Lecture 9b: Bioenergetics- photosynthesis Flashcards
Autotrophs
are able to carry out carbon fixation using CO2 as a carbon source; also called primary producer
organisms obtain carbon in one of 2 ways;
Autotrophs and heterotrophs
Heterotrophs
organisms are unable to synthesize its own organic carbon-based compounds and as a result, they feed on organic matter
organisms obtain energy in one of 2 ways;
phototrophs and chemotrophs
phototrophs
are photosynthetic organisms that use light as their energy source
Chemotrophs
are organisms that obtain energy by the oxidation of reduced compounds (electron donors) in their environments
photoautotrophs
plants, algae, and cyanobacteria
photosynthesis
the process by which all photoautotrophs use light energy to make sugars and other organic food molecules from CO2 and water (creates biomass and oxygen)
Light reactions
the light driven production of ATP (phosphorylation) and NADPH
Carbon fixation
the conversion of CO2 to carbohydrates
Chloroplast
An organelle found in plants and photosynthetic protists absorbs sunlight and uses it to power the synthesis of organic food molecules (sugar)
Structure of chloroplast:
- out and inner membranes
- Stroma
- thylakoid (Granum)
- thylakoid membrane
- thylakoid lumen
Photosynthetic pigments:
- Chlorophyll a
- Chlorophyll b
- Carotenoids
Chlorophyll a
absorbs light within the violet, blue and red wavelengths while mainly reflecting green
Chlorophyll b
extends the absorption spectrum and acts as an accessory pigment that also participates in light absorption
carotenoids
another accessory pigment that absorb different wavelengths of light
Photosystem
a light-harvesting unit of a chloroplast thylakoid membrane, containing a reaction center plus antenna complexes (2 types)
2 types of photosystems
photosystem I + photosystem II
Photosystem I
(PS I), also called P700 because the reaction center associated with PS I has an absorption peak at 700nm (red light)
photosystem II
(PS II), called P680 made up of a reaction center with an absorption peak of about 680 nm (orange shade of red)
Noncyclic electron flow
involves both Photosystems I & II and produces ATP and NADPH
Cyclic electron flow
uses only photosystem I and produces only ATP
- no h20 splitting occurs
- ATP is formed by chemiosmosis
Carbon Fixation
Step 1- carbon fixation
Step 2- Energy consumption and carbon reduction
Step 3- RuBP regeneration
