CELLS

THE CYTOPLASM

• CYTOSOL: JELLY-LIKE FLUID

• CONTAINS THE CYTOSKELETON

• COMPOSED OF 75 – 90% WATER + IONS, GLUCOSE, AMINO ACIDS, FATTY ACIDS, PROTEINS, LIPIDS, ATP, AND WASTE PRODUCTS

• CYTOPLASMIC ORGANELLES: METABOLIC MACHINERY OF THE CELL• SEPARATE STRUCTURES THAT MAY OR MAY NOT BE ENCLOSED BY A

MEMBRANE

• PERFORM SPECIFIC ESSENTIAL FUNCTIONS OF THE CELL

RIBOSOMES

• CONSTRUCTED OF PROTEIN AND RIBOSOMAL RNA (RRNA)

• PRODUCED IN THE NUCLEOLUS

• FUNCTION AS THE SITE OF PROTEIN SYNTHESIS

• FREE RIBOSOMES SYNTHESIZE SOLUBLE PROTEINS USED IN THE CYTOSOL

• MEMBRANE-BOUND RIBOSOMES SYNTHESIZE PROTEINS FOR INSERTION IN THE PM OR SECRETION FROM THE CELL

ENDOPLASMIC RETICULUM (ER): NETWORK OF MEMBRANE-ENCLOSED CHANNELS (CISTERNAE)

• ROUGH ER (RER): WITH ATTACHED RIBOSOMES (CONTINUOUS WITH THE NUCLEAR ENVELOPE) SYNTHESIZES GLYCOPROTEINS AND PHOSPHOLIPIDS

• PRODUCTS TRANSFERRED INTO ORGANELLES, INSERTED INTO PM, OR SECRETED DURING EXOCYTOSIS

• SMOOTH ER (SER): NO RIBOSOMES (CONTINUOUS WITH RER) SYNTHESIZES FATTY ACIDS AND STEROIDS; INACTIVATES/DETOXIFIES DRUGS AND HARMFUL SUBSTANCES; REMOVES PHOSPHATE GROUP FROM GLUCOSE-6-PHOSPHATE

ER STORE CALCIUM IONS UNTIL NEEDED

ROUGH ENDOPLASMIC RETICULUM

Figure 3.5

Ribosome

Protein

Protein insidetransport vesicle

Transportvesicle buds off

mRNA

Rough ER

As the protein is synthesizedon the ribosome, it migratesinto the rough ER cistern.

In the cistern, the protein foldsinto its functional shape. Shortsugar chains may be attachedto the protein (forming aglycoprotein).

The protein is packaged in atiny membranous sac called atransport vesicle.

The transport vesicle buds fromthe rough ER and travels to theGolgi apparatus for furtherprocessing or goes directly tothe plasma membrane where itscontents are secreted.

ROUGH ENDOPLASMIC RETICULUM

Figure 3.5, step 1

Ribosome

Protein

mRNA

Rough ER

As the protein is synthesizedon the ribosome, it migratesinto the rough ER cistern.

ROUGH ENDOPLASMIC RETICULUM

Figure 3.5, step 2

Ribosome

Protein

mRNA

Rough ER

As the protein is synthesizedon the ribosome, it migratesinto the rough ER cistern.

In the cistern, the protein foldsinto its functional shape. Shortsugar chains may be attachedto the protein (forming aglycoprotein).

ROUGH ENDOPLASMIC RETICULUM

Figure 3.5, step 3

Ribosome

Protein

Transportvesicle buds off

mRNA

Rough ER

As the protein is synthesizedon the ribosome, it migratesinto the rough ER cistern.

In the cistern, the protein foldsinto its functional shape. Shortsugar chains may be attachedto the protein (forming aglycoprotein).

The protein is packaged in atiny membranous sac called atransport vesicle.

ROUGH ENDOPLASMIC RETICULUM

Figure 3.5, step 4

Ribosome

Protein

Protein insidetransport vesicle

Transportvesicle buds off

mRNA

Rough ER

As the protein is synthesizedon the ribosome, it migratesinto the rough ER cistern.

In the cistern, the protein foldsinto its functional shape. Shortsugar chains may be attachedto the protein (forming aglycoprotein).

The protein is packaged in atiny membranous sac called atransport vesicle.

The transport vesicle buds fromthe rough ER and travels to theGolgi apparatus for furtherprocessing or goes directly tothe plasma membrane where itscontents are secreted.

