Copyright © 2010 Pearson Education, Inc. Cells- Part B Cell Organelle and DNA.

Copyright © 2010 Pearson Education, Inc.

Cells- Part B

• Cell Organelle and DNA


Cytoplasm

• Located between plasma membrane and nucleus

• Cytosol

• Water with solutes (protein, salts, sugars, etc.)

• Cytoplasmic organelles

• Metabolic machinery of cell

• Inclusions

• Granules of glycogen or pigments, lipid droplets, vacuoles, and crystals


Cytoplasmic Organelles

• Membranous

• Mitochondria

• Peroxisomes

• Lysosomes

• Endoplasmic reticulum

• Golgi apparatus

• Nonmembranous

• Cytoskeleton

• Centrioles

• Ribosomes


Mitochondria

• Double-membrane structure with shelflike cristae

• Provide most of cell’s ATP via aerobic cellular respiration

• Contain their own DNA and RNA

Copyright © 2010 Pearson Education, Inc. Figure 3.17

Enzymes

Matrix

Cristae

Mitochondrial DNA

Ribosome

Outer mitochondrial membrane

Inner mitochondrial membrane

(b)

(a)

(c)


Ribosomes

• Granules containing protein and rRNA

• Site of protein synthesis

• Free ribosomes synthesize soluble proteins

• Membrane-bound ribosomes (on rough ER) synthesize proteins to be incorporated into membranes or exported from the cell


Endoplasmic Reticulum (ER)

• Interconnected tubes and parallel membranes enclosing cisternae

• Continuous with nuclear membrane

• Two varieties:

• Rough ER

• Smooth ER

Copyright © 2010 Pearson Education, Inc. Figure 3.18a

Nuclearenvelope

Ribosomes

Rough ER

Smooth ER

(a) Diagrammatic view of smooth and rough ER


Rough ER

• External surface studded with ribosomes

• Manufactures all secreted proteins

• Synthesizes membrane integral proteins and phospholipids


Smooth ER

• Tubules arranged in a looping network

• Enzyme (integral protein) functions:

• In the liver—lipid and cholesterol metabolism, breakdown of glycogen, and, along with kidneys, detoxification of drugs, pesticides, and carcinogens

• Synthesis of steroid-based hormones

• In intestinal cells—absorption, synthesis, and transport of fats

• In skeletal and cardiac muscle—storage and release of calcium


Golgi Apparatus

• Stacked and flattened membranous sacs

• Modifies, concentrates, and packages proteins and lipids

• Transport vessels from ER fuse with convex cis face of Golgi apparatus

• Proteins then pass through Golgi apparatus to trans face

• Secretory vesicles leave trans face of Golgi stack and move to designated parts of cell


Protein-containing vesicles pinch off rough ERand migrate to fuse with membranes ofGolgi apparatus.

Proteins aremodified withinthe Golgi compartments.

Proteins arethen packagedwithin differentvesicle types, depending ontheir ultimatedestination.

Plasmamem-brane

Secretion byexocytosis

Vesicle becomeslysosome

Golgiapparatus

Rough ER ERmembrane

Phagosome

Proteins incisterna

Pathway B:Vesicle membraneto be incorporatedinto plasmamembranePathway A:

Vesicle contentsdestined for exocytosis Extracellular fluid

Secretoryvesicle

Pathway C:Lysosome containing acid hydrolaseenzymes

1

3

2


Lysosomes

• Spherical membranous bags containing digestive enzymes (acid hydrolases)

• Digest ingested bacteria, viruses, and toxins

• Degrade nonfunctional organelles

• Break down and release glycogen

• Break down bone to release Ca2+

• Destroy cells in injured or nonuseful tissue (autolysis)


Endomembrane System

• Overall function

• Produce, store, and export biological molecules

• Degrade potentially harmful substances


Golgiapparatus

Transportvesicle

Plasmamembrane

Vesicle

Smooth ER

Rough ER

Nuclear envelope

Lysosome

Nucleus


Endomembrane System

PLAYPLAY Animation: Endomembrane System


Peroxisomes

• Membranous sacs containing powerful oxidases and catalases

• Detoxify harmful or toxic substances

• Neutralize dangerous free radicals (highly reactive chemicals with unpaired electrons)


Cytoskeleton

• Elaborate series of rods throughout cytosol

• Microtubules

• Microfilaments

• Intermediate filaments


Microfilaments

• Dynamic actin strands attached to cytoplasmic side of plasma membrane

• Involved in cell motility, change in shape, endocytosis and exocytosis


Strands made of sphericalprotein subunits called actins

(a) Microfilaments

Actin subunit

7 nm

Microfilaments form the blue networksurrounding the pink nucleus in thisphoto.


Intermediate Filaments

• Tough, insoluble ropelike protein fibers

• Resist pulling forces on the cell and attach to desmosomes

Copyright © 2010 Pearson Education, Inc. Figure 3.23b

(b) Intermediate filaments

Tough, insoluble protein fibersconstructed like woven ropes

10 nm

Fibrous subunits

Intermediate filaments form the purplebatlike network in this photo.


