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143 Cards in this Set
- Front
- Back
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Explain passive diffusion. |
Very small, uncharged polar molecules, gases, water, and urea can all get through the phospholipid bilayer. They just "wiggle" their way through the cracks. |
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Explain facilitated diffusion. |
a) A channel protein acts like a "hallway" and molecules that are the correct shape (one kind per protein) can get through without any added energy. OR b) a carrier protein works by the solute binding to it, causing a conformational change that makes it release the solute out the other side. These proteins can move around in the membrane before releasing the protein. BOTTOM LINE OF FACILITATED DIFFUSION: NO ATP ADDED |
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Explain primary active transport.
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ATP is added to move solute up its gradient rather than down (e.g. with a pump protein).
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Explain secondary active transport.
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Uses electrochemical gradient - H+. The potential energy from the uneven distribution of charge can be used to transport solutes without the direct involvement of ATP - ex. symporter/cotransporter protein |
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What is the fundamental difference between active and passive transport? |
Active transport uses energy. Passive transport does not.
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What does it mean that a lipid bilayer is selectively permeable? |
Only certain thing can cross it.
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Give examples of molecules with high permeability.
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Gases (CO2, N2, O2), very small uncharged polar molecules (ethanol)
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Give examples of molecules with moderate permeability.
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Water, urea
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Give examples of molecules with low permeability.
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Polar organic molecules (glucose)
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Give examples of molecules with very low permeability. |
Ions (Na+, K+, etc.), charged polar molecules and macromolecules (amino acids, ATP, proteins, polysaccharides, nucleic acids)
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What is a gated channel protein?
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Channel protein that can open and close.
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List two common types of gated channels and briefly explain how they are opened. |
1) ligand-gated channel - ligand (molecule) binds to a receptor site on the protein and makes it open/close. 2) voltage-gated channel - activated by a change in voltage
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How are gated channels different than aquaporin?
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Aquaporin doesn't open or close, it's just installed or not based on ADH
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What are transporter proteins? |
A protein that moves molecules within an organism.
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Do all transporter proteins require energy?
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Nope! Carrier proteins don't.
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What is a pump protein?
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Uses ATP to pump solute against gradient.
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What is a cotransporter?
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Uses an electrochemical gradient as the push to push a revolving door, sort of.
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Why are electrochemical gradients important for some types of active transport?
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Secondary active transport uses the potential energy from the electrochemical gradients.
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Do transporters that use electrochemical gradients have binding sites for ATP? |
No. |
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List 3 reasons (and cite an example for each) for concentrating solutes using active transport.
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1) To make water move where we want it (e.g. stomatal opening). 2) to transport something (e.g. sucrose in plants, waste), 3) to create a favorable gradient for another process (ex. H+ for ATP synthesis)
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What is water potential and in what units is it measured? |
Water potential = the potential energy of water. Measured in mPa (megaPascals)
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Explain what it means that water potential in plants depends upon solute potential and pressure potential. |
Water potential = solute potential + pressure potential.
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What is the relationship between solute concentration and solute potential?
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Higher [solute] -> lower solute potential
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How are pressure potentials created within plant cells? |
The cells pushing itself against the cell wall
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What is turgor pressure? |
Pressure that the cell wall exerts on the cell membrance
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Explain what is meant by hypertonic, hypotonic, and isotonic.
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Hypertonic = hyperosmotic (high [solute]), hypotonic = hypo-osmotic, isotonic = iso-osmotic
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What is a turgid/flaccid/plasmolyzed cell & how can you predict which one a cell will become?
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Turgid = cell membrane pushing against cell wall (H20 in) - fully turgid cell pressure potential = 1.1 mPa, flaccid = membrane loose. Pressure potential = 0. Equilibrium. Plasmolyzed cell = membrane pulle away. Pressure potential = 0. H20 out
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Why is it important for plants to be able to open and close stomata?
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To keep them from losing too much water |
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What are guard cells and where are they located?
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Guard cells are the doors to the stomata. Turgid cells = open, flaccid = closed
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List the series of steps involved in stomatal opening by guard cells.
