Gas Exchange

Where does gas exchange occur in a mammalian lung?

alveoli

Describe the structure of lung tissue as viewed in a light microscope.

spongy. lots of space

Why are the epithelia of the capillaries and the alveoli so thin?

A thin epithelial layer is needed because rapid diffusion of gas occurs between the capillaries and the alveoli The alveoli use simple epithelium so that gases can easily diffuses to and from the bloodstream.

How is carbon dioxide transported in the circulatory system? In which chemical form is carbon dioxide transported?

3 different modes of transport: 1) (70%) Carbon dioxide molecules are transported in the blood from body tissues to the lungs by one of three methods: Dissolution directly into the blood. Binding to hemoglobin. Carried as a bicarbonate ion. 2) (5%) straight CO2 dissolved in plasma fluids 3) (25%) CO2 binds with amino groups present in hemoglobin. Does not bind to heme compound like oxygen.

What is a heme group? What is its function?

A heme group composes hemoglobin. There are 4 heme groups heme is an iron-containing compound giving the red color to blood. Each heme group contains one iron atom that can bind one oxygen molecule through ion-induced dipole forces

What are the basic characteristics of a lung?

A sac that is in contact with a capillary network and connected to the pharynx. Lung systems have some sort of muscle to ventilate Most elaborate of all are mammalian lungs containing millions of small sacs called "alveoli" lung parabronchi: One cell thick air capillaries where gas exchange occurs The main function of the lungs is the process of gas exchange called respiration

Explain the process of negative pressure breathing.

A way to suck in air The diaphragm contracts and move down, the intercostal muscles contract and move up and out. This causes the lungs to expand. The pressure inside the lungs drops. The negative pressure sucks air in. For us humans, negative pressure ventilation is the normal physiologic way we breathe.

What is the function of the air sacs found within many insects?

Air sacs are found as tiny sacs off the larger breathing tubes (tracheae) of insects They serve to increase respiratory efficiency by providing a large surface area for gas exchange. Pump out old air while the insect is moving

What is the importance of the alveoli?

Alveoli are tiny sacs within the lungs that allow oxygen and carbon dioxide to move between the lungs and bloodstream The air in the alveoli is oxygen rich The Alveoli hugely increase the surface area of the lungs which is important for diffusion.

What factors control breathing in a human? Where is the breathing control center located?

Amount of CO2 present in the blood as Carbonic acid affects rate of breathing. This is because presence of carbonic acid can really reduce blood Ph levels. Control center is the medulla oblongata The medulla oblongata detects the levels of oxygen and carbon dioxide concentrations and signals the muscles in the heart, the lungs, and the diaphragm to increase or decrease the breathing. The pons control the speed of inhalation and exhalation or respiration rate depending on the need of the body.

How does the amount of available oxygen vary between aquatic and terrestrial environments?

Aquatic Environments: Limited availability. Dissolved oxygen increases with decreasing temperature and decreases with depth. Terrestrial Environments: Are readily available in the air. Air contains about 20% oxygen and 0.03% carbon dioxide. However, availability of gas may be a limiting factor at high altitudes.

How does the gas exchange process occur in a book lung? Is the circulatory system involved in the process?

Book lungs are the main respiratory organ in most arachnids (Spiders and scorpions) Book lungs consist of a series of haemolymph filled plate-like structures. Between the plates there is an air space and this allows air to circulate around the plates.

How does a crocodile produce its negative pressure in its breathing process?

By pulling its diaphragmatic, liver, and other body organs towards its tail to create a negative pressure.

Briefly explain the process of cellular respiration (include the following processes: glycolysis, the Krebs cycle and the electron transport chain (ETC) in your answer)!

Cellular respiration is the oxidative process that occur within cells. The 3 main stages of Cellular respiration are 1) Glycolysis 2) The krebs cycle and 3) electron transport chain (ETC) In this process, the cell seems to respire in a way that it takes in molecular oxygen (as an electron acceptor) and releases carbon dioxide (as an end product) Aerobic process, meaning: requiring oxygen to work 1) Role of Glycolysis in Cellular Respiration: First of the main metabolic pathways of cellular respiration to produce energy in the form of ATP. 2) Role of Krebs Cycle in Cellular Respiration: The second of the three stages of Cellular Respiration. glucose, fatty acids, and some amino acids are oxidized. The oxidation of these molecules is primarily used to transform the energy contained in these molecules into ATP. 3) Role of Electron Transport Chain (ETC) in Cellular Respiration: the 3rd Stage. Builds up a surplus of Hydrogen ions (protons) in the intermembrane space so that there will be a concentration gradient compared to the matrix of the mitochondria

Is there a connection between gas exchange and desiccation in insects? Explain!

Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. It is important that the gas exchange doesn't dry out, because oxygen must dissolve in water before it can diffuse into the cells. A limitation is that insects rely on diffusion to get oxygen to every cell. Insects don't have a circulatory system to carry oxygen around their bodies. Because the spiracles lead directly to the inside of the body and there are many of them, open spiracles would lead to the drying out of the insect. This is why spiracles can be closed

Describe the use of external surfaces (skin/epithelium) in gas exchange. Describe the actual process of gas exchange. Give several examples of animals that use this method. What is the crucial factor in terms of being able to use this type of gas exchange?

External features use diffusion for gas exchange. Gas Exchange: Oxygen and carbon dioxide move by diffusion across moist membranes. In simple animals, the exchange occurs directly with the environment. But with complex animals, such as mammals, the exchange occurs between the environment and the blood. Concentration of oxygen within the animal's cells is lower than concentration of oxygen outside the cells, so oxygen passes through the cell walls of the animal to maintain equilibrium. As the animal uses the oxygen, more of it diffuses through the skin. Protozoa, sponges, cnidarians, and worms all use direct diffusion. The crucial factor is greater surface area in relation to volume because the greater the surface area, the faster diffusion of gases can occur

Explain the concept of the counter-current system as applied to the process of gas exchange in fish gills.

Fish gills use 'countercurrent oxygen exchange' to maximize the amount of oxygen that their blood can pick up. They achieve this by maximizing the amount of time their blood is exposed to water that has a higher oxygen level, even as the blood takes on more oxygen. Countercurrent oxygen exchange means the blood flows through the gills in the opposite direction as the water flowing over the gills. This flow pattern ensures that as the blood progresses through the gills and gains oxygen from the water, it encounters increasingly fresh water with a higher oxygen concentration that is able to continuously offload oxygen into the blood. The low-oxygen blood, which is just entering the gill, meets low-oxygen water. Since there is more oxygen in the water, the oxygen can flow from water to blood. Likewise, the high-oxygen blood, which has nearly passed the entire length of the gill, meets fresh, high-oxygen water, and oxygen continues to flow from water to blood.

Explain the concept of gills in animals. Is there a connection between gills and the circulatory systems in animals?

Gill = the body part that helps an animal breathe underwater. Fish and some amphibians need to breathe the oxygen in water to live, and they use their gills for this. Gills are the main organs of respiration for animals that live underwater In animals that contain coelomic fluid instead of blood, oxygen diffuses across the gill surfaces into the coelomic fluid. Gills are found in mollusks, annelids, and crustaceans.

Describe the anatomy of gills in fishes (from macroscopic to microscopic levels). What are the main features of gills in a fish?

Gills come in different sizes and shapes Mouth: is a mouth. Acts as entrance for water. Gill bar: Structure that holds many gill filaments Gill Filaments: Where gas exchange takes place. Full of blood vessels Operculum cavity: Expands when mouth is closed in order to draw water over gills Operculum: Flap on outside of fish that covers whole gill structure. Works in conjunction with mouth to pump water over gills. Acts as an exit for the water. Gills in bony fish look similar to a car radiator. They are made of three parts: the filaments, the arches, and the rakers. The filaments are where the exchange of oxygen and carbon dioxide actually takes place. The arches provide structural support for the gills. The rakers are appendages that run along the inside edge of the arches, preventing food from passing through the gills. Most bony fish also have an operculum, a hard flap that covers the gills. The operculum allows the water pressure to be adjusted in the gills so the fish can breathe without forward movement. Cartilaginous aquatic animals have gill slits which open directly to the outside of the body. Each slit is separated by a gill arch.

What is the difference between positive and negative pressure breathing?

In negative pressure breathing, a vacuum is formed in the animal to drop pressure below atmospheric pressure, which cause air to rush into the respiratory system. In positive pressure breathing, air is forced into the lungs via pumping.

There are different forms of hemoglobin (e.g. fetal versus adult hemoglobin). Explain!

Hemoglobin A : makes up about 95%-98% of hemoglobin found in adults; it contains two alpha chains and two beta protein chains. Hemoglobin A2 : makes up about 2%-3% of hemoglobin found in adults; it has two alpha (α) and two delta (δ) protein chains Fetal hemoglobin has a higher affinity to oxygen than adult hemoglobin. This is because oxygen is given to the fetus and CO2 removed through blood from the mother. In order for the oxygen to diffuse into the fetus's blood stream, its hemoglobin needs to have a higher attraction to oxygen.

How is oxygen transported with in the blood? Describe the variety of proteins used in animals for this purpose!

