EE BIOL 162 Study Guide - Midterm Guide: Heat Sink, Disaccharide, Enzyme Inhibitor
8 Jun 2018
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Midterm Study Guide Questions (Spring 2015)
1. What are 3 features of cells that are distinctive and typical of plants?
• Cellulose cell walls
• Vacuoles
• Chloroplasts
2. What are 5 characters that might define a good model plant for understanding
genetics and physiology?
• Easy to manipulate
• Easily identifiable traits that you can see mutants for
• Easy to grow/short life cycles
• Sequenced genome
• Self-fertilizing
3. What is the difference between apoplast and symplast?
• Apoplast = diffusional space in cell walls
o Includes xylem
• Symplast = diffusional space in cytoplasm
o Includes phloem
4. Which is a better system to conduct water?
• Apoplast → water travels faster if it does not have to move through the plasma
membrane
5. Which is a better system conduct large biomolecules?
• Symplast → biomolecules are "expensive," so only want to send it to target areas
o Transportation through the apoplast can go anywhere in the cell, but
transport through the symplast/plasmodesmata is concentrated to target
areas (more controlled)
6. What are three major kinds of plant tissues and their functions?
• Dermal: prevents H20 loss, lets light through for photosynthesis, protection
• Ground: photosynthesis and metabolism, structural & mechanical support
• Vascular: transports H20 and nutrients
7. Where are the major plant tissues located?
• Dermal – located on surface of plant (roots, stems, leaves)
o Epidermis: single layer of cells (upper pavement and lower)
o Cuticle: waxy layer to prevent H2O loss
o Guard cells: regulate gas exchange in stomata
o Root hairs: increase SA and water uptake
• Ground – located in leaves and stems
o Parenchyma
▪ Soft and thin-walled
▪ Metabolically active
▪ Function in metabolism and photosynthesis
▪ Include palisade mesophyll and bundle sheath cells
o Collenchyma
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▪ Narrow, hard & flexible, elongated cells with thick primary walls
▪ Provide structural support to the growing plant body
▪ Can stretch as organs grow (found in stem periphery, petioles)
o Sclerenchyma
▪ Provides mechanical support particularly to non-elongating parts of the
plant, hard and woody, short cells
▪ Consists of two types of cells → sclereids and fibers
o Both have thick secondary walls and are frequently dead at
maturity
▪ Sclereids
o Occur in a variety of shapes, ranging from roughly spherical to
branched
o Widely distributed throughout the plant
▪ Fibers
o Narrow, elongated cells that are commonly associated with vascular
tissues
• Vascular – located in stems
o Xylem (up)
▪ Conduction of H20 and nutrients
▪ Conducting tissue composed of tracheids (gymnosperms) and vessels
(angiosperms)
▪ Vessels are composed of vessel elements
▪ Contain parenchyma and sclerenchyma
o Phloem (down)
▪ Conduction of sugars and signal molecules
▪ Conducting tissue composed of sieve cells (gymnosperms) and sieve
tubes (angiosperms)
▪ Sieve tubes are composed of sieve elements
▪ Contain parenchyma and fibers
8. Describe the diversity of plants and plant physiology:
• Taximonic Diversity:
o 700 species of gymnosperms and 250,000 species of angiosperms
• Life Form Diversity:
o Immense size variation, < few mm (duckweed) to 100 m (redwoods)
o Growth form variation of trees (single stem) to shrub (multiple stems), herb
(non woody) to climbers (vines)
• Variation in habitat → epiphytes (plants growing on other plants but not
parasitic), carnivorous plants, clonal population
• Biochemical and Structural Diversity
o Biochemistry and metabolism: C3, C4, CAM
o Nutrient and pigment concentrations
o Hormone sensitivity
o Structure (variation in cell size and tissue, leaf color, size)
• Habitat and Adaptation Diversity:
o Irradiance, different amounts of sunlight
o Moisture supplies (dry soil to wet soil to submersion plants)
o Temperature (-40 to 40 degrees C)
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9. Please give three reasons that plants need water, and indicate which of the three
reasons accounts for the bulk of the water used.
• Mass of plant – water makes up most of the mass of the plant cells (bulk
of content of vacuole, tissues). Plants must maintain water levels within
narrow limits or:
o Growth will cease
o Tissue becomes stressed
o Plant wilts or dies
• Transpiration – evaporation of water dissipates heat energy (passive
cooling)
o Transpirational cost – they open their stomata to access CO2 for
photosynthesis and exposes the moist plant to the drying air → water
is lost as a side effect, bulk of the water used
• Growth – if there is not enough water the stomata will close, stopping
photosynthesis and cause the plant to overheat, use a lot of water
because they have to open up their pores to get CO2, tissue expansion via
turgor pressure (structural support)
10. Why is transpirational cooling effective?
• Water is a heat sink due to its high specific heat from H bonding. Energy used to
heat up leaf used to evaporate water in the stomata/dissipate heat energy.
11. How high can water rise in cell wall pore capillaries (radius=100 nm)? How high in
xylem vessels (radius=25 um)?
• Capillary rise = 14.9*10^-6 m^2/radius
• 14.9*10^-6/100*10^-9 = 149 m (pore capillaries), 14.9*10^-6/25*10^-6 = 0.6
m (xylem)
12. Please explain and give the basis for two of the following four properties of water,
and give an example of why the properties are important for plant life:
• Supersolvent – water molecule is small and polar, good for ionic substances,
sugars, and proteins w/ polar groups, H bonds formed stabilize ions and
increase solubility → polar molecules easily dissolved
• High specific heat – H bonding increases energy required to raise temperature,
high latent heat of vaporization (convert liquid to gas), buffers temperature
change (transpirational cooling)
• High tensile strength – cohesion allows water to be pulled by negative pressure,
good for transport of water, pull = negative pressure/tension which develops if
there are no air bubbles, basis of transpiration (pull H2O from roots to leaves)
• High surface tension – H bonding causes cohesion and air water interface
minimizes its SA, expanding SA requires breaking of H bonds or energy (surface
tension), water attracted to solid phase (adhesion), supplies force for small-
distance transpiration
13. Explain these two forms of water transport:
• Diffusion: transport of molecules down a concentration gradient (driving force),
limited by diffusion coefficient (transport coefficient)
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Document Summary
Includes xylem: symplast = diffusional space in cytoplasm. S = -0. 5 mpa and p = 0. 5 mpa. Why do plants invest in such a tissue: the casparian strip filters what goes into the cell and performs selective ion uptake. It prevents water from entering the xylem from apoplastic route since it cannot regulate material water enters symplast and moves to xylem. Osmosis is used to cross this tissue because it is moving between cells symplastically in the endodermis. Without the endodermis, it could pick up toxic levels of ions or become infected. Osmosis: apoplast (only along cell walls to endodermis) bulk flow, suppose that a pine tree has tracheids of 10 (cid:586)m diameter, and a sunflower has vessels of 50 (cid:586)m diameter. Briefly, what are their roles: macronutrients n, k, ca, mg, p, s, si (new kangaroos can migrate past sweet. Where is it located: light harvesting antenna is where light absorption mainly occurs by chlorophyll.
