Eukaryotic and prokaryotic cell structures and functions

Eukaryotic Cells

Larger (10–100 µm) Contain membrane-bound organelles DNA is linear, associated with histones, contained in a nucleus Ribosomes are 80SExamples: animal, plant, fungi, and protist cellsProkaryotic CellsSmaller (0.1–5 µm)No membrane-bound organellesDNA is circular and located in the nucleoid regionMay contain plasmids (small circles of DNA)Ribosomes are 70S Cell walls contain peptidoglycan (murein) Examples: bacteria and archaea

Nucleus

Contains DNA organized into chromosomes

Surrounded by nuclear envelope with pores

Site of transcription (mRNA production)

Nucleolus

Produces ribosomal RNA (rRNA)

Assembles ribosomes

Mitochondria

Site of aerobic respiration

Produces ATP

Double membrane with folded cristae and matrix

Contains its own DNA and ribosomes

Ribosomes (80S)

Site of protein synthesis

Can be free in cytoplasm or attached to rough ER

Rough Endoplasmic Reticulum (RER)

Covered in ribosomes

Modifies and transports proteins

Smooth Endoplasmic Reticulum (SER)

Synthesises and transports lipids

Golgi Apparatus

Modifies, sorts, and packages proteins and lipids

Forms vesicles and lysosomes

Lysosomes

Contain digestive enzymes

Break down old organelles and pathogens

Plasma Membrane

Phospholipid bilayer

Controls movement of substances in and out

Centrioles

Involved in spindle formation during cell division

Chloroplasts (plants only)

Site of photosynthesis

Contain chlorophyll

Have thylakoids, grana, and stroma

Contain their own DNA and ribosomes

Cell Wall (plants only)

Made of cellulose

Supports and protects the cell

Nucleoid

Region containing circular DNA molecule

Not membrane-bound

Plasmids

Small circular DNA molecules

Often carry antibiotic resistance genes

70S Ribosomes

Smaller than eukaryotic ribosomes

Site of protein synthesis

Cell Wall

Made of peptidoglycan (murein)

Maintains cell shape and protects from osmotic lysis

Capsule (sometimes present)

Protective outer layer

Helps evade host immune system

Flagellum (sometimes present)

Enables movement

Different structure from eukaryotic flagella

Mesosomes (controversial)

Infoldings of membrane seen in some images

Now thought to be artefacts of preparation