Ch 4

Tour of the Cell

Cells

• Smallest unit that shows properties of life– Metabolizes– Reproduces

• Cell Theory– All organisms consist of one or more cells– The cell is the smallest unit of life– New cells arise from old cells– Cells pass hereditary material to offspring

Microscopic Worlds

• Microscopes led to the discovery of the cell– Discovered “animalcules”

and wee “beasties”• Antoni van Leeuwenhoek• Robert Hooke

Microscopic Worlds

Cell Size

• House DNA, protein molecules and internal structures

• Obtain nutrients and diffuse nutrients and O2

• Smaller cells have a greater surface area to volume ratio than do larger cells– Surface area is significant for diffusion and

osmosis

Surface area : Volume

• Volume= 30 um *30 um* 30 um=27000um • SA (large)= 6*(30um*30um)=5,400 um• SA (small)=(6*(10um*10um))*27=16,200 um

30 m 10 m

30 m 10 m

Surface areaof one large cube 5,400 m2

Total surface areaof 27 small cubes 16,200 m2

Domains of Life

• The 3 domains of life – Bacteria (prokaryotic cells)– Archaea (prokaryotic cells)– Eukarya (all other life forms)

Cells• Prokaryotic

– Bacteria & Archaea• Eukaryotic

– Protists, fungi, plants, animals

Prokaryotic cells are simpler & usually smaller than Eukaryotic cells

Prokaryotic cell

Nucleoidregion

Nucleus

Eukar yotic cell Organelles

Co

loriz

ed

TE

M 1

5,0

00

In Common

• Bounded by plasma membrane• Ribosomes• Cytoplasm• DNA as genetic material

Prokaryote• Do not have membrane

bound nucleus• Have a cell wall outside

their plasma membrane• Circular DNA strands• No membrane bound

organelles

Prokar yoticflagella

Ribosomes

Capsule

Cell wall

Plasmamembrane

Nucleoid region (DNA)

Pili

Eukaryote

• Membrane bound nucleus

• Linear DNA• Membrane

bound organelles

NucleusSmooth endoplasmicreticulumRough

endoplasmicreticulum

Ribosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Flagellum

Not in mostplant cells Lysosome

Centriole

Microtubule

CytoskeletonIntermediatefilament

Microfilament

Peroxisome

Eukaryotic Cells• A typical animal cell:

• Contains a variety of membranous organelles (underlined)

NucleusSmooth endoplasmicreticulum

Roughendoplasmicreticulum

Ribosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Flagellum

Not in mostplant cells Lysosome

Centriole

Microtubule

CytoskeletonIntermediatefilament

Microfilament

Peroxisome

Figure 4.4A

Eukaryotic Cells

• A typical plant cell Smooth endoplasmicreticulum

Rough endoplasmicreticulum

CYTOSKELETON:

NUCLEUS

Ribosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Peroxisome

Cell wall

Central vacuole Microtubule

Intermediatefilament

Microfilament

Cell wall ofadjacent cell

Chloroplast

Plasmodesmata

Categories of Organelles• Structural support, movement, communication

– Cytoskeleton, plasma membrane, cell wall (plants)• Manufacturing

– Nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus

• Energy processing– Mitochondria (animal), chloroplasts (plants)

• Hydrolysis– Lysosomes (animals), vacuoles (plants),

peroxisomes

Plasma Membrane• Forms boundary around cell• Controls and regulates material transport

-Semi permeable• Phospholipid bilayer

Plants and Cell Walls

• Cell wall– Cellulose

• Connect by plasmodesmata– Channels between adj. cells

Plasma membrane

Cytoplasm

Plasmodesmata

Vacuole

Layers of one plant cell wall

Walls of two adjacent plant cells

Cytoskeleton

• Cell’s internal skeleton – Helps organize structure and activities– Consists of network of protein fibers

Actin subunit

Microfilament

7 nm

Fibrous subunits

10 nm

Intermediate filament Microtubule

25 nm

Tubulin subunit

Cytoskeleton• Microfilaments (actin filiments)