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1) Blue light activates H+-ATPase, 2) H+ is pumped out of the cell 3) voltage-gated K+ channel activates - K+ moves in 4) H+/sucrose symporter activated - sucrose moves in, 5) increased [solute] makes H20 flood in through aquaporin 6) guard cell becomes turgid, stoma opens |
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Trace the path of water from the soil to the atmosphere in detail.
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x |
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What is the cohesion-tension theory? How does H+ bonding relate to this theory? |
Cohesion tension theory: water = cohesive (because of H+ bonding among H2O molecules), so when water molecules evaporate from plants, there's high surface tension and a meniscus forms that pulls on neighboring liquid water molecules and eventually water in the nearest vein (and therefore the plant's whole water supply). So, because of the cohesion of water and the tension on the water at the surface, a stream of water can be pulled up through the plant body. |
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Which mineral nutrients are necessary for photosynthesis?
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nitrogen, magnesium, manganese, iron, copper, zinc
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How to mineral elements enter a plant?
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with water!
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What is the major function of roots? |
To absorb water (+ nutrients)
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Why are root hairs important to plants?
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To increase the surface area of the roots for more efficient + faster absorption of water
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Describe the 3 major paths that water and ions can travel from the root hairs to the vascular cylinder. |
1) transmembrane 2) symplastic - through plasmodesmata 3) apoplastic |
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Describe the major tissue layers in the root.
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epidermis = thin "skin," root hairs = extension of epidermal cells. cortex = undifferentiated cells - outside layer. then endodermis - inside skin (impregnated w strip of suberin = casparian strip), vascular cylinder (stele)
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Why is the Casparian strip important to plants (2 major reasons).
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1) bad things can't get into xylem 2) easier to maintain a soute gradient
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What is xylem?
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1) dead at maturity 2) thick cell walls 3) impreganted w lignin -> strong & impervious to H20 4) have pits/pores
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What is xylem parenchyma?
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cells H20 & selected ions pass through until they reach tracheids or vessels
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What is xylem loading?
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taking ions and putting them in xylem
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Vessel elements vs. tracheids
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tracheids = long & skinny, pits on sides and ends, vessel elements = short & fat; pits on sides & perforation plates on ends
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What is bulk flow?
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movement of fluid through a tube. cost = vicosity * length/(radius)^4 |
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Why do plants have both vessels and tracheids?
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Vessels move fluid at a lower cost but are more prone to embolism than tracheids
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What is cavitation? Why is it bad for plants?
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When transpirtation occurs faster than water can be drawn upwards, an air bubble (embolism forms), blocking the flow of water to tissues above the point of embolism & causing them to die
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Why does transpiration occur?
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Transpiration causes the flow of water
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What environmental factors affect the rate of transpiration in plants?
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Humidity, heat, wind level
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What is the main driver of water flow from soil to root? Explain.
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Solute potential - big [solute] inside endodermis (made possible by the casparian strip), much lower at the root
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What is the main driver of water flow through the xylem to the leaf? Explain.
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Pressure potential - low pressure at the top, high pressure at the bottom
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Why can't plants grow to infinite heights? |
Gravity exerts pressure at the top, so there isn't lower pressure at the top anymore
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List some ways that plants can minimize transpirational water loss through stomata. |
Sunken stomata, leaf hairs |
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What are sources and sinks? List examples.
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Source - leaf, sinks - fruits, seeds, leaves at night, roots
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Explain the basics of the pressure-flow hypothesis.
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High [solute] at source STEs -> water flows in -> turgid cell -> high pressure. Low [solute] at sink STEs -> no water -> not turgid -> low pressure |
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Describe the basic structure and function of phloem cells. Why are STEs dependent on CCs?
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STEs have no nuclei, CCs keep them alive by synthesizing mRNA and proteins for them.
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What is phloem loading?
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Process of moving sugars from mesophyll thorugh the CCs to the STEs
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What is phloem sap? |
Sugary fluid
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Describe two different ways of phloem loading that are commonly found in plants.
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1) through plasmodestmata 2) sucrose symporter
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Why are plasmodesmata important for phloem loading?
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They allow for passive transport
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Which way of phloem loading requires ATP?
