1
Q
Similarities between Animal and plant cells
A
Plasma membrane, intracellualr organelles (nucelus mitochondria ER adn golgi) and they are all living
2
Q
What do plants have that animals dont
A
chloroplast to harvest and store light energy and a cell wall to allow exchange with environment and allow turgor pressure in plant cells
3
Q
IN plants how are they organized and connected
A
They are connected with roots and shoot by continuous vasculature.
4
Q
What are the three main tissue types in plants
A
dermal, vascular and ground
5
Q
In animals how are they organized and connected
A
multiple organ systems
6
Q
What are the four main tissue types of animals
A
epithelial, connective, muscle and nervous
7
Q
What is entropy and what offsets it
A
Disorder of an isolated system over time. ATP is metabolic source of energy that offsets entropy
8
Q
Where is ATP produced in plants and animals
A
animals: mitochondria. Animals use organic matter (plants or other animals)
Plants: Chloroplast uses and and produces ATP to store energy as sugars. Plants use sunlight
9
Q
What is Diffusion
A
Movement of substances across membrane of single cell organisms and individual cells. Diffusion is slow across long distances and rapid across short
10
Q
What is positive pressure
A
push
11
Q
Negative pressure?
A
pull
12
Q
Is phloem positive or negative
A
postivive push
13
Q
xylem positive or neg?
A
negative
14
Q
What is the cellular level environmental resposne
A
- Reception: Cell receptors sense external signal
- Transduction: phosphorylation cascade s and second messengers (Ca2+) translate signals into a chemical language that the cell understands
- Response: cell response involves DNA transcription/translation or activation/inactivation of pumps
15
Q
Why is animal different then cell response
A
Animals have complex sensory organs such as eyes and signal integration centre (brain) and endocrine and electrical signals to give fast response
16
Q
what type of response do plants have
A
cellular level as they don’t have signal integration centre and have. a systemic communication by hormonal (slow response)
17
Q
When energy is converted form one form to another what is inefficient
A
there is a loss of useful energy through heat
18
Q
why do organisms need nutrients
A
to obtain energy, obtain building blocks for developmental growth and repair and to combat entropy
19
Q
What is metabolism
A
sum of all chemical reactions in the body
20
Q
Catabolic reactions:
A
Highly ordered, complex molecules become simpler molecules. Carbohydrates, prtoien, lipids to glucose, amino acids and fatty acids
21
Q
Anabolic Reactions:
A
Highly ordered (low entropy) where simpler molecules (glucose, amino acids and fatty acids) are built into complex molecules( carbs proteins and lipids)
22
Q
What do both catabolic and anabolic reactions use
A
Catabolic uses ADP and P to make ATP.
Anabolic breaks down ATP to ADP and P
23
Q
Where in the cell does photosynthesis occur
A
chloroplast from mesophyll cells.
24
Q
Explain the layers of the mesophyll cell
A
the upper epidermis has transparent layer to allow light in to th emesophyll below. The stomata is in the lower leaf epidermis to control gas exchange and regulate water balance
25
What are the four main Nutirents
Carb, Protein, Fat and nucleic acids
26
27
Where in the chloroplast does the light dependent reaction occur
in the thylakoid memrbane. This is where light energy absorption occurs (ATP and NADPH is generated)
28
Where does the light independent reaction occur
In the stroma (space between the stacks). This is where calvin cycle occurs using teh ATP and NADPH for CO2 fixation and rubisco
29
What does chlorophyll A reflect
High energy blue waevelengths
30
WHat does Chlorophyll B refelct
green
31
what does carotenoids reflect
yellow
32
What is the function of Chlorophyll A
Main photosynthetic pigment that catalyzes the transfer of electrons to accept molecule (photochemistry)
33
Function of chlorophyll b
Accessory pigment that absorbs light at the wavelength poorly absorbed by chlorophyll a and transfers excitation energy to it
34
Carotenoid function
accessory pigment that absorbs wavelength poorly absorbed by a and transfers excitation energy to it. Redirects right to the reaction centre (chlorophyll a) and allows leaves to live longer to recycle nutrient in the winter (absorbs blue and green light)
35
What happens to chlorophyll in the fall
Chlorophyll breaks down revelaing other pigments to give yellow oragne colour. The pigment production increases
36
Explain the antenna complex
Pigments are organized here and the pigment molecules capture and direct energy form photons towards the reaction centre
The peripheral antenna is loosely packed and contains chlorophyll a.
