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Bio 181 Lecture 1

by: Ariel Hudson

Bio 181 Lecture 1 BIO 181

Ariel Hudson
GPA 3.0
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Cell to Cell interactions, for Chakra's class!
General Biology 1
Chakravadhanula, Farrokh, Konikoff
Class Notes
Biology, cells




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This 2 page Class Notes was uploaded by Ariel Hudson on Wednesday March 30, 2016. The Class Notes belongs to BIO 181 at Arizona State University taught by Chakravadhanula, Farrokh, Konikoff in Winter2015. Since its upload, it has received 138 views. For similar materials see General Biology 1 in Biochemistry at Arizona State University.

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Date Created: 03/30/16
Lecture 1– Cell­cell interactions.  ● Terms to know: cellulose microfibrils, pectins, collagen, proteoglycans, integrins,  laminins, ECM, ligand, receptor, signal transduction, G­protein coupled receptors, second  messengers, enzyme­linked receptors, phosphorylation cascade ­ Cellulose Microfibrils: the fibrous component of plant primary cell walls synthesized by  enzymes in the plasma membrane. They are long strands of of cellulose bundled into microfibrils  and cross­linked by other polysaccharide filaments. ­ Pectins: They are gelatinous polysaccharides that fill the space between microfibrils in  plants, they are synthesized in the rough ER and Golgi and are hydrophilic so they can hold lots  of water. ­ Collagen: fibrous component in animal cells. ­ Proteoglycans: gelatinous polysaccharides in animals that have a protein core with large  polysaccharides attached. ­ Integrins: connect the ECM to the cytoskeleton ­ Laminins: these are ECM crosslinking proteins ­ ECM: extracellular matrix, most animals have these. - Ligand: an ion or molecule attached to a metal atom by coordinate bonding, receptors  change shape and activates its G­protein in response to Ligand bonding. ­ Receptor: a protein that changes shape and activity after binding with a signaling  molecule. They can be blocked in such a way they are unable to receive signal, and they are  dynamic. ­ Signal Transduction: conversion of a signal from one form to another and forms a  network. Lipid insoluble signals must undergo this. It begins at the plasma membrane and has  two major systems: G­protein coupled receptors and enzyme­linked receptors. Signal  transductions are dependent of each other. ­ G­Protein Coupled Receptors: part of signal transduction, the receptors initiate  production of intracellular “second messengers” that then amplify the signal. An activated g­ protein interacts with another protein in the plasma membrane to produce a second messenger.  Afterwards are deactivated by turning on enzymes. ­ Second Messengers: Second messengers are small, non­protein signaling molecules  that elicit an intracellular response to the first messenger. They aren’t restricted to a single role or  cell type. More than one second messenger may be triggered by the same extracellular signaling  molecule. They ultimately alter gene expression or activate/deactivate proteins in the target cell.  When second messengers are cleared from the cytosol, the response stops ­ Enzyme­Linked Receptors: these receptors trigger protein activation in the cell. These  receptors cause a phosphorylation cascade and make an effect in the cell.  - Phosphorylation Cascade: A phosphorylation cascade is a sequence of events where  one enzyme phosphorylates another, causing a chain reaction leading to the phosphorylation (the addition of a phosphoryl group (PO 32−) to a molecule)  of thousands of proteins ● What is the organizational scheme of the plant primary cell wall and the animal ECM?  What dominates the fibrous and gelatinous components of each? ○ Both plants and animals follow the same organizational scheme, they  both have fibers that resist pushing and pulling forces as well as gel­forming  polysaccharides that withstand pressing forces. ○ For plants, the fibrous component is cellulose microfibrils and their  gelatinous polysaccharides are called pectins and these fill the space between the  microfibrils.  ○ For animals, the fibrous component is collagen and their gelatinous  polysaccharides are called proteoglycans. ● Know the structures and functions of tight junctions, gap junctions, desmosomes, and  plasmodesmata ○ Tight Junctions: junctions that seal cells together, found in animal cells,  these were compared to “staples” in class. They are very dynamic and are capable of  forming watertight seals, but they are very weak individually. ○ Gap Junctions: act as channels between animal cells, they allow for  rapid communication. They look like tunnels between the cells. ○ Desmosomes: connect the cytoskeletons of cells. ○ Plasmodesmata: In animals they are the same as gap junctions, but in  plants they form physical connections between the two plant cells. ● What are the four major steps of cell­cell signaling? know a brief description of each. ○ 1.  Signal Reception: there must be something present to detect the  signal, a receptor. ○ 2.  Signal Processing: Something has to happen to cause a change in  the cell. ○ 3. Signal Response: messengers or proteins may be activated and gene  expression can change. ○ 4.  Signal Deactivation: signals are turned off ● How are lipid soluble vs. lipid insoluble signals processed? ○ Lipid soluble signals can go directly through the cell’s plasma membrane  and directly to the receptor to initiate a signal response. ○ A lipid insoluble signal cannot pass through the cell’s plasma membrane  and must be met at the membrane by a receptor protein attached to the membrane and  that signal is then goes through transduction and amplification (in most cases) and after  those extra steps the signal response occurs. ● What are two major types of signal transduction and amplification systems, and how do  they work? ○ G­protein coupled receptors: initiate production of intracellular “second  messengers” that then amplify the signal.  ○ Enzyme­linked receptors trigger protein activation in the cell, always  forms a phosphorylation cascade ● Crosstalk – know that cells can respond to various signals in an integrated manner, and  they can depend on one another.


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