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Sucrose symporters (but not directly)
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Why would simple diffusion of sugars through the phloem be an inefficient method for sugar translocation? |
Doesn't work over long distances
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Why is it important for sugar transport that the phloem be located adjacent to xylem?
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Water must flow in for the pressure-flow hypothesis to worok
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Which way would sugar be transported through phloem in the absence of a strong turgor pressure gradient - from source to sink, or sink to source? Explain.
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Source to sink because of solute gradients, but slowly and innefficiently
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Compare and contrast water flow through the xylem and sugar transport through phloem.
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Xylem pulls, phloem pushes
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What is the ER?
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Network of membranes that do lots of jobs, basically
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Explain why differing solute concentrations on either side of a membrane are balanced by water movement rather than by solute movement.
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The solutes can't get through, so water moves to balance the concentration. |
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Which types of transporter proteins are enzymes? What is the substrate for transporter proteins that are enzymes?
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Primary active transporter proteins, like pumps, break down ATP.
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What would happen to a plant cell in a normal, everyday plant if it were placed in ocean water?
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It would become plasmolyzed because the water potential of the surrounding water is so much lower than inside the plant.
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Why do open stomata pose a problem for plants? What are the benefits of open stomata? |
Open stomata = water loss. But also CO2 in, which is very important!
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What kinds of transmembrance transport occur across guard cell plasma membrances during the process of stomatal opening? What kinds of membrane proteins are involved, and which use ATP?
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H+-ATPase <- USES ENERGY, K+ channel (voltage-gated), H+/sucrose symporter
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Think about two adjacent plant cells (call them cell A and cell B). In cell A the solute potential is -0.4 MPa and in cell B, the solute potential is -0.6 Mpa. Is cell A hypotonic or hypertonic compared to cell B? Which way will water flow?
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Cell A is hypotonic to cell B. If the pressure potential is 0, water will flow into cell B. If it's not zero... we don't know because we don't know the pressure potential. |
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If cell A has solute potential -0.4 MPa and pressure potential 0.2 MPa and cell B has solute potential -0.6 MPa and pressure potential 0.5 MPa, which way will water flow?
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Water will flow into cell A.
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How is ATP synthase similar to the K+ chanel in guard cell membranes?
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It requires an H+ gradient to function.
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Why is aquaporin necessary if water can cross biological membranes?
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Diffusion is slow and doesn't work over long distances.
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Does solute transport in xylem require energy?
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No, because it just gets pulled along with the water.
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Would you expect to find heavy metal ions (i.e. a non-nutrient ion) like aluminum in the leaf? Why or why not?
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No, because it gets blocked by the casparian strip.
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Why are plasmodesmata important in water flow through the root?
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They allow water to flow more efficiently
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Imagine that while looking at a cross section of a leaf under a microscope, you observe a thick coating of hairs on the leaf and sunken stomata. Does this plant live in a wet or dry environment? Explain how you know.
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Dry environment. Those are adaptations to prevent water loss.
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Would you expect the rate of transpiration from a plant to increase or decrease on a cool, rainy day, compared to normal environmental conditions? |
Slow - a much shallower gradient between the water coating the miniscus/air inside the leaf and the outside.
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How does a cool, rainy day affect the rate of water flow throguh the xylem? Explain your answer.
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Slows it because the water is not evaporating as quickly off of the miniscus so there is less pull upwards.
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Does the likelihood of cavitation within the xylem increase or decrease on a hot, sunny day, compared to normal environmental conditions? Explain.
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Yes, because water is getting pulled up faster, resulting in more and more tension.
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What might happen to the top of a tall redwood tree during a dry summer, and why? |
It dies because there's not enough water (OR an embolism forms near the top because of not enough water and it dies)
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Where does the water in phloem sap come from?
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The xylem
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Why are sieve tube elements near sugar sources turgid? Now, think about hte pressure-flow hypothesis. Why might sieve plates be important for the pressure gradient in sieve tubes?
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High [solute] -> water flows in. Sieve plates offer resistance to create the pressure gradeint that makes phloem sap move from source to sink
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How does active transport of sugars from the sieve tube elements into the companion cells at sugar sinks help to maintain a pressure gradient in the phloem?
