Cellular Energetics Test

metabolism

the sum of all chemical reactions in an organism

metabolic pathways

series of chemical reactions that build or break down molecules

catabolic

Pathways that release energy by breaking down complex molecules (e.g., Cellular Respiration).

anabolic

 Pathways that consume energy to build complex molecules (e.g., Photosynthesis).

energy

The capacity to cause change or do work.

thermodynamics

The study of energy transformations.

1st law of thermodynamics

Energy cannot be created or destroyed, only transferred or transformed.

2nd law of thermodynamics

Every energy transfer increases the entropy (disorder) of the universe.

spontaneous process

A process that occurs without an overall input of energy; increases entropy.

entropy

A measure of molecular disorder or randomness.

free energy

The portion of a system's energy that can perform work.

activation energy

The initial energy needed to start a chemical reaction.

substrate

The specific reactant an enzyme acts on.

reactants

starting materials that get consumed

products

new substances that are formed

active site

The specific region of the enzyme where the substrate binds.

exergonic

A spontaneous reaction that releases free energy

endergonic

A non-spontaneous reaction that absorbs free energy

atp

The cell's primary energy shuttle.

energy coupling

Using an exergonic process to drive an endergonic one.

phosphorylated intermediate

 A molecule with a phosphate group covalently bound to it, making it more reactive.

phosphate

three in atp

adenine

nitrogenous base in atp

hydrolysis

The process of breaking bonds (like in ATP) by adding water.

autotrophic

Organisms that "feed themselves"; producers of the biosphere.

chloroplasts

Organelles where photosynthesis occurs.

stroma

region of the chloroplast around the thylakoid; where the Calvin cycle takes place

thylakoids

Sac-like photosynthetic membranes; site of light reactions.

photosynthesis equation

6co2 + 6 h2o= c6h1206+6o2

light reactions

series of chemical reactions during photosynthesis in the thylakoid where the energy of sunlight and water are used to synthesize NADPH and ATP

NADPH

an electron carrier in many biochemical reactions; the reducing agent used in the Calvin cycle during photosynthesis; made by light reactions

calvin cycle

process where carbon dioxide is reduced to synthesize carbohydrates, with ATP and NADPH as the energy source; carbon fixation, reduction, and regeneration

visible light

The segment of the electromagnetic spectrum ($380\text{--}750\text{ nm}$) that drives photosynthesis.

wavelengths

he distance between crests of electromagnetic waves; determines color and energy.

chlorophyll a

The main photosynthetic pigment.

photon

light energy.

photosystem

A reaction-center complex surrounded by light-harvesting complexes.

reaction center complex

core part of photosystems where light energy is converted into chemical energy by exciting an electron, starting the ETC

light harvesting complexes

antenna part of photosystems that collects light energy through pigments that are excited, and transfers it to the reaction center

primary electron acceptor

the first molecule to receive an energized electron from the reaction-center chlorophyll, starting the ETC

Photosystem II and 1

protein-pigment complexes that absorb light energy to drive redox reactions to drive the photosynthetic electron transport chain; PSII - splits water molecules to replace lost electrons, releasing oxygen, protons, and electrons; PSI - re-energizes electrons and transfers them to make NADPH.

Best at absorbing wavelength.

linear electron flow

the process in photosynthesis where electrons move in a one-way path from water to NADP+, creating ATP and NADPH; light energy excites electrons in PSII and move through the ETC, creating a proton gradient that powers ATP synthase; electrons are re-energized at PSI before being used to reduce NADP+ to NADPH

C3 plants

Fix carbon into a three-carbon compound; risk photorespiration in heat.

C4 plants

Minimize photorespiration by fixing co2 into four-carbon compounds in mesophyll cells.

