BIOL 3100: CELL AND MOLECULAR BIOLOGY - PHOTOTROPIC ENERGY METABOLISM: CHLOROPLAST FUNCTION

Flashcards covering key concepts from the lecture on Phototrophic Energy Metabolism and Chloroplast Function, focusing on photosynthesis, chloroplast structure, light-dependent reactions, the Calvin cycle, and adaptations like C4 and CAM pathways.

__ is the conversion of light energy to chemical energy and its subsequent use in synthesizing organic molecules.

Photosynthesis

Organisms that convert solar energy to chemical energy in the form of ATP and the reduced coenzyme NADPH are called __.

Phototrophs

Organisms that acquire energy from sunlight but depend on organic sources of reduced carbon are known as __.

Photoheterotrophs

Plants, algae, and most photosynthetic bacteria are __ because they use solar energy to synthesize energy-rich organic molecules from simple inorganic starting materials.

Photoautotrophs

Light energy captured by chlorophyll and converted to ATP and NADPH occurs during __ reactions.

Energy transduction

ATP synthesis driven by energy derived from the sun is called __.

Photophosphorylation

The reactions, commonly known as the Calvin cycle, where carbon atoms from carbon dioxide are 'fixed' to form carbohydrates, are called __.

Carbon assimilation reactions

The energy transduction reactions of photosynthesis occur in the chloroplast __.

thylakoids

The carbon assimilation reactions, including the Calvin cycle and starch biosynthesis, occur in the chloroplast __.

stroma

The organelle responsible for most events of photosynthesis in eukaryotic phototrophs is the __.

chloroplast

Newly differentiated plant cells have smaller organelles called __ that can develop into various kinds of plastids.

proplastids

The inner membrane of a chloroplast encloses the __, a gel-like matrix rich in enzymes for carbon, nitrogen, and sulfur reduction and assimilation.

stroma

The outer membrane of a chloroplast contains transmembrane proteins called __ that are freely permeable to most small organic molecules and ions.

porins

Flat, saclike structures suspended in the chloroplast stroma, usually arranged in stacks, are called __.

thylakoids

Stacks of thylakoids are called __.

grana

A stream of discrete particles, each carrying a quantum of energy, is called __.

photons

The event where a photon's energy is transferred to an electron, energizing it from its ground state to an excited state, is called __.

photoexcitation

__ is the primary energy transduction pigment that channels solar energy into the biosphere.

Chlorophyll

The skeleton of a chlorophyll molecule consists of a central __ ring and a strongly hydrophobic phytol side chain.

porphyrin

Most photosynthetic organisms contain __ pigments, which absorb photons not captured by chlorophyll and transfer their energy.

accessory

Two types of accessory pigments are carotenoids and __.

phycobilins

Functional units composed of chlorophyll molecules, accessory pigments, and associated proteins within thylakoid membranes are called __.

photosystems

Photosystem I (PSI) has an absorption maximum of __ nm.

700

Photosystem II (PSII) has an absorption maximum of __ nm.

680

Most pigments of a photosystem serve as light-gathering __ pigments, which collect light energy and pass it to neighboring pigments.

antenna

Each photosystem is generally associated with a __, which also collects light energy but does not contain a reaction center.

light-harvesting complex (LHC)

The process of transporting excited electrons from chlorophyll to NADP+, forming NADPH, is known as __.

photoreduction

The flow of electrons through the __ complex is coupled to unidirectional proton pumping across the thylakoid membrane.

cytochrome b6/f

The ATP synthase found in chloroplasts is designated the __ complex.

CF0CF1

The __ complex contains the P680 reaction center chlorophyll, where water is oxidized and split.

Photosystem II

The __ complex transfers electrons from plastoquinol to plastocyanin, linking PSII with PSI.

Cytochrome b6/f

The __ complex contains the P700 reaction center chlorophyll and donates electrons to ferredoxin.

Photosystem I

__ is an enzyme on the stromal side of the thylakoid membrane that catalyzes the transfer of electrons to NADP+, forming NADPH.

Ferredoxin-NADP+ reductase

__ is a proton channel and ATP synthase that couples the exergonic flow of protons from the thylakoid lumen to the stroma with the synthesis of ATP.

ATP synthase complex (CF0CF1)

__ electron flow through PSI enables oxygenic phototrophs to increase the ratio of ATP/NADPH production when extra ATP is needed.

Cyclic

The __ cycle is confined to the chloroplast stroma and converts CO2 into carbohydrates.

Calvin

The first stage of the Calvin cycle involves the carboxylation (fixation) of ribulose-1,5-bisphosphate to generate two molecules of __.

3-phosphoglycerate

In C3 plants, during one turn of the Calvin cycle, three CO2 molecules are fixed and one molecule of __ is produced.

glyceraldehyde-3-phosphate (G3P)

The most abundant protein in the chloroplast inner membrane is a __ translocator, which exchanges triose phosphates for inorganic phosphate.

triose phosphate/phosphate

Sucrose synthesis occurs in the __, while starch synthesis occurs only in the chloroplast stroma.

cytosol

Rubisco, besides acting as a carboxylase, can also function as an __ by catalyzing the addition of molecular oxygen to ribulose-1,5-bisphosphate.

oxygenase

The wasteful diversion of material from carbon assimilation that produces phosphoglycolate due to rubisco's oxygenase activity is channeled into the __ pathway.

glycolate

The glycolate pathway is also referred to as __ due to its light-dependent uptake of oxygen and evolution of carbon dioxide.

photorespiration

The glycolate pathway involves specific peroxisomes called __.

leaf peroxisomes

In C4 plants like maize, a short carboxylation/decarboxylation pathway known as the __ cycle is used to isolate rubisco.

Hatch-Slack

The immediate product of carbon dioxide fixation by the Hatch-Slack cycle is the four-carbon organic acid __.

oxaloacetate

In C4 plants, the Hatch-Slack cycle occurs in __ cells, while the Calvin cycle is confined to bundle sheath cells.

mesophyll

Crassulacean acid metabolism (CAM) plants segregate carboxylation and decarboxylation reactions by __ rather than by space.

time

CAM plants generally open their __ only at night to conserve water.

stomata

A process called __ in CAM plants allows them to survive droughts by recycling carbon dioxide between photosynthesis and respiration with virtually no water loss.

CAM idling