Bio Ch. 5 - The Working Cell

Biologists use the ____ model to describe a membrane’s structure

Fluid Mosaic Model

The Plasma Membrane exhibits ___

Selective Permeability

What does ‘Permeable’ (verb) mean?

Allowing liquids or gases to pass through it.

Membranes are fluid mosaics of ___ and ___ with many functions

Lipids and Proteins

What is an enzyme?

a protein that speeds up a chemical reaction in a cell (a catalyst)

Solute vs Solvent vs Solution

Solute = The thing being dissolved (ex.🧂)

Solvent = The liquid doing the dissolving (💧)

Solution = The mixture you get when the ‘solute’ dissolves in the ‘solvent’ (🥤)

Transport Proteins

Allow specific ions or molecules to enter or exit the cell

Attachment Proteins

• Attach to the extracellular matrix and cytoskeleton

• Help support the membrane

• Can coordinate external and internal changes

Receptor Proteins

• Signaling molecules bind to receptor proteins

• Receptor proteins relay the message by activating other molecules inside the cell

Glycoproteins

• Serve as ID tags

• May be recognized by membrane proteins of other cells

Phospholipids spontaneously self-assemble into ___

Simple membranes

The formation of _____ collections of molecules was a critical step in the evolution of the first cells

membrane-enclosed

Diffusion

The tendency of particles to spread out evenly in an available space. (ex. like perfume sprayed in a room)

ATP

(Adenosine Triphosphate) is the primary energy currency of all living cells

Passive Transport

Diffusion across a cell membrane that does NOT require energy (ATP).

Osmosis

The diffusion of water across a selectively permeable membrane from where there is MORE water to where there is LESS water to make the water concentration equal!

___ balance between cells and their surroundings is crucial to organisms

Water

Tonicity

•The ability of a surrounding solution to cause a cell to lose or gain water (or in other words, it affects the movement of water into or out of a cell).

•Hypertonic, Hypotonic, and Isotonic describe the tonicity of the solution outside the cell.

Hypertonic Solution

•Cells shrink in a Hypertonic Solution. (Hyper = higher)

•There’s more solute outside → therefore less water outside → water leaves the cell.

Hypotonic Solution

•Cells swell in a Hypotonic Solution.

(Hypo = lower)

•There’s less solute outside → therefore more water outside → water enters the cell.

Isotonic Solution

Iso = same

•The solute concentration is the same inside and outside → water moves in both directions at an equal rate → no net water movement.

•In isotonic solutions, animal cells are normal, but plant cells are flaccid (has lost turgor pressure, meaning the cell membrane no longer presses tightly against the cell wall).

Active Transport

In Active Transport, a cell must expand energy to move a solute against its concentration gradient.