C HAPTER 6 A Tour of the Cell

C H. 6 W ARM -U P 1.What are the 2 main types of cells? Which Domains do they consist of? 2.List 3 ways that eukaryotes differ from prokaryotes.

C H. 6 W ARM -U P 1.How is the size of a cell related to its function? 2.Name 5 organelles or cell structures and their function.

C H. 6 W ARM -U P Animal CellPlant Cell Compare and contrast Animal vs. Plant Cells

C H. 6 W ARM -U P What is the structure & function of: 1. Microtubules 2. Microfilaments 3. Intermediate filaments

C H. 6 W ARM -U P What is the function of: 1. Plasmodesmata 2. Gap junctions 3. Tight junctions 4. Desmosomes

Y OU M UST K NOW Three differences between prokaryotic and eukaryotic cells. The structure and function of organelles common to plant and animal cells. The structure and function of organelles found only in plant cells or only in animal cells.

E ARLY C ONTRIBUTIONS Robert Hooke - First person to see cells, he was looking at cork and noted that he saw "a great many boxes. (1665) Anton van Leeuwenhoek - Observed living cells in pond water, which he called "animalcules" (1673)

Theodore Schwann - zoologist who observed tissues of animals had cells (1839) Mattias Schleiden - botanist, observed tissues of plants contained cells ( 1845) Rudolf Virchow - also reported that every living thing is made of up vital units, known as cells. He predicted that cells come from other cells. (1850 )

T HE C ELL T HEORY 1. Every living organism is made of one or more cells. 2. The cell is the basic unit of structure and function. It is the smallest unit that can perform life functions. 3. All cells arise from pre-existing cells. *Why is the Cell Theory called a Theory and not a Fact?

T HREE F EATURES OF C ELLS 1. Plasma (Cell) Membrane - serves as a barrier, regulates what enters and leaves the cell * We go into much more detail in the next chapter on how this works*

2. G ENETIC M ATERIAL 1. provides cellular "blueprint" that controls the functions of the cell 2. In the form of DNA (Deoxyribonucleic acid) 3. DNA is universal for all cells, an all living things - evidence of common ancestry 4. Chromatin is the complex of proteins and DNA, it condenses into chromosomes before cell division *We will go into much greater detail in a later unit on GENETICS*

3. C YTOPLASM ( CYTOSOL ) 1. Located within the plasma membrane 2. contains water, salts, and other chemicals 3. organelles float within this jelly-like substance Microtubules and filaments support the inner structure of the cell

H OW W E S TUDY C ELLS Biologists use microscopes and the tools of biochemistry to study cells

C ELLS ARE ALWAYS SMALL, HOW SMALL DEPENDS ON THE TYPE OF CELL C ELLS CAN COME IN A VARIETY OF SHAPES

Single Cheek Cell - at different illuminations

F IGURE 4.3

Size range of cells Note that light microscopes can not magnify as well as electron microscopes

C ELL S IZE AND S CALE Scale of the Universe: rse_2012

surface area to volume ratio Cells must be small to maintain a large surface area to volume ratio Large S.A. allows  rates of chemical exchange between cell and environment

A NIMAL S URFACE A REA E XAMPLE (A NIMAL ): Small Intestine: highly folded surface to increase absorption of nutrients Villi Villi: finger-like projections on SI wall Microvilli Microvilli: projections on each cell

F OLDS  V ILLI  M ICROVILLI

P LANT S URFACE A REA E XAMPLE (P LANT ): Root hairs Root hairs : extensions of root epidermal cells; increase surface area for absorbing water and minerals

Light Microscopy (LM) vs. Electron Microscopy (EM)

C OMPARISONS OF S COPES Visible light passes through specimen Refracts light so specimen is magnified Magnify up to 1000X Specimen can be alive/moving Color Focuses a beam of electrons through/onto specimen Magnify up to 1,000,000 times Specimen non-living and in vacuum Black and white Light Electron

E LECTRON M ICROSCOPY 2-D Creates a flat image with extreme detail Can enhance contrast by staining atoms with heavy metal dyes 3-D Used for detailed study of surface of specimen Gives great field of depth Transmission (TEM) Scanning (SEM)

Studying cell structure & function 1.Cell fractionation - take apart cells, separate major organelles 2.Ultracentrifuge - applies force 1 million times the force of gravity to separate further the cell organelles with the most dense at the bottom

2 T YPES OF C ELLS : 1. Prokaryotes : Domain Bacteria & Archaea 2. Eukaryotes (Domain Eukarya): Protists, Fungi, Plants, Animals

A P ROKARYOTIC C ELL ( BACTERIA )

P ROKARYOTE C ELLS no membrane bound nucleus, chromosomes grouped together in an area called the "nucleoid" no membrane bound organelles smaller than eukaryotes Include the domains Bacteria and Archaea

have cell wall and cell membrane, some have a capsule on the outside ribosomes make protein consist of bacteria and archaebacteria Appendages include: fimbriae/pili, flagella *pili are usually longer and fewer than fimbriae, both function for attachment and recognition of host cells (or (sexual reproduction)

F IGURE 4.4 A

E. coli

E UKARYOTES has a membrane bound nucleus has membrane bound organelles in cytoplasm Organelles perform specific functions much larger than prokaryotes Organisms within the animal, plant and fungi kingdoms are all eukaryotes

