Cellular Uptake Major ways that cells acquire large samples from environment Phagocytosis-”cell-eating” or engulfment  Amoebae or macrophages  Cell produces pseudopod to surround large object Pinocytosis-”cell drinking”  Vesicle forms and brings in liquid Endocytosis-receptor mediated  A specific receptor-target interaction triggers  Forms coated pit and vesicle

Vesicle Nomenclature Vesicles have specific names that are linked to their origin  Phagocytosis=phagosome  Pinocytosis=pinosome or uncoated vesicle  Endocytosis=endocytic vesicle or coated vesicle

Nucleus Command center of cell Where DNA as chromosomes is located Membrane bound Site of transcription and RNA modification and maturation Normally only one per cell unless cell is actively dividing

Fig Nucleolus Nucleus Rough ER Nuclear lamina (TEM) Close-up of nuclear envelope 1 µm 0.25 µm Ribosome Pore complex Nuclear pore Outer membrane Inner membrane Nuclear envelope: Chromatin Surface of nuclear envelope Pore complexes (TEM)

Nuclear membrane Double membrane with perinuclear space in between Very important for cell function  Allow separation of mRNA from translational machinery Allows modification and maturation of mRNA before it is translated into proteins Membrane is covered with octameric pores that allow mRNA out and nuclear proteins in Ribosomes cover outer membrane and translate mRNA into proteins

Nucleolus Very dense core of nucleus Easy to see on EM Responsible for synthesis of ribosomes Essential for cell function

DNA Structure In the nucleus, DNA exists as highly compact structures known as chromosomes Many levels of compaction  DNA is wound around Histone proteins like rope around a barrel  Histones associate and bring the complexes closer together  Looping and supercoiling compact DNA even further DNA would be larger than cell if not compacted

Ribosomes Synthesize protein via translation  Use mRNA as template Comprises two subunits-60S and 40S Very complex structures made up of many small proteins and rRNA molecules

Fig Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit Diagram of a ribosome TEM showing ER and ribosomes 0.5 µm

Ribosome Location Ribosomes perform one function but are found at several locations  On outer surface of nuclear membrane  On Rough Endoplasmic Reticulum  Free in cytosol

Endoplasmic Reticulm Complex mass of membranes with cytoplasm of cell Extension of nuclear membranes and perinuclear space Two varieties  Rough-coated with ribosomes  Smooth-no ribosomes Complex structure with:  Tubules-thin tubes of membrane  Cisternae-large holding vats

Fig Smooth ER Rough ER Nuclear envelope Transitional ER Rough ER Smooth ER Transport vesicle Ribosomes Cisternae ER lumen 200 nm

Roles of ER Rough Ribosomes synthesize excreted proteins  Stored in cisternae or vesicle Modify proteins  Glycosylation of proteins Delivery of membrane associated proteins Often interacts with the Golgi Smooth Tissue-specific uses Storage of carbohydrates Detoxification reactions in liver Synthesizes much of the new membrane material Modification of existing molecules

ER and Golgi Often adjacent in cytoplasm of cell Both are membrane producers  Membrane has sides  Vesicles are produced inside out  Vesicle fuses with surface and excreted proteins are released and integral proteins are added along with membrane ER often performs first steps of modification that is later finished in Golgi