Introduction to Transport in Plants - Fall 2023 PDF

Meet w/Speaker 2:30-3:30 BI 415 Today! Biology Department Seminars Wednesdays @ 4 pm BI 234 ➢ Exam 1 ➢ Read the question ➢ Answer the question ➢ Where does this reaction occur? CO2 + H2 O ↔ H2 CO3 ↔ HCO3− + H + ➢ Why is it important for nutrient acquisition? Big Picture pp. 838-839 ➢ Exam review...

Meet w/Speaker 2:30-3:30 BI 415 Today! Biology Department Seminars Wednesdays @ 4 pm BI 234 ➢ Exam 1 ➢ Read the question ➢ Answer the question ➢ Where does this reaction occur? CO2 + H2 O ↔ H2 CO3 ↔ HCO3− + H + ➢ Why is it important for nutrient acquisition? Big Picture pp. 838-839 ➢ Exam review is important! ➢ Review through Thursday, 9 Nov ➢ Reminder Office Hours ➢ T&R 12 – 2 pm or by appt. ➢ drop-in or sign-up for 10-15 min slot Four Overarching Themes Multicellular organisms: ✓Create and maintain their structure. ✓Obtain and use nutrients and energy. • Balance water and solutes, and transport fluids and gases. • Sense and respond to the environment (internal and external). Big Picture pp. 838-839 1 Transport in Multicellular Organisms Learning Objectives Transport in Multicellular Organisms Learning Objectives 1. Describe the pathways in which solutes and gases are transported between cells in plants and animals. 1. Describe the pathways in which solutes and gases are transported between cells in plants and animals. 2. Explain the challenges of transport over long distances in a multicellular organism. • What do you recall from BIOL 205? 3. Describe the principles of fluid flow and gas exchange along with the structure and function of tissues and organ/organ systems specialized for long-distance transport in plants and animals. • Discuss with neighbor(s) one cell-to-cell pathway that transports solutes or gases 4. Explain how water balance is achieved and maintained in plants and animals. Transport in Multicellular Organisms • To survive, multicellular organisms must transport and exchange fluids and gases between locations within their bodies • What materials are in these fluids and gases? • • • • • Nutrients Water Gases: O2 , CO2 Waste Others? • How are they transported? Transport in Multicellular Organisms • A system of tube-like vessels is the common evolutionary solution. However, mechanisms of transport vary • Plants use pressure gradients and pressure potentials to transport water, minerals, and sugars through specialized tubes; what are these tubes? • Animals use a pump to move circulatory fluid through tubes called vessels; the pump creates pressure; the vessels can form open or closed circulatory systems 2 Transport in Multicellular Organisms Transport in Multicellular Organisms • The exchange of certain gases with the environment is essential for life: • Both plants and animals have evolved highly convoluted surfaces that increase the area available for gas exchange • Respiration by plants and animals requires taking up O2 and releasing CO2 • A few examples: • spongy mesophyll • roots • gills • alveoli • With photosynthesis, net exchange occurs in the opposite direction: CO2 uptake and O2 release This is a crayfish Fig.10.19 Transport in Multicellular Organisms • General means of transport? • Gravity • Pressure gradients • Electrochemical gradients (charged substances) Transport in Multicellular Organisms • Transport where & how? • Cell to cell? Tissues? Organs? • Distance? • Short • Long • Throughout the body? • Circulation? • Concentration gradients (entropy-driven) 3 Transport in Multicellular Organisms Transport in Multicellular Organisms • All Transport requires some form of energy • All transport requires some form of energy • Passive & Active Transport • Passive • Energetically “downhill” • Spontaneous process (thermodynamically favorable) • Active • Energetically “uphill” • Requires metabolic energy (often ATP hydrolysis) • Secondary Active Transport (cotransport) • Two substances move (“one uphill, one downhill”) • Symporter – same direction • Antiporter – opposite directions Transport in Multicellular Organisms • Mechanisms of Transport • Diffusion • by random, molecular motion can occur across membranes; short distances Fig. 6.27 Complete the figure. Differentiate b/w active and passive transport; b/w simple and facilitated diffusion, using examples. Transport in Multicellular Organisms • Mechanisms of Transport: Diffusion • Short-distance • Osmosis • water movement across membranes; short distances • Pump, Channel, and Carrier-mediated transport • ions/small molecules across membranes; short distances • Bulk Flow • efficient, mass movement driven by hydrostatic pressure – Pressure Gradient; long distances Fig. 6.13 Which mechanisms are passive, which active? What force typically opposes hydrostatic pressure across membranes? What controls diffusion across a membrane made of a lipid bilayer? Transport in Multicellular Organisms Transport in Multicellular Organisms • Mechanisms of Transport: Diffusion • Short-distance transport primarily regulated by membranes • Mechanisms of Transport: Diffusion • • • • • • • Fick’s Law of Diffusion • describes the factors affecting the rate of diffusion SA:V is critical H2 O Sugars & other fuels Ions Gases Proteins, hormones, etc. How are membranes modified to increase surface area? Name some membranes where transport occurs. 