second midterm Flashcards
Go back and add flashcards from the last chapter of mineral nutrients and the first part of solute transport
deal. will do
What form is Fe usually found / used? in
Fe3+, iron is largely oxidized and insoluble
What is interveinal chlorosis?
the characteristic symptom of iron deficiency
What is chelation?
the formation of bonds between two or more seperate binding sites within a ligand and a single central atom
- a central metal atom attactched to a ligand in a cyclic structure
What is the tonoplast?
the membrane of the central vacuole
Define chemical potential
The energy (ability) of a substance to perform (move) freely work
- the sum of the concentration, electrical and hydristatic potentials under standard conditions
specific definition of diffusion?
movement of molecules from a region of high concentration or high chemical potential to an area of low concentration or low chemical potential
What is facilitated diffusion?
- involves the movement of specific molecule / ions
- needs specific channels or carrier proteins
- does not use ATP for transport - it is passive transport
Which requires a greater gibbs free energy, simple or facilitated diffusion?
simple diffusion is less efficient because the membrane acts as a barrier and kinda slows it down
- facilitated diffusion is more efficent - has a lower gibbs free energy
When does simple diffusion overtake facilitated diffusion?
facilitated diffusion has a much higher rate of transport at low concentrations - but will plateau at some point when all membrane transporters / membrane proteins are fully saturated at the high concentration. As long as the area or concentration gradient does not change simple diffusion will eventually overtake facilitated diffusion in transport rate
How does diffusion continue once the solute has reached an equilibirum on either side of the membrane?
for example, metabolic consumption of glucose will lower the concentration of glucose on one side of the membrane - then the concentration gradient will be restablished - like that one chem thing of removing a reagent to push the equilibirum forward
- facilitated diffusion will continue
Two examples of passive transporters in plants
Plastid glucose transporter in the chloroplast inner envelope
triose phosphate translocator in the stoma - mediates a passive counter exchange of Pi and triose phosphate
Explain facilitated diffusion of charged species, ex) KCl
If you have K+ and Cl- ions on one side of the membrane, and a K+ transporter, then K+ will move to the other side of the membrane. Diffusion gradient will move K+ across, chemical potential gradient will go across, electrochemical potential gradient will go across, electrical gradient will go back the other way -this system will be in equilibrium even tho the concentrations arent equal
explain the difference between an ATPase, symporter, and anitporter
ATPase - is a proton pumping transporter that uses ATP for power
Symporter - couples with ATPase to transport two different ions in the same direction
Antiporter - couples with ATPase to transport two different ions in different directions
Which three mineral elements are transported by symporters?
NO3-, Pi (PHT1), and K (HAK)
Which directions do proton pumps usually move protons?
usually pump protons outside of the cell
Which side of the plasma membrane is more acidic - based on the gradient generated by proton pumps
outside of the cell is more acidic - because
in the current voltage relationship curve, which values are represented by the axis?
y axis = flux - positive = efflux, negative = influx
x axis = current in mV
What is the relationship between stomatal aperture and the presence of photosynthetically active radiation?
stomatal aperture increases - meaning the stomata open wider - when photosynthetically active light is present
the two are highly correlated and coincides with time of day.
How do guard cells respond to blue light?
blue light causes dramatically increased stomatal opening
- stimulated HATPase
you need to come back and look at these slides plz n thanks
yes forsolute transport 3`
Why is xylem(?) and phloem considered a non circulatory vascular system?
- xylem transports from root to shoot - in one direction
- phloem translocates from source to sink - meaning it will move sugars produced by photosynthesis from a source leaf either up into the vegetative meristem or down to the root meristem
What is the pathway for guard cell opening?
Blue light triggers HATPase - pumps H out of guard cells - causes K and Cl to accumulate - lowers solute potential - lowers water potential - water uptake into cells - guard cell becomes turgid and the stomata opens
- blue light also triggers starch degradation and malate synthesis - increases level of sucrose and malate - accumulates sucrose and malate which also lowers solute potential
What is the pathway for guard cell closing?
ABA accumulation triggers sucrose to starch conversion - also stops HATPase - opens outward K and Cl channels - sucrose and malate levels decrease - solute potential increases (less solute), water potential increases - water leaves via osmosis - the guard cells become flaccid and close
What is source tissue and what is sink tissue?
source tissue - exporting plant tissues or organs that produces photosynthate - sugars - a mature photosynthetically active leaf
sink tissue - non photosynthetic developing organ or an organ that does not produce a significant amount of photosynthate
How are sources and sinks related to tissue maturity?
phloem will move sugars from source to sink, or mature tissue to immature tissue - will move from an older leaf to a younger leaf - some leaves are in the middle and represent a source - sink transition leaf
What are the two strong sinks in a plant>
vegetative meristem and root meristem - both are young immature tissue and are not differentiated
within one leaf - which area is more mature and therefore a source and which area is less mature and therefore a sink?
the leaf tip is more mature / differentiated and therefore is a source - the leaf base is immature and therefore a sink
what is the functional unit of phloem?
sieve tubes - functional units for long distance translocation of plant materials - consists of stacked sieve elementsW
What is the sieve plate?
perforated wall between sieve elements and maybe also companion cells?
What are four key structures contained in a sieve element?
- structural phloem specific P-proteins
- endoplasmic reticulum
- mitochondria
- sieve element plastids
Which phloem structure contains a nucleus, vacuole and chloroplasts?
companion cells
What do P-proteins do in sieve elements?
seals off damaged sieve elements by plugging up sieve plate pores
- is a quick plant response and represents a short term solution
What does callose do in the sieve element?
seals off damaged sieve elements by plugging up sieve pores
- is a slower plant response but represents a long term solution
Two types of sucrose loading models in minor veins?
Symplasmic loading model - sugar moves through plasmodesmata from the mesophyll cells to the phloem
Apoplasmic sucrose loading model - sucrose will move on the outside of plant cells (bundle shealth cell or phloem parenchyma cell) into companion cells - happens via passive transport out of the cell via a permease - and then moves into companion cells by active transport via a sucrose symporter
Can all sugars move through phloem?
no, some “reducing” sugars are too reactive to be transported through the phloem
Which sugars will be able to move through the phloem?
non reducing - or less reactive sugars can be transported - sucrose
Which sugars cannot move through the phloem and why?
sugars with reactive groups like aldehydes and ketones are too reactive - glucose, mannose, fructose
How do plants get around moving reactive sugars through the phloem?
will bind other sugars to sucrose or as sugar alcohols
transport as sucrose, raffinose, stachyose, and verbascose
What is being loaded and translocated in phloem?
-water
- photosynthate (sugars in specific forms)
- specific amino acids
- ions (K+ and Mg2+
- metabolites
- hormones (auxin, gibberellic acid)
- proteins (signaling and sieve element maintenance)
- RNA (information macromolecules)
