Transcript lect 2 CELL structure

The Cell Theory
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4/9/2015
Further observations in the 1800’s by
Schleiden and Schwann
Fatchiyah, Ph.D. JB UB
http://members.tripod.com/blustein/Schwann_Cells/schwann_cells.htm
Pengertian Sel
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Sel merupakan satuan struktural dan
fungsional terkecil dari makhluk hidup.
Sel melakukan semua proses kehidupan.
Penemuan Pertama Sel
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Robert Hooke, ilmuwan
Ingris(1665)  sel
gabus dalam buku
Micrographia
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Anton van
Leeuwenhoek, 1674
(pembuat lensa dari
Belanda)  sel hidup
dalam air
Penemu Sel
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Mathias Schleiden (ahli tumbuhan dari
Jerman), 1838  semua tanaman terdiri
atas sel
Theodor Schwann (zoologis dari Jerman),
1839  sel merupakan unit struktur terkecil
dari makhluk hidup
Rudolp Virchow (Jerman), 1855  sel
berasal dari sel yang sudah ada (TEORI SEL)
Teori Sel
Teori Sel menyatakan bahwa :
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Semua makhluk hidup tersusun atas satu
atau lebih sel
Sel merupakan satuan struktural terkecil dari
makhluk hidup, sel melakukan semua proses
kehidupan
Sel berasal dari sel yang lain
What are cells?
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Fundamental, replicating units of living
organisms.
Machines with complex regulation and
behaviors; based on networks of chemical
reactions called pathways.
They carry the information needed to
reproduce themselves.
All cells based on molecules of a limited
number of classes
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DNA
RNA
Proteins
Ph.D. JB UB
“etcetera” (Lipids, Fatchiyah,
Carbohydrates,
Metabolites)
Cell structure and function
The components of a cell
The cell membrane: how materials get into
and out of the cell
Are all cells the same?
The life and death of a cell
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Fatchiyah, Ph.D. JB UB
Trillions of cells in the human body
All have DNA, organelles and membranes
Cells are very different in size, shape and
activity- and how they are arranged
in tissues
Do cells mimic organ systems, or do organ
systems mimic cells?
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Fatchiyah, Ph.D. JB UB
Bacterial cell
Plant cells
Animal cells
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Observe the “composite cell” (no cell looks
like this)
Cells are capable of:
reproducing themselves
synthesizing the organelles they need
metabolism
eliminating waste materials
regulating movement of materials into
and out of themselves
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Fatchiyah, Ph.D. JB UB
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Fatchiyah, Ph.D. JB UB
What is so special about the cell membrane?
Cell is in an aqueous environment
phospholipid membrane provides a
“selectively permeable” barrier
Water and carbon dioxide move easily
Water-soluble molecules do not
How DO these molecules get through the
membrane?
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Membrane-bound proteins
Transport proteins or channels for watersoluble molecules
“Signal transduction”- cell receives a signal
and responds to it
Adhesion molecules
Each type of protein has a specific function
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Structure and function of organelles
I.
Protein synthesis
Endoplasmic reticulum
Rough- site of protein synthesis and
processing
Smooth- lipid metabolism and detoxification
Ribosomes- site of the initial steps of protein
synthesis
Golgi apparatus- the “UPS” of the cell
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Fatchiyah, Ph.D. JB UB
II. Metabolism
mitochondria- where most ATP is made
mitochondria have their own DNA and
ribosomes
some cells have more than others
III. The by-products of metabolism
lysosomes contain enzymes that break
down large molecules, recycle old
organelles
peroxisomes- specialized for detoxification
in liver and kidney cells
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IV. Cytoskeleton- support and movement of
the cell
Microfilaments- (actin, myosin) involved in
cell division, cell movement
arrangement is significant in muscle cells
Microtubules (tubulin)
found in centrioles, flagella, cilia
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The nucleus and its contents
Contains chromatin (material that makes up
chromosomes)
Nucleoli- ribosome synthesis
Specialized nuclear membrane:
double membrane with nuclear pores
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Features of the cell membrane
Semi-permeable
remember: membrane is phospholipid
bilayer, with embedded and peripheral
proteins
Movement of materials across membrane is
regulated:
size of molecule
solubility in water or lipid
concentration gradient
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What is a concentration gradient?
Molecules move spontaneously, from areas
where they are highly concentrated to
where they are less concentrated
Equilibrium: molecules are uniformly distributed
Molecules tend to seek equilibrium, i.e., diffuse
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Diffusion across a cell membrane occurs if:
There is a concentration gradient (more of the
substance on one side of the membrane
than the other)
The membrane is permeable to the substance
No energy is required for diffusion
Examples: oxygen and carbon dioxide
why can they diffuse through the membrane?
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Fatchiyah, Ph.D. JB UB
Facilitated diffusion
The membrane is not permeable to all
molecules
Ion channels
Specialized pores
Carrier molecules
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Osmosis- diffusion of water
Water will move through membrane when
solutes cannot
So cell might take on water, or lose water, if
it is in a solution that is not isotonic
Water will move down the concentration
gradient
Processes allow for filtration of body fluids
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Fatchiyah, Ph.D. JB UB
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Diffusion and osmosis do not require energy
Active transport: substances are moved from
area of low concentration to high
Examples: sugars, amino acids, various ions
ATP is required
release of energy
change in shape of transport protein
Endocytosis, exocytosis
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The cell cycle
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Cell cycle is carefully controlled
Cells can divide a limited number of times
(Hayflick limit)
Proto-oncogenes
Tumor suppressors: genes that control the cell
cycle
If these genes are damaged cancer (tumors)
may result
Cell death (apoptosis) is also regulated
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We all started out as one cell!
How do we develop so many different kinds of
cells?
How does cell differentiation occur?
hormones, growth factors, etc.
What are stem cells?
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Summary
All living things are composed of one or more
cells
Eukaryotic cells contain organelles that have
specialized functions
Membranes (and physical laws) regulate the
movement of materials into and out of
cells
Grwoth and differentiation of cells is carefully
regulated
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