Transcript CELL

THE CELL
Anindyaningrum Chrisant Rystiasih
Nadia Karlina
FT 7 - 2009
The Discovery of Cells
I. Robert Hooke (1665), described chambers in cork; called them cells (cellulae)
II. Anton van Leeuwenhoek (1665-1675),
A. The first to describe living single cells; results were checked and confirmed
by Hooke
B. Saw “animalcules” in pond water using the scopes that he made
III. 1830s - full & widespread importance of cells realized
A. Matthias Schleiden,realized that, despite differences in tissue structures, all
plant tissues were made of cells & that plant embryos arise from single cell
B. Theodor Schwann, realized cellular basis of animal life; concluded that plants &
animals are similar structures
C. Schwann then proposed first two tenets of Cell Theory
1. All organisms are composed of one or more cells.
2. The cell is the structural unit of life for all organisms.
D. Rudolf Virchow, made good case for & added third tenet of Cell Theory derived
from his cell division observations; Cells can arise only by division from a
preexisting cell.
Miller Experiment
Replicate conditions of Earth’s Primitive
atmosphere
•Little/no free oxygen
•Mostly CO2 & N2
•Also H2, H2S & CO
(PLUS) Energy: Sunlight/ Electrical
Discharge
(EQUALS) Organic Molecules
First cell is presumed to be self replicating
RNA in phospholipid membrane.
Basic Properties of Cells
•
I. Life – most basic property of cells; they are the smallest units to
exhibit this property
•
II. Cells are highly complex and organized
Each level of structure in cells has a great level of consistency from
cell to cell :
Organelles have consistent macromolecular composition arranged in a
predictable pattern
Cell structure is similar from organism to organism despite
differences in higher anatomical features
•
III. Cells possess genetic program & the means to use it (a blueprint);
encoded in collection of genes
•
IV. Cells are capable of producing more of themselves - mitosis and
meiosis
•
V. Cells acquire & use energy (constant input) to develop & maintain
complexity – photosynthesis, respiration
Source of all energy needed by life on Earth arrives from sun
Basic Properties of Cells Contd.
•
VI. Cells carry out a variety of chemical reactions - sum total of chemical
reactions in cells (metabolism); to do this, cells require enzymes (molecules
that greatly increase rate of chemical reactions)
VII. Cells engage in numerous mechanical activities (require constant energy
to keep working):
A. Material moved from place to place
B. Structures assembled and disassembled
C. Cells move from place to place
•
•
VIII. Cells able to respond to stimuli whether organisms are uni- or multi
cellular - have receptors that sense environment & initiate responses (move
away from object in path or toward nutrient source)
• IX. Cells are capable of self-regulation
A. Importance of regulatory mechanisms most evident when they break down
1. Failure of cell to correct error in DNA replication -> may lead to
debilitating mutation
2. Breakdown in growth control -> may lead to cancer cell & maybe death of
whole organism
Eukaryotic Animal Cell
Eukaryotic Plant Cell
Eukaryotic Cell Cycle
•
•
•
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M, G1, S, G2
M mitosis (usually followed by cytokinesis)
S DNA replication
G1 Gap 1 metabolically active and
continuously grow
• G2 Gap 2 growth continues, protein are
synthesis for preparation of mitosis
Why are most cells so small?
• A. Most eukaryotic cells have single nucleus with only 2 copies of most
genes
1. Thus, cells can only produce limited number of mRNAs in a given
amount of time
2. The larger a cell's volume, the longer it takes to make the number of
mRNAs the cell needs
• B. Surface area/volume ratio which affects ability to exchange molecules.
Large cell=Small surface area/volume ratio --> surface area is not sufficient
to take up substances needed to support metabolism (oxygen, nutrients,
etc.) or get rid of wastes
• C. Cells depend on diffusion
As cell becomes larger, distance from surface to interior gets larger;
diffusion time required to move things in & out of a metabolically
active cell becomes too long
Larger Cells Have Strategies
• Increase Surface Area
Eg. Intestinal epithelium which absorbs solutes have
microvilli .
• Decrease cell metabolically active area
Eg. interior of large plant cell is typically filled by large,
fluid-filled vacuole rather than metabolically active
cytoplasm
• 4. Giraffe (and other large animal) nerve cells - very long
but very small diameter
Stem Cells
• A cell that divides to produce daughter cells
that can either differentiate or remain as stem
cells
• Source for production of differentiated cells
throughout life eg. Blood cells, epithelial cells
of skin, epithelial cells of digestive tract (all of
which have short life span)
Embryonic Stem Cells
• Can differentiate into any type of cell
Eg. Cell-nuclear replacement or "therapeutic cloning"
This
is
Adult
Stem
Cell

Cell Communication
• Direct cell to cell
ex: embryonic development, maintainance adult
tissue
• Indirect
– Endocrine signaling (hormone, eg: estrogen)
– Paracrine signaling (molecule release on one cell and acts
on neighboring target cell, eg: response of vertebrate
immune system cells to foreign antigens)
Cell Death & Renewal
• Apoptosis, programmed cell death
• Active Process, maintenance of embryonic
development and adult tissues
• Apoptotic cells and fragments removes by
phagocytosis
• Effector: caspases enzyme
• Major caspases in Mamalian cells is
apoptosome complex (+ cytocrom C from
Mytochondria)
QUIZ!!!
• Please Prepare a Sheet of Paper
• We will now test if you have been paying
attention.
• What is the smallest unit of Living Things?
CELL
• The Ovum is the largest ……CELL
while the
CELL
smallest is the sperm ….
• Organisms are called Multicellular Organisms
because they consist of multiple number
of…?
A. tissues
B. organs
C. cells
• What is a single space in an Excel sheet called?
CELL
• Fill in the dots:
CELL
• The longest ……
in the human body is
the motor neuron cell located in the
spinal chord, near the central
nervous system.
• There are more nerve …..CELL
In your
brain than stars in the milky way.
Reference
• http://www.answersingenesis.org/tj/ima
ges/v18/i2/abiogenesis_experiment.jpg
• Cooper, Geoffrey M. Hausman, Robert E.
The Cell. A Molecular Approach. Fourth
Edition. Washington, DC. 2007.
• easyweb.easynet.co.uk/~sfl/rlb_stem.ht
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