Calvin Cycle and Photosynthesis

These flashcards cover key vocabulary related to the Calvin cycle and photosynthesis, helping students understand important concepts and processes.

Calvin Cycle

A series of biochemical reactions that takes place in the stroma of chloroplasts and uses ATP and NADPH to convert CO2 into sugar.

ATP

Adenosine triphosphate, the energy currency of the cell used in the Calvin cycle.

NADPH

Nicotinamide adenine dinucleotide phosphate, a reducing agent that donates electrons during the Calvin cycle.

Carbon Fixation

The process of converting inorganic CO2 into organic compounds during the first phase of the Calvin cycle.

Glyceraldehyde 3-phosphate (G3P)

A three-carbon sugar produced in the Calvin cycle; the net gain of carbohydrate after several turns of the cycle.

Ribulose bisphosphate (RuBP)

A five-carbon sugar that acts as the starting material for the Calvin cycle.

Rubisco

The enzyme ribulose bisphosphate carboxylase/oxygenase that catalyzes the first step of carbon fixation in the Calvin cycle.

Anabolic

A metabolic pathway that builds larger molecules from smaller ones; characteristic of the Calvin cycle.

Catabolic

A metabolic pathway that breaks down larger molecules into smaller ones; characteristic of the citric acid cycle.

Reduction Phase

The second phase of the Calvin cycle where ATP and NADPH convert 3-PGA into G3P.

Stroma

The liquid matrix inside chloroplasts where the Calvin cycle takes place.

Photorespiration

A metabolic pathway that consumes oxygen and releases CO2, occurring when rubisco adds O2 instead of CO2.

C3 plants

Plants that use rubisco for carbon fixation, producing a three-carbon compound during photosynthesis.

C4 plants

Plants that fix carbon into a four-carbon compound to minimize photorespiration under hot, dry conditions.

CAM plants

Plants that fix CO2 at night into organic acids, conserving water and minimizing photorespiration.

NADP+

The oxidized form of NADPH, which serves as an electron acceptor during the Calvin cycle.

Photosynthesis

The process by which green plants use sunlight to synthesize foods from CO2 and water.

Light Reactions

The first stage of photosynthesis that converts solar energy into chemical energy stored in ATP and NADPH.

ATP Synthase

An enzyme that produces ATP from ADP and inorganic phosphate during photosynthesis.

Oxygen

A byproduct of photosynthesis produced during the light reactions.

Chloroplast

The organelle in plant cells where photosynthesis occurs.

Stomata

Small openings on leaf surfaces that allow for gas exchange during photosynthesis.

Carbon Dioxide (CO2)

The inorganic gas that is fixed during the Calvin cycle to create glucose.

Sugar Production

The end goal of the Calvin cycle, which produces carbohydrates for energy storage.

Three Phases

The Calvin cycle is divided into three phases: carbon fixation, reduction, and regeneration.

Carbon Skeletons

The structure formed during the regeneration phase of the Calvin cycle to reform RuBP.

Molecules of ATP

During the Calvin cycle, nine ATP molecules are consumed for the net gain of one G3P.

Molecules of NADPH

Six NADPH molecules are consumed in the Calvin cycle for the reduction phase.

Glycolysis

The metabolic pathway that breaks down glucose to produce energy; related to the Calvin cycle through G3P.

Light Dependent Reactions

Reactions in photosynthesis that require light energy to produce ATP and NADPH.

Endergonic Reactions

Reactions that require energy input to proceed; applicable in the reactions of the Calvin cycle.

Energy Consumption

The process of utilizing ATP and NADPH in the Calvin cycle to build glucose.

Organic Acids

Compounds produced by some plants during carbon fixation, important in CAM photosynthesis.

Mesophyll Cells

Cells in leaves where photosynthesis occurs and where carbon is initially fixed in CAM plants.

Bundle-sheath Cells

Cells that surround the vascular tissue in C4 plants where the Calvin cycle occurs.

Disruptions in Carbon Fixation

Factors affecting the Calvin cycle’s efficiency, such as environmental stresses at stomata.

Emergent Property

Characteristics of photosynthesis that arise from the coordinated functions of the light and Calvin cycles.

Succulent Plants

Plants, such as cacti and aloe, that conserve water and use CAM for carbon fixation.

Photosynthetic Adaptations

Evolutionary changes in plants that optimize photosynthesis under varying environmental conditions.

Environmental Stresses

Conditions, like drought, that affect plant metabolism and carbon fixation efficiency.

Optimal Photosynthesis

Achieved when stomata are open, allowing maximum CO2 entry in plants.

Photosynthetic Output

The total amount of sugars produced through photosynthesis, critical for plant energy.

Calvin Cycle Efficiency

Refers to the effectiveness of the cycle in producing sugars under various conditions.

Carbon Concentration

Refers to the levels of CO2 available for photosynthesis, influenced by environmental conditions.

