AS CIE Cell structure and ultrastructure

A3: Cell Structure and ultrastructure

Plan

1 Introduction:

1.1 Definition of a Cell

1.2 Number of Cells

1.3 Size of Cells

2 Prokaryotic and Eukaryotic Cells:

2.1 A Typical Prokaryotic Cell

2.2 A Typical Eukaryotic Cell

2.3 A Typical Animal Cell

2.4 Some Specialized Animal Cells

2.5 A Typical Plant Cell

2.6 Some Specialized Plant Cells

3 Cell structure :

3.1 Extracellular Matrix in Animals

3.2 Bacterial Cell Wall

3.3 Plant Cell Wall

3.4 Intercellular junctions

3.5 Plasma Membrane

3.6 Cytoplasm

2

3

4

1

5

4 Inside the Cytoplasm :

4.1 Organelles

4.2 Nucleus

4.3 Endoplasmic Reticulum

4.4 Ribosomes

4.5 Golgi’s Apparatus

4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles

4.9 Organelles with DNA:

Mitochondria

Chloroplasts

4.10 Cytoskeleton

5 Cell Fractionation:

6 Conclusions and Overviews

6.1 Prokaryotic and Eukaryotic Cells

6.2 Components of the Cell

6.3 Tissue, Organ and System

Xavier DANIEL, Ph.D. AS

Animal Cell Bacterial Cell

Cell is the basic unit of all living organisms

“Building block of life”

Definition of a Cell

Plant Cell

1


Unicellular organisms are made of one unique cell only

Each cell performs ALL tasks

The cells of multicellular organisms are specialized to

perform precise tasks

– e.g. mesophyll cells for photosynthesis and root hair cells for water and

ions absorption in Plants

– e.g. red blood cells to transport oxygen and white blood cells for immunity

in Animals

Definition of a Cell


Organisms may be:

• Unicellular – composed

of one cell

• Multicellular- composed

of many specialized cells

1

Number of Cells


1

Number of Cells

10 14 cells = 100 trillion cells

= 100,000,000,000,000 cells

1 cell

E.coli Homo sapiens


Surface area increases while total volume remains constant

5

1 1

Total surface area (height width number of sides number of boxes)

Total volume (height width length number of boxes)

Surface-to-volume ratio (surface area volume)

6

1

6

150

125

12

750

125

6

1

Size of Cells

What is best, one big cell or many small cells ?


1.2

A smaller cell

– Has a higher surface to volume ratio,

– which facilitates the exchange of materials into and out of the cell

Surface area increases while total volume remains constant

5

1 1

Total surface area (height width number of sides number of boxes)

Total volume (height width length number of boxes)

Surface-to-volume ratio (surface area volume)

6

1

6

150

125

12

750

125

6

1

Size of Cells

What is best, a smal cell or a big cell ?


1.2

Most cells are relatively small because as size increases,

The volume of the cell increases much more rapidly than its size

– longer diffusion time inside the cell

1

Size of Cells


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








Cells may be Prokaryotic

or

Eukaryotic

Prokaryotic and Eukaryotic Cells 2



The word prokaryote comes from the Greek

πρό- (pro-) "before"

and καρυόν (karyon) “nut” or “kernel”

The word eukaryote comes from the Greek

eu (eu) "good"

and καρυόν (karyon) “nut” or “kernel”

Kernel = the softer, usually edible part contained in the shell of a nut or

the stone of a fruit


Prokaryotes

Include Bacteria and Archaea

No nucleus

No organelles (membrane-bound structures)

Eukaryotes

Most other cells: Fungi, Plants and Animals

Nucleus

Organelles


Unicellular organisms

Unicellular

Or

Multicellular organisms


• Cell wall

• Plasma membrane

• Cytoplasm

• Free circular DNA

• Ribosomes

A Typical Prokaryotic Cell 2

0.1 – 10mm

Depending on the species

outside

inside


• Cell wall (only plant cells)