P ROKARYOTE V S. E UKARYOTE “before” “kernel” No nucleus DNA in a nucleoid Cytosol No organelles other than ribosomes Small size Primitive i.e. Bacteria & Archaea “true” “kernel” Has nucleus and nuclear envelope Cytosol Membrane-bound organelles with specialized structure/function Much larger in size More complex i.e. plant/animal cell

K NOW T HIS C HART ! CharacteristicProkaryotic CellsEukaryotic Cells Plasma MembraneYes Cytosol with organelles Yes RibosomesYes NucleusNoYes Size1 um- 10 um10 um- 100 um Internal membranes Noyes

C ELL ORGANELLES

N UCLEUS Function: control center of cell Contains DNA Surrounded by double membrane ( nuclear envelope ) Continuous with the rough ER Nuclear pores : control what enters/leaves nucleus Chromatin : complex of DNA + proteins; makes up chromosomes Nucleolus : region where ribosomal subunits are formed

N UCLEUS Contains DNA Function: control center of cell Surrounded by double membrane ( nuclear envelope ) Continuous with the rough ER Nuclear pores : control what enters/leaves nucleus Chromatin : complex of DNA + proteins; makes up chromosomes Nucleolus : region where ribosomal subunits are formed

R IBOSOMES Function: protein synthesis Composed of rRNA + protein Large subunit + small subunit Types: 1. Free ribosomes : float in cytosol, produce proteins used within cell 2. Bound ribosomes : attached to ER, make proteins for export from cell

E NDOMEMBRANE S YSTEM : Regulates protein traffic & performs metabolic functions

E NDOPLASMIC R ETICULUM (ER) Network of membranes and sacs Types: 1. Rough ER : ribosomes on surface Function: package proteins for secretion, send transport vesicles to Golgi, make replacement membrane 2. Smooth ER : no ribosomes on surface Function: synthesize lipids, metabolize carbs, detox drugs & poisons, store Ca 2+

E NDOPLASMIC R ETICULUM (ER)

G OLGI A PPARATUS Function: synthesis & packaging of materials (small molecules) for transport (in vesicles); produce lysosomes Series of flattened membrane sacs (cisternae) Cis face : receives vesicles Trans face : ships vesicles

L YSOSOMES Function: intracellular digestion; recycle cell’s materials; programmed cell death (apoptosis) Contains hydrolytic enzymes

V ACUOLES Function: storage of materials (food, water, minerals, pigments, poisons) Membrane-bound vesicles Eg. food vacuoles, contractile vacuoles Plants: large central vacuole -- stores water, ions

M ITOCHONDRIA Function: site of cellular respiration Double membrane: outer and inner membrane Cristae : folds of inner membrane; contains enzymes for ATP production; increased surface area to  ATP made Matrix : fluid-filled inner compartment

C HLOROPLASTS Function: site of photosynthesis Double membrane Thylakoid disks in stacks (grana); stroma (fluid) Contains chlorophylls (pigments) for capturing sunlight energy

E NDOSYMBIONT THEORY Mitochondria & chloroplasts share similar origin Prokaryotic cells engulfed by ancestors of eukaryotic cells Evidence: Double-membrane structure Have own ribosomes & DNA Reproduce independently within cell

P ROKARYOTE VS E UKARYOTE C ELLS Endosymbiosis theory: All organelles seem to share many properties with bacteria. Lynn Margulis proposed endosymbiont hypothesis: that organelles derived from ancient colonization of large bacteria (became the eukaryotic cell) by smaller bacteria (became the mitochondria, chloroplast, etc.) Symbiosis = "living together". *Mitochondria & Chloroplasts have their own DNA Animation at Microbiological Concepts

P EROXISOMES Functions: break down fatty acids; detox alcohol Involves production of hydrogen peroxide (H 2 O 2 )

C YTOSKELETON : NETWORK OF PROTEIN FIBERS Function: support, motility, regulate biochemical activities

MicrotubulesMicrofilaments Intermediate Filaments Protein = tubulin Largest fibers Shape/support cell Track for organelle movement Forms spindle for mitosis/meiosis Component of cilia/flagella Protein = actin Smallest fibers Support cell on smaller scale Cell movement Eg. ameboid movement, cytoplasmic streaming, muscle cell contraction Intermediate size Permanent fixtures Maintain shape of cell Fix position of organelles 3 T YPES OF C YTOSKELETON F IBERS :

MicrotubulesMicrofilaments Intermediate Filaments 3 T YPES OF C YTOSKELETON F IBERS :

Centrosomes : region from which microtubules grow Also called microtubule organizing center Animal cells contain centrioles

C ILIA & F LAGELLA Flagella: long and few; propel through water Cilia: short and numerous; locomotion or move fluids Have “9+2 pattern” of microtubules

E XTRACELLULAR M ATRIX (ECM) Outside plasma membrane Composed of glycoproteins (ex. collagen) Function: Strengthens tissues and transmits external signals to cell

I NTERCELLULAR J UNCTIONS (A NIMAL CELLS ) Tight junctions : 2 cells are fused to form watertight seal Desmosomes : “rivets” that fasten cells into strong sheets Gap junctions : channels through which ions, sugar, small molecules can pass

P LANT C ELLS Cell wall: protect plant, maintain shape Composed of cellulose Plasmodesmata : channels between cells to allow passage of molecules

Plant Cells OnlyAnimals Cells Only Central vacuolesLysosomes ChloroplastsCentrioles Cell wall of celluloseFlagella, cilia Plasmodesmata Desmosomes, tight and gap junctions Extracellular matrix (ECM)

Parts of plant & animal cell p

H ARVARD CELL VIDEO