mass transport Flashcards
what factors affect haemoglobin binding with oxygen
-partial pressure of oxygen
-partial pressure of carbon dioxide
-saturation of haemoglobin with oxygen
How does partial pressure affect oxygen binding with haemoglobin
-as the partial pressure of oxygen increases, affinity of oxygen also increases
-saturation levels increase
-when partial pressure is low, oxygen is offloaded
name some common features of a mammalian circulatory system
-suitable medium for transport
-means of moving medium throughout the body
-means of controlling flow of medium
what happens during cardiac diastole
-heart is relaxed
-blood enters the atria
-increases the pressure and opens the atrioventricular valves
-blood can move into the ventricles
-semilunar valves are shut
what happens during atrial systole
-atria contract and force any blood into the ventricles
what happens during ventricular systole
-ventricles contract
-atrioventricular closed to prevent backflow, and semilunar valves open to allow blood into the aorta and pulmonary artery
How does tissue fluid form
-high hydrostatic pressure forces the tissue fluid out of capillaries
-tissue fluid bathes the surrounding cells
-returns to the capillaries when the hydrostatic pressure is low enough
what are the three components of phloem vessels
-sieve-tube elements, transports sucrose in the form of sap across the phloem
-companion cells, involved in ATP production for the active transport of sucrose into the sieve tubes
-plasmodesmata, gaps between cell walls where the cytoplasm can flow to allow substances to flow
name the process where sucrose is transported around the body of a plant
translocation
how does sucrose in the leaf move into the phloem
-sucrose enters the companion cell via active transport (active loading) that uses ATP and H+ ions.
-sucrose then diffuses from companion cells into sieve tube element via plasmodesmata
how do phloem vessels transport sucrose around the plant
-as sucrose enters the sieve tube elements, it lowers the water potential in the phloem
-water from the xylem moves by osmosis into the sieve tube elements
-increases the hydrostatic pressure, water moves towards lower hydrostatic pressure
-sucrose diffuses into surrounding cells where it’s needed
Give evidence for the mass flow hypothesis of translocation
-sap is released when a stem is cut, so there must be pressure present
-there is higher sucrose concentration in the leaves than in the roots
give evidence against the mass flow hypothesis of translocation
-structure of sieve tube elements seems to hinder mass flow
-not all solutes move at the same speed as they would in mass flow
how can ringing be used to investigate transport in plants
-bark and phloem of tree are removed, leaving only xylem
-eventually tissues above the ring swells due to accumulation of sucrose
-so sucrose must be transported in phloem
how can tracing be used to investigate transport in plants
-plants grown in presence of radioactive carbon dioxide (carbon 13)
-using autoradiography, we can see the areas exposed correspond to where phloem is
-as the carbon dioxide is incorporated into the sugars.
