CellsAnd Differentiation

What is a Cell?• A cell is the basic structural unit of all living things• It is a microscopic structure which contains organelles along with

cytoplasm enclosed within a membrane and/or a cell wall

Sayer, J. (2011) Cells [Picture]http://wakeup-world.com/2012/01/14/the-flame-of-cell-life-death-in-the-miracle-of-regeneration

Groups of Cells• There are two basic groups of cells:

– Eukaryotic• Animal• Plant

http://www.phschool.com/science/biology_place/biocoach/cells/review3.html

– Prokaryotic• Bacteria

http://www.daviddarling.info/encyclopedia/B/bacteria.html

What’s the Difference?• Prokaryotic Cells

– bacterial cells – They do not have a nuclear membrane– They are unicellular– Lack membrane bound organelles

• Eukaryotic Cells– There are two basic types:

• Animal Cells• Plant Cells

– They have a nuclear membrane– They can be unicellular and multicellular– They have membrane bound organelles

What are organelles?

• Organelles are structures that have a specific function (job) in the cell

• Some of the most common organelles are:– Cell membrane– Cell wall– Cytoplasm– Cytoskeleton

– Nucleus– Nucleolus– Centrioles– Ribosome– Endoplasmic Reticulum

• Smooth• Rough

– Golgi Apparatus– Mitochondria– Lysosome

Cell Membrane – Aka plasma membrane

– Fluid Mosaic Model• Found on the outside of the cell• Made up mainly of

phospholipids and proteins• Hydrophobic tails• Hydrophilic heads

• Some proteins have carbohydrate chains attached (glycoproteins)

• Function is to control what goes in or out of the cell and to aid in providing shape by latching on to the cytoskeleton

Burns, D., Cell Membrane, http://www.molecularstation.com

Cell Wall

• Found in Plants, Fungi, and Bacteria

• Outside of the plasma membrane

• Function: Protects cell and gives it structure

• Made of cellulose

Plant Cell, http://www.teacherthomas.com/

Cytoplasm

• Gel-like material which is found between the nucleus and cell membrane

• Function: Holds all the organelles in place and carries water, ionic solutions, proteins and sugars that will be used by the cell. It also helps to give the cell structure

http://www.scsc.k12.in.us/SMS/Teachers/Martin/cytoplasmreplacement.htm

Cytoskeleton

• Made of a network of filamentous proteins and microtubules

• Function: gives the cell structure

http://middletownhighschool.wikispaces.com/2010-11+Cytoskeleton++%26++Cytoplasm

Nucleus & Nucleolus• Nucleus is a specialized

organelle• Function is to hold DNA

and regulates cell activity

• Nucleolus is not membrane bound and is found inside the nucleus

• Function is to manufacture ribosomes

Centrioles

• Small structure found close to the nucleus of animal cells

• Usually found in pairs• Aids in cell division• Made of microtubules

in a 9+3 pattern

http://www.shayda.us/WebCT/AP1/AP1_Ex2_Materials/Centrioles.htm

http://rpdp.net/sciencetips_v2/L12B1.htm

Ribosome

• Small dense structures• Can be found free

floating or attached to endoplasmic reticulum

• Function: Aids in making proteins during translation and transcription

http://www.nigms.nih.gov/About/Budget/Statements/February29_2000.htm

http://hyperphysics.phy-astr.gsu.edu/hbase/biology/ribosome.html

Endoplasmic Reticulum

Smooth ER• Does not have ribosomes

attached• Both are found in plant and

animals cell, not in bacteria

Rough ER• Has attached ribosomes• Both are pathways used to

transport molecules such as proteins and lipids

http://micro.magnet.fsu.edu/cells/endoplasmicreticulum/endoplasmicreticulum.html

Golgi Apparatus

• Stacked membrane bound organelle

• Function: Packaging materials for export out of the cell by enclosing them in a vesicle and releasing them.

http://academic.pgcc.edu/~kroberts/Lecture/Chapter%203/membranous.html

Mitochondria• Considered the

“powerhouse” of the cell • Has its own DNA• Function: Used in cellular

respiration where the cell utilizes and produces energy for use in other cellular processes

• Makes ATP (Energy molecule)

Lysosome

• Small membrane bound organelle that is used in the “cleanup” of the cell

• Lysosomes contain enzymes that break down particles, digest them and release out of the cell through exocytosis

Levels of Organization • Cells are the basic building block of all living things• Cells make more cells that combine to make tissue which combines to

make organs. Organs combine to make organ systems that will combine to make the organism.

http://www.doctortee.com/dsu/tiftickjian/bio101/animal-structure.html

Different Types of Cells• There are many different types of cells that will combine to make tissue

How do cells differentiate?

• During embryonic formation stem cells are produced. Stem cells are specialized cells that can differentiate to become other types of cells or they can continue as a stem cell

• Stem cells are important because they can be manipulated to differentiate into any type of cell and they can generate new cells.

• Embryonic Stem Cells are found in the blastocyst during early embryonic development

http://www.allthingsstemcell.com/2009/04/human_embryonic_stem_cells/

http://robby.nstemp.com/photo6.html

What’s the Difference• Three basic types of stem cells:

– Totipotent: These cells have the greatest potential to become any type of cell. These are found around the 3rd day of germination of the fetus from the blastocyst and can actually form a complete organism

– Pluripotent: These cells can also form different tissue types but cannot form a complete organism. They can form the three cell layers: endoderm, mesoderm and exoderm and will give rise to the types of tissue that form from those layers

– Multipotent: These will usually form tissue from the area they originated (Stem cells in brain can form nerve cells)