Exchange Surfaces Verified Solutions 2023/2024

EXCHANGE SURFACES VERIFIED SOLUTIONS 2023/2024 Why do multicellular organisms need specialised exchange surfaces but single celled organisms don't? - ANSWER single celled organisms can exchange materials across their CSM to meet requirements - metabolic activity low → O2 needs low + CO2 produced is low - large SA:V ratio Multicellular organisms are the opposite - high metabolic rate (active + maintain temp) - small SA:V ratio 3 main features of an efficient exchange surface - ANSWER • increased surface area • thin layer • good blood supply/ventilation to maintain gradient how to calculate surface area to volume ration using a sphere - ANSWER - calculate SA with 4π² - calculate volume with 4/3πr³ - ratio = surface area/volume can see as radius gets bigger the SA:V ration decreases How does increased SA aid diffusion? - ANSWER larger SA:V ratio bigger area for exchange e.g root hair cells, villi How do thin layers aid diffusion? - ANSWER reduces diffusion distance e.g in alveoli How does a good blood supply aid diffusion? - ANSWER Increases concentration gradient substances constantly delivered and removed e.g alveoli, gills, villi Nasal cavity features - ANSWER - large SA with good blood supply - goblet cells secrete mucus to trap dust + bacteria - moist surface so gases dissolve helping them to pass across the gas exchange surface trachea structure - ANSWER - supported by incomplete rings of strong flexible cartilage - lined with ciliated epithelium which uses synchronised movement to move bacteria out of lungs to throat - also lined with goblet cells which produce mucus to trap bacteria - smooth muscle and elastic fibres Bronchiole structure - ANSWER - smooth muscle - contracts to constrict airways to control air flow - elastic fibres - ciliated epithelium - goblet cells CORRECT FROM DR REYNOLDS EMAIL REPLY alveoli structure - ANSWER - layer of thin flattened epithelial cells → short diffusion pathway - elastin + collagen → stretch and recoil - large surface area - surrounded by capillaries → good blood supply - covered in surfactant which speeds up transport of gases + reduces the surface tension of fluid in alveoli - good ventilation what happens in the alveoli? - ANSWER main gas exchange surfaces what is the purpose of cartilage in the trachea? - ANSWER prevents it collapsing on itself diagrams comparing bronchiole and trachea - ANSWER describe route taken by air as it is inhaled - ANSWER - through the mouth - down trachea - into bronchi - into bronchioles - alveoli What is ventilation? - ANSWER movement of air into and out of the lungs what happens during inspiration? - ANSWER - diaphragm contracts, flattens + lowers - external intercostal muscles contract so rib cage moves upwards and outwards - volume of thorax increases so pressure in thorax decreased - pressure in thorax lower than than atmospheric pressure so air is drawn into lungs what happens during expiration? - ANSWER - diaphragm relaxes, moves up into dome shape - external intercostal muscles relax so rib cage moves downwards and inwards - volume of thorax decreases so pres