Module 3: Exchange and transport Flashcards
Do smaller organisms have a bigger or smaller SA:Vol than larger organisms?
Bigger
What is diffusion?
Net movement of particles down a concentration gradient from an area of higher concentration to an area of lower concentration.
Describe how single-celled organisms exchange substances with the environment
Substances can diffuse directly into or out of cell across cell surface membrane.
Why is diffusion quick in single-celled organisms?
short diffusion pathway and high SA:Vol
Give three reasons as to why diffusion across outer membrane is slow in multicellular organisms
Some cells deep within body - long diffusion pathway between cells and outside environment
Larger animals have low SA:Vol - difficult to exchange enough substances to supply a large volume of animal through a relatively small outer surface.
Higher metabolic rate - use up oxygen and glucose faster.
What three features improve efficiency of exchange surface?
Large SA
Thin - short diffusion pathway
Good blood supply and/or ventilation
Describe an example of how large SA increases efficiency of exchange surface.
Root hair cells
Cells on plant roots grow into long hair like structures which stuck out into soil.
Each branch of root is covered in millions of these root hair cells
Gives root large SA, helping to increase rate of absorption of water ( by osmosis) and mineral ions (by active transport) from the soil.
Why does being thin increase efficiency of exchange surface?
Decreased distance that substances being exchanged have to travel over.
Describe an example of how being thin increases efficiency of exchange surface.
Alveoli
Alveoli are gas exchange surface in the lungs.
Each alveolus is made from a single layer of flat, thin cells called alveolar epithelium.
Oxygen diffuses out of alveolar air space and into blood, CO2 diffuses in opposite direction.
Thin alveolar epithelium helps prover shorter diffusion pathway, increasing rate of diffusion.
Describe two examples of how good blood supply/ventilation helps increase efficiency of exchange surface.
Alveoli
Surrounded by large capillary network, giving each alveolus its own blood supply.
Blood constantly takes O2 away and brings CO2.
Lungs also well ventilated (you breathe in and out) so air in each alveolus is constantly replaced.
These features help maintain concentration gradients of O2 and CO2.
Gills
Gas exchange surface in fish
O2 and CO2 exchanged between fish’s blood and surrounding water
Contain large network of capillaries, keeping them well supplied with blood
Well ventilated as fresh water constantly passes over them
These features help maintain concentration gradient of O2, increasing rate at which O2 diffuses into blood.
What do cells need to exchange with the environment?
Take in things like Oxygen & glucose for aerobic respiration and other metabolic reactions and excrete waste products like carbon dioxide and urea.
What are the gas exchange organs in mammals?
Lungs
Describe the basic structure of gaseous exchange system
As you breathe in air enters trachea
Trachea splits into two bronchi - one bronchus leading to each lung
Each bronchus then branches off into smaller tubes called bronchioles.
Bronchioles end in alveoli - this is where gases are exchanged.
Why are there lots of alveoli in the lungs?
Provide larger surface area for diffusion
Name the 5 key cells and tissues found in gaseous exchange system
Goblet cells Cilia Elastic fibres Smooth muscle Cartilage
State where goblet cells are found and describe their function.
Trachea, bronchi, larger bronchiole
secrete mucus which traps microorganisms and dust particles in the inhaled air, stopping them from reaching the alveoli
State where cilia are found and describe their function
Trachea, bronchi, larger bronchiole, smaller bronchiole
Hair-like structures on surface of epithelial cells lining the airways.
Beat mucus secreted by goblet cells, moving it up away from alveoli and towards throat, where it’s swallowed.
Prevents lung infections
State where elastic fibres are found and describe their function.
Found in walls of trachea, bronchi, bronchioles, and alveoli.
Help process of breathing out
On breathing in, lungs inflate & elastic fibres are stretched.
Then, fibres recoil to help push air out when exhaling.
State where smooth muscle is found and describe its function
Trachea, bronchi, largest bronchiole, smaller bronchiole
Allows diameter to be controlled
During exercise smooth muscle relaxes, making tubes wider
Means less resistance to airflow and air can move in and out of lungs more easily
State where cartilage is kind and describe it’s function
Trachea in large C-shaped rings, bronchi in smaller pieces
Provide support
Strong but flexible - stops trachea and bronchi from collapsing when you breathe in and pressure drops
What is ventilation?
Ventilation consists of inspiration and exploration. It’s controlled by movements of diaphragm, intercostal muscles and ribcage.
Describe the process of inspiration.
External intercostal and diaphragm muscles contract
Causes rib cage to move up and out and diaphragm to flatten
This increases volume of thorax and therefore decreases lung pressure (to below atmospheric pressure)
Causes air to flow into lungs from area of higher pressure (atmospheric) to area of lower pressure (lung)
Active process - requires energy
Describe process of expiration.
External intercostal and diaphragm muscles relax
Ribcage moves down and in and diaphragm become curved again
Causes thorax volume to decrease and air pressure to increase
Air forced out of lungs
Normal expiration is passive process - doesn’t require energy
What happens during forced expiration?
Internal intercostal muscles contract, pulling rib cage down and in
