Module 3 Life in Motion 01_AK PDF

Fluid dynamics: hydrodynamics of water and other fluids, fluid dynamics of blood Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Hydrodynamics of Water Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cum...

Fluid dynamics: hydrodynamics of water and other fluids, fluid dynamics of blood Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Hydrodynamics of Water Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Water as continuum: Though Fluids Are Composed of Molecules It Is Possible to Treat Them as a Continuous Medium Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Overview: The Molecule That Supports All of Life Water is the biological medium on Earth All living organisms require water more than any other substance Most cells are surrounded by water, and cells themselves are about 70–95% water The abundance of water is the main reason the Earth is habitable Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-1 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 3.1: The polarity of water molecules results in hydrogen bonding The water molecule is a polar molecule: The opposite ends have opposite charges Polarity allows water molecules to form hydrogen bonds with each other Animation: Water Structure Copyright © Copyright © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-2 – Hydrogen + bond H —— O – + —— H – + – + Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 3-UN1 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 3.2: Four emergent properties of water contribute to Earth’s fitness for life Four of water’s properties that facilitate an environment for life are: – Cohesive behavior – Ability to moderate temperature – Expansion upon freezing – Versatility as a solvent Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Cohesion Collectively, hydrogen bonds hold water molecules together, a phenomenon called cohesion Cohesion helps the transport of water against gravity in plants Adhesion is an attraction between different substances, for example, between water and plant cell walls Animation: Water Transport Copyright © Copyright © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-3 Adhesion Water-conducting cells Direction Cohesion of water 150 µm movement Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Surface tension is a measure of how hard it is to break the surface of a liquid Surface tension is related to cohesion Copyright © Copyright © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-4 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Moderation of Temperature Water absorbs heat from warmer air and releases stored heat to cooler air Water can absorb or release a large amount of heat with only a slight change in its own temperature Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Heat and Temperature Kinetic energy is the energy of motion Heat is a measure of the total amount of kinetic energy due to molecular motion Temperature measures the intensity of heat due to the average kinetic energy of molecules Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  The Celsius scale is a measure of temperature using Celsius degrees (°C) A calorie (cal) is the amount of heat required to raise the temperature of 1 g of water by 1°C The “calories” on food packages are actually kilocalories (kcal), where 1 kcal = 1,000 cal The joule (J) is another unit of energy where 1 J = 0.239 cal, or 1 cal = 4.184 J Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Water’s High Specific Heat The specific heat of a substance is the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1ºC The specific heat of water is 1 cal/g/ºC Water resists changing its temperature because of its high specific heat Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Water’s high specific heat can be traced to hydrogen bonding – Heat is absorbed when hydrogen bonds break – Heat is released when hydrogen bonds form The high specific heat of water minimizes temperature fluctuations to within limits that permit life Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-5 Burbank San Bernardino Santa Barbara 73° 90° 100° Los Angeles Riverside 96° (Airport) 75° Santa Ana Palm Springs 70s (°F) 84° 106° 80s Pacific Ocean 90s 100s San Diego 72° 40 miles Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Evaporative Cooling Evaporation is transformation of a substance from liquid to gas Heat of vaporization is the heat a liquid must absorb for 1 g to be converted to gas As a liquid evaporates, its remaining surface cools, a process called evaporative cooling Evaporative cooling of water helps stabilize temperatures in organisms and bodies of water Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Insulation of Bodies of Water by Floating Ice Ice floats in liquid water because hydrogen bonds in ice are more “ordered,” making ice less dense Water reaches its greatest density at 4°C If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-6 Hydrogen bond Ice Liquid water Hydrogen bonds are stable Hydrogen bonds break and re-form Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 3-6a Hydrogen bond Ice Liquid water Hydrogen bonds are stable Hydrogen bonds break and re-form Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  The Solvent of Life A solution is a liquid that is a homogeneous mixture of substances A solvent is the dissolving agent of a solution The solute is the substance that is dissolved An aqueous solution is one in which water is the solvent Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Water is a versatile solvent due to its polarity, which allows it to form hydrogen bonds easily When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules called a hydration shell Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-7 – Na+ + –+ – + – – Na+ – + + Cl– Cl– + – – + – + – – Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Water can also dissolve compounds made of nonionic polar molecules Even large polar molecules such as proteins can dissolve in water if they have ionic and polar regions Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-8 (a) Lysozyme molecule in a (b) Lysozyme molecule (purple) in an aqueous (c) Ionic and polar regions nonaqueous environment environment on the protein’s surface attract water molecules. