2. 2
3.1: Introduction
• The basic organizational
structure of the human body is
the cell.
• There are 50-100 trillion cells
in the human body.
• Differentiation is when cells
specialize.
• As a result of differentiation,
cells vary in size and shape
due to their unique function.
4. • Major parts include:
• Nucleus
• contains DNA
• Cytoplasm
• cellular contents between plasma membrane & nucleus
• Cell membrane
• selective barrier
4
5. Cell Membrane
(aka Plasma Membrane)
• Outer limit of the cell
• Controls what moves in and out of the cell
• Selectively permeable
• Phospholipid bilayer
• Water-soluble “heads” form surfaces (hydrophilic)
• Water-insoluble “tails” form interior (hydrophobic)
• Permeable to lipid-soluble substances
• Cholesterol stabilizes the membrane
5
7. 7
Cytoplasm
• Cytosol = water
• Organelles = solids
Cytoplasm is really like a Jello fruit
salad where the Jello is the cytosol and
the fruits (oranges, grapes, bananas,
maybe walnuts, etc.) are the
organelles.
14. 3.3: Movements Into
and Out of the Cell
There are 2 ways substances move through the cell
membrane.
14
•Passive mechanisms do
not require energy.
• Simple diffusion
• Facilitated diffusion
• Osmosis
• Filtration
Active mechanisms require cell
energy
• Active transport
• Endocytosis
• Exocytosis
• Transcytosis
15. 15
Simple Diffusion
•The process by which molecules or ions scatter or spread
spontaneously from a higher concentration to a lower
concentration
• Oxygen and carbon dioxide can diffuse readily through the cell
membrane
•Equilibrium is reached.
Time
Solute molecule
Water molecule
A B A B
(2) (3)
Permeable
membrane
A B
(1)
17. 17
Facilitated Diffusion
• Substances that are not able to pass through the lipid
bilayer need the help of membrane proteins to get across,
this is called Facilitated Diffusion
•Carrier molecules “revolving doors” are used to carry large
molecules (transported substance) across the membrane.
• Ex. Glucose and amino acids
Region of higher
concentration
Transported
substance
Region of lower
concentration
Protein carrier
molecule
Cell
membrane
18. 18
Animation:
How Facilitated Diffusion
Works
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20. 20
Animation:
How Osmosis Works
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24. 24
Active Transport:
Sodium-Potassium Pump
• Active transport mechanism
• Creates balance by “pumping” three (3) sodium (Na+)
OUT and two (2) potassium (K+) INTO the cell
• 3:2 ratio
34. 34
Animation:
Mitosis and Cytokinesis
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35. 35
Cytoplasmic Division
• Also known as cytokinesis
• Begins during anaphase
• Continues through telophase
• Contractile ring pinches cytoplasm in half
36. 36
Animation:
Control of the Cell Cycle
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37. 37
3.5: Control of Cell Division
• Cell division capacities vary greatly among cell types
• Skin and blood cells divide often and continually
• Neuron cells divide a specific number of times then cease
• Chromosome tips (telomeres) that shorten with each
mitosis provide a mitotic clock
• Cells divide to provide a more favorable surface area
to volume relationship
• Growth factors and hormones stimulate cell division
• Hormones stimulate mitosis of smooth muscle cells in uterus
• Epidermal growth factor stimulates growth of new skin
• Tumors are the consequence of a loss of cell cycle control
• Contact (density dependent) inhibition
39. 39
Animation:
How Tumor Suppressor Genes
Block Cell Division
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40. 40
3.6: Stem and Progenitor Cells
• Stem cell:
• Can divide to form two new stem cells
• Self-renewal
• Can divide to form a stem cell and a progenitor cell
• Totipotent – can give rise to every cell type
• Pluripotent – can give rise to a restricted number of cell
types
• Progenitor cell:
• Committed cell
• Can divide to become any of a restricted number of cells
• Pluripotent