powering the cell part 2

Question 1

what are the different classifications of organism according to their mode of respiration

Answer 1

1) obligate aerobe = need oxygen = last electron acceptor
2) obligate anaerobe= die in presence of oxygen
3) faculative aerobe= prefers oxygen but can respire anaerobically

Question 2

what affects the ability of a microbe to withstand oxygen

Answer 2

1) ability to breakdown byproducts of oxygen metabolisms
2) presence of protective enzymes agains reactive oxygen species which form toxic byproducts such as hydrogen peroxide

Question 3

how do cells generate ATP in the absence of oxygen

Answer 3

1) fermentation
2) anaerobic respiration

Question 4

outline fermentation

Answer 4

1) in the absence of oxygen glucose is converted into one or more carbon compounds which are released into the surrounding media
2) glycolysis remains the same as it is oxygen independent
3) pyruvates molecules are converted into 2 co2 and 2 ethanol molecules and 2 NADH moleucles are regenerated to NAD

Question 5

outline how fermenation differs from anaerobic metabolic processes

Answer 5

• generates less ATP= only 2 ATP produced
• uses intracellular electron carries whereas anaerobic uses membrane bound electron carriers

Question 6

outline how terminal electron acceptors differ in microbes than animals and plants

Answer 6

= use alternative acceptors
- not all alternative acceptors harness the same amount of energy so o2 is optimal
- sometimes o2 isnt available so microbes would use second best then once that exhausted move onto third and so on

• accepots with higher redox potential deliver more ATP

Question 7

what is the site of photosynthesis in plants and photosynthetic bacteria

Answer 7

thylakoid membranes

Question 8

outline the structure of thalkoids in bacteria

Answer 8

invaginations of the plasma membrane to form a set of internal membranes

Question 9

outline the chloroplast

Answer 9

• bounded by two membranes which dont contain chlorophyll
• contain third membrane, thyalkoid, where photosynthesis occurs
• thyalkoids arranged in stacks of grana
  membranes conatin integral proteins bound to light absorobing pigments
• carbohydrate synthesis occurs in the stroma

Question 10

what are the 4 stages of photosynthesis

Answer 10

1) absorption of light
2) electron transport
3) synthesis of ATP
4) carbon fixation/ calvin cycle

Question 11

outline the absorption of light

Answer 11

1) occurs in photosystems made up of a reaction centre and light harvesting complexes/ antenna complexs
2) LHC capture light and transfer to reaction centre

Question 12

what is the energy of light used for

Answer 12

1) removal of electrons from water forming oxygen
2) transfer of electrons to primary electron acceptor

Question 13

what is chlorophyll A

Answer 13

1) principle pigment in photosynthesis at the reaction centre of photosystems

Question 14

when is the rate of photosynthesis greatest

Answer 14

when wavelengths of light are absorbed by three pigments

Question 15

outline ATP synthesis in plants

Answer 15

1) the proton motive force drives ATP synthase to form ATP
2) the transfer of electrons can be cyclic or non-cyclic

Question 16

outline non-cyclic transport of electrons

Answer 16

1) needs 2 photosystems conatining one reaction centre each
2) PSII extracts electrons from water and transfers to PSI enabling it to keep producing reducing power

Question 17

when is non cyclic photophosphorylation used

Answer 17

when there is a need for both ATP and NADPH production
- if need for ATP outweighs need for NADPH then may carry out cyclic instead = just ATP

Question 18

outline cyclic transport of electrons

Answer 18

• only needs one photosystem
• light excites chlorophyll and 2 electrons are passed through the ETC
• quinone in the ETC accepts and releases 2 protons in the periplasmic space where they move into the cytosol and out the cell generating PMF
• electrons are then transported back to the RC via soluable cytochrome

Question 19

what is quinone

Answer 19

one electron acceptor in the ETC

Question 20

how is co2 converted into carbohydrates in photosynthesis

Answer 20

1) occurs in the calvin cycle
2) co2 fixed into organic molecules in a series of reacyions which occur in the stroma
3) initial reactions are catalysed by RUBSICO

Question 21

what is the final product of the calvin cycle

Answer 21

1) glyceradlderhyde 3 phosphate
- some is generated in the cycle is transported to cytosol to be converted into sucrose