Topic 3A - Exchange and transport systems DVY * Flashcards
size and surface area Gas exchange Gas exchange in humans the effects of lung disease interpreting lung disease data dissecting gas exchange systems
why do organisms need exchange surfaces?
cells need to take in oxygen (for aerobic respiration) and nutrients
they need to excrete waste products like CO2 and urea
most organisms need to stay at roughly the same temperature, so heat needs to be exchanged too
how does surface area to volume ratio change with the size of an organism?
the smaller an organism, the greater its surface area to volume ratio
how does exchange work in single-celled organisms?
substances can diffuse directly into (or out of) the cell across the cell-surface membrane. the diffusion rate is quick because of the small distance substances have to travel
why can’t multicellular animals do substance exchange like single-celled organisms?
diffusion across the outer membrane is too slow
how is diffusion across the outer membrane too slow in animals?
some cells are deep within the body
larger animals have a low surface area to volume ratio
what problem does cells deep within the body cause for substance exchange?
big distance between them and outside environment
what problem does low surface area to volume ratio cause for substance exchange?
its difficult to exchange enough substances to supply a large volume of animal through a relatively small outer surface
how have multicellular organisms adapted for substance exchange?
flattened shape so cells are all closer to surface
specialised exchange organs and an efficient system to carry substances to and from their individual cells (mass transport)
what does mass transport refer to in mammals?
it normally refers to the circulatory system, which uses blood to carry glucose and oxygen around the body. it also carries hormones, antibodies and waste like CO2
what does mass transport involve in plants?
the transport of water and solutes in the xylem and phloem
how does body size affect heat exchange?
the rate of heat loss from an organism depends on its surface area. small animals have comparatively large surface areas, this makes it easy to lose heat from its body, so they need a relatively high metabolic rate, in order to generate enough heat to stay warm
how does body shape affect heat exchange?
compact shape = small surface area : volume - minimising heat loss from surface
less compact = large SA:vol - increases heat loss from surface
body shape depends on the temperature of its environment
what’s an example of an animals environmental temperature affecting its body shape?
Arctic fox: 0C - small ears, round head to reduce SA:vol
African bat-eared fox: 25C - large ears, pointed nose to increase SA:vol
European fox: 12*C - intermediate between 2 matching temperature of its environment
what other adaptations do organisms have when their body size or shape doesn’t fit their climate?
kidney structure adaptations so they produce less urine to compensate for water loss through high SA:vol
eating high energy foods to support high metabolic rates in cold regions
thick layers of fur to hibernate in cold weather
large organisms in hot climate increase SA with large flat ears or staying in water
what determines how much of a substance an organism needs?
size
exchange surfaces
metabolic rates
transport systems
what features do specialised exchange surfaces have?
large SA:vol to increase rate of exchange
very thin - to reduce diffusion distance
selectively permeable - allow selected materials to cross
movement of environmental medium to maintain diffusion gradient
transport system - internal medium is moved to maintain diffusion gradient
what is Fick’s law?
rate of diffusion ∝ surface area x concentration difference / thickness of membrane
what major features do gas exchange systems have to have?
large surface area
they’re thin
maintain a steep concentration gradient
why don’t single-celled organisms need gas exchange systems?
they absorb and release gases by diffusion through their outer surface.
they have a large SA, they’re thin so have short diffusion pathway and gases can take part in biochemical reactions as soon as they enter the cell
how do fish get oxygen from the water?
water enters fish through mouth and passes through gills
how are gills adapted for efficient gas exchange?
large surface area
the lamellae have lots of blood capillaries
thin surface layer of cells to speed up diffusion
counter-current blood flow
how do gills have a high surface area?
each gill is made of lots of thin plates called gill filaments
the gill filaments are covered in lots of tiny structures called lamellae
this increases surface area
what is counter-current blood flow?
blood flows through lamellae in 1 direction and water flows in the other.
the concentration of oxygen in the water is always higher than in the blood, so as much oxygen as possible diffuses into the blood
how does gas exchange occur in insects?
tracheal system
what is the tracheal system?
air enters tracheae through spiracles
tracheae branch into smaller tracheoles with thin permeable walls and go to individual cells
insect use rhythmic abdominal movements to move air in and out of the spiracles
ventilation also replaces air in tracheae
what are spiracles?
pores on the surface of insects that connect to the tracheae
how does gas exchange occur in the tracheal system?
oxygen travels down its concentration gradient towards the cells, and diffuses directly into respiring cells from the tracheoles.
