New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here


by: Corinne Caro

Chapter4;Physiology.pdf HCS 215

Corinne Caro
GPA 3.0
Dr. Diego Deleon

Almost Ready


These notes were just uploaded, and will be ready to view shortly.

Purchase these notes here, or revisit this page.

Either way, we'll remind you when they're ready :)

Preview These Notes for FREE

Get a free preview of these Notes, just enter your email below.

Unlock Preview
Unlock Preview

Preview these materials now for free

Why put in your email? Get access to more of this material and other relevant free materials for your school

View Preview

About this Document

Outline of Chapter 4 of Physiology
Dr. Diego Deleon
75 ?




Popular in Physiology

Popular in Nursing and Health Sciences

This 15 page Bundle was uploaded by Corinne Caro on Sunday October 25, 2015. The Bundle belongs to HCS 215 at University of Miami taught by Dr. Diego Deleon in Fall 2015. Since its upload, it has received 23 views. For similar materials see Physiology in Nursing and Health Sciences at University of Miami.

Popular in Nursing and Health Sciences


Reviews for Chapter4;Physiology.pdf


Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 10/25/15
CHAPTER 4 CELL MEMBRANE TRANSPORT l FACTORS AFFECTING THE DIRECTION OF TRANSPORT To get started right away just tap any placeholder text such as this and start typing A Energy Difference Energy difference in the molecule on the two sides of the membrane determines the direction of spontaneous transport passive transport and need for energy to move the molecule against the energy gradient active transport B Passive Transport vs Active Transport vi vii Viii Spontaneouspassive movement occurs from areas of high energy to areas of low energy when they need to move in opposite direction it requires an input of energy Energy of solute depends on solute concentration and charge if solute is ion energy increases as solute concentration increases Solutes move passively from an area where they are in greater concentration to an area where they are in lesser concentration To move from an area of low concentration to high requires input of energy Active transport transport of molecules across a membrane if it requires energy Passive transportdoes not require energy Simple diffusionthe movement of a molecule into or out of the cell by its own thermal motion one form of passive transport Active transport is always mediated by transport proteins referred to as pumps Glucose example 1 Concentration is 1 mM in intracellular uid but it is nearly 6mM in extracellular uid 2 If glucose is allowed to move spontaneousy across membrane of typical cell it Will move from area of higher concentration to area of lower concentration move into cell C 3 Transport of glucose in opposite direction from lower to higher is active because it requires energy and does not occur spontaneous y Driving Forces Acting on Molecules Driving forceany difference in energy existing across a membrane that tends to push molecules in one direction or another Direction is always higher to lower Driving forces can arise as a result of concentration differences or other factors that affect molecular energies Molecules are generally in uenced by three types of driving forces chemical electrical and electrochemical 1 Chemical Driving Forces a Concentration gradient when a substance is present in different concentrations on either side of a membrane this exists across a membrane When molecules are moving from higher to lower concentration we can say that they are moving down a concentration gradient movement in the opposite direction is up a concentration gradient Concentration gradient is a force that quotpushesquot molecules in a particular direction Chemical driving force the direction of which is always down the concentration gradient The rate at which a substance is transported varies with the size of the concentration gradient and generally increases as the size of the gradient increases When more than one substance is present as is the case with real cells more than one concentration eXists Any chemical driving force that might be acting on a given substance depends only on the concentration gradient of that particular substance Chemical driving force is fundamentally different does not act the same as the force of gra vity does when molecules move across a membrane down a concentration gradient they do so simply because more molecules are present on one side of the membrane than the other i Individual molecules are not pushed down the gradient but are equally likely to move in either direction j PAGE 96 for Photos to help Visualize 2 Electrical Driving Forces a Electrical driving forces arise due to membrane potential a difference in electrical potential or voltage that exists across the membrane of most cells b Membrane potential re ects an unequa distribution of positively charged ions and negatively charged ions across the plasma membrane c The membrane potential the uids in the body contain a Wide variety of solutes including many ions also called electrolytes substance possessing a chemical charge Cations have positive electrical charge Anions have negative electrical charge lons are also present in salt solutions such as sea water Something is considered electrically neutral beca use the positive and negative charges cancel each other out giving a total net charge of 0 Human s bodies are electrically neutral however a person can pick up