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 3-8ab (a) Lysozyme molecule in a (b) Lysozyme molecule (purple) in an aqueous nonaqueous environment environment Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 3-8bc (b) Lysozyme molecule (purple) in an aqueous (c) Ionic and polar regions environment on the protein’s surface attract water molecules. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Hydrophilic and Hydrophobic Substances A hydrophilic substance is one that has an affinity for water A hydrophobic substance is one that does not have an affinity for water Oil molecules are hydrophobic because they have relatively nonpolar bonds A colloid is a stable suspension of fine particles in a liquid Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Solute Concentration in Aqueous Solutions Most biochemical reactions occur in water Chemical reactions depend on collisions of molecules and therefore on the concentration of solutes in an aqueous solution Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Molecular mass is the sum of all masses of all atoms in a molecule Numbers of molecules are usually measured in moles, where 1 mole (mol) = 6.02 x 1023 molecules Avogadro’s number and the unit dalton were defined such that 6.02 x 1023 daltons = 1 g Molarity (M) is the number of moles of solute per liter of solution Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Concept 3.3: Acidic and basic conditions affect living organisms A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other: – The hydrogen atom leaves its electron behind and is transferred as a proton, or hydrogen ion (H+) – The molecule with the extra proton is now a hydronium ion (H3O+), though it is often represented as H+ – The molecule that lost the proton is now a hydroxide ion (OH–) Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Water is in a state of dynamic equilibrium in which water molecules dissociate at the same rate at which they are being reformed Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-UN2 H H O H O O H O H H H H 2H2O Hydronium Hydroxide ion (H3O+) ion (OH–) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Though statistically rare, the dissociation of water molecules has a great effect on organisms Changes in concentrations of H+ and OH– can drastically affect the chemistry of a cell Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Effects of Changes in pH Concentrations of H+ and OH– are equal in pure water Adding certain solutes, called acids and bases, modifies the concentrations of H+ and OH– Biologists use something called the pH scale to describe whether a solution is acidic or basic (the opposite of acidic) Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Acids and Bases An acid is any substance that increases the H+ concentration of a solution A base is any substance that reduces the H+ concentration of a solution Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  The pH Scale In any aqueous solution at 25°C the product of H+ and OH– is constant and can be written as [H+][OH–] = 10– 14 The pH of a solution is defined by the negative logarithm of H+ concentration, written as pH = –log [H+] For a neutral aqueous solution [H+] is 10–7 = –(–7) = 7 Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Acidic solutions have pH values less than 7 Basic solutions have pH values greater than 7 Most biological fluids have pH values in the range of 6 to 8 Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-9 pH Scale 0 1 Battery acid Gastric juice, 2 lemon juice Increasingly Acidic H+ H+ H+ H+ OH 3 Vinegar, beer, – OH– H H+ + wine, cola [H+] > [OH–] H+ H+ Acidic 4 Tomato juice solution Black coffee 5 Rainwater 6 Urine OH– OH– Saliva Neutral H+ H OH– 7 Pure water [H+] = [OH–] + OH– OH– + Human blood, tears H+ H+ H 8 Seawater Neutral solution 9 Increasingly Basic 10 [H+] < [OH–] Milk of magnesia OH– OH– 11 OH– H+ OH– OH OH – – Household ammonia H+ OH– 12 Basic solution Household 13 bleach Oven cleaner 14 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Buffers The internal pH of most living cells must remain close to pH 7 Buffers are substances that minimize changes in concentrations of H+ and OH– in a solution Most buffers consist of an acid-base pair that reversibly combines with H+ Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Threats to Water Quality on Earth Acid precipitation refers to rain, snow, or fog with a pH lower than 5.6 Acid precipitation is caused mainly by the mixing of different pollutants with water in the air and can fall at some distance from the source of pollutants Acid precipitation can damage life in lakes and streams Effects of acid precipitation on soil chemistry are contributing to the decline of some forests Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-10 0 More 1 acidic 2 3 Acid 4 rain 5 Normal 6 rain 7 8 9 10 11 12 13 More 14 basic Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Human activities such as burning fossil fuels threaten water quality CO2 is released by fossil fuel combustion and contributes to: – A warming of earth called the “greenhouse” effect – Acidification of the oceans; this leads to a decrease in the ability of corals to form calcified reefs Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings Fig. 3-11 EXPERIMENT