CO2 from the cells moves down its own concentration gradient towards the spiracles to be released into the atmosphere
why do leaves need gas exchange?
they need CO2 for photosynthesis which produces oxygen
they need oxygen for respiration which produces CO2
they can’t be completely self-sufficient because they can’t photosynthesise at night
what is the main gas exchange surface in leaves?
the surface of the mesophyll cells, they’re well adapted because they have a large surface area
how do gases reach the mesophyll tissues inside the leaf?
gases move in and out through special pores in the epidermis called stomata
guard cells can open the stomata to allow exchange of gases, and close them to prevent water loss
how do insects reduce water loss without reducing gas exchange too much?
they can close their spiracles using muscles
waterproof waxy cuticle all over their body
tiny hairs around their spiracles which reduce evaporation
small SA:vol
how do plants reduce water loss without reducing gas exchange too much?
can close stomata
waxy upper layer to prevent water loss through evaporation
stomata on shaded underside of leaf
xerophytic adaptations
how do plants open and close their stomata?
kept open during day to allow gaseous exchange.
water entering guard cells makes them turgid, which opens stomatal pore
if plant starts getting dehydrated guard cells lose water and become flaccid, closing pore
what are xerophytes?
plants that are specially adapted for life in warm, dry or windy habitats, where water loss is a problem
what are some examples of xerophytic adaptations?
sunken stomata hairs around stomata curled leaves reduced number of stomata waxy, waterproof cuticles on leaves and stems small leaf surface area extensive roots
how do sunken stomata reduce water loss in leaves?
stomata sunk in pits trap moist air, reducing the concentration gradient of water between the leaf and the air. this reduces the amount of water diffusing out of the leaf and evaporating away
how do hairs surrounding the stomata reduce water loss in leaves?
a layer of hairs on the epidermis traps moist air around the stomata, reducing the concentration gradient of water between the leaf and the air.
how do curled leaves reduce water loss in leaves?
curled leaves with the stomata inside protect them from wind, (windy conditions increase the rate of diffusion and evaporation)
how does a reduced number of stomata reduce water loss in leaves?
there are fewer places for water to escape
why do insects need gas exchange systems?
they are highly active so need efficient gas exchange
but they can’t have thin permeable surfaces over a large area because they also need to conserve water.
this means they need a gas exchange system
what are the trachea in insects made up of?
chitin rings, which prevent the tubes from collapsing
how is the concentration gradient of oxygen in the tracheal system maintained?
cells are respiring and using up oxygen
oxygen concentration near cells is low
where oxygen enters spiracles, oxygen concentration is high
how is the concentration gradient of carbon dioxide in the tracheal system maintained?
cells are respiring and producing CO2
CO2 concentration near cells is high
CO2 concentration near spiracles is low
what happens in abdominal pumping?
insects have muscles which squeeze the trachea enabling mass transportation of gases in and out
during contraction = expulsion of air
during expansion = inspiration of air
why do fish need specialised gas exhange sysytems?
they have a waterproof, gas tight outer covering
small SA:vol
where are gills located?
behind the head of the fish
how many gills do bony fish have?
most bony fish have 5 pairs of gills
how much oxygen can gills absorb from the water?
about 80% of the oxygen available in the water is absorbed into the fish’s blood
how can fish still absorb oxygen when they’re not moving?
bony fish ventilate their gills using muscular contractions which causes water to move through the mouth over the gills and out of the open opercula valves
why is concurrent flow less effective than counter-current flow?
when a fish’s blood flows in the same direction as water, the oxygen concentration in both decreases alongside the other, this means only 50% of the oxygen available can be absorbed
what are the main features of a leaf?
