Cytology = the study of cells

Cellular basis of life:

•Basic unit of life

•Lowest level with all attributes of life

•Organisms composed of one or more cells

•Cell structure correlated to function

•All cells are related

Chapter 4 CELL STRUCTURE

BIOLOGY

Chapter 4 CELL STRUCTURE

Which cellular structure is common

to all 3 domains of life?

a) Nucleus

b) Endoplasmic reticulum

c) Mitochondria

d) Phospholipid bilayer cell membrane

e) Endocytotic vesicles

Figure 4.6

EukaryoticProkaryotic

Figure 6.3

Brightfield

(unstained specimen)

Brightfield

(stained specimen)

50

m

Confocal

Differential-interference-

contrast (Nomarski)

Fluorescence

10 m

Deconvolution

Super-resolution

Scanning electron

microscopy (SEM)

Transmission electron

microscopy (TEM)

Cross section

of cilium

Longitudinal section

of cilium

Cilia

Electron Microscopy (EM)

1

m1

0

m5

0

m

2 m

2 m

Light Microscopy (LM)

Phase-contrast

Cellular observations

microscopy

Figure 6.4TECHNIQUE

Homogenization

Tissue

cells

Homogenate

Centrifugation

Differential

centrifugation

Centrifuged at

1,000 g

(1,000 times the

force of gravity)

for 10 min Supernatant

poured into

next tube

20,000 g

20 min

80,000 g

60 minPellet rich in

nuclei and

cellular debris

150,000 g

3 hr

Pellet rich in

mitochondria

(and chloro-

plasts if cells

are from a plant)

Pellet rich in

“microsomes”

(pieces of plasma

membranes and

cells’ internal

membranes) Pellet rich in

ribosomes

Cellular fractionation

•To study organelle function

Figure 4.5

• size 1 – 10 µm

• Nucleoid

• Circular DNA plasmid

• Cell wall

• Gram +

• Gram -

Prokaryotes

• DNA not membrane

bound

• Lack membrane bound

organelles

• No histone proteins

• Peptidoglycan

• Widespread

• Size (0.5 – 5 µm)

• Bacteria or Archaea

Fig. 27-2

(a) Spherical(cocci)

1 µm

(b) Rod-shaped(bacilli)

2 µm

(c) Spiral

5 µm

Diplo-

Staphylo-

Strepto-

Prokaryotic Reproduction

• Binary Fission • Genetic Diversity via

Horizontal Gene Transfer• Transformation

• Transduction

• Conjugation

Fig. 27-3

Cellwall

Peptidoglycanlayer

Plasma membrane

Protein

Gram-positive

bacteria

(a) Gram-positive: peptidoglycan trapscrystal violet.

Gram-negativebacteria

(b) Gram-negative: crystal violet is easily rinsed away,revealing red dye.

20 µm

Cellwall

Plasma membrane

Protein

Carbohydrate portionof lipopolysaccharide

Outermembrane

Peptidoglycanlayer

Cell Surface Structures

Hans Christian Gram Gram Staining

LPS component

•O polysacch antigens for ID (E. coli O157:H7)

•Lipid A endotoxin toxic (fever/shock)

antibiotics

Fig. 27-3c

Gram-positive

bacteria

Gram-negativebacteria

20 µm

Figure 6.6

Outside of cell

Inside of cell0.1 m

TEM of a plasma membrane

• Phospholipid bilayer• Cholesterol • Proteins • Carbohydrates

Hydrophilicregion

Hydrophobicregion

Hydrophilicregion

Carbohydrate side chains

ProteinsPhospholipid

(b) Structure of the plasma membrane

8 m

cholesterol

Outside cell

Inside cell

Figure 4.7 Why are cells so small?

• Efficiency in:• Acquisition of nutrients

• Disposal of wastes

• What makes this possible?• High surface areas to volume ratio

a) One largecell.

b) Eight smallcells.

c) Cell withmicrovillion one surface.

Cell size & plasma membrane shape affect SA:V

• Which cell has the larger SA?

