Gas Exchange, Digestion & Mass Transport (SR) Flashcards
(50 cards)
How can single celled organisms exchange Oxygen and Carbon Dioxide?
Directly through Plasma Membrane via Diffusion
How do Insects exchange gas?
In their Tracheal system:
1) Air enters via spiracles
2) Travels through trachea and tracheoles
3) Delivering Oxygen directly to every tissue
How does gas exchange occur in fish?
Via Gills:
1) Orientation of Gill filaments and Lamellae ensures water flowing over them moves in opposite direction to flow of blood through capillaries (counter-current system)
2) Maintaining a diffusion gradient
Where does gas exchange occur in Dicotyledonous plants? How does it occur?
1) Occurs in the leaves
2) Stomata open to allow gases to diffuse in and out
Mesophyll cells have large SA for rapid diffusion
What can gas exchange lead to and how is this controlled?
1) Gas Exchange can lead to water loss
2) Plants control opening of Stomata to limit this
How do Xerophytes control water loss?
Additional Adaptations, such as: Hairs Waxy Cuticle Small Leaves Sunken Stomata Rolled Leaves
How can Insects control water loss?
By controlling the opening and closing of Spiracles
Having Hair around Spiracles and by
Having a Waterproof, Waxy Cuticle
Where does Gas Exchange occur in Humans?
In the lungs
How is the Alveolar Epithelium adapted to gas exchange?
Having a large Surface Area
Good Blood Supply
Thin Walls & Elastic Fibres which help recoil
What is Ventilation?
The process of breathing in (inspiration) and breathing out (expiration)
What occurs in Inspiration?
External Intercostal Muscles (ICM) contract (Internal ICM relax)
Rib Cage moves up & out
Diaphragm contracts
Volume of Thorax increases
Atmospheric Pressure > pulmonary pressure - forcing air into the lungs
What occurs in Expiration?
Internal Intercostal Muscles (ICM) contract (external ICM relax)
Ribs move down and inwards
Diaphragm relaxes
Volume of Thorax Decreases
Pulmonary Pressure > Atmospheric Pressure - forcing air out of the lungs
What is the Pulmonary Ventilation Rate?
Total volume of air moved into the lungs in a minute
What is the Tidal Volume?
Volume of Air moved in and out of the lungs with a normal breath
What is the Breathing Rate?
Number of Breaths per minute
What is the Pulmonary Ventilation Rate Equation?
Pulmonary Ventilation Rate (dm3 min-1) = Tidal Volume (dm3) x Breathing Rate (min-1)
How does increasing the size of an organism affect the Surface Area : Volume Ratio (SA:V)?
Greater the size of an organism, the smaller its SA:V
Larger organisms ∴ require specialised exchange surfaces and transport mechanisms to meet metabolic requirements
What do Specialised Exchange Surfaces have?
1) A Large Surface Area
2) Thin Barriers
3) Associated Transport Systems to maintain steep diffusion gradient
Why do Organisms with a higher metabolic rate require a specialised exchange surface?
Because they require more nutrients and produce more waste than Organisms with a lower metabolic rate
What do Red Blood Cells (RBCs) have to transport Oxygen?
The Protein Haemoglobin (Hb)
What is Haemoglobin (Hb) made up of?
Made up of 4 Polypeptide chains, each containing a prosthetic Haem group.
Each Haem group binds to one Oxygen molecule
What does the binding of the 1st Oxygen molecule cause?
Causes a conformational change in the Haemoglobin (Hb)
Making the Haem groups more accessible to Oxygen
What is the Bohr Affect?
Haemoglobin’s (Hb) oxygen binding affinity is inversely related to the concentration of Carbon Dioxide
Causing the Oxygen Dissociation Curve to shift
What is the Cardiac Cycle?
Sequence of events that occur within one full beat of the heart