RESULTS 40 Calcification rate per m2 per day) (mmol CaCO3 20 0 150 200 250 300 [CO32–] (µmol/kg) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 3-11a EXPERIMENT Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 3-11b RESULTS Calcification rate per m2 per day) 40 (mmol CaCO3 20 0 150 200 250 300 [CO32–] (µmol/kg) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 3-UN3 – Hydrogen + bond H – O + H – + + – Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 3-UN4 Ice: stable hydro- Liquid water: gen bonds transient hydrogen bonds Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 3-UN5 0 Acidic [H+] > [OH–] Acids donate H+ in aqueous solutions Neutral [H+] = [OH–] 7 Bases donate OH– or accept H+ in Basic aqueous solutions [H+] < [OH–] 14 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 3-UN6 Surface of Mars Surface of Earth Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 3-UN7 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  You should now be able to: 1. List and explain the four properties of water that emerge as a result of its ability to form hydrogen bonds 2. Distinguish between the following sets of terms: hydrophobic and hydrophilic substances; a solute, a solvent, and a solution 3. Define acid, base, and pH 4. Explain how buffers work Copyright Copyright © © 2008 2008 Pearson Pearson Education, Education, Inc., Inc., publishing publishing as as Pearson Pearson Benjamin Benjamin Cummings Cummings  Fluid Dynamics of Blood Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: Trading Places Every organism must exchange materials with its environment. Exchanges ultimately occur at the cellular level. In unicellular organisms, these exchanges occur directly with the environment. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  For most cells making up multicellular organisms, direct exchange with the environment is not possible. Gills are an example of a specialized exchange system in animals. Internal transport and gas exchange are functionally related in most animals. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How does a feathery fringe help this animal survive? Circulatory systems link exchange surfaces with cells throughout the body In small and/or thin animals, cells can exchange materials directly with the surrounding medium. In most animals, transport systems connect the organs of exchange with the body cells. Most complex animals have internal transport systems that circulate fluid. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Gastrovascular Cavities Simple animals, such as cnidarians, have a body wall that is only two cells thick and that encloses a gastrovascular cavity. This cavity functions in both digestion and distribution of substances throughout the body. Some cnidarians, such as jellies, have elaborate gastrovascular cavities. Flatworms have a gastrovascular cavity and a large surface area to volume ratio. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Internal transport in gastrovascular cavities Circular canal Mouth Pharynx Mouth Radial canal 5 cm 2 mm (a) The moon jelly Aurelia, a cnidarian (b) The planarian Dugesia, a flatworm Open and Closed Circulatory Systems More complex animals have either open or closed circulatory systems. Both systems have three basic components: – A circulatory fluid = blood or hemolymph. – A set of tubes = blood vessels. – A muscular pump = the heart. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  In insects, other arthropods, and most molluscs, blood bathes the organs directly in an open circulatory system. In an open circulatory system, there is no distinction between blood and interstitial fluid, and this general body fluid is more correctly called hemolymph. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  In a closed circulatory system, the blood is confined to vessels and is distinct from the interstitial fluid. Closed systems are more efficient at transporting circulatory fluids to tissues and cells. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Open and closed circulatory systems Heart Heart Blood Hemolymph in sinuses Interstitial Small branch vessels surrounding organs fluid In each organ Pores Dorsal vessel (main heart) Tubular heart Auxiliary hearts Ventral vessels (a) An open circulatory system (b) A closed circulatory system Organization of Vertebrate Closed Circulatory Systems Humans and other vertebrates have a closed circulatory system, often called the cardiovascular system. The three main types of blood vessels are: arteries - away from the heart. veins - toward the heart. capillaries - exchange with body cells. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Arteries branch into arterioles and carry blood to capillaries. Networks of capillaries called capillary beds are the sites of chemical exchange between the blood and interstitial fluid. Venules converge into veins and return blood from capillaries to the heart. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Vertebrate hearts contain two or more chambers. Blood enters through an atrium and is pumped out through a ventricle. Atria - receive blood Ventricles - pump blood Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Single Circulation Bony fishes, rays, and sharks have single circulation with a two-chambered heart. In single circulation, blood leaving the heart passes through two capillary beds before returning. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Single Gill capillaries circulation in fishes Artery Gill circulation Ventricle Heart Atrium Systemic Vein circulation Systemic capillaries Double Circulation Amphibian, reptiles, and mammals have double circulation. Oxygen-poor and oxygen-rich blood are pumped separately from the right and left sides of the heart. