Chapter 10 Flashcards
what is an autotroph?
organism that produces organic molecules using CO2 as carbon source
why do autotrophs produce their own food?
to sustain themselves without eating other organisms
what are photoautotrophs?
organisms that use photosynthesis as a process to produce their own food
ex: plants, algae, cyanobacteria
what does CO₂ contribute to photosynthesis?
carbon molecules for the glucose
is photosynthesis endergonic or exergonic
endergonic
is photosynthesis catabolic or anabolic?
anabolic
what is being reduced in photosynthesis?
CO₂ is reduced into glucose
what is being oxidized in photosynthesis?
H₂O is being oxidized into O₂
what two metabolic stages occurs in photosynthesis?
- light harvesting rxns
- calvin cycle
which plant cells perform photosynthesis?
palisade and spongy cells
what occurs in the chloroplast’s thylakoid membrane?
the photosynthetic ETC/ light harvesting reactions
what occurs in the chloroplast’s stroma?
the Calvin-light-independent cycle
what are photosystems?
protein-pigment complexes that absorb light/photons in order to drive the transfer of electrons
describe the flow of electrons in the photosystems
H₂O → NADP+ → NADPH
how much of the sugars made by photosynthesis are consumed as fuel for cellular respiration in plant cells?
about half of the sugars, rest are used for structure, energy storage, other organic compounds
why do plants need mitochondria for ATP production if ATP is already made in the light-harvesting reactions?
plants still need to undergo cellular respiration at night (no light, cannot produce ATP via light-harvesting rxns)
what are the products in the light-harvesting reactions?
O₂ , ATP, NADPH
Summarize what occurs in the light-harvesting reactions
light/photons are absorbed by electrons from water, transferred through photosystems, reducing NADP+ to NADPH
ATP synthesized by ETC
Summarize what occurs in the Calvin Cycle
ATP and NADPH from light-harvesting rxns convert CO₂ into sugars
what happens to excess carbs produced from photosynthesis?
converted to starch and stored temporarily in chloroplasts
what is light?
type of electromagnetic energy with wave-like properties
what is wavelength?
distance between crests of waves?
what is frequency?
of waves in a certain distance?
Describe the relationship between amount of energy and wavelength of the light
The amount of energy is INVERSELY related to the wavelength of light
(e.g. longer wavelength → lower energy)
(shorter wavelength → higher energy)
what absorbs light that drives the light-harvesting reactions?
photosynthetic pigments (pigments that absorb light/take part in photosynthesis)
what are pigments?
molecules that absorb wavelengths of visible light
why do pigments look coloured?
pigments reflect/transmit light they DO NOT absorb
why do leaves appear green?
leaves have chlorophyll, a pigment that reflects green light because it does not absorb it
what is the absorption spectrum?
a graph plotting a pigment’s light absorption vs. wavelength
what wavelengths of light does chlorophyll best absorb?
red and violet-blue
what can carotenoids do that chlorophyll can’t?
- absorb wavelengths of light that chlorophyll poorly absorbs
- protect chlorophyll from damaging high-energy photons
how is chlorophyll amphipathic?
chlorophyll has a polar head and nonpolar tail
what is the purpose of chlorophyll’s porphyrin ring head?
absorbs light
what is the purpose of chlorophyll’s hydrocarbon tail?
allows chlorophyll pigment to be anchored in the lipid membrane
what happens when chlorophyll absorbs light?
one of its electrons becomes excited, goes from ground state to a higher energy excited state
why is heat released when an excited electron returns to its ground state?
Because of the 2nd law of thermodynamics - all energy transformations increase entropy of the universe
what is fluoresence?
the light/visible radiation emitted by a substance after its electrons are excited, which release the light energy it absorbs as heat and fluorescent light
why does chlorophyll emit a different coloured light when it is excited?
The amount of energy it emits is less than what it initially received because of the 2nd law of thermodynamics, some of the energy dissipates in the form of heat
where does electrons in a chlorophyll molecule of a plant cell come from?
from H₂O, H₂O is oxidized into O₂, providing electron for chlorophyll
what happens to the electrons in a chlorophyll molecule of a plant cell when it absorbs light?
the electron becomes excited and transfers its energy to another electron in an adjacent chlorophyll molecule, which transfers energy to another electron in another chlorophyll molecule until it reaches a reaction centre
what are antenna chlorophylls?
chlorophyll molecules that absorb and transfer energy from light
what is a reaction centre?
a specially configured pair of chlorophyll molecules that can transfer the high-energy electron to an electron acceptor
what happens in the electron transfer phase (reaction centre transfers electron to an electron acceptor) in terms of redox reactions?
reaction centre loses electrons, becomes oxidized
electron acceptor gains electrons, becomes reduced
what must occur in order for the photosystem II to continue capturing light energy after an electron acceptor moves on the the photosynthetic ETC?
another electron must be delivered to the reaction centre to replace the electron that was lost and moved to electron acceptor
which molecule is the electron donor in photosynthesis?
H₂O, donates electrons and becomes oxidized into O₂, reducing reaction centre
why are two photosystems necessary?
provides enough energy to pull electrons from water and then use them to reduce NADP+ to form NADPH
what is photosystem II?
supplies electrons to the beginning of the ETC, when photosystem II loses an electron, photosystem I can pull another electron from water
what is photosystem I?
energizes electrons with a second input of light energy, so they have enough energy to reduce NADP+ to form NADPH
where do protons accumulate in the chloroplast?
in the thylakoid lumen (inside thylakoids)
what increases the H+ conc. in the thylakoid lumen?
the oxidation of H₂O occurs in the thylakoid lumen, which produces O₂ and H+
what complex works as a H+ pump to move H+ from stroma to the lumen?
cytochrome b6f
how do protons flow back into the stroma? what does this do regarding ATP?
protons flow back into stroma through ATP synthase, driving ATP synthesis
what is photophosphorylation?
production of ATP using light/photons in order to provide enough energy to phosphorylate ADP
describe the Z scheme
- electron pulled from water into PS II (LOWEST ENERGY)
- electron excited by absorbing light, travels through chlorophyll (HIGHER ENERGY)
- electron transfers through ETC (LOWER ENERGY)
- PS I energizes electrons using 2nd input of light (HIGHEST ENERGY)
- electron energy level used to reduce NADP+ to NADPH (HIGH ENERGY but LOWER than #4)
what is the final electron acceptor in the light-harvesting reactions?
NADP+
how is the energy from electrons used to do work in the light-harvesting reactions?
the formation of a proton gradient provides energy for photophosphorylation
what are the reactants in the calvin cycle?
CO₂, ATP, and NADPH
what is the product in the calvin cycle?
G3P ( triose phosphate ) which can be used by the cell to make glucose and other carbs
can the calvin cycle occur in the dark?
yesssss
what are the 3 stages of the calvin cycle?
- Carboxylation
- Reduction
- Regeneration
describe carboxylation in the calvin cycle
3x CO₂ is added to 3x 5-carbon RuBP, catalyzed by enzyme rubisco. the 3x 6-carbon molecules are immediately broken down into 6x 3-carbon 3-PGA
describe reduction in the calvin cycle
the 6x 3-PGA are phosphorylated by ATP
the 3-PGA are reduced when NADPH transfers 2 electrons and 1 H+, forming 6 G3P and releasing Pi
describe regeneration in the calvin cycle
12-step process, 5 G3P molecules are reorganized and combined to regenerate 3 RuBP, using up ATP
for ever 6 G3P, how many can be withdrawn from the calvin cycle?
only one, 5 G3P are needed to regenerate RuBP
