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Enzymes, Chemical Reactions and Cell Transport Mechanisms Test Study Guide Enzymes – Shape determines function o Specifically shaped for one substrate (Lock-key) o Denatured with pH, Temp and Salinity – when an enzyme is denatured – the shape changes. o If shape changes, function is reduced – cannot bind substrate anymore if shape is changed Catalyst o Speeds up reaction rate o Reduces activation energy o Remains unchanged from reaction Chemical Reactions – Endothermic: absorbs energy o Makes bonds o Dehydration synthesis Exothermic: releases energy o Breaks bonds o hydrolysis Controlled via the Cell Membrane Passive Transport Active Transport Does NOT require energy, moves from HIGH concentrations to LOW concentrations DOES require energy, moves from LOW concentrations to HIGH concentrations Diffusion Moves small molecules, like CO2 & O2 gases, directly through the membrane Osmosis Movement of water across the membrane 3 Types of Solutions Hypertonic Water moves out of the cell & it shrinks Isotonic Water moves equally in and out of the cell; it stays the same size Facilitated Diffusion Uses transport proteins to move large molecules through the membrane WITHOUT energy Hypotonic Water moves into the cell & it swells Protein Pumps Transport proteins that require energy to do work. Example: Sodium / Potassium Pumps are important in nerve responses. (3 Na+ are moved out and 2 K+ are moved in) Endocytosis Materials ENTER the cell through a vesicle formed by the membrane Exocytosis Materials EXIT the cell through a vesicle formed by the Golgi Body