or emit charges lntra cellularextracellular uid cations and anions are present in unequal numbers these uids are not electrically neutral lntra cellular uid contains a slight excess of anions over cations giving it a net negative charge Extracellular uids contain a slight excess of cations over anions giving it a net positive charge A separation of charge is said to exist across the membrane because positive and negative charges are distributed unequaly between the inside and outside of cell When charges are separated a potential energy voltage exists The excess negative and positive charges of intracellular and extracellular uid tend to be clustered close to the membrane because the excess negative charges on one side of the membrane are attracted to the excess positive charges on the other side A cell 5 membrane potential re ects the separation of charge and is given in units of electrical potential in milivots m V Which are 11000 of a volt The magnitude of the membrane potential depends on the degree of charge separation the greater the difference in charge between the two sides of a membrane the larger the membrane potential The sign of the membrane potential is taken to be the sign of the net charge inside the cell relative to outside 0 How the Membrane Potential Creates an Electrical Driving Force that Acts on Ions An electrical potential is a form of potential energy that is an electrical force acting on the charged particles and has potential to ca use those particles to move Current in biological systems is caused by ion movement the membrane potential creates an electrical driving force for the movement of ions To determine the direction of electrical driving force we need to know the valence or charge of the ion the sign of the membrane potential usualy negative Opposites attract likes repel Cations are attracted by the negative charge inside the cell and have an in ward directed electrical driving force Anions are repelled by the negative membrane potential and have an outwarddirected electrical driving force Uncharged molecules glucose are not affected by the membrane potential and therefore have an electrical driving force of zero The magnitude of the electrical driving force on an anion depends on the size of the membrane potential and the quantity of charge carried by the ion and it increases as either of these factors gets larger A larger negative membrane potential means a greater number of negative charges inside and positive charges outside which increases the attractive and repulsive forces acting on an ion If an ion carries more charge the attractive and repulsive forces are also increased which makes the electrical driving force stronger 3 Electrochemical Driving Forces a When ions are transported across membranes two driving forces are in uential 1chemical force re ecting the ions tendency to move down their concentration gradients from higher to lower and 2 electrical force re ecting the ion 5 tendency to be pushed in one direction or the other by the membrane potential b Electrochemical driving force the total force acting on the ions is a combination of these chemical and electrical driving forces also known as uncharged molecules which are not in uenced by electrical driving forces in this case the electrochemical driving force is synonymous with the chemical driving force c The direction of the electrochemical driving force acting on an ion depends on the net direction of the electrical and chemical driving forces 0 If both forces go in the same direction then the electrochemical driving force also acts in the same direction e If the electrical and chemical forces go in opposite directions then the electrochemical force acts in the direction of the larger force f To determine whether the electrical or chemical force is larger we need to know an ion 5 equilibrium potential hypothetical value for the membrane potential at which the electrical driving force is equal and opposite to the chemical driving force producing an electrochemical driving force of zero g If membrane potential equals the equilibrium potential for an ion that ion will not move spontaneously in either direction because the total driving force acting on it is zero Ion will be at equilibrium h Chemical reaction is at equilibrium when its net direction is neither forward nor backward i The magnitude and sign of the ion 5 equilibrium potential depend on the size and direction of the ion 5 concentration gradient and on the ion 5 valence Larger concentration gradients mean larger equilibrium potentials because a greater electrical force is required to equal or quotbalancequot a larger chemical force j The sign of the equilibrium potential is such that the electrical force goes in the direction opposite to the chemical force k Na sodium are found in higher concentration outside a cell the chemical force is directed in ward because it charged positivey a positive membrane potential will exert an outward electrical force that balances the in ward chemical force Na equilibrium potential must be positive Outwardy directed electrical force is required to balance the chemical force m Determining the Direction of the Electrochemical Driving Force STEPS FOR THIS PROCEDURE CAN BE FOUND ON PAGE 98 n Signi cance of Electrochemical Driving Force the electrochemical force is the total driving force acting of transported ions it determines the direction in which the ions move if they are allowed to cross the membrane