• Plasma membrane

• Cytoplasm

• DNA mostly in Nucleus

• Ribosomes

• Organelles

A Typical Eukaryotic Cell 2

10 – 100mm

Depending on the species

outside

inside


Plant Cell Animal Cell

Two main Types of Eukaryotic Cells 2


Rough ER Smooth ER

Centrosome (2 centrioles)

CYTOSKELETON

Microfilaments

Microtubules

Microvilli

Peroxisome

Lysosome

Golgi apparatus

Ribosomes

In animal cells but not plant cells: Lysosomes Centrioles

Flagella (in some plant sperm)

Nucleolus

Chromatin

NUCLEUS

Flagelium

Intermediate filaments

ENDOPLASMIC RETICULUM (ER)

Mitochondrion

Nuclear envelope

Plasma membrane

A Typical Animal Cell 2


Some Specialized Animal Cells 2

white blood cell

red blood cell

cheek cells sperm

nerve cell

muscle cell

Amoeba

Paramecium

unicellular


In plant cells but not animal cells: Chloroplasts

Central vacuole and tonoplast Cell wall

Plasmodesmata

CYTOSKELETON

Ribosomes (small brown dots)

Central vacuole

Microfilaments


Microtubules

Rough endoplasmic reticulum Smooth

endoplasmic reticulum

Chromatin

NUCLEUS

Nuclear envelope

Nucleolus

Chloroplast

Plasmodesmata Wall of adjacent cell

Cell wall

Golgi apparatus

Peroxisome

Tonoplast

Centrosome

Plasma membrane

Mitochondrion

A Typical Plant Cell 2


Onion Epidermal Cells

Root Hair Cell

root hair

Guard Cells

Some Specialized PlantCells 2

unicellular


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

From outside to inside the cell

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton









Extracellular Matrix in Animals 3

Animal cells do not have a cell wall

Between cells,

There is an elaborate matrix

=

The Extracellular Matrix

ECM


Extracellular Matrix in Animals 3

ECM = Collagen + Fibronectin + Glycoproteins

Glycoproteins/Proteoglycans = Proteins “decorated” with sugars

Functions of the ECM include

– Support

– Adhesion

– Movement


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton









The Bacterial Cell Wall 3

Two kinds of Bacteria

Based on their Cell Wall Structure

Gram-negative The Gram test is negative

Gram-positive The Gram test is positive





The Gram test : Differentiate Gram+ and Gram -

primary

stain

mordant

counterstain

decolorization

Positive

Negative


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1


4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








Cell wall

The Plant Cell Wall 3

Cell wall of

neighbour cell

Cell wall of

neighbour cell


Dead layer

Strong and rigid

Gives shape to the cell

Resist entry of excess water into the cell

Made of cellulose which forms very thin fibers




There are three parts in the Plant Cell Wall


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1


4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








Intercellular junctions in Plants 3

Plasmodesmata connect insides of adjacent cells

Plasma membrane (edge view)

Root cells

Cell wall (edge view)

Middle lamella (edge view)

Root

Plasmodesmata


Intercellular junctions in Plants 3

Channels that perforate plant cell walls

=

Channels that connect two plant cells

=

Plasmodesmata


Plasmodesma (singular)

Plasmodesmata (plural)

Interior

of cell

Interior

of cell

0.5 µm Plasmodesmata Plasma membranes

Cell walls

3

Space

between cells

Intercellular junctions in Plants


3

A typical plant cell has between 103 and 105 plasmodesmata

connecting it with adjacent cells !!!

Used to transport material between cells

DNA, mRNA, proteins...

