Biol 371 Samuel Flashcards
What is the highest cause of death in children?
Malnutrition
Whats the difference between animal and plant nutrition?
nutrition- plants do work to create energy, animals just eat them to get energy.
The start codon ATG codes for the amino acid methionine, can humans make methionine?
No, we need them from plants- we can’t even make the molecules that is coded from our start codon ATG.
How many essential elements do plants need?
17
What do the essential elements that plants need do?
Components of nucleic acids (N, P), amino acids (N, S)
Function as enzyme cofactors (Ca2+)
Role in photosynthesis (Mg2+, Fe2+, Fe3+) or regulation of osmotic potential (K+)- need magnesium and iron in chlorophyll
What the 17 essential elements seperated into?
macro and micro nutrients
What are the macronutrients and how do they become available for plants?
Theres non minerals (C, H, O), and theres minerals (N, P, K, S, Ca, Mg), these are only avaible to plants once dissolved in water as they’re ionic form.
What micronutrients are essential for plants (MUST KNOW)
Cu, Cl, Ni- needed in small amounts but are required for plants grow
Give an example of what happens when plants don’t have trace micronutrients
Potatoes will not grow w out micronutrients
Can nitrogen as it’s form in air be utilized by plants?
NO, Nitrogen has to be converted into plant available compounds through n fixing bacteria, bacterial ammonification, or bacterial nitrification.
N fixation- N fixing bacteria convert N2 gas to NH3 which then dissolves and becomes NH4.
Ammonification- Bacteria break decaying organic nitrogen compounds and convert it into NH4
Bacterial nitrification- oxidizes nh4 and makes it into no3, plants convert it back to nh3 in the plant and then transport it throughout plant.
What do plants prefer to take up? NO3, or NH4
NO3
If you continuously harvest plants what happens to the n fixation system?
If you continuously harvest plants, bacteria can’t fix nitrogen at the same rate which would lead to n deficient plants.
Describe the symbiosis between root nodules and plants?
roots have nodules - plant cells “infected” by N2-fixing Rhizobium bacteria
Gaseous form of nitrogen hard for plants to take up, ammonia easier, bacteria are given houses and plants are given a usuable form of nitrogen.
How did nitrogen depletion cause us to resort to fertilizer?
In the past we used to move lands and let the soil regain it’s nitrogen by itself through natural processes, but needing to do more and more farming made us use all the nitrogen in the land. Needed to resort to fertilizer in order to get nitrogen needed to grow crops at rate needed.
What problem did fertilizers pose to crops and how was it solved?
Plants grew tall due to fertilizer (artificial nitrogen) but because they grew so tall they collapsed. Need a solution to this problem as we need plants to grow but no collapse on themselves.
Dr. Norman borlaugh found a way to make a tall plant shorter (shutting down a hormonal pathway required for stem elongation creating a dwarf breed) and then use fertilizer to increase the yield of these plants.
What is a gmo?
a genetically modified organism, requires a piece of dna not native to the organism.
What was a negative effect of creating dwarf plants in terms of the hormonal pathway?
By breeding these crops he shut downa hormonal pathway that allowed elongation. Because this hormone was shut down it made it shorter but this hormone was needed to avoid drought, so it made the gmo plants more drought sensitive.
What is a negative side effect of using Nitrogen fertilizers?
The fertilizers runoff into water causing algal blooms which bacteria feed on and consequently deplete oxygen. Animal life at sea floors then die.
What is eutrophication?
Enrichment of an ecosystem with chemical nutrients such as compounds containing nitrogen and phosphorous
Example: nitrogen depletes into groundwater, groundwater runs off into a water body, forms algal blooms which shade plants hindering plant growth, and absorb more nutrients, when these blooms die their decomposition process takes up so much oxygen that oxygen levels fall and fish begin to die
What humus?
is the dark organic component of soil formed by decomposition of plants, holds water and nutrients. Has a negative charge so nutrients (ions) stick to it ex: ammonium
What properties does the size of soil particles determine?
Water availability, and mineral availability
What do micronutrients do in terms of reactions?
Act as catalysts
What solution is there to avoid negative effects of fertilizer but still have abundant plant growth?
Want to manipulate plants to make their own nitrates or make all crops have a symbiotic relationship with root nodules.
Define chlorosis and what causes it
yellowing of plant tissues due to lack of chlorophyll, happens when there’s a deficiency in plant nutrients so the plant can’t photosynthesize any more
What is a hydroponic culture, how can it be utilized?