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Double circulation in vertebrates Mammals and Amphibians Reptiles Birds Lung and skin capillaries Lung capillaries Lung capillaries Pulmocutaneous Right Pulmonary Pulmonary circuit systemic circuit circuit aorta Atrium (A) Atrium (A) A A A A Ventricle (V) V V Left V V Right Left Right Left systemic Right Left Systemic aorta Systemic circuit circuit Systemic capillaries Systemic capillaries Systemic capillaries  In reptiles and mammals, oxygen-poor blood flows through the pulmonary circuit to pick up oxygen through the lungs. In amphibians, oxygen-poor blood flows through a pulmocutaneous circuit to pick up oxygen through the lungs and skin. Oxygen-rich blood delivers oxygen through the systemic circuit. Double circulation maintains higher blood pressure in the organs than does single circulation. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Adaptations of Double Circulatory Systems Amphibians: Frogs / amphibians have a three-chambered heart: 2 atria and 1 ventricle. The ventricle pumps blood into a forked artery that splits the ventricle’s output into the pulmocutaneous circuit and the systemic circuit. Underwater, blood flow to the lungs is nearly shut off. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Reptiles (Except Birds) Turtles, snakes, and lizards have a three- chambered heart: two atria and one ventricle. In alligators, caimans, and other crocodilians a septum - partially or fully divides the ventricle. Reptiles have double circulation, with a pulmonary circuit - lungs and a systemic circuit. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  RA --> RV --> LUNGS --> LA --> LV --> Body Mammals Mammals and birds have a four-chambered heart with two atria and two ventricles. The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood. Mammals and birds are endotherms and require more O2 than ectotherms. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Coordinated cycles of heart contraction drive double circulation in mammals Blood begins its flow with the right ventricle pumping blood to the lungs. In the lungs, the blood loads O2 and unloads CO2 Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped through the aorta to the body tissues by the left ventricle. The aorta provides blood to the heart through the coronary arteries. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Blood returns to the heart through the superior vena cava (deoxygenated blood from head, neck, and forelimbs) and inferior vena cava (deoxygenated blood from trunk and hind limbs). The superior vena cava and inferior vena cava flow into the Right Atrium - RA. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Superior vena cava 7 Capillaries of head and Returns deoxygenated blood from Forelimbs - EXCHANGE body to heart RA Pulmonary artery Pulmonary artery Carries deoxygenated blood to lungs Capillaries Aorta 9 Capillaries of right Lung GAS EXCHANGE of left Lung GAS EXCHANGE 3 2 3 4 11 Pulmonary vein Pulmonary vein Carries oxygenated blood 5 to heart: LA 1 Right Atrium Left Atrium - LA RA - Receives deoxygenated blood 10 Receives oxygenated blood from body from lungs Right Ventricle Left Ventricle - LV RV - Pumps blood to lungs Pumps oxygenated blood to body Inferior vena cava Aorta = main artery to body Returns deoxygenated blood from for Systemic Circulation body to heart RA mammalian 8 Capillaries of abdominal organs and hind limbs cardiovascular system EXCHANGE with body cells The Mammalian Heart: A Closer Look A closer look at the mammalian heart provides a better understanding of double circulation. RIGHT side = deoxygenated blood from body pumped to lungs. LUNGS = gas exchange. LEFT side = oxygenated blood from lungs pumped to body. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Pulmonary artery Mammalian Heart Aorta - systemic - to lungs circulation Right Atrium RA Pulmonary veins - Receives from lungs to heart Deoxygented Blood from Left Atrium LA body Receives oxgenated blood from lungs Semilunar Semilunar valve valve Atrioventricular Atrioventricular valve valve Right Ventricle RV Left Ventricle LV Pumps to lungs for Pumps oxygenated gas exchange blood to body via aorta  The heart contracts and relaxes in a rhythmic cycle called the cardiac cycle. The contraction, or pumping, phase is called systole. The relaxation, or filling, phase is called diastole. Blood Pressure = systolic / diastolic Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cardiac 2 Atrial systole; Semilunar cycle valves ventricular diastole closed 0.1 sec Semilunar AV valves valves 0.4 sec 0.3 sec open open 1 Atrial and ventricular diastole AV valves closed 3 Ventricular systole; atrial diastole  The heart rate, also called the pulse, is the number of beats per minute. The stroke volume is the amount of blood pumped in a single contraction. The cardiac output is the volume of blood pumped into the systemic circulation per minute and depends on both the heart rate and stroke volume. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Four valves prevent backflow of blood in the heart: The atrioventricular (AV) valves separate each atrium and ventricle. The semilunar valves control blood flow to the aorta and the pulmonary artery. The “lub-dup” sound of a heart beat is caused by the recoil of blood against the AV valves (lub) then against the semilunar (dup) valves. Backflow of blood through a defective valve causes a heart murmur. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Maintaining the Heart’s Rhythmic Beat Some cardiac muscle cells are self-excitable = they contract without any signal from the nervous system. The sinoatrial (SA) node, or pacemaker, sets the rate and timing at which cardiac muscle cells contract. Impulses from the SA node travel to the atrioventricular (AV) node. At the AV node, the impulses are delayed and then travel to the Purkinje fibers that make the ventricles contract. Impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG or EKG). The pacemaker is influenced by nerves, hormones, body temperature, and exercise. