Chloroplasts

Chloroplast

double membraned organelle found in plants that performs photosynthesis; converts light energy into chemical energy (glucose)

Chloroplast envelope

the double membrane that surrounds the chloroplast controlling the movement of materials in and out of the organelle; functions like the nuclear envelope

Outer membrane

outer layer of the choloroplast envelope, permeable to small molecules + ions

Inner membrane

inner layer of the chloroplast envelope, selectively permeable, regulates transport of molecules into the stroma and houses protein involved in metabolic processes

Stroma

fluid filled space inside the chloroplast enclosed by the inner membrane; where Calvin cycle (light independent rxns)takes place; chloroplast DNA, ribosomes, and enzymes are located here

Thylakoid membranes

membrane system inside chloroplasts that form flattened sacs called thylakoids which contains chlorophyll; where light dependent reactions occur

Granum (grana)

stack(s) of thylakoid membranes within the chloroplast; increase surface area for light dependent reactions

Light reactions

convert light energy into ATP and NADPH, produce oxygen by splitting water; first stage of photosynthesis occurring in the thylakoid membranes

Sunlight

energy source for photosynthesis; visible and UV light energy emitted by the sun

Photons

packets of light energy that are absorbed by chlorophyll during photosynthesis to excite e⁻

Chlorophyll

green pigment that captures light energy for photosynthesis

ATP

cell’s main energy currency; releases a phosphate group to become ADP (releases power)

NADPH

electron carrier produced during light reactions; provides electrons and H for Calvin cycle

Calvin cycle

light independent stage of photosynthesis in stroma; uses ATP and NADPH to turn CO2 into glucose or other sugars

Carbon dioxide

gas taken in by plants during photosynthesis; used in calvin cycle to make glucose

Ribulose 1,5 biphosphate (RuBP)

5 carbon sugar in calvin cycle that reacts with CO2, starting the carbon fixation process; catalyzed by rubisco

Rubisco

an enzyme in the Calvin cycle that catalyzes the fixation of CO2 to RuBP (the most abundant enzyme on Earth)

Glyceraldehyde 3 phosphate (G3P)

3 carbon sugar produced in the Calvin cycle; used to form glucose and other carbohydrates

Photorespiration

process where rubisco uses O2 instead of CO2 leading to a 2 carbon compound instead of sugar; reduces photosynthetic efficiency

Epidermis

outermost layer of cells in plants and animals; protect against water loss, pathogens, and regulates gas exchange

Stomata

small pores on the plant epidermis that regulate gas exchange and water vapor release through opening and closing

Vascular bundle

strand of xylem and phloem tissues which transports water, nutrients, and sugars throughout the plant

Mesophyll cells

plant leaf cells located between the epidermal layers (palisade and spongy); specialize in photosynthesis containing many chloroplasts

C3 Photosynthesis

most common photosynthetic pathways when CO2 is fixed directly by RuBisCO into G3P

C4 Photosynthesis

photosynthetic pathway where CO2 is fixed into a 4 carbon compound to reduce photorespiration in hot + dry environments

Bundle sheath cells

specialized cells surrounding the vascular bundle in C4 plants to help reduce photorespiration; release CO2 for the Calvin cycle

Antenna complex

group of proteins + pigments in the thylakoid membrane that capture + transfer light energy to the rxn center; starts process of turning light into usable energy

Z scheme photosynthesis

stepwise flow of electrons through photosystem II + photosystem I, resembling a Z shape on an energy diagram; produces ATP + NADPH

Photosystem II

first protein pigment complex in light rxns; captures light energy to split water molecules, releasing oxygen + exciting electrons for the ETC

Plastoquinone

small, mobile electron carrier in thylakoid membrane that transfers electrons from photosystem II to the cytochrome b6f complex during light rxns

Cytochrome b6f complex

protein complex in thylakoid membrane that accepts electrons from plastoquinone + transfers them to plastocyanain; creates a proton gradient for ATP synthesis

Plastocyanin

small copper containing molecule in the thylakoid lumen that transfers electrons from the cytochrome b6f complex to photosystem I

Photosystem I

protein pigment complex that re excites electrons to reduce NAPH+ to NADPH

Ferredoxin NADP+ reductase

enzyme that uses electrons from ferredoxin to reduce NADP+ into NADPH at the end of the ETC

Fatty acid synthesis

process of making fatty acids from smaller molecules like acetyl CoA using ATP and NADPH; stores energy in the form of fats

Amino acid biogenesis

process by which cells build amino acids from simpler molecules, often using intermediates from glycolysis or the citric acid cycle; essential for making proteins