Bio101 CHAPTER 5 Study Guide Questions 1 Attachment protein is proteins that attach to the extracellular matrix and cytoskeleton help support the membrane and can coordinate external and internal changes Receptor protein signaling molecules bind to receptor proteins which relay the message by activating other molecules inside the cell Active transport protein transport proteins allow specific ion or molecules to enter or exit the cell Junction protein membrane proteins may form intercellular junctions that attach adjacent cells Glycoprotein Glycoproteins may serve as ID tags that are recognized by membrane proteins of other cells Channel protein is a protein that allows the transport of specific substance across a cell membrane 2 Diffusion is the tendency of particles to spread out evenly in an available space Diffusion across a cell membrane does not require energy so it is called passive transport 3 Osmosis is the diffusion of water across a membrane Tonicity is a term that describes the ability of a surrounding solution to cause a cell to gain or lose water The control of water balance is called osmoregulation Toward the 2 side In an isotonic solution the concentration of solute is the same on both sides of a membrane and the cell volume will not change In a hypotonic solution the solute concentration is lower outside the cell water molecules move into the cell and the cell will expand and may burst In a hypertonic solution the solute concentration is higher outside the cell water molecules move into the cell and the cell will shrink 4 Polar or charged substances do not easily cross cell membranes and instead move across membranes with the help of specific transport proteins in a process called facilitated diffusion The very rapid diffusion of water into and out of certain cells is made possible by a protein channel called an aquaporin Bio101 5 In an active transport a cell must expend energy to move a solute against its concentration gradient Both require transport proteins for substances to move through But in facilitated diffusion the direction of the movement is still from areas of high concentration to low concentration and therefore no energy needs to be added to the system 6 First law of thermodynamics energy in the universe is constant Second law of thermodynamics energy conversions increases the disorder of the universe Kinetic energy is the energy of motion Potential energy is energy that matter possesses as a result of its location or structure Chemical reactions either released energy exergonic reactions or required an input of energy and store energy endergonic reactions Photosynthesis is an endergonic reaction Cellular respiration is an exergonic reaction Energy coupling uses the energy released from exergonic reactions to drive endergonic reactions typically using the energy stored in ATP molecules 7 Hydrolysis of ATP releases energy by transferring its third phosphate from ATP to some other molecule in a process called phosphorylation In the ATP cycle energy release an exergonic reaction such as the breakdown of glucose during cellular respiration is used in an endergonic reaction to generate ATP from ADP 8 An energy barrier must be overcome before a chemical reaction by lowering energy barriers this energy is called activation energy An enzyme is very selective reaction it catalyzes and has a shape that determines the enzyme s specificity Many enzymes require nonprotein helpers called cofactors which bind to the active site and function in catalysis If a cofactor is an organic molecule such as most vitamins it is called a coenzyme 9 Many beneficial drugs act as enzyme inhibition In some reactions the product may act as an inhibitor of one of the enzymes in the pathway that produced it This is called feedback inhibitions Bio101 Competitive inhibitors bind substrates from entering the active site and reduce an enzyme s productivity Noncompetitive inhibitors bind to the enzyme somewhere other than the active site change the shape of the active site and prevent the substrate from binding