3.1 Exchange and Transport Flashcards
why do organisms need to exchange things with their environment
- need to take in things like oxygen and glucose for aerobic respiration and other metabolic activities
- need to excrete waste products from these reactions, such as CO2 and urea
- to every one of its cells
how do you calculate surface area to volume ratio
divide the surface area by the volume
as the size of an organism gets bigger, what happens to the SA:V ratio
it gets smaller
why do single-celled organisms not need exchange surfaces
- substances can diffuse directly in or out of the cell across the cell membrane, and they only have a small distance to travel
- they have a large SA:V ratio
- the metabolic activity is usually low, so O2 demands and CO2 production are low as well
why do bigger organisms need an exchange surface
- the rate of diffusion across the outer membrane is too slow:
1) some cells are very deep within the body, and there is a big distance between them and the outside environment
2) they have a lower (small) SA:V ratio, so difficult to exchange enough substances to supply the large volume through a relatively slow outer surface
3) they have a higher metabolic rate, so use up O2 and glucose, and excrete CO2 quicker
what is a main feature of mammalian and insect gas exchange systems
- need exchange of gases
- also need to reduce water loss
what are the adaptations of exchange surfaces to improve efficiency
- large surface area
- thin
- good blood supply
- ventilated well
explain increases surface area as an adaptation of an exchange surface
- provides area needed for exchange and overcomes the SA:V limitations of the organism, increasing rate
-e.g. root hair cells which grow into long hairs that stick out of the soil, with each branch covered in millions of these microscopic hairs - e.g. villi in small intestine
explain being thin as an exchange surface adaptation
- gives a short distance the substances have to travel to diffuse, so is fast and efficient (short diffusion pathway)
-e.g. the alveoli, where each air sac is made from a single, thin, flat layer of alveolar epithelium
explain having a good blood supply as an exchange surface adaptation
- steeper the concentration gradient, faster diffusion takes place
- good blood supply means substances are constantly delivered and removed from exchange surface, maintaining the steep gradient
explain ventilation as an exchange surface adaptation
- helps maintain concentration gradient and makes process efficient
explain how the alveoli and gills maintain a steep concentration gradient
alveoli:
- surrounded by large capillary network, so each alveolus has its own blood supply
- O2 always delivered, CO2 always removed
- also ventilated by breathing, so air is constantly replaced
gills:
- contain large network of capillaries, so well supplied with blood
- well ventilated, as fresh water constantly passes over them
explain the structure of the mammalian exchange system
- air enters via the trachea (windpipe) (via the larynx - voice box)
- trachea splits into 2 bronchi, each leading to each lung
- bronchus split off into smaller tubes called bronchioles
- bronchioles end in small air sacs called alveoli where gas is exchanged
- ribcage, intercostal muscles and diaphragm all work together to move air in and out, and pleural membrane surround lungs
what is the role of the nasal cavity
- large surface area and good blood supply, warming the air to body temperature
- hairy lining, secreting mucus and trapping bacteria
- moist surface, increasing humidity and reducing evaporation
- so air entering lungs is similar temp and humidity already
what are goblet cells
- in between and below ciliated epithelium cells
- secrete mucus
- trap microorganisms and dust particles in the inhaled air, stopping them from reaching the alveoli
what are cilia
- on the surface of the ciliated epithelium lining the bronchus
- beat the mucus
- move the mucus upward away from the alveoli towards the throat, where it is swallowed
- helps prevent lung infection
what and where are elastic fibres
- in the walls of the trachea, bronchus, bronchioles and alveoli
- help in the process of breathing out
- when breathing in, the lungs inflate and the elastic fibres are stretched
- then, the fibres recoil to help push the air out when exhaling
explain the role of smooth muscle
- walls of trachea, bronchi and bronchioles
- allow their diameter to be controlled
- during exercise, the smooth muscles relax, making the tube wider
- means less air resistance to airflow and air can move in and out of lungs more easily
explain the role of the rings of cartilage
- in the trachea and bronchus
- provide it support
- strong but flexible, stopping them from collapsing when you breath in and the pressure drops
- incomplete, so allows food to move easily to the oesophagus behind the trachea
what features does the trachea have
-large C shaped cartilage
- smooth muscle
- elastic fibres
- goblet cells
- ciliated epithelium
what features does the bronchi have
- smaller pieces of cartilage
- smooth muscle
- elastic fibres
- goblet cells
- ciliated epithelium
what features do the bronchioles have
- no cartilage
- smooth muscle, but not in smallest
- elastic fibres
- goblet cells in larger only
- ciliated, but not in smallest
what features do alveoli have
- no cartilage
- no smooth muscle
- elastic fibres
- no goblet cells
- no cilia
- MANY OF THEM
- also permeable and moist, to be able to carry dissolved gases through
what is lung surfactant
- cover inner wall of alveoli, along with water and salts
- makes it possible for alveoli to stay inflated
explain the process of inspiration
1) external intercostal and diaphragm muscles contract
2) causes the ribcage to move upwards and outwards, and the diaphragm to flatten
3) increases the volume in the thorax
4) causes the lung pressure to decrease below atmospheric pressure
5) causes air to flow into the lungs
-active process, requires energy
explain the process of expiration
1) external intercostal and diaphragm muscles relax
2) ribcage moves downwards and inwards, and the diaphragm becomes curved again
3) volume in the thorax decreases
4) air pressure increases above atmospheric pressure
5) air is forced out of the lungs
- normal expiration is a passive process
what happens during forced expiration
- internal intercostal muscles contract
- pulling the ribcage down and in
what is tidal volume
the volume of air in each breath, usually about 0.4dm^3
what is vital capacity
the maximum volume of of air that can be breathed in or out
what is breathing rate
how many breaths are taken, usually in a minute
what is oxygen consumption or oxygen uptake
