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

Close-up: Blood cells in capillary

Examples of Cell Specialization3. Sperm cell:

– Fertilizes egg– Strong tail for quick swimming, distinct head

for entering egg cell

* Cell differentiation is a result of different gene expression.

Cell Communication• Cells communicate with one another by

secreting and receiving chemicals

Cell Communication• Chemicals released by one cell can

influence the activity of another cell.– Ex: sensory cells to nerve cells to muscle

cells

Cell CommunicationHormones = communication

chemicals that travel

through the blood– 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 mechanisms:

• Negative feedback– The end product stops the production of a hormone

initially secreted

• Positive feedback– The last step triggers more release of the hormone

initially secreted

Birth process triggered by low levels of progesterone

↓

Stimulates release of oxytocin

↓

Uterus contracts, stimulates more oxytocin release

↓

More contraction

↓

Baby is born!