Chapter 3A

Flashcards for reviewing cell biology concepts, including cell theory, plasma membrane structure, membrane transport, and cell junctions.

Cell theory

The structural and functional unit of life; the organism's function depends on the combined activities of all of its cells; continuity of life has a cellular basis.

Plasma membrane

Flexible outer boundary; plays a dynamic role in cellular activity by controlling what enters and leaves the cell.

Cytoplasm

Intracellular fluid containing organelles.

Nucleus

DNA-containing control center.

Extracellular fluids

Interstitial fluid, blood plasma, and cerebrospinal fluid.

Cellular secretions

Saliva and mucus.

Extracellular matrix

Substance that acts as glue to hold cells together.

Plasma Membrane

Acts as an active barrier separating intracellular fluid (ICF) from extracellular fluid (ECF).

Fluid mosaic

Membrane lipids form a flexible lipid bilayer; specialized membrane proteins float through the fluid membrane.

Glycocalyx

Surface sugars form this.

Phospholipids

Phosphate heads (polar, hydrophilic) and fatty acid tails (nonpolar, hydrophobic).

Glycolipids

Lipids with sugar groups on the outer membrane surface.

Cholesterol

Increases membrane stability.

Integral proteins

Firmly inserted into the membrane; most are transmembrane proteins.

Peripheral proteins

Loosely attached to integral proteins.

Glycocalyx

Sugars (carbohydrates) sticking out of the cell surface that function as specific biological markers for cell-to-cell recognition.

Tight junctions

Integral proteins on adjacent cells fuse to form an impermeable junction that encircles the whole cell.

Desmosomes

Rivet-like cell junction formed when linker proteins (cadherins) of neighboring cells interlock.

Gap junctions

Transmembrane proteins (connexons) form tunnels that allow small molecules to pass from cell to cell.

Passive transport

No energy is required to cross the membrane.

Active transport

Energy (ATP) is required to cross the membrane.

Diffusion

Natural movement of molecules from areas of high concentration to areas of low concentration.

Simple diffusion

Nonpolar lipid-soluble substances diffuse directly through the phospholipid bilayer.

Facilitated diffusion

Hydrophobic molecules are transported passively down their concentration gradient by carrier or channel proteins.

Osmosis

Movement of solvent (such as water) across a selectively permeable membrane.

Osmolarity

Measure of the concentration of the total number of solute particles in a solvent.

Hydrostatic pressure

Outward pressure exerted on the cell side of the membrane caused by increases in the volume of the cell due to osmosis.

Osmotic pressure

Inward pressure due to the tendency of water to be pulled into a cell with higher osmolarities.

Tonicity

Ability of a solution to change the shape or tone of cells by altering the cells' internal water volume.

Isotonic solution

Solution with the same osmolarity as inside the cell, so volume remains unchanged.

Hypertonic solution

Solution with higher osmolarity than inside the cell, so water flows out of the cell, resulting in cell shrinking (crenation).

Hypotonic solution

Solution with lower osmolarity than inside the cell, so water flows into the cell, resulting in cell swelling and potentially bursting (lysing).