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. 6-10

NucleolusNucleus

Rough ER

Nuclear lamina (TEM)

Close-up of nuclear envelope

1 µm

1 µm

0.25 µm

Ribosome

Pore complex

Nuclear pore

Outer membraneInner membraneNuclear envelope:

Chromatin

Surface ofnuclear 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. 6-11

Cytosol

Endoplasmic reticulum (ER)

Free ribosomes

Bound ribosomes

Large subunit

Small subunit

Diagram of a ribosomeTEM 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. 6-12

Smooth ER

Rough ER Nuclear envelope

Transitional ER

Rough ERSmooth ERTransport vesicle

RibosomesCisternaeER 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