Specialized Cells & Cell Origins Page Essential Questions: Do all cells have the same structure? How did complex cells come to be?

Levels of Organization

Cell Differentiation Process by which an unspecialized cell becomes specialized. Stem cells are undifferentiated and depending on where they are on an embryo, they will develop into a specific cell type.

Specialized Cells: Blood Cells Red Blood Cells Function: Carry Oxygen Structure: large surface area to hold oxygen molecules; contains protein called hemoglobin, which binds to oxygen; have no nucleus White Blood Cells Function: Fight infection & protect body from pathogens Structure varies depending on type of leukocyte Platelets Function: Help blood clot Structure: When activated, cells produce long finger-like projections (made of protein!) that are sticky; have no nucleus

Specialized Cells: Neurons Function – carry electrical nerve impulses to different parts of the body Structure Can be very long Myelin sheath covers the axon to help speed the neural impulses Cell body contains the nucleus and other cell organelles

Specialized Cells: Muscle Cells 3 Types of Muscle: Skeletal, Smooth, & Cardiac Function – movement Skeletal: moves bones Smooth: moves food via peristalsis Cardiac: moves blood Structure: long, tubular cells

Specialized Cells: Epithelial Cells Epithelial cells line all surfaces of your body Function Secretion, Absorption, Protection, Cellular transport, Detection of sensations Structure Some have cilia to help move substances Reproduce rapidly

Specialized Cells: Bone Cells

Specialized Cells: Root Cells Roots help support plants & absorb nutrients Each root is lined with root hairs Root hairs increase the surface area of the root How do root hairs affect the plant’s ability to absorb nutrients?

Specialized Cells: leaf Cells Cuticle helps prevent water loss Stomata open and close to let gases in and out of plant Guard Cells surround stomata to control their opening and closing Mesophyll layers contain chloroplasts and absorb sunlight Xylem & Phloem are tubes that transport water and food throughout the plant

Where did complex cells come from?

Endosymbiotic Theory Prokaryotic cells are believed to be the first cells to exist because they are more simple than eukaryotic cells. Theory that more complex cells arose by one simple cell engulfing another. Evidence: Chloroplasts & mitochondria replicate similar to bacteria Chloroplasts & mitochondria have their own DNA & ribosomes, which are similar to bacteria DNA & ribosomes Chloroplasts & mitochondria have their own membranes Believed to be the explanation for how a eukaryotic cell has specialized organelles