Chapter 10 Flashcards
photosynthesis
the process that converts solar energy into chemical energy
autotrophs
sustain themselves without eating anything derived from other organisms
Autotrophs are the _____ of the biosphere, producing organic molecules from CO2 and other inorganic molecules
PRODUCERS
true or false
Almost all plants are photoautotrophs, using the energy of sunlight to make organic molecules
TRUE
in what does photosynthesis happen in?
plants, algae, certain protists, and some prokaryotes
*these organisms feed not only themselves but also most of the living world
heterotrophs
-obtain their organic material from other organisms
• Heterotrophs are the consumers of the biosphere
• Almost all heterotrophs, including humans, depend on photoautotrophs for food and O2
fossil fuels come from what?
the remains of organisms that died hundreds of millions of years ago
where does photosynthesis happen? and what did this possibly evolve from?
in the chloroplasts
-possibly evolve from photosynthetic bacteria
chlorophyll
the pigment within chloroplasts that absorbs blue and red but not green so it reflects green
where are chloroplasts usually found?
in cells of the mesophyll, the interior tissue of the leaf (each mesophyll cell contains 30-40 chloroplasts)
where does CO2 enter and O2 exit on the leaf?
through the microscopic pores called stomata
where is chlorophyll found?
in the membranes of thylakoids
a stack of thlyakoids is a what?
grana
stroma
a dense interior fluid inside the chloroplasts
what is the equation for photosynthesis?
6CO2 + 12H2O + LIGHT ENERGY –> C6H1206 + 6O2 + 6H2O
what is the equation for cellular respiration?
C6H1206 + 6O2 –> 6CO2 + 6H2O + ENERGY
What splits up H2O? and what happens from this split?
- chloroplasts split H2O
- uses the electrons of hydrogen to continue with photosynthesis
- releases oxygen as a by product
Photosynthesis is a redox process in which H2O is _____ and CO2 is ______
- oxidized
- reduced
Photosynthesis is an ______ process; the energy boost is provided by light
endergonic process
what are the 2 stages of photosynthesis?
- light reactions
- calvin cycle
what happens in the “light reactions”
- splitting of H2O
- Release of O2
- Reduce NADP+ to NADPH
- Generate ATP from ADP by photophosphorylation
what happens in the calvin cycle?
-forms sugar from CO2, using ATP and NADPH
by using carbon fixation
from where do chloroplasts get their energy?
the sun (light energy)
what do thylakoids do with light energy?
transform light energy into the chemical energy called ATP and NADPH
• Light is a form of electromagnetic energy, also called ______ _____
electromagnetic radiation
light travels in ….
rhythmic waves
Wavelength determines the type of _____ _____
electromagnetic energy
electromagnetic spectrum
the entire range of electromagnetic energy, or radiation
visible lights
wavelengths (including those that drive photosynthesis) that produce colors we can see
photons
discrete particles that light consists of
pigments
substances that absorb visible light
-different pigments absorb different wavelengths
-Wavelengths that are not absorbed are reflected
or transmitted
spectrophotometer
measures a pigment’s ability to absorb various wavelengths
what does it mean if you are testing a liquid for transmittance of the color green and the transmittance percentage is high
Chlorophyll absorbs very little green light.
according to chlorophyll a what color wavelengths work best for photosynthesis
violet blue and red light
what is the main pigment in photosynthesis? what are the other pigments?
- chlorophyll a
- -chlorophyll b
- cartenoids
chlorophyll b
broaden the spectrum used for photosynthesi
carotenoids
absorb excessive light that would damage chlorophyll
what happens when pigments in the chloroplasts absorb light?
it goes from a ground state to an excited state which is unstable
When excited electrons fall back to the ground state, photons are given off, an afterglow called
-flourescence
what does a photosystem consist of?
reaction center complex and light harvesting complexes
what does a reaction center do?
- a type of protein complex
- it contains a special pair of chlorophyll a molecule, the electron that will get excited, and a primary electron acceptor.
- –this is surrounded by light harvesting complexes
what does the light harvesting complexes do?
(pigment molecules bound to proteins) transfer the energy of photons to the reaction center to excite the electron
primary electron acceptor
in the reaction center accepts excited electrons and is reduced as a result
which goes first photosystem 2 or 1?
2
linear electron flow
the primary pathway, involves both photosystems and produces ATP and NADPH using light energy
• A photon hits a pigment and its energy is passed among pigment molecules until it excites reaction center/ chlorophyll a of PS2
• An excited electron from the reaction center/ chlorophyll a of PS2 is transferred to the primary electron acceptor
what is H2O split by? and where do its electrons go?