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Control of heart rhythm 1 Pacemaker 2 Signals are 3 Signals pass 4 Signals spread generates wave of delayed at to heart apex. throughout signals to contract. AV node. ventricles. AV SA node node (pacemaker) Bundle Purkinje Fibers: branches Heart ventricles contract apex ECG Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels The physical principles that govern movement of water in plumbing systems also influence the functioning of animal circulatory systems. The epithelial layer that lines blood vessels is called the endothelium. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Structure Artery Vein of blood vessels SEM 100 µm Valve Basal lamina Endothelium Endothelium Smooth Smooth muscle muscle Connective Connective tissue Capillary tissue Artery Vein Arteriole Venule 15 µm Red blood cell Capillary LM  Capillaries have thin walls, the endothelium plus its basement membrane, to facilitate the exchange of materials. Arteries and veins have an endothelium, smooth muscle, and connective tissue. Arteries have thicker walls than veins to accommodate the high pressure of blood pumped from the heart. In the thinner-walled veins, blood flows back to the heart mainly as a result of muscle action. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Blood Flow Velocity Physical laws governing movement of fluids through pipes affect blood flow and blood pressure. Velocity of blood flow is slowest in the capillary beds, as a result of the high resistance and large total cross-sectional area. Blood flow in capillaries is necessarily slow for exchange of materials. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The interrelationship of cross-sectional area of blood vessels, blood flow velocity, and blood pressure. 5,000 Area (cm2) 4,000 3,000 2,000 1,000 0 50 40 (cm/sec) Velocity 30 20 10 0 120 Systolic 100 pressure Pressure (mm Hg) 80 60 40 Diastolic 20 pressure 0 Capillaries Venules Arterioles Aorta Veins Venae cavae Arteries Blood Pressure Blood pressure is the hydrostatic pressure that blood exerts against the wall of a vessel. In rigid vessels blood pressure is maintained; less rigid vessels deform and blood pressure is lost. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Changes in Blood Pressure During the Cardiac Cycle Systolic pressure is the pressure in the arteries during ventricle contraction /systole; it is the highest pressure in the arteries. Diastolic pressure is the pressure in the arteries during relaxation /diastole; it is lower than systolic pressure. A pulse is the rhythmic bulging of artery walls with each heartbeat. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Regulation of Blood Pressure Blood pressure is determined by cardiac output and peripheral resistance due to constriction of arterioles. Vasoconstriction is the contraction of smooth muscle in arteriole walls; it increases blood pressure. Vasodilation is the relaxation of smooth muscles in the arterioles; it causes blood pressure to fall. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Vasoconstriction and vasodilation help maintain adequate blood flow as the body’s demands change. The peptide endothelin is an important inducer of vasoconstriction. Blood pressure is generally measured for an artery in the arm at the same height as the heart. Blood pressure for a healthy 20 year old at rest is 120 mm Hg at systole / 70 mm Hg at diastole. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Question: How do endothelial cells control vasoconstriction? RESULTS Ser Leu Ser Endothelin Met Cys Ser Cys —NH+ 3 Asp Lys Glu Cys Val Tyr Phe Cys His Leu Asp Ile Ile Trp —COO– Cys Trp Parent polypeptide 1 53 73 Endothelin 203 Measurement of blood pressure: sphygmomanometer Blood pressure reading: 120/70 Pressure in cuff Pressure in cuff Pressure in greater than drops below cuff below 120 mm Hg 120 mm Hg 70 mm Hg Rubber cuff inflated 120 120 with air 70 Artery Sounds Sounds closed audible in stop stethoscope  Fainting is caused by inadequate blood flow to the head. Animals with longer necks require a higher systolic pressure to pump blood a greater distance against gravity. Blood is moved through veins by smooth muscle contraction, skeletal muscle contraction, and expansion of the vena cava with inhalation. One-way valves in veins / heart prevent backflow of blood. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Blood flow in veins Direction of blood flow in vein (toward heart) Valve (open) Skeletal muscle Valve (closed) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Capillary Function Capillaries in major organs are usually filled to capacity. Blood supply varies in many other sites. Two mechanisms regulate distribution of blood in capillary beds: – Contraction of the smooth muscle layer in the wall of an arteriole constricts the vessel. – Precapillary sphincters control flow of blood between arterioles and venules. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Blood flow Thoroughfare in capillary Precapillary sphincters channel beds Capillaries Arteriole Venule (a) Sphincters relaxed Arteriole Venule (b) Sphincters contracted  The critical exchange of substances between the blood and interstitial fluid takes place across the thin endothelial walls of the capillaries. The difference between blood pressure and osmotic pressure drives fluids out of capillaries at the arteriole end and into capillaries at the venule end. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fluid Body tissue exchange INTERSTITIAL FLUID between Capillary Net fluid capillaries movement out Net fluid and the movement in interstitial fluid Direction of blood flow Blood pressure = hydrostatic pressure Inward flow Pressure Outward flow Osmotic pressure Arterial end of capillary Venous end Fluid Return by the Lymphatic System The lymphatic system - returns fluid that leaks out in the capillary beds … restoring filtered fluid to blood maintains homeostasis. This system aids in body defense. Fluid, called lymph, reenters the circulation directly at the venous end of the capillary bed and indirectly through the lymphatic system. The lymphatic system drains into neck veins. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Lymph nodes are organs that produce phagocytic white blood cells and filter lymph - an important role in the body’s defense. Edema is swelling caused by disruptions in the flow of lymph. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Blood Composition and Function Blood consists of several kinds of blood cells suspended in a liquid matrix called plasma. The cellular elements: red blood cells, white blood cells, and platelets occupy about 45% of the volume of blood. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Composition of mammalian blood Plasma 55% Constituent Major functions Cellular elements 45% Cell type Number Functions Water Solvent for per µL (mm3) of blood carrying other substances Erythrocytes 5–6 million Transport oxygen (red blood cells) and help transport Ions (blood electrolytes) carbon dioxide Sodium Osmotic balance, Separated Potassium pH buffering, and blood Calcium regulation of elements Magnesium membrane Chloride permeability Bicarbonate Leukocytes 5,000–10,000 Defense and (white blood cells) immunity Plasma proteins Albumin Osmotic balance pH buffering Basophil Lymphocyte Fibrinogen Clotting Immunoglobulins Defense Eosinophil (antibodies) Neutrophil Monocyte Substances transported by blood Nutrients (such as glucose, fatty acids, vitamins) Waste products of metabolism Platelets 250,000– Blood clotting Respiratory gases (O2 and CO2) 400,000 Hormones Plasma Blood plasma is about 90% water. Among its solutes are inorganic salts in the form of dissolved ions, sometimes called electrolytes. Another important class of solutes is the plasma proteins, which influence blood pH, osmotic pressure, and viscosity. Various plasma proteins function in lipid transport, immunity, and blood clotting. Plasma transports nutrients, gases, and cell waste. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cellular Elements Suspended in blood plasma are two types of cells: – Red blood cells rbc = erythrocytes, transport oxygen. – White blood cells wbc = leukocytes, function in defense. Platelets are fragments of cells that are involved in blood clotting. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Erythrocytes - Oxygen Transport Red blood cells, or erythrocytes, are by far the most numerous blood cells. They transport oxygen throughout the body. They contain hemoglobin, the iron-containing protein that transports oxygen. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Leukocytes - Defense There are five major types of white blood cells, or leukocytes: monocytes, neutrophils, basophils, eosinophils, and lymphocytes. They function in defense by phagocytizing bacteria and debris or by producing antibodies. They are found both in and outside of the circulatory system. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Platelets - Blood Clotting Platelets are fragments of cells and function in blood clotting. When the endothelium of a blood vessel is damaged, the clotting mechanism begins. A cascade of complex reactions converts fibrinogen to fibrin, forming a clot. A blood clot formed within a blood vessel is called a thrombus and can block blood flow. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Blood clotting Red blood cell Collagen fibers Platelet plug Fibrin clot Platelet releases chemicals that make nearby platelets sticky Clotting factors from: Platelets Damaged cells Plasma (factors include calcium, vitamin K) Prothrombin Thrombin Fibrinogen Fibrin 5 µm Stem Cells and the Replacement of Cellular Elements The cellular elements of blood wear out and are replaced constantly throughout a person’s life. Erythrocytes, leukocytes, and platelets all develop from a common source of stem cells in the red marrow of bones. The hormone erythropoietin (EPO) stimulates erythrocyte production when oxygen delivery is low. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Differentiation of Blood Cells Stem cells in bone marrow Lymphoid Myeloid stem cells stem cells Lymphocytes B cells T cells Erythrocytes Neutrophils Platelets Eosinophils Monocytes Basophils Cardiovascular Disease = Disorders of the Heart and the Blood Vessels One type of cardiovascular disease, atherosclerosis, is caused by the buildup of plaque deposits within arteries. A heart attack is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries. A stroke is the death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the brain /head. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Atherosclerosis Connective Smooth tissue muscle Endothelium Plaque (a) Normal artery 50 µm (b) Partly clogged artery 250 µm Treatment and Diagnosis of Cardiovascular Disease Cholesterol is a major contributor to atherosclerosis. Low-density lipoproteins (LDLs) = “bad cholesterol,” are associated with plaque formation. High-density lipoproteins (HDLs) = “good cholesterol,” reduce the deposition of cholesterol. Hypertension = high blood pressure, promotes atherosclerosis and increases the risk of heart attack and stroke. Hypertension can be reduced by dietary changes, exercise, and/or medication. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Adaptations for gas exchange include pigments that bind and transport gases The metabolic demands of many organisms require that the blood transport large quantities of O2 and CO2 Blood arriving in the lungs has a low partial pressure of O2 and a high partial pressure of CO2 relative to air in the alveoli. In the alveoli, O2 diffuses into the blood and CO2 diffuses into the air. In tissue capillaries, partial pressure gradients favor diffusion of O2 into the interstitial fluids and CO2 into the blood. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Loading and unloading of respiratory gases Alveolus Alveolus PO2 = 100 mm Hg PCO2 = 40 mm Hg PO2 = 40 PO2 = 100 PCO2 = 46 PCO2 = 40 Circulatory Circulatory system system PO2 = 40 PO2 = 100 PCO2 = 46 PCO2 = 40 PO2 ≤ 40 mm Hg PCO2 ≥ 46 mm Hg Body tissue Body tissue (a) Oxygen (b) Carbon dioxide Hemoglobin A single hemoglobin molecule can carry four molecules of O2 The hemoglobin dissociation curve shows that a small change in the partial pressure of oxygen can result in a large change in delivery of O2 CO2 produced during cellular respiration lowers blood pH and decreases the affinity of hemoglobin for O2 This is called the Bohr shift. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings   Chains Iron Heme  Chains Hemoglobin  100 Dissociation O2 unloaded O2 saturation of hemoglobin (%) to tissues 80 at rest curves for 60 O2 unloaded hemoglobin to tissues during exercise 40 at 37ºC 20 0 0 20 40 60 80 100 Tissues during Tissues Lungs exercise at rest PO2 (mm Hg) (a) PO and hemoglobin dissociation at pH 7.4 2 100 O2 saturation of hemoglobin (%) pH 7.4 80 pH 7.2 60 Hemoglobin retains less 40 O2 at lower pH (higher CO2 20 concentration) 0 0 20 40 60 80 100 PO2 (mm Hg) (b) pH and hemoglobin dissociation  Membrane Structure and Function Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Overview: Life at the Edge The plasma membrane is the boundary that separates the living cell from its surroundings The plasma membrane exhibits selective permeability, allowing some substances to cross it more easily than others Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-1 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 7.1: Cellular membranes are fluid mosaics of lipids and proteins Phospholipids are the most abundant lipid in the plasma membrane Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Membrane Models: Scientific Inquiry Membranes have been chemically analyzed and found to be made of proteins and lipids Scientists studying the plasma membrane reasoned that it must be a phospholipid bilayer Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-2 WATER Hydrophilic head Hydrophobic tail WATER Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  In 1935, Hugh Davson and James Danielli proposed a sandwich model in which the phospholipid bilayer lies between two layers of globular proteins Later studies found problems with this model, particularly the placement of membrane proteins, which have hydrophilic and hydrophobic regions In 1972, J. Singer and G. Nicolson proposed that the membrane is a mosaic of proteins dispersed within the bilayer, with only the hydrophilic regions exposed to water Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-3 Phospholipid bilayer Hydrophobic regions Hydrophilic of protein regions of protein Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Freeze-fracture studies of the plasma membrane supported the fluid mosaic model Freeze-fracture is a specialized preparation technique that splits a membrane along the middle of the phospholipid bilayer Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-4 TECHNIQUE RESULTS Extracellular layer Proteins Inside of extracellular layer Knife Plasma membrane Cytoplasmic layer Inside of cytoplasmic layer Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  The Fluidity of Membranes Phospholipids in the plasma membrane can move within the bilayer Most of the lipids, and some proteins, drift laterally Rarely does a molecule flip-flop transversely across the membrane Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-5 Lateral movement Flip-flop (~107 times per second) (~ once per month) (a) Movement of phospholipids Fluid Viscous Unsaturated hydrocarbon Saturated hydro- tails with kinks carbon tails (b) Membrane fluidity Cholesterol (c) Cholesterol within the animal cell membrane Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-5a Lateral movement Flip-flop (107 times per ( once per second)of (a) Movement month) phospholipids Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-6 RESULTS Membrane proteins Mixed proteins after 1 hour Mouse cell Human cell Hybrid cell Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  As temperatures cool, membranes switch from a fluid state to a solid state The temperature at which a membrane solidifies depends on the types of lipids Membranes rich in unsaturated fatty acids are more fluid that those rich in saturated fatty acids Membranes must be fluid to work properly; they are usually about as fluid as salad oil Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-5b Flui Viscou d s Unsaturated Saturated hydrocarbon hydro- tails (b) with kinks Membrane carbon tails fluidity Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  The steroid cholesterol has different effects on membrane fluidity at different temperatures At warm temperatures (such as 37°C), cholesterol restrains movement of phospholipids At cool temperatures, it maintains fluidity by preventing tight packing Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-5c Cholester ol (c) Cholesterol within the animal cell membrane Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Membrane Proteins and Their Functions A membrane is a collage of different