spontaneousy when ions are transported passively they always move in the direction of the electrochemical driving force they move down their electrochemical gradient when transported actively they move in the direction opposite to the electrochemical force or up their electrochemical gradient Molecules cross the membrane by simple diffusion under two conditions 1 when their concentration is the same on both sides 2 when the concentration on the left side is twice that on the right side 2 RATE OF TRANSPORT A The rate of a metabolic transport is important because reactions must proceed at a rate fast enough to meet the body s metabolic demands molecules must be transported across membranes at suf cient rates The rate at which a substance is transported across a membrane refers to the number of molecules that cross the membrane in a given length of time which is called the ux Flux is usually expressed in units of moles per second or some equivalent Molecules cross a membrane by simple diffusion under two set conditions 1 when their concentration is the same on both sides 2 when the concentration on the left is twice than on the right Transport rates are in uenced by many variables some of which are speci c to certain transport mechanisms PAGES 101 102 HAS FIGURES FOR EXAMPLES OF RULES 3 PASSIVE TRANSPORT A Molecules move across the membrane down their chemical or electrochemical gradients no energy is required types of passive transports simple diffusion facilitated diffusion diffusion though ion channels B Simple Diffusion Passive Transport Through the Lipid Bilayer Least complicated of all transport mechanisms The Basis for Simple Diffusion l 2 Simple diffusion passive transport of molecules through a biological membrane s lipid bia yer but in fact the mechanism of simple diffusion is not strictly biological ex Perfume bottle Diffusionmovement of molecules from one location to another simply as a result of their own thermal motion Factors Affecting Rates of Simple Diffusion 1 When a substance is transported passivey across a membrane by simple diffusion the rate at which it is transported depends on three factors 1 Magnitude of driving force 2 the membrane of the surface area 3 the permeability of the membrane a measure of the ease with which molecules are able to move through it Magnitude of the Driving Force a When a driving force acts on molecules crossing a membrane it in uences not only the direction but also the rates at which they are transported b The net ux increases as the magnitude of the driving force increases not always though c In simple diffusion the rate of transport is directly related to the size of the driving force Membrane Surface Area a The rate at which molecules are transported across a membrane varies in direct proportion to the membrane s surface are b Various tissues are specialized for transport the pulmonary epithelium the intestinal epithelium walls of capillaries all have larger membrane surface areas which enhance ability of these tissues to transport large quantities of material quickly 4 Membrane Permeability a The permeability of a membrane to a particular substance depends on both the nature of the transported substance and the properties of the membrane other than surface area that in uence the ease with which molecules are able to penetrate it b For passive transport a higher permeability translates into a higher rate of transport other things being equal c Factors In uencing Permeability of Cell Membranes Lipid solubility of the diffusing substance hydrophobic substances of are the most lipid soluble whereas h ydrophilic substances are least lipid soluble the more lipid soluble a substance is the greater a membrane s permeability to that substance The size and shape of diffusing molecules Molecules vary considerably in their sizes physical dimensions and molecular weights and shapes larger molecules and those with more irregular shapes move through bia yer more slowly making permeability membrane lower Temperature molecules move faster at higher temperatures which increases permeability however not common in human body because body temperature is relati vel y constant Membrane Thickness tissue thickness varies considerably tissues specialized for transport have rea ti vely thin walls this thinness increases the permeability and enhances rate of transport Lipid solubility has the strongest in uence on permeability Substances that can be transported by simple diffusion fatty acids steroid hormones thyroid hormones oxygen carbon dioxide and fatsoluble vitamins A D E K C Facilitated Diffusion Passive Transport Utilizing Membrane Proteins ii Carriers in Facilitated Diffusion carrier is a transmembrane protein that binds molecules on one side of a membrane and transports them to one side by means of a conformational change they possess one or more binding sites that are usually speci c for molecules of certain substances or classes of substances examples are monosaccharides and amino acids to be transported a molecule must rst enter a binding site once the molecule is in the binding site the carrier undergoes a conformational change that exposes the binding site to the uid on the other side of the membrane molecule is free to dissociate from the carrier and be released into the uid conformational changes may be triggered by solute binding or may occur When binding sites are empty if a molecule does not bind to a site the carrier can then revert to its original