CAM plants

Open stomata at night, incorporating co2 into organic acids for use during the day.

photorespiration

A wasteful pathway where O2 is consumed instead of co2

G3P

The direct sugar product of the Calvin cycle.

fermentation

metabolic pathways that produce ATP from the partial oxidation of organic molecules without oxidative phosphorylation or an electron acceptor, such as oxygen

cellular respiration

series of chemical reactions where organic molecules like glucose are oxidized to carbon dioxide, converting the energy stored in organic molecules to ATP; glycolysis, pyruvate oxidation, Kreb's Cycle, electron transport chain

aerobic respiration

Consumes organic molecules and o2 to yield ATP.

redox reactions

Chemical reactions involving the transfer of electrons.

oxidation

a chemical reaction in which a molecule loses electrons and energy; water is converted to oxygen, partially losing electrons

reduction

a chemical reaction in which a molecule gains electrons and energy; carbon dioxide is converted to glucose, partially gaining electrons

NAD+

A coenzyme that cycles between oxidized (NAD+) and reduced (NADH) states as an electron carrier.

electron transport chain

a series of four protein complexes in the inner mitochondrial membrane; facilitates a series of redox reactions, transferring electrons from NADH and FADH2 to oxygen, creating a proton gradient that drives ATP synthesis via oxidative phosphorylation

glycolysis

breakdown of glucose to pyruvate; the first stage of cellular respiration, producing 2 net ATP and NADH

citric acid cycle

third stage of cellular respiration, in which acetyl-CoA is broken down and carbon dioxide is released; NADH, FADH2, and ATP are made

oxidative phosphorylation

set of chemical reactions that occurs by passing electrons along an electron transport chain to a final electron acceptor, oxygen, pumping protons across a membrane, and using the proton electrochemical gradient to drive the synthesis of ATP

chemiosmosis

the movement of ions from high to low concentration across a selectively permeable membrane; powers the synthesis of ATP

pyruvate

3 carbon molecule

acetyl CoA

two-carbon molecule formed in pyruvate oxidation from pyruvate, releasing CO2 and making NADH; then used in Kreb's Cycle

CoA

vitamin B5-derived cofactor responsible for fatty acid synthesis/oxidation and the citric acid cycle

proton motive force/gradient

electrochemical difference in hydrogen ion concentration across a membrane (inner mitochondrial membrane); stores potential energy, which drives ATP synthesis through ATP synthase

ATP synthase

enzyme that couples the movement of H+ protons through the enzyme the synthesis of ATP

alcoholic/ethanol fermentation

form of anaerobic respiration where microorganisms like yeast convert sugars into ethanol and carbon dioxide, creating a small amount of ATP

lactic acid fermentation

form of anaerobic respiration where glucose is converted into ATP and the byproduct lactic acid, is regenerated into NAD+ for glycolysis to continue; occurs in muscle cells

versatility of catabolism

breaks down diverse complex molecules—carbohydrates, lipids, proteins, and nucleic acids—into smaller, simpler units to generate ATP energy and raw materials for anabolism

mitochondria

organelles where cellular respiration takes place in eukaryotic cells, oxidizing chemical compounds such as sugars to carbon dioxide and transferring their chemical energy to ATP

mitochondrial matrix

space enclosed by the inner membrane of the mitochondria

inner mitochondrial membrane

phospholipid bilayer inside mitochondria that separates the matrix from the intermembrane space; folded into cristae to maximize surface area for the ETC and ATP production

outer mitochondrial membrane

outer phospholipid bilayer that encloses the mitochondrion, separating it from the cytosol

intermembrane space

space between the inner and outer mitochondrial membrane

cristae

folds

active and passive transport in both photosynthesis and cellular respiration.

Active and passive transport are essential for both photosynthesis and cellular respiration, primarily by managing proton (

H+cap H raised to the positive power

𝐻+

) gradients across membranes to drive ATP synthesis and facilitating gas exchange. Active transport creates energy-intensive proton gradients, while passive transport allows protons to flow back down their gradient, powering ATP generation, alongside passive diffusion of gases

enzyme

a protein that functions as a catalyst to accelerate the rate of a chemical reaction

NADH, Fadh2

electron carrier that transports high-energy electrons from organic molecules like glucose and donates them to the electron transport chain to generate ATP; reduced form of nicotinamide adenine dinucleotide

pyruvate oxidation

process that converts 3 carbon pyruvate molecules into 2 carbon acetyl coa molecule, releases co2 and makes nadh