BIOL - Quiz 2, Ch 10

mesophyll cells

the tissue in the interior of the leaf, where chloroplasts are mainly found

thylakoid

flattened sacs in the chloroplasts bounded by membranes where light reactions occur

stroma

fluid in the chloroplasts

electromagnetic spectrum

the entire range of radiation

absorption spectrum

a graph plotting a pigments light absorption versus wavelength

action spectrum

profiles the relative effectiveness of different wavelengths of radiation in driving the process

chlorophyll a

the key light-capturing pigment that participates directly in light reactions

chlorophyll b

accessory pigment that captures light energy and transfers it to chlorophyll a

carotenoid

accessory pigments that are hydrocarbons, various shades of yellow and orange because they absorb violet and blue-green light.

photosystem I

a protein-pigment complex located in the outer thylakoid membranes, absorbs longer wavelengths, catalyzes transfer of electrons, produces NADPH for the calvin cycle, and participates in cyclic phosphorylation

photosystem II

a protein-pigment complex in the inner thylakoid membrane that captures light energy to split water molecules and provide electrons, release oxygen, and generate high-energy electrons for photosynthesis

light harvesting complex

protein-pigment assembly that captures solar energy and transfers it to photosynthetic reaction centers, enabling efficient photosynthesis

electron acceptor

receives excited electrons during the light-dependent reactions, occurs in the thylakoid membranes of chloroplasts and involves two photosystems

chemiosmosis

process by which ions, typically H⁺, move across a semipermeable membrane down their electrochemical gradient, driving the synthesis of ATP

calvin cycle / dark reactions

series of biochemical processes in the stroma that convert carbon dioxide into glucose and other organic molecules using energy from ATP and reducing power from NADPH produced in the light-dependent reactions

PG = 3-phosphoglycerate

three-carbon molecule with a phosphate group attached to its third carbon, plays a crucial role as an intermediate in both glycolysis and the Calvin cycle. In glycolysis, 3PG is formed from 1,3-bisphosphoglycerate and is essential for converting glucose into pyruvate

BPG = 1,3-bisphosphoglycerate

three-carbon organic molecule found in most living organisms that serves as a metabolic intermediate in both glycolysis during respiration and the calvin cycle during photosynthesis

CAM = crassulacean acid metabolism

closes stomata during day to conserve water and prevent CO2 from entering, opens stomata during night to take up CO2 to carry out carbon fixation

ATP synthase enzyme

enzyme that catalyzes the production of adenosine triphosphate (ATP), the primary energy carrier in cells, by utilizing the energy from a proton gradient across a membrane

thylakoid space

internal compartment enclosed by the thylakoid membrane within chloroplasts, where protons accumulate during the light-dependent reactions

NADP = reductase enzyme

a coenzyme which is oxidized and an electron acceptor, plays a significant role in the calvin cycle of photosynthesis, where it converts carbon dioxide into glucose

NADPH = nicotinamide adenine dinucleotide phosphate

a coenzyme that serves as a reducing agent, providing electrons for the synthesis of large molecules from smaller precursors

G3P = Glyceraldehyde-3-phosphate

the carbohydrate produced directly from the calvin cycle, for one molecule the cycle must take place three times

photorespiration

process that occurs in the light and consumes O2 while producing CO2

PEPCO = phosphoenolpyruvate carboxylase

an enzyme that catalyzes the conversion of phosphoenolpyruvate (PEP) to oxaloacetate and inorganic phosphate.

oxaloacetate

a central 4-C intermediate in the citric acid cycle, where it reacts with acetyl-CoA to form citrate, initiating a series of reactions that generate energy in the form of NADH, FADH₂, and ultimately ATP

bundle sheath cells

photosynthetic cell arranged into tightly packed sheaths around the veins of the leaf

photophosphorylation

the process of synthesizing ATP (adenosine triphosphate) from ADP (adenosine diphosphate) and inorganic phosphate using light energy during photosynthesis

cyclic light reaction

a process where light energy is converted into chemical energy in the form of ATP, occurs in Photosystem I (PSI), which absorbs light energy and excites electrons which are then transferred through an electron transport chain, creating a proton gradient to drive ATP synthesis

non-cyclic light reaction

a process in the thylakoid membrane of chloroplasts, electrons are transferred from photosystem II (PSII) to photosystem I (PSI), splitting water molecules to release oxygen and hydrogen ions, which reduce NADP to NADPH, the electrons are not recycled and are instead used to generate ATP and NADPH

RUBISCO = ribulose-1,5-biphosphate carboxylase

a enzyme found in the chloroplasts that facilitates the reaction between carbon dioxide (CO2) and ribulose-1,5-bisphosphate (RuBP) to produce 3-phosphoglycerate (3-PGA), a key intermediate in the calvin cycle

C3 plants

first organic product of carbon fixation is a three-carbon compound, 3-phosphoglycerate

C4 plants

preface the calvin cycle with an alternate mode of carbon fixation to produce a four-carbon compound as first product

CAM photosynthesis

a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions, allowing plants to photosynthesize during the day and only exchanging gases at night