Unit 4: Photosynthesis Flashcards
Compare photosynthesis and cellular respiration
Products of one are reactants of other
PS purpose: capture/store energy
CR purpose: release energy
Define
Autotroph
Organism capable of using inorganic molecules to make organic molecules (sugars)
What organisms are autotrophic?
Plants
Algae, some other protists
Some bacteria
Define
Heterotroph
Organisms that rely on organic molecules made by autotrophs for their source of energy / organic matter
What tissue type contains the most chloroplasts?
Mesophyll
Found in leaves
Define
Stomata
Pores on leaf surface that allow for the exchange of O2 and CO2
Identify the parts of the chloroplast
a - outer membrane
b - stroma (liquid portion)
c - thylakoid
d - granum
e - inner membrane
State
Reaction for Photosynthesis
6 CO2 + 6 H2O → C6H12O6 + 6 O2
What is the purpose of the light dependent reactions?
Capture solar energy and convert it into chemical energy (in ATP and NADPH)
What is the purpose of the light independent reactions?
Save energy from ATP and NADPH (made during LDR) into molecules of glucose
What is the electron carrier in photosynthesis?
NADP+ (oxidized)
NADPH (reduced)
NADP+ + 2 e- + H+ → NADPH
Define
Electromagnetic energy
Energy that travels as waves, which makes up the electromagnetic spectrum
What is visible light?
Electromagnetic energy, which can be detected by the human eye (about 380 to 750 nm; you do not need to memorize these numbers)
Define
Photon
A “unit” of energy
Think of a photon as the energy that a single electron pair can absorb, which then allows it to become excited / move to a higher electron orbital
Define
Pigment
Molecules that absorb certain wavelengths of light
Define
Absorption
Specifically, absorption of light energy
Energy that is used by a molecule to excite electron(s)
What can happen to light when it hits matter?
It can be:
* absorbed (excite electrons)
* reflected (bounce off)
* transmitted (go through)
We don’t discuss transmission but I didn’t want this to be inaccurate
Light Dependent Reactions: Location
On thylakoid membranes
Light Dependent Reactions:
Reactant
Water
Light Dependent Reactions:
Product
O2
Light Dependent Reactions: Energy Transformation
Sunlight → Chemical (in ATP and NADPH)
Light Independent Reactions: Location
Stroma
Light Independent Reactions: Reactant
CO2
Light Independent Reactions: Product
G3P (and ultimately, glucose)
Light Independent Reactions: Energy Transformations
Chemical energy from ATP and NADPH → G3P / glucose
Define
Photosystem
A group of proteins and pigments that absorb light and focus it to a pair of electrons, which can then be passed on
Describe the movement of electrons during the light dependent reactions
- Water
- PSII (where it will stay until excited by a photon of light)
- Electron transport chain (as it moves through, its energy is used to pump H+ into thylakoid lumen)
- PSI (where it will stay until excited by a photon of light)
- Electron transport chain
- NADP+ reductase
- NADPH
How is NADPH made during photosynthesis?
Electrons are passed to NADP+ reductase, which then bind NADP+ to a H+, making NADPH
What is the other name for the light independent reactions?
Calvin Cycle
State
3 “phases” of the light independent reactions
- Fixation
- Reduction
- (RuBP) Regeneration
What happens during LIR: Fixation
Rubisco (enzyme) binds RuBP (five carbon) to CO2 (1 carbon), making a 6-carbon molecule that quickly breaks into two 3-carbon molecules of 3PG
What happens during LIR: Reduction
3PG is reduced by ATP and NADPH into G3P
What happens during LIR: Regeneration
1/6 of G3P molecules made by reduction phase are used for making glucose (2 G3P = 1 glucose)
5/6 of G3P molecules are rearranged back into 3 molecules of RuBP
Enzyme that adds RuBP + CO2
Rubisco
This is the most abundant protein on Earth!
Define
Fixation
Incorporation of an inorganic molecule to an organic one
Namely, carbon fixation involves adding a CO2 onto RuBP, making an organic 6-carbon molecule
What organisms are heterotrophic?
Animals
Decomposers (fungi, most bacteria)