4 Transport in Multicellular Organisms • Mechanisms of Transport: Diffusion • Fick’s Law of Diffusion • Equation: example using gases, e.g., O2 Fig. 42.3 Fig. 6.9 Transport in Multicellular Organisms • Mechanisms of Transport: Osmosis • Diffusion of water across a selectively permeable membrane • Water molecules move from high [ ] to low [ ] • Until when? • What happens when solutes are added? Fig. 6.14 What do aquaporins do? Transport in Multicellular Organisms • Mechanisms of Transport: Active Transport • ATP driven cation pumps, a few examples: H+ Na+- K+ H+ - K+ Ca2+ Transport in Multicellular Organisms Mechanisms of Transport: Active, Pump • Recall: the potential to do work = the gradients of concentration and of electrical charge across the membrane = Electrochemical Gradient plants, fungi animals animals, plants, fungi Can you describe other ATPase cation pumps? Fig. 6.21 5 Transport in Multicellular Organisms Transport in Multicellular Organisms • Mechanisms of Transport: Active, Pump • ATP driven proton H+ pump: main pump in plants and fungi • Establishes three gradients: • • • • • Mechanisms of Transport: Active, Pump • ATP driven Na+-K+ pump: main pump in animals • Also, establishes electrochemical gradients pH Concentration (chemical) Electrical Together = Electrochemical Fig. 36.10 Name 3 conditions across the cell membrane which will be maintained in disequilibrium as a result of the action of proton pumps? Fig. 6.26 Transport in Multicellular Organisms Transport in Multicellular Organisms • Secondary Active Transport = Cotransport Mechanisms of Transport • Secondary Active Transport = Cotransport • Proton pump glucose symporter example: • Moves substances against their [ ] gradient • Generalized example: Fig. 35.19 Transport in Multicellular Organisms • Mechanisms of Transport Fig 35.20 Transport in Multicellular Organisms • Mechanisms of Transport: Bulk Flow • Long-distance transport is pressure dependent What about long-distance transport? • Where are materials being transported? • What “drives” long distance transport? • Bulk flow: • Mass movement of molecules from areas of high pressure to areas of low pressure = Pressure Gradient • Transport of materials is between cells, i.e., through openings or pores between cells • Quicker than diffusion or osmosis • Occurs via plant and animal vascular systems • What creates the pressure? 6 Transport in Multicellular Organisms Plants need water for? • Physical support • Chemical reactions • Photosynthesis • Others? • Temperature control • Transport of solutes • Pathways? Fig. 11.11 Transport in Multicellular Organisms Animals need water for similar reasons…. • Physical support • Chemical reactions • Bicarbonate • Others? • Temperature control • Transport of solutes • Pathways? Organism of the Day Giant Sequoia Sequoiadendron giganteum Grows to 95 m tall with diameters up to 12m. Can live to 3,000+ years! Bark is fibrous, reddish-brown, furrowed. Needles 3-6 mm long; dark brown seeds 4-5 mm long and 1 mm wide. Range: limited to stands on the west side of the Sierra Nevada Range between 4,0008,000 ft. Okay, not native to Washington, but there are several on campus. Can you find one? What mechanisms move solutes in organisms? What two forces move water in organisms? Lecture Outline How does water get from roots to shoots and leaves? Transport in Plants Transport in Plants • Why plants need water • Water Potential • Water & Solutes • Xylem - water and mineral transport • Roots to shoots • Cohesion-Tension Theory • Phloem - solute translocation • Source to sink • Pressure-Flow Hypothesis • Gas exchange 7 Transport in Plants Transport in Plants Why do Plants Need Water Why do Plants Need Water • Why do plants need water? • How do terrestrial plants obtain water and mineral nutrients? • • • • Photosynthesis Transporting solutes Cooling the plant Internal pressure for support (structure) • Plants lose large quantities of water to evapotranspiration -- this must be replaced • Ex., a large Douglas-fir (Pseudotsuga menziesii) can lose up to 425 liters of water per day! • Where does the water come from? • How does it get to the plant? • How does it move through the plant? Transport in Plants • Recall: Vascular tissue system = the transport system xylem tissue Transport in Plants Transport in Plants Water Potential Water Potential • Vascular tissue system = the transport system • Water uptake requires water to move through cell membranes • Diffusion = • How? • Diffusion phloem tissue • passive transport of a substance from a region of high concentration to one of low concentration; i.e., down a concentration gradient. 8 Transport in Plants Water Potential • Osmosis, a type of diffusion = • movement of water across a selectively permeable membrane from a region of high water [ ] to a region of low water [ ] • Is osmosis passive or active transport? • Review BIOL 205 osmosis lab…. Transport in Plants Water Potential (ψ) • Water Potential (ψ) = • ψ is a measure of the free energy in a volume of water • the overall tendency of a solution to take up water from pure water • Ψ = the sum of its negative solute potential (Ψs) and pressure potential (Ψp) 𝜓 = 𝜓𝑆 + 𝜓𝑃 Transport in Plants Transport in Plants Water Potential (ψ) Water Potential (ψ) 𝜓 = Psi 𝜓 = Water Potential 𝜓 = 𝜓𝑆 + 𝜓𝑃 • Influenced by presence of solutes and pressure • Water always moves from high Ψ to low Ψ 𝜓 = 𝜓𝑆 + 𝜓𝑃 Transport in Plants Water Potential (ψ) • Solute potential (ψs) • Solute potential (aka osmotic potential, ψs): • Solutes bind water molecules removing free water from the solution • What happens next? • water potential (ψ) is lowered • ψs is always negative • b/c relative to pure water; ψ = 0 𝜓 = 𝜓𝑆 + 𝜓𝑃 Give an example of solutes that bind with water molecules (hint: ionic). 9