Life's Transport, Exchange, and Defense Systems

Life's Transport, Exchange, and Defense Systems

• How do gas exchange systems facilitate the exchange of gases between organisms’ cells and the environment?
• A flatworm's respiration process functions via diffusion across the outer membrane.
• A common carp, like many aquatic creatures, utilizes gills to extract oxygen from the water.
• As water passes over the gills, oxygen is transferred to the blood via veins.
• Insects respire using a tracheal system.
• Air enters the respiratory system through the nasal cavity and pharynx.
• Air continues through the trachea and enters the bronchi, which bring air into the lungs.
• The trachea and bronchi consist of incomplete cartilage rings.
• The trachea bifurcates into the right and left bronchi in the lungs.
• The right lung contains three lobes and is larger
• The left lung is smaller with two lobes to accommodate the heart.
• Terminal bronchioles connect with respiratory bronchioles, which connect to alveolar ducts and alveolar sacs.
• Each alveolar sac has 20–30 spherical alveoli and looks like a bunch of grapes.
• Air flows into the alveolar sac's atrium then circulates into alveoli, where gas exchanges with the capillaries.
• Mucous glands secrete mucous to keep airways moist and flexible.

Gas Pressure and Respiration

• Air comprises gases: nitrogen (N2; 78.6%), oxygen (O2; 20.9%), water vapor (H2O; 0.5%), carbon dioxide (CO2; 0.04%).
• A gas's partial pressure is calculated by P = (Patm) x (percent content in mixture).
• Patm = PN2 + PO2 + PH2O + PCO2 = 760 mm Hg
• PO2 = (760 mm Hg) (0.21) = 160 mm Hg
• PCO2 = (760 mm Hg) (0.0004) = 0.3 mm Hg
• At high altitudes, Patm decreases but concentration does not change; the partial pressure decrease is due to the reduction in Patm.
• When air reaches the lung, it is humidified.
• Water pressure (47 mm Hg) is subtracted from atmospheric pressure: 760 mm Hg - 47 mm Hg = 713 mm Hg
• The partial pressure of oxygen is: (760 mm Hg - 47 mm Hg) × 0.21 = 150 mm Hg.

Respiration

• Respiration consists of 4 distinct processes: pulmonary ventilation, external respiration, transport and Internal respiration.
• Pulmonary Ventilation consists of air moving into and out of the lungs.
• External Respiration is when oxygen diffuses into the blood and carbon dioxide diffuses into the alveolar air

Respiration Processes

• Transport moves oxygen and carbon dioxide between the lungs and tissues through the blood
• Internal Respiration is diffusion of gases between the blood of the systemic capillaries and cells.
• Inhalation involves air being taken into the lungs by creating negative pressure.
• Negative pressure is created by respiratory muscles and diaphragm contraction; also called inspiration/active process.
• Active processes causes pressure to be less than the environment.
• Active processes increase the volume of the thoracic cavity and size of the lungs as oxygen enters the lungs.
• Exhalation involves air being drawn out of the lungs by respiratory muscles relaxation.
• Air being drawn out is also called expiration, and constitutes a passive process with greater pressure than the environment.
• A passive process decreases the thoracic cavity and the lungs as carbon dioxide exits.
• The ratio of carbon dioxide production to oxygen consumption is the respiratory quotient (RQ).
• RQ varies between 0.7 and 1.0.
• RQ equals one if just glucose is used to fuel the body.
• One mole of carbon dioxide is produced for every mole of oxygen consumed.
• Alveolar PO2 = inspired PO2 – (alveolar PCO2/RQ)
• An RQ of 0.8 with a PCO2 in the alveoli of 40 mm Hg, makes the alveolar PO2 equal to: alveolar PO2 = 150 mm Hg - (40 mm Hg/0.8 ) = mm Hg.
• Notice that this pressure is less than the external air, prompting the oxygen to flow from the inspired air in the lung (PO2 = 150 mm Hg) into the bloodstream (PO2 = 100 mm Hg).
• The partial pressures of oxygen and carbon dioxide change as blood moves through the body.

Hemoglobin

• Hemoglobin is a protein inside of red blood cells that carries oxygen to cells and carbon dioxide to the lungs.
• Hemoglobin is made of four symmetrical subunits and four heme groups.
• Iron associated with heme binds oxygen.
• The oxygen dissociation curve shows that increasing partial pressure of oxygen leads to more oxygen binding to hemoglobin.
• Hemoglobin's affinity for oxygen may shift left or right based on environmental conditions.
• Carbon dioxide levels, blood pH, and body temperature affect oxygen-carrying capacity
• CO2 + H2O --> H2CO3 --> HСОЗ- + H+
• Increase in CO2 levels decreases pH which decreases Hb-O2 affinity
• Carbon dioxide is transported in the blood via dissolution directly into the blood, carried as a bicarbonate ion and binding to hemoglobin
• 5-7% of carbon dioxide is dissolved in the plasma, because carbon dioxide is more soluble in blood than is oxygen.
• 10% of carbon dioxide binds to hemoglobin to form carbaminohemoglobin, which is reversible
• Majority (85%) is carried as part of the bicarbonate buffer system
• Bicarbonate buffer system uses the actions of Carbonic anhydrase (CA) CO2 + H2O <--> H2CO3 <--> HCO3- + H+
• Hemoglobin binds to free H+ ions and thus limits shifts in pH.
• Chloride shift: newly synthesized bicarbonate ion is transported out of the red blood cell into the liquid component of the blood in exchange for a chloride ion (Cl-)

