IB Biology2 Cells

2.3 Eukaryotic Cells

Jason de Nys

All syllabus statements ©IBO 2007All images CC or public domain or link to original material.

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

2.3.1.Draw and label a diagram of the ultrastructure of a liver cell as an example of an animal cell

2.3.2 Annotate the diagram from 2.3.1 with the functions of each named structure.

The bright blue stains are nuclei in HeLa cells. Read “The Immortal Life of Henrietta Lacks” for a fascinating story of the origin of HeLa cells

http://commons.wikimedia.org/wiki/File:HeLa_cells_stained_with_Hoechst_33258.jpg

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 the DNA in the nucleus, exits through pores more in 3.3, 3.4 and 7.1 and 7.2

- Some cells have multiple nuclei

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

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 membraneMore in 2.4

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

http://commons.wikimedia.org/wiki/File:Animal_mitochondrion_diagram_en.svghttp://commons.wikimedia.org/wiki/File:Mitochondria,_mammalian_lung_-_TEM.jpg

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 in

the cellMore in 3.7 and 8.1

Remember: Where else do we see loops of DNA?How does the size of a mitochondrion compare with an average prokaryote?

The implications of the answers to these questions are in Option D: Evolution

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

It is where protein synthesis occurs

more in 3.5 and 7.4

http://www.flickr.com/photos/cryo_mariena/6033827307/sizes/m/in/photostream/

The (free) Ribosome, the molecular machine responsible for protein synthesis

much, much more in 3.5 and 7.4

A ribosome on the sculpture “Waltz of the Polypeptides” at Cold Spring Harbor Laboratory

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

http://en.wikipedia.org/wiki/File:Nucleus_ER_golgi.svg

The Golgi Apparatus is a flattened stack of membranes responsible for the packaging and delivery of proteins

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

Lysosomes are simple, membrane-bound organelles full of enzymes that digest engulfed bacteria and viruses and large moleculesfor recycling.

http://www.tokresource.org/tok_classes/biobiobio/biomenu/eukaryotic_cells/index.htm

Image from an amazing site by teacher Andrew Brown

2.3.3 Identify structures from 2.3.1 in electron micrographs of liver cells.

Rough Endoplasmic Reticulum

Smooth Endoplasmic Reticulum

Mitochondrion

What can you see?

2.3.4 Compare prokaryotic and eukaryotic cells

Compare Give an account of similarities and differences between two (or more) items, referring to both (all) of them throughout

Prokaryotic Eukaryotic

Small cells Relatively larger cells

Always unicellular Some multicellular, some unicellular

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

DNA in chromosomes in a membrane-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

Table modified from Click4Biology

2.3.5 State three differences between plant and animal cells

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

Animals

Don’t have a cell wall

Don’t have chloroplasts anywhere

Carbohydrate stored as glycogen and animal fat

Flexible shape

May have small, temporary vacuoles

Plants

Have 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

http://www.flickr.com/photos/powi/749366522/http://www.flickr.com/photos/chubbybat/45407031/

V.

2.3.6 Outline two roles of extracellular components

Outline: Give a brief account or summary.

Got a banana?

Bone cells have an extracellular matrix in the interstitial spaces (between the cells)of collagen and calcium phosphate; which together form the hard bone.

http://www.flickr.com/photos/limonada/14705232/

The other form of extracellular matrix is the basement membranes

They exist in many tissue types as a form of support e.g. as the lining in blood vessels

You may already know about the glomerulus in the kidney. A basement membrane is integral to ultrafiltration there.

More in HL 11.3

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

As well as extracellular matrices in animals, plant have extracellular components….Cell Walls

http://www.flickr.com/photos/ah_pao/2590017159/

They are made of cellulose and provide structure, support and protection. They

maintain cell shape and prevent turgor pressure from rupturing the cell

Further information:

A good introduction to what a cell is and the functions of organelles

Three of the best sites for IB-specific Biology information. The top link takes you to the PPT by Stephen Taylor