Unified Cell Theory
1. Cell is the basic unit of life
2. All living things are composed of one or more cells
3. All cells come from pre-existing cells
Robert Hooke- saw a thin slice of cork under a microscope and describes the structures as cells in
jail
Anton van Leeuwenhoek- discovered protist which he called “animacules” and is the father of
microbiology
Rudolf Virchow- contributed to the development of cell theory and stated “Omnis cellula e cellula”
Matthias Schleiden- saw cells in plants
Theodore Schwann- observed cells in animals
Diversity of Cells
In the World
bulkiest cell – ostrich egg
longest cell – neuron/nerve cell
smallest cell – mycoplasma
In Humans
bulkiest cell – egg cell
longest cell – sciatic nerve
smallest cell – sperm cell
Common Cellular Components
Regardless of cell type, all cells have:
1. plasma membrane
2. cytoplasm
3. genetic material
4. ribosome
Prokaryotic Cell vs Eukaryotic Cell
Prokaryotic cells
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Basic cell type, no true nucleus, circular genetic material
bacteria and archaea
always single-celled
an estimate of 4 to 6×10^30 prokaryotic cells on earth
small 1-5𝛍m
Eukaryotic Cells
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with nucleus (linear genetic material) and membrane bound organelles
animals, plants, fungi, and protists
can be unicellular or multicellular
an estimate of 10^7 eukaryotic cells in the world
large, 10-100𝛍m
Endosymbiotic Theory - A theory that explains the complexity of eukaryotes. Proposed that
mitochondria and chloroplasts were one free-living prokaryotes that live within a host cell, until they
evolved together.
Prokaryotic Cell Structure (bacteria and archaea). . only some of it
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Cell wall – made of peptidoglycan; protects the cell from bursting or shrinking in hostile
environments
Flagellum- long, whip-like structure; function is for movement
Fimbriae (singular: Fimbria) – used by the bacteria to attach to the host cell
Bacterial Shape
Eukaryotic Cell Structure (plants, animals, protists)
Endomembrane System - regulates protein traffic and performs metabolic functions in the cell. The
movement of nutrients is from:
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synthesis of the protein on the ribosome;
modification in the endoplasmic reticulum;
tagging in the Golgi;
distribution by the vesicle to other cell parts
Components of the endomembrane system:
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Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Plasma membrane
These components are either continuous or connected via transfer by vesicles.
For other cell components, study the table provided to you during class, focus on:
Endoplasmic Reticulum
Peroxisome
Nucleus
Centrosome
Mitochondria
Plasma Membrane
Ribosome
Intermediate Filaments
Lysosome
Extracellular components, focus on:
Extracellular matric
Gap junction
Plasmodesmata
Cell Cycle – sequence of events occurring within a cell as it undergoes growth and division
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Interphase – DNA/chromosome duplication (during S phase); organelle duplication; increase in
cell size
G2 checkpoint – checks for correct and complete duplication of genetic materials
M checkpoint – checks if spindle is attached before proceeding to anaphase
MPF level declines at the end of mitosis because cyclin is degraded
Cdk – positive regulator; phosphorylates other proteins when activated
P53 – negative regulator; can trigger apoptosis
Rb – negative regulator; “tumor suppressor”; prevents DNA transcription
Mitosis – produces two diploid cells; somatic cell cycle
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Prophase – condensing of chromosomes and disintegration of nuclear envelope
Prometaphase – formation of kinetochore in the centromeric region of the chromosome
Metaphase – Alignment of chromosomes in the metaphase plate
Anaphase – Separation of the sister chromatids
Telophase – Unpacking of chromosomes and the formation of new nuclear envelope
Meiosis – produces four haploid cells; gametes cell division
➢ Chiasmata – point of crossing over between non sister chromatids
➢ Crossover – Recombination nodules mark the crossover point; Chiasmata are formed; Non-sister
chromatids exchange genetic material.
Binary Fission – prokaryotic cell division; there is no karyokinesis (prokaryotes don’t even have nucleus!);
FtsZ proteins directs the formation of septum
Errors in Cell Cycle
Nondisjunction. It happens when the sister chromatids do not separate equally. The end result is one
gamete that is missing a chromosome and one that gets an extra. If this happens to an autosome
chromosome, a gamete missing any one of the chromosomes doesn’t survive. In a few situations,
though, the gamete getting the extra chromosome does survive.
What do Down syndrome, Edward syndrome, and Patau syndrome have in common? Each of these is a
relatively common trisomy disease compared to other trisomy possible states. In these diseases,
chromosome 21, chromosome 18, and chromosome 13 (respectively) are in threes in each cell instead of
two (because of nondisjunction). Of these three disorders, only one is survivable: Down Syndrome.
Babies born with the other two diseases rarely survive for long.
Klinefelter’s syndrome (XXY, instead of the normal XY) is an example of sex chromosomal disease
affecting males where they get an extra X chromosome, leading to additional female phenotypic
feature/s.
Plasma Membrane, focus on:
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Phospholipid
Cholesterol
Protein
Carbohydrates
Fluid Mosaic Model and its proponents
Active vs passive transport
Pinocytosis vs phagocytosis
Hypotonic vs Hypertonic solution