Is when you grow plants in solution w out soil, can see what nutrients is important to plant using this as you can remove one nutrient in the water at a time. If plant grows bad you removed an essential element- one that is necessary for growth/reproduction, cannot be subbed, and has metabolic roles.
What is soil solution?
Is the combo of water and dissolved substances that coats soil particles and fills pore space. Is available for plant uptake after gravity drainage (in which water is drained and concentration of ions and nutrients is increased).
Why are water molecules attracted by clay particles and humus particles?
Because humus particles are neg charged so attracted to pos water molecules
Because clay is alkaline due to minerals, gives it a high ph (more basic and more neg charged) so it sticks to water molecule smore.
Describe how minerals are made available in soil
Minerals are dissolved in water and passively enter plant roots in their dissolved form, they are selectively absorbed by roots via ion-specific transport proteins
why are both cations (Na+, Ca++, Mg++) and anions (NO3-, SO42-, PO43- ) are present in soil solution, but not equally available to plants?
Because soil is negatively charged so it repulses the anions but binds tight to cations, makes it so anions enter soil solution and are uptook by plants easier. However, they’re also washed away because of this easier.
Describe the connection between root systems and soil solution
The solution moves in and out of roots, extensive root systems are adaptations to limited mineral nutrients, and they make up 20-50% of the plants mass
Explain how cation exchange works?
As dissolved cationic minerals are bound onto surface of clay particles (adsorbed), it’s hard to take them up, plan addresses this by pumping out H+ in order to replace the cations on the soil with H+ so the minerals can then be taken up by the roots. Plants also does cation exchange by respiration, in which it realses co2 that creates carbonic acid which dissociates into H+- displacing the minerals which will be uptook by plant.
What is a negative side effect of anions not binding to clay particles, whats a positive side effect?
Anions (NO3, SO4, AND PO4) are neg so they don’t bind to soil and go up plant roots readily, however this is also bad because water can leech them out of the soil and run off into groundwater and (NO3 and PO4) can cause eutrophication.
Although soils are usually basic, what happens to mineral content when they’re acidic due to events like acid rain caused by pollution?
Become acidic so the negative charges on the soil now become positive and cations are easily leeched out of the soil solution.
Whats passive transport?
solutes move down a concentration or electrochemical gradient. They diffuse over a semi permable membrane or they are released through transport proteins.
Whats active transport?
Is moving against an electrochemical or concentration gradient (ex transport pumps)
What mechanism are there to increase substance uptake in plants?
Root hairs, mycorrhizae.
How do root hairs increase substance uptake in plants? What substances do they help uptake?
They Greatly increase root surface area, absorb water and minerals
How do mycorrhizae help substance uptake in plants, what substances?
Mychorizzae increases plants supply of phosphate and plant gives the mychorizzae carbon, fungus interacts with root to mobilize phosphate
Why is there membrane transports in root cells?
Because charge particles require a channel or transport- can’t just diffuse.
Why do we want to reduce nitrogen fertilization?
Want to reduce nitrogen fertilization as each molecule of nitrogen is 300x more potent than CO2.
What are the different ways plant transport material?
Into and out of cells, cell to cell, and over long distances such as root to shoot.
What are the two mechanisms used transporting material in plants?
Passive and active transport
How much water do plants move through their body, break down the percentages of what it’s used for?
Are able to move buckets of water, moves a hundred gallons of water, 90% of it is used in transpiration and 10% in metabolism
How do trees transport a hundred gallons of water?
Answer is in the wood of tree, There’s tube sin trunk that extend whole length of trunk, water gets filtered into xylem vessels which move up water, then move into branches and then leaves
How do stomata pores adjust to water content in the surrounding soil of a plant?
Stomata pore adjusts to increase/lack of water in soil that’s being pulled up through xylem in plant.
If the soil is dry a hormone is triggered that shuts down the stomata pore. The cells have to consistently adjust themselves to remain turgidity this way.
Whats short distance transport in plants?
minerals and water being transported across cell membranes.
Mineral and water being pulled into and out xylem and phloem
What’s long distance transport in plants?
Moving substances from root to shoot
Define osmosis
Passive movement of water across a selectively permeable membrane
Whats aquaporin?
A protein that allows quick movement of water through hydrophobic environments
Define water potential
Is the potential energy of water and is a driving force in the directionality of water. Water potential is measured in megapascals and is the sum of its components (pressure potential and solute potential)
What way does water move?
Water moves from High water potential to low water potential
What is the pressure of a turgor cell?
1 megapascal
What decreases water potential?
