Cellular Classification & Organelles: A Look at the Endomembrane System Biology 111 Holyoke Walsh

Prokaryotes vs Eukaryotes The basic structural & functional unit of every organism is one or two types of cells – pro or eukaryote. Prokaryotes are archaebacteria & eubacteria Eukaryoes include protists, fungi, animals and plants.

Typical Eukaryotic Cell

Typical Prokaryotic Cell

Commonalities…of all cells!! Plasma Membrane Cytosol Chromosomes Ribosomes

So What is the Difference? The location of their DNA; Prokaryote = nucleoid region Eukaryote = nucleus Disparity in structural complexity

Prokaryote vs. Eukaryote

Prokaryote or Eukaryote??

Eukaryotes In addition to the plasma membrane at its outer surface, a eukaryotic cell has extensive & elaborately arranged internal membranes, which divide the cell into compartments. These provide different local environments that facilitate specific metabolic functions, so incompatible processes can go on simultaneously in a single cell The plasma and organelle membranes participate directly in the cell’s metabolism b/c many enzymes are built right into the membranes themselves.

Eukaryotes…genetic info… Two cellular components involved with the genetic control of the cell are the NUCLEUS & the RIBOSOMES

Cell Membranes..in general Phospholipid bilayer Embedded proteins Each type of membrane has a unique composition of lipids and proteins suited to that membrane’s specific function Ex: enzymes embedded in the mitochondrial organelle function in cellular respiration

NUCLEUS

Ribosomes Made of some RNA (genetic info) and Protein Main function is to carry out protein synthesis.

Ribosomes cont… Cells that have high rates of protein synthesis have particularly high rates of ribosomes Located in the cytoplasm/ER (structurally identical) Free ribosomes – function within the cytosol (ie. enzymes that catalyze reactions) Attached ribosomes – generally destined for insertion into organelles membranes or for export (cells that secrete enzymes)

Locate the Ribosomes…

Endomembrane System Many of the different membranes of the eukaryotic cell are part of this system which carry out a variety of tasks in the cell. Ie. synthesis of proteins, metabolism and movement of lipids, & detoxification of poisons The membranes of this system are related either through physical continuity or by the transfer of membrane segments as tiny vesicles (sacs made of membrane) This system includes: nuclear envelope, the endoplasmic reticulum, golgi apparatus, lysosomes, various vacuoles, and the plasma membrane

Endomembrane System

Endoplasmic Reticulum Extensive network accounting for more than half the total membrane in eukaryotic cells Consists of a network of membranous tubules and sacs called cisternae The ER membrane separates the internal compartment of the ER, called the ER lumen (cavity) or cisternal space, from the cytosol. The ER membrane is continuous with the nuclear membrane

ER cont… Two types of ER: smooth and rough 1.Smooth ER – lacks ribosomes and involved in diverse metabolic processes such as lipid synthesis, metabolism of carbohydrates, and detoxification of drugs and poisons 2.Rough ER – has ribosomes and is involved in protein synthesis

Golgi Apparatus – Shipping & Receiving Center

Lysosomes Membranous sac of enzymes that an animal cell uses to digest macromolecules. Lysosomal enzymes work best in an acidic environment found in lysosomes. If a lysosome breaks or leaks the enzymes are not very active b/c cytosol has a neutral pH Lysosomes carry out intracellular digestion in a variety of ways. ie. amoebas use phagocytosis…food vacuole fuses with lysosome and enzymes will then digest the food. FYI: humans use phagocytosis: WBC called macrophage that engulfs and destroys bacteria & other invaders.

Vacuoles Types: 1.Food vacuoles – formed by phagocytosis 2.Contractile vaculoes – pump excess water out of the cell 3.In plants & Fungi – Central vacuole: stores food, nutrients, water and waste.

Work time… HWK: Additional Organelles?? – Students will fill out their table using the student textbook to create a study sheet