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Shaan Gurnani Organelles Project

Page history last edited by PBworks 16 years, 5 months ago

~ Shaan Gurnani's Organelles Project ~

~ Freshmen Biology - Mr. De - Period 6.8 ~

~ November 2007 ~

Cells and Organelles

Introduction:

Discovery of the Cell

- made possible by the microscope

- 1665 - Robert Hooke examined cork (named ‘little boxes’ cells)

- 1673 - Anton von Leewenhoek saw live cells

- 1838 - Matthias Schleiden said plants are made of cells

- 1838 - Theodor Schwann said animals are made of cells

- 1855 - Rudolf Virchow said cells come from other cells

Cell Theory

1.)All living things are composed of cells.

2.) Cells are basic unit of structure and function in an organism.

3.) Cells come from the reproduction of existing cells

A cell is very small, basic unit of life that is found in all functional organisms and is often called the building block of life. There are two main types: prokaryotic and eukaryotic.

Cell Diversity

- cells come in all shapes and sizes, specific to their function (> 200 different types)

Size:

- plant and animal cells, 10-50 micrometers

- bacterial cells, 0.2 micrometers

- as a cell grows, its volume increases faster than its surface area (think balloon) so…not enough surface (area) to take in nutrients or remove wastes

- cell will die if it could just keep enlarging – so it divides to make two more cells

Shape:

- shape of cell is important to its job in the body, i.e. long nerve cell, flat skin cells, globular white blood cell

Prokaryotic: far more basic, no nucleus, DNA is in a ring, lacking other membrane bound organelles, usually found in bacteria
Eukaryotic: more complex, have membrane bound nucleus to protect DNA, have membrane bound organelles (seperate parts with unique functions), usually found in plants and animals

A diagram showing the anatomy (all of the parts) of an animal cell:

<-- picture from: http://micro.magnet.fsu.edu/cells/animals/images/animalcell.jpg

A diagram showing the anatomy (all of the parts) of a plant cell:

picture from http://www.ualr.edu/botany/plant3.gif

One of the Main/Major differences between an animal cell and a plant cell is that plant cells have a cell membrane and a cell wall while animal cells only have a cell membrane. Also, Plant cells also have chloroplasts a central vacuole. Animal cells have a flagellum, a lysosome, and a centriole.

An organelle is a specialized part of a cell. Each one has a specific function. All organelles work together as a unit to maintain cell life.

Outline and basic ideas:

Extracellular fluid - fluid in external environment of cell
Flagellum/Cilia (my choice) - propel cells through environment, move materials over cell surface
Endomembrane system - group of several related organelles (following)
Plasma membrane - cell membrane, protects cell from outside environment, selectively permeable
Nuclear membrane - membrane of the nucleus, the "brain" of the cell
endoplasmic reticulum (ER) - rough ER - prepares protein for export, smooth ER: makes steroids, regulates calcium levels, breaks down toxic substances
Golgi Apparatus - processes and packages substances produced by the cell
Vacuole - storage compartments for enzymes, waste products
Cytoskeleton - network of long protein strands
Mitochondria - energy "powerhouse"; transfer energy from organic compouds to ATP
Ribosome - makes proteins
Exocytosis/Endocytosis - import and export department of the cell
Plastid (Chloroplast) - used by plants for photosynthesis

Extracellular fluid (ECF)

outside of cell fluid

This is all body fluid outside of cells
it is 1/3 of the body's liquid, 1/5 of body weight
it is found in blood and in muscular and other body tissues
- within the body, this fluid, such as blood, is maintained at a certain pH (7.4) by buffers
It is subdivided into three different parts:
- Interstitial Fluid - surrounds cells; 3/4 ECF
- Plama - part of blood; 1/4 ECF
- Transcellular fluid - part of digestive juices, mucus, and more

Flagellum/Cilium (my choice)

plural: Flagella/Cilia
make up a group of organelles called Undulipodium
- (notice that undulate is part of the group name)
they are both very similar
projections from the cell body
are used for transportation (assist in movement)
made up of microtubules
Differences: (in function)
Flagella:
- "whip-like" action to move the whole cell
- long and slender
- used to propel unicellular or small multicellular organism
- for example, allow sperm to move
- usually found in animal and protist cells, not plant cells
- can be more than one
Cilia:
- waving action
- small hair-like and present in large numbers
- moves substances across the cell
- many
- may also be used as a sensory organ

Shown above: Escherichia coli bacterium with flagella

Picture from: http://www.monash.edu.au/news/assets/images/micro-robot.jpg

Picture from: http://sun.menloschool.org/~tbuxton/cells/f/animals/cilia_flagella/cilia.jpg

Endomembrane system:

within eukaryotic cells
this system is a collection of many membranes that create/seperate the various organelles
they work together in the synthesis (production), storage and export of molecules
the system includes the following organelles, which be covered in length following this:
- the plasma membrane -
  - another term for the cell membrane -
  - it is formed by a phospholipid bi-layer
  - it seperates the cell from its environment
  - regulates what can go in and out of the cell -
  - (it is selectively permeable) -
  - (this includes nutrients, waste, etc.)
- the nuclear membrane -
  - also known as the nuclear envelope -
  - is a membrane around the nucleus
  - that encloses and protects genetic information
- Endoplasmic reticulum (ER) -
  - synthesis (production) and transport organelle
  - extension of the nuclear membrane
- Golgi apparatus
  - packaging and delivery system for molecules
- vacuoles
  - storage units in cells

The above image is::: a diagram that shows the various parts (organelles) of the endomembrane system in a eukaryotic cell.