Agricultural Implications

Understanding the Calvin cycle aids in improving crop yield through optimized carbon fixation.

Soil Nutrients

Essential elements required for plant growth, influencing photosynthetic activity and sugar production.

Transpiration

The process of water movement through a plant and its evaporation from aerial parts, affecting photosynthesis.

Aerobic Conditions

The environment where photorespiration is more likely to occur, impacting the Calvin cycle efficiency.

Global CO2 Trends

Current atmospheric changes in carbon dioxide levels affecting plant growth and photosynthesis.

Plant Metabolism

Refers to the biochemical processes that occur within plants including photosynthesis and respiration.

Overall Equation of Photosynthesis

6CO2 + 6H2O + \text{Light Energy} \rightarrow C6H{12}O6 + 6O2

Regeneration Phase

The third phase of the Calvin cycle where ATP is used to convert 10 molecules of G3P back into 6 molecules of RuBP.

3-Phosphoglycerate (3-PGA)

A three-carbon compound formed during carbon fixation in the Calvin cycle when CO2 combines with RuBP.

Role of ATP in Regeneration

ATP provides the energy needed to convert G3P into RuBP, allowing the Calvin cycle to continue.

Spatial Separation (C4 plants)

The evolutionary adaptation in C4 plants where carbon fixation and the Calvin cycle occur in different types of cells (mesophyll and bundle-sheath cells) to minimize photorespiration.

Temporal Separation (CAM plants)

The evolutionary adaptation in CAM plants where CO2 is fixed at night and the Calvin cycle occurs during the day, allowing stomata to be closed during hot daytime hours to conserve water.

Phosphoenolpyruvate (PEP) Carboxylase

An enzyme in C4 and CAM plants that fixes CO2 into a four-carbon compound, having a higher affinity for CO2 than rubisco and no affinity for O2.

Malate

A four-carbon organic acid produced in C4 and CAM plants that stores CO2 before its release to the Calvin cycle.

Sucrose Production

The primary form in which carbohydrates are transported from leaves to other parts of the plant after being produced in the Calvin cycle.

Starch

A storage polysaccharide synthesized from glucose, commonly stored in chloroplasts or other plastids in plants.

Light Intensity

A factor influencing the rate of photosynthesis; higher light intensity generally increases the rate up to a saturation point.

Temperature's Effect on Calvin Cycle

The Calvin cycle is sensitive to temperature; optimal temperatures maximize enzyme activity, while extreme temperatures can denature enzymes or reduce CO2 solubility.

Water Availability

A crucial factor for photosynthesis; water stress can cause stomata to close, limiting CO2 intake and reducing photosynthetic rates.

Chlorophyll

The green pigment found in chloroplasts that absorbs light energy for photosynthesis.

Thylakoids

Disk-like sacs within chloroplasts where the light-dependent reactions of photosynthesis take place.

Grana

Stacks of thylakoids within the chloroplasts.

Chemiosmosis

The process of ATP synthesis in chloroplasts (and mitochondria) driven by the movement of protons across a membrane, powered by electron transport.

Photophosphorylation

The process of generating ATP from ADP and phosphate by means of chemiosmosis, using a proton-motive force generated across the thylakoid membrane during the light reactions.

Photoautotrophs

Organisms that use light as source of energy to synthesize organic compounds from inorganic substances, such as plants, algae, and some bacteria.

Primary Producers

Organisms, primarily photoautotrophs, that produce organic matter from inorganic compounds, forming the base of most food webs.

Electron Transport Chain (Photosynthesis)

A series of protein complexes and molecules that transfer electrons excited by light energy, ultimately generating ATP and NADPH during the light reactions.

Photosystem I (PSI)

A pigment-protein complex in the thylakoid membrane that absorbs light at a peak wavelength of 700 \text{ nm} and passes excited electrons to NADP+.

Photosystem II (PSII)

A pigment-protein complex in the thylakoid membrane that absorbs light at a peak wavelength of 680 \text{ nm} and is responsible for splitting water and releasing oxygen.

Wavelength of Light

A characteristic of light energy that influences the rate of photosynthesis, as different pigments absorb specific wavelengths more efficiently.

Cyclic Electron Flow

A pathway of electron flow during the light reactions that only involves Photosystem I and produces ATP but not NADPH or oxygen.

Non-Cyclic Electron Flow

The primary pathway of electron flow during the light reactions that involves both Photosystem I and Photosystem II, producing ATP, NADPH, and oxygen.

Glycerate 1,3-bisphosphate

An intermediate compound in the reduction phase of the Calvin cycle, formed from 3-PGA by ATP.

RuBisCO's Dual Nature

The enzyme Rubisco can act as a carboxylase (fixing CO2) or an oxygenase (initiating photorespiration), depending on the relative concentrations of CO2 and O2.

Photons

Discrete packets of light energy that are absorbed by pigments in photosynthetic organisms to energize electrons.

Proton-Motive Force

The potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions across a biological