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The cell theory states…
The cell is the basic unit of life
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All organisms are made up of
one or more cells
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All cells come from pre-existing cells… HOW?
Cells reproduce via cellular division
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What is reproduction?
Is the birth of new organisms
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Reproduction occurs much more often at the
cellular level
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Ectoderm
- Central nervous system
- Retina and lens
- Cranial and sensory
- Ganglia and nerves
- Pigment cells
- Head connective tissue
- Epidermis
- Hair
- Mammary glands
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Mesoderm
- Skull
- Head, skeletal muscle
- Skeleton
- Dermis of skin
- Connective tissue
- Urogenital system
- Heart
- Blood, lymph cells
- Spleen
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Endoderm
- Stomach
- Colon
- Liver
- Pancreas
- Urinary bladder
- Epithelial parts of
- trachea
- lungs
- pharynx
- thyroid
- intestine
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Cell division plays a role in…
- The replacement of lost or damaged cells
- Cell reproduction and growth
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Before a parent cell divides, it duplicates all of its
genetic material
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Homologous chromosomes are
similar but not identical (one from each parent)
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Sister chromatids
- chromosome that replicated
- Identical
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After cell division the two resulting “daughter” cells are
genetically identical
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What is a genome?
The complete set of an organism’s gene
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Genes are
sequences of nucleotides, sequences of DNA that code for a protein or a functional RNA
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Genes are located
mainly on chromosomes in the cell’s nucleus
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Centromere
center of chromosome
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Telomere
ends of chromosome (top or bottom)
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Chromosomes…
- Are made of chromatin, a combination of DNA and protein molecules
- Are not visible in a cell until cell division
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he cell cycle consists of two distinct phases:
- Interphase (90%)
- Mitotic phase (10%)
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Mitosis is
the division of the chromosomes
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Mitosis is preceded by
Interphase
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Three steps of interphase
G1, S, G2
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Mitosis consists of four distinct phases:
- Prophase
- Metaphase
- Anaphase
- Telophase
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Order of Cell Division
G0 --> G1 --> S --> G2 --> Mitosis (PMAT) --> Cytokinesis
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Prophase
- Asters (microtubule arrays) are seen
- chromatin condenses into chromosomes attached to one another by their centromere (sister chromatids + proteins = kinetochore)
- Nucleoli disappear
- Centriole pairs separate and the mitotic spindle (mitotic spindles) is formed
- Nuclear envelope disappear
- Microtubules attach to kinetochores and begin moving sister chromatids to the center of the cell.
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Metaphase
- Sister chromatids cluster at the middle of the cell with their centromeres aligned at the exact center
- This arrangement of chromosomes along a plane midway between the poles is called the metaphase plate
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Anaphase
- Centromeres of the sister chromatids split and each becomes a chromosome again
- Motor proteins in kinetochores pull chromosomes toward poles
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Telophase
- Telophase is a reversal of prophase
- It "cleans up" the aftereffects of mitosis.
- Corresponding sister chromosomes attach at opposite ends of the cell.
- A new nuclear envelope, using fragments of the parent cell's nuclear membrane, forms around each set of separated sister chromosomes.
- Both sets of chromosomes, now surrounded by new nuclei, unfold back into chromatin.
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Cytokinesis
- Cytokinesis typically occurs during telophase
- Is the division of the cytoplasm
- Note: NOT A PART OF MITOSIS
- Mitosis and cytokinesis are two different phases in the cell cycle
- So mitosis ends at telophase
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Cancer is a class of diseases in which a group of cells display the following
- characteristics:
- Uncontrolled growth (division beyond the normal limits)
- Invasion (intrusion on and destruction of adjacent tissues)
- Sometimes metastasis (spread to other locations in the body via lymph or blood)
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Cancer is caused by a breakdown in control of the cell cycle in which
The cancerous cell ignores the cell checkpoints
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Cancer Treatment
- Radiation therapy disrupts cell division
- Chemotherapy involves drugs that disrupt cell division
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Cancer prevention includes changes to lifestyle
- Not smoking
- Avoiding exposure to the sun
- Eating a high-fiber, low-fat diet
- Visiting the doctor regularly
- Performing self-examinations
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Cellular Diversity
- Specialized functions of cells relates to the shape of cells and the arrangement of
- organelles
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Fibroblast
makes and secretes protein compound of fibers
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Erythrocyte (RBC)
concave shape provides surface area for uptake of the respiratory gases
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Epithelial cell
hexagonal shape allows maximum number of epithelial cells to pack together
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Skeletal and smooth muscle cells
- elongated and filled with actin and myosin
- contract forcefully
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Fat cell (adipocyte)
shape is produced by large fat droplet in its cytoplasm
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Macrophage
phagocyte that moves through tissue to reach infection sites
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Neuron
long processes for receiving and transmitting messages
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Oocyte (female)
- largest cell in the body
- Contains many copies of organelles for distribution to daughter cells
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Sperm (male)
possesses long tail for swimming to the egg for fertilization
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Free radical theory
- 1) Damage from byproducts of cellular metabolism
- 2) Radicals build up and damage essential molecules of cells
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Mitochondrial theory
a decrease in production of energy by mitochondria weakens and ages our cells
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Genetic theory
proposes that aging is programmed by genes
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Telomeres
“end caps” on chromosomes that limit the maximum number of time a cell can divide
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Telomerase
prevents telomeres from degrading
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