final cellular energetics pt 2

Question 1

how does photosynthesis generate chemical energy and reducing power

Answer 1

photosynthesis uses light energy to generate ATP and NADPH to allow CO2 to be “fixed” into organic molecules

Question 2

are catabolic and anabolic pathways reverses or opposites of each other

Answer 2

opposites

Question 3

what is photosynthesis

Answer 3

the synthesis of simple sugars from CO2 and H2O using energy from light

Question 4

what are the two stages that photosynthesis occur in

Answer 4

light and dark reactions (in chloroplasts)

Question 5

what do light reactions do

Answer 5

they harness light energy to generate ATP and NADPH; occurs in thylakoid membrane

Question 6

what do dark reactions do

Answer 6

use ATP and NADPH to “fix” CO2 into organic compounds; occurs in stroma

Question 7

what are the three chloroplast membranes

Answer 7

outer membrane, inner membrane, thylakoid membrane

Question 8

what is the thylakoid membrane organized into

Answer 8

stacks called granum

Question 9

what is the difference between light and dark reactions

Answer 9

light reactions are dependent on light, whereas dark reactions aren’t

Question 10

what is the difference between NADPH and NADH

Answer 10

they’re energetically similar but NADPH is used for anabolic reactions and NADH is used for catabolic reactions

Question 11

what are futile cycles and why don’t we want them

Answer 11

cells do an anabolic reaction, then a catabolic reaction on same set of molecules where then you just are building up and burning down, wasting energy - this happens if anabolic and catabolic cycles aren’t separated

Question 12

how do light reactions work with dark reactions

Answer 12

take ATP and NADPH that were generated in light reactions and use them to fix CO2 from atmosphere to make 3-carbon sugars

Question 13

what are photosystems

Answer 13

light is harvested by these two multi-protein complexes

Question 14

what are the two photosystem reactions

Answer 14

electrons are transferred from ETC that pumps protons, which delivers electrons to NADP to make NADPH

Question 15

what do proton pumps do in light reactions

Answer 15

they make proton gradients which are used in a pathway to generate ATP

Question 16

what is used in the carbon-fixation cycle

Answer 16

ATP and NADPH are used when CO2 is reduced to generate carbohydrate molecules

Question 17

what is the order of the photosystems

Answer 17

photosystem 2 is first, photosystem 1 is second

Question 18

how do the two photosystems work

Answer 18

• photosystem II uses light energy to “split” 2 water molecules into 4 H+ and O2 and excite 4 electrons
• excited electrons from photosystem II pass through an electron transport chain to generate a proton gradient (just like in mitochondria), but the protons are pumped into the thylakoid space
• the proton gradient is used to generate ATP, required in the dark reactions

Question 19

what is the final electron acceptor of light reactions

Answer 19

Photosystem I, which excites the electrons and passes them to NADP+ to generate NADPH, also required in dark reactions

Question 20

what are some similarities between mitochondrial respiration and photosynthesis

Answer 20

both use electron transport chains to generate proton gradients, which generate ATP by chemiosmosis

Question 21

what are some differences between mitochondrial respiration and photosynthesis (where electrons come from)

Answer 21

• in photosynthesis, they come from water

- in mitochondrial respiration, they come from catabolic reactions like glycolysis and krebs cycle

Question 22

what are some differences between mitochondrial respiration and photosynthesis (final electron acceptor)

Answer 22

• final electron acceptor for the etc in mitochondria in O2 to generate water
• for proton pumping etc in chloroplast in photosystem I itself

Question 23

what are some differences between mitochondrial respiration and photosynthesis (form of NAD)

Answer 23

mitochondrial respiration uses NADH, photosynthesis uses NADPH

Question 24

what are some differences between mitochondrial respiration and photosynthesis (amount of proton pumping machines)

Answer 24

in mitochondrial ETC, 3

in photosynthesis, 1

Question 25

what are some differences between mitochondrial respiration and photosynthesis (where energy comes from)

Answer 25

• energy for ATP generation and for reducing NADP to NADPH and generating proton gradient in photosynthesis comes from light
• in mitochondrial metabolism and glycolysis, the energy to reduce NAD and to generate ATP comes form oxidation of organic molecules

Question 26

when do dark reactions occur

Answer 26

in the calvin cycle - starts with the addition of 3 CO2 to 3 molecules of ribulose 1,5-biphosphate

Question 27

what happens in the calvin cycle

Answer 27

• take CO2 and attach it to 5-carbon molecule to generate 6-carbon intermediate
• catalyzed by RuBisCO, the most abundant protein on earth
• intermediate reacts to form 2 molecules of 3-phophoglycerate

Question 28

what does the calvin cycle begin and end with

Answer 28

• calvin cycle makes glyceraldehyde 3-phosphate?

- ends and starts with some molecule