BIO 2A03 LEC 18-20 EXAM QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026

BIO 2A03 LEC 18-20 EXAM QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026 What is unique about the climbing perch fish? - Answers It has a unique respiratory system that allows it to survive on land for up to 6 days Why is oxygen important? - Answers So mitochondria can make ATP (mitochondrial respiration) What does respiratory systems do? - Answers facilitate transport of oxygen and co2 to and from exchange areas What is external respiration? - Answers Gas exchange movement from environment into the cells that need it What is internal respiration? - Answers Cellular respiration and getting oxygen into mitochondria and conversion into ATP Steps of external respiration? - Answers 1. Ventilation 2. Diffusion across respiratory surface 3. Circulation 4. Tissue diffusion (Perfusion in tissues) 5. Cellular utilization or production What is simple diffusion vs. bulk flow? - Answers Simple: SA:V ratio is large so oxygen diffuses through skin Bulk Flow: SA:V ratio is small so we need internal organs What does the diffusion rate depend on? - Answers Diffusion coefficient (higher in the air than water) Cross sectional area (gills/lungs) Partial pressure gradient Diffusion distance What are Fick's laws? - Answers 1. solute moves from high concentration to low (from lungs to blood) 2. the amount of substance that diffuses across a surface is proportional to SA and inverse to distance it diffused SA:V ratio determines what? - Answers If large ratio- simple diffusion works well (flat worm) If small ratio- specialized structures to improve oxygen uptake How do aquatic animals breathe? - Answers Through evaginations or outpockets of body surface allowing for water exchange How do land animals breathe? - Answers Invaginations with special respiratory structures What direction does water flow? - Answers Countercurrent, where water flows in one direction across the gills and blood flows in the opposite direction What are the cavities that water flows through? - Answers Water flows through buccal cavity and it closes and opercular cavity expands to bring in water Exchange happens into cells and lammalae Why is countercurrent flow more efficient? - Answers 100% ox water interacts with 90% ox blood this allows for diffusion gradient to be substantial at all points Respiration on land uses what type of breathing? - Answers Spiracular How do insects breathe? - Answers Through tracheal systems called spiracular breathing Actual insect breathing mechanisms? - Answers Trachea end go all the way to skin called spiracles (Tracheloes are very thin about 0.2um diameter so short diffusion distance) What are spiracles lined with? - Answers smooth muscle to control water loss and keep dust out Bird breathing mechanisms? - Answers They have rigid and in expansible lungs. Lungs and air sacs expand and contract with thoracic cavity. In depth bird breathing mechanisms? - Answers Expansion of chest causes air to go to bronchi then to posterior air sacs then to lungs then to anterior air sacs then second exhalation pushes stale air from anterior air sacs out through trachea Ventilation has how many cycles? - Answers 2; inhalation and exhalation What are parabronchi? - Answers Structures in birds where gas exchange occurs called cross current (capillary bed is perpendicular to airflow) What should respiration systems do? - Answers Ventilation, exchange surface for diffusion/perfusion, difference in partial pressure and surface area What are the 2 zones in mammalian respiration? - Answers Conducting zone (no gas exchange between blood and air) Respiratory zone (gas exchange occurs here) What is the function of cartilage rings in mammals? - Answers allow for the trachea to expand and contract and protects these areas. What structures are used in the conducting zone? - Answers Primary, secondary and tertiary bronchi which is reinforced with cartilage and smooth muscle so it can constrict and dilate to change the amount of air What structures are used in the respiratory zone? - Answers Terminal bronchioles and alveoli (site of exchange) with little cartilege or smooth muscle to ensure efficient exchange How many alveoli do we have? - Answers 20 million or 100m^2 of surface area What are the 3 laws of pulmonary ventilation? - Answers Daltons Law: Total pressure is the sum of all the partial pressures of a gaseous mixture (oxygen is just a part of atmospheric pressure) Boyles Law: Gases move from areas of high pressure to areas of low pressure. (pressure is inverse to volume of the container) Henrys Law: Concentration of a gas in liquid is proportional to solubility and partial pressure of that gas Does our chest expand before or after air comes in? - Answers Our chest expands first and then air comes in (it is dependent on the difference in pressure between the atmosphere and our lungs What are the three types of pressure? - Answers Atmospheric (760 mmHg, oxygen is only 150 of this) Intra-alveolar (intrapulmonary pressure): pressure inside the lung/ alveoli which changes during phases of breathing Intrapleural: the pressure of air within the pleural cavity (between the visceral and parietal pleurae) - Lower than or negative to intra-alveolar pressure and ensures lungs stay closely connected to thoracic wall - Serous membrane which is connective tissues to connect it to viceral and parietal membranes What are the lungs surrounded by? - Answers A pleural sac which consists of 2 pleural sheets and fluid in the interpleural space (which lubricates pleura and allows for the layers to slide past eachother during ventilation) What is the level of interpleural