Light Microscope Electron Microscope

Focuses a beam of electrons through the speciman.

Two typesTEM and SEM (transmission and scanning)

TEM: through a thin section of the speciman, used to view ultrastructure of cell.

SEM: Detailed surface, 3D image

To take cells apart WHY? To study the individual organelles Ultracentrifuge: separates cells according

to densities. Homogenization: disruption of cells, two

parts are created Pellet: larger structures at the bottom Supernatant: smaller parts of the cell

suspended in the liquid above the pellet. Repeated decantation collects smaller and

smaller components.

Prokaryotic: -no true nucleus, nucleoid(concentration

of DNA), no membrane -ex. Bacteria Eukaryotic: -true membrane organelles -has endomembrane system:

membranes in the cell that are related through direct physical continuity or by transferring segments in vesicles. These include nuclear envelope, endoplasmic reticulum, Golgi body, lysosomes, vacuoles and Plasma membrane.

Bound by nuclear envelope(phospholipid bilayer), porous

Contains DNA(hereditary information)Normally spread out in threadlike matrix

called chromatin. Condenses to form prior to

cell division. Chromosomes=DNA + Proteins called

Histones organize DNA, coiling it into

bundles called nucleosomes.

Chromosomes

Histones

Nucleus also contains nucleoli-concentrations of DNA in the process of manufacturing components of ribosome.

Serves as the site for the separation of chromosomes during cell division.

Subunits are manufactured in the nucleus and consist of RNA molecules and proteins.

Subunits- 60S and 40S move across the nuclear envelope and into the cytoplasm where they are assembled into a single 80S ribosome.

“S” stands for Svedbergs…which is the sedimentation coefficient…which is the velocity of sedimentation(think centrifuge!)

Assist in the assembly of amino acids into proteins.

Flattened stacks involved in the production of materials.

Cisternal Space-look like maze-like channels, closely associated with the nucleus.

Rough ER -has bound ribosomes attached Many specialized cells secrete proteins

(ex.insulin) -creates glycoprotein (secretory pro) by

attaching polysaccharide groups to polypeptides as they are assembled by the ribosomes.

Leave by secretory vesicles

Smooth ER -no ribosomes Carries out various activities including

the synthesis of lipids and hormones (sex hormones) and metabolism of carbs (Liver: glycogen into glucose and release into bloodstream.)

Especially in cells that produce these substances for export from the cell.

In liver cells, smooth ER is involved in the breakdown of toxins, drugs, and toxic by products from cell reactions.

Increasing drugs, causes an increase in the production of smooth er.

Individual can now intake more toxins and break them down.

This causes an increased tolerance!

Group of flattened sacs arranged like a stack of bowls

Modify and package proteins and lipids into vesicles-small, spherically shaped sacs that bud from the golgi apparatus.

(Center of manufacturing, gets deliveries from ER)

Vesicles will merge with plasma membrane and release their contents to the outside of the cell.

Vesicles form the Golgi apparatus that contain digestive hydrolytic enzymes.

Break down food, cell debris, and foreign invaders such as bacteria

Not present in plant cells Apoptosis: programmed cell death! Ex.

Rid of webbing between fingers and toes.

Break down various substances During the process, oxygen combines

with hydrogen to form toxic hydrogen perioxide!

The hydrogen perioxide is converted into water!

Common in liver and kidney cells(break down toxic substances) and in plant cells that are carrying out photosynthesis.

Carry out aerobic respiration Two membranes, inner makes up the

infolding called cristae. Matrix is the space within the cristae.

Folds increase surface area for respiration.

-made of three protein fibers of increasing diameter. (respectively)-involved in establishing the shape of or in coordinating movements of the cytoskeleton(the internal structure of the cytoplasm).

Made of the protein tubulin Provides support and motility for cell

activities. Found in the spindle apparatus (guide

the movement of chromosomes during cell division)

Found in the cilia and flagella (project from plasma membrane to provide motility for the cell).

Provide support for maintaining the shape of the cell.

Made of actin Involved in cell motility Found in muscle cells and phagocytes

Protrude from the cell membrane Make wavelike movements Flagella-long and few Cilia-short and many Ex. 1 flagella propels sperm, many cilia

line the respiratory tract and sweep away debris.