- split by enzymes
- electrons go from hydrogen atoms to the reaction center/chlorohpyll a ( thus reducing the reaction center/ chlorophyll a)
after the electron jumps up to the electron acceptor in PS 2 where does it go?
it falls down the electron transport chain between PS2 to PS1
As the electron falls from PS2 to PS1 what is produced?
energy is released and bring protons (H+) into the thylakoid space (thylakoid lumen)…this process creates ATP (this stage includes electron transport chain and ATP synthase)
once the electron goes through PS2 and the electron transport chain what happens?
the electron is accepted by PS1 and by using light energy it excites the electron again so the electron jumps up to the electron acceptor of PS1`
once the electron is stationed in the electron acceptor of PS1 what happens?
it “falls” down an electron transport chain from the electron acceptor of PS1 to the protein ferredoxin (Fd)
- the electrons are transferred to NADP+ and thus reduces it to NADPH (to become NADPH it needs the electron and a H+ so while doing this it is also taking H+ from the stroma)
cyclic electron flow
uses only photosystem I and produces ATP, but not NADPH
• No oxygen is released
• Cyclic electron flow generates surplus ATP, satisfying the higher demand in the Calvin cycle
what is an organism that has PS1 but not PS2
purple sulfur bacteria
what might have been evolved first? cyclic or linear electron flow?
CYCLIC
what does cyclic electron flow protect cells from?
light induced damage
in respiration Glucose is ____ and Oxygen is ____
- oxidized
- reduced
cytochrome
the family of proteins that make up the electron transport chain in both mitochondria and chloroplasts
is the calvin cycle in the thylakoid?
no it leaves the thylakoid and happens in the stroma
where does the ETC of photosystem 1 happen?
it happens on the outer side of the thylakoid (the side facing the stroma)
by moving electrons from H20 to NADPH what is this doing?
increasing the potential energy
true or false?
The Calvin cycle, like the citric acid cycle,
regenerates its starting material after molecules enter and leave the cycle
TRUE
___ enters the cycle and leaves as a ____
- Carbon as CO2
- sugar
what are the three phases of the calvin cycle?
– Carbon fixation (catalyzed by rubisco)
– Reduction – Regeneration of the CO2 acceptor (RuBP)
For net synthesis of 1 sugar (G3P), the cycle must take place three times, fixing __ molecules of CO2
3 molecules of CO2
explain the first stage of the calvin cycle (carbon fixation)
- > taking a CO2 molecule and attaching it to a five carbon sugar named ribulose bisphosphate (RuBP)
- -> the enzyme doing the catalyzing in this first step is RUBISCO
- –>the product of the reaction in this first step is a six carbon intermediate so unstable that it immediately splits in half, forming two molecules of 3-phosphogylcerate (for each CO2 molecule)
explain the 2nd stage of the calvin cycle (reduction)
- > each molecule of 3- phosphoglycerate recieves an additional phosphate group(now has 2 phosphate group) from an ATP (thus 1st use of an ATP molecules) and with the phosphate group it becomes 3-bisphosphoglycerate
- ->then a pair of electrons from NADPH are donated to the molecule 3-bisphosphoglycerate to reduce it…in addition this molecule also loses a phosphate group (goes back to having 1 phosphate group) and in the end this molecule now becomes known as G3P THIS IS YOUR SUGAR..YOUR OUTPUT
explain the third stage of the calvin cycle (regeneration of the CO2 accepter rubisco)
- > carbon skeletons of 5 molecules of G3P are rearranged by the last steps of the calvin cycle into 3 molecules of rubisco BUT to accomplish this transformation you need 3 ATP
- -> now you have rubsico ready to work with more CO2 molecules
for a net synthesis of 1 G3P ( a sugar) the calvin cycle must take place three times thus taking 3 molecules of CO2 and putting each individually through the process…
for all three molecules of CO2 was in produced and what is taken in?
PRODUCED
(3) short lived intermediate
(6) 3-phosphogylcerate
(6) 1,3-bisphosphoglycerate
(6) G3P
USED
(9) ATP
(6) NADPH
(3) Rubisco
On hot, dry days, plants ____ stomata, which conserves H2O but also limits photosynthesis
close
The closing of stomata reduces access to ___ and causes __ to build up
CO2
O2
Photorespiration
a wasteful process where rubisco takes O2 Instead (because likes O2 better for some reaosn) of CO2 and makes garbage instead of sugar
what plants do photorespiration if put in the wrong environment (hot and arid) ?
C3 plants
how do C4 plants avoid or minimize photorespiration?
C4 plants have an additional pathway which ensures that Rubisco will only receive CO2 to fix. it’s more costly, but it beats wasting ATP for nothing in photorespiration
-use of the enzyme PEP carboxylase to fix CO2 to rubisco
what makes CAM plants special?
open their stomata at night, and store CO2 overnight in organic acids
• Stomata close during the day, and CO2 is released from organic acids and used in the Calvin cycle
-> the CO2 didnt go through calvin cycle at night because it didnt have ATP and NADPH from the light dependent part of photosynthesis so the plant had to store the CO2
NADP /NADPH is for
-plants
FADH/FADH2 and NAD+/NADH is for
-animal
