Module 2: The Plasma Membrane

Vocabulary flashcards covering atomic bonds, membrane structure, polarity, passive transport mechanisms, and active transport processes from BIOL 1441 Module 2.

Plasma membrane

A structure present in every cell that functions to divide the inside of the cell from its environment and is selectively permeable.

Cytosol

The intracellular fluid found inside the cell.

Extracellular fluid

The fluid found in the environment outside of the cell.

Selective permeability

A property of a membrane meaning only certain molecules can pass straight through it based on its structure.

Atom

A particle of matter that consists of a nucleus surrounded by one or more negatively charged electrons.

Chemical bond

A lasting attraction between atoms or ions that enables the formation of molecules.

Covalent bond

A strong chemical bond involving shared electrons.

Hydrogen bond

A weak bond formed between polar molecules.

Polar molecule

A molecule that has areas of partial positive charge and partial negative charge due to unequal sharing of electrons.

Nonpolar molecule

A molecule that shares electrons equally and does not have positive and negative ends.

Hydrophilic

Meaning water loving; describes polar molecules that are attracted to one another and to other polar molecules.

Hydrophobic

Meaning water fearing; describes nonpolar molecules that repel water and other polar molecules.

Phospholipid bilayer

The structure of the plasma membrane consisting of two rows of phospholipids with hydrophilic head groups and hydrophobic fatty acid tails.

Solvent

The liquid part of a solution, which in the human body is water.

Solute

The dissolved substances within a solution.

Concentration gradient

The difference in solute concentration between two solutions.

Passive transport

Any movement of molecules across the plasma membrane that moves down a concentration gradient and does not require energy.

Simple diffusion

A form of passive transport where hydrophobic and nonpolar molecules move straight across the plasma membrane.

Facilitated diffusion

A form of passive transport where hydrophilic, polar, and large molecules move across the plasma membrane using a transport protein.

Channel protein

A transport protein used in facilitated diffusion that is open on both sides of the membrane at the same time.

Carrier protein

A transport protein that changes its shape to move specific substances across the plasma membrane.

Osmosis

The passive movement of water down its concentration gradient straight across the plasma membrane or through a transport protein.

Hypertonic solution

A solution that has a higher concentration of solutes and a lower concentration of water compared to cytosol.

Isotonic solution

A solution that has the same concentration of solutes and water as cytosol.

Hypotonic solution

A solution that has a lower concentration of solutes and a higher concentration of water compared to cytosol.

Active transport

The movement of a molecule up or against its concentration gradient across a membrane, requiring energy and a transport protein.

Primary active transport

A type of active transport that directly uses ATP as an energy source to move molecules against their concentration gradient.

Sodium-potassium pump

A primary active transport mechanism that uses ATP to pump $Na^+$ out of the cell and $K^+$ into the cell to polarize the cell membrane.

Secondary active transport

A type of active transport where the movement of one molecule down its concentration gradient powers the movement of another molecule against its concentration gradient.

Sodium-glucose cotransporter

A secondary active transport mechanism where $Na^+$ moving down its concentration gradient pulls glucose into the cell against its concentration gradient.