P HOTOSYNTHESIS

A UTOTROPHS Auto = self Troph = eating Organisms that can produce their own food (energy) from inorganic materials (sunlight)

H ETEROTROPH Hetero = other Troph = eating Organisms that cannot make its own food. Requires organic compounds (other organisms) for its principle source of food.

C HEMICAL E NERGY AND ATP All cells use chemical energy carried by ATP- Adenosine triphosphate. Cells use ATP for functions such as building molecules and moving material through active transport.

ATP The energy carried by ATP is released when a phosphate group is removed from the molecule. ATP become ADP (Adenosine diphosphate) ADP can become ATP again through a series of chemical reactions.

ATP ATP is produced during the breakdown of carbon-based molecules. Different foods provide different amounts of ATP. Carbohydrates (glucose) can make ~ 36 molecules of ATP Lipids can make ~ 146 molecules

S PECIAL C REATURES Some organisms do not need sunlight and photosynthesis as a source of energy. Some organisms live near cracks in the ocean and never see sunlight Chemosynthesis Process by which some organisms use chemical energy instead of light energy to make energy- storing carbon-based molecules

P HOTOSYNTHETIC O RGANISMS ARE P RODUCERS. Producers – Produce the chemical energy for themselves and for other organisms. Photosynthesis – A process that captures energy from sunlight to make sugars that store chemical energy. Chlorophyll – A molecule in chloroplasts that absorb some of the energy in visible light

P ROPERTIES OF L IGHT Organisms use only a small range of wavelengths for photosynthesis, vision, and other processes. – Most of these wavelengths are the ones we see as visible light, a small part of the electromagnetic spectrum from the sun. – Light energy is packages as photons, which vary in energy as a function of wavelength. The shortest are gamma rays with the highest energy; longer are radio waves with the lowest energy. – Photoautotrophs use only a small range ( nm) of wavelengths for photosynthesis.

F ROM S UNLIGHT TO P HOTOSYNTHESIS Pigment molecules on the thylakoid membranes absorb photons. The chlorophylls in green leaves mask the accessory pigments until autumn when the chlorophyll content declines. – A pigment absorbs light of specific wavelengths by acting as an antenna for receiving photon energy. – Chlorophyll a and b pigments absorb blue and red, but reflect green (leaves). Carotenoid pigments absorb blue- violet and blue-green but reflect yellow, orange, and red. Xanthophylls reflect yellow, brown, purple, or blue light; anthocyanins reflect red and purple light in fruit and flowers; phycobilines reflect red or blue-green light and are accessory pigments found in red algae and cyanobacteria.

H ARVESTING THE R AINBOW Violet and red light are the wavelengths best suited for photosynthesis.

P HOTOSYNTHESIS IN C HLOROPLASTS Both stages of photosynthesis occur in the chloroplast. – The semifluid interior (stroma) is the site for the second series of photosynthesis reactions. – Flattened sacs, thylakoids, interconnected by channels weave through the stroma; the first reactions occur here. In the thylakoid membranes, pigments are organized into clusters called photosystems, each consisting of pigment molecules capable of trapping energy from the sun.

P HOTOSYNTHESIS IN C HLOROPLASTS Light-dependent reactions Convert light energy to the chemical bond energy of ATP. Water is split to release oxygen. NADP+ picks up electrons to become NADPH to be used later. Light-independent reactions Assemble sugars and other organic molecules using ATP, NADPH, and CO 2.

F IRST S TAGE : L IGHT -D EPENDENT R EACTION Capture and transfer energy. There are two photosystems involved: photosystem II and photosystem I

L IGHT -D EPENDENT R EACTION Chlorophyll and other light- absorbing molecules capture energy from sunlight. Water molecules are broken down into hydrogen ions, electrons, and oxygen gas ( waste ) Sugars are NOT MADE during this part of photosynthesis Day 1

L IGHT D EPENDENT R EACTION : P HOTOSYSTEM II Chlorophyll and other light absorbing molecules absorb energy from sunlight and that energy is transferred into chloropyll. The energy is then transferred to electrons. – 1. Energy is absorbed in sunlight High energy electrons leave the chorophyll and enter the electron transport chain (a series of proteins in the thylakoid) – 2. Water molecules split – 3. Hydrogen ions transported

L IGHT D EPENDENT R EACTION : P HOTOSYSTEM I Chlorophyll and other light-absorbing molecules absorb sunlight and add it to the electrons from photosystem II 4. Energy is absorbed from sunlight. Electrons are energized. 5. NADPH produced. In photosynthesis NADPH functions like ATP. The molecules of NADPH go to light-independent reactions.

ATP P RODUCTION Final part of the light-reaction. 6. Hydrogen ion diffusion H + ions flow through the thylakoid. 7. ATP produced ATP synthase take the ions as they flow and makes ATP by adding phosphate groups to ADP.

L IGHT D EPENDENT R EACTION : P HOTOSYSTEM II AND P HOTOSYSTEM I

S UMMARY OF L IGHT -D EPENDENT R EACTIONS PRODUCTS ARE: NADPH Used later to make sugar. ATP Used later to make sugar. Oxygen Given off as a waste.

2 ND S TAGE : L IGHT I NDEPENDENT R EACTION Uses energy from the first stage to make sugar. Light-independent reactions take place ANY time that energy is available (it doesn’t need sunlight). Light-independent reactions use the NADPH and ATP made during the light-dependent reactions to make sugar.

T HE C ALVIN -B ENSON C YCLE Uses the NADPH and ATP from the light- dependent reaction, and CO 2 from the atmosphere to make simple sugars.

T HE C ALVIN -B ENSON C YCLE 1. Carbon dioxide added. CO 2 molecules are added to five-carbon molecules already in the Calvin Cycle (RuBP). six-carbon molecules are formed. 2. Three-carbon molecules formed (PGA). ATP and NADPH is used to split the six-carbon molecules into two three- carbon molecules.

T HE C ALVIN -B ENSON C YCLE 3. Three-carbon molecules exit. Most of the three-carbon molecules will stay IN the Calvin Cycle. ONE high energy three- carbon molecule will leave the cycle. When TWO three-carbon molecules leave the cycle, they will bond together to build a six-carbon sugar molecule. Glucose (C 6 H 12 O 6 )

T HE C ALVIN -B ENSON C YCLE 4. Three-carbon molecules recycled (PGAL). Energy from ATP is used to change the three- carbon molecules that stayed in the cycle to five- carbon molecules. These five-carbon molecules stay in the Calvin Cycle. They are added to new CO 2 molecules that enter the cycle.

T HE C ALVIN -B ENSON C YCLE

S UMMARY OF L IGHT -I NDEPENDENT R EACTIONS PRODUCTS ARE: Glucose Used to store energy. NADP + Return to the light- dependent reaction. Will be changed into NADPH there. ADP Return to the light- dependent reaction. Will be changed into ATP there.

F UNCTIONS OF P HOTOSYNTHESIS Provides material for plant growth and development. Simple sugars are bonded together to form complex sugars like cellulose and starch. Starches store energy for the plant. Cellulose is a major component of the cell wall. Helps regulate the Earth’s environment. Removes CO 2 from the atmosphere.

P HOTOSYNTHETIC E QUATION 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 Light Dependent Reactions Includes Photosystem II Electron Transport Chain Photosystem I Light Independent Reactions Includes the Calvin Cycle

P HOTOSYNTHETIC E QUATION