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Keeps [solute] low in sink STEs, so water doesn't flow in and cause the cells to become turgid
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Can leaves ever be thought of as sugar sinks? |
Yes, at night!
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Does water transport require energy?
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No
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Does sugar transport require energy?
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Sort of - active transport of sugars at the sinks. But the transport of phloem sap doesn't require energy.
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Why are all mesophyll cells located very close to leaf veins?
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So they can dump sugar into the phloem and get water from the xylem.
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How are sieve tubes similar to and different from vessels? |
they're shaped kind of the same but they transport different stuff
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Does it make sense that a sugary fluid like phloem sap could NOT be transported through sieve tubes as easily as water flows through xylem? |
Yes; phloem is very viscuous, so the cost of bulk flow is higher for it.
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What are the functions of a circulatory system?
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1) distribution & transport of nutrients, oxygen 2) collection of wastes 3) circulation of cells 4) circulation of proteins 5) thermal stabilization (in large animals)
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What are the components of circylatory systems? |
Some liquid to suspend solutes, variable kinds of cells, and SOMETIMES vessels to convey liquid to parts of body & mechanism for moving liquid in these vessels |
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What kinds of circulatory sysytems are there? Explain each.
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1) gastrovascular cavity - combined digestive & circulatory system 2) open circulatory system - hemolymph flows inside the dorsal blood vessel and in spaces among organs 3) closed circulatory system
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What are the pros & cons of a closed circulatory system?
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Pros: 1) faster, more efficient, and EVENTUALLY 2) maker higher metabolisc rate likely and 3) makes larger body size possible. Cons: Hydrostatic pressure-related problems
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What are arteries/veins/capillaries?
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Capillaries = sheet of cells rolled up into a tube, usually fenestrated (holey). Arteries take blood away from the heart and veins take blood towards the heart.
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Compare veinlets of plants to capillaries.
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Xylem doesn't join up with phloem, but capillaries join veins + arteries
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Why are fishes said to have single circulation, while mammals and birds are said to have double?
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They have just one atrium and ventricle, while mammals and birds have 2 of each, thus separating oxygenated and deoxygenated blood.
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Why would CO2 be predicted to always diffuse away from metabolizing cells in living tissues? Why would O2 be expected to diffuse the other way? |
Metabolizing cells are using up O2 and producing CO2 so high [CO2] -> goes away, low [O2] -> comes in
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Why is blood pressure greatest at the aorta, or artery leading directly from the heart?
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Blood is moving fastest there. |
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Why might hyperosmolarity of the blood eventually cause elevated blood pressure?
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Water comes in, too much volume = higher hydrostatic pressure.
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Does blood entering the systemic circulation have higher or lower pressure than blood leaving? Explain.
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higher pressure
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Why is the ventricular blood of amphibians and certain reptiles said to be mixed?
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While there are flaps of tissue in the ventricle to keep blood from the right & left atria separate, it's not a perfect system and it is all going into one ventricle.
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Of what benefit is cutaneous gas exchange, as seen in amphibians that are mostly aquatic? |
Can respire underwater.
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What are the components of blood?
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cells, plasma (water, solutes)
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Serum vs. plasma
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Serum has no clotting proteins |
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What do platelets do?
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repond to ligands released by injured capillary cells
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What are capillary beds and how do they work?
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Water potential moves H2O and solutes in and out, basically
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Where is the lymphatic system and what does it do? |
Located in the thymus, spleen, lymph nodes around the body. Uses: fatty acids transport, lymphocyte highway, nursery, and graveyard, nodes filter rids IF of dead lymphocytes, bacteria, migrating cancer cells, + ADJUSTS AMOUNT OF IF
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What makes your heart beat?
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Electrical impulses from specialised cells and innate contractibility of muscle fibers
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neurogenic vs. myogenic heart
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Neurogenic - signal comes from the cardiac muscles. Neurogenic - heart won't beat without regular electrical impulses from the nervous system
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How does blood return from toes to genereal circulation?