Plasmodesmata

Continuum between Endoplasmic Reticula of two cells

Intercellular junctions in Plants


Three types of intercellular junctions in

Animals

3

Intercellular junctions in Animals

Tight

junctions

Desmosomes

Gap

junctions


Tight junctions formed by strands

of protein

Plasma membrane (edge view)

Cells lining bladder

Tight junctions seal membranes of adjacent cells

together

3


Tight junctions


3


Tight junctions

At tight junctions, the membranes of

neighboring cells are very tightly pressed

against each other, bound together by

specific proteins (green).

Forming continuous seals around the cells,

tight junctions prevent leakage of

extracellular fluid across a layer of cells.


desmosome

Protein strands holding cells

together

Protein filaments in cytoplasm

Small intestine Plasma membrane

(edge view)

Cells lining small intestine

3


Desmosomes = Anchoring junctions


3


Desmosomes = Anchoring junctions

Desmosomes function like rivets

They fasten cells together

into strong sheets.

Intermediate filaments of keratin proteins

anchor desmosomes in the cytoplasm


desmosome

Gap Junctions: pairs of channels connect insides of

adjacent cells

Liver Plasma membrane (edge view)

Liver cells

3


Gap junctions = Communicating junctions


3


Gap junctions = Communicating junctions


3



Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1


4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








3

The Plasma Membrane

Plasma membrane = Cell membrane

Surrounds the cells

Prokayotes and Eukaryotes


AS and A Biology


3

The Plasma Membrane

Plasma membrane

Bacterial Cell

Surrounds the cell

Against the cell wall


3

The Plasma Membrane

Surrounds the cell

Animal Cell

Plasma membrane


3

The Plasma Membrane

Plasma membrane

Plant Cell

Surrounds the cell

Against the cell wall


3

The Plasma Membrane

Surrounds the Cell

Living layer

Made of protein and phospholipids

Selective barrier: Controls what goes in and out of the cell


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

Inside the cell

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








3

The Cytoplasm

Cytoplasm = Cytosol

Jelly-like substance enclosed by cell membrane

Medium for chemical reactions to take place

pH = 7.2

Prokayotes and Eukaryotes


3

The Cytoplasm

Cytoplasm

Bacterial Cell


3

The Cytoplasm

Animal Cell

Cytoplasm


3

The Cytoplasm

Cytoplasm

Plant Cell


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton







Inside the cell


4

Organelles

An Organism has functional units called Organs

A Cell has functional units called Organelles

Only in Eukaryotes

Prokaryotes do not have organelles


4

Organelles

Inside the Cytoplasm of Eukayotes

Each organelle has a specific function

With or without its own membrane


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








4

Nucleus

One nucleus per eukaryotic cell

Controls the activities of the cell

“The Brain of the Cell”

Contains most genetic information = DNA

Surrounded by a double membrane

= Nuclear envelope


Animal Cell

Nucleus

Nucleus 4


Plant Cell

Nucleus

Nucleus 4


4

Nucleus


4

Nucleus

Nuclear envelope:

Barrier between cytoplasm and nucleus

20-40 nm thick

Between inner and outer membranes:

Perinuclear space

PS contiguous with ER’s lumen


http://upload.wikimedia.org/wikipedia/commons/3/38/Diagram_human_cell_nucleus.svg

4

Nucleus

Inner membrane encloses nucleoplasm

Cell has cytoplasm

Nucleus has nucleoplasm



4

Nucleus

Inside nucleoplasm:

Two types of Chromatin:

Heterochromatin (dense DNA)

and

Euchromatin (not dense DNA)



4

Nucleus

Inside nucleoplasm:

