Honors Biology: Cell Membrane Structure, Function, and Transport Mechanisms

Nonpolar molecules

Can pass directly through the phospholipid bilayer.

Polar molecules

Cannot cross the phospholipid bilayer without transport proteins.

Ions

Cannot cross the phospholipid bilayer.

Components of an animal cell membrane

Phospholipid bilayer, cholesterol, protein.

Transmembrane proteins

Proteins that are embedded in the cell membrane and can cross it entirely.

Transmembrane protein

A protein that crosses the cell membrane entirely.

Glycoprotein

Protein that has a carbohydrate attached to it.

Glycolipid

A lipid that has a carbohydrate attached to it.

Functions of membrane proteins

Transporting substances across the membrane, functioning as enzymes, transferring signals, and cell recognition.

Parts of a phospholipid molecule

Hydrophilic head and hydrophobic tails.

Function of cholesterol in membranes

Keeps the cell membrane's fluidity balanced.

Selective permeability

Let's some things in & not others.

Passive transport

Doesn't use energy to control what molecules enter & leave.

Active transport

Uses energy to control what molecules enter & leave.

Cell membrane

Controlling which molecules enter & leave the cell and separating cell from surroundings.

Peripheral proteins

Proteins that are attached to the inner surface of the cell membrane.

Characteristics of passive transport

Doesn't require energy, moves substances down their gradient from high to low concentration, and needs diffusion, osmosis, or facilitated diffusion.

Concentration gradient

The difference in concentration of a substance from one area to another.

Dynamic equilibrium

Reached when the concentration of a substance on both sides of the cell membrane is the same.

Aquaporins

Proteins that help water cross the cell membrane.

Osmosis

The facilitated diffusion of water across a selectively permeable membrane.

Types of passive transport

Facilitated diffusion, diffusion, osmosis.

Characteristics of active transport

Moves things from low concentration to high concentration, requires ATP energy, and uses a transport protein.

Sodium-potassium pump

Main type of active transport in animals that moves 3 Na out and 2 K in.

Electrochemical gradient

The difference in ion concentration and charge relative to the other side of the cell.

Exocytosis

Moving big molecules out of a cell.

Endocytosis

Moving big molecules into the cell.

Phagocytosis

Moving big solid molecules into the cell.

Pinocytosis

Moving big amounts of liquid into the cell.

Hypertonic solution

A solution where the solute concentration outside the cell is greater than inside.

Isotonic solution

A solution where the solute concentration is the same inside and outside the cell.

Hypotonic solution

A solution where the solute concentration outside the cell is less than inside.

Ideal environments for cells

Animal cells thrive in isotonic environments, while plant cells thrive in hypotonic environments.

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