Unit 3: Cell Energy Vocab (AP Biology)

metabolism

total of all chemical reactions done in an organism to store or release energy (the number of molecules built vs. the amount of molecules broken down- ex. digestion or building muscle)

metabolic pathway

begins with a specific molecule, ends with a product, and is carried out by enzymes (2 types)

catabolic pathway

releases energy by breaking down molecules into simpler compounds (ex. cellular respiration and breakdown of glucose to release energy in humans)

anabolic pathway

uses energy to build molecules (ex. synthesis of protein from amino acids to be used in muscles)

thermodynamics

study of energy transformations

First Law of Thermodynamics

energy cannot be created or destroyed, just transformed

Second Law of Thermodynamics

Every energy transfer increases the entropy of the universe and makes things unstable (energy will seek to get back into a stable form or equilibrium).

entropy

disorder

free energy

energy available to do work

DeltaG

change in free energy (negative- energy released, more stable; positive- energy stored, less stable)

spontaneous change

releasing free energy (can be harnessed to do work)

endergonic reaction

absorbs free energy from surroundings and is nonspontaneous (anabolic)

exergonic reaction

proceeds with a net release of free energy and is spontaneous (catabolic)

energy coupling

use of an exergonic process to drive an endergonic one (cell energy coupling is mostly done by ATP)

ATP

the cell's energy molecule; made of ribose (a sugar), adenine (a nitrogenous base), and three phosphate groups

phosphorylation

process where a released phosphate combines with a reactant to make it unstable (endergonic; makes recipient molecule unstable with extra stored energy and able to do work)

dephosphorylation

process where a phosphate releases itself from a substance and creates ATP (exergonic)

catalyst

chemical agent that speed up a reaction (can be reused)

enzyme

catalytic protein (ex. hydrolysis of sucrose by sucrase)

activation energy

initial energy needed to start a chemical reaction (can be supplied in form of heat from surroundings)

substrate

reactant that an enzyme acts on

enzyme-substrate complex

enzyme and substrate together

active site

part of the enzyme the substrate binds to

induced fit

"lock and key" matching shape of enzyme and substrate

cofactor

nonprotein enzyme helper

coenzyme

organic cofactor (ex. vitamins)

competitive inhibitor

binds to the active site of an enzyme, competing with the substrate

noncompetitive inhibitor

binds to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

allosteric regulation

occurs when regulatory molecule binds to a protein at one site and affects the protein's function at another site

inhibitors

make enzymes inactive (ex. toxins, poisons, pesticides, and antibiotics)

activators

make enzymes active

cooperativity

form of allosteric regulation where presence of substrate makes enzyme active

feedback inhibition

end product of a metabolic pathway shuts down the pathway (ex. thermostat)

autotroph

makes its own energy (usually from the sun; ex. plants)

heterotroph

gets energy from other organisms (ex. animals, fungi)

photosynthesis

using energy from the sun to create glucose (plants use glucose to make ATP and sugars; reactants: carbon dioxide, sunlight, and water; products: oxygen and glucose; redox process where H2O is oxidized and CO2 is reduced)

mesophyll

interior tissue of leaves

thylakoids

help capture sunlight for plants (arranged in grana)

granum

a stack of thylakoids

stroma

region of fluid filled space outside the thylakoids

chlorophyll

pigment in chloroplasts (transmits green light, absorbs all others)

pigments

substances that absorbs visible light (different types absorb different light)

spectrophotometer

measures a pigment's ability to absorb various wavelengths of light (sends light through pigments and measures amount of light transmitted)

absorption spectrum

graph plotting pigment's light absorption vs. wavelength

action spectrum

tells you which wavelength of light actually drives photosynthesis the best

reduction

gain electrons

oxidation

lose electrons

light reaction

requires sunlight (in thylakoid, happens in light, water is oxidized, and produces NADPH and ATP)

photosystem

pigment molecule attached to proteins (light harvesting complex) that funnels light energy into a reaction center where electrons are transferred (light comes in electrons come out)

photosystem II

light first enters here (discovered second)