Above picture is from::: http://upload.wikimedia.org/wikipedia/commons/thumb/0/00/Endomembrane_system_diagram.svg/612px-Endomembrane_system_diagram.svg.png

The Plasma Membrane:

part of the endomembrane system
also known as the cell membrane
Structure:
it is formed by a phospholipid bi-layer
- obviously, made up of several phopholipids
- As you can see in the diagram below,
- the hydrophobic fatty acids (the tails) are non-polar (water-fearing) and
- the hydrophillic head groups are polar (water loving - attracted to water)
- - This diagram shows the hydrophillic head and the hydrophobic tail of a phospholipid.
  - The phospholipids form arrange in the following particular orientation because:
  - there is H20 (polar) on the inside and H20 (polar) on the outside
  
  - the fatty acids (tails) are hydrophobic and therefore face each away from the water and towards each other (the tails are attracted to each other from a phospholipid bi-layer)
  
  - the head groups are hydrophillic and therefore face the water on the inside and the water on the outside
- Phospholipid bilayer is therefore a double layer of phospholipids
- a phopholipid are a type of lipids
  http://www.fz-juelich.de/inb/inb-1/datapool/page/28/Figure1-500.jpg
- ok so the following picture is a section of a phospholipid bilayer which forms the cell membrane...the blue things are proteins, they are membrane channels which allow things, such as water and nutrients,

http://www.sophion.dk/sophion/Membrane-channels3.jpg
it seperates the cell from its environment
- (it is selectively permeable)
regulates what can go in and out of the cell -
(this includes nutrients, waste, etc.)

A unique feature about the cell membrane is that:
A cell membrane, unlike a cell wall (which is rigid), is fluid: it can move, it is flexible, and things can go through it
This is all according to the Fluid Mosaic Model
-         Fluid Mosaic Model

o       lipid bilayer moves continuously and behaves like a liquid

o       mosaic of proteins constantly changes as phospholipids move around and flip
which was designed/discovered by S. J. Singer and Garth Nicolson
the following image shows the cell membrane with all of its parts:
(the phospholipid bilayer and several different types of proteins)

http://en.wikipedia.org/wiki/Image:Cell_membrane_detailed_diagram.svg

The Nuclear Membrane:

The following image is a diagram of a nucleus in a human cell, from wikipedia.org: http://en.wikipedia.org/wiki/Image:Diagram_human_cell_nucleus.svg
part of the endomembrane system
the nuclear membrane -
- in eukaryotic cells
- also known as the nuclear envelope -
- is a double membrane (outer and inner)
- around the nucleus
- that encloses and protects genetic information
- it seperates what is within the nucleus from the cytoplasm
- there are several nuclear pores, marked on the diagram
- these are used to transport substances between the nucleus and the cytoplasm
- (allows materials to go into and out of the nucleus)
- Perinuclear space (space between the two membranes that composes the nuclear envelope)
- Outer membrane contains endoplasmic reticulum
a nucleus is
- an organelle in eukaryotic cells
- the brain, or central control system, of the cell
- it contains all of the genetic information required (DNA)

Endoplasmic reticulum (ER):

http://www.hhmi.org/askascientist/images/cell.gif

This image show location of the ER within the cell.

Endoplasmic Reticulum (ER)
- part of the endomembrane system
- an organelle that is found in all eukaryotic cells
- network of many parts (tubes and vesicles)
- structure is similar to that of the plasma (cell) membrane
- intracellular highway, moves things through cell
- two parts/types

Rough ER

covered in ribosomes (therefore it is rough)

(the function of ribosomes is the production of proteins)

synthesizes (produces) proteins

transports proteins

Smooth ER

connected to the nuclear envelope

Synthesizes steroids (thyroid gland)

synthesizes lipids

Regulation of calcium levels in muscle cells

breakdown of toxic material by liver

usage of carbs and {calcium] for energy

http://computer.act.ac.th/webproject5_2548/st/m53/division/Endoplasmic%20reticulum.jpg