• Larger Vol?

• Larger SA:V ratio?

Figure 4.8Figure 4.8

Cell structure reflects eukaryotic cell’s function

a) A portion of several musclecells of the heart (X 1,500).

b) Nerve cells of the centralnervous system (X 830).

c) Cells lining a tubule of a kidney (X 250).

• How are these cells similar?

• What makes these cells different?

Figure 6.8b

Animal Cells

Cell

Nucleus

Nucleolus

Human cells from lining

of uterus (colorized TEM)

Yeast cells budding

(colorized SEM)

10

m

Fungal Cells

5

m

Parentcell

Buds

1 m

Cell wall

Vacuole

Nucleus

Mitochondrion

A single yeast cell(colorized TEM)

Endomembrane System

Figure 6.9aNucleus

Rough ER

Nucleolus

Chromatin

Nuclear envelope:

Inner membrane

Outer membrane

Nuclear pore

Chromatin

Ribosome

Porecomplex

Close-upof nuclearenvelope

• Nuclear Envelope

• Nucleus• Genetic control ctr

• DNA synthesis

• RNA synthesis

• Nuclear pores

Figure 4.12

• Chromatin

a) DNA + histone proteins (8) nucleosome

b) Replicated chromosome

NucleolusRibosome production

• Free or bound

» Protein synthesis

Figure 3.15A transmission electron micrograph (X 6,000) of

the nucleus of an animal cell

Nucleolus

Nuclear

membrane

Nuclear

pores

Nuclear

membrane

Figure 3.15A transmission electron micrograph (X 6,000) of

the nucleus of an animal cell

Nucleolus

Nuclear

membrane

Nuclear

pores

Nuclear

membrane

Nucleolus/nucleoliRibosome production

Free or bound

Protein synthesis

Figure 6.10

0.25 m

Free ribosomes in cytosol

Endoplasmic reticulum (ER)

Ribosomes bound to ER

Large

subunit

Small

subunit

Diagram of a ribosomeTEM showing ER and

ribosomes

Figure 6.11

Smooth ER

Rough ER

ER lumen

CisternaeRibosomes

Smooth ERTransport vesicle

Transitional ER

Rough ER 200 nm

Nuclear

envelope

Endoplasmic Reticulum

• Rough ER

• Smooth ER

Endomembrane Organelles• Rough Endoplasmic

Reticulum (RER)

– Ribosomes

– Protein synthesis

Endomembrane Organelles

• Smooth Endoplasmic Reticulum• No ribosomes

Some functions:

• Carbo metabolism

• Ca++ storage

• Detoxification

• Phospholipid synthesis

cis face

(“receiving” side of

Golgi apparatus)

trans face

(“shipping” side of

Golgi apparatus)

0.1 m

TEM of Golgi apparatus

Cisternae

Endomembrane Organelles• Golgi apparatus/body/complex “warehouse”

• Receives

• Modifies

• Stores

• Ships

Figure 6.15-3

Smooth ER

Nucleus

Rough ER

Plasma

membrane

cis Golgi

trans Golgi

Endomembrane System

Figure 6.13a

Nucleus

Lysosome

1 m

Digestive

enzymes

Digestion

Food vacuole

LysosomePlasma membrane

(a) Phagocytosis

• Lysomsome

• Contains hydrolytic enzymes

• Breaks down “stuff”

• Intracellular digestion of nutrients

Endomembrane

Organelles

Figure 6.13bVesicle containing

two damaged

organelles1 m

Mitochondrion

fragment

Peroxisome

fragment

Peroxisome

VesicleMitochondrion

Lysosome

Digestion

(b) Autophagy

Endomembrane

Organelles• Lysomsome

• Contains hydrolytic enzymes

• Breaks down “stuff”

