Chapters 8 & 9 Photosynthesis & Cellular Respiration Regular Biology Waggy

Photosynthesis Objectives Describe the role of chlorophyll in photosynthesis Summarize the main events of the steps of photosynthesis & the Calvin cycle Explain how ATP is formed during photosynthesis Explain how environmental factors influence photosynthesis

Photosynthesis Is the most valuable biological system on the planet! Simply put, photosynthesis is the process by which plants combine sunlight, carbon dioxide, and water to create sugars (carbohydrates) Plants are the ONLY living thing on earth that can convert the suns energy into a usable form

Living organisms that can make their own food are called autotrophs Autotrophs are typically the first step in the food chain because of this ability There are two parts to photosynthesis: 1. Light reactions: PSII & PSI 2. Calvin cycle

STEP 1: Light Reactions Plant cells contain chloroplasts Chloroplasts are cell organelles that contain chlorophyll Chlorophyll is a green pigment & is kept in coin shaped structures called thylakoids (they look like a stack of coins)

Photosystem II (PSII) sunlight strikes the chlorophyll & is absorbed The extra energy from the sun causes an electron to be released from the chlorophyll molecule This excited electron jumps from the chlorophyll molecule & is caught by the primary electron acceptor

The electron (e-) is now sent through an electron transport chain until it reaches a chlorophyll molecule in Photosystem I (PSI) The electron replaces the missing e- in PSI.

SUNLIGHT PSII Hydrolysis Chlorophyll Gives up e- Excited e- jumps e- is caught by e- acceptor e- transport chain e- replaces one lost in PSI

Photosystem I (PSI) Chlorophyll in PSI is struck by sunlight & an e- becomes excited The e- is caught by another primary e- acceptor Now the e- moves through a second electron transport chain At the end of the second transport chain, the e- combines with H+ to form a Hydrogen atom

This Hydrogen atom attaches to a NADP molecule creating NADPH NADPH is a form of energy like ATP NADP: nicotinamide adenine dinucleotide phosphate ATP: adenosine triphosphate

SUNLIGHT PSII PSI Hydrolysis Chlorophyll Gives up e- Chlorophyll Gives up e- Excited e- jumps Excited e- jumps e- is caught by e- acceptor e- is caught by e- acceptor e- transport chain e- transport chain NADPH formed e- replaces one lost in PSI

The Production of ATP: ATP is also produced in the thylakoid membrane in a process called chemiosmosis