Nucleolus

Makes RNA to make Ribosomes



4

Nucleus

Nuclear pores

RNA out, proteins in



Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








4

Endoplasmic Reticulum

There are two distinct regions of ER

Smooth ER

No ribosomes

Rough ER

Ribosomes on it


Animal Cell

4

Rough

endoplasmic

reticulum

Smooth

endoplasmic

reticulum



Plant Cell

4

Rough

endoplasmic

reticulum

Smooth

endoplasmic

reticulum



4


Both ER are delimited by a membrane

Inside of both ER = Lumen


4


The smooth ER

– Makes lipids

– Sends lipids to the Golgi

apparatus

The rough ER

– Makes proteins that will be secreted

– Packs these proteins in vesicles

– Sends these vesicles to the Golgi apparatus

Functions of both RE


4


The Rough ER membrane

is continuous with the outer nuclear membrane


4


The Smooth ER membrane

is continuous with the Rough ER membrane


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








4

Ribosomes

Ribosome = RNAs + Proteins

RNAs made in Nucleolus

Exported to the cytoplasm

Site of protein synthesis

Made of two subunits

Non-membranous organelles


4

Ribosomes

Free ribosomes = in the cytoplasm of Eukaryotes and

Prokayotes

= in the mitochondria and chloroplasts of Eukaryotes

OR

Bound ribosomes: on the membrane of the Rough ER

Eukaryotes only


4

Ribosomes

Bacteria, mitochondria, chloroplasts Eukaryotes

“smaller” 20 nm diameter

“bigger” 25-30 nm diameter


Bacterial Cell

4

Ribosomes

Free ribosomes


Animal Cell

4

Ribosomes bound

to the Rough

ER

Free ribosomes

Ribosomes


Plant Cell

4

Ribosomes bound

to the Rough

ER

Free ribosomes

Ribosomes


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








4

Golgi Apparatus

Golgi Apparatus = Golgi body = Golgi

Discovered by Italian Camillo Golgi (1898)

Metabolism of glycoproteins

Metabolism of lipids

Exocytosis of glycoproteins


4

Golgi Apparatus

Structure

Flattened sacks Side that receives

transport vesicles from

the ER

Side that exports

secretory vesicles

from

the Golgi


4

Golgi Apparatus

The cis face receives transport vesicles

containing

1) proteins from the RER

2) lipids from the SER

How does it work ?

1

ER Golgi

Transport vesicle


4

Golgi Apparatus

In the cisternae, carbohydrates are added

to the proteins

=

Glycoproteins

How does it work ?

2


4

Golgi Apparatus

Glycoproteins move from cis to trans faces

How does it work ?

3


4

Golgi Apparatus

How does it work ?

4 Glycoproteins are packed inside secretory

vesicles


4

Golgi Apparatus

Proteins in secretory vesicles

are released outside the cell

by exocytosis

Fusion between

the vesicle’s membrane

and the plasma membrane

How does it work ?

5


Animal Cell

4

Golgi

Golgi Apparatus


Plant Cell

4

Golgi Apparatus

Golgi


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








4

Lysosome

“Lysis” = process to destroy

“Soma” = Body

Lysosome = organelle to destroy Worn-out organelles, food, viruses, bacteria

pH = 4.8

Only in Animal Cells

Contain digestive enzymes Proteases, lipases,…


Digestion of outside material

=

Phagocytosis 1 µm

Lysosome contains

active hydrolytic

enzymes

Food vacuole

fuses with

lysosome

Hydrolytic

enzymes digest

food particles

Digestion

Food vacuole

Plasma membrane

Lysosome

Digestive

enzymes

Lysosome

Nucleus

4

Lysosome


Lysosome containing

two damaged organelles 1 µ m

Mitochondrion

fragment

Peroxisome

fragment

Lysosome fuses with

vesicle containing

damaged organelle

Hydrolytic enzymes

digest organelle

components

Vesicle containing

damaged mitochondrion

Digestion

Lysosome

Digestion of inside material

=

Autophagocytosis = Autophagy

4

Lysosome


4 4

Endomembrane System

Phagocytosis and Autophagocytosis


4

Animal Cell

Lysosome

4

Lysosome


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








4 4

Peroxysome

In almost all eukariotic cells

Destruction of some lipids Very long chain fatty acids

Made of vesicles from the ER

Reduction-oxydation (redox) reactions


4

Animal Cell

Peroxysome

4

Peroxysome


Plant Cell

4

Peroxysome

Peroxysome


4 4

Endomembrane System


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








4 4

Vacuole

Membrane of the vacuole = Tonoplast

In all Plant and fungal cells

In some animal and bacterial cells

Water + molecules (inorganic and organic) + enzymes

Function, shape and number: according to the cell’s needs


4 4

Vacuole

Functions:

