Cells part 2

Phospholipid

A molecule that makes up the cell membrane, consisting of a hydrophilic head and two hydrophobic tails.

Amphipathic

A molecule that has both hydrophilic and hydrophobic regions.

Bilayer

A structure formed by two layers of phospholipids arranged tail-to-tail.

Hydrophobic

Repelling water; non-polar molecules that do not dissolve in water.

Hydrophilic

Attracted to water; polar molecules that dissolve readily in water.

Permeability

The ability of a membrane to allow substances to pass through.

Semi-permeable

A characteristic of membranes that allows certain substances to pass while blocking others.

Simple diffusion

The passive movement of molecules from an area of higher concentration to one of lower concentration.

Facilitated diffusion

The process of passive transport of molecules across a membrane via specific proteins.

Active transport

The movement of molecules across a membrane against their concentration gradient, requiring energy.

Fluid-mosaic model

A model that describes the structure of cell membranes, depicting them as flexible and composed of various proteins embedded in a bilayer.

Peripheral protein

A protein that is attached to one side of the membrane and does not penetrate it.

Integral protein

A protein that is embedded within the membrane and spans across the bilayer.

Glycoprotein

A protein that has carbohydrate chains attached, playing a role in cell recognition.

Cholesterol

A lipid that helps to stabilize the structure of the membrane.

Glycolipid

A lipid with a carbohydrate attached, involved in cell recognition and signaling.

Channel protein

A protein that allows specific ions or water to pass through the membrane.

Osmosis

The diffusion of water across a semi-permeable membrane.

Aquaporin

A channel protein that facilitates the movement of water across cell membranes.

Hypertonic

A solution with a higher concentration of solutes compared to another solution.

Hypotonic

A solution with a lower concentration of solutes compared to another solution.

Isotonic

A solution with the same concentration of solutes as another solution, resulting in no net movement of water.

Turgor pressure

The pressure exerted by water inside the central vacuole of a plant cell against the cell wall.

Plasmolysis

The process in which cells lose water in a hypertonic environment, causing the cell membrane to pull away from the cell wall.

Contractile vacuoles

Organelles in freshwater unicellular organisms that help to expel excess water and maintain osmotic balance.

Dynamic equilibrium

A state in which the concentration of solutes in a solution remains relatively stable.

Passive transport

The movement of substances across a cell membrane without the need for energy input.

Selective permeability

A characteristic of cell membranes that allows them to regulate which molecules can enter or exit the cell.