conformation With the binding site empty the net ux of facilitated diffusion depends on the frequency of solute binding to the carrier molecule on the two sides of the membrane so net transport occurs from the side With a greater frequency of binding two factors affect the binding site 1 the affinity of the binding site on the carrier 2 the concentration gradient or electrochemical gradient if ions are being transported of the solute across the membrane an y difference in the binding of solute to carrier on either side of the membrane depends on the concentration gradient soute is most likely to bind the carrier When there is more solute present if a concentration gradient is present more solute binds to carriers When the binding sites are facing the side With the greater solute concentration if solute is present at the same concentration on both sides of the membrane then solute Will bind equaly When the carrier faces either side of the membrane and the net ux is zero if a concentration gradient exists the direction of the net ux is down the gradient iii Factors Affecting the Rate of Facilitated Diffusion 10 3 factors 1 transport rates of the individual carriers 2 the number of carriers in the membrane 3 the magnitude of the concentration or electrochemical gradient of the transported substance an increase in any of these factors translates into an increased rate of facilitate diffusion individual carriers transport molecules at different rates depending on their type PAGE 105 HAS FIGURE TO ILLUSTRATE When the concentration of molecules on one side of a membrane is high the likelihood that at any given time the binding sites are occupied by molecules is also high if concentration is high binding sites are occupied 100 of time cells can regulate the rate of facilitated diffusion by modifying the number of carriers that are present in the membrane an increase in the number of carriers Will increase the likelihood that solute will bind to carrier and be transported across the membrane D Diffusion Through Channels A channel is a transmembrane protein that transports molecules via a passageway or pore that extends from one side of the membrane to the other channels are usually speci c for certain substances or classes of substances lDiffusion of Water Through Aquaporins most water diffuses across cell membranes through aquaporins highly selective pores that permit water but no solutesto move across the membrane by diffusion 13 have been identi ed Water can also cross cell membranes through ion channels 2 Diffusion Through Ion Channels the mechanism of transport through an ion channel depends on the type of channel When a channel has numerous binding sites ions move through the pore by quotjumpingquot from one site to the next an empty channel 5 binding sites are accessible from both sides of the membrane at the same time in contrast for a carrier the sites are accessible from only one or the other at any given time 3 Factors affecting the Rate of Transport Through Ion Channels the rate of ion movements through channels depends on the transport rate of individual channels and the number of channels in the membrane the rate of individual channels varies depending on the type of channel channels that function primarily as pores ion movement follows the same basic principles as simple diffusion except that ions move down electrochemical gradient not just chemical gradient for ion channels with binding sites transport is generally slower and the channels can be saturated similar to what occurs with facilitated diffusion most ion channels can eXist in two conformations l a closed state 2 and open state in closed state ions cannot move through the channel in open ions diffuse through the channel down their electrochemical gradients the rate of transport depends on the number of quotopenquot ion channels 4 ACTIVE TRANSPORT A 11 The importance of active transport to the life of a cell is that some cells expend large amounts of energy as much as 40 of ATP Many things depend on active transport whether directly or indirectly generation of electrical signals in neurons and other excitable cells regulation of muscle contraction absorption of nutrients and water by the digestive system and body uid regulation by the kidneys Transport of a substance down an electrochemical gradient requires no energy transport of a substance up an electrochemical gradient requires an input of a substance up an electrochemical gradient requires energy because molecules are moving against the electrochemical force pushing them 2 rules for transport 1 if the direction of the net ux is down an electrochemical gradient the transport is passive 2 if the direction of the net ux is up electrochemical gradient the transport is active J K 12 Primary and Secondary active transport differ in the nature of the energy source Primary active transport uses ATP or some other chemical energy source directly to transport substances proteins involved are called pumps Secondary active transport is powered by a concentration gradient or an electrochemical gradient that was previously created by primary active transport Active transporters can harness energy to drive the transport of molecules in a preferred direction across a membrane Primary Active Transport The membrane proteins that perform primary active transport function both as transport proteins and enzymes Sodium and Potassium pump is present in every cell and is crucial to several important