pressure? - Answers It is sub-atmospheric at rest because chest wall pulls on parietal pleura (touches lungs) and elasticity of lungs pulls on visceral pleura (touches muscle) Negative pressure holds it all together (at minus 4) Is inhalation an active or resting process? - Answers Active, it uses muscles Which muscles does inhalation involve? - Answers External intercostal muscles contract, pulling ribs up and out Diaphragm contracts, moving down so lung volume increases, thoracic volume increases and negative pressure so air flows in Is exhalation active or resting process? - Answers Both, resting/passive at rest where the elastic recoil of thoracic and lung volume decrease and positive pressure causes exhalation. Active during intense breathing exercise! Muscles used in active exhalation? - Answers Internal intercostal muscles contract, pulling ribs in and down. Abdominal muscles contract pushing the diaphragm up which allows for air to flow out faster What is tidal ventilation? - Answers When air comes in and out the same way (not unidirectional) Coordinated in brain where CPGs in the medulla excite the contractions in diagraphm and intercostal muscles (autonomic process) What happens when we do not have Acetylcholine? - Answers Muscles cannot relax so suffocation occurs (with serin gas) What is perfusion? - Answers Movements of air into blood through pulmonary capillaries Ventilatory surface: lungs (bronchioles to alveoli) Counter-current exchange: oxygen poor capillaries to alveoulus Which cells do respiratory alveolar membranes contain? - Answers - Type 1 epithelial cells: line sac and contact air (1 cell thick) - Type 2 surfactant cells (reduce surface tension so air sacs do not collapse on themselves) important for lung compliance and reducing surface tension - Macrophages: help with immune surveillance - Blood rich supply to respiratory zone What is Ficks law? - Answers D * SA * (delta P / X) What is the partial pressure of oxygen - Answers alveloar partial pressure - blood partial pressure What is the partial pressure of carbon dioxide? - Answers blood partial pressure - alveolar partial pressure What is the mitochondria partial pressure? - Answers minimum for it to support ATP synthesis which is 1 mm Hg (which is a large buffer) How is hemoglobin effective? - Answers It delivers 0.2 mL oxygen per 1 mL of blood whereas if oxygen just dissolved in blood it would be 0.3 mL per 100 mL (it has low solubility in water and plasma) What is the structure of hemoglobin? - Answers tetrameric respiratory protein, composed of 4 oxygen binding subunits (2 alpha and 2 beta chains and 4 hemes ) How is Hb modulated? - Answers Allosterically where binding on one site affects binding at other sites When oxygen binds hemoglobin what does it create? - Answers An oxyhemoglobin which is 98% saturated with oxygen If we have low tissue PO2 what happens? - Answers O2 is released and deoxyhemoglobin is formed How much on average does hemoglobin offload? - Answers 25% of oxygen, leaving 75% remaining What does the oxygen equilibrium curve show? - Answers Percent saturation of hemoglobin and how it relates to partial pressure of oxygen What is the P50 value? - Answers the measure of oxygen affinity of a respiratory pigment when the pigment is 50% saturated What curve shape does hemoglobin have? - Answers sigmoidal shape which comes from salt bridges (allosteric modifier for oxygen binding) Where one gives and one takes What curve shape does myoglobin have? - Answers hyperbolic because myoglobin is monomeric. Each myoglobin binds one oxygen molecule independantly of other myoglobin molecules What are conditions that affect hemoglobin? - Answers PH: decrease causes curve to shift right (lactic acid causes pH to decrease eg. Bohr Shift) CO2: increase causes shift right Temperature: increase shifts right Organic Phosphate: negative allosteric modifiers of O2 binding (2-3, DPG) which an increase causes shift right What do fetal mammals use? - Answers A different hemoglobin molecule where they have 2 alpha and 2 gamma chains (instead of beta) Which increases affinity What are the 3 ways that CO2 is transported? - Answers 10% is dissolved in plasma and RBC cytoplasm 30% is bound to hemoglobin to form carbaminohemoglobin 60% is transported as bicarbonate (HCO3), mainly dissolved in plasma and happens through carbonic anhydrase which catalyzes the formation of HCO3 What is the most abundant protein in RBC? - Answers Hb and then HCO3 What is the Bohr shift? - Answers a rightward shift of the oxygen dissociation curve due to increase pH or CO2 What goes hand in hand with CO2 increase? - Answers high pH What is the PP of CO2 at rest? - Answers 46 mm HG What is the Haldane effect? - Answers The lower the PO2 and hemoglobin saturation with O2, the more CO2 can be carried in the blood. As blood passes through pulmonary capillaries: - Answers Increased PO2 and decrease PCO2 Oxygen curve shifts left to load O2 and unload CO2 As blood passes through systemic capillaries: - Answers Decreased PO2 = increased PCO2 and H+ Oxygen equilibrium curve shifts right which accentuates O2 unloading and CO2 loading How is breathing regulated? - Answers Sensory receptors and CPG Which receptors do we have? - Answers Central chemoreceptors: located in ventrolateral surface of medulla and respond to PCO2 and pH changes of CSP Peripheral chemoreceptors: located in carotid and aortic arteries (cell detect changes is pressure of O and CO2) What do carotid and aortic arterial chemoreceptors do? - Answers If low blood PO2 occurs, potassium channels close and cell depolarizes, calcium enters and signals to the medulla to increase respiration (only if below 60 mmHG)