Hemoglobin: The protein inside red blood cells that carries oxygen to cells and carbon dioxide to the lungs is hemoglobin Hemoglobin is made up of four symmetrical subunits and four heme groups. Each heme group can hold 4O2. Iron associated with the heme binds oxygen. It is the iron in hemoglobin that gives blood its red color. most animals use proteins called respiratory pigments to be able to carry more oxygen.

Hemoglobin is an amazing protein that has evolved to accommodate the process of gas exchange. Briefly explain some attributes of this protein that makes it such an excellent candidate for gas exchange in the human body.

Hemoglobin: a red, iron containing protein present in all vertebrates and many invertebrates. Each molecule of hemoglobin is 5% heme And 95% globin (a colorless protein) The heme portion has a great affinity for oxygen, each gram of hemoglobin can carry a maximum of approximately 1.3 ml of oxygen hemoglobin is sensitive to oxygen levels around it. In environments with a high partial pressure of oxygen, hemoglobin holds on to oxygen, at low concentrations it releases the oxygen. oxyhemoglobin's sensitivity to CO2 levels. Higher CO2 concentrations make hemoglobin have less affinity to its oxygen, so it unloads more oxygen in the presence of more CO2.

How does a bird lung differ from a mammalian lung? Briefly explain the process of gas exchange as it occurs in a bird lung.

In mammalian lungs, the exchange of oxygen and carbon dioxide occurs in microscopic sacs in the lungs, called 'alveoli.' The respiratory system of birds is more efficient than that of mammals, transferring more oxygen with each breath. This also means that toxins in the air are also transferred more efficiently. Birds have air sacs farther along the respiratory system that hold air. When birds breath in, some air goes into the lungs where oxygen diffuses. A lot of the air goes to the air sacs where it is stored until the bird exhales. When the bird exhales, air from the sacs which is still oxygen rich enters the long for more oxygen intake while old air is exhaled. This helps a bird have oxygenated air when it breathes in and out.

Discuss the different strategies of gas exchange in terms of internal and external surfaces. What kind of attributes do these surfaces need to have? Is there a connection with the type of habitat that the animal lives in? Explain!

Internal Gas Exchange: Internal respiration occurs in the metabolizing tissues, where oxygen diffuses out of the blood and carbon dioxide diffuses out of the cells. Internal Attributes: lungs, fish/mollusc gills, and the Tracheal systems of arthropods. These are mostly used by terrestrial animals. The reason terrestrial animals evolved internal structures is because they needed a way to keep their breathing structures moist. External Gas Exchange: External respiration occurs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses into the alveolar air. External Attributes: External structures include gills(dermal papillae for sea stars, some parapodia of polychaete worms) and the outer skin layer of an animal. This are mostly used by aquatic animals.

How does a lizard breathe? Does it strategy of breathing interfer with any other aspects of its life?

Lizards have lungs and a respiratory system to breathe. lizards breathe by flexing their body muscles Lizards breath in a unidirectional air path. The air goes into one of the bronchi and then instead of stopping at the alveoli continues through bronchioles and out of the lung. Lizards can't breathe while running.

What are the major types of gas exchange systems that have evolved in animals?

Lungs - In land animals Tracheal Systems - Used by insects Gills - Exchange gases in water environments

The term 'respiratory system' is typically used to refer to the system involved in providing gas exchange for the organism. What is the main physical process that is used for the actual movement of the two gases? Can the respiratory system handle this process alone in a larger organism?

Main Physical Process = Diffusion Diffusion: A way to get Oxygen in and Carbon Dioxide out. When blood returns to the lungs from the body, it has a lot of CO2 and no O2. By diffusion: The CO2 moves from the blood to the alveoli, where it can be exhaled through the lungs. The bigger the surface area = the faster diffusion of gasses can occur Want O2 into blood / CO2 out of blood as fast as possible, therefore we want a bigger surface area Larger organisms = cell increasing in size = volume increases faster than surface area, and when there is more volume and less surface area diffusion takes longer and is less effective Therefore, larger organisms cannot handle the process of diffusion alone

Give examples of several different types of animals with gills?

Mollusks, annelids, and crustaceans, sea stars

Do all animals have blood cells? Explain!

No, all animals do not have blood cells Animals that use diffusion don't have blood cells. some, not all, animals with circulatory systems don't need to have blood cells. For example, insects have their dedicated systems for gas flow through their tracheal systems

Are animals that use external surfaces for gas exchange restricted to that method? Give examples animals that combine several types of gas exchange.