Golgi Apparatus

Part of the Endomembrane system
in eukaryotic cells
discovered by an Italian physician named Camillo Golgi in 1898
basically it processes and packages,, materials (cell products such as macromolecules)
- and prepares for export out of cell through exocytosis
- (important for releasing materials from the cell)
you can think of it as a mail center:
- preparing, processing, and packaging items
- to be sent out (of the cell, out of the post office) to another place
Structure:
six to seven flattened, membrane-bound sacs called cisternae
located near the nucleus

The following image is a cell with the golgi apparatus label. I got the image from http://sun.menloschool.org/~cweaver/cells/c/golgi/cell.jpg

a closer look at strucutre, location, and parts of the golgi apparatus:: from http://micro.magnet.fsu.edu/cells/golgi/images/golgifigure2.jpg

Vacuole:

last part of the endomembrane system
eukaryotic cells
found in most plant cells and in some animal cells
are big in plant cells and small in animal cells
sac bound by membrane
small storage compartments in cell
plays a role in releasing/exporting waste/not needed products out of the cell
maintains turgor pressure which is important to keep plant cells rigidy and have them not wilt

First image (left) is a cartoon image: from::: http://www4.alief.isd.tenet.edu/cahowe/PreAPBio/Projects/Cell_files/slide0013_image053.jpg

Second image (right) is a microscopic image: from::: http://www.cellsalive.com/cells/vacuole.htm

Cytoskeleton:

network of long protein strands located in the cytosol
not surrounded by membranes
made of microfilaments and microtubules
- Microfilaments
  - protein threads of actin
  - cell movement and muscle contraction
- Microtubules (conveyor belts around cell that move organelle around
  - longest strands of cytoskeleton
  - make up spindle fibers (role in mitosis and meiosis)t

MTOC - Microtubule Organizing Center
- usually near nucleus
- a structure from where microtubules emerge
- is basically a centrosome
- microtubules grow out and connect to chromosomes during interphase (mitosis
above images were taken from the following website:
http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/part1/microtub.htm

I believe that in the left picture, the blue represents either the nucleus or the MTOC. Similarily, in the picture to the right, I believe that the purple sphere is the MTOC and the gold/yellow represents microtubules.

left picture from: http://content.answers.com/main/content/wp/en-commons/thumb/7/70/300px-FluorescentCells.jpg

right picture from: http://www.immediart.com/catalog/images/big_images/SPL_6_P780110-Fibroblast_cells_showing_cytoskeleton.jpg

Mitochondria:

- Mitochondria

o powerhouse of cell, uses ATP for energy, numerous in muscle cells and liver cells, have their own DNA

o two membranes

§ outer membrane is boundary

§ inner membrane is cristae, highly folded for increased surface area for reactions

picture from http://www.cartage.org.lb/en/themes/sciences/zoology/AnimalPhysiology/Anatomy/AnimalCellStructure/Mitochondria/mitochondria.jpg

Ribosomes

do not have a membrane
made/consists of both RNA and proteins parts
made within nucleolus
can be free floating or attached to rough ER (Endoplasmic Reticulum)
make proteins, in a function called translation
site of protein synthesis (free- within cell; RER (Rough Endoplasmic Reticulum) – exported out of cell)

Right image, ribosome protein from: http://publications.nigms.nih.gov/insidethecell/images/ch2_ribosome_proteinbig.jpg

Exocytosis/Endocytosis

This animation shows exocytosis. http://academic.brooklyn.cuny.edu/biology/bio4fv/page/exocy.htm

Exocytosis:

http://www.linkpublishing.com/exocytosis5.jpg

The following picture shows both exocytosis and endocytosis:

endocytosis (import) is on the top and exocytosis (export) is on the bottom of the diagram

http://www.accessexcellence.org/RC/VL/GG/ecb/import_export.html

The import/export "department" of the cell:

Endocytosis:

endo means "in"
cells import materials (nutrients, etc.) from the external environment using Endocytosis
as you can see in the above image, the cell captures the material in a vesicle (like a bubbles) and pinches it off from the cell (plasma) membrane

Exocytosis:

opposite of endocytosis
"exo" is similar to exit and means leave
this is a process for exporting, or removing, substances such as waste and cell products from the cell
a vesicle (bubble, holder) is created and it contains the substance
it moves towards the membrane and eventually fuses with it
the animation and the second image are both very good examples of exocytosis

Plastid (Chloroplast):

<-- picture from http://biology.nuim.ie/graphics/chloropic_000.gif

basic model of the plastid

found only in plant cells
in charge of Photosynthesis, a process by which plants convert light energy into plant energy
the reactants are CO2, H20 and energy from sunlight
the products are glucose and oxygen
also responsible for storage of starch
surrounded by double membrane
have their own DNA
can store starch, fats, or pigments
chloroplast convert solar energy to chemical energy
contains thylakoids – flattened membranous sacs where photosynthesis occurs
a granum is a stack of thylakoids
stoma is the aqueous space
Chlroplasts In an actual plant cell:
http://en.wikipedia.org/wiki/Image:Chloroplasten.jpg