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Biology ch 5 notes

by: Megan Smith

Biology ch 5 notes Biol 1103k

Megan Smith
GPA 3.6

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About this Document

this covers chapter 5 notes from the book
Introductory biology I
David blaustein
Class Notes
25 ?




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This 6 page Class Notes was uploaded by Megan Smith on Monday February 1, 2016. The Class Notes belongs to Biol 1103k at Georgia State University taught by David blaustein in Summer 2015. Since its upload, it has received 59 views. For similar materials see Introductory biology I in Biology at Georgia State University.


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Date Created: 02/01/16
Date CELL MEMBRANE STRUCTURE AND FUNCTION 1. HOW IS THE STRUCTURE OF THE CELL MEMBRANE RELATED TO ITS FUNCTION ? Phospholipids • responsible for isolating the cell s contents Proteins • responsible for selectively exchanging substances and communic ating with the environment • controlling biochemical reactions associated with the cel l membrane • forming connections between cells Cell membrane functions: a. selectively isolate the contents of membrane enclosed organelles from the surrounding cytosol, and the cells conents fr om the surrounding interstitial fluid b. regulate the exchange of essential substances between the cell and the interstitial flui d, or between membrane enclosed organelles in the surrounding cytosol c. Allow communication among the cell of multi cellular organisms d. Create attachments within and between cells e. regulate many biochemical reactions B. membranes are “fluid mosaics” in which proteins move within layers of lipids i. Fluid mosaic model o Developed by Nicolson o now known to be accurate ii. fluid o any substance use molecules can flow past one another C. the fluid phospholipid bilayer helps to isolate the cells contents i. phospholipid o consists of two different parts : a. A “head” that is polar and hydrophili c b. A pair of fatty acid “tails” that are nonpolar and hydrophobic ii. interstitial fluid o a weekly salty liquid resembling blood without its cells or large proteins iii. Phospholipid by later o Phospholipids spontaneously arrange themselves into a double layer iv. cholesterol o all animal cell membranes contain cholesterol o especially abundant in the plasma membrane D. a variety of proteins form a mosaic within the me mbrane i. glycoproteins • some membrane proteins their carbohydrate groups that project from the outer membrane surface ii. membrane proteins maybe grouped into five major categories based on their function: a. enzymes b. receptor proteins c. recognition proteins d. connection proteins e. transport proteins iii. enzymes o proteins that promote chemical reactions that synthesize or break apart biological molecules iv. receptor proteins o dozens span cells plasma membrane o Allow cells to respond to specific messenge r molecules v. Recognition proteins o glycoproteins that serve as identification tags vi. connection proteins o anchors cell membranes in various ways vii. transport proteins o stanza phospholipid bilayer and regulate the movement of hydrophilic molecules across the membrane o some transport proteins from pores that can be opened or closed to allow specific substances to pa ss across the membrane 2. HOW DO SUBSTANCES MO VE ACROSS MEMBRANES ? 2 Membrane transport : a. solute § a substance that can be dissolve d in a solvent b. solvent § a fluid capable of dissolving the solute c. concentration § defines the amount of solute in a given amount of solvent d. gradient § a difference in certain properties , such as temperature , or the concentration of a solute in the fluid - between t wo adjacent regions e. concentration gradient § differences in solute concentration across their membranes B. Molecules and fluids defuse in response to gradients i. Diffusion o Random movements of solutes produce a net movement from regions of high concentration to regi ons of low concentration C. movement through membranes occurs buy passive transport and energy requiring transport i. selectively permeable o describes plasma membrane s o Their proteins selectively allow only certain ions or molecules to pass through, or permeate ii. Passive transport o involves diffusion of substances across cell membranes down their concentration gradient iii. Energy requiring transport o requires that the cell expend Energy to move substances across membranes D. passive transport include s simple diffusion, facilitated diffusion, and osmosis i. diffusion can occur within a fluid or cross a membra ne that is permeable to the diffusing substance ii. simple diffusion o some molecules diffuse directly through the phospholipid bilayer of cell membranes iii. facilitated diffusion o ions in polar molecules must you specific trans port proteins to move through so membranes 3 iv. Carrier proteins o span the cell membrane o have regions that loosely binds certain ions or specific molecules such as sugars or small proteins v. Channel proteins o form pores through the cell membrane vi. isotonic o Solutions with equal concentrations of solute ( and thus equal concentrations of water) are isotonic to one another vii. hypertonic o a solution that contains a greate r concentration of solute viii. hypotonic o a more dilute solution ix. turgor pressure o when water flows into the cytosol and then into the vacuole by osmosis o inflates the cell, forcing the cytosol within its surrounding plasma membrane against the cell wall E. Energy requiring transport includes acti ve transport, endocytosis, and exocytosis i. Active transport o membrane proteins use cellular energy to move molecules o r ions across the plasma membrane against their concentration grad ient o this means that the substances are transported from areas of lower concentration to areas of higher concentration o these proteins spend the width of the membrane and have two binding regions a. one loosely binds with the specific molecules or ion b. the second region, on the inside of the membrane, binds ATP ii. ATP o donates energy to the protein , causing the protein to change shape and move the calcium ion across the membrane o the energy for active transport comes from breaking the high -energy bond that links the last of the three phosphate groups in ATP iii. Endocytosis o a cell may need to acquire materials from its extra cellular environment that are too large to move directly through the membrane o this energy requiring process is endocytosis iv. pinocytosis 4 o very small patch of plasma membrane dimples inward as it surrounds interstitial fluid, and then the membrane bud s off into the cytosol as a tiny vesicle v. receptor mediated endocytosis o to specifically take up specific molecules or complexes of molecules that cannot move through channels or diffuse through the plasma membrane vi. Phagocytosis o Moves large particles- sometimes including whole microorganisms- into the cell vii. exocytosis o the process in which cells use energy to dispose of undigested particles of waste or to secrete substances such as hormones into the interstitial fluid F. Exchange of materials across membranes inf luences cells size and shape 3. HOW DO SPECIALIZED J UNCTIONS ALLOW CELLS TO CONNECT AND COMMUNICATE ? Four major types of cell connecting structures: a. Desmosomes b. Tight junctions c. gap injunctions d. plasmodesmata B. Desmosomes attached cells together i. Desmosomes o Join cells in tissues that are repeatedly stretched C. tight junctions makes sell attachments leak proof i. tight junctions o Formed by proteins that span the plasma membrane s at corresponding sites on adjacent cells D. Gap injunctions and Plasmodesmata allow direct communication between cells i. gap junctions o the cells of many tissues in the animal body are interconnected buy gap junctions o clusters of channels ranging and number from a few to thousands ii. Plasmodesmata o Channels that link nearly all adjacent plant cells o these openings are linked with plasma membrane and filled with cytosol 5 o so the membranes in the cytosol of adjacent cells are continuous with one another at plasmodesmata 6


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