the rate at which an organism uses up oxygen
- e.g. the number of dm^3 used per minute
which parts of a graph are what for gas in lungs and time
- from top of normal peak to bottom of normal = tidal volume
- from top of big peak to bottom = vital capacity
- big line up = big breath in
- big line down = big breath out
- the line never reaches 0 = residual air cant be expelled
what can a spirometer be used to measure
tidal volume, vital capacity, breathing rate, oxygen uptake
how does a spirometer work
- has an oxygen filled chamber with a moveable lid
- person breathes through a tube connected to the oxygen chamber
- as the person moves, the lid of the chamber moves up and down
- these movements can be recorded by a pen attached to the lid of the chamber
- this writes on a rotating drum, creating a spirometer trace
- OR can also be connected to a motion sensor, which will use movements to produce electronic signals, which are picked up by a data logger
- the soda lime in the tube the subject breathes into absorbs the carbon dioxide
why does the total volume of gas in the spirometer chamber decrease over time
- air that’s breathed out is a mixture of CO2 and O2
- the CO2 is absorbed by the soda lime (including the CO2 released via respirartion)
- so there’s only oxygen in the tube that the subject inhales from
- as the oxygen gets used up by respiration, the total volume decreases
how can you work out breathing rate from a spirometer
- count the amount of peaks in the first minute
- if less than a minute, multiply
- unit is breaths per minute
how can you work out tidal volume from a spirometer
- difference between peak and trough of one wave, may change
how do you work out vital capacity from a spirometer
measure the biggest wave
how do you work out oxygen consumption from a spirometer
- the decrease in volume in the chamber
- read by taking the average slope of the trace
- difference between highest and lowest peak
why do fish need specialised gas exchange
- water is denser than air
- water is more viscous than air
- water has a lower concentration of oxygen than the air
explain how the structure of the gills makes them efficient for gas exchange
- water containing oxygen enters the fish through the mouth and passes out through the gills
- each gill is made from lots of tiny branches called gill filaments/primary lamellae, giving them a big surface area for gas exchange
- the gill filaments are covered in lots of tiny structures called gill plates or secondary lamellae, increasing the surface area even more
- each gill is supported by a gill arch
- the gill plates have lots of blood capillaries and a thin surface layer of cells to speed up diffusion
- overlapping of gill filaments increases resistance to water flow and slows it down, more time for gas exchange to take place
what do some more primitive forms of fish use to ventilate their gills
ram ventilation- continually move in water to pass it over the gills
explain how counter current flow helps with fish gas exchange
- blood flows through the gill plates in one direction and water flows over in the opposite direction
- called the counter-current system
- maintains a large concentration gradient between the water and the blood
- the concentration of oxygen in the water is always higher than in the blood, so as much oxygen as possible diffuses from the water into the blood
- across the whole length of the gill
how do the gills in bony fish stay ventilated
1) fish opens its mouth which lowers the floor of the buccal cavity ( the space inside the mouth)
2) the volume of the buccal cavity increases, decreasing the pressure inside the cavity
3) water in sucked into the cavity
4) when the fish closes its mouth, the floor of the buccal cavity is raised again
5) volume inside decreases, pressure increases and water is forced out of the cavity across the gill filaments
6) each gill is covered by a bony flap called the operculum (which protects the gill)
7) increase in pressure causes the operculum on each side of the head to open, allowing water to leave the gills
(in some fish, the operculum bulges out, increasing the volume of the cavity behind the operculum, just after the buccal cavity lowers. this contributes to the decrease in pressure that causes the water to increase the fishes mouth)
PAG: how do you dissect a fish
1) wear apron/lab coat and gloves, as can be messy
2) place the fish on a dissection tray or on a cutting board
3) push back the operculum and use scissors to carefully remove the gills
4) cut each gill arch through the bone at the top and bottom
5) if looked closely, should be able to see gill filaments (can put in water for better view)
6) finish off by drawing and labelling
what is the insect gas exchange surface
microscopic air-filled pipes called tracheae
explain the insect gas exchange system - tracheae
- air moves into the tracheae through pores on the insects surface called spiracles
- oxygen travels down the conc. gradient towards the cells
- CO2 from the cells moves down its own conc. gradient towards the spiracles to be released into the atmosphere
what do the tracheae branch off into and what are they filled with
- smaller tracheoles which have thin, permeable walls and go to individual cells
- also contain fluid, which oxygen can dissolve into
- oxygen then dissolves from this fluid into body cells (CO2 is opposite)
explain rhythmic abdominal movements in insects
- used to change the volume of their bodies
- move air in and out of the spiracles due to changing pressures
- when insects are flying, they use their wing movements to pump their thoraxes too
- increases the amount of O2 entering
how can you dissect an insect
- you need a relatively big one, thats been killed humanely fairly recently
1) fix the insect to a dissecting board, putting dissecting pins through its legs to hold it in place
2) to examine the trachea, carefully cut and remove a piece of exoskeleton (insects hard outer shell) from along the length of its abdomen
3) use a syringe to fill the abdomen with saline solution
4) should be able to see a network of very thin, silvery grey tubes - tracheae (silver as filled with air)
5) can examine under light microscope using a wet mount
6) should be able to see rings of chitin in the walls of the trachea - there for support, like cartilage in humans
explain how the bell jar model would be used to show the breathing
- lungs are the balloons
- glass rods are the trachea and bronchi
- jar is the chest cavity
- rubber sheet is the diaphragm
- as the rubber sheet is pulled down the volume of the jar increases, the pressure therefore decreases and air is drawn in through the glass tube inflating the balloons, which represent the lungs
