AP Bio Unit 3

catabolic pathways

Reactions that release energy by breaking down complex molecules into simpler ones. An example is cellular respiration.

anabolic pathways

Reactions that consume energy by building complex molecules from simpler ones. An example is protein synthesis from amino acids.

first law of thermodynamics

Also known as the law of conservation of energy, this law states that energy cannot be created nor destroyed.

free energy

This is energy available to do work at any given time.

spontaneous reaction

A reaction with a negative net change in free energy. These reactions only require an energy input in the beginning (activation energy), but after that they are self-sustaining.

nonspontaneous reaction

A reaction with a positive net change in free energy (similar to charging). These reactions require a constant energy input throughout the entire reaction. If this energy input stops at any time, the whole reaction stops as well.

exergonic reaction

A reaction that has a net release of energy. It is a spontaneous reaction.

endergonic reaction

A reaction that has a net gain/absorbance of energy. It is a nonspontaneous reaction.

Adenosine triphosphate (ATP)

The universal energy “currency” of the body. It stores energy and when it breaks apart, it releases energy. It powers everything inside the body.

phosphorylated

The addition of a phosphate group to any molecule. An example of this is the changing of ADP into ATP.

enzyme

A tertiary catalytic protein that speeds up reactions.

activation energy

The initial energy needed to start a chemical reaction. Often, this is in the form of heat from surroundings.

substrate

The reactant that an enzyme reacts on (to speed up the reaction).

enzyme-substrate complex

The entire structure of a substrate currently inside an active site of an enzyme.

active site

The region of an enzyme where the substrate bonds.

induced fit

The active site of an enzyme tightens around a substrate to enhance its catalytic ability.

competitive inhibitors

Molecules that bond to the active site, preventing a substrate from bonding with the active site and inhibiting the reaction from taking place.

noncompetitive inhibitors

Molecules that bond to the allosteric site of an enzyme, changing the shape of the active site, making it less effective.

allosteric regulation

When a molecule inhibits or stimulates an enzyme’s activity by bonding to the allosteric site of an enzyme.

allosteric site

Anywhere on an enzyme that is not the active site.

Fermentation

A type of reaction that occurs when there is no oxygen available. This reaction occurs in place of aerobic respiration, and for most organisms, is only temporary. This reaction is rapidly repeated glycolysis, with an added step at the end. That step is the conversion of NADH back into NAD+ so that the reaction can repeat again. It yields much less energy per glucose, and is not sustainable.

anaerobic respiration

A type of reaction that occurs when there is no oxygen available. This reaction mostly occurs in prokaryotic organisms that are adapted to survive environments without oxygen. This is a sustainable reaction that is able to produce almost as much ATP as aerobic respiration. It uses other molecules, such as sulfate, as the final electron acceptor rather than oxygen.

redox reactions

Chemical reactions that transfer electrons.

electron transport chain

A part of oxidative phosphorylation where NADH and FADH2 power the active transport of hydrogen ions using their electrons. These electrons are then transported between proteins.

glycolysis

The first step of cellular respiration. In this step, glucose is broken down into two pyruvates in the cytosol outside the mitochondria.

citric acid cycle

This step of cellular respiration occurs in the matrix of the mitochondria. In this step, Acetyl COA is used to power the synthesis of NADH, FADH2, and ATP.

oxidative phosphorylation

The final step of cellular respiration. It is in two parts, the electron transport chain and chemiosmosis. In this step, the active transport of hydrogen ions across the cristae leads to mass power generation from their eventual diffusion back into the matrix.

ATP synthase

An enzyme used in chemiosmosis to capture the kinetic energy generated by the mass diffusion of hydrogen ions across the cristae from the intercellular space to the matrix.

Chemiosmosis

The second part of oxidative phosphorylation. In this step, ATP synthase captures the kinetic energy generated by the mass diffusion of hydrogen ions across the cristae. This energy turns a rotor, and is used to synthesize 32-34 ATP.

alcohol fermentation

A type of fermentation that occurs in plants and produces ethanol.

lactic acid fermentation

A type of fermentation that occurs in animals and produces lactate.

Cristae

The foldy inner membrane of the mitochondria.

Matrix

The cytosol-filled space inside the cristae of the mitochondria.

Autotrophs

Organisms that perform photosynthesis. They create their own glucose using the energy they harness from the sun.

Heterotrophs

Organisms that obtain glucose from other organisms as opposed to creating their own.

Chlorophyll

A pigment found within photosystems that absorbs light and powers photosynthesis.

Stomata

Pores in the bottom of a leaf that are used for gas exchange.

Stroma

The fluid filled matrix within a chloroplast.

Thylakoids

Green disks found inside chloroplasts.

light reactions

The first stage of photosynthesis in which light and water are converted into chemical energy inside the thylakoid.

calvin cycle

The second stage of photosynthesis in which energy produced in the light reactions and carbon dioxide from the air are used to produce glucose inside the stroma.

carbon fixation

The process of attaching carbon to a molecule.

Rubisco

An enzyme that performs carbon fixation on RuBP during the Calvin Cycle.

C3 plants

Plants that do not have any special evolution to prevent photorespiration.

Photorespiration

Rubisco will oxidize RuBP instead of performing carbon fixation in the presence of oxygen. This is detrimental to the plant, making gas exchange essential.

C4 plants

Plants that have anatomical separation and carbon pumps to prevent photorespiration.

CAM plants

Plants that open and their stomata depending on time of day to balance photorespiration prevention and dehydration.