No, they are not restricted Amphibians like frogs and turtles use only diffusion to breath in the winter when they hibernate even though they have lungs. Some lungless salamanders have larvae with gills, but as they mature they lose the gills

Do insects depend on their circulatory system to transport oxygen and carbon dioxide within their bodies? Explain!

No. The tracheoles lead directly to the cell so gas exchange is independent of circulatory system. Insects do not have lungs, nor do they transport oxygen through their circulatory systems. Instead, the insect respiratory system relies on a simple gas exchange system to bathe the insect's body in oxygen and to expel carbon dioxide waste.

What is the importance of accessing oxygen? What exactly is it used for? What happens if there is no oxygen available?

Oxygen = Survival Oxygen is needed to burn the fuels in cells to produce energy oxygen is brought into the lungs by breathing, where it is transported by red blood cells to the entire body where it is used to produce energy Aerobic Respiration would stop if there was no oxygen available, and organisms would die.

Why is gas exchange a necessity (from a cellular perspective)?

Oxygen acts as an electron acceptor in cellular respiration in order to create ATP. After accepting the electrons the oxygen also accepts hydrogen and forms water.

Explain the process of gas exchange as it occurs between the alveoli and the capillaries in a human lung.

Pulmonary ventilation provides air to the alveoli for gas exchange process. At the respiratory membrane, where the alveolar and capillary walls meet, gases move across the membranes, with oxygen entering the bloodstream and carbon dioxide exiting.

Some mammals are amazing divers (e.g. the Weddell Seal). How are these animals able to stay under water for more than an hour?

Reference link above Diving mammals will slow their heart rate, stop their breathing, and shunt blood flow from their extremities to the brain, heart, and muscles when starting a dive. champion divers, such as Weddell Seal, can hold their breath for about two hours. They rely on internal oxygen stores when they're down there. They have have positively charged oxygen-binding proteins, called myoglobin, in their muscles. This positive characteristic allows the animals to pack much more myoglobin into their bodies than other mammals, such as humans—and enables diving mammals to keep a larger store of oxygen on which to draw while underwater.

In what sense are diving spiders specialized in terms of their gas exchange?

Some diving spiders will spin a bell shaped web that they trap air under and surround themselves with. This lets them breathe underwater

How does the amount of oxygen vary between creeks/rivers versus stagnant water? Surface water versus water further down in the water column?

Stagnant water and deep water = less oxygen Moving and surface water = more oxygen Water at higher altitudes holds less oxygen. Fast-moving water generally has more oxygen than still water, because the movement mixes the air into the water. However, if the water is very turbulent, it may hold too much oxygen, causing stress to the aquatic organisms

Why does the surface area of the exchange surface be large as well as moist?

Surface area needs to be large to maximize the amount of oxygen that can diffuse into the bloodstream. Needs to be moist so that gases can diffuse through the membrane.

How is it possible that inhaled air will be clean, humid and warm as it reaches the alveoli of the lungs?

The Nose or Nasal Cavity. The Nasal airways are lined with cilia and kept moist by mucous secretions. The combination of cilia and mucous helps to filter out solid particles from the air an Warm and moisten the air, which prevents damage to the delicate tissues that form the Respiratory System.

Describe the process of gas exchange as it occurs between a developing human fetus and its mother.

The mother has oxygen in her blood. Her circulatory system comes into close contact with the fetus's and because the fetus's hemoglobin has a higher affinity to oxygen the oxygen diffuses out of the mother's system and into the fetuses. CO2 does the same, but out of the fetus and into the mother.

Describe the process of gas exchange in the tracheal system in the insects. How does the animal control the level of gas exchange?

There are holes on the outside of an insect called spiracles. The spiracles can be close to reduce water loss. The spiracles open to tracheae, which branch into many fluid filled tracheoles, which end really close to the plasma membrane of cells. This brings oxygen directly to cells. The way insects control how much air goes through them is by moving their body. this pushes old air out and can let new air enter.

Make a drawing of a human lung and label important parts in the upper as well as the lower respiratory tract. What are the functions of the different parts?

Upper Respiratory Tract: Nasal Cavity(lined with mucus, conditions air), Pharynx(tube which connects digestive and respiratory passages), Larynx(voice box) Lower Respiratory Tract: Trachea(diverts air to Bronchi), Bronchi(Directs air into each of the two lungs), Lungs(Consists of bronchioles, then alveoli where gas exchange occurs).

Where does the carbon dioxide originate from? Why does it need to be removed from the organism? What will occur if the carbon dioxide accumulates within the organism?

When food is burned for energy, the body makes Carbon dioxide as a waste product in the form of gas. Carbon dioxide must be removed from body to stop in from becoming toxic If CO2 accumulates within the organism then respiratory failures can occur and it can harm the body's organs