Photosynthesis Flashcards
What is photosynthesis?
The process that converts light energy to the chemical energy of sugar (in plants)
Autotrophs (7.1)
- make their own food through photosynthesis
- sustain themselves
- do not usually consume organic molecules derived from other organisms
- MAKE ORGANIC ENERGY FROM INORGANIC ENERGY
Photoautotrophs vs Chemiautotrophs
- Photoautotrophs use the energy of light to produce organic molecules
- Chemiautotrophs use chemicals to produce organic molecules
Heterotrophs
consumers that…
- feed on plants
- feed on animals
or - decompose organic material
CONSUME ORGANIC MOLECULES
photosynthesis equation
Where does photosynthesis in plants take place
in chloroplasts
What are the two metabolic processes in photosynthesis?
- Light reactions
- Calvin cycle
What happens during the light reactions in photosynthesis and where do they take place? (check what chapter)
- light goes in
- water goes in
- oxygen comes out (as waste)
- NADPH and ATP come out for Calvin cycle
- some energy from the sun (light energy) is converted into the chemical energy of ATP and NADPH (closely related to NADH)
Take place in Thylakoids of a chloroplast
What happens during the Calvin Cycle in photosynthesis and where does it take place? (check what chapter)
- ATP goes in
- NADPH goes in
- 3 CO2 goes in
- One 3 carbon sugar comes out
uses…
-the energy from light reactions (chemical energy in the form of ATP and NADPH)
- carbon dioxide
in order to to produce sugar
Takes place in the stroma of a chloroplast
Chlorophyll (7.2)
- an important light-absorbing pigment in chloroplasts
- is responsible for the green color of plants
- plays a central role in converting solar energy (light) to chemical energy
What is the main photosynthetic organ in plants?
Leaves
What is the photosynthetic organelle in plants?
chloroplast
Where in a leaf does most of the photosynthesis take place?
Inside the mesophyll tissue (tissue has many cells PACKED with chloroplast)
What are stoma and what do they do?
Holes/Pores in the leaf that allow for gas exchange
(carbon-dioxide goes in, oxygen comes out)
Water vapor also evaporates out of the stoma during the process of transpiration
Where does the water that the plant needs for photosynthesis come from and how does in enter the leaf?
it comes from roots
water goes up roots through a vein (by process of transpiration) through cells called xylem
xylem
the tissue in the vein that helps the water set from the ground to the plant
phloem
a tissue that transports products of photosynthesis throughout the plant (leaves, roots, etc)
What type of membrane does a chloroplast have? What is inside a chloroplast?
Has a double membrane (because of endosymbiotic theory)
INSIDE:
- Thylakoids (poker chips)
a stack of Thylakoids (poker chips) is called a Granum - The FLUID that is around the “cytoplasm” of the chloroplast is called the stroma
Is Photosynthesis a redox reaction like cellular respiration or not? Why?
It is a redox reaction because:
- CO2 becomes reduced to sugar as electrons with hydrogen ions from water are added to it
AND - Water molecules are oxidized when they lose electrons and hydrogen ions
What is the energy that sunlight contains called? How is it measured? (7.6)
electromagnetic energy
measured in wave lengths AND/OR Photons (a fixed quantity of light energy)
What are wavelengths?
Electromagnetic energy travels in waves…
the wavelength is the distance between the crest (peak/top) of two adjacent waves
The shorter the wavelength, the greater the energy
What is the electromagnetic spectrum? What part/parts of it can we transduce (brain can comprehend)?
The electromagnetic spectrum is the full range of electromagnetic wavelengths
We can only transduce visible light, which is a tiny part of the spectrum, however other organisms can transduce other parts of the spectrum as well
What does it mean when a pigment absorbs light energy? What happens at times when there is no light energy to absorb?
When light energy hits a pigment, some of its electrons get boosted up to a higher energy state (EXCITED STATE).
if you turn the light off, that electron has to fall back down (GROUND STATE), releasing heat, allowing for fluorescence
Embedded into the phospholipid bilayer of a thylakoid are proteins. What are these called? how many are there? What order do they go in?
They are called photosystem II and Photosystem I (there are 2 of them)
They go in order of: Photosystem II, Photosystem 1
What are the green circles representing in this picture of Photosystem II? (the middle ones, and the outside ones)
They represent pigment molecules:
The middle 2 are chlorophyll A molecules called the reaction center
The outside ones are all different types of pigments, called accessory pigments
THEY WILL ALL ABSORB LIGHT
Explain what happens in Photosystem II
- some of the energy from the light that comes in gets absorbed by the accessory pigments, who feed that energy to the two middle chlorophyll A pigments (the reaction center)
- The reaction center pigments’ electrons can boost it up to a higher energy level using light energy
- instead of just falling back down, there is a molecule that steals them
THIS STARTS AN ELECTRON TRANSPORT CHAIN
Explain what happens in photosystem I (and before and after)
- The new, higher energy, electrons go through an electron transport chain, ending up in the Chlorophyll As in photosystem 1 (the reaction center)
- meanwhile, the light energy is hitting the accessory pigments in photosystem 1, who feed the energy to the reaction center allowing them to boost up their new electrons from Photosystem 2
- they again don’t fall back down, and instead get picked up by a molecule to go through a very SHORT chain
After the short chain, they are used to reduce NADP+ to NADPH (and that is how the light reactions make NADPH)
How do the Chlorophyll A molecules in the reaction center of Photosystem II replace the electrons that they lose?
- They split water apart, and THEN they tear the hydrogens apart
- The electrons from the hydrogens replace the ones lost in the reaction center of Photosystem II
- The protons float away, and the oxygen from the water floats away
As the electrons go down the ETC, they lose some energy. What is this energy used for?
- It is used to pump protons from the stroma into the inside of a thylakoid (small restricted space)
- does this through a PUMP
- the H+ concentration is very high inside a thylakoid, and they use facilitated diffusion through an ATP synthase (from inside thylakoid to the stroma)
- As they go through (by CHEMIOSMOSIS), the ATP synthase spins and bonds an ADP and a P to make ATP
How much ATP and NADPH are used in one cycle of the calvin cycle?
9 (total) ATP and 6 NADPH
What is the net gain of G3P from one cycle of the calvin cycle? how many are remaining in the cycle after the output?
1 G3P is net gain
5 remain in cycle after giving 1
PEP carboxylase cycle
Occurs in the mesophyll cells of a C4 plant
a cycle with an enzyme that fixes ONLY carbon dioxide (not oxygen)
the enzyme is called PEP carboxylase
When the stomata close, there is still some carbon dioxide and oxygen in the mesophyll layer. PEP Carboxylase will keep using that carbon dioxide until there is ACTUALLY none left (completely depleted), and luckily, it will ignore the oxygen
The cycle pumps CO2 into the bundle-sheath layer for the calvin cycle, meaning that rubisco can and will only fix carbon dioxide
What is the purpose of the CAM cycle in CAM plants?
It fixes CO2 into an organic acid which is a solid (AT NIGHT)
you can store way more of this solid organic acid (form of carbon dioxide) then you would be able to store the gas by itself
this allows for the CAM plant to keep CO2 concentration HIGH ENOUGH for Calvin cycle during the day until they can “refill” at night