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Muscles in legs contract and squeeze veins & there are passive one-way valves that keep blood from going downwards |
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What are varicose veins/how do they happen?
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When veins are habitually subjected to high blood volum (pressure), veins with stretch (curl) & bulge out
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Which plasma contents exist as solutes? Which plasma contents have sizes that prevent them from leaving capillaries through fenestrations? Which plasma contents don’t affect osmotic rates (that is, don’t prevent or don’t promote osmosis)? |
x |
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Would the gastrovascular cavity be classified as an open or a closed circulatory system? Explain your answer. |
x |
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Compare and contrast the following: coelomic fluid, hemolymph, blood, lymph, interstitial fluid (IF). |
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Explain which of the following are likely to have clotting properties: a) bedbug hemolymph b) chicken blood c) earthworm blood d) newt blood e) rhinoceros blood f) butterfly hemolymph |
x |
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Do plants have capillary beds? Vascular tissues? Explain your answer.
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x |
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In which type(s) of vertebrate circulatory system a) does the heart handle only deoxygenated blood? b) can the cycle of blood flow be described as ‘simple’, and why? c) does the heart completely separate the handling of oxygenated and deoxygenated blood? d) does pulmocutaneous respiration play a part? e) does gas exchange happen via gills? f) does gas exchange happen via lungs? |
x |
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Like platelets, red blood cells (or RBCs, or erythrocytes) are specialized cells that have incomplete sets of organelles (no nuclei, for instance). How do they differ in function?
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x |
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Compare your arteries, arterioles, veins, venules, and capillaries with regard to: a) wall thickness and composition b) type of blood conveyed within c) direction of blood flow, relative to the heart d) presence of an endothelium e) presence of muscles |
x |
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Collagen, like fibrin, is a protein. How do they differ?
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x |
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Where does lymphatic fluid come from? What solutes may be present in lymphatic fluid? |
x |
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Of what value is pulmocutaneous blood circulation to amphibians? |
x |
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What is respiration?
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Gas exchange via an organ.
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What are some common features of respiratory systems? |
Large surface area, short distance to diffuse, take advantage of solubility of gases in water and use the steepest possible gradient.
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What are some common respiratory systems (4)?
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External gills, internal gills, tracheoles, lungs
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What is countercurrent exchange?
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Blood flow runs opposite air flow so there's always a gradient.
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How do external gills work?
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Simple diffusion.
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How do tracheoles work?
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Air enters via spiracles, tracheole tips are covered in water which creates a gradient.
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Internall gills
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Water runs across gills countercurrent to blood.
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Mammalian lungs |
Air flow is tidal, caused by changes in pressure created by the intercostal muscles contracting.
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Bird lungs
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Blood:air flow is counter current due to the existence of air sacs and parabronchi making the flow of air one-way
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Do gases diffuse faster in air or water?
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About 1000x faster in air.
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How do small organisms transport O2/CO2?
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Simple diffusion accross their surfaces.
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How do arthropods and annelids transport gases?
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Gases dissolvei n hemolymph (arthropods) and coelomic fluid (annelids).
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How do very large organisms transport O2/CO2?
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Hemoglobin!
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What is partial pressure?
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Relative abundance. pO2 determines how much will bind to Hb
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What is cooperativity?
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1st heme binds O2 -> conformational change -> next heme can bind O2 more easily. Works in reverse also.
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What is the graph of pO2 vs Hb saturation called and what is it shaped like?
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Hb-O2 association-dissociation curve. S-shaped, or sigmoidal, curve.
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When would the S-curve shift left? Right?
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Low CO2, low pH, low temperature. Right - opposites.
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Why is it adaptive that myoglobin and fetal Hb are left-shifted?
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Muscles need lots of O2 and fetuses need to be able to grab O2 from maternal Hb.
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How is CO2 transported in the blood?
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7% - in plasma. 23% - non-heme parts of Hb (->carboxyhemoglbin). 70% reacts with H20 to form carbonic acid, which ionizes into H+ and bicarbonate-. Hb picks up H+ to prevent pH drop and bicarbonite exits to plasma where it helps maintain pH at 7.2-7.4
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