Chapter 5 Flashcards
Photosynthesis
Autotroph
Organism that produces organic molecules by acquiring carbon from inorganic substances such as water and carbon dioxide (primary producer)
-carry out photosynthesis
Heterotrophs
Organism that obtains carbon and energy by eating other organisms (consumer)
Explain oxidation of H20
During light reactions, electrons are removed from water, oxidizing it. NADP+ gains electrons (it’s reduced) forming NADPH
Explain reduction of CO2
During carbon reactions, electrons move from NADPH to CO2. NADPH is oxidized and CO2 is reduced, forming carbohydrates
Define photosynthesis
The process of converting light energy (kinetic) into chemical energy (stored)
-harness sunlight energy to manufacture organic molecules
What kind of cells carry out photosynthesis?
-Cyanobacteria carry out photosynthesis mainly in water
-Eukaryotes such as algae and plants carry out photosynthesis in water and on land
-no archaea are known to carry out photosynthesis at all
Where does photosynthesis occur in domain bacteria?
Cyanobacteria, in the cytoplasm
Where does photosynthesis occur in domain eukarya?
Plants and algae, in the chloroplasts
What is the equation for photosynthesis?
Carbon dioxide, water, and sunlight into glucose and oxygen
6CO2 + 6H2O + light energy»_space; C6H12O6 + 6O2
How much of sunlight goes through photosynthesis?
About 1% of sunlight goes through, the rest gets reflected
How much energy does the sun convert each minute?
The sun converts more than 100,000 kg of matter to energy
List the different lights in order of shortest to longest wavelength
-gamma rays (high energy)
-X-rays
-ultra violet radiation
-visible light
-infrared radiation
-microwaves
-radio waves (low energy)
List different wavelengths in nanometers and their colors
-400 (violet)
-445 (blue)
-475 (cyan)
-510 (green)
-570 (yellow)
-590 (orange)
-650 (red)
Electromagnetic spectrum
A range of naturally occurring radiation
Wavelength
The distance a photon moves during a complete vibration
What are the 3 rays of sunlight that reach earth’s surface?
Ultraviolet radiation, visible light, and infrared radiation
Ultra violet radiation
Shortest of the 3 wavelengths that hit earth
-its high energy damages DNA
-causes sunburn and skin cancer
Visible light
Medium wavelength of the 3 that hit earth
-provides energy that powers photosynthesis
-we perceive this light as colors
Infrared radiation
Longest of the 3 wavelengths that hit earth
-too little energy per photon to eb useful to organisms
-most of its energy in converted to heat
Chlorophyll a
A blue-green pigment that plants, algae, and cyanobacteria use to harness the energy in sunlight
Stoma
Plural- Stomata
-pores in plants epidermis through which gases are exchanged with the atmosphere
Mesophyll
Photosynthetic tissue in a leaf’s interior
Thylakoid space
Inner compartment of the thylakoid
Photosystem
Cluster of pigment molecules and proteins in a chloroplast’s thylakoid membrane
-antenna pigments and a reaction center
Reaction center
A molecule of chlorophyll a (and associated proteins) that participate in the life reactions of photosynthesis
How many chloroplasts in the average photosynthetic cell?
40-200 chloroplasts per cell
-adds up to about 500,000 per square mm of leaf
Stroma
Fluid inner region of a chloroplast
Thylakoid
Pancake shaped structure that make up the inner membrane of a chloroplast (it’s studded with photosynthetic pigments)
Photons
Discrete packets of light (kinetic) energy or other electromagnetic radiation
-plants and other photo-synthesizers capture photons of visible light
What are pigments
Molecules that capture energy from light
-pigments found in plants specialize in absorbing energy from different wavelengths of light
3 different kinds of pigments
-chlorophyll a
-chlorophyll b
-carotenoids
Which of the 3 pigments are main and which are accessory?
Chlorophyll a is the main pigment and chlorophyll b and carotenoids are accessory pigments
Main pigment Chlorophyll a
-blue-green color
-plants, algae, and cyanobacteria
Accessory pigment chlorophyll b
-yellow-green color
-plants and green algae
Accessory pigment carotenoids
-(like carotenes and xanthophylls)
-red, orange, and yellow
-plants, algae, and bacteria
What light isn’t absorbed by plants and why?
Green light because it is reflected, this is why we perceive leaves as green
Antenna pigments
Photosynthetic pigments that passes photon energy to the reaction center of a photosystem
Thylakoid membrane
Lipid bilayer in which photosystems are embedded
Granum
A stack of flattened thylakoid discs in a chloroplast
ATP
A nucleotide that stores potential energy in the covalent bonds between its phosphate groups
NADPH
A coenzyme that carries electrons in photosynthesis
Chemiosmotic phosphorylation
Reactions that produce ATP using ATP synthase and the potential energy of a proton gradient
Photosystem II
Group of pigments and proteins that uses light energy to energize electrons stripped from water
What are the 2 stages of photosynthesis?
