Photosynthesis: Light & Dark Reactions

• Photosynthesis requires sunlight, water, and carbon dioxide and produces glucose and oxygen
• It takes place in two main stages

Light-Independent Reactions (Calvin Cycle)

• Occur in the stroma of chloroplasts
• Do not require light directly but use ATP and NADPH from the light reactions
• Produces glucose (C6H12O6), which plants use for energy and growth
• It involves Rubisco

Light-Dependent Reactions

• Occur in the thylakoid membranes of the chloroplasts
• Requires sunlight to excite electrons in chlorophyll
• Splits water molecules (H2O), producing oxygen (O2) as a byproduct
• Converts light energy into ATP (adenosine triphosphate) and NADPH, which store energy for the next stage
• Photosystem I (PSI) and Photosystem II (PSII) are two protein-pigment complexes in the thylakoid membrane of chloroplasts that drive the light-dependent reactions of photosynthesis, working together to convert light energy into chemical energy

Electron Transport Chain (ETC)

• A series of protein complexes in the thylakoid membrane that transfers electrons from Photosystem II (PSII) to Photosystem I (PSI)
• It generates ATP and NADPH, which power the Calvin cycle

Photosystem II

• Splits water (H2O) and starts the electron transport chain

Photosystem I

• Produces NADPH

Chloroplasts

• Organelles found in plant cells and some algae
• Photosynthesis occurs here, converting sunlight into chemical energy (glucose) while releasing oxygen
• They contain thylakoids which are complex proteins needed for photosynthesis

Thylakoid Membrane

• Contains Chlorophyll which absorbs light energy

Cellular Respiration

• Cells break down glucose into usable energy, mainly in mitochondria
• Breaks down glucose to produces energy in the form of ATP, which requires glucose and oxygen
• Three stages of cellular respiration: Glycolysis, Krebs Cycle, Oxidative Phosphorylation

Glycolysis

• Occurs in the cytoplasm
• Anaerobic
• The process breaks down glucose (C6H12O6) into two molecules of pyruvate (C3H4O3)
• Produces 2 ATP and 2 NADH (energy carriers)

Krebs Cycle

• Occurs in the mitochondrial matrix
• Pyruvate is converted into Acetyl-CoA, which enters the cycle
• Releases CO2 as a waste product
• Produces 2 ATP, NADH, and FADH2 (electron carriers)

Oxidative Phosphorylation

• NADH & FADH2 donate electrons to the ETC
• Electrons move through protein complexes, pumping protons (H+) into the intermembrane space, creating a proton gradient
• Oxygen (O2) acts as the final electron acceptor, forming water (H2O)
• ATP Synthase uses the proton gradient to generate ~34 ATP

ATP

• Adenine (a nitrogenous base)
• Ribose ( a five-carbon sugar)
• Three phosphate groups (Triphosphate)
• The energy currency for life

ADP

• Adenine (a nitrogenous base)
• Ribose (a five-carbon sugar)
• Two phosphate groups (Diphosphate)

Metabolism

• All of the chemical reactions that occur in cells
• Includes Anabolism and catabolism

NADPH

• An energy carrier
• The ability to store and transfer high-energy electrons is key
• It is an essential molecule in photosynthesis and other cellular processes
• Functions as an electron carrier, providing high-energy electrons for biosynthesis and energy production

ATP Synthase

• An enzyme that produces ATP (Adenosine Triphosphate)

• Plays a crucial role in both photosynthesis and cellular respiration by converting ADP and inorganic phosphate (Pi) into ATP using a proton gradient

• Anaerobic means without oxygen

• Aerobic means with oxygen

Enzymes

• Molecules that speed up chemical reactions

Substrates

• Molecules that will react to form new products

Active Site

• A region on an enzyme that binds to a protein or other substance during a reaction

Induced Fit

• A theory that describes how enzymes and proteins change shape to bind to substrates

• Fermentation is a process that uses microorganisms to break down organic compounds into simpler molecules