Anytime there’s a solute in the water, the water potential drops
What is pressure potential?
. Pressure potential is the force required to stop water movement.
When the pressure potential is positive/negative what happens to water potential?
Positive pressure increases water potential, negative pressure reduces water potential.
If the pressure potential is 0 is there any movement of water?
No
What maintains turgor pressure in plants?
Central vacuole’s tonoplast membrane
Does water potential control how the plants gets water from soil?
Yes for example water potential of dry soil is low which is why plants get plasmolyzed in dry soil as water moves down to soil.
If you increase solutes inside the cell what happens to turgor pressure?
It goes up because water rushes into the cell as the solute conc is high, this will increase the pressure potential resulting in a turgid cell.
Describe what happens to a cell when the outside of it has a very low water potential
Solute will rush into vacuole in order to avoid being plasmolyzed, this will then decrease the water potential of the vacuole/cell, water will rush in and increase the pressure potential so vacuole maintains turgidity and water will continue to rush in until equilibrium between outside and inside of the cell is the same.
When solutes enter cell, what comes first water or solute?
Water always follows solute!
What are the three pathways that help water and solutes go from root to the cells?
Apoplastic pathway- is outside of the cell, nothing gets into the cell and it’s a passive transport
Symplastic- Things are being transported into the cell, water flows from the cytoplasms via plasmodesmata.
Cell to cell movement.
What are plasmodesmatas?
The openings between cells are called plasmodesmatas- can have 20 to 50 connections within a single cell.
How does solute move in the apoplastic pathway?
Solute moves from cell wall to cell wall and travels in the apoplast, diffuses across spongy cell wall
How does solute move in symplastic pathway?
Symplast is cytosol and plasmodesmata (are channels in cell walls that connect cells together).
So if sugar was in a mesophyll cell, and it went down the symplastic route that means the sugar will travel through symplast only and travels through cells through channels. Don’t ever have to cross plasma membrane or cell wall. Is active transport for sugars but passive transport through osmosis for water.
WHat’s cell to cell movenemtn?
Solute travels from actual cells, not openings like plasmodesmata
What’s faster apoplast or symplastic?
Apoplastic is fastest route as solute doesn’t even enter cell and doesn’t have to through cytosol and organelles which are incredibly dense so take a long time to go through.
Cell to cell movement is slowest.
Whats the endodermis?
Is layer in root that sits and screens solute to filter only what plant needs into cell, anything absorbed must go through endodermis
Is the symplastic pathway or apoplastic pathway blocked by the endodermis (casparian strip) screening layer?
The apoplastic pathway, once things enter symplast there’s no need for screening by the endodermal layer
How are ions transported into the xylem?
They are actively transported as endodermal cells (casparian strip) only let certain ions pass through.
What’s the casparian strip?
Is in roots is also called the endodermal layer forces apoplastic water pathway to be converted into symplastic pathway before entering xylem by passing it through the plasma membrane
What is the casparian strip made of?
waxy cells
What another benefit of the casparian strip besides screening for ions
It stops solutes from leaking out back by being hydrophobic.
For long distance transport of water and minerals what does this?
Xylem- considered apoplastic route cause it’s not a cell.
What properties of water play a role in long distance transport of water and minerals?
Cohesion and tension, in trees the tallest ones have reached their growth limit because this mechanism has reached its own limit
What is transpiration?
Evaporation of water out of plants
Greater than water used in growth and metabolism
Describe how the cohesion-tension mechanism works?
This mechanism is driven by transpiration, water drive sup length of plant in order to transpire from the top of it, after a molecules of water evaporates than another water molecules replaces it immediately through cohesion (as water molecules are attracted to each other).
Evaporation exerts a negative pressure on the xylem (reduces pressure)- what happens to prevent the column from collapsing?
Lignin in secondary cell wall (xylem) is strong so holds up column, weight of column is heavy, and adhesive forces in xylem-water prevents it from collapsing.
How do leaves facilitate transpiration?
Large volume of air space provides surface area for evaporation
Stomata: Thousands to millions of stomata
Short cell distances to xylem: each square cm contains thousands of xylem veins
When the water evaporates what happens to xylem?
This transpirations also exerts tension on the xylem allowing it to stay up right as thin film of water is connect to xylem
How does root pressure aid bulk flow? Is it the main mechanism?
Positive pressure in roots forces xylem sap upwards and moves water up small distances. However you still need the main mechnaism of transpiration.
Define gluttation?
