Biology 101: Cell Structure

Cell

The basic structural and functional unit of all living organisms, capable of carrying out life processes independently.

Plasma Membrane

A selectively permeable phospholipid bilayer that surrounds the cell, regulating what enters and exits.

Nucleus

A membrane-bound organelle that contains the cell's DNA and controls gene expression and cell division.

Mitochondria

Double-membrane organelles that generate ATP through cellular respiration, often called the powerhouses of the cell.

Ribosome

Small organelles made of rRNA and protein that synthesize proteins by translating mRNA sequences.

Endoplasmic Reticulum (Rough)

A network of membrane-enclosed tubules studded with ribosomes that synthesizes and processes proteins for secretion or membrane insertion.

Endoplasmic Reticulum (Smooth)

A network of membrane-enclosed tubules lacking ribosomes that synthesizes lipids, detoxifies drugs, and stores calcium ions.

Golgi Apparatus

A stack of flattened membrane sacs that modifies, sorts, and packages proteins and lipids for transport or secretion.

Lysosome

A membrane-bound organelle containing hydrolytic enzymes that digest worn-out organelles, food particles, and invading pathogens.

Cytoplasm

The gel-like substance filling the interior of the cell between the plasma membrane and the nucleus, where organelles are suspended.