waxy cuticle upper epidermis palisade mesophyll spongy mesophyll xylem phloem lower epidermis guard cells stomata
examples of plants with a thick waxy cuticle?
holly
examples of plants with a small leaf surface area?
conifer needles
cactus spines
examples of plants with sunken stomata?
marram grass
cacti
examples of plants with stomatal hairs?
marram grass
couch grass
examples of plants with rolled leaves?
marram grass
examples of plants with extensive roots?
cacti
how do extensive roots reduce water loss in leaves?
maximise water uptake from soil
why do humans breathe?
humans need to get oxygen into the blood for respiration and get rid of carbon dioxide
what does the gas exchange system consist of in humans?
air enters trachea
trachea splits into 2 bronchi
each bronchus branches into smaller bronchioles
bronchioles end in smaller air sacs called alveoli
what does ventilation consist of?
inspiration and expiration
its controlled by the movements of the diaphragm, internal and external intercostal muscles and ribcage
what happens in inspiration?
external intercostal muscles and diaphragm muscles contract
ribcage moves upwards and outwards, diaphragm moves down (flattens)
volume of thoracic cavity increases
lung pressure decreases
air flows down pressure gradient into lungs
requires energy
what happens in expiration?
external intercostal and diaphragm muscles relax
ribcage moves down and in
diaphragm curves up
volume of thoracic cavity decreases
air pressure in lungs increases
air forced down pressure gradient out of the lungs
passive- doesn’t require energy
what happens during forced expiration?
external intercostal muscles relax, internal intercostal muscles contract, pulling the ribcage further down and in.
the movement of the 2 sets of intercostal muscles are said to be agnostic (opposing)
what is each alveolus made from?
alveolar epithelium - a single layer of thin, flat cells
how are the alveoli structured?
huge number of alveoli, so big surface area
surrounded by a network of capillaries
how does gas exchange occur at the alveoli?
O2 diffuses out of alveoli, across the alveolar epithelium and the capillary endothelium and into haemoglobin in the blood
CO2 diffuses into the alveoli from the blood, and is breathed out
how does oxygen move in the respiratory system?
oxygen from air moves down trachea, bronchi and bronchioles into alveoli
down pressure gradient
oxygen diffuses across alveolar epithelium, then the capillary endothelium into the capillary down diffusion gradient
how are alveoli adapted for efficient gas exchange?
thin exchange surface large surface area steep concentration gradient capillaries in close contact RBC slow down to fit through capillary
how do alveoli have thin exchange surfaces?
the alveolar epithelium is only 1 cell thick, this means there’s a short diffusion pathway
how do alveoli have a large surface area?
a large number of alveoli means there’s a large surface area for gas exchange
how do alveoli have a steep concentration gradient?
steep concentration gradient of oxygen and carbon dioxide between the alveoli and capillaries constantly maintained by the flow of blood and ventilation
why do mammals have lungs?
large, with a large number of cells
need lots of oxygen absorbed for respiration and lots of CO2 removed
high metabolic rate to maintain body temperature
why do we need to remove CO2 from our bodies?
it is toxic
what do we do to keep oxygen and CO2 levels constant?
alter our breathing depth and rate according to our level of activity
what are the lungs?
a pair of lobed structures found in the thoracic cavity protected by the ribs
what is the trachea?
tube leading from the throat to the lungs. made of muscle and help open by c-shaped rings of cartilage.
lined with goblet and ciliated epithelial cells to trap dirt and microbes
what are the bronchi?
2 divisions of the trachea, one leading to each lung. narrower than trachea but still contain cartilage to protect cilia and mucus
what do goblet cells do?
produce mucus
what are the bronchioles?
many smaller branches from the 2 bronchi. no cartilage. made of smooth muscle so can contract and relax and adjust diameter
what are the ribs?
protect and support the lungs. during ventilation the intercostal muscles between the ribs contract and relax
what is the diaphragm?
thick sheet of muscle between the lungs that separate the thorax from the abdomen. contract and relaxes and controls ventilation of the lungs along with movement of the ribs
what are the alveoli?
tiny air sacs at the end of each bronchiole. lined with thin epithelial cells with rich blood supply. have elastic properties and contain collagen
what is the composition of gases in inhaled air?
