topic 6 - phototrophic metabolism - general

Question 1

what happens during the redox reaction of photosynthesis

Answer 1

polar covalent bonds in the reactants are broken
non polar covalent bonds in the products are formed

bonding e- between the C and O in CO2 have moved closer to the C atoms
bonding e- between the O and H in H2O have moved farther away from the O atoms

Question 2

what is biomass

Answer 2

all the matter that makes up an organism after all the water has been removed

in plants
- biomass comes from CO2 (autotroph)

Question 3

what are the parts of the chloroplast

Answer 3

triple membrane (outer, inner, and thylakoid)
spaces (stroma - calvin cycle, and thylakoid lumen)

Question 4

what happens on the thylakoid membrane

Answer 4

light absorption be chlorophylls and carotenoids
e- transport
ATP synthesis by ATP synthase

Question 5

what are the 2 parts of the photosynthetic process

Answer 5

light reactions - transform solar energy into chemical energy

calvin cycle - uses chemical energy to fix CO2 into carbs
- dark/light independent reaction

Question 6

what is used and produced in the light reactions

Answer 6

use
- NADP+, ADP, Pi, sunlight, and water

produce
- ATP, NADPH (reduced e- carrier) and O2

Question 7

what is used and produced in the light independent reactions

Answer 7

uses
- CO2, ATP, NADPH

produces
- fixes the CO2 and uses energy to build carbs

Question 8

what is the association between energy and wavelength of light

Answer 8

energy is inversely proportional to wavelength
shorter wave = more energy

visible light = 400-700nm
400 = blue
700 = red

Question 9

what are the three things that can happen when a photon strikes an object

Answer 9

reflected
transmitted - pass through
absorb the photon - absorbed by e- that gain the energy of the photon

Question 10

what are pigments

Answer 10

molecules efficient in absorbing photons

chemical structure allows their e- to readily absorb their energy

Question 11

how do pigments work

Answer 11

wavelength must exactly match teh energy needed to raise and e- to a higher energy level

if the energy doesn’t match exactly, nothing happens to the e-

Question 12

what are the 3 things that can happen when a photon is absorbed by an e- that moves from a low energy level to a higher energy level

Answer 12

1. e- returns to ground state by emitting a less energetic photon (fluorescence) o releasing energy as heat
2. e- returns to ground state as its energy is transferred to an e- in a neighbouring pigment
3. high energy e- is transferred to another molecule (e- acceptor)

Question 13

where are photosynthetic pigments

Answer 13

embedded in thylakoid membrane

Question 14

what is chlorophyll

Answer 14

main pigment in most photoautotrophs

reflect green
absorb red and blue

Question 15

what are carotenoids

Answer 15

act as accessory pigments

reflect yellow, red, and orange
absorb blue and green

Question 16

what is the reason behind leaves changing colour in fall

Answer 16

cessation of chlorophyll production which revelas the colours of other pigments

Question 17

how are pigments organised

Answer 17

organised into complexes with proteins (photosystems - light harvesting complexes)

Question 18

what is inside of a photosystem

Answer 18

hundereds of antenna pigments grouped around a reaction centre (collection of proteins that interact with pigments)

when excited, the antenna pigemnts channel energy (energy moves NOT e-) to the reaction centre

Question 19

what is inductive resonance

Answer 19

energy transfer form one e- to another

Question 20

what is oxygenic photosynthesis

Answer 20

occurs in prokaryotes
all metabolism occurs in the cytosol and on the cell membrane

cyanobacteria have a photosynthetic mechanism very similar to chloroplasts

responsible for oxygenation of earth

Question 21

what is anoxygenic photosynthesis

Answer 21

does not produce O2
only known to occur in prokaryotic cells

Question 22

why does anoxygenic photosynthesis exist

Answer 22

evolved at a time before O2 was present in the atmosphere and organic molecules much less abundant

does NOT oxidise water
likely the first metabolism utilising an ETC

Question 23

how does anoxygenic photosynthesis work

Answer 23

only use cyclic e- flow to generate PMF
does not produce O2

purple and green sulphur bacteria use H2S as a source of e- instead of water
- produces sulphur

cyanobacteria can also go through cycling e- flow

Question 24

what are the inputs and outputs of anoxygenic photosynthesis

Answer 24

input
- light, H2S, ADP, Pi, NADP+

output
- sulphur, ATP, NADPH

Question 25

what is the difference between aerobic cell resp and photosynthesis

Answer 25

photosynthesis = anabolic process (building up carbs)

cell resp = catabolic process (breaking down C based molecules - oxidising and releasign as CO2)

ATP synthase embedded in both
both have ETC that generates PMF