Carbon Dioxide Flow

• When the blood reaches the lungs, the bicarbonate ion is transported back into the red blood cell in exchange for the chloride ion.
• H+ ion dissociates from the hemoglobin and binds to the bicarbonate ion.
• This produces the carbonic acid intermediate, which is converted back into carbon dioxide through the enzymatic action of CA.
• The carbon dioxide produced is expelled through the lungs during exhalation via : CO2 + H2O <--> H2CO3 <--> HCO3- + H+

Gas Exchange in Plants

• Plants facilitates gas exchange using stomata, lenticels and root hairs
• Lenticels are loosely packed mass of cells in bark of woody plant, visible on a stem surface as a raised powdery spot,
• Root hairs are long tubular-shaped outgrowths from root epidermal cells
• In closed circulatory systems, the heart pumps blood through vessels separated from the body's interstitial fluid.
• Most vertebrates and some invertebrates like the annelid earthworm, have closed circulatory systems.
  • In open circulatory systems, fluid called hemolymph is pumped through a blood vessel that empties into the body cavity.
• Hemolymph returns to the blood vessel through openings called ostia.
  • Arthropods, like the bee and most mollusks, have open circulatory systems.
• Simple animals consisting of a single cell layer such as a sponge, or only a few cell layers, like the jellyfish, do not have a circulatory system.
• Instead, gases, nutrients, and wastes are exchanged by diffusion.

Vertebrate Circulatory Systems

• Fish have the simplest circulatory systems: blood flows unidirectionally from the two-chambered heart through the gills and then the rest of the body.
• Amphibians have two circulatory routes: one for oxygenation of the blood through the lungs and skin, and the other to take oxygen to the rest of the body.
  • The blood is pumped from a three-chambered heart with two atria and a single ventricle.
• Reptiles also have two circulatory routes; blood is oxygenated through the lungs.
  • The heart is three-chambered, but the ventricles are partially separated so some mixing of oxygenated and deoxygenated blood occurs except in crocodilians and birds.
• Mammals and birds have the efficient heart with four chambers that completely separate oxygenated and deoxygenated blood; it pumps only oxygenated blood through the body and deoxygenated blood to the lungs.
• The mammalian circulatory system is divided into three circuits: the systemic circuit, the pulmonary circuit, and the coronary circuit.
• Blood is pumped from veins of the systemic circuit into the right atrium of the heart, then into the right ventricle.
• Blood then enters the pulmonary circuit and is oxygenated by the lungs.
• From the pulmonary circuit, blood re-enters the heart through the left atrium.
• From the left ventricle, blood re-enters the systemic circuit through the aorta and is distributed to the rest of the body.
• The coronary circuit, which provides blood to the heart, is not shown.
• Red blood cells deliver oxygen to cells and remove carbon dioxide.
• Hemoglobin delivers oxygen to the body and removes some carbon dioxide.
  • Hemoglobin comprises four protein subunits, two alpha chains and two beta chains, and a heme group with iron. - Iron reversibly associates with oxygen, and is oxidized from Fe2+ to Fe3+.
• In most mollusks and some arthropods, hemocyanin delivers oxygen, is not carried in blood cells, and the copper binds oxygen, giving the hemolymph a blue-green color.
• Annelids or earthworms, hemerythrin carries oxygen, is carried in blood cells, has iron, but lacks heme.

Immune System

• Granulocytes, including neutrophils, eosinophils and basophils, are characterized by a lobed nucleus and granular inclusions in the cytoplasm
• Granulocytes are typically first-responders during injury or infection.
  • Agranulocytes include lymphocytes and monocytes.
• Lymphocytes, including B and T cells, are responsible for adaptive immune response.
• Monocytes differentiate into macrophages and dendritic cells, which in turn respond to infection or injury.
• Platelets form from megakaryocytes and are required for clotting the blood.
  • Platelets collect at a wound site in conjunction with other clotting factors, such as fibrinogen, to form a fibrin clot that prevents blood loss and allows the wound to heal.

