3.1.1 - EXCHANGE AND TRANSPORT Flashcards
Why do organisms need to exchange substances with their environment?
- Cells need to take in things (e.g. oxygen and glucose for aerobic respiration)
- They need to excrete waste products from such reactions (e.g. carbon dioxide and urea)
What would have a larger SA:V ratio, a mouse or a hippo?
The mouse would have a higher SA:V ratio
How to calculate SA:V ratio?
SA ÷ V
Why do multicellular organisms need exchange surfaces?
An organism needs to supply every one of its cells with substances like glucose + oxygen (for respiration), but also needs to remove waste products to avoid damage
Why is the diffusion rate slower for multicellular organisms than unicellular organisms?
- In unicellular organisms, these substances can diffuse quickly into (or out of) the cell across the cell surface membrane (the distance is small)
- However in multicellular organisms, some cells are deep within the body (big difference between them and outside world), larger animals have a low SA:V ratio (difficult to exchange substances or supply a large volume of animal through a small outer surface, multicellular organisms have a higher metabolic rate than unicellular organisms (use of oxygen and glucose faster)
How are root hair cells adapted for transport?
They grow long ‘hairs’ which stick out into the soil, increasing their surface area
How are alveoli adapted for transport?
- Each alveolus is made from a single layer of thin, flat cells called the alveolar epithelium —> this decreases the distance over which oxygen and carbon dioxide diffusion takes place
- Alveoli are surrounded by large capillary network (each alveolus has its down blood supply) + lungs are ventilated —> maintains concentration gradients of oxygen and carbon dioxide
How are fish gills adapted for transport?
- They contain a large networks of capillaries for a good blood supply
- They are also well ventilated (due to fresh water constantly passing over them
These features help maintain a concentration gradient of oxygen
Name four substances an organism needs to exchange with its environment
- Oxygen
- Glucose
- Carbon dioxide
- Urea
Name the components/organs in the human respiratory system
- Trachea
- Bronchi (singular Bronchus)
- Bronchioles
- Alveoli
- Ribcage
- Intercostal muscles (internal + external)
- Diaphragm
What is the function of goblet cells in the mammalian gas exchange system?
- Lines the airways
- Secret mucus, trapping organisms and dust particles in the inhaled air, stopping them for reaching the alveoli
What is the function of cilia in the mammalian gas exchange system?
- On the surface of cells lining the airways
- Cilia beat the mucus, moving it upward away from the alveoli towards the throat, where it’s swallowed
Prevents lung infection
What is the function of elastic fibres in the mammalian gas exchange system?
- Present on the walls of the trachea, bronchi, bronchioles and alveoli to help the process of breathing out
- On breathing in, ht lungs inflate and the elastic fibres are stretched
- Then, fibres recoil to help push the air out when relaxing
What is the function of smooth muscle in the mammalian gas exchange system?
- Present in the walls of the trachea, bronchi and bronchioles and allows their diameter to be controlled
- During exercise, the smooth muscles relaxes, making the tubes wider
^— means there’s less resistance to airflow + air can move in and out of the lungs more easily
What is the function of rings of cartilage in the mammalian gas exchange system?
- Lines the walls of the trachea and bronchi to provide support
- it’s strong but flexible - stops the trachea and bronchi collapsing when you breathe in + the pressure drops
Describe the structure of the trachea in the mammalian gas exchange system
Cartilage - large C-shaped pieces
Smooth Muscle
Elastic fibres
Goblet cells
Ciliated epithelium
Describe the structure of the bronchi in the mammalian gas exchange system
Cartilage - smaller pieces
Smooth muscle
Elastic fibres
Goblet cells
Ciliated epithelium
Describe the structure of the larger bronchioles in the mammalian gas exchange system
NO cartilage
Smooth muscle
Elastic fibres
Goblet cells
Ciliated epithelium
Describe the structure of the smaller bronchioles in the mammalian gas exchange system
NO cartilage
Smooth muscle
Elastic fibres
NO goblet cells
Ciliated epithelium
Describe the structure of the smallest bronchioles in the mammalian gas exchange system
NO cartilage
NO smooth muscle
Elastic fibres
NO goblet cells
NO ciliated epithelium
Describe the structure of the alveoli in the mammalian gas exchange system
NO cartilage
NO smooth muscle
Elastic fibres
NO goblet cells
NO ciliated epithelium
Describe the process of inspiration in the mammalian gas exchange system
- Breathing in
- External intercostal and diaphragm muscles contract
- Ribcage moves upwards and outwards + diaphragm flattens (increasing volume of the thorax)
- As thorax volume increase, lung pressure decreases
- Causes air to flow into lungs
INSPIRATION IS AN ACTIVE PROCESS - REQUIRES ENERGY
Describe the process of expiration in the mammalian gas exchange system
- Breathing out
- External intercostal and diaphragm muscles relax
- Ribcage moves downward and inwards + diaphragm becomes curved again (relaxes)
- Thorax volume decreases, causing the air pressure to increase
- Air is forced out of the lungs
NORMAL EXPIRATION IS A PASSIVE PROCESS - DOESN’T REQUIRE ENERGY
EXPIRATION CAN BE FORCED THOUGH (e.g. blowing out candles on birthday cake)
^— when forced, internal intercostal muscles contract, to pull the Ribcage down and in
What is meant by tidal volume?
