Chapter 5 Cells: Membrane Transport and Energy

A complete set of vocabulary flashcards covering cell membrane structure, selective permeability, types of transport (passive, active, vesicular), thermodynamic laws, and the mechanics of metabolism and enzymes.

Extracellular fluid (ECF)

The fluid that surrounds the outside of a cell.

Cytosol

The fluid that fills the inside of a cell.

Plasma membrane

The boundary that separates the extracellular fluid from the cytosol and performs functions such as physical isolation and regulation of exchange.

Phospholipid bilayer

The structural framework of the plasma membrane consisting of hydrophilic head groups and a hydrophobic core.

Cholesterol

A lipid component of the cell membrane that makes the membrane stiffer.

Transport proteins

Proteins that make a channel through the phospholipids to allow substances to pass in and out of the cell.

Receptor proteins

Proteins that allow for cell signaling by acting as receptors for messages.

Recognition proteins

Proteins with attached sugars that allow cells to identify or recognize each other.

Glycoproteins

Proteins with sugars attached that allow cells to recognize each other.

Selective permeability

The property of a cell membrane that allows some substances to pass through while preventing others.

Diffusion

The net movement of particles from a region of higher to lower concentration down a concentration gradient.

Concentration gradient

A difference between regions of high and low concentration.

Equilibrium

A state where particles are uniformly distributed with an equal concentration on both sides of a membrane.

Passive Diffusion

Movement across a membrane that is unaided by proteins, requires no energy, and moves from high to low concentration; examples include $O_2$, $CO_2$, and alcohol.

Osmosis

The diffusion of water ($H_2O$) through a membrane from areas of high water concentration to areas of lower water concentration.

Solution

A mixture consisting of a solute and a solvent (typically water).

Tonicity

The description of the effects of osmotic solutions on cells.

Isotonic solution

A solution where there is no net gain or loss of water by the cell.

Hypotonic solution

A solution that causes a net gain of water into the cell, which may lead to the cell lysing (bursting).

Hypertonic solution

A solution that causes a net water flow out of the cell, resulting in the cell shriveling.

Turgid

The normal, firm state of a plant cell when placed in a hypotonic solution.

Flaccid

The state of a plant cell when it wilts in an isotonic solution.

Facilitated diffusion

A form of passive transport that uses a transport protein to provide a pathway for large or hydrophilic molecules without requiring energy.

Active transport

The movement of molecules against their concentration gradient using protein channels and $ATP$ energy.

Vesicular transport

The movement of large materials into or out of cells within membranous vesicles.

Endocytosis

The process of moving materials into the cell via vesicles.

Pinocytosis

A type of endocytosis involving the movement of fluid into the cell.

Phagocytosis

A type of endocytosis involving the movement of food or solid particles into the cell.

Exocytosis

The process of ejecting materials from the cell.

Bioenergetics

The study of how energy is processed by living organisms.

Energy

The capacity to cause change.

Potential Energy

Stored energy, such as chemical energy found in food, coal, or wood.

Kinetic Energy

Energy in motion or released energy, such as light ($photons$), electricity ($electrons$), or heat.

1st Law of Thermodynamics

The Law of the Conservation of Energy, stating that energy can neither be created nor destroyed, and the total amount of energy in the universe is constant.

2nd Law of Thermodynamics

The Law of Entropy, stating that when energy is transformed, there is always a loss of usable energy, typically in the form of heat.

Entropy

A measure of disorder in a system.

Producers

Photosynthetic organisms, such as plants and algae, that convert light energy into chemical energy.

Consumers

Organisms that feed on plants or other animals.

Decomposers

Organisms like fungi and bacteria that break down waste products and the remains of dead organisms.

Metabolism

The totality of all biochemical reactions that occur within a cell.

Catabolism

The part of metabolism involving breakdown (degradation) reactions that release energy, often involving hydrolysis and oxidation.

Anabolism

The part of metabolism involving build-up (synthetic) reactions that require energy and involve dehydration synthesis and reduction.

Oxidation (OIL)

The loss of electrons ($e^-$) or hydrogen ions ($H^+$) during a chemical process.

Reduction (RIG)

The gain of electrons ($e^-$) or hydrogen ions ($H^+$) during a chemical process.

Enzymes

Proteins that act as biological catalysts to speed up chemical reactions by lowering the activation energy barrier.

Activation energy

The energy barrier that must be overcome to start a chemical reaction.

Substrate

The specific molecule that an enzyme is designed to recognize and interact with.

Active site

The specific 3D area on an enzyme where the substrate binds.

Induced fit

The process where an enzyme changes shape to hug the substrate as they lock together.

Competitive inhibition

A form of enzyme inhibition where an inhibitor binds directly to the active site, preventing the substrate from binding.

Non-competitive inhibition

A form of enzyme inhibition where an inhibitor binds elsewhere on the enzyme, disrupting its function regardless of substrate binding.

ATP (Adenosine triphosphate)

The primary chemical energy molecule used by cells for work, consisting of adenosine and three phosphate groups.

ADP (Adenosine diphosphate)

The molecule that remains after $ATP$ is broken down and one phosphate group is removed to release energy.