Bio 181 Lecture 1
Bio 181 Lecture 1 BIO 181
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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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