• Intracellular digestion of nutrients

• “Garbage man” dead organelles

• Programmed cell destruction

• Tay Sachs Disease

Figure 6.14

Central vacuole

Cytosol

Nucleus

Cell wall

Chloroplast

Central

vacuole

5 m

Figure 6.15-1

Smooth ER

Nucleus

Rough ER

Plasma

membrane

Endomembrane System

Figure 6.15-2

Smooth ER

Nucleus

Rough ER

Plasma

membrane

cis Golgi

trans Golgi

Endomembrane System

Figure 6.15-3

Smooth ER

Nucleus

Rough ER

Plasma

membrane

cis Golgi

trans Golgi

Endomembrane System

Enzymes responsible for

biosynthesis of membrane lipids

would be located in what part of

the cell?

a) endoplasmic reticulum.

b) nucleus.

c) lysosomes.

d) Golgi.

e) plasma membrane

Endomembrane Organelles• Lysomsome

– Contains hydrolytic enzymes

– Breaks down “stuff”

• Intracellular digestion of nutrients

• “Garbage man” dead organelles

• Programmed cell destruction

• Tay Sachs Disease

Endomembrane Organelles

• Vacuoles

– Food

• Temp. storage of food

– Contractile

• Expels waste

Types of Vesicles• Storage & shipping vesicles

• Secretory vesicles

• Endocytic vesicles

– Vacuoles

– Food

– Contractile

• Expels waste

• Peroxisomes

– Contain enzymes that detoxify

• Lysosomes

– Contain digestive enzymes Bacterium

Plasma

membrane

Golgi

apparatu

s

Peroxisome

Alcohol

Harmless

waste

Cell toxic

waste

Lysosome

Residual

body

Endomembrane System

A membrane protein synthesized in

the rough ER may be directed to:

a) peroxisomes.

b) lysosomes.

c) mitochondria.

d) all of the above

Golgi

Brefeldin A is a drug that disrupts transport from

the ER to the Golgi apparatus. What other

organelles and membranes are affected?

A. lysosomes, vacuoles, plasma membrane

B. lysosomes, peroxisomes, plasma membrane

C. vacuoles, mitochondria, plasma membrane

D. lysosomes, vacuoles, nuclear membrane

E. all intracellular organelles and membranes

Figure 6.16

NucleusEndoplasmic

reticulum

Nuclear

envelope

Ancestor of

eukaryotic cells

(host cell)

Engulfing of oxygen-

using nonphotosynthetic

prokaryote, which

becomes a mitochondrion

Mitochondrion

Nonphotosynthetic

eukaryote

Mitochondrion

At least

one cell

Photosynthetic eukaryote

Engulfing of

photosynthetic

prokaryote

Chloroplast

Endosymbiotic Eukaryotic Origins

Intermembrane space

Outer

membrane

DNA

Innermembrane

Cristae

Matrix

Free

ribosomes

in the

mitochondrial

matrix

(a) Diagram and TEM of mitochondrion (b) Network of mitochondria in a protist

cell (LM)

0.1 m

Mitochondrial

DNA

Nuclear DNA

Mitochondria

10 m

Mitochondrion/mitochondria

• Double membrane

• Inner membrane

• Cristae energy production

• Matrix energy production

• DNA 1 chromosome

• Binary fission

• All aerobic eukaryotes

Figure 6.17a

Intermembrane space

Outer

DNA

Innermembrane

Cristae

Matrix

Free

ribosomes

in the

mitochondrial

matrix

(a) Diagram and TEM of mitochondrion

0.1 m

membrane

Mitochondrion/mitochondria

RibosomesStroma

Inner and outermembranes

Granum

1 mIntermembrane spaceThylakoid

(a) Diagram and TEM of chloroplast

DNA

Chloroplasts

• Double membrane• Thylakoid (granum/grana)

• Sunlight NRG chemical NRG

• Photosynthetic pigments

• Stroma

• Uses chemical NRG

• Sugar production

• Own DNA

According to the endosymbiont

theory, which of the following

organelles were once endosymbiotic

prokaryotic organisms?

