Cell Specialization Unicellular Organism consists of only one

Cell Specialization

Unicellular Organism – consists of only one cell - that one cell carries out all functions required to maintain the life of the organism Multicellular Organism – consists of more than one cell - Cells are specialized to perform certain functions (cell specialization/differentiation)

Examples of Cell Specialization 1. Neuron (nerve cell) - sends info from one part of the body to another - very long and thin

Examples of Cell Specialization 2. Red Blood Cells - carry oxygen throughout body - flattened disks so that they can easily flow through blood vessels

Examples of Cell Specialization 3. Sperm Cell - fertilizes egg - strong tail for quick swimming, distinct head for entering egg cell

Cell differentiation is a result of different gene expression.

• Most cells in your body have the same DNA • Cells use only the DNA that they need; the rest is inactive • For example, skin cells use the DNA that codes for melanin (a skin pigment that protects from UV light) • Heart cells do not need melanin, so it is “turned off” in heart cells

Stem Cell Research • stem cells – cells of humans that can develop into different cell types

• 2 kinds: embryonic and adult • some researchers believe that they can be a source of replacement cells to treat disorders (ex. Parkinson’s disease and burn injuries) Embryonic stem cells Adult stem cells

Cell Communication - Cells communicate with one another by secreting and receiving chemicals - Chemicals released by one cell can influence the activity of another cell http: //learn. genetics. utah. edu/content/begin/cells/cellcom/

Example of Cell Communication - Sensory cells to nerve cells to muscle cells http: //bcs. whfreeman. com/thelifewire/content/chp 46/46020. html

Cell Communication (cont. ) Hormone – communication chemicals that travel through the blood (ex. insulin, estrogen) - Secreted by endocrine glands

- Acts much slower than nerve impulses but effects last much longer - Only influence the action of target cells that have specific receptors

Two Hormone Mechanisms 1. Negative Feedback – the end product stops the production of the hormone

Negative Feedback

2. Positive Feedback – the last step triggers more release of the initial hormone or other hormones - triggers a series of events