-light reactions
-carbon reactions (aka Calvin Cycle)
Light reactions in photosynthesis
Light energy is captured and converted to chemical energy
-occur in thylakoids and require water and light
-ATP and NADPH are produced, to carry stored energy
-oxygen is formed as a byproduct
Carbon reaction in photosynthesis
Energy is used to produce sugar
-use ATP and NADPH to synthesize carbohydrates from CO2
Photosystem I
Group of pigments and proteins that uses light energy to energize electrons received by photosystem II
Electron transport chain
Series of membrane proteins that shuttle electrons and use the released energy to create a proton gradient across a membrane
ATP synthase
Enzyme that uses the potential energy in a proton gradient to produce ATP
Light reactions- pigments transfer energy to electrons
-light strikes first photosystem (PSII)
-chlorophyll absorbs the light energy and transfers it to electrons, which come from water molecules
-electrons move to an electron transport chain
Light reactions- PSII produces ATP
-electrons from PSII move down to an electron transport chain
-H+ is pumped into the thylakoid
-H+ leaves through ATP synthase
-ATP is produced by ATP synthase, through chemiosmotic phosphorylation
Light reactions- PSI produces NADPH
-electrons arrive at the second photosystem (PSI)
-when light hits PSI, chlorophyll transfers light energy to electrons
-electrons move to a second electron transport chain
-electrons reduce to NADPH
-chlorophyll A reaction center
Light reactions- ATP and NADPH power the carbon reactions
-ATP and NADPH produced during light reactions carry the stored energy derived from sunlight
-in the carbon reactions, this energy is used to break up molecules of CO2 and build molecules of sugar from it
Some weed killers block light reactions how?
Some chemicals, such as weed killers DCMU (Diuron) and Paraquat, block the light reactions by interfering with the flow of electrons
Rubisco
Enzyme that adds CO2 to RuBP in the carbon reactions of photosynthesis
-catalyzes the first reaction of the carbon cycle
PGA
Phosphoglycerate, which is two 3-carbon molecules
How many times does the Calvin Cycle have to turn to produce 1 molecule of glucose?
It has to go through 6 times to produce 1 molecule of glucose
4 basic steps of the Calvin cycle
1.) carbon fixation- carbon dioxide is added to RuBP (a 5-carbon molecule), which creates an unstable 6-carbon molecule
2.) PGAL synthesis- the unstable intermediate splits to form PGAL
3.)PGAL molecules are combined to form glucose, which is used to form starch, sucrose, and other organic molecules
4.) regeneration of RuBP- RuBP is regenerated by rearranging the remaining molecules
Carbon fixation definition
The incorporation of carbon from CO2 into an organic compound
-aka Calvin cycle, C3 pathway
Carbon reactions- carbon fixation
-rubisco enzyme adds onto a molecule of RuBP
-an unstable 6-carbon organic molecule is produced
Carbon reactions- produce PGAL
-ATP and NADPH from light reactions are cashed in
-their energy is used when PGA is converted to PGAL
Carbon reactions- produce glucose
-one PGAL leaves the cycle
-multiple PGALs combine to form molecules of glucose
-some of the PGAL goes back into the cycle to reform the RuBP again
RuBP
Ribulose Biphosphate- the 5-carbon molecule that reacts with CO2 in the Calvin cycle
Photorespiration
Metabolic pathway in which rubisco reacts with O2 instead of CO2, counteracting photosynthesis
-conditions are extreme, hot and dry, stomata are closed to conserve water
-limits sugar production
C4 pathway
Carbon fixation pathway in which CO2 combines with a 3-carbon molecule to form a 4-carbon compound (fixes carbon twice)
Bundle sheath cell
Thick walled plant cell surrounding veins
-site of Calvin cycle in C4 plants
CAM pathway
Crassulacean Acid Metabolism- carbon fixation that occurs at night
-CO2 is later released for use in the Calvin cycle during the day (fixes carbon twice)
C3 plants do well in what conditions?
-cool, moist weather
-95% of all plants
-ex. sycamore tree
C4 plants do well in what conditions?
-hot, dry weather
-about 1% of all plants
-ex. corn
CAM plants do well in what conditions?
-hot, dry weather
-about 3-4% of all plants
-ex. cactus and pineapple
How do C3 plants do the Calvin cycle?
-they do it all at once
-it all takes place in the mesophyll cells
-in hot, dry weather, the stomata will close to conserve water
-photorespiration occurs due to oxygen build up inside the leaf, decreasing photosynthesis
How do C4 plants do the Calvin cycle?
-they divide the labor between cells
-the carbon reactions catalyzed by rubisco occurs in the bundle sheath cells away from the air
-photorespiration doesn’t reduce the efficiency of photosynthesis
How do CAM plants to the Calvin Cycle?
-they divide the labor temporarily
-all reactions for photosynthesis occur in mesophyll cells
-carbon reactions only occur at night in cooler, moister air
-photorespiration doesn’t reduce the efficiency of photosynthesis
Salamander embryos are solar powered and benefit twice
-salamander produces embryos that are surrounded by a jelly layer
-algae lives in jelly layer, where they carry out photosynthesis
-this benefits both organisms
-embryos with a jelly coat receive oxygen from the algae
-researchers used radioactive labels to show embryos also receive more sugars from the algae when grown in the light rather than the dark