N2 - 78% O2 - 21% CO2 - 0.04% H2O - <1% other - <1%
what is the composition of gases in exhaled air?
N2 - 78% O2 - 15% CO2 - 4% H2O - 3% other - <1%
what is pulmonary ventilation?
this calculates the total volume of air that is moved into the lungs during 1 minute
what does lung disease affect?
ventilation and gas exchange in the lungs
what is the tidal volume?
the volume of air in each breath - usually between 0.4 dm^3 and 0.5 dm^3 for adults
what is ventilation rate?
the number of breaths per minute. for a healthy person its about 15
what is forced expiratory volume?
the maximum amount of volume of air that can be breathed out in 1 second
what is forced vital capacity?
the maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath in
how can you find a persons tidal volume, ventilation rate and other measures of breathing?
from a spirometer
what are 2 examples of different lung diseases?
pulmonary tuberculosis
fibrosis
asthma
emphysema
what happens when someone gets tuberculosis?
when infected with tuberculosis bacteria, immune system cells build a wall around the bacteria in the lungs, forming small hard lumps called tubercles
how does pulmonary TB reduce tidal volume?
infected tissue inside tubercles dies and gaseous exchange surface is damaged
tuberculosis can cause fibrosis which further reduces tidal volume
what affect does a reduced tidal volume have?
less air can be inhaled with each breath. in order to take in enough oxygen, patients have to breathe faster. ventilation rate increased
what are symptoms of pulmonary tuberculosis?
persistent cough, coughing up blood and mucus, chest pains, shortness of breath and fatigue
what is fibrosis?
the formation of scar tissue in the lungs, from infection or exposure to substances like asbestos or dust
how does fibrosis lead to reduced tidal volume?
scar tissue is thicker and less elastic than normal lung tissue.
lungs are less able to expand, so can’t hold as much air.
tidal volume is reduced and so is FVC
how does fibrosis reduce gas exchange?
diffusion is slower across thicker scarred membrane
what are symptoms of fibrosis?
shortness of breath, a dry cough, chest pain, fatigue and weakness
faster ventilation rate - to get enough air into lungs to oxygenate blood
what is asthma?
a respiratory condition where the airways become inflamed and irritated
what causes asthma?
usually allergic reactions to substances like pollen and dust
what happens during an asthma attack?
the smooth muscle lining the bronchioles contracts and a large amount of mucus is produced
how does asthma reduce the forced expiratory volume?
asthma attack causes constriction of the airways, making it difficult to breathe properly. air flow in and out of lungs is severely reduced, so less oxygen enters alveoli and moves into the blood
what are symptoms of asthma?
wheezing, a tight chest and shortness of breath. symptoms come on very suddenly during an attack
how can asthma symptoms be relieved?
they can be relieved by drugs, often in inhalers, which cause the muscle in the bronchioles to relax, opening up the airways
what causes emphysema?
smoking or long-term exposure to air pollution - foreign particles in the smoke or air become trapped in the alveoli
how is damage caused in emphysema?
foreign particles cause inflammation, which attracts phagocytes to the area and produce an enzyme that breaks down elastin
what is elastin?
a protein in the walls of the alveoli thats elastic and helps them return to their normal shape after inhaling and exhaling air
what does a loss of elastin in the alveoli mean?
the alveoli can’t recoil to expel air as well (it remains trapped in alveoli)
destruction of alveoli walls, which reduces the surface area, so rate of gaseous exchange decreases
what are the symptoms of emphysema?
shortness of breath and wheezing.
increased ventilation rate as they try to increase the amount of air reaching their lungs
in general what negative effects does lung disease have?
reduced rate of gas exchange in alveoli.
less oxygen able to diffuse into bloodstream body’s cells receive less oxygen and rate of aerobic respiration is reduced
less energy is released and sufferers often feel tired and weak
what are risk factors?
factors that increase a person’s chance of getting that disease
what is a correlation?