processes electrical signaling in neurons and absorption of glucose by intestinal epithelial cells For each cycle of the pump 3 Na ions are transported out of the cell and two K ions are transported into the cell transport is active in each case because both types of ions move up their electrochemical gradients Secondary Active Transport A transport protein couples the flow of one substance to that of another one substance moves passively down its electrochemical gradient in the process releasing energy that is then used to drive the movement of the other substance up its electrochemical gradient Cotransport the transport of two substances in the same direction Countertransport the transport of two substances in opposite direction PAGE 109 SHOWS FIGURE TO DESCRIBE PROCESSES WITH EXAMPLES Factors Affecting Rates of Active Transport Two factors of sole determinants of the rate at which molecules are actively transported across any membrane 1 the rate of transport by individual active transporters 2 the number of active transporters that are present in the membrane As either variable increases so does the rate of transport increases Transport rate can be in uenced by concentration of transported substance size of the electrochemical driving force for that substance L Coexistence of Active and Passive Transport Mechanisms in Cells PAGE 110 HAS CHARACTERISTICS OF TRANSPORT PROCESSES 5 OSMOSIS PASSIVE TRANSPORT OF WATER ACROSS MEMBRANE 6 A Water transport is important water transport is always passive unaffected by membrane potentials and is always driven by its own concentration gradient B Osmosis the flow of water across a membrane down its concentration The direction of passive water ow into or out of the cell depends on the direction of the water concentration gradient across the plasma membrane Osmolarity Known as the total solute particle concentration of a solution lsoosmotic two solutions having the same osmolarity Hyperosmotic a solution whose osmolarity is higher than another Hyposmoticsolution whose osmolarity is lower E Osmotic Pressure vi vii A solution39s total solute concentration As total solute concentration increases so does osmotic pressure Tonicity a function of the concentration of nonpermeating solutes outside a cell relative to the concentration inside the cell and it determines the behavior of a cell placed in the solution lsotonic when it does not alter cell volume when a cell comes into contact with an isotonic solution it neither shrinks nor swells Hypertonicshrink Hypotonicswell FIGURE 419 ON PAGE 113 EXPLAINS TONICITY VS OSMOLARITY TRANSPORT OF MATERIAL WITHIN MEMBRANEBOUND COMPARTMENTS 13 A Macromolecules are too large to cross the plasma membrane even with the assistance of proteins thus they are transported across with assistance of vesicles Endocytosismolecules in the extracellular uid enter the cell through the formation of vesicles calls endosomes B Transport of Molecules into Cells By Endocytosis Phagocytosiscell uses amoeboidlike movements of plasma membrane to extend the membrane around particulate matter in extracellular uid Pinocytosisplasma membrane develops an indentation and its outer edges pinch together to form an endosome in cytoplasm Receptormediated endocytosis speci c proteins in the plasma function as receptors that recognize and bind speci c particles in the extracellular uid Clathrin area of plasma membrane that forms the vesicle that is coated with proteins C Transport of Molecules Out of Cells by Exocytosis Three functions 1 Add components to the plasma membrane 2 To recycle receptors removed from the plasma membrane by endocytosis 3 To secrete speci c substrates out of the cell and into the extra cellular uid 7 EPITHELIAL TRANSPORT MOVEMENT ACROSS TWO MEMBRANES A Epithelial Structure Apical membrane membrane on the side that faces lumen of body cavity Basement membrane anchors the basolateral membrane and provides physical support for the epithelial layer B Epithelial Solute Transport C Epithelial Water Transport Epithelia absorb or secrete water by rst using the active transport of solutes to create a difference in osmotic pressure Because water ow occurs in response to transport of solutes water transport is said to be secondary to solute transport D Transcytosis 14 15 Macromolecules cross epithelial cells which involves both exocytosis and endocytosis A large molecule is take into the cell by endocytosis but the endocytotic vesicle does not fuse with a lysosome Vesicle travels to the opposite side of the cell and fuse with the plasma membrane to release its content by exocytosis


Buy Material

Are you sure you want to buy this material for

75 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Jim McGreen Ohio University

"Knowing I can count on the Elite Notetaker in my class allows me to focus on what the professor is saying instead of just scribbling notes the whole time and falling behind."

Jennifer McGill UCSF Med School

"Selling my MCAT study guides and notes has been a great source of side revenue while I'm in school. Some months I'm making over $500! Plus, it makes me happy knowing that I'm helping future med students with their MCAT."

Bentley McCaw University of Florida

"I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"


"Their 'Elite Notetakers' are making over $1,200/month in sales by creating high quality content that helps their classmates in a time of need."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.