When root pressure strong enough to force water out of leaf openings
Water is pushed up and out of veins
Define translocation
Long-distance transport of substances via phloem, this substance is phloem sap and contains amino acids, organic acids, organic nitrogen compounds, hormones, and other signal molecules, is more than just sugar
What drives translocation?
Differences in pressure between the source and sink regions drive the flow. So where it’’s lower in pressure in plant is where phloem sap goes.
Define a source in a plant?
Any region of the plant where organic substances can be loaded into the phloem
ex: Sources- leaves as they put sugar into phloem
Define a sink in a plant?
:Any region of plant where organic substances are unloaded from phloem
Ex. sugars can get unloaded at roots which makes them sinks.
What sugar does phloem like transporting and not like transporting?
Phloem likes transporting sucrose- as it’s soluble, but not glucose.
What is phloem comprised of?
sieve tubes, companion cells, and sieve plates
How are sieve tubes, plates, and companion cells connected?
Sieve plates are on either side of sieve tube.
Every single sieve tube is connected to a companion cell
Describe how phloem transports sap
Phloem starts from a cell called phloem mother cell can go through a symmetric or asymmetric division.
If it’s symmetric division- the cell produced will have the same funcions
If assymetric- the cell produced can do two diff functions.
So after asymmetric division of phloem mother cell- the cells produced are the companion cell and sieve element
The images above show the cells, with all organelles, they cells are connected through plasmodesmata.
How do they transport sugar through all this clutter? The sieve tube go through partial cell death, clearing out organelles, take remaining organelles left after partial cell death and anchor them to the far ends of the cell.
How can phloem be alive at maturity if it has no nucelous? This is because the companion cell holds the organelles that the sieve element needs, the sieve tube needs to be alive to import apoplastic sugars.
What are the mechanism of sugar loading?
Both apoplastic and symplastic
Can sugar be transported only through the apoplast
No, substances have to eventually get into the symplast of the sieve tube to be transported.
Is moving sugar passive or active?
active, Because the concentration of sugar is high in the sieve tube, to load more into it it needs to be active transport
How does sucrose travel through companion cells and sieve tubes?
Sucrose comes through smaller plasmodesmata into companion cells, processed into larger sugars and through larger plasmodesmata transferred to sieve tube (as sucrose) and then into phloem.
What mechanism is used to move sugars to other parts of plant?
Pressure flow mechanism moves substances by bulk flow under pressure from sources to sinks
Based on water potential gradients
Load from source transport in sieve tube unload into sinks
How do xylem and sieve tubes work together in terms of bulk flow?
Water gets loaded into sieve tube source as solute level is high so low water potential, this increases the turgor pressure, water then travels down to sink which has a low turgor pressure and moves backwards into xylem to start the process over again.
How do leaves adapt to do gas exchange?
gas exchange is done by simple diffusion, to maximize this they put a short distance between cells and the external environment and create surface area through leaves
WHat role does stomata play in gas exchange?
does all of gas exchnage
What does a stomata consist of?
Two guard cells that surround a tiny pore called a stoma
Whats the disadvantage of stomata?
Disadvantage is same pore controls water loss and taking in gases
What’s the transpiration photosynthesis compromise?
Transpiration photosynthesis compromise- when stomata open you lose water good for transpiration but can cause excess loss of water and plants to wilt but stops photosynthesis, is a compromise do you wanna lose water or photosynthesize. Also cuticles reduce water loss but also limits co2 diffusion- again a compromise.
What is the stomatal opening/closing controlled by? (on exam)
stomatal opening and closing is actively controlled by potassium, water follows potassium being transported into or out of guard cells- if in the stomatas open- if out it’s closed
What is ABA? What does it do?
Abscisic acid, How do plants sense there’s not enough water in the soil, does this through abscisic acid that moves up xylem and signal stomata to close.
Mesophylls cells from root take ABA and release it to guard cells which open and close stomata
How does the stomatal opening and closing work?
Opening- Hydrogen ion gets pumped out to set a concentration gradient, Potassium ions flood into guard cells and as water follows solutes it gets pumped in after- this then causes the guard cell to open and pores to open as it becomes turgid
Closing- ABA triggers potassium to be released out by entering guard cells and water follows it, this softens the stomatal pores and the stomata closes.
How can phloem be alive at maturity if it has no nucelous?
This is because the companion cell holds the organelles that the sieve element needs, the sieve tube needs to be alive to import apoplastic sugars.
What organelles get killed off during partial cell death in sieve element cells?
nucleus, tonoplasts, rough er, ribosomes, cytoskeleton, and golgi
