A Level Biology - Chapter 3 A

small organism

small organism

high SA : V

large organism

low SA : V

single-celled organism

fast diffusion rate, substances diffuse directly into cell across membrane

multicellular organism

slow diffusion rate, large distance between cells and external environment, low SA : V, specialised exchange organs and mass transport system

heat exchange, body size

large V low SA hard to lose heat, low V large SA easily lose heat needs high metabolic rate to stay warm

heat exchange, body shape

compact shape (mouse) low SA reduce heat loss, complex shape (elephant) large SA easy heat loss

gas exchange surface

a boundary between the outside environment and the internal environment of an organism

gas exchange surface properties

large SA, thin

gill filaments

increase surface are

lamellae

increase surface area, lots of blood capillaries close to surface

counter current system

blood and water flow in opposite directions over the gills, maintains high concentration gradient, high rate of diffusion of oxygen

dicotyledonous plants

mesophyll cells large SA, stomata open and close to control substances

insects

air movement - spiracles - tracheae, move down concentration gradient - tracheoles, thin permeable walls, oxygen diffuses directly into respiring cells

controlling water loss - xerophytes

sunken stomata reduce concentration gradient, hairs trap water vapour, curled leaves protect from wind, reduced stomata, thick waxy cuticle reduce evaporation

gas exchange system structure

trachea - bronchi - lung - bronchioles - alveoli

ventilation

the process of inspiration and expiration controlled by movements of the diaphragm, internal / external intercostal muscles and ribcage

inspiration

external intercostal muscles and diaphragm contract, internal intercostal muscles relax, ribcage moves up and out, thoracic cavity volume increase, lung pressure decrease, air moves down pressure gradient into lungs

expiration

internal intercostal muscles contract, external intercostal muscles and diaphragm relax, ribcage moves down and in, thoracic cavity volume decrease, lung pressure increase, air moves down pressure gradient out of lungs

phospholipid surfactant

decrease surface tension preventing alveoli collapsing

alveoli adaptations

thin one cell thick, millions large SA, capillaries one cell thick, concentration gradient - increase rate of diffusion; elastin - recoil to normal shape

tidal volume

the volume of air in each breath

ventilation rate

the number of breaths per minute

forced expiratory volume (FEV)

the maximum volume of air that can be treated out in 1 second

forced vital capacity (FVC)

the maximum volume of air it’s possible to breathe forcefully out if the lungs after a really deep breath in

tuberculosis

bacteria, immune system builds wall around bacteria in lungs forming tubercles, infected tissue dies, reduces tidal volume

tuberculosis symptoms

persistent cough, coughing up blood and mucus, chest pains, shortness of breath, fatigue

fibrosis

formation of scar tissue in the lungs, thicker and less elastic, reduces tidal volume and rate of gas exchange, faster ventilation rate to get enough oxygen

fibrosis symptoms

shortness of breath, dry cough, chest pain, fatigue, weakness

asthma

bronchiole smooth muscle contract, secrete a lot of mucus, constriction of airways, air flow/FEV reduced

asthma symptoms

wheezing, tight chest, shortness of breath

emphysema

foreign particles/smoke trapped in alveoli, inflammation, attracts phagocytes, alveoli walls and elastin break down, no recoil, surface area decreased, rate of gas exchange decreased

emphysema symptoms

shortness of breath, wheezing