Chapter 5 Photosynthesis

5-1 NRG and Living Things Where does the NRG we use come from. Directly or indirectly from the sun Plants get their NRG directly from the sun How?

Plants use photosynthesis to convert light NRG into chemical NRG Plants are autotrophs Autotrophs convert light NRG or inorganic compounds to make organic compounds Photoautotrophs use the sun Chemoautotrophs use inorganic compounds

Heterotrophs must eat things to aquire NRG from organic compounds Cellular Respiration is how most heterotrophs, and most autotrophs get their NRG from organic compounds Similar to burning fuel (uses oxygen), to build ATP

Organisms get NRG from compounds by breaking chemical bonds Some NRG gets released as heat when breaking chemical bonds Most of the remaining NRG gets temporarily stored as ATP

ATP ATP yields ADP + P + NRG Made of a nitrogen base, ribose sugar, and three phosphate groups How is the NRG released? By breaking the chemical bond between phophate groups

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5-2 Photosynthesis Stage One and Two (Light RXNS) Chloroplast contain pigments that absorb solar NRG Primary pigment is called chlorophyll and absorbs blue, red light waves Two types of chlorophyll a and b

Carotenoids are yellow and orange pigments They absorb different wavelengths of light

Stage 1 Pigments are located in chloroplast Embedded in the membranes of thylakoids (disk shaped) When light hits them, NRG is transferred to electrons Makes them “excited”

Excited electrons jump from chlorophyll molecules to other molecules in the thylakoid These electrons fuel the second stage of photosynthesis

Plants must replace these lost electrons Water molecules get spilt by an enzyme Electrons are taken from hydrogen atoms, leaving H+ The oxygen is combined to form oxygen gas

Stage 2 Electrons are used to produce new molecules that store chemcal NRG Electrons are passed between molecules in the thylakoid membrane Called the Electron Transport Chain

One type of e- chain contains a protein that acts like a membrane pump The e- lose their NRG as they pass through the protein This NRG is used to pump H+ into the thylakoid This creates a concentration gradient inside the thylakoid

The H+ then diffuse out the thylakoid through special carrier proteins These carrier proteins function as enzymes and ion channels These proteins catalyze a reaction that adds a phosphate group to ADP to create ATP

ATP used to fuel stage 3

Another e- transport chain makes NADPH NADPH is an electron carrier that provides NRG to make carbon-hydrogen bonds in stage 3 NADP+ + Hydrogen ions=NADPH

Light RXNS Summary Pigments in thylakoids capture solar NRG Electrons become excited and move through the e- transport chain Electrons are replaced by splitting water molecules H+ accumulate in thylakoid, helping to create ATP and NADPH

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