Stem Cells

Textbook: Chapter 5

Cell Theory (term coined by Robert Hooker - 1665, Anton van Leeuwenhoek - microscopes)

1. All organisms are made of 1 or more cells

2. All life functions occur within cells

3. All cells come from existing cells

Stem Cells

Unspecialized - ones that aren’t assigned to a particular function (can stay stem cells or become different: any other cell)

Stages of Development

Totipotent - zygotes

Pluripotent - embryonic

Multipotent/Unipotent - adult stem cells

Light Microscopes to Electron Microscopes

LM - reached their limit by 1800s, couldn’t see structures inside cells

EM - uses electrons instead of light to see structures, molecules, and atoms (invented in 1950s)

Shared Structures by All Cells

1. Plasma membrane

2. Cytoplasm

3. Ribosomes

4. DNA

All suggest a common evolutionary origin for all life on Earth

Cell Size

• Larger cubes/cells have a smaller surface area (SA) to volume (V) ratio than smaller cells

  • Have more volume needing resources but less relative surface area to exchange materials (limits growth)

Nerve Cells

Receives and sends messages from the body to the brain and back to the body (long extensions for messages)

Sperm Cells

Male reproductive cells (tails for movement)

White Blood Cells

Protection against illness and disease (engulf and destroy pathogens)

Prokaryotic Cells

Bacteria and archaea (no nucleus - DNA floats)

• Flagellum

• Pili

• Capsule

• Cell wall

• Plasma membrane

Eukaryotic Cells

Animals, plants, fungi, protists, algae (with nucleus - membrane-bound)

• Nucleus and other organelles (have specialized functions)

• Larger and more complex

Plasma Membrane

Forms a barrier between the inside (cytoplasm) and outside environment of a cell (protects, supports, and controls entry/exit of substances)

• Phospholipid bilayer structure - hydrophilic (water-loving) and hydrophobic (water-hating)

• Other components: cholesterol, proteins, carb-containing molecules, cytoskeleton filaments)

Cytoskeleton

A protein framework within cytoplasm that provides internal structure to the cell (3 types - microtubes, intermediate filaments, and microfilaments)

Nucleus

• Control center of the cell

• Stores DNA

• Enclosed by nuclear envelope with nuclear pores for transport

• Contains nucleoplasm and nucleolus (ribosomes)

Mitochondria

• Site of ATP energy production through aerobic respiration

• Contains own DNA and ribosomes (supports endosymbiotic theory)

• Has double membrane with compartments: outer + inner membrane, cristae, and matrix)

Endoplasmic Reticulum (ER)

Rough ER (RER): makes and transports proteins (studded with ribosomes)

Smooth ER (SER): synthesizes lipids, detoxifies chemicals, stores calcium (no ribosomes)

Golgi Apparatus

• Modifies, sorts, and packages proteins/lipids from ER

• Produces lysosomes and secretory vesicles

• Structure: cis, medial, and trans regions

Vesicles

Small sacs for transport/storage/reactions (types: lysosomes and peroxisomes)

Vacuoles

Larger sacs, more common in plant cells for storage

Centrioles

Organize chromosomes during cell division (only in animal cells, tublin microtubules)

Ribosomes

• Sites of protein synthesis

• Not membrane bound: RNA and protein

• Found free-floating in cytoplasm or attached to RER

Passive Transport (no energy)

Simple diffusion: movement of small, nonpolar molecules (Ex: O2 and CO2)

Osmosis

Diffusion of water from across a semi-permeable membrane (high to low)

• Hypertonic solution: more solute outside, water leaves cells, cell shrinks

• Isotonic solution: equal solute levels, water moves in and out equally, cell remains stable

• Hypotonic solution: larger or charged molecules

Active Transport (energy)

More substances against the concentration gradient (low to high)

• Pump: primary (ATP to move ions) and secondary (energy stored in ion gradients)

• Vesicle:

  • Endocytosis (into the cell) - phagocytosis, pinocytosis, and receptor-mediated

  • Exocytosis (out of the cell) - vesicle fuses with cell membrane (important for waste removal)

ATP

Powers cellular activities (Ex: cellular respiration), is recyclable (made of adenine, ribose, and 3 phosphate groups)

Autotrophs

“Self-feeder” (Ex: plants)

Heterotrophs

“Other-feeder” (Ex: humans)

Cellular Respiration (stages)

• Glycolysis (cytoplasm) - splits glucose (6C) into 2 pyruvate (3C), net gain = 2 ATP, 2 NADH

• Transformation of Pyruvate (mitochondria) - produces CO2 and more NADH

• Oxidative Phosphorylation - electron transport chain (ETC) and chemiosmosis (ATP)

Fermentation

• Lactic acid (in humans/bacteria, produces lactate and NAD)

• Alcoholic (yeast/some microbes, produces ethanol, CO2, and NAD)