Blood Vessels and Blood Pressure

• arteries conduct blood from the heart to the other organs Precapillary sphincters regulate blood flow through capillaries, they help control the location of blood flow to where it is needed
• Valves in veins prevent blood from moving backward.
• Varicose veins are veins that become enlarged because the valves no longer close properly, allowing blood to flow backward, often prominent in the legs.
• Fluid from capillaries moves into the interstitial space and lymph capillaries by diffusion down a pressure gradient and osmosis.
  • Out of 7,200 liters of fluid pumped by the average heart in one day, over 1,500 liters are filtered.
• Blood pressure comes form the fluid's(blood) hydrostatic pressure against blood vessel walls.
• • Fluid moves from areas of high to low hydrostatic pressures
• Arteries hydrostatic pressure is very high near the heart and blood flows to the arterioles .
• Atterioles narrow openings slow rate of flow.
• During systole, the artery walls stretch to accommodate the increased blood pressure.
• During diastole the walls return to normal because of their elastic properties.
• The blood continues to empty into the arterioles at a relatively even rate throughout the cardiac cycle.
• Peripheral resistance is the resistance to blood flow.
• Blood pressure is related to the blood velocity in the arteries and arterioles.
• Capillaries and veins experience a decrease but the velocity increases

Cardiac Output

• Cardiac output (CO) is the volume of blood pumped by the heart per minute: CO = HR x SV
  • HR = heart rate
  • SV = stroke volume (volume of blood pumped into the aorta per contraction of the left ventricle)
• Cardiac output can be increased by increasing heart rate.
• Cardiac output can be increased by increasing stroke volume.
  • Stroke volume can be increased by speeding blood circulation through the body so that more blood enters the heart between contractions.
• During heavy exertion, blood vessels relax and increase in diameter to increase oxygenated blood flow to the muscles.
• Stress reduces the diameter of blood vessels,increasing blood pressure

Plant Transport

• The cohesion-tension theory of sap ascent says that transpiration draws water from the leaf.
• This evaporation from the mesophyll cells produces a negative water potential gradient that causes water to move from the roots up through xylem..
• Phloem consists of cells call sieves-tube elements
• Phloem transports phloem sap through perforations call sieve plate tubes
• Neighbouring companion cells carry out metabolic functions for sieve-tube elements.
• Lateral sieve areas connect the sieve-tube elements to the companion cells.
• Sucrose is actively transported from source cells into neighboring companion cells and then into the sieve-tube elements
• This process reduces water potential to allow water to enter the pholem from the xylem
• The resulting pressure forces the sucrose water mixture toward the roots where sucrose is unloaded
• Transpiration causes water to return to the leaves through the xylem vessels

Immunity

• Barriers as physical defense
  • Intact epidermis, dermis, and mucous membranes
  • Mucus trapping and cilia sweeping of pathogens
  • Tears washing pathogens away
  • Resident normal flora competing with pathogens
• Also chemical barriers as defense
  • Sebum and perspiration acidity inhibit bacteria
  • Lysozyme in perspiration, tears, saliva is antibacterial
  • Gastric juice acidity destroys swallowed pathogens.
• Mast cells dilate blood vessels and induce inflammation through release of histamines and heparin & recruit macrophages and neutrophils.
  • Macrophages are phagocytic cells that ingest foreign pathogens and cancer cells which stimulates immune cell response.
• Natural killer cells kills tumor cells and virus-infected cells.
• Dendritic cells present antigens on their surfaces, and trigger adaptive immunity migrating to lymph nodes upon activation.
• Monocytes differentiate into macrophages and dendritic cells in response to inflammation.
• Neutrophils are first responders that release toxins and recruit other immune cells.
• Basophils are responsible for defense against parasites which release histamines that cause inflammation and allergic reactions.
• Eosinophils release toxins against bacteria and parasites, and may cause tissue damage.
• Interferons are cytokines released by cells infected with a virus to destroying neighboring RNA and reduce protein synthesis.
• Mast cells secrete histamines that cause nearby capillaries to dilate in response to a cut.
  • Neutrophils and monocytes leaving capillaries develop into macrophages & release chemicals to stimulate inflammatory response.

Immune System Pathways and Cells

• Antigen-antibody complex involves C1 binding to antigen-antibody classic pathway has C1 that binds to an antigen-antibody
• Antigen-antibody complex causes complement components C2 and C4 to split in two with fragments forming an enzyme call C3 convertase.
• Alternate pathway C3 convertase splits into C3 by C3 convertase which splits C3 in two, and endogenous proteins protects host cells from lysis.
• Natïve CD4+ T cells engage MHC II molecules on antigen-presenting cells (APCs), creating clones in activated helper T cells, which activate B cells and CD8+ T cells where cytotoxic T cells kill infected cells.
• Memory cells results from a B cell internalizing an antigen and presenting it on MHC II and a helper T cell recognizes the MHC II-antigen complex and activates the B cell
• Lymphatic vessels carry lymph a clear fluid that moves thru the body
• The liquid enters lymph nodes through afterent vessels that contain lymphocytes that damage infecting walls.
• The spleen is like the lymph more but is larger which filters blood instread of lymph; containing red pulp, whie pulp and a capsule.
• The B cell region has an antigen binding site that enables the cell to bind to antigen.
• Immunoglobins exists as lgA IgG IgE lgM and lgD

Antibodies

• Antibodies have the effect of neutralization, opsonization, and complement activation.
• Neutralixation involves antibodies that prevent the binding of a vurs or toxic protein from binding
• Opsonization involves a pathogen being tagged to consumed by macrophagel or neutrophil
• Complemen activation involves antibodies attached to the surface of a pthogen activiting the system
• Autoimmune disease: is where the body's immune systems attack the body’s own cells rather than foreign pathogens