Photosynthesis, Enzyme Function, and Ecological Relationships Flashcards

A set of vocabulary flashcards covering enzyme activity, energy carriers, photosynthesis stages and factors, chloroplast structure, and symbiotic relationships based on the provided lecture notes.

Biomagnification

The process by which a toxin becomes more concentrated in the tissues of organisms with each higher trophic level.

Pepsin

An enzyme produced in the stomach lining of carnivorous mammals that breaks down proteins.

Pepsin Active Site Denaturation

The structural change in pepsin's active site when moving from the highly acidic stomach to the higher, more alkaline pH of the small intestine, resulting in reduced enzyme activity.

Adenosine Triphosphate (ATP)

A complex organic chemical that provides energy to drive many cellular processes, such as muscle contraction, nerve impulse propagation, and chemical synthesis.

ATP-ADP Cycle

The cellular energy shuttle mechanism where ATP releases energy and a phosphate group to form ADP ($ATP \rightleftharpoons ADP + P_i + \text{energy}$), and free energy from respiration or photosynthesis adds a phosphate group back to ADP.

NADP sequence

A coenzyme functioning as a universal electron carrier that accepts electrons and hydrogen ions during photosynthesis to form NADPH ($NADP^+ + \text{electrons} + \text{hydrogen} \rightarrow NADPH$).

NADPH

The reduced coenzyme formed during the light-dependent stage of photosynthesis that transfers high-energy electrons and hydrogen ions to the stroma for carbon fixation.

NADH and FADH2

Coenzymes that transport electrons from one section of the mitochondria to another during cellular respiration.

Photosynthesis

A biochemical process in which autotrophs and producers convert light energy, carbon dioxide, and water into chemical energy stored in organic compounds like glucose.

Photosynthesis Chemical Equations

The complete balanced chemical equation $6CO_2 + 12H_2O \xrightarrow[\text{chlorophyll}]{\text{sunlight}} C_6H_{12}O_6 + 6O_2 + 6H_2O$ and the simplified equation $6CO_2 + 6H_2O \xrightarrow[\text{chlorophyll}]{\text{sunlight}} C_6H_{12}O_6 + 6O_2$.

Chloroplast

A double-membraned organelle containing thylakoid membranes, stroma, and chlorophyll pigments where photosynthesis takes place in plant cells.

Stroma

The colorless, gel-like matrix enclosed by the inner membrane of a chloroplast, rich in enzymes, DNA, RNA, and cytochrome system, where light-independent reactions (Calvin cycle) occur.

Thylakoid

A flat, disk-like sac membrane structure suspended in the stroma of a chloroplast that contains photosynthetic pigments and serves as the site for light-dependent reactions.

Grana

Stacks of thylakoid membranes within the chloroplast that provide a large surface area for the attachment of photosynthetic pigments like chlorophyll-a, chlorophyll-b, carotene, and xanthophyll.

Light-Dependent Stage

The initial stage of photosynthesis taking place in the thylakoid membranes (grana), where absorbed light energy produces ATP, splits water via photolysis, forms NADPH, and releases oxygen gas as a waste product.

Photolysis

The splitting of water molecules using light energy ($H_2O \rightarrow 2H^+ + 2e^- + \frac{1}{2}O_2$) in the thylakoid membranes, supplying electrons to replace those lost by chlorophyll, protons for NADP+, and oxygen gas.

Electron Transport Chain

A series of electron-carrier complexes embedded in the thylakoid membrane through which excited electrons move, driving the production of ATP and NADPH.

Light-Independent Stage

The second stage of photosynthesis (Calvin cycle) taking place in the stroma, using ATP energy and hydrogen from NADPH to reduce carbon dioxide into organic compounds like glucose.

Calvin Cycle

The series of enzyme-catalyzed anabolic reactions in the stroma comprising three stages: Carbon Fixation (catalyzed by Rubisco), Reduction of 3-PGA to G3P, and Regeneration of RuBP.

Carbon Fixation

The initial step of the Calvin cycle in which dissolved carbon dioxide ($CO_2$) in the stroma is combined with organic molecules using energy from ATP and hydrogen from NADPH.

Limiting Factor

An abiotic factor (such as light intensity, temperature, or carbon dioxide concentration) that restricts the rate of photosynthesis when it is in shortest supply, regardless of other factors.

Light Intensity Effect on Photosynthesis

At low levels, increasing light intensity increases the rate of photolysis and photosynthesis; at higher levels (around $38\%$), the rate plateaus because another factor becomes limiting.

Temperature Effect on Photosynthesis

Increasing temperature increases the rate of enzyme-catalyzed light-independent reactions up to an optimum ($25^\circ\text{C}-35^\circ\text{C}$), above which rate declines due to enzyme denaturation.

Carbon Dioxide Concentration Effect on Photosynthesis

Increasing $CO_2$ concentration increases the rate of carbon fixation in light-independent reactions until reaching a maximum plateau (around $0.1\%$).

Symbiosis

A general term for an ecological relationship in which individuals of two or more species live together, benefiting at least one of the species.

Parasitism

A symbiotic relationship in which one organism (the parasite) benefits at the expense of another organism (the host).

Mutualism

A symbiotic relationship in which both participating species benefit and neither is harmed.

Commensalism

A symbiotic relationship in which one species benefits while the other species neither benefits nor is harmed.

Pollinators

Organisms essential for flowering plant reproduction that transfer pollen from one plant to another.

Seed Dispersers

Organisms that eat fruits and seeds for nutrition and deposit viable seeds in new locations through defecation, aiding seed germination and ecosystem biodiversity.