Do Now –please • Take out a piece of binder paper• Divide into 4 quadrants1.1. top left corner –a TV show or top left corner –a TV show or

movie you think more people movie you think more people should watchshould watch

2.2. top right corner – Name of the top right corner – Name of the street you’ve lived on the street you’ve lived on the longestlongest

3.3. bottom left corner – a silly wordbottom left corner – a silly word4.4. bottom right corner – favorite bottom right corner – favorite

animal animal Last Week Tonight

Amethyst WayAmethyst Way

bababooey tiger

Don’t take too long – these answers aren’t important

Cell Communication

Overview• Cell-to-cell communication is absolutely

essential for multicellular organisms Trillions of cells in a human body - there

must be a way to coordinate activities

Overview

• 3 steps1.Receive a signal2.Pass the message along inside the cell3.Have a response to that signal

Overview• Communication

is also important in unicellular organisms

Overview• Biologists have discovered

universal mechanisms of cell communication

• The same small set of cell signaling processes show up across all life forms More evidence for the More evidence for the

interrelatedness of all living interrelatedness of all living thingsthings

Overview• Cells most often

communicate by using chemical signals

Some questions to explore

1. What messages are passed from cell to cell?

2. How do cells respond to these messages?

An example of Cell Communication in microbes

• Microbes like yeast talk about sex

• Saccharomyces cerevisiae (yeast) identify potential mates using chemical signals

Yeast Sex

• There are 2 “sexes” or mating types a - secretes “a” factor - secretes “” factor

These factors bind to receptor proteins on the other mating type

Yeast Sex

• Once the mating factors have bound to the receptors the 2 cells grow toward each other

• The 2 cells fuse, or mate, to form an a/ cell Contains genes of

both cells Advantage for future

“offspring” since have more genetic resources

CRITICAL VOCAB!!

• Transduction - the conversion of a signal from outside the cell into a form that can bring about a specific cell response

Message from outside the cell

Transduction to another “form”

Cell response

Back to yeast sex…

• Q: So how does the attachment of the signal molecule on the surface of the yeast cell get transduced into a form that causes the cells to fuse?

• A: by a signal transduction pathway

CRITICAL VOCAB!!

• Signal transduction pathway - a process by which a signal on the cell’s surface is converted into a specific cell response

Quick Think

•Discuss with a neighbor how yeast cells communicate in order to mate

With your silly word buddy

Signal Transduction Pathways

• They are very similar in yeast and animal cells Evidence for a common ancestor

• Plants and bacteria have similar pathways

• Evidence suggests a prokaryotic ancestor that was capable of signaling - this organism was “adopted” for use in single cell eukaryotes and multicellular organisms (similar to the “adoption” of chloroplasts and mitochondria)

Cell Communication in multicellular organisms

• Communication in multicellular organisms usually involves releasing signaling molecules that target other cells, as we saw in the yeast

Direct Contact between cells

• Recall that cells may have junctions that connect adjacent cells

Direct Contact between cells

• With intercellular junctions, substances dissolved in the cytosol of one cell can freely pass into the adjacent cell

• Animal cells may communicate via direct contact between membrane surface molecules

• Most often used in development of the embryo and during the immune response

Local contact

• Signaling cell may Signaling cell may secrete messenger secrete messenger moleculesmolecules

• These chemical messages may travel only a short distance and influence cells only in the local vicinity

CRITICAL VOCAB!!

• Local regulators - a chemical messenger that influences cells in the vicinity

Example

• Growth factors in animals - stimulate nearby target cells to grow and divide

• paracrine signaling - Many nearby target cells receive and respond to a local regulator that is secreted by just one messenger cell

More specialized local signaling

• Synaptic signaling - occurs in nerve cells

• Nerve cell releases a neurotransmitter

• It diffuses across the synapse (small gap between 2 neurons)

• Neurotransmitter stimulates the target cell

• Can also be considered long distance signaling because message is passed from neuron to neuron over a long distance

CRITCAL VOCAB!!

• Paracrine signaling - when numerous cells simultaneously receive and respond to growth factors produced by a single cell in their vicinity

• Synaptic signaling - when a nerve cell releases neurotransmitters into a synapse, stimulating the target cell

Local signaling in plants

• This is not well understood yet

• Must be different somehow from animals due to presence of cell walls in plants

Quick Think

•With a neighbor, describe paracrine signaling and give an example of it

With your TV show buddy

Long distance signaling

• Both plants & animals use hormones for long distance signaling

• In animals - endocrine cells release hormones into circulatory system - hormones travel to other parts of the body

• In plants - hormones called growth regulators - may travel in vessels, may travel cell to cell, may travel through the air by diffusion

Long distance signaling

• Chemical messengers vary

• Plant hormone ethylene - very small (C2H4) - makes fruit ripen - can pass through cell walls

• Animal hormone insulin - 1000s of atoms big - regulates blood sugar - travels in blood stream

Quick Think

• Discuss with a neighbor how plant and animal cells carry out long distance signaling.

• Explain why nerve cells provide an example of both local and long distance signaling With your

street buddy

What happens when a cell encounters a signal?

• The signal must be recognized by the target cell Target cells have specific receptor molecules

on their cell membranes

• The information in the chemical signal must be changed into another form - Transduced - inside the cell before the cell can respond

There are 3 stages of cell signaling

1. Reception - target cell receives chemical signal2. Transduction - conversion of the signal to a

form that brings about a specific cell response3. Response - the transduced signal finally brings

about a cell response

Quick Think

• Discuss with a neighbor:

• Summarize how cells communicate in 1 sentence.

With your animal buddy