– Enable cells to change shape and move

• Intermediate filaments – Reinforce the cell and anchor certain organelles

• Microtubules – give the cell rigidity, provide anchors for organelles,

act as tracks for organelle movement

Actin subunit

Microfilament

7 nm

Fibrous subunits

10 nm

Intermediate filament Microtubule

25 nm

Tubulin subunit

Nucleus• Contains most of the

cells DNA• Eukaryotic

chromosomes made of chromatin

• Enclosed by nuclear enveloper

• Nucleolus– rRNA synthesized

NucleusChromatin

Nucleolus

Pore

Ribosomes

Roughendoplasmicreticulum

Two membranesof nuclearenvelope

Ribosomes

• Free and bound ribosomes• Composed of 2 subunits

– Involved in protein synthesis

Endomembrane System• Interconnected structurally and functionally

– Physically connectedOR– Connected via vesicles

Nucleus

Smooth ER Nuclear envelope Golgi apparatus

Lysosome

Vacuole

Plasmamembrane

Rough ERTransport vesiclefrom ER to Golgi

Transport vesicle fromGolgi to plasma membrane

Rough Endoplasmic Reticulum• Membrane continuous

with nuclear envelope– Makes more membrane – Transferred via vesicles

• Bound ribosomes– Produces proteins– Transported or secreted

Smooth ER

Rough ER

Nuclearenvelope

Rough ER

Ribosomes

Smooth ER

TE

M 4

5,00

0

Figure 4.7

Fig. 4-9b

Transport vesiclebuds off

Secretoryproteininside trans-port vesicle

Glycoprotein

Polypeptide

Ribosome

Sugarchain

Rough ER

1

2

3

4

Smooth ER

• Lacks bound ribosomes• Involved in metabolic

processes– Synthesis of lipids,

hormones, enzymes

• Stores calcium

Golgi Apparatus• Vesicles from ER go to Golgi• Receives and modifies products

Golgi apparatus

TE

M 1

30

,00

0

Transportvesicle fromthe Golgi“Shipping” side

of Golgi apparatus

Golgiapparatus

“Receiving” side ofGolgi apparatus

Transportvesiclefrom ER

New vesicleforming

Lysosomes• Digestive enzymes enclosed by membrane sac• Destroy ingested bacteria, recycle damaged

organelles • Break down food

DigestiveenzymesLysosome

Plasmamembrane

Food vacuoleDigestion

Lysosome

Vesicle containingdamaged mitochondrion

Digestion

Lysosomes

Figure 4.10AFigure 4.10A

GolgiapparatusPlasma

membrane

“Food”

Foodvacuole

Lysosomes

Lysosomeengulfingdamagedorganelle

Digestion

Engulfmentof particle

Transport vesicle(containing inactivehydrolytic enzymes)

Rough ER

Vacuoles

• Membranous sac• Central Vacuole

– hydrolytic function

• Contractile• Food

Chloroplast

Centralvacuole

Nucleus

Col

oriz

ed T

EM

8,7

00

Peroxisomes

• Metabolize fatty acids & inactivate toxins• Enzymes that digest peroxides• Come only from ER

Mitochondria• Cellular respiration

– Converts chemical energy to ATP

– Phospholipid bilayer membrane

– Has own DNA and ribosomes

Mitochondrion

Outermembrane

Intermembranespace

Matrix

Innermembrane

Cristae

TE

M 4

4,8

80

Chloroplasts• Convert solar energy to chemical energy (photosynthesis)• Stroma

– Contains DNA, ribosomes and enzymes• Thylakoids

– Interconnected sacs that form stacks called granum

Endosymbosis

• Hypothesis of endosymbosis– Mitochondria and chloroplasts were once small

prokaryotes living independently– At some point, began living within larger cells

Movement• Cilia

– Short appendage, numerous– Move via coordinated beating– Stirs fluid around stationary cells

• Flagella– Long appendage, whip-like– Move via bending

• Pseudopods– Irregular long lobes– Bulge outward and drag cell

Movement

Cilia lining lungs

Extracellular matrix• Holds cells to tissues• Protect and support PM

– Integrins

• Regulate behavior, transmit information, coordinate cells

Cell Junctions•Tight junctions can bind cells together into leakproof sheets•Anchoring junctions link animal cells into strong tissues•Gap junctions allow substances to flow from cell to cell

Anchoring junction

Tight junctions

Gap junctions

Extracellular matrix

Space between cells

Plasma membranes of adjacent cellsFigure 4.18B

Fig. 4-23

Videos• Overview• http://www.youtube.com/watch?v=NiiLS_ovLwM&feature=related• http://www.youtube.com/user/greatpacificmedia#p/u/56/vCqQLoRaTNA• Basic cell structure

http://www.youtube.com/watch?v=mphqugYoiQY&feature=related• Cytoskeleton• http://www.youtube.com/user/greatpacificmedia#p/u/55/5rqbmLiSkpk• Cell membrane and wall• http://www.youtube.com/user/greatpacificmedia#p/u/52/-aSfoB8Cmic