a link between 2 things, it doesn’t always mean that one thing causes the other
what may you be asked to do about data given to you in exams?
describe the data - e.g. there is a decrease in people who smoke between 1990 and 2012
draw conclusions - e.g. correlation between num of smokers and morality rate, but not necessarily caused by it there may be other reasons for the trend
consider other points - more people may have cancer but more are surviving
How did the Government respond to scientific data for lung cancer?
in 1950s and 60s medical studies found link between smoking and cancers.
this caused UK government making deal with tobacco companies to put written and then picture health warnings on adverts and products
what response did the government have to evidence linking asthma and pollution?
EU adopted national emissions ceilings directive. setting upper limits on total emissions for 4 major pollutants in atmosphere.
clean power for transport package also introduced, taxing car owners according to cars emissions
what equipment is needed for a lung dissection?
lab coat
scalpels and dissecting scissors - all clean, sharp and free from rust
cutting board
why do dissecting tool have to be sharp?
blunt tools don’t cut well and can be dangerous
how to inflate the lungs in a dissection?
attach a piece of rubber tubing to the trachea and pump air into the lungs using foot or bicycle pump, they will deflate by themselves because of the elastin in the walls of the alveoli
what precautions must be taken when inflating the lungs in a dissection?
down blow down tube to inflate lungs - stale air from the lungs may be inhaled
put lungs in clear plastic bag before inflating - to stop bacteria from lungs being released into the room
how to cut open the trachea in a lung dissection?
cut lengthways, down the gap in the c-shaped rings of cartilage, using dissecting scissors or scalpel
if using scalpel, cut downwards, away from you and don’t apply to much pressure on the blade.
cut down 1 bronchi and see bronchioles
what is involved in a lung dissection?
inflating the lungs
examine different tissue types
open up trachea and bronchi
cut off a piece of the lung
why does lung tissue feel spongy?
air trapped in all the alveoli
what to do after lung dissection?
wash your hands and disinfect work surfaces
lungs could contain bacteria that cause food poisoning
how to dissect fish?
wear lab coat
place fish in dissection tray or on cutting board
push back operculum and use scissors to carefully remove gills
cut each gill arch through the bone at the top and bottom
if you look closely you can see the gill filaments
how are gills protected?
by a bony flap called the operculum and are supported by gill arches
what insect is needed for an insect dissection?
a big insect e.g. grasshopper or cockroach thats been humanely killed fairly recently
how to carry out an insect dissection?
fix insect to dissecting board using dissecting pins
remove section of exoskeleton
use syringe to fill abdomen with saline solution, a network of thin, silvery-grey tubes should be seen - these are the tracheae, the look silver because they’re filled with air
tracheae can be observed under an optical microscope using a temporary mount slide, rings of chitin can be seen in the walls of the tracheae for suport
how to remove section of exoskeleton?
carefully cut and remove a piece of the exoskeleton from along the length of the insects abdomen
what are the ethical issues involved in dissecting animals?
morally wrong to kill animals just for dissections, its unnecessary killing
animals raised in an inhumane way
what is the argument against dissections being unnecessary killing?
many dissections are carried out on animals that have already been killed for their meat
how might animals not be raised in a humane way?
they may be subject to overcrowding, extremes of temperature or lack of food - they may not be killed humanely either
what must be done if animals are raised in schools for dissection?
make sure they are looked after properly and killed humanely to minimise any suffering or distress
how to calculate pulmonary ventilation?
tidal volume x ventilation rate
units of tidal volume?
dm^3
units of ventilation rate?
breaths per minute
min^-1
units for pulmonary ventilation?
dm^3/min
how are the results of a spirometer displayed?
on a kymograph
what is the residual volume?
the volume left over from volume of air forcefully inhaled after forceful expiration (usually 2.5 dm^3) its to make sure the alveoli don’t close up
what are the risk factors for lung disease?
smoking - 90% of COPD sufferers are or have been heavy smokers
air pollution
genetic make-up
infections
occupation - e.g. people working with harmful chemicals, gases and dusts
