Cell Structure and Function

Kandinsky (1866-1944)

Early Observations

• Santiago Ramon y Cajal (1852-19340

• Mid 1600s - Robert

Hooke cells in cork

• Late 1600s - Antony

van Leeuwenhoek,

microorganisms

Early Discoveries

Early Discoveries

• 1820s - Robert Brown observed

nucleus in plant cells

Microscopes

• Light microscopes• Magnify to 1,000X

LM 1

,000

Figure 4.1B

• Greater magnification

SE

M 2

,000

TE

M 2

,800

Figure 4.1C Figure 4.1D

Electron Microscope

• Cells vary • Surface area - limits

Human height

Length of somenerve andmuscle cells

Chicken egg

Frog egg

Un

aid

ed e

ye

Lig

ht m

icro

sco

pe

Ele

ctro

n m

icro

scop

e

10 m

1 m

100 mm(10 cm)

10 mm(1 cm)

1 mm

100 m

10 m

1 m

100 nm

10 nm

1 nm

0.1 nmAtoms

Proteins

Small molecules

Lipids

Viruses

Ribosome

Nucleus

Mycoplasmas(smallest bacteria)

Most plant andanimal cells

Most bacteria

Mitochondrion

Cell Size

– Ratio of surface area to volume

30 m 10 m

30 m 10 m

Surface areaof one large cube 5,400 m2

Total surface areaof 27 small cubes 16,200 m2Figure 4.2B

Cell Size

Cell Theory

1) Every organism is composed of

cells

2) Cell is smallest unit of life

3) Continuity of life from cells growth

+ division

Structure of Cells

• Two types

• Prokaryotic - bacteria– No nucleus

– DNA?

Prokar yoticflagella

Ribosomes

Capsule

Cell wall

Plasmamembrane

Nucleoid region (DNA)

Pili

Structure of Cells

• Eukaryotic – plants, animals, fungi– DNA?

Structure of Cells

Prokaryotic cell

Nucleoidregion

Nucleus

Eukar yotic cell Organelles

Co

loriz

ed

TE

M 1

5,0

00

Eukaryotic Cells• Nucleus and

organellesNucleus

Smooth endoplasmicreticulum

Roughendoplasmicreticulum

Ribosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Flagellum

Not in mostplant cells Lysosome

Centriole

Microtubule

CytoskeletonIntermediatefilament

Microfilament

Peroxisome

Plant Cell Features

CentralvacuoleNot in

animalcells

Chloroplast

Cell wall

Golgiapparatus

Nucleus

Microtubule

CytoskeletonIntermediatefilament

Microfilament

Ribosomes

Smoothendoplasmicreticulum

Mitochondrion

Peroxisome

Plasma membrane

Roughendoplasmicreticulum

Components of the Nucleus

NucleusChromatin

Nucleolus

Pore

Ribosomes

Roughendoplasmicreticulum

Two membranesof nuclearenvelope

Smooth ER

Rough ER

Nuclearenvelope

Rough ER

Ribosomes

Smooth ER

TE

M 4

5,00

0

Figure 4.7

Smooth ER

Rough ER

Secretory(glyco-) proteininside trans-port vesicle

4Transport vesiclebuds off

Sugar chain

3

Rough ER

Glycoprotein2Polypeptide

Ribosome

1

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

Golgi Apparatus

Vesicles• Lysosomes

Vesicles• Vacuoles

– Central vacuole– Contractile vacuole

Chloroplast

Centralvacuole

Nucleus

Col

oriz

ed T

EM

8,7

00

LM

6

50

Nucleus

Contractilevacuoles

Mitochondria

Mitochondrion

Outermembrane

Intermembranespace

Matrix

Innermembrane

Cristae

TE

M 4

4,8

80

Chloroplasts

TE

M 9

,750

Chloroplast

Stroma

Intermembranespace

Inner and outermembranes

Granum

Figure 4.14

LM

60

0

Co

loriz

ed

SE

M 4

,10

0

Figure 4.17A Figure 4.17B

Flagella and Cilia

Figure 4.17C

Flagellum Electron micrographsof cross sections:

Flagellum

Basal bodyBasal body(structurally identical to centriole)

TE

M 2

06,5

00

TE

M

206,

500

Plasmamembrane

Dynein arms

Radial spoke

Centralmicrotubules

Outer microtubuledoublet

Flagella and Cilia

Cytoskeletal Elements

Actin subunit

Microfilament

7 nm

Fibrous subunits

10 nm

Intermediate filament Microtubule

25 nm

Tubulin subunit

Microtubules

• Involved in plant/ animal interactions

Figure 4.21Page 71

tubulinsubunit

Microfilaments

• Muscle contraction

actinsubunit

Intermediate Filaments

onepolypeptidechain

Plant Cell Walls

• Primary cell wall = outer • Secondary cell wall

– Rigid– Cellulose and lignin

• Middle lamella joins cells together

Plant Cell Walls

Primary cell wall

Secondary cell wall(3 layers)

Plant Cell Walls

Slide 35

plasmamembrane

middle lamella

primarycell wall

plasmodesmata

Figure 4.27bPage 74

Animal Cell Junctions

• Tight junctions– Link cells of most body tissues– Waterproof

• Adhering junctions– Link cells prone to stretching

• Gap junctions– Link cytoplasm - rapid signals

Animal Cell Junctions

tightjunctions

adhering junction

gapjunction

Question of the Day

What is the role of the smooth ER in increasing drug tolerance?