Photosynthesis Lab Report

Emily Chaykosky

Biology I Cellular Processes

Exam #3 Extra Credit

1. Outline in detail (exclude the details of specific chemical reactions) each step in photosynthesis and where each step takes place (light dependent and light independent reactions). What goes in and what is produced?

• The process of photosynthesis converts light energy to chemical energy, which can be used by organisms for different metabolic processes.

Step 1: Light Dependent Reaction (occurs in the thylakoid)

Photosystem II o CO2 and H2O enter the leaf o Light hits the pigment in the membrane of a thylakoid, splitting the H2O into O2 and H+ protons o O2 is released as a biproduct

Photosystem I o The electrons move down to enzymes o Sunlight hits the second pigment

This step makes a six-carbon compound that splits into two molecules of a three-carbon compound, 3-PGA. This reaction is catalyzed by the enzyme rubisco.

Reduction o ATP and NADPH are used to convert the 3-PGA molecules into molecules of a three-carbon sugar, G3P. This stage gets its name because NADPH donates electrons to, or reduces, a three-carbon intermediate to make G3P.

Regeneration of the CO2 acceptor (RuBP) o Some G3P molecules go to make glucose, while others must be recycled to regenerate the RuBP acceptor. Regeneration requires ATP and involves a complex network of reactions.

2. Outline the complete process of cellular respiration. Where does each step take place? What goes in and what is produced?

• The process of cellular respiration oxidizes food molecules, like glucose, to carbon dioxide and water. The energy released is trapped in the form of ATP for use by all the energy-consuming activities of the cell.

Step 1: Glycolysis (occurs in the cytosol) o Six-carbon glucose is converted into two pyruvates (three carbons

o Carbon dioxide is released and NADH is made.

Step 3: Citric Acid Cycle (occurs in the mitochondrial matrix) o The acetyl CoA combines with a four-carbon molecule and goes through a cycle of reactions, ultimately regenerating the four-carbon starting molecule. o ATP, NADH, and FADH2 are made, and carbon dioxide is released.

Step 4: Oxidative Phosphorylation (occurs in the mitochondria) o The NADH and FADH2 produced in previous steps deposit their electrons in the electron transport chain in the inner mitochondrial membrane. o As electrons move down the chain, energy is released and used to pump protons out of the matrix and into the intermembrane space, forming a gradient. o The protons flow back into the matrix through an enzyme called ATP synthase, making ATP. o At the end of the electron transport chain, oxygen accepts electrons and takes up protons to form water.

3. Explain the basic structure of DNA including base pairing. o DNA is made up of six smaller molecules – a five carbon sugar called deoxyribose, a phosphate molecule and four different nitrogenous bases (adenine, thymine, cytosine and