Photosynthesis- Unit 2 Flashcards
Autotrophs
Make their own food using energy form the environment and inorganic carbon sources such as CO2
Photosynthesis
Plants and other autotrophs capture light energy and use it to build sugars from water and CO2 (metabolic pathway)
Converts light energy to chemical energy
Heterotrophs
Get energy and carbon from molecules that other organisms have already assembled
Biofuels
Increasing demand
Oils, gases, and alcohols made form organic mater that is no fossilized.
Materials currently used for biofuel production consists mainly of food crops, typically expensive, ecologically disruptive, and produced in competition with our food supply
Making biofuels from other plants require additional steps to break down cellulose
Biofuel solution
Researchers work to find cost effective way to break down the cellulose in fast-growing weeds such as switchgrass
Sunlight as an energy source
Visible light drives photosynthesis which begins when photons are absorbed by photosynthetic pigment molecules
Properties of Light
Travels in waves and is organized as photons.
Visible light is a very small part of the spectrum of electromagnetic energy radiating from the sun
We see light of particular wavelengths as different colors
Wavelength- distance between two crests of 2 successive waves of light
Light waves
Shortest waves are the highest energy (blues)
Longest waves are the lowest energy (reds)
Pigments
Molecules that absorb light of a particular wavelength, photons that are not captured by a pigment are reflected as it’s characteristic color
Chlorophyll A
The main photosynthetic pigment in plants
Absorbs violet and red light, so plant appears green
Accessory pigments
Plants, protists, and bacteria share the majority. Protists and bacteria share the exact same
Color everything else
Archaean photosynthetic pigment
Has one singular unique occurrence, retinal which emits the color violet.
Pigment function
Absorbing a photon excites electrons in the pigment and boosts them to a higher energy level
Photosynthetic cells can capture energy emitted from electrons as they return to a lower energy level
When energy is passed to a special pair of chlorophylls the reaction of photosynthesis begins
who discovered the rainbow
Theodor Engelmann identified the colors of light (red and violet) that drive photosynthesis in a photosynthetic alga
His results created an absorption spectrum which is a graph that shows how efficiently different wavelengths of light are absorbed by a substance
Directed light through a prism so that bands of color crossed a water droplet on a microscope slide. The water held strand of photosynthetic Cladophora and oxygen requiring bacteria. The bacteria clustered around algal cells that released most oxygen, reds and violets.
Flow of energy in terms of pigment
Starts when chlorophylls and other photosynthetic pigments absorb the energy of visible light
In plants, some bacteria, and many protists, that energy ultimately drives the synthesis of glucose and other carbohydrates
where does photosynthesis occur
Chloroplasts
Photosynthesis as a reaction
6CO2+6h20=light energy= glucose and oxygen
series of reactions that occur in 2 stages, light-dependent and light-independent
Light dependent reactions
First stage of photosynthesis, occurs at the thylakoid membrane, convert light energy to chemical energy (ATP)
Form ATP and NADPH, which donate their electrons and chemical bond energy
Light independent reactions
Second stage of photosynthesis
Occurs in stroma
Use ATP to assemble sugars from water and CO2
Molecules that form in the first stage power the formation of sugar in the second stage
Synthesis part of photosynthesis
Sugars are assembled with carbon and oxygen atoms from CO2
Light harvesting complexes
Light harvesting complexes in the thylakoid membrane absorb photons and pass the energy to photosystems which release electrons
Photosystems
A cluster of hundreds of chlorophylls, accessory pigments and other molecules that convert light energy to chemical energy in photosynthesis
Photolysis
Process in second stage by which light energy breaks down a molecule
Stage of photosynthesis replaces lost electrons by pulling them from water which then dissociates into H and O
Energy flow in photosynthesis
Energy flow in light-dependent reactions is an example of how organisms use energy harvested from the environment to drive cellular processes
the simpler cyclic pathway evolved first and operates nearly all photosynthesizes
Some organismal populations evolved the additional photosystem II, beginning a sequence of reactions that removes electrons from water molecules, releasing hydrogen ions and oxygen
Calvin-Benson Cycle
The cyclic light-independent reactions of the Calvin-Benson cycle are the synthesis part of photosynthesis.
Carbon fixation synthesizes sugar
Inside the stroma, the enzyme rubisco attaches a carbon from CO2 to RuBP to start the cycle
Carbon fixation
The incorporation of carbon from an inorganic source such as CO2 into an organic molecule
Rubisco
Most common enzyme on earth, plays an important part in the synthesis portion of photosynthesis
Energy for Sugar Synthesis
Photo: ATP and NADPH are produced by the light-dependent reactions using light energy
Synthesis:
Light-independent reactions use energy from ATP and hydrogen and electrons from NADPH to synthesize sugars from CO2
Carbon-Fixing and Alternate Pathways
When environment differs, so do details of light-independent reactions
Three pathways
C3, C4, CAM plants
Alternate: Details of light-independent reactions that vary among organisms are evolutionary adaptions to different environmental conditions
Photorespiration
On dry days plants conserve water by closing their stomata
O2 from photosynthesis can’t escape and CO2 for it can’t enter
Stomata
openings through plant surfaces that allow water vapor and gases to diffuse across the epidermis and through cuticle
Green energy (process of carbon)
Photosynthesis removes carbon dioxide from the atmosphere, and locks it’s carbon atoms inside the organic compounds
When aerobic organisms break down the organ compounds for energy, carbon atoms are released in CO2
Since photosynthesis evolved, these two processes have constituted a balanced cycle of biosphere