proteins embedded in the fluid matrix of the lipid bilayer Proteins determine most of the membrane’s specific functions Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-7 Fibers of extracellular matrix (ECM) Glyco- Carbohydrate protein Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Cholesterol Microfilaments Peripheral of cytoskeleton proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Peripheral proteins are bound to the surface of the membrane Integral proteins penetrate the hydrophobic core Integral proteins that span the membrane are called transmembrane proteins The hydrophobic regions of an integral protein consist of one or more stretches of nonpolar amino acids, often coiled into alpha helices Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-8 N-terminus EXTRACELLULAR SIDE C-terminus CYTOPLASMIC  Helix SIDE Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Six major functions of membrane proteins: – Transport – Enzymatic activity – Signal transduction – Cell-cell recognition – Intercellular joining – Attachment to the cytoskeleton and extracellular matrix (ECM) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-9 Signaling molecule Enzymes Receptor ATP Signal transduction (a) Transport (b) Enzymatic activity (c) Signal transduction Glyco- protein (d) Cell-cell recognition (e) Intercellular joining (f) Attachment to the cytoskeleton and extracellular matrix (ECM) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-9ac Signaling molecule Enzymes Receptor ATP Signal transduction (a) Transport (b) Enzymatic activity (c) Signal transduction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-9df Glyco- protein (d) Cell-cell recognition (e) Intercellular joining (f) Attachment to the cytoskeleton and extracellular matrix (ECM) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Role of Membrane Carbohydrates in Cell-Cell Recognition Cells recognize each other by binding to surface molecules, often carbohydrates, on the plasma membrane Membrane carbohydrates may be covalently bonded to lipids (forming glycolipids) or more commonly to proteins (forming glycoproteins) Carbohydrates on the external side of the plasma membrane vary among species, individuals, and even cell types in an individual Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Synthesis and Sidedness of Membranes Membranes have distinct inside and outside faces The asymmetrical distribution of proteins, lipids, and associated carbohydrates in the plasma membrane is determined when the membrane is built by the ER and Golgi apparatus Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-10 ER 1 Transmembrane glycoproteins Secretory protein Glycolipid Golgi 2 apparatus Vesicle 3 Plasma membrane: Cytoplasmic face 4 Extracellular face Transmembrane Secreted glycoprotein protein Membrane glycolipid Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 7.2: Membrane structure results in selective permeability A cell must exchange materials with its surroundings, a process controlled by the plasma membrane Plasma membranes are selectively permeable, regulating the cell’s molecular traffic Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  The Permeability of the Lipid Bilayer Hydrophobic (nonpolar) molecules, such as hydrocarbons, can dissolve in the lipid bilayer and pass through the membrane rapidly Polar molecules, such as sugars, do not cross the membrane easily Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Transport Proteins Transport proteins allow passage of hydrophilic substances across the membrane Some transport proteins, called channel proteins, have a hydrophilic channel that certain molecules or ions can use as a tunnel Channel proteins called aquaporins facilitate the passage of water Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Other transport proteins, called carrier proteins, bind to molecules and change shape to shuttle them across the membrane A transport protein is specific for the substance it moves Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment Diffusion is the tendency for molecules to spread out evenly into the available space Although each molecule moves randomly, diffusion of a population of molecules may exhibit a net movement in one direction At dynamic equilibrium, as many molecules cross one way as cross in the other direction Animation: Membrane Selectivity Animation: Diffusion Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-11 Molecules of dye Membrane (cross section) WATER Net diffusion Net diffusion Equilibrium (a) Diffusion of one solute Net diffusion Net diffusion Equilibrium Net diffusion Net diffusion Equilibrium (b) Diffusion of two solutes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-11a Molecules of dye Membrane (cross section) WATER Net diffusion Net diffusion Equilibrium (a) Diffusion of one solute Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  Substances diffuse down their concentration gradient, the difference in concentration of a substance from one area to another No work must be done to move substances down the concentration gradient The diffusion of a substance across a biological membrane is passive transport because it requires no energy from the cell to make it happen Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-11b Net diffusion Net diffusion Equilibrium Net diffusion Net diffusion Equilibrium (b) Diffusion of two solutes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Effects of Osmosis on Water Balance Osmosis is the diffusion of water across a selectively permeable membrane Water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Copyright Cummings© 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 7-12 Lower Higher Same concentration concentration concentration of sugar of solute (sugar) of sugar H2O