Question 18

Redo Reactions

Answer 18

Donor(red) + Acceptor(ox) -> Donor(ox) + Acceptor(red)

D + A -> D+ + A-

Question 19

Redox Reactions in the Absence of Oxygen

Answer 19

• usually oxygen is used as the electron acceptor in a redox reaction as it has a very positive redox potential
• it is possible to use other molecules as acceptors, but the difference in potential energy will usually be smaller so less energy will be released

Question 20

Reduction of Alternative Electron Acceptors

Answer 20

NO3(-) -> N2 OR N2O
SO4(-2) -> H2S OR S
CO2 -> CH4

Question 21

Nitrogen as an Electron Acceptor

Answer 21

• a lot of N is recycled by bacteria that use nitrogen as an oxidant
• nitrate reduction is essential for denitrification of soil and recycling of nitrogen back to the atmosphere
• nitrate would otherwise wash into and accumulate in rivers or oceans

Question 22

Assimilatory Reductions

Answer 22

look up

Question 23

Dissimilatory Reductions

Answer 23

look up

Question 24

Fermentations

Answer 24

loose sense – industrial production process involving microbial growth
strict sense – energy generation process in which both electron donor and acceptor are organic compounds, energy is generated by substrate level phosphorylation, doesn’t use an electron transport chain and membrane

Question 25

Example of Fermentation

Answer 25

Glycolysis

Question 26

Respiration

Answer 26

-use of electron transport chain, membrane and proton gradient

Question 27

Fermentations - Toxic Products

Answer 27

-microorganisms find it easy to remove the often toxic fermentation products from the cell by for higher organisms this is more of a problem

Question 28

Recycling of NAD+

Answer 28

- metabolically expensive so cant keep synthesise so must keep recycling - in oxidation NAD+ is reduced to form NADH2 - to be used again it has to be oxidised back to NAD+ using oxygen

Question 29

Fermentation and Recycling

Answer 29

- fermentations are essentially recycling schemes | - in fermentation NADH/H2 is oxidised by passing hydrogen and electrons to an organic compound

Question 30

Alternatives to Oxidative Sugar Utilisation

Answer 30

- in the absence of oxygen as a hydrogen acceptor, a fermentation takes place - yeast and some bacteria can ferment glucose to alcohol

Question 31

Ethanolic Fermentation

Answer 31

``` glucose -> 2 pyruvate (2ADP->2ATP and 2NAD->2NADH) 2 pyruvate -> 2 acetaldehyde (releases 2 CO2) 2 acetaldehyde -> 2 ethaol (2NADH2 -> 2NAD) ```

Question 32

Lactic Fermentation

Answer 32

glucose -> 2 pyruvate (2ADP -> 2ATP and 2NAD -> 2NADH2) 2 pyruvate -> lactic acid (2NADH2 -> 2NAD)

Question 33

Products of Lactic Fermentations

Answer 33

- cheese - yogurt - silage - fermented vegetables - fermented milks - fermented meats

Question 34

Multi-Stage Fermentations

Answer 34

-many fermentations are multi stage and produce a mixture of products

Question 35

What do the products of a fermentation depend on?

Answer 35

- the organism - substrate - growth conditions

Question 36

Which organisms use which types of energy generating mechanisms?

Answer 36

-some organisms are restricted to the type of energy generating processes they can use, others have access to many types of mechanism

Question 37

How is ATP produced in photosynthesis?

Answer 37

-flow of electrons from donors with negative redox potential to acceptors with more positive redox potential is coupled to the synthesis of ATP from ADP and Pi

Question 38

Phototrophy

Answer 38

ADP + pi -> H2O + ATP (using light energy)

Question 39

Photolithotrophy

Answer 39

- H2O or H2S as electron donors | - CO2 as a carbon source

Question 40

Photoorganotrophy

Answer 40

-organic substrates as the electron donor and as the carbon source

Question 41

Electron Transport Chain

Answer 41

- split electron donor with energy to release protons | - pump protons with energy from transport chain to increase gradient

Question 42

Chloroplasts vs Photosynthetic Bacteria | Where do protons accumulate?

Answer 42

- in the thylakoid space in chloroplasts | - in the periplasm in photosynthetic bacteria

Question 43

Mitochondria vs Bacteria | Where do protons accumulate?

Answer 43

- protons accumulate in the intermembrane space in mitochondria - protons accumulate in the periplasm in bacteria - i.e. in the equivalent place in mitochondria and bacteria

Question 44

Higher Plants vs Chromatium vs Purple Bacteria | Carbon Fixation

Answer 44

Higher Plant CO2 + 2H2O -> CH2O + 2O (using light) Chromatium CO2 + 2H2S -> CH2O + 2S (using light) Purple Bacteria 2CO2 + H2S + 2H2O -> 2CH2O + H2SO4 (using light)

Question 45

Chemolitotophic Metabolism | Characteristics

Answer 45

- mainly aerobic - convert oxidations to biological fuel - reducing power is derived from oxidation of many inorganic compounds mostly with oxygen as electron acceptors

Question 46

Examples of Chemolithotrophic Bacteria

Answer 46

- iron bacteria - nitrate oxidisers - ammonia oxidisers - sulphur bacteria