Post on 04-Jan-2016
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Cells
Some Random Cell Facts
• The average human being is composed of around 100 Trillion individual cells!!!
• It would take as many as 50 cells to cover the area of a dot on the letter “i”
Discovery of Cells• 1665 Robert Hooke
– discovered cells while looking at a thin slice of cork.– described the cells as tiny boxes or a honeycomb– thought that cells only existed in plants and fungi
Anton van Leuwenhoek
• 1673- Used a handmade microscope to observe pond scum & discovered single-celled organisms
• He called them “animalcules”
• He also observed blood cells from fish, birds, frogs, dogs, and humans
• Therefore, it was known that cells are found in animals as well as plants
• 1838 Matthias Schleiden– concluded that all plant parts are made of
cells
• 1839 Theodor Schwann, – stated that all animal tissues are composed of
cells.
• 1858- Rudolf Virchow– concluded that cells must arise from preexisting cells.
The Cell Theory Complete
• The 3 Basic Components of the Cell Theory were now complete:
1. All organisms are composed of one or more cells.
2. The cell is the basic unit of life in all living things.
3. All cells are produced by the division of preexisting cells.
Can you design the “best cell” shape?
• What do cells need?
• How could you measure if this need is met?
• How could you compare different designs?
2 Basic Types of Cells1) Prokaryotic examples ???2) Eukaryotic examples????
Plasma membrane• Structure
– Main component is phospholipids that are arranged in a double layer (bilayer)
– Has scattered proteins within the phospholipids
Function of the Plasma Membrane
• Regulate what gets into or leaves the cell
Nucleus• Structure
– Surrounded by a double membrane
– This “nuclear membrane” has pores
• Function– Holds the
chromosomes (DNA) and the nucleolus
Nuclear envelope
• Double layer of membrane
• Has pores
• Surrounds the nucleus
• Regulates what goes into and out of the nucleus
Chromosomes
• Structure– String-like
structures in the nucleus made of DNA and protein
• Function – Contain your genes
Nucleolus • Structure
– Small dark structure in the nucleus
• Function– Produce ribosomes
Ribosomes
• Small structures (NOT made of membrane)
• Make proteins
Central Vacuole
• Structure– LARGE sac made
of membrane– Found in center of
plant cells
• Function– Stores chemicals
and water
Smooth Endoplasmic Reticulum• Structure
– Canals and tubes made of membrane
• Function– Makes lipids (oils,
phospholipids, steroids)
– Detoxifies poisons
Rough Endoplasmic Reticulum
• Structure– Canals and tubes
made of membrane– Have ribosomes
attached to the outside
• Function– Transport materials
in the cell– Make proteins
(those exported from the cell, those found on the plasma membrane, those found in lysosomes)
Golgi Apparatus• Structure
– Stacks of membrane sacs
– has a receiving end (from ER) and a shipping end
• Function– Chemically modifies
substances– Packages material for
transport out of the cell or to other locations within the cell
Vesicles • Structure
– Small membrane “bubbles” that bud off the ER or Golgi
• Functions– Transport materials
to new locations
Lysosomes • Structure
– Sacs of membrane that contain hydrolytic enzymes
– -found mostly in animal cells
• Function– Use enzymes to
break down old organelles
– In white blood cells are used to destroy bacteria
Mitochondria
• Structure– Surrounded by a
double membrane• Folds found on the
inside
• Function– Cellular Respiration
• Converts energy in sugars into the energy of ATP molecule
Chloroplasts
• Structure– Surrounded by a
double layer of membrane
• Disks found inside
• Function – Convert solar
energy into chemical energy (food)
– Site of photosynthesis
Perioxisome • Structure
– Small membranous sac
• Function – Some reactions
occurring here produce H2O2 (toxic)
• So, it also contains an enzyme (catalase) that converts this to water and oxygen gas
Cell Wall• Structure
– Found outside the plasma membrane
– Plant made of cellulose
• Function– Give support to
certain cells (plant)– Does NOT
determine what can get into/out of the cell
Cytoskeleton
• Structure• Made of protein fibers
– Microtubules• Hollow tube
– Microfilaments• Small rods
– Intermediate filaments
• Function– Give the cell shape– Help to move
organelles around the cell
Fig. 4-17
Microfilament
Actin subunit
7 nm
Intermediate filament
Fibrous subunits
10 nm
Microtubule
Tubulin subunit
25 nm
Nucleus
Nucleus
Centrioles
• Structure– Made of rings of
microtubules– Found in pairs that
lie at right angles • Look similar to a
pair of barrels
• Function– Found in animal
cells– Help organize the
tubulin required for cell division
Cilia• Structure
– Microtubules that extend from the cell (still covered by the plasma membrane)
– Short and many of them
• Function– In single-celled
organisms, they can move the organism from place to place
– If anchored in place, can set up a current, moving fluid across the surface of a cell
Fig. 4-1c
Fig. 4-18a
Cilia
http://www.youtube.com/watch?v=YHb2JaujIPo&feature=related&safety_mode=true&persist_safety_mode=1
Flagella Structure • Same as cilia, but
are longer and there are just a few of them
• Prokaryotes also have them– Not made of
microtubules
Function • Move the cell within its
environment
Fig. 4-20
EXTRACELLULAR FLUID
Microfilaments
Collagen fiber
Connectingglycoprotein
Integrin
Plasmamembrane
Glycoproteincomplex with longpolysaccharide
CYTOPLASM
How large can cells get?-depends on how efficiently they can get nutrients in and wastes out
30 µm
30 µm 10 µm
10 µm
Surface areaof one large cube= 5,400 µm2
Total surface areaof 27 small cubes= 16,200 µm2
Fig. 4-21
Tight junctions
Anchoring junction
Gap junctions
Plasma membranesof adjacent cells
Extracellular matrix
Fig. 4-22
Vacuole
Wallsof twoadjacentplant cells
Cytoplasm
Plasma membrane
Plasmodesmata
cell wall
A
BE
CD (CONTAINING DIGESTIVE ENZYMES)
AC
AD
C
D
E
AB
BD
B
AEBC
A
B
C
E
AB
AC
AD
AE
BC
BD
BE
D
A
B
C
D