Do Now 12/20 First task – the labs! 1.Inspect your tubes. Many of the yeast/sucrose tubes are completely full of gas and are floating. If so, enter the following in your data table: Day 1 Final air level = “Full” Day 1 Change in Air Level = “Full” Day 1 rate of gas production = “> 25 ml / day” 2.Record data for the yeast/water control tube. 3.Await instructions about how to proceed.

Anaerobic reset Pour the contents of the yeast/sucrose tubes into a beaker. Pour the contents back into the small tube, and invert once again, like we did yesterday. Record the size of the new air bubble as “Day 1 initial air level.”

Photosynthesis as a Process

Cellular Respiration Heterotrophs can’t make their own food, like autotrophs can. The process of cellular respiration is how organisms get the energy they need from the food they take in.

Cellular Respiration How heterotrophs get energy out of the organic chemicals they eat

The Carbon Cycle of Life C 6 H 12 O 6 ATP Energy Produced Light Energy CO 2 Photo- synthesis Respiration

Photosynthesis Happens in Chloroplasts Thylakoid Stroma

Photosynthesis Happens in Two Main Steps The light reactions of photosynthesis are responsible for capturing the energy of light, and storing it in chemicals like ATP. Those chemicals are then used by the Calvin Cycle to build sugars the plant needs to grow and survive.

Chlorophyll is the green pigment that green plants use to capture light energy

Step 1: Chlorophyll in the chloroplast captures light energy Light strikes chlorophyll Electrons are knocked out of chlorophyll by light… they travel to step 2 Electrons are replaced when water is split Chlorophyll Light electrons H2OH2O 2 H + O

Do Now 12/15 Use this diagram to complete the 8-step description of the light reactions you got yesterday.

Step 2: The Electron Transport Chain Makes a Hydrogen Gradient e- H+H+ H+H+ H+H+ H+H+ H+H+ Electrical energy allows ACTIVE transport from low concentration to high. Inside thylakoid Stroma H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+

H+ is at a high concentration in the thylakoids

Step 3: ATP is made by the enzyme ATP synthase The energy to make ATP from ADP + P comes from the concentration gradient of hydrogen ions across the thylakoid membrane. ATPsynthase is a key enzyme that makes ATP Inside Thylakoid Stroma

Light Reaction Summary Light energy is captured by chlorophyll in the chloroplast. Light energy is stored in ATP and other molecules (NADPH). The electrons used in the process come from the splitting of water. This is why plants make oxygen.

The Calvin Cycle In the Calvin Cycle build sugars from CO 2. (Carbon Fixation) The energy for the process comes from ATP made during the light reaction. This process also happens in the chloroplast (specifically, the stroma).

Calvin Cycle… it’s complicated What you need to know FOR NOW: –CO 2 molecules are combined to make sugar (C 6 H 12 O 6 ) –Requires lots of ATP

Calvin Cycle = Carbon Fixation Carbon fixation is the process of turning inorganic carbon (like CO 2 ) into organic carbon (like C 6 H 12 O 6 ) Carbon fixation is the source of ALL CARBON BIOMASS ON EARTH. Thank you, autotrophs!

The Calvin Cycle is an Energy Hog To make 2 molecules of G3P required for a single glucose molecule, the cell must use 18 ATP molecules and 6 NADPH molecules. Bottom line: it takes a lot of energy to turn CO2 and water into glucose! 18 ATPs per molecule!

How did Dr. Calvin figure this out, anyway? Melvin Calvin introduced radioactive carbon ( 14 C) dioxide to photoautotrophs that were actively growing. He then killed them at various times and analyzed their chemical make up by autoradiological 2 dimensional chromatography. Thus, he could see which compounds were produced in what order. It took him about 10 years… and he won a Nobel Prize for his efforts in 1961