CLINICAL CONNECTION – SER AND DRUG TOLERANCE

• SER DETOXIFIES SOME DRUGS SUCH AS THE SEDATIVE PHENOBARBITAL

• TAKEN REPEATEDLY, INDIVIDUALS DEVELOP CHANGES IN THE SER OF THEIR LIVER CELLS

• PROLONGED ADMINISTRATION RESULTS IN INCREASED TOLERANCE TO THE DRUG

• WITH REPEATED EXPOSURE THE AMOUNT OF SER AND ITS ENZYMES INCREASES TO PROTECT THE CELL FROM ITS TOXIC EFFECTS

• INCREASED SER HIGHER AND HIGHER DOSES NEEDED TO ACHIEVE ORIGINAL EFFECT

GOLGI APPARATUS: PACKAGING AND SHIPPING DEPARTMENT

• STACK OF 3 TO 10 DISC-SHAPED MEMBRANOUS SACS (CISTERNAE)

1. MODIFIES, SORTS, PACKAGES PRODUCTS OF THE RER SENDING THEM TO THEIR PROPER DESTINATION

2. FORMS SECRETORY VESICLES THAT SECRETES PROCESSED PROTEINS VIA EXOCYTOSIS3. FORMS MEMBRANE VESICLES TO SEND NEW MOLECULES TO THE PM4. FORMS TRANSPORT VESICLES TO CARRY MOLECULES TO OTHER ORGANELLES

(LYSOSOMES)• PRODUCTS OF RER MOVE THROUGH THE GOLGI FROM THE CONVEX (CIS) SIDE TO THE CONCAVE (TRANS) SIDE

Cis face—“receiving” side

Secretory vesicleTransport vesicle

Transportvesiclefromtrans faceTrans face—

“shipping” side

New vesiclesforming

Cisternae

Transport vesiclefrom rough ER

Golgi apparatus

Figure 2.8

SEQUENCE OF EVENTS FROM PROTEIN SYNTHESIS ON THE ROUGH ER TO THE PROTEINS FINAL DISTRIBUTION

Plasmamembrane

Secretion by exocytosis

Vesicle becomeslysosome

Golgi apparatus

Rough ER ER membrane Phagosome

Proteins in cisterna

Pathway B:Vesicle membraneto be incorporatedinto plasmamembranePathway A:

Vesicle contentsdestined forexocytosis

Extracellular fluid

Secretoryvesicle

Pathway C:Lysosomecontaining acidhydrolaseenzymes

Protein-containing vesicles pinch off rough ER and migrate to fuse with membranes of Golgi apparatus.

Proteins are modified within the Golgi compartments.

Proteins are then packaged within different vesicle types, depending on their ultimate destination.