P680

special chlorophyll molecule in photosystem II that takes electrons from the hydrogen that came from the split water (it really likes electrons :D)

primary electron acceptor

molecule in the reaction center that receives electrons from P680

linear flow

primary electron acceptor sends electrons down the electron transport chain to photosystem I

photosystem I

electrons enter here from electron transport chain (ETC; discovered first)

ATP synthase

enzyme that makes ATP as hydrogens pass through

P700

receives electrons coming from ETC (electrons are not coming from water this time)

cyclic flow

primary acceptor can send electrons back to top of ETC so they can come down again and make more ATP

NADP+

electron carrier that can receive electrons from the primary acceptor in photosystem I

NADPH

reduced from of NADP+

calvin cycle

light-independent reaction (in stroma, happens in both light and dark, CO2 is reduced, uses ATP and NADPH from light reaction, produces glucose; 3 phases: Carbon Fixation, Reduction, and Regeneration)

carbon fixation

incorporating carbon dioxide

RuBP

5 carbon sugar that awaits CO2 in Calvin and Citric Acid/Krebs cycles

rubisco

enzyme that adds one CO2 to RuBP to make a 6 carbon sugar (happens three times)

G3P

3 carbon molecule formed during the Reduction phase of the Calvin Cycle and during the Krebs Cycle

regeneration

replacing RuBP

C3 plants

initial fixation of CO2, via rubisco, forms a three-carbon compound (close stomata on hot dry days, which conserves H2O but limits intake of CO2)

C4 plants

counteract hot days by fixing CO2 into four-carbon compounds in mesophyll cells (resuires enzyme PEP carboxylase)

PEP carboxylase

can fix CO2 even when there isn't much of it

bundle-sheath cells

cells in C4 plants where four-carbon compounds release CO2 that is then used in the Calvin Cycle

CAM plants

use CAM to fix CO2 into four-carbon molecules (open their stomata at night and close them during the day to do so)

cellular respiration

process by which the mitochondria break down glucose to make ATP (produces 36-38 ATPs; opposite of photosynthesis)

glycolysis

stage 1 of cellular respiration (anaerobic; occurs in cytoplasm; produces 2 net ATP molecules, 2 NADH molecules, and 2 Pyruvic Acid molecules; releases hydrogen)

anaerobic

no oxygen needed

citric acid cycle/krebs cycle

stage 2 of cellular respiration (aerobic; occurs in mitochondrial matrix; acetyl-CoA is formed; CO2 is released; 8 NADHs are made; 2 FADH2s (electron carrier) are made; yields 2 molecules of ATP; hydrogen is released; happens twice because there are two Pyruvates which create two acetyl-CoAs)

acetyl-CoA

3 carbon Pyruvate is converted into this 2 carbon molecule that is a coenzyme that is essential in the Citric Acid Cycle

electron transport chain (ETC)

transfers electrons from photosystem II to photosystem I in photosynthesis; stage 3 of cellular respiration (aerobic, occurs in inner membrane of mitochondria and in thylakoid membrane of chloroplasts; NADH (yields about 3 ATPs) delivers electrons to first protein in ETC; FADH2 (yields about 2 ATPs) delivers electrons to second protein in ETC; 32-34 ATPs produced)

oxidative phosphorylation

phosphorylation that requires oxygen (occurs in ETC)

aerobic

requires oxygen

fermentation

anaerobic ATP production that occurs after glycolysis when oxygen is not available (not efficient, 2 ATPs, 2 types)

lactic acid fermentation

produces 2 ATPs and lactic acid (lactate)

lactic acid

a product of lactic acid fermentation; stored in muscles and turned into pyruvate (ex. when exercising)

alcoholic fermentation

produces 2 ATPs, CO2, and ethyl alcohol (ex. yeast)

ethyl alchohol

product of alcoholic fermentation