a) Mitochondria and lysosomes

b) Mitochondria and chloroplasts

c) Chloroplasts and Golgi apparatus

d) Golgi apparatus and ribosomes

e) Ribosomes and lysosomes

Figure 6.19

Chloroplast

Peroxisome

Mitochondrion

1 m

Peroxisome

• Single membrane

• Plants & animals

• Detoxifies cells

• H2O2

Figure 6.21

ATPVesicle

(a)

Motor protein

(ATP powered)

Microtubule

of cytoskeleton

Receptor for

motor protein

0.25 mVesiclesMicrotubule

(b)

Table 6.1

Column of tubulin dimers

Tubulin dimer

25 nm

Actin subunit

7 nm

Keratin proteins

812 nm

Fibrous subunit (keratins

coiled together)

10 m 10 m 5 m

Microtubule Function

Taxol, a drug approved for treatment of breast

cancer, prevents depolymerization of microtubules.

What cellular function that affects cancer cells

more than normal cells might taxol interfere with?

a) maintaining cell shape

b) cilia or flagella

c) chromosome movements in cell division

d) cell division (cleavage furrow formation)

e) cytoplasmic streaming

Figure 6.22

Centrosome

Longitudinalsection ofone centriole

Centrioles

Microtubule

0.25 m

Microtubules Cross section

of the other centriole

Figure 6.23

Direction of swimming

(b) Motion of cilia

Direction of organism’s movement

Power stroke Recovery stroke

(a) Motion of flagella 5 m

15 m

Figure 6.24

Microtubules

Plasmamembrane

Basal body

Longitudinal sectionof motile cilium

(a)

0.5 m 0.1 m

0.1 m

(b) Cross section ofmotile cilium

Outer microtubuledoublet

Dynein proteins

Centralmicrotubule

Radialspoke

Cross-linkingproteins betweenouter doublets

Plasma membrane

Triplet

(c) Cross section ofbasal body

Figure 6.25Microtubule

doublets

Dynein protein

ATP

(a) Effect of unrestrained dynein movement

Cross-linking proteins

between outer doubletsATP

Anchorage

in cell

(b) Effect of cross-linking proteins

(c) Wavelike motion

1

2

3

Figure 6.27

Muscle cell

Actin

filament

Myosin

Myosin

filament

head

(a) Myosin motors in muscle cell contraction

0.5 m

100 m

Cortex (outer cytoplasm):

gel with actin network

Inner cytoplasm: sol

with actin subunits

(b) Amoeboid movement

Extending

pseudopodium

30 m(c) Cytoplasmic streaming in plant cells

Chloroplast

Figure 6.27a

Muscle cell

Actinfilament

Myosin

Myosin

filament

(a) Myosin motors in muscle cell contraction

0.5 m

head

Locomotion

Figure 6.27b

100 m

Cortex (outer cytoplasm):

gel with actin network

Inner cytoplasm: sol

with actin subunits

(b) Amoeboid movement

Extending

pseudopodium

Cytoplasmic streaming

Figure 6.27c

30 m(c) Cytoplasmic streaming in plant cells

Chloroplast

Cyclosis/Cytoplasmic streaming

EXTRACELLULAR FLUIDCollagen

Fibronectin

Plasmamembrane

Micro-filaments

CYTOPLASM

Integrins

Proteoglycancomplex

Polysaccharidemolecule

Carbo-hydrates

Coreprotein

Proteoglycanmolecule

Proteoglycan complex

Cytoskeleton & extracellular matrix

Figure 6.32

Tight junctions prevent

fluid from moving

across a layer of cells

Tight junction

Tight junction

TEM0.5 m

TEM1 m

TE

M

0.1 m

Extracellular

matrixPlasma membranes

of adjacent cells

Space

between cells

Ions or small

molecules

Desmosome

Intermediate

filaments

Gap

junction

Cellular Junctions• Tight

• Anchoring

• Gap

Figure 6.28

Secondary

cell wall

Primary

cell wall

Middle

lamella

Central vacuole

Cytosol

Plasma membrane

Plant cell walls

Plasmodesmata

1 m

Plasmodesmata

Figure 6.UN01

Nucleus

(ER)

(Nuclear

envelope)

Semen & Ovum