1

2

3

Figure 3.6

Extracellular fluid

Plasma membrane

Golgi vesicle containingmembrane componentsfuses with the plasmamembrane

Golgi vesicle containingdigestive enzymesbecomes a lysosome

Proteins in cisterna

Lysosome fuses withingested substances

Membrane

Transportvesicle

Pathway 3

Pathway 2

Secretory vesicles Pathway 1

Golgiapparatus

Golgi vesicle containingproteins to be secretedbecomes a secretoryvesicle

Cisterna

Rough ER

Proteins

Secretion byexocytosis

Figure 3.6, step 1

Extracellular fluid

Plasma membrane

Proteins in cisterna

Membrane

Golgiapparatus

Cisterna

Rough ER

Figure 3.6, step 2

Extracellular fluid

Plasma membrane

Proteins in cisterna

Membrane

Transportvesicle

Golgiapparatus

Cisterna

Rough ER

Pathway 1

Figure 3.6, step 3

Extracellular fluid

Plasma membrane

Proteins in cisterna

Membrane

Transportvesicle

Golgiapparatus

Cisterna

Rough ER

Pathway 1

Figure 3.6, step 4

Extracellular fluid

Plasma membrane

Proteins in cisterna

Membrane

Transportvesicle

Secretory vesicle Pathway 1

Golgiapparatus

Golgi vesicle containingproteins to be secretedbecomes a secretoryvesicle

Cisterna

Rough ER

Figure 3.6, step 5

Extracellular fluid

Plasma membrane

Proteins in cisterna

Membrane

Transportvesicle

Secretory vesicles Pathway 1

Golgiapparatus

Golgi vesicle containingproteins to be secretedbecomes a secretoryvesicle

Cisterna

Rough ER

Proteins

Secretion byexocytosis

Figure 3.6, step 6

Extracellular fluid

Plasma membrane

Proteins in cisterna

Membrane

Transportvesicle

Pathway 2Golgiapparatus

Cisterna

Rough ER

Figure 3.6, step 7

Extracellular fluid

Plasma membrane

Proteins in cisterna

Membrane

Transportvesicle

Pathway 2Golgiapparatus

Cisterna

Rough ER

Figure 3.6, step 8

Extracellular fluid

Plasma membrane

Golgi vesicle containingmembrane componentsfuses with the plasmamembrane

Proteins in cisterna

Membrane

Transportvesicle

Pathway 2Golgiapparatus

Cisterna

Rough ER

Figure 3.6, step 9

Extracellular fluid

Plasma membrane

Proteins in cisterna

Membrane

Transportvesicle

Pathway 3

Golgiapparatus

Cisterna

Rough ER

Figure 3.6, step 10

Extracellular fluid

Plasma membrane

Golgi vesicle containingdigestive enzymesbecomes a lysosome

Proteins in cisterna

Membrane

Transportvesicle

Pathway 3

Golgiapparatus

Cisterna

Rough ER

Figure 3.6, step 11

Extracellular fluid

Plasma membrane

Golgi vesicle containingdigestive enzymesbecomes a lysosome

Proteins in cisterna

Lysosome fuses withingested substances

Membrane

Transportvesicle

Pathway 3

Golgiapparatus

Cisterna

Rough ER

Figure 3.6, step 12

Extracellular fluid

Plasma membrane

Golgi vesicle containingmembrane componentsfuses with the plasmamembrane

Golgi vesicle containingdigestive enzymesbecomes a lysosome

Proteins in cisterna

Lysosome fuses withingested substances

Membrane

Transportvesicle

Pathway 3

Pathway 2

Secretory vesicles Pathway 1

Golgiapparatus

Golgi vesicle containingproteins to be secretedbecomes a secretoryvesicle

Cisterna

Rough ER

Proteins

Secretion byexocytosis

LYSOSOMES: MEMBRANE-ENCLOSED VESICLES CONTAINING DIGESTIVE ENZYMES (HYDROLASES)

1. DIGEST SUBSTANCES THAT ENTER A CELL VIA ENDOCYTOSIS AND TRANSPORT FINAL PRODUCTS OF DIGESTION INTO THE CYTOSOL

2. AUTOPHAGY : DIGESTION OF INTERNAL MEMBRANES, PROTEINS, AND ORGANELLES THAT ARE DAMAGED OR WORN OUT

3. AUTOLYSIS: DIGESTION OF THE ENTIRE CELL

4. EXTRACELLULAR DIGESTION: FUSE WITH VESICLES CONTAINING SUBSTANCES FOR DEGRADATION SUCH AS INGESTED BACTERIA AND VIRUSES

CLINICAL CONNECTION – TAY-SACHS DISEASE• A INHERITED DISORDER CAUSED BY ABSENCE OF A SINGLE LYSOSOMAL

ENZYME CALLED HEX A

• HEX A BREAKS DOWN GANGLIOSIDE GM2, A MEMBRANE GLYCOLIPID

PREVALENT IN NERVE CELLS

• AS EXCESS GANGLIOSIDE ACCUMULATES, NERVE CELLS FUNCTION LESS EFFICIENTLY RESULTING IN SEIZURES AND MUSCLE RIGIDITY

• GRADUALLY AFFECTED INDIVIDUALS BECOME BLIND, DEMENTED, AND UNCOORDINATED AND USUALLY DIE BEFORE THE AGE OF 5

PEROXISOMES: TOXIC WASTE DISPOSAL SYSTEM

• PEROXISOMES: MEMBRANE-WALLED SACS OF OXIDASE ENZYMES• ENZYMES NEUTRALIZE FREE RADICALS AND DEGRADE TOXIC SUBSTANCES

• OXIDASES: ENZYMES OXIDIZE (REMOVE HYDROGEN ATOMS FROM) VARIOUS ORGANIC SUBSTANCES AND TOXIC SUBSTANCES SUCH AS ALCOHOL

• TOXIC BYPRODUCTS OF METABOLISM, HYDROGEN PEROXIDE (H2O2) DECOMPOSED BY CATALASE AND SUPEROXIDE (O2

-) BY

SUPEROXIDE DISMUTASE

• WITHOUT PEROXISOMES, BYPRODUCTS OF METABOLISM WOULD ACCUMULATE RESULTING IN CELLULAR DEATH

• BREAK DOWN LONG CHAINS OF FATTY ACIDS

• NUMEROUS IN THE LIVER AND KIDNEYS

PROTEASOMES

• TINY BARREL-SHAPED PROTEIN STRUCTURES THAT CONTAIN PROTEASES

• ENZYMES THAT BREAK DOWN UNNEEDED, DAMAGED, OR FAULTY CYTOSOLIC PROTEINS

• ALZHEIMER DISEASE AND PARKINSON DISEASE MAY RESULT FROM FAILURE OF PROTEASOMES TO DEGRADE ABNORMAL PROTEINS

Copyright 2012, John Wiley & Sons, Inc.

