Cell Membranes, Energy, and Thermodynamics

Flashcards on Cell Membranes, Energy, and Thermodynamics

Plasma Membrane

Composed of phospholipids arranged in a bilayer with globular proteins inserted within. Functions include a flexible matrix and permeability barrier.

Fluid Mosaic Model

Describes the plasma membrane as a mosaic of proteins floating in or on the fluid lipid bilayer.

Phospholipids

Has hydrocarbon tails that are nonpolar and hydrophobic on the bilayer's inside, and polar, hydrophilic head groups on the outside.

Transmembrane Proteins

Integral membrane proteins within the phospholipid layer.

Hydrophobic

Water-fearing; Describes the nonpolar hydrocarbon tails of phospholipids.

Hydrophilic

Water-loving; Describes the polar head groups of phospholipids.

Membrane Protein Functions

Include transporters, enzymes, cell-surface receptors, cell-surface identity markers, cell-to-cell adhesion proteins, and attachment to the cytoskeleton.

Thermodynamics

The study of energy changes related to chemistry. Governed by laws stating energy cannot be created or destroyed, only changed.

First Law of Thermodynamics

Energy cannot be created or destroyed; it can only be changed from one form to another. The total amount of energy in the universe remains constant.

Kinetic Energy

Energy of motion (moving objects).

Potential Energy

Stored energy (objects that are not moving).

Calorie

The heat required to raise the temperature of 1 gram of water by 1 degree Celsius.

Photosynthesis

Process where organisms convert small molecules into complex molecules (sugars) using light energy.

Redox Reaction

Chemical reactions where electrons are transferred from one atom or molecule to another.

Oxidation

The loss of an electron by an atom or molecule.

Reduction

The gain of an electron by an atom or molecule.

Second Law of Thermodynamics

Energy cannot be transferred 100% from one form to another. Some energy is always unavailable, increasing entropy.

Entropy

A measure of energy unavailable to do work; increases as energy transformations occur.

Gibbs Free Energy (G)

The free energy available to perform work; calculated as G = H - TS.

Enthalpy (H)

Energy stored in a molecule's chemical bonds.

Endergonic Reaction

A reaction that requires the input of energy and is not spontaneous (positive ΔG).

Exergonic Reaction

A reaction that is spontaneous and releases energy (negative ΔG).

Activation Energy

The minimum amount of energy required for reactants to start a reaction.

ATP (Adenosine Triphosphate)

The primary energy currency used by cells. Energy is stored and released in its bonds.

ATP Hydrolysis

The breakdown of ATP into ADP + Pi + energy, which is an exergonic reaction.

ATP Composition

Ribose (five-carbon sugar), adenine (nitrogen-containing compound), and a chain of three phosphates.

ADP (Adenosine Diphosphate)

ATP with two phosphates; lower energy than ATP.

AMP (Adenosine Monophosphate)

ATP with one phosphate; lowest energy form.

ATP Cycle

ATP drives endergonic reactions. It is not suitable for long-term energy storage; fats and carbohydrates are better for that purpose.