The Ultrastructure of Cells (1.2)IB Diploma Biology

1.2.4 Electron microscopes have a much higher resolution than light microscopes.

• Resolution: making separate parts of

an object distinguishable by the eye

• Beams of electrons have shorter

wavelengths than visible light; so

much higher resolution

Resolution

mm µm nm

Eye 0.1 100 100,000

Light micro.

0.0002 0.2 200

Electron micro.

0.000001 0.001 1

Escherichia coli (E. coli) http://en.wikipedia.org/wiki/Escherichia_coli

Prokaryotes“Before nucleus:” evolutionary precursors to eukaryotes.

1.2.1 Prokaryotes have a simple cell structure without compartments

1.2.1 Prokaryotes have a simple cell structure without compartments

Cell structures animation:

http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.swf

cell wall: protective protein-based coating (Gram + / Gram -

)plasma membrane: selectively permeable, controls entry &

exit of materials to and from the cell.

pili: attach to other bacteria for DNA transfer

ribosomes: protein synthesis (transcription & translation)

flagella: whiplash-like motion causes movement

cytoplasm: contains enzymes for metabolic reactions

nucleoid: closed-loop of bacterial DNA in a condensed area

Prokaryotic Cell Parts

Past-paper question: E. coli TEM image

Image from IB Biology QuestionBank CDRom – get a copy here: https://store.ibo.org/biology

Identify these structures:

I.

II.

III.

IV.

Calculate the magnification of the

image.

Past-paper question: E. coli TEM image

Image from IB Biology QuestionBank CDRom – get a copy here: https://store.ibo.org/biology

Identify these structures:

I. Plasma membrane

II. Cell wall / pili

III. Nucleoid

IV. Cytoplasm / ribosomes

Calculate the magnification of the

image.

1. Measure the scale bar in mm.

2. Multiply x 1000 to convert to μm.

That is the magnification.

How long is the bacterium?

PROKARYOTESE

P

R

O

D

U

C

E

through

binary

fissiontwo-parts splitting

1.2.3 Prokaryotes divide by binary fission.

PROKARYOTESE

P

R

O

D

U

C

E

throughbinary

fissionThe closed-loop DNA of the

bacterium makes copies through

semi-conservative DNA replication.

New plasmids are pulled to

opposing poles by fibers.

The bacterium divides in two.

http://www.youtube.com/watch?v=gEwzDydciWc

So after absorbing all of that information, all you have

to do is put it in the diagram! Annotate: to add brief notes

to a diagram or graph.

1.2.7 Draw the ultrastructure of prokaryotic cells based on electron micrographs.

1.2.2 Eukaryotes have a compartmentalized cell structure.

1.2.8 Draw the ultrastructure of eukaryotic cells based on electron micrographs.

The Cell membrane is the boundary of the cell.

• It acts as a “gatekeeper”, preventing the entry or exit of

some molecules and facilitating the movement of others.

• It is a phospholipid bilayer

• It is permeable to oxygen and carbon dioxide

• It is impermeable to water and charged particles, they

must enter through special proteins embedded in the

membrane

More in 2.4

http://commons.wikimedia.org/wiki/File:Cell_membrane_detailed_diagram_en.svg

The Nucleus contains

the chromosomes which

comprise most of the

DNA in a cell

- It is the largest

organelle

- It has a double layer

membrane

- mRNA, transcribed

from DNA in nucleus,

exits through pores

- Some cells have

multiple nuclei

http://images.wellcome.ac.uk/

Rough Endoplasmic Reticulum

Smooth Endoplasmic Reticulum

Spot the

difference?

The ‘spots’ are the

difference!

The Rough

Endoplasmic Reticulum

is peppered with

ribosomes that give it

the rough appearance

Proteins synthesized

here are secreted

Smooth ER is site of lipid

production

http://commons.wikimedia.org/wiki/File:C_Golgi.jpg

http://commons.wikimedia.org/wiki/File:Golgi_in_the_cytoplasm_of_a_macrophage_in_the_alveolus_(lung)_-

_TEM.jpg

I shall name it………The internal reticular apparatus!!

Pretty catchy… no?*

*Everybody thought that was a

terrible name, so they called it the

Golgi apparatus instead

Camillo

Golgi

The Golgi Apparatus is a

flattened stack of membranes

responsible for the packaging

and delivery of proteins

Lysosomes are simple, membrane-bound organelles full of

enzymes that digest engulfed bacteria and viruses and

large molecules for recycling.

Mitochondria in mammalian lung cells

The Mitochondrion (pl. Mitochondria)

• The ‘power house’ of the cell

• Has a smooth outer membrane and a

folded inner membrane

• Where aerobic respiration occurs

Free Ribosomes:

• 80s sized in

eukaryotes (v. 70s

size in prokaryotes)

• Proteins

synthesized for

use within the cell

(i.e. enzymes used

in the cytoplasm)

Chloroplasts

• Site of Photosynthesis in Plant Cells

• Stacks of Thylakoids

Vacuoles & Vesicles:• Animal cells sometimes have small vacuoles for digestion

• Unicellular organisms have contractile vacuoles for expelling water

• Plant cells have large vacuoles that hold water and food

• Vesicles are small lipid sacs used for transport

Centrioles & Microtubules:

• Centrioles are bundles of

microtubules found in Animal Cells

• Microtubules separate

chromosomes in cell division and

make-up cilia and flagella

1.2.8 Draw the ultrastructure of eukaryotic cells based on electron micrographs.

State: Give a specific name, value or other brief answer without

explanation or calculation.

AnimalsDon’t have a cell wall

Don’t have chloroplasts anywhere

Carbohydrate stored as glycogen and animal fat

Flexible shape

May have small, temporary vacuoles

PlantsHave a cell wall

Have chloroplasts in photosynthetic cells

Carbohydrate stored as starch and plant oils

Rigid Shape (due to cell wall)

Have a large permanent storage vacuole

V.

Compare: Give an account of similarities and differences between

two (or more) items, referring to both (all) of them throughout

Prokaryotic EukaryoticSmall cells Relatively larger cells

Always unicellular Some multicellular, some unicellular

No nucleus: DNA a ‘naked’ loop in the nucleoid region

DNA in chromosomes in amembrane-bound nucleus

Ribosomes smaller (70s) Ribosomes larger (80s)

No mitochondria, respiration in cell membrane and mesosomes

Mitochondria, where aerobic respiration occurs

Cell division by binary fission Cell division by Meiosis or Mitosis

Reproduction asexual (some gene exchange can occur via conjugation)

Reproduction Sexual or asexual

1.2.5 The structure and function of organelles within the exocrine gland cells of the

pancreas.

• Enzymes are

proteins, so these

cells must produce

proteins in large

quantities

• Organelles involved:• Rough ER

• Vesicles

• Golgi Apparatus

• Plasma membrane

Exocrine gland cells of the Pancreas secrete digestive

enzymes into small intestine

1.2.6 The structure and function of organelles within palisade mesophyll cells of the leaf.

• Organelles involved:• Chloroplasts

• Mitochondria

• Large Vacuole

Palisade mesophyll cells carry out most of the

photosynthesis in plant cells

1.2.9 Interpret electron micrographs to identify organelles and deduce the function of

specialized cells.

Identify the labeled structures in this liver cell TEM image.

Source: http://www.udel.edu/biology/Wags/histopage/empage/empage.htm

What can you

see?

Bibliography / Acknowledgments

Jason de

Nys

Chris

Paine