MITOCHONDRIA: CELL’S POWER PLANT• COMPLEX ORGANELLE THAT GENERATES MOST OF THE

CELL’S ENERGY

• SELF-REPLICATE: ABUNDANT IN ENERGY-REQUIRING CELLS (MUSCLE CELLS, SPERM)

• ENCLOSED BY TWO MEMBRANES: SMOOTH OUTER MEMBRANE, INNER MEMBRANE FOLDS INWARD TO PRODUCE CRISTAE (“CRESTS”)

• ATP PRODUCTION STARTS IN THE MATRIX (CITRIC ACID CYCLE / KREB CYCLE)

• COMPLETED ON INNER MEMBRANE (OXIDATIVE PHOSPHORYLATION AND ELECTRON TRANSPORT)

Enzymes

(a) Microfilaments

Strands made of spherical proteinsubunits called actins

(b) Intermediate filaments

Tough, insoluble protein fibersconstructed like woven ropes

(c) Microtubules

Hollow tubes of spherical proteinsubunits called tubulins

Actin subunit

7 nm 10 nm 25 nm

Fibrous subunitsTubulin subunits

Microfilaments form the blue networksurrounding the pink nucleus in this photo.

Intermediate filaments form the purplebatlike network in this photo.

Microtubules appear as gold networkssurrounding the cells’ pink nuclei in this photo.

CYTOSKELETON (“CELL SKELETON”): ELABORATE NETWORK OF RODS

• MICROFILAMENTS: FILAMENTS COMPOSED OF ACTIN (CONTRACTILE PROTEIN)

• INTERMEDIATE FILAMENTS: COMPOSED OF TOUGH INSOLUBLE PROTEIN FIBERS

• MICROTUBULES: CYLINDRICAL STRUCTURES MADE OF PROTEINS (TUBULIN SUBUNITS)

CENTROSOME AND CENTRIOLES

• CENTROSOMES: SPHERICAL STRUCTURES IN THE CYTOPLASM COMPOSED OF CENTROSOME MATRIX AND PAIR OF CENTRIOLES

• MATRIX SEEDS GROWTH AND ELONGATION OF MICROTUBULES

• CENTRIOLES: PAIRED CYLINDRICAL BODIES COMPOSED OF 27 SHORT MICROTUBULES

• FORMATION OF MITOTIC SPINDLE IN KARYOKINESIS (NUCLEAR DIVISION)

• CILIA AND FLAGELLA: MADE OF MICROTUBULES

• CILIA FUNCTIONS IN MOVEMENT OF SUBSTANCES OVER CELL SURFACES

• FLAGELLA PROPEL SPERM

CILIA AND FLAGELLA

Copyright 2012, John Wiley & Sons, Inc.

Cilia move fluids along a cell surface

A flagellum moves an entire cell

CLINICAL CONNECTION – CILIA AND SMOKING

• CILIA: MOVEMENT PARALYZED BY NICOTINE IN CIGARETTE SMOKE

• SMOKERS COUGH OFTEN TO REMOVE FOREIGN PARTICLES FROM THEIR AIRWAYS

• IN FEMALES CILIA ON CELLS THAT LINE THE UTERINE TUBES SWEEP OOCYTES TOWARD THE UTERUS

• SMOKING INCREASES THE RISK OF ECTOPIC PREGNANCY

CYTOPLASMIC INCLUSIONS

• TEMPORARY STRUCTURES NOT PRESENT IN ALL CELL TYPES

• MAY CONSIST OF PIGMENTS, CRYSTALS OF PROTEIN, AND FOOD STORES

• LIPID DROPLETS: FOUND IN LIVER CELL AND FAT CELLS

• GLYCOSOMES: STORE SUGAR IN THE FORM OF GLYCOGEN

THE NUCLEUS: CONTROL CENTER OF THE CELL

• LARGEST ORGANELLE ~5ΜM IN DIAMETER

• CONTAINS THE GENETIC MATERIAL (DNA) THAT DIRECTS THE CELL’S ACTIVITIES

• NUCLEAR ENVELOPE: PARALLEL MEMBRANES SEPARATED BY A FLUID-FILLED SPACE

• NUCLEAR PORES ALLOW LARGE MOLECULES TO PASS IN AND OUT OF THE NUCLEUS

• NUCLEOLUS (‘LITTLE NUCLEUS’): SITE OF RIBOSOME SUBUNIT ASSEMBLY

• CONTAINS PARTS OF SEVERAL CHROMOSOMES

Chromatin (condensed)

Nuclear envelope Nucleus

Nuclearpores

Nucleolus

Cisternae of rough ER(a)

Nuclear pore complexesEach pore ringed by protein particles

CELL DIVERSITY

Figure 3.8a

CELL DIVERSITY

Figure 3.8b

CELL DIVERSITY

Figure 3.8c

CELL DIVERSITY

Figure 3.8d

CELL DIVERSITY

Figure 3.8e

CELL DIVERSITY

Figure 3.8f

CELL DIVERSITY

Figure 3.8g