AP bio unit 3 cellular energetics

Kreb’s Cycle

A series of reactions in the mitochondria that break down acetyl CoA to produce ATP, NADH, FADH₂, and carbon dioxide

Aerobic

A process that requires oxygen to occur

Anaerobic

A process that does not require oxygen to occur

Oxidative phosphorylation 

The process in cellular respiration where ATP is produced using energy from the electron transport chain and a proton gradient

Alcohol fermentation

A molecule that carries acetyl groups into the Krebs cycle for energy production during cellular respiration

Acetyl CoA

A 2-carbon molecule that enters the Krebs cycle to produce energy (ATP, NADH, FADH₂).

Cellular Respiration

The process cells use to break down glucose and other molecules to produce ATP for energy

Redox reactions

Chemical reactions where electrons are transferred between molecules, involving both oxidation and reduction

ATP Synthase

An enzyme that makes ATP by using energy from a flow of protons across a membrane

substrate-level phosphorylation

A way to make ATP by transferring a phosphate group from a molecule to ADP during metabolism

lactic acid fermentation

A process where cells convert pyruvate into lactic acid to produce ATP without using oxygen

oxidation

A chemical reaction where a molecule loses electrons or hydrogen

glycolysis

The first step of cellular respiration where glucose is broken down into pyruvate, producing a small amount of ATP and NADH

catabolism

The set of metabolic processes that break down molecules to release energy

reduction 

A chemical reaction where a molecule gains electrons or hydrogen

chemiosmosis

The process where protons move across a membrane through ATP synthase, producing ATP from a proton gradient

NAD+/NADH

NAD⁺ is an empty electron carrier, and NADH is the full form that carries electrons and energy for cellular processes

proton motive force

The energy stored in a proton gradient across a membrane that drives ATP synthesis

proton gradient

A difference in proton (H⁺) concentration across a membrane that stores energy used to make ATP

photosynthesis

The process by which plants, algae, and some bacteria use sunlight, carbon dioxide, and water to make glucose and oxygen

non-cyclic photophosphorylation

A process in photosynthesis where electrons flow from water through photosystems II and I to produce ATP, NADPH, and oxygen

autotrophs

Organisms that make their own food from sunlight or chemicals, such as plants and some bacteria

cyclic electron flow

A process in photosynthesis where electrons cycle back to photosystem I to produce ATP without making NADPH or oxygen

heterotrophs

Organisms that cannot make their own food and get energy by eating other organisms

cyclic photophosphorylation

A process in photosynthesis where electrons from photosystem I are recycled to produce ATP without making NADPH or oxygen

chlorophyll

The green pigment in plants that absorbs light energy for photosynthesis

absorption spectrum

A graph showing the wavelengths of light a pigment absorbs most effectively

mesophyll cells

Leaf cells where most photosynthesis occurs, containing many chloroplasts to capture light energy

chlorophyll a

The main pigment in plants that absorbs light energy to drive photosynthesis

rubisco (RUBP carboxylase)

The main enzyme in the Calvin cycle that adds carbon dioxide to RuBP, beginning the process of building sugars

stomata

Tiny openings on plant leaves and stems that allow gas exchange, letting carbon dioxide in and oxygen and water vapor out

action spectrum

A graph that shows how much a plant uses different wavelengths of light for photosynthesis

C3 plants

Plants that fix carbon dioxide directly through the Calvin cycle, forming a 3-carbon compound first; they do best in cooler, wetter environments

stroma

The fluid-filled space inside the chloroplast where the Calvin cycle takes place

cholorphyll b 

A pigment in the chloroplast that helps absorb additional light and passes that energy to chlorophyll a for photosynthesis

photorespiration

A process where the enzyme Rubisco binds to oxygen instead of carbon dioxide, wasting energy and reducing sugar production in the plant

light reactions

The first stage of photosynthesis where light energy is used to make ATP and NADPH and oxygen is released from splitting water

accessory pigments

Pigments in the chloroplast that help absorb extra light wavelengths and pass that energy to chlorophyll for photosynthesis

c4 plants

Plants that first fix carbon into a 4-carbon compound, allowing them to photosynthesize efficiently in hot, sunny environments while reducing photorespiration.

calvin cycle

A series of reactions in the stroma of the chloroplast that uses ATP and NADPH to turn carbon dioxide into sugars.

bundle sheath cells

Tightly packed cells around leaf veins in C₄ plants where the Calvin cycle happens, helping the plant avoid photorespiration.

NADP+/NADPH

NADP⁺ is the empty electron carrier, and NADPH is the energy-filled carrier used in photosynthesis.

reaction center chlorophyll

the special chlorophyll molecule in a photosystem that actually sends out excited electrons when it absorbs light, starting the steps of photosynthesis

photophosphorylation

the process where light energy is used to make ATP during photosynthesis

carbon fixation

the process where plants take carbon dioxide from the air and turn it into usable organic molecules, like sugars, during photosynthesis

PEP carboxylase

an enzyme that captures CO₂ and turns it into a 4-carbon compound, helping certain plants (like C₄ and CAM plants) start photosynthesis more efficiently.

photosystem I

the part of the chloroplast that uses light to make energy-rich molecules (like NADPH) for photosynthesis.

photosystem II

the part of the chloroplast that uses light to split water and start photosynthesis.

CAM plants

are plants that take in CO₂ at night and do photosynthesis during the day to save water.

thylakoid membrane

the membrane in chloroplasts that captures light for photosynthesis.