The volume of air in each breath (usually about 0.4 dm³)
What is meant by vital capacity?
The maximum volume of air that can be breathed in or out
What is meant by breathing rate?
How many breath are taken - usually in a minute
What is meant by oxygen consumption/uptake?
The rate at which an organism uses up oxygen (e.g. the number of dm³ used up per minute)
What is a spirometer?
A machine that can give readings of tidal volume, vital capacity, breathing rate and oxygen uptake
Describe how a spirometer can be used
- A spirometer is an oxygen-filled chamber with a movable lid
- The person breathes through a tube connected to the oxygen chamber
- As the person breathes in and out, 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 the spirometer can be hooked up to a motion sensor - this will use the movements to produce electronic signals, which are picked up by a data logger
- The soda lime in the tube the subject breathes into absorbs carbon dioxide
How are fish specially adapted to get enough oxygen from the water?
- Water, containing oxygen, enters the fish through its mouth + passes out through the gills
- Each gill is made of a lot of thin branches called gill filaments (primary lamellae), which give a big surface area for exchange of gases | The gill filaments are covered in lots of tiny structures called gill plates (secondary lamellae), which increase surface area. Each gill supported by a gill arch
- Gill plates have lots of blood capillaries and a thin surface layer of cells to speed up diffusion
- Blood flows through the gill plates in one direction + water flows over in the opposite direction (counter current system) | Maintains a large conc. gradient between the water and the blood - the conc. of oxygen in water is always higher than blood (so as much oxygen as possible diffuses from the after into the blood)
Describe how fish gills are ventilated
- The fish opens its mouth, which lowers the floor of the buccal cavity space inside the mouth) | Volume of buccal cavity increases, decreasing pressure in the cavity - water then sucked into cavity
- When fish closes its mouth, the floor of the buccal cavity is raised again | The volume inside the cavity decreases, the pressure increases, and water is forced out of the cavity across the gill filaments
- Each gill is covered by the operculum | The increase in pressure forces the operculum on each side of the head to opens, allowing water to leave the gills
What is the operculum?
The bony flap on each side of the fish’s head, covering and protecting the gills
Describe how insects exchange gases
- Insects have microscopic air-filled pipes called tracheae which they use for gas exchange
- Air moves into the tracheae through pores on the insect’s surface called spiracles
- Oxygen travels down the conc. gradient towards the cells | Carbon dioxide from the cells moves down its own concentration gradient towards the spiracles to be released into the atmosphere
- The tracheae branch off into smaller tracheoles which have thin, permeable walls and go to individual cells | The tracheoles also contain fluid, which oxygen dissolves in
- The oxygen then diffuses from this fluid into body cells | Carbon dioxide diffuses into the opposite direction
- Insects use rhythmic abdominal movements to change the volume of their bodies and move air in and out of the spiracles | When larger insects are flying, they use their wing movements to pump their thoraxes too
Name the structures on an insect’s surface that allow air to enter the tracheae
Spiracles
Describe the structure on an insect’s tracheoles
Tracheoles come of tracheae branches and are single elongated cells which run between tissues
No chitin - so are permeable and allow for easier gaseous exchange
What is the function of the rings of chitin surrounding the tracheae?
They are impermeable (so there is no gas exchange in the tracheae) and provide structure for the tracheae
