Cell ConnenctionsRead Chapter 4 (all of it) you have a test

soon!

What is the endomembrane system?◦ A network of membranous organelles that partition

the cytoplasm of eukaryotic cells into functional compartments. Some organelles are structurally connected to each other (Nucleus to Rough ER and Smooth ER), whereas others are structurally separated but are functionally connected by the traffic of membranous vesicles that travel between them (ER to Golgi to Lysosomes/Vesicles).

What organelles are involved?◦ Nucleus, ER, Golgi Apparatus, Lysosomes, & Vesicles

Endomembrane System

Explain the difference between the structural and functional connections within the endomembrane system.◦ If organelles are not structurally connected then a

transport vesicle is required to move the contents of one organelle to the next for the contents to be further processed. Each organelle plays a role in modify the product.

◦ Connections – physical or by vesicle – allow the cell to be efficient in producing cell products either for use in the cell or for export out of the cell.

Endomembrane System

Fig. 6-16-3

Smooth ER

Nucleus

Rough ER

Plasma membrane

cis Golgi

trans Golgi

What surrounds a plant cell?◦ Plant cells have cell walls. The cell walls may have

multiple layers: Primary cell wall: relatively thin and flexible Middle lamella: thin layer between primary walls of

adjacent cells Secondary cell wall (in some cells): added between the

plasma membrane and the primary cell wall

How do plant cells communicate (cell to cell)?◦ Plasmodesmata are channels between adjacent plant

cells that allow for cell to cell communication

Cell to Cell Connenction

Fig. 6-28

Secondary cell wallPrimary cell wall

Middle lamella

Central vacuole Cytosol

Plasma membranePlant cell walls

Plasmodesmata

1 µm

Animals cells don’t have cells walls – so what do they have outside their cell membranes?◦ Animal cells lack cell walls but are covered by an

elaborate extracellular matrix (ECM)◦ The ECM is made up of glycoproteins such as

collagen, proteoglycans, and fibronectin◦ ECM proteins bind to receptor proteins in the

plasma membrane called integrins◦ Functions of the ECM include: Support, Adhesion,

Movement, and Regulation

Cell to Cell Connection

Fig. 6-30

EXTRACELLULAR FLUID

Collagen

Fibronectin

Plasmamembrane

Micro-filaments

CYTOPLASM

Integrins

Proteoglycancomplex

Polysaccharidemolecule

Carbo-hydrates

Coreprotein

Proteoglycanmolecule

Proteoglycan complex

How do animal cells communicate (cell to cell) and stick together?◦ At tight junctions, membranes of neighboring cells are

pressed together, preventing leakage of extracellular fluid

◦ Desmosomes (anchoring junctions) fasten cells together into strong sheets

◦ Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells

Cell to Cell Connection

Fig. 6-32

Tight junction

0.5 µm

1 µm

Desmosome

Gap junction

Extracellularmatrix

0.1 µm

Plasma membranesof adjacent cells

Spacebetweencells

Gapjunctions

Desmosome

Intermediatefilaments

Tight junction

Tight junctions preventfluid from movingacross a layer of cells

Which organelles produce cell products?◦ Nucleus, Ribosomes, ER, Golgi Apparatus

Which organelles breakdown materials?◦ Lysosomes, Vacuoles, Peroxisomes

Which organelles produce energy?◦ Chloroplast & Mitochondria

Which organelles are involved in support, movement, and communication?◦ Cytoskeleton, Cell Walls, Extracellular Matrix, &

Cell Junctions

Organelle review

Fig. 6-UN1a

Cell Component

Structure

Function

Concept 6.3 The eukaryotic cell’s geneticinstructions are housed inthe nucleus and carried outby the ribosomes

Nucleus

Surrounded by nuclearenvelope (double membrane)perforated by nuclear pores.The nuclear envelope iscontinuous with theendoplasmic reticulum (ER).

(ER)

Houses chromosomes, made ofchromatin (DNA, the geneticmaterial, and proteins); containsnucleoli, where ribosomalsubunits are made. Poresregulate entry and exit osmaterials.

Ribosome

Two subunits made of ribo-somal RNA and proteins; can befree in cytosol or bound to ER

Protein synthesis

Fig. 6-UN1b

Cell Component

Structure

Function

Concept 6.4 The endomembrane systemregulates protein traffic andperforms metabolic functionsin the cell

Endoplasmic reticulum (Nuclear

envelope)

Golgi apparatus

Lysosome

Vacuole

Large membrane-boundedvesicle in plants

Membranous sac of hydrolyticenzymes (in animal cells)

Stacks of flattenedmembranoussacs; has polarity(cis and transfaces)

Extensive network ofmembrane-bound tubules andsacs; membrane separateslumen from cytosol;continuous withthe nuclear envelope.

Smooth ER: synthesis oflipids, metabolism of carbohy-drates, Ca2+ storage, detoxifica-tion of drugs and poisons Rough ER: Aids in sythesis ofsecretory and other proteinsfrom bound ribosomes; addscarbohydrates to glycoproteins;produces new membrane

Modification of proteins, carbo-hydrates on proteins, and phos-pholipids; synthesis of manypolysaccharides; sorting ofGolgi products, which are thenreleased in vesicles. Breakdown of ingested sub-stances cell macromolecules, and damaged organelles for recycling Digestion, storage, wastedisposal, water balance, cellgrowth, and protection

Fig. 6-UN1c

Cell Component

Concept 6.5Mitochondria and chloro-plasts change energy fromone form to another

Mitochondrion

Chloroplast

Peroxisome

Structure

Function

Bounded by doublemembrane;inner membrane hasinfoldings (cristae)

Typically two membranesaround fluid stroma, whichcontains membranous thylakoidsstacked into grana (in plants) Specialized metaboliccompartment bounded by asingle membrane

Cellular respiration

Photosynthesis

Contains enzymes that transferhydrogen to water, producinghydrogen peroxide (H2O2) as aby-product, which is convertedto water by other enzymesin the peroxisome

Fig. 6-9a

ENDOPLASMIC RETICULUM (ER)

Smooth ER

Rough ERFlagellu

m

Centrosome

CYTOSKELETON:MicrofilamentsIntermediate

filamentsMicrotubules

Microvilli

Peroxisome

Mitochondrion Lysosom

e

Golgiapparatus

Ribosomes

Plasma membrane

NuclearenvelopeNucleolusChromatin

NUCLEUS

Fig. 6-9b

NUCLEUS

Nuclear envelopeNucleolusChromatin

Rough endoplasmic reticulum

Smooth endoplasmic reticulum Ribosome

s

Central vacuole

MicrofilamentsIntermediate filamentsMicrotubules

CYTO-SKELETON

Chloroplast

PlasmodesmataWall of adjacent

cell

Cell wall

Plasma membrane

Peroxisome

Mitochondrion

Golgiapparatus