Stores water to

- Maintain turgor of Plants (cells + whole plant)

-Help seeds germinate

Isolates harmful materials

Stores waste products


Plant Cell

4

Central

vacuole

Vacuole


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








4 4

Where is DNA found ?

DNA is not only in the nucleus !

Two organelles contain their own DNA

Mitochondrion Plural: Mitochondria

Chloroplast

In all eukariotic cells Only in Plant cells

Small, circular DNA Small, circular DNA


4 4

Where are Ribosomes found ?

Ribosomes are not only in the cytoplasm!

Two organelles contain their own Ribosomes

Mitochondrion Plural: Mitochondria

Chloroplast

In all eukariotic cells Only in Plant cells

Ribosomes in Mitochondria and Chloroplast are similar to

Prokaryotic Ribosomes Xavier DANIEL, Ph.D. AS

Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








4 4

Mitochondria

The word mitochondrion comes from Greek

μίτος (mitos) "thread“

and

χονδρίον (chondrion) "granule“

“The Powerhouse of the Cell”


4 4

Mitochondria

Production of ENERGY = ATP

Site of cellular respiration

Double membrane

In all eukaryotic cells

Contain their own DNA and ribosomes


4 4

Mitochondria


4 4

Mitochondria

Site of enzymatic reactions


4

Animal Cell

Mitochondrion

4

Mitochondria


Plant Cell

4

Mitochondrion

Mitochondria


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








4 4

Chloroplast

The word chloroplast comes from Greek

χλωρός (Chloros) = “green”

and

Πλάστης (plastid) = “plant organelle”

Chloroplast is a green organelle


4 4

Chloroplast

Production of ENERGY = Sugar

Site of photosynthesis

Contains Chlorophyll

Double membrane

Only in plant cells and protista

Contains its own DNA and ribosomes


4 4

Chloroplast

Ten to one hundred per mesophyll cell !!!


4 4

Chloroplast


Plant Cell

4

Chloroplasts

Chloroplast


4

Where do Mitochondria and Chloroplasts come from ?

2.5 billion

years ago…

The endosymbiosis theory


4


2.5 billion

years ago…

1.5 billion

years ago….

The endosymbiosis theory


Evidence in favor of the endosymbiosis theory is

that mitochondria and chloroplasts:

Have appropriate size to be descendants of eubacteria.

Have inner membranes similar to those of prokaryotic plasma membranes.

Replicate by splitting, as prokaryotes do.

DNA is circular and different from the DNA of the cell's nucleus.

Have ribosomes similar to prokaryotic ribosomes.

4



Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








4

Cytoskeleton

Cytoskeleton

“Skeleton of the cell”

Supports cell shape

and

Keeps organelles in place

Movements inside the cell


4

Cytoskeleton

Three main components


4

Cytoskeleton



4

Cytoskeleton

Microtubules


Animal Cell

4

Centriole

Ribosomes


4

Cytoskeleton

Microfilaments


The centrosome

“microtubule-organizing center”

Made of two centrioles

Only in Animal cells

4

Centrosome and Centrioles

Centrosome

Microtubule

Centrioles

0.25 µm

Longitudinal section

of one centriole

Microtubules Cross section

of the other centriole


Cilia and flagella

Contain specialized arrangements of

microtubules

Some cells use them for movement

4

Cytoskeleton


Ciliary motion Cilia have a back-and-forth motion that moves the cell in a direction perpendicular

to the axis of the cilium.

A dense nap of cilia, beating at a rate of about 40 to 60 strokes a second, covers this

Colpidium, a freshwater protozoan (SEM).