Structure –Both consist of microtubules arranged in a “9 + 2” array- nine pairs of microtubules arranged in a circle surrounding a pair of microtubules.

Microtubule organizing centers Centrioles –a pair, enclosed in a centrosome,

located outside of the nuclear envelope, gives rise to the microtubules that make up the spindle apparatus used during cell division.

Basal Bodies-found at the base of each flagellum and cilium and organize their development.

Centrioles and Basal bodies: both made of 9 triplets sets arranged in a circle.

Plant Cells lack centrioles…only lower plants (mosses and ferns) with motile sperm have flagella and basal bodies.

Found in plants, fungi, protists, and bacteria

Develop outside of plasma membrane Provide support of the cell Plants: cell wall made of cellulose(beta

glucose polysaccharide) Fungi: cell wall made of cellulose or

chitin (a modified polysaccharide that is different from cellulose in that one of the hydroxyl groups is replaced by a group containing nitrogen. )

Fluid filled, membrane bound organelles Transport Vesicles: -move materials between organelles or

between organelles and the plasma membrane.

Food Vesicles: -Temporary nutrient receptacles -merge with lysosomes, whose digestive

enzymes break down the food. Storage Vesicles: -in plants they store starch, pigments, and

toxic substances(nicotine)

Central Vacuole: -large bodies that occupy most of the

interior of some plant cells. -When filled, they exert turgor pressure

on the cell walls, which maintains the cells rigidity.

-store nutrients and carry out functions otherwise assumed by lysosomes in animal cells.

Contractile Vacuoles: -single-celled organisms collect and

pump excess water out of cells.

Anchor cells to one another and provide a pathway for cellular exchange.

Protein attachments between animal cells inside the plasma membrane

Have a disc-shaped structure from which protein fibers extend into the cytoplasm.

Hold together tissues that undergo a considerable stress

Ex. Skin or heart

Tightly stitched steams between animal cells.

Completely encircles each cell, preventing the movement of materials between cells

Characteristic of cells lining the digestive tract where materials are required to pass through cells (rather than intercellular spaces) to penetrate the bloodstream.

Narrow tunnels between animal cells that consist of proteins called connexons.

Connexons prevent the cytoplasm of each cell from mixing but allow the passage of ions and small molecules.

Allow cell communication through the exchange of materials or through the transmission of electrical impulses.

Narrow channels between plant cells A narrow tube of ER(desmotubile,

surrounded by cytoplasm and the plasma membrane, passes through the channel.

Material exchange through plasmodesmata occurs through the cytoplasm surrounding the desmotubule.

This theory states that eukaryotic cells originated from a symbiotic partnership of prokaryotic cells.

http://www.sumanasinc.com/webcontent/animations/content/organelles.html

This is a theory of how Eukaryotic organisms evolved from Prokaryotic cells.

Reminder: Prokaryotic differences:

Lacks a true nucleus; nucleoid Simpler in structure, has few organelles Has many ribosomes Rigid cell wall with an outer capsule Can have flagella, pili(for attachment) Due to simplicity, limits metabolic activities Smaller…so limits the amount of genetic

material possible in the prokaryote!

How did the endomembrane structures form that were not there… theory that the plasma membrane infolded.

NEXT…ENDOSYMBIOTIC THEORY This theory believes that the mitochondria

and chloroplasts were once formally small prokaryotes living inside a larger prokaryotic cell that served as the host.

The theory hypothesizes that mitochondria evolved from aerobic heterotrophic prokaryotes. Chloroplasts evolved from photosynthetic prokaryotes. They became endosymbionts(living inside another cell)

They gained entry to the host cell as undigested prey or parasite.

It became mutually beneficial! If you were a heterotrophic prokaryote, a

“chloroplast” would provide food! If you were an anerobic prokaryote, a

“mitochondria” would provide more ATP. As they became more interdependent, the

endosymbionts and the host would become inseparable.

This is a merger of lineages!! Very different from traditional evolutionary divergence. (cladogenesis)

1)they are the same size as Eubacteria 2) The inner membranes of mitochondria

and chloroplasts have several enzymes and transport systems similar to prokaryotes.

3) they also reproduce through binary fission(same as Pro)

4)if their ribosomes are sliced open and studied, they resemble prokaryotes more than a eukaryotes.

5) Mitochondria and chloroplasts contain circular DNA like prokaryotes.