Chapter 4: The Energy of Life - Flashcards

Vocabulary flashcards covering energy forms, thermodynamics, metabolic reactions, enzyme function, and membrane transport mechanisms based on Chapter 4 of the Biology: Concepts and Investigations textbook.

Energy

The ability to do work—to move matter.

Kinetic energy

The energy of motion or movement.

Potential energy

Stored energy that is available to do work.

First law of thermodynamics

The principle stating that energy is never created or destroyed, only converted from one form to another.

Heat energy

Disordered energy lost at each step of energy transformation that cannot be used or converted back to a useful form.

Entropy

A measure of disorder or the randomness of the universe.

Second law of thermodynamics

The principle that the entropy of the universe is increasing because heat energy is constantly being lost to the universe.

Metabolism

The sum of all chemical reactions that occur within cells.

Endergonic reactions

Chemical reactions that form bonds to build molecules and require an input of energy.

Exergonic reactions

Chemical reactions that break bonds to release energy stored in those bonds.

Oxidation

The loss of electrons from an atom or molecule, which releases energy.

Reduction

The gain of electrons by an atom or molecule, which requires energy.

Electron transport chain

A series of membrane proteins participating in sequential, linked oxidation-reduction reactions.

Adenosine triphosphate (ATP)

A nucleotide that temporarily stores energy and is the form of energy that all cells can use to power chemical reactions.

Cellular respiration

A series of chemical reactions that release energy from sugar, producing ATP from ADP.

ATP hydrolysis

The process of removing the endmost phosphate group from ATP by adding water, which releases potential energy.

Enzyme

A protein that acts as a catalyst to speed up a chemical reaction without being consumed.

Substrate

The specific molecule that an enzyme acts on by binding to its active site.

Active site

The region on an enzyme where substrate molecules bind and the chemical reaction occurs.

Activation energy

The energy required to start a chemical reaction.

Cofactors

Partners, such as metal ions or vitamins, that help catalyze reactions and increase enzyme activity.

Negative feedback

A control mechanism where the product of a reaction inhibits the activity of an enzyme earlier in the pathway to slow production.

Positive feedback

A control mechanism where the product of a reaction stimulates its own production by enhancing enzyme activity.

Competitive inhibitor

A molecule that binds to an enzyme's active site, blocking the substrate from binding.

Noncompetitive inhibitor

A molecule that binds to an enzyme outside of its active site, altering the enzyme's shape so the substrate cannot bind.

Concentration gradient

A directional difference in the concentration of a solute between neighboring regions.

Passive transport

The movement of substances down a concentration gradient without the requirement of energy.

Simple diffusion

A form of passive transport where small, nonpolar molecules move down their concentration gradient across a biological membrane.

Osmosis

The simple diffusion of water across a selectively permeable membrane down its concentration gradient.

Isotonic solution

A condition where solute concentrations are equal inside and outside the cell, resulting in water moving equally in both directions.

Hypotonic solution

A solution with a lower solute concentration than the cell's interior, causing water to rush into the cell.

Hypertonic solution

A solution with a higher solute concentration than the cell's interior, causing water to rush out of the cell.

Turgor pressure

The pressure of water against the cell wall in plant cells; its loss due to hypertonic surroundings causes wilting.

Facilitated diffusion

Passive transport that requires membrane proteins to move polar molecules or ions across a membrane down their concentration gradient.

Active transport

The movement of substances against their concentration gradient using membrane proteins (pumps) and cellular energy.

Sodium-potassium pump

An active transport protein that moves $Na^{+}$ and $K^{+}$ ions across the membranes of neuron and muscle cells.

Endocytosis

An energy-requiring process where the cell membrane buds inward to form a vesicle, engulfing fluids or large molecules into the cell.

Exocytosis

An energy-requiring process where cells use vesicles to secrete large polar molecules, such as proteins, out of the cell.