15 µm

4

Cytoskeleton


Flagella beating pattern

A flagellum usually undulates, its snakelike motion driving a cell in the same

direction as the axis of the flagellum.

Propulsion of a human sperm cell is an example of flagellatelocomotion (LM).

1 µm

Direction of swimming

4

Cytoskeleton


Cytoplasmic streaming

Created by microfilaments

Nonmoving

cytoplasm (gel)

Chloroplast

Streaming

cytoplasm

(solution)

Parallel actin

filaments

Cell wall

4

Cytoskeleton


Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








Cell Fractionation 5

Fraction

= a part which is distinct from the whole

Fractionation

= 1. Process to make fractions

= 2. Result of this process

Cell Fractionation = Separating the different parts of the Cell

In reality: Taking cells apart and separating the major

organelles from one another



Strategy

Different organelles have different sizes and densities

Separate them using those parameters



Method

1 Cells are homogenized in a blender to

break them up

2 The resulting mixture (cell homogenate)

is centrifuged at various speeds and

durations to fractionate the cell

components, forming a series of pellets.

3 Take the different pellets separately

Tissue

cells

Homogenization

Homogenate 1000 g

(1000 times the

force of gravity)

10 min Differential centrifugation

Supernatant poured

into next tube

20,000 g 20 min

Pellet rich in

nuclei and

cellular debris

Pellet rich in

mitochondria

(and chloro-

plasts if cells

are from a

plant)

Pellet rich in

“microsomes”

(pieces of

plasma mem-

branes and

cells’ internal

membranes)

Pellet rich in

ribosomes

150,000 g 3 hr

80,000 g 60 min





Centrifuge speed and force




Plan

1 Introduction:


1.2 Number of Cells

1.3 Size of Cells








3 Cell structure :



3.3 Plant Cell Wall


3.5 Plasma Membrane

3.6 Cytoplasm

2

3

1

4

5


4.1 Organelles

4.2 Nucleus


4.4 Ribosomes


4.6 Lysosomes

4.7 Peroxysomes

4.8 Vacuoles


Mitochondria

Chloroplasts

4.10 Cytoskeleton








Animal and Plant cells

Main similarities

Both have a cell membrane surrounding the cytoplasm

Both have a nucleus

Both contain mitochondria


Animal and Plant cells

Main differences

Animal cells Plant cells

Relatively smaller

in size

Irregular shape

No cell wall

Relatively larger

in size

Regular shape

Cell wall

No chloroplast Chloroplast Xavier DANIEL, Ph.D. AS

Prokayotic and Eukaryotic cells


Components of Eukaryotic cells

Peroxysomes


Components of Eukaryotic cells


Tissue

A group of similar cells to perform a particular function

– Animals : epithelial tissue, muscular tissue…

– Plants : vascular tissue, mesophyll…

Tissue, Organ and System


Organ

Different tissues group together to

carry out specialized functions

– Heart : consists of muscles, nervous

tissue and blood vessels

– Leaf : consists of epidermis,

mesophyll and vascular tissues



Stomata

Air Space

Spongy Mesophyll

Cell

Chloroplast

The Structure of a Leaf

Palisade Mesophyll

Cell



The Structure of a Heart



System

Several organs and tissues work together to

carry out a particular set of functions in a

co-ordinated way

– Human : digestive, respiratory, excretory, circulatory

and reproductive systems

– Plant : root and shoot systems




The Digestive System



The Respiratory System



The Circulatory System



The Nervous System


Levels of Organization

CELLS (muscle cells,nerve cells)

TISSUES (muscle, epithelium)

ORGANS (heart, lungs, stomach)

SYSTEMS (circulatory system)

ORGANISM (human)

Tissue, Organ and System…and Organism


A Typical Animal Cell


A Typical Plant Cell


Documents

AS CIE Cell structure and ultrastructure