Photosynthesis Chapter 8 (pages )

Where energy comes from light energyPlants and some other types of organisms use light energy from the to produce food ▫Autotrophs ▫Autotrophs: organisms that make their own food  Use the sun’s energy to help make their food ▫Heterotrophs ▫Heterotrophs: organisms that do not make their own food  Where does their energy come from?

ATP Adenosine TriphosphateAdenosine Triphosphate ▫Definition: One of the principal chemical compounds that cells use to store and release energy ▫Composed of:  5-carbon sugar (ribose)  Adenine  Three phosphate groups adenineribose 3 phosphate groups

ADP Adenosine Diphosphate ▫Looks almost like ATP, but only two phosphate groups ▫When a cell has energy available to store, tacks on that extra phosphate group to ADP  ATP

Storing vs. Releasing Energy To store energy  add on a phosphate group To release energy  remove a phosphate group

Using ATP Active transportActive transport Cell movementCell movement Responding the chemical signalsResponding the chemical signals Protein synthesisProtein synthesis Nucleic Acid synthesisNucleic Acid synthesis  ATP is not good for storing energy  glucose contains 90x the chemical energy that one ATP molecule has.  Regenerate ATP from ADP by using energy in foods like glucose  ATP is not good for storing energy  glucose contains 90x the chemical energy that one ATP molecule has.  Regenerate ATP from ADP by using energy in foods like glucose

The Scientists of Photosynthesis Van HelmontVan Helmont: found plants gain mass from water PriestleyPriestley: plants release oxygen IngenhouszIngenhousz: plants produce oxygen in sunlight, not in dark MayerMayer: proposed plants convert light into chemical energy CalvinCalvin: traced chemical path that carbon follows to form glucose (Calvin Cycle)  we will get to this later

Photosynthesis PhotosynthesisPhotosynthesis the use of energy from sunlight to convert water and carbon dioxide into high-energy carbohydrates – sugar and starches – and oxygen as a waste product

Light and Pigments chlorophyllIn addition to H2O and CO2, light and chlorophyll needed ▫Where’s chlorophyll found? In chloroplasts! Plants gather sun’s energy with light-absorbing molecules called pigments chlorophyll ▫Principal pigment in plants  chlorophyll ▫Two types: chlorophyll a and chlorophyll b  Absorb light in blue and red region of visible light spectrum  When light is absorbed, energy levels of electrons rise

Inside a Chloroplast ThylakoidStroma Granum Sac-like structure; Contains the photosynthetic pigments, reaction centers for LDR, and the electron transport chain Stack of thylakoids The inner fluid of the chloroplast between the grana which contains various enzymes and where the Calvin Cycle occurs

Electron Carriers Sunlight excites electrons – hold energy ▫Would you want to transport the electron yourself or have something else transport it? Carrier needed to transport excited electron ▫Carrier known as = electron transport chain NADP + ▫Actual Transporter = NADP +  Holds 2 high energy electrons  Holds H + NADP NADP + e- - H+H+

Light Dependent Reactions

Pigments absorb light in photosystem II  electrons excited  passed to ETC  thylakoid membrane replaces electrons with H2O  H +, O, electrons Excited electrons move through ETC to photosystem I  energy fuels ETC to move H+ from stroma to inner thylakoid space Pigments in photosystem I use light energy to reenergize electrons  NADP+ picks up electrons and H+  NADPH When electrons are passed from chlorophyll to NADP+, more H+ ions are pumped across the membrane  difference in charges provides energy to make ATP ATP synthase allows H+ ions to pass through  ATP synthase rotates  As it rotates, grabs ADP and bonds it to Phosphate group  ATP!

Calvin Cycle Also known as the light independent reactions (or dark reactions) ▫No light required for them to start Occur in the stroma of the chloroplast Use products of LDR as their reactants  NADPH, ATP Give the products NADP +, ADP, high energy sugars Multiple steps!

Calvin Cycle Multiple steps take CO2 and convert into multi- carbon containing molecules ▫Step 1: 6 CO2 and 6, 5-Carbon Molecules  12, 3- Carbon Molecules ▫Step 2:  ATP  ADP (energy storage for LDR)  NADPH  NADP+ (electron carrier for LDR) ▫Step 2: 12, 3-Carbon Molecules  2 fall off to make sugar (remember 6 carbons are in a monosaccharide) ▫Step 3: 10 3-Carbon Molecules  6, 5-Carbon Molecules  ATP  ADP

Calvin Cycle

Quick review LDRLIR Reactants ADP, NADP+, H2O ATP, NADPH, CO2 ProductsOXYGENGLUCOSE Location Thylakoid Membrane Stroma

Factors that alter photosynthesis Water availability ▫Which scientist figured this out?  Van Helmont! Intensity of light ▫Which scientists figured this out?  Ingenhousz! Temperature ▫What temperature do enzymes function best?  98.6 degrees