Chemical Equations in Biology: Photosynthesis and Respiration

Vocabulary flashcards covering chemical equations in biology, including detailed stages and components of photosynthesis, cellular respiration, the nitrogen cycle, acid rain, and ozone depletion.

Reactants

The starting materials in a chemical reaction, written on the left side of a chemical equation.

Products

The end results formed by a chemical reaction, written on the right side of a chemical equation.

Coefficients

Numbers placed before chemical formulas in an equation to show the relative amounts of each substance and ensure the equation is balanced.

Components of a Chemical Equation

A chemical equation illustrating reactants, products, and coefficients, such as $\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}$.

Law of Conservation of Mass

A law formulated by Antoine Lavoisier stating that mass cannot be created or destroyed in a closed system, so total mass of reactants equals total mass of products.

Photosynthesis

The process by which green plants convert light energy into chemical energy (glucose) inside chloroplasts, releasing oxygen as a byproduct.

Photosynthesis Chemical Equation

The general chemical equation for photosynthesis: $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$.

ATP (Adenosine Triphosphate)

An energy-storing molecule that acts as the cell's energy currency to power cellular processes.

NADPH

Nicotinamide Adenine Dinucleotide Phosphate (reduced form), a high-energy electron carrier vital for photosynthesis and anabolic building reactions.

NADP+

Nicotinamide Adenine Dinucleotide Phosphate, an electron carrier molecule that becomes NADPH when it accepts electrons and hydrogen ions.

Thylakoid

Disc-shaped membrane sacs in chloroplasts where the light-dependent reactions of photosynthesis occur.

Granum

A stack of thylakoid membrane sacs inside a chloroplast.

Stroma

The fluid space surrounding the grana inside a chloroplast; the site of the Calvin Cycle.

Light-Dependent Reactions

The first stage of photosynthesis occurring in thylakoid membranes, which uses light to split water (2\text{H}_2\text{O} + \text{light energy} \rightarrow 4\text{H}^\u002B + 4e^- + \text{O}_2) and produces ATP, NADPH, and oxygen.

Thylakoid Electron Transport Chain

Diagram illustrating the light-dependent reactions where Photosystems II and I, electron transport proteins, and ATP synthase produce ATP and NADPH.

Calvin Cycle (Light-Independent Reactions)

The second stage of photosynthesis occurring in the stroma, using $\text{CO}_2$, ATP, and NADPH to produce sugar through carbon fixation, reduction, and regeneration.

Calvin Cycle Stages

Diagram showing the three main stages of the Calvin Cycle: Carbon Fixation (catalyzed by rubisco), Reduction, and Regeneration of the RuBP acceptor.

G3P (Glyceraldehyde-3-phosphate)

A three-carbon sugar molecule produced by the Calvin Cycle; two G3P molecules are required to build one six-carbon glucose molecule.

Cellular Respiration

The process by which cells break down glucose in mitochondria to release energy, producing ATP, carbon dioxide, and water.

Cellular Respiration Chemical Equation

The general chemical equation for cellular respiration: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{energy (ATP)}$.

Mitochondrion Structure

Structure of the cellular organelle responsible for respiration, showing outer membrane, inner membrane, cristae, matrix, DNA, and ribosomes.

Glycolysis

The anaerobic first stage of cellular respiration occurring in the cytoplasm/cytosol, breaking down glucose into two pyruvate molecules and generating a net of 2 ATP and 2 NADH.

Citric Acid Cycle (Krebs Cycle)

The second stage of cellular respiration taking place in the mitochondrial matrix, completing the breakdown of pyruvate/acetyl CoA to generate $\text{CO}_2$, ATP/GTP, NADH, and $\text{FADH}_2$.

Krebs Cycle Steps and Enzymes

Diagram detailing the pathway converting acetyl CoA and oxaloacetate into citrate, isocitrate, $\alpha$-ketoglutarate, succinyl CoA, succinate, fumarate, malate, and oxaloacetate.

Citrate Synthase

The enzyme catalyzing step 1 of the Krebs cycle, combining acetyl CoA with 4-carbon oxaloacetate to form 6-carbon citrate.

Isocitrate Dehydrogenase

An $\text{NAD}^u002B$-dependent enzyme catalyzing step 3 of the Krebs cycle, converting isocitrate to 5-carbon $\alpha$-ketoglutarate with decarboxylation and NADH generation.

Succinyl-CoA Synthetase

The enzyme catalyzing step 5 of the Krebs cycle, converting succinyl CoA to succinate coupled with substrate-level phosphorylation of GDP to GTP.

Electron Transport Chain (ETC) and Oxidative Phosphorylation

The final stage of cellular respiration in the inner mitochondrial membrane, where electrons from NADH and $\text{FADH}_2$ create a proton gradient driving ATP synthase, with oxygen as final electron acceptor.

Fermentation

An anaerobic process that breaks down glucose to produce ATP without oxygen, releasing either lactic acid or alcohol and carbon dioxide as end products.

Lactic Acid Fermentation

A form of anaerobic fermentation converting glucose into two lactic acid molecules and two ATP: $\text{C}_6\text{H}_{12}\text{O}_6 \rightarrow 2\text{C}_3\text{H}_6\text{O}_3 + 2\text{ATP}$.

Alcoholic Fermentation

A form of anaerobic fermentation converting glucose into two ethanol molecules, two carbon dioxide molecules, and two ATP: $\text{C}_6\text{H}_{12}\text{O}_6 \rightarrow 2\text{C}_2\text{H}_5\text{OH} + 2\text{CO}_2 + 2\text{ATP}$.

Nitrogen Fixation

The biological process carried out by certain bacteria and archaea that converts atmospheric nitrogen ($\text{N}_2$) into ammonia ($\text{NH}_3$): \text{N}_2 + 8\text{H}^\u002B + 8e^- \rightarrow 2\text{NH}_3 + \text{H}_2.

Root Nodules

Structures on plant roots containing symbiotic bacteria that fix atmospheric nitrogen into usable forms for plants.

Denitrification

The process carried out by denitrifying bacteria that converts soil nitrate back into atmospheric nitrogen gas: 2\text{NO}_3^- + 10e^- + 12\text{H}^\u002B \rightarrow \text{N}_2 + 6\text{H}_2\text{O}.

Acid Rain

Precipitation formed when atmospheric sulfur dioxide ($\text{SO}_2$) and nitrogen oxides ($\text{NO}_x$) react with water to form sulfurous ($\text{H}_2\text{SO}_3$), nitrous ($\text{HNO}_2$), and nitric ($\text{HNO}_3$) acids.

Acid Rain Deposition

Diagram showing emission sources, chemical oxidation to sulfurous/nitric acids, and wet/dry deposition of dissolved acids onto ecosystems.

Ozone Depletion

The breakdown of ozone ($\text{O}_3$) molecules initiated when UV light liberates chlorine radicals ($\text{Cl}$) from chlorofluorocarbons (CFCs).