Microtubules

• Dynamic hollow tubes

• Most radiate from centrosome

• Determine overall shape of cell and distribution of organelles

Copyright © 2010 Pearson Education, Inc. Figure 3.23c

(c) MicrotubulesHollow tubes of spherical protein

subunits called tubulins

25 nm

Tubulin subunits

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


Motor Molecules

• Protein complexes that function in motility (e.g., movement of organelles and contraction)

• Powered by ATP


Cytoskeletal elements(microtubules or microfilaments)

Motor molecule (ATP powered)

ATP

(b) In some types of cell motility, motor molecules attached to oneelement of the cytoskeleton can cause it to slide over anotherelement, as in muscle contraction and cilia movement.

ATP

Vesicle

(a) Motor molecules can attach to receptors onvesicles or organelles, and “walk” the organellesalong the microtubules of the cytoskeleton.

Motor molecule (ATP powered)

Microtubule of cytoskeleton

Receptor for motor molecule


Centrosome

• “Cell center” near nucleus

• Generates microtubules; organizes mitotic spindle

• Contains centrioles: Small tube formed by microtubules


Centrosome matrix

(a)

Centrioles

Microtubules


Cellular Extensions

• Cilia and flagella

• Whiplike, motile extensions on surfaces of certain cells

• Contain microtubules and motor molecules

• Cilia move substances across cell surfaces

• Longer flagella propel whole cells (tail of sperm)

PLAYPLAY Animation: Cilia and Flagella


Plasmamembrane

Outer microtubuledoublet

Dynein arms

Centralmicrotubule

Radial spoke

Radial spoke

TEM

TEM

Triplet

Basal body(centriole)

Cilium

Microtubules

Plasmamembrane

Basal body

Cross-linkingproteins insideouter doublets

Cross-linkingproteins insideouter doublets

A longitudinal section of acilium shows microtubules running the length of thestructure.

The doubletsalso have attached motor proteins, the dynein arms.

The outermicrotubule doublets and the two central microtubules are held together by cross-linking proteins and radial spokes.

A cross section through thebasal body. The nine outer doublets of a cilium extend into a basal body where each doublet joins another microtubule to form a ring of nine triplets.

A cross section through thecilium shows the “9 + 2”arrangement of microtubules.

TEM


(a) Phases of ciliary motion.

(b) Traveling wave created by the activity ofmany cilia acting together propels mucusacross cell surfaces.

Power, orpropulsive,stroke

Layer of mucus

Cell surface

Recovery stroke, whencilium is returning to itsinitial position

1 2 3 4 5 6 7


Cellular Extensions

• Microvilli

• Fingerlike extensions of plasma membrane

• Increase surface area for absorption

• Core of actin filaments for stiffening


Microvillus

Actinfilaments

Terminalweb


Nucleus

• Genetic library with blueprints for nearly all cellular proteins

• Responds to signals and dictates kinds and amounts of proteins to be synthesized

• Most cells are uninucleate

• Red blood cells are anucleate

• Skeletal muscle cells, bone destruction cells, and some liver cells are multinucleate


Chromatin (condensed)

Nuclear envelope Nucleus

Nuclear pores

Nucleolus

Cisternae of rough ER

(a)


Nuclear Envelope

• Double-membrane barrier containing pores

• Outer layer is continuous with rough ER and bears ribosomes

• Inner lining (nuclear lamina) maintains shape of nucleus

• Pore complex regulates transport of large molecules into and out of nucleus

Copyright © 2010 Pearson Education, Inc. Figure 3.29b

Nucleus

Nuclearpores

Fractureline of outermembrane

Nuclear pore complexes.Each pore is ringed byprotein particles.

Surface of nuclear envelope.

Nuclear lamina. The netlikelamina composed of inter-mediate filaments formed bylamins lines the inner surfaceof the nuclear envelope.

(b)


Nucleoli

• Dark-staining spherical bodies within nucleus

• Involved in rRNA synthesis and ribosome subunit assembly


Chromatin

• Threadlike strands of DNA (30%), histone proteins (60%), and RNA (10%)

• Arranged in fundamental units called nucleosomes

• Condense into barlike bodies called chromosomes when the cell starts to divide


Metaphasechromosome(at midpointof cell division)

Nucleosome (10-nm diameter; eight histone proteins wrapped by two winds of the DNA double helix)

Linker DNA

Histones

(a)

(b)

1 DNA doublehelix (2-nm diameter)

2 Chromatin(“beads on a string”) structurewith nucleosomes

3 Tight helical fiber(30-nm diameter)

5 Chromatid(700-nm diameter)

4 Looped domain structure (300-nm diameter)

Date post:	18-Jan-2016
Category:	Documents
Upload:	hester-banks
View:	218 times
Download:	0 times

Copyright © 2010 Pearson Education, Inc. Cells- Part B Cell Organelle and DNA.

Documents