Biology: Cells

Cell portion

Cell Theory

All living things are composed of cells; cells are the basic units of structure and function; new cells arise from preexisting cells.

Prokaryotes

Single-celled organisms lacking membrane-bound organelles; DNA is in the cytoplasm; example:Bacteria.

Eukaryotes

Organisms with internal membrane-bound organelles; can be single-celled or multicellular; examples:Protists, Fungi, Plants, Animals.

Unicellular

Organisms consisting of a single cell; examples:E. coli, Yeast, Amoeba.

Multicellular

Organisms made up of multiple specialized cells; examples:Mold, Red Maple, Coral, Humans.

Cytoplasm

Gel-like substance within the cell, containing organelles and nutrients; involved in cellular processes.

Cell Wall

Rigid outer layer in plant and fungal cells; provides structure and protection; composed of cellulose or chitin.

Cell Membrane

Phospholipid bilayer that regulates the movement of substances in and out of the cell; provides shape and support.

Nucleus

Membrane-bound organelle containing genetic material; controls cellular activities and processes like transcription.

Nucleolus

Structure within the nucleus responsible for synthesizing ribosomal RNA and assembling ribosomes.

Centrosome

Organelle containing centrioles; plays a role in cell division and the formation of cilia and flagella.

Microtubules

Hollow structures that provide shape and movement to the cell; part of the cytoskeleton.

Microfilaments

Protein fibers that provide mechanical support and assist in cell movement; part of the cytoskeleton.

Rough Endoplasmic Reticulum

Network of membranes with ribosomes; involved in protein synthesis and modification.

Smooth Endoplasmic Reticulum

Membrane network without ribosomes; involved in lipid synthesis and metabolism.

Ribosomes

Sites of protein synthesis; consist of two subunits; found free in the cytoplasm or attached to the rough ER.

Golgi Apparatus

Organelle that modifies, sorts, and packages proteins and lipids for transport within or outside the cell.

Vesicles

Membrane-bound sacs that transport materials within the cell or to the cell membrane for exocytosis.

Lysosomes

Organelles containing digestive enzymes; involved in breaking down waste materials and cellular debris.

Peroxisomes

Organelles that contain enzymes for metabolic processes, including the breakdown of hydrogen peroxide.

Mitochondria

Double-membraned organelles responsible for ATP production through cellular respiration.

Chloroplast

Double-membraned organelle in plant cells; site of photosynthesis, containing chlorophyll.

Vacuole

Membrane-bound structure for storage of nutrients and waste; helps maintain turgor pressure in plant cells.

Cilia

Hair-like projections that aid in movement and sensing the environment; contain a 9+2 arrangement of microtubules.

Flagella

Long, whip-like structures that enable movement in some cells; structure differs between prokaryotes and eukaryotes.

Microvilli

Finger-like projections that increase surface area for absorption and secretion; contain actin filaments.