Chapter 11: Cell Communication Flashcards by Blen Daniel

Cell-to-Cell Communication is essential for what organisms?

Multicellular Organisms

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Cell Response

The combined effects of multiple signals

Each cell is programmed to respond to specific combos of extra cellular signal molecules

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How do cells in multicellular organisms communicate?

Through chemical messengers

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Cell junctions

Direct connection of the cytoplasm to the adjacent cells to exchange materials

No plasma membrane restrictions

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What are the ways animal cells do local signaling?

Direct contact (cell junction) and cell-cell recognition

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Paracrine Signaling

Type of local signaling

Local regulator diffuses through extracellular fluid.

The secreting cell secretes vesicles to target cell

Allows cells to communicate w/each other by releasing signaling molecules that binds to and activate surrounding cells

Messenger molecules released by cell travels short distances and carry a message to neighboring cells.

Growth factor is released in this manner

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Synaptic Signaling

Type of local signaling, electrical signals along a nerve triggers the secretion of a chemical signal carried by neurotransmitter molecules to stimulate the target cell

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Hormonal Signaling

Long distance signaling, hormones ,secretes by specialized endocrine cells ,travels in bloodstream to target cells

Nerve cells may use long distance signaling

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Signal Transduction

The process by which a signal received on the cell surface is converted into a specific cellular response

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Signal Transduction Pathways

A series of steps by which a signal on a cell’s surface is converted into a specific cellular response

Converts signals on the cell’s surface into cellular responses

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How do Yeast mate?

There are 2 “sexes” of yeast (a &a)

(a )secretes a signaling molecules that binds to receptors on (a). The reverse is true of (a) cell

Signals cause cells to grow together.. produces one cell with combined genetics

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What type of pheromones are people attracted to?

People whose pheromones are very different from our own. So baby can have the best immune system possible

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Quorum Sensing

Control growth rate

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Coordinate Activities

If nutrients are low, soil dwellers aggregate and produce biofilms

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Cell to Cell Recognition

2 cells communicate by recognizing signal molecules of cell surfaces

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What are the 3 stages of Signaling

Stage 1: Reception
Stage 2: Transduction
Stage 3: Response

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Reception

The signal molecules binds to a receptor protein which causes it to change shape

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Ligand

The signal molecule that binds to another molecule

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What does the ligand do to receptor proteins?

change it shape( conformational change) —Activation

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What happens during transduction?

Relay molecules in a signal transduction pathway

How many types of receptors are there?

What are the types of receptors?

Intracellular Receptors & Plasma Membrane Receptors

Intracellular Receptors

Found in the cytoplasm or nucleus of target cell ( inside the cell)

Signal pass through cell membrane to activate receptor

Signal must be small and non-polar

Ex: Steroid hormones ( cholesterol based) Thyroid hormones ( Tyrosine based)

Plasma Membrane Receptors

Found in the plasma membrane ( exterior of cell)

Signal doesn’t have to pass through the membrane; receptors proteins changes shape or join together to transmit info

Signals can be water-soluble

Ex: G-protein-linked receptors, receptor tyrosine kinase and ion channel receptors

What is the process of Intracellular receptors

The signal attaches to the receptor proteins The protein then goes into the nucleus and makes a copy of the DNA needed. mRNA The mRNA then gets out of the nucleus to make new protein

What are the signals used for Intracellular receptors?

Hormones

What are the receptors of the membrane

G-Protein Coupled Receptors Enzyme Receptor (Tyrosine Kinases) Ion Channel Receptors

What is a G Protien-coupled receptor?

Plasma membrane receptor that works with the help of a G- Protein

What does the G protein act as?

As an on/off switch, if the GDP is bound to the G-Protein, the G protein is inactive, if the GTP is bound to the G protein, it becomes active.

What are the G protein receptors used for l?

About 800 genes use these, over 400 are olfactory genes( nose)

What happens at the Receptor tyrosine kinase?

An enzymes( signal molecules) gets in the binding site. After the binding sites shift towards each other ( Dimer). 6 ATPs then proceeds to activate the receptors( 3 phosphate are given to each Tyrosine) This then activates the relay proteins

What does RTK’s Trigger ?

This response triggers cell growth and cell differentiation They always occur in pairs so that cross phosphorylation can occur in the dimer. This binding activates enzyme activities

Ligand- Gated Ion Channel Receptor

Acts as a gate when the receptor changes shape the gate allows specific ions, such as Na+_ , through a channel in the receptor Used a lot in the nervous system Sometimes controlled by electrical signals rather than ligands

Transduction

A multiple step process which occurs when receptor receives signal More steps -> greater responses Many genetic disorders are seen where “steps” are missed

Retts Syndrome

MECP2 - gene that codes for MECP2 protein needed for brain development. The protein acts as a biochemical switch If the MECP2 genes is mutated, the MECP2 protein will be mutated and genes will not be controlled properly

Phosphorylation

A process of the protein kinase transferring phosphates from ATP to protein There may be several proteins kinases in b/tw to activate the protein

Protein kinase

An enzyme that transfers phosphate from ATP to protein

Cellular Response

Cell signaling leads to regulation of transcription or cytoplasmic activities

How may the cell response regulate protein synthesis?

By turning a gene on or off … can lead to the “extra” protein features w/ added exposure of hormone

How May the cell response regulate the activity of a protein?

Opening or closing protein channels used for transport Affecting activity of enzyme with inhibitors

Progesterone

Triggers the female cells to prepare the inner lining of the uterus for Possible embryo & inhibit the contraction of the uterus Not fertilized, progesterone levels drop and the endometrium level begin to breakdown… the cell within are programmed for apoptosis

Apoptosis

Cell signaling for cell suicide

What cells are given the orders for apoptosis

Damaged, old or infected to prevent enzyme leakages to other “healthy” cells

Cytochrome C

A protein in ETC can also function as a cell death factor Mitochondria is induced to “leak” cytochrome c into the cytoplasm. The cell recognizes the leak and release Cassandra which order cell suicide

Who often send the cell death signals ?

It’s often the nucleus that send the signal, cell recognizing errors in the DNA beyond repair.

What does P53 do ?

It orders the cell to commit suicide if DNA is damaged beyond repair. This is detected at G1 checkpoint

How is P53 used medically?

Cancer treatment, considered to be the tumor depressor gene

How is Apoptosis used developmentally ?

Used to eliminate “ extra” cell growth during embryo stage