All About Cells A cell with its cytoskeleton by fluorescence microscopy

The Cell Theory 1. Cells are the fundamental unit of life. A cell is the “simplest collection of matter that can live”. 2. All current cells come from pre-existing cells. 3. Cells organize the metabolism of life and carry the genetic “blueprints” of life from one generation to the next.

Prokaryotic versus Eukaryotic Cells Prokaryotic cells: Nucleoid contains DNA, not a membrane-bounded nucleus No membrane-bounded organelles Eukaryotic cells: Has a membrane-bounded nucleus which contains the DNA Has membrane-bounded organelles Both are full of cytoplasm Both have a plasma membrane surrounding the cell

Prokaryotic Cell Cytoplasm with ribosomes plasma membrane Often have projections called pili to increase surface area Flagella for locomotion

Prokaryotic Structure Cytoplasm contains DNA (nucleoid) and ribosomes, as well as various chemicals Surrounded by plasma membrane May have pili to increase surface area and “stickiness” May have flagella for movement

Prokaryotic Structure Cell wall (a rigid structure important in classifying bacteria) made of a protein-sugar molecule Some bacteria also have a capsule, a protective outer coating

Size difference between eukaryotic and prokaryotic cells Bacteria on the human epithelial cell from the mouth of a human Photo by Dr. Gary Kaiser

Overview of a Eukaryotic Cell (characterized by membrane bound organelles) nucleus mitochondria endomembrane system In plants, add a cellulose cell wall and a really big vacuole full of water plasma membrane

Nucleolus (where ribosomal RNA is made) condensed DNA Nucleus (surrounded by the nuclear envelope)

The Nucleus nuclear pores

nuclear pores The Nucleus Connection between outer nuclear membrane and the endoplasmic reticulum inner membrane of nuclear envelope nuclear pore outer membrane of nuclear envelope

nuclear pores The Nucleus Attached to the outer surface of the nuclear envelope and the endoplasmic reticulum are ribosomes ribosomes

Ribosomes are the sites of protein synthesis in the cell Ribosomes are composed of a type of RNA (ribosomal RNA or rRNA) and proteins – made in the nucleolus of the nucleus Ribosomes are the sites of protein synthesis in the cell Free ribosomes vs. Bound ribosomes

The Endomembrane System A continuous internal membrane system that includes the: Outer membrane of the nuclear envelope Rough endoplasmic reticulum Smooth endoplasmic reticulum Transport vesicles between ER and Golgi Golgi apparatus Transport vesicles between Golgi and plasma membrane Lysosomes Plasma membrane

The Rough and Smooth Endoplasmic Reticulum Smooth ER Transitional ER Transport vesicle destined for Golgi apparatus Rough ER

Functions of smooth ER and rough ER Produce certain lipids (e.g., steroids) Detoxifies drugs (has enzymes in its membranes that do this) Rough ER With bound ribosomes, produces proteins destined for secretion from cell or packaging in specialized organelles (e.g., lysosomes) Makes new membranes (phospholipids and proteins are made and put together by the rough ER)

Golgi apparatus – a “refinery” or “processing plant” Golgi apparatus – a “refinery” or “processing plant”. Proteins are processed and refined as they pass through on their way to final destination Transport vesicle from transitional ER cisternae (flattened membranous sacs) Transport vesicle destined for plasma membrane, or to become a lysosome

Golgi are especially used to “refine” glycoproteins – proteins plus carbohydrate chains Glycoprotein produced in ER Refined as it passes through Golgi Distributed in transport vesicles

Nematode Golgi apparatus trans face – ‘shipping’ cis face – ‘receiving’ Flow of transport vesicles and proteins

The flow of membrane through the endomembrane system Tracking an insulin molecule

1. Insulin is produced by ribosomes on the rough ER 2. Enters the cisternae of the rough ER and moves inside the cisternae to the transitional ER

3. Packaged into transport vesicles and transferred to cis face of the Golgi apparatus 4. Transport vesicles fuse to form first cisternae of Golgi apparatus

5. Processed in Golgi apparatus as cisternae move through stack 6. Packaged into transport vesicles at the trans face of the Golgi apparatus and transported to plasma membrane

The entire process once again!

One additional organelle produced by the Golgi apparatus is the lysosome

Lysosomes Digestive organelles – sacs of digestive enzymes Function at acidic pH inside lysosome

Lysosomes – digestive organelles – for intracellular digestion Digesting food particles that are brought into cells Digesting damaged mitochondria and other organelles