Ch. 7 Photosynthesis: Using Light to Make Food Flashcards
Photosynthesis
Putting together glucose with light.
- light energy —> chemical energy (Energy Transaction)
What is the equation for photosynthesis?
6CO2 + 6H2O — Light Energy —> C6H12O6 + 6O2
Autotrophs
An organism that makes its own food
- 2 methods: photosynthesis, and chemiosmosis
Producers
An organism that makes organic food molecules from CO2, H2O, and other inorganic raw materials
Where does photosynthesis occur?
All green parts of the plant. Leaves particularly. It is particularly the membranes of chloroplast.
Mesophyll
The green tissue in the interior of a leaf
- numerous chloroplast
- main site of photosynthesis
Stomata
A pore surrounded by guard cells in the epidermis of a lead
- CO2 enters, water and O2 exit
Stroma
Thick fluid where sugars are made by enzymes of the Calvin Cycle
Thylakoids
Disc shaped membranous sacs inside a chloroplast that contains chlorophyll and the enzymes of the light reactions of photosynthesis
Grana
A stack of hollow discs formed of thylakoid membrane in the chloroplast
- site where light energy is trapped by chlorophyll and converted to chemical energy during light reactions of photosynthesis
What is reduced and oxidized in photosynthesis?
CO2 is reduced. H2O is oxidized.
Light Reactions
The first of two stages in photosynthesis. Steps in which solar energy is absorbed and converted to chemical energy in the form of ATP and NADPH.
- powers the sugar producing Calvin Cycle
Calvin Cycle
The second of two stages of photosynthesis. A cyclic series of chemical reactions that occur in the stroma of a chloroplast using the carbon in CO2 and the ATP/NADPH produced in light reactions to make energy rich sugar molecule G3P
Carbon Fixation
Carbon from the air combines with RuBP to make 3 C6 which is unstable and turns into PGA
Electromagnetic Energy
Solar energy or radiation which travels in space as rhythmic waves and can be measured in photons
Wavelength
The distance between crests of adjacent waves
What wavelengths do carotenoids absorb?
Yellow-orange pigments
What color is least effective in driving photosynthesis?
Green
Photon
Fixed quantity of light energy
- shorter the wavelength, greater the energy
Reaction Center
In a photosystem in chloroplast, the chlorophyll “a” molecule and the primary electron acceptor that trigger the light reactions of photosynthesis
- absorbed energized light energy (electrons)
Photosystem
Light harvesting unit of a chloroplast’s thylakoid membrane
- consists of several hundred antenna molecules, a reaction center chlorophyll, and a primary electron acceptor
What are the three key events of light reactions?
1) Absorption of light energy
2) Excitation of electrons by that energy
3) Formation of ATP and NADPH using energy made available by electrons
Photophosphorylation
The production of ATP by chemiosmosis during the light reactions of photosynthesis
What are the 2 stages of photosynthesis?
1) Light Reactions
2) Calvin Cycle
What 3 things do all cells use?
1) Electron Transport
2) Redox reactions
3) Chemiosmosis
C3 Plants
Plants where Calvin Cycle uses CO2 directly from the air
- common, widely distributed
- stomata closes in dry air
Photorespiration
In a plant cell, the breakdown of a 2C produced by Calvin Cycle instead of G3P w/ 3C when leaf cell fixes O2 instead of CO2
C4 Plants
Plants have special water adaptations and prevent photorespiration
CAM Plants
Plants adapted to very dry climates
- conserves CO2 by opening stomata at night
Old Growth Forest
An ancient forest that has never been seriously disturbed by humans
- trees dominating may be thousands of years old
Greenhouse Effect
Warming of the atmosphere caused by CO2, CH4, and other gases which absorb infared radiation and slow its escape from Earth’s surface
Why is photosynthesis crucial to life?
It produces most of the oxygen in the atmosphere. Makes glucose for cell respiration (energy) and to build more complex molecules.
What do plants, some protists, and some bacteria all have in common?
All have chlorophyll that enables photosynthesis. [chloroplast is only an organelle by chlorophyll is what does the work specifically]
What are the parts of a leaf?
Cuticle, Upper epidermis, Palisade layer, Spongy layer, vein stomate (pore/guard cells), lower epidermis
Electromagnetic Spectrum
Full range of electromagnetic wavelength
- nanometers
What comprises the electromagnetic spectrum?
Gamma rays, x-rays, UV rays, visible light, infared, microwaves, radio waves
What are three things that can happen when an electron is excited?
Light. Heat. Down electron transport chain.
What are the three components of a photosystem?
1) 200 - 300 pigment molecules of chlorophyll (antenna)
2) Reaction center molecule
3) Primary Electron Acceptor
What is noncyclic photophosphorylation?
Adding phosphate to ATP using light
Photosystem I
Chlorophyll molecule with reaction center P700 where light is absorbed most strongly and electrons sent to NADP to make NADPH
Photosystem II
Identical to photosystem I but with P680 and electrons go to P700
What are the 3 events of light reactions?
1) Absorption of light by chlorophyll
2) Excitation of electrons caused by light
3) Splitting of water into hydrogen and oxygen (released to atmosphere) [Produces ATP/NADPH]
What are the five steps of light reactions?
1) Antenna pigments of photosystem I chlorophyll absorb light energy
2) Energized electrons sent to reaction center P700
3) Reaction center sends energized electrons to primary electron center
4) Primary electron acceptor is oxidized as it loses electrons (redox reactions)
5) Electrons arrive at NADP to make NADPH
What is the function of Photosystem II?
To split water into O2 and 4H+ to send electrons to P680 so electrons sent to an acceptor then to P700 to fill a void
What are the four steps of calvin cycle?
1) Carbon fixation
2) Energy consumption redox
3) Release of 1 molecule of G3P
4) Regeneration of RuBP
What are three key substances of calvin cycle?
PGA –> G3P –> RuBP
What do plants use sugar made in cell respiration for?
Make energy and building material. Excess is stored as starch.
Why is photosynthesis the ultimate source of food?
Produces oxygen, building material, and energy/fuel.
