Gas Exchange, Digestion & Mass Transport (SR) Flashcards
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
What do Arteries and Arterioles do?
Transport blood away from the Heart
What do Veins and Venules do?
Transport Blood back to the Heart
What are Capillaries?
Small blood vessels which are the area of Metabolic Substance Exchange
How is Tissue Fluid Formed?
Arteriole: Hydrostatic Pressure > Water Potential
Water and solutes leave plasma from capillary
Venule: Hydrostatic Pressure < Water Potential
Water and solutes re-enter plasma in capillary if protein present
Remaining fluid returns to Circulation via the Lymphatic System
What occurs during Digestion?
Large Biological Molecules are Hydrolysed to smaller molecules that can be absorbed across cell membranes
What Digestion Enzymes are found in Mammals?
Amylase
Membrane-bound Disaccharidases (Maltase, Sucrase, Lactase)
Lipase
Endopeptidases (Pepsin, Trypsin & Chymotrypsin)
Exopeptidases
Membrane-bound Dipeptidases
What does Amylase hydrolyse and what does it form?
E1/E8
1) Starch
2) Maltose
What does Maltase hydrolyse and what does it form? (E2/E8)
1) Maltose
2) α-glucose molecules
What does Sucrase hydrolyse and what does it form? (E3/E8)
1) Sucrose
2) Glucose and Fructose
What does Lactase hydrolyse and what does it form? (E4/E8)
1) Lactose
2) Glucose and Galactose
What does Lipase hydrolyse and what does it form? (E5/E8)
1) Lipids
2) Monoglyceride & Fatty Acids
What do Endopeptidases (Pepsin, Trypsin & Chymotrypsin) hydrolyse and what does it form? (E6/E8)
1) Peptide Bonds in middle region of Proteins
2) Several polypeptide chains
What do Exopeptidases hydrolyse and what does it form? (E7/E8)
1) Peptide Bonds on Terminal Amino Acids
2) Release Single Amino Acids and Dipeptides
What do Membrane-bound Dipeptidases hydrolyse and what does it form?
1) Dipeptides
2) Single Amino Acids
What is the name of the final section of the Small Intestine where both hydrolysis and absorption occur?
Ileum
What do Bile salts do?
Emulsify lipids to increase surface area, for greater access to lipases
What are the products of Lipase Digestion?
Micelles
Remain in association with bile salts to form structures
Micelles travel to Ileum where they are broken down upon contact with the surface of Ileum epithelial cells
What do Micelles release when they are broken down?
Releases Non-polar Monoglyceride and Fatty Acids
These diffuse straight into the epithelial cell
How are Amino Acids and Carbohydrates absorbed?
Absorbed via Co-Transport with Sodium
What is used to transport water and mineral ions in plants against gravity?
Xylem vessels
How does water move up the Xylem?
Cohesion-Tension Theory:
1) Water evaporates from leaves (Transpiration) creating tension
2) Cohesive nature of water moves whole column up the Xylem
What is the Rate of Transpiration affected by?
1) Light
2) Temperature
3) Humidity
4) Wind
By what process does the Phloem transport Assimilates from sources to sinks?
Via Translocation
What occurs during Translocation?
1) Sucrose Actively Transported into companion cells and moves via diffusion into the sieve tube followed by water
Assimilates move from area of high to low pressure (mass flow)
2) At the sink, the solutes are removed, water leaving by Osmosis
How can Scientists track the movement of sugars through the Phloem?
Radioactive Isotopes are used in Tracer experiments
What is Ringing?
Removal of the bark and Phloem
Theoretically prevents Translocation to the sinks below the Ring