The reaction centre is a modified chlorophyll dimer with the ability to transfer one excited electron to an acceptor
37
photochemistry
the light energy is transformed into chemical energy
38
Where does photochemistry get lost or transferred
At the reaction centre. The excited electron is transferred to an electron acceptor. When the electron acceptor is reduced the light energy is transformed to chemical energy
39
resonance
the excitation energy of the electron is transferred to an electron in a nearby pigment ***energy transferred no thte electron
40
What happens when electron is transferred by reaction centre
The reaction centre must be replenished. PSII gets electron from water splitting and the electron donor for reaction centre 1 is component of PSII
PSII get sunlight energy to split water to O2 and protons. The protons excite the electron carryign it to reaction centre 1. The antenna resonance energy transfers to pheophytin adn then to plastocyanin which carries it to reaction centre 1 in PSI wehre the antenna resonance energy carreis to ferredoxin
41
How is the energy of the electron released
Pigment energy of the photons are absorbed and used to excite electrons. The ehat of excited electron is released as heat fluorescence, energy transfer (resonance) and photochemistry.
Heat fluorescence is useless in isolated pigments
42
Explain Z scheme
The linear scheme of photosynthesis that produces ATP and NADPH.
In light dependent PSII and PSI work together to move electron from water to form the NADPH and ATP
NADP reductase is the only possible exit point for electrons. H2O is the only possible entry point for electrons
The # of electrons entering system = # electrons exiting the system
Plastoquinone only works it it moves electrons and protons
ELectrons move higher to lower energy
43
Explain the steps of the Z scheme
Photon energy is absorbed and moved across the pigments, splitting water to make protons and oxygen. The proton release gives electrons to the PSII where the photons can excite the electrons at the reaction centre. The reaction centre gives the excited electron to pheophytin where PQ carries this down the ETC to the cytochrome complex and to PC. All fo this in ETC releasign ATP. The PC carries the ... to PSI reaction centre where the electron is again excited and carried to the ETC adn to ferredoxin where NADP reductase forms NADPH.
44
IN ETC explain
The movement of PQ across the thylakoid membrane created H+ gradient. When photons reach reaction centre of PSII high energy electrons of reaction centre are donated to pheophytin to plastoquinone PQ adn enter the ETC.
PQ shuttles an electron and proton across thylakoid memrbane (stroma to lumen) and the proton goes to the lumen, elextron reaches cyytochrome complex
ATP syntahse then makes ATP powered by the gradient
Cytochrome c complex transfers the electron to plastocyanin which links PSII to PSI
45
What happens if there is any inhibition of PQ, Water splitting, sytnheissi of NADPH)
then electron flow will stop and everything stops
46
WHat happens if translocation of pQ stops
fluorescence will icnrease beacuse instead o fenergy being released as photoenergy it is realeased as fluorescence which is less wanted
47
Explain cyclic electron flow
Electron is transferred from ferredoxin in PSI back to PQ in PSII only producign ATP nto NADPH
48
DOes water splititng occur in cyclic
no, ATP is produced without adding electrons to the system. Produces half the amount of ATP and no NADPH, the extra ATP is obtained without O2 rpoduciton but prevents RubisCO
49
First step of Calvin Cycle
1. Carbon Fixation (RubisCO): six molecules of CO2 (6C) reacts with six molecules substrate Ribulose 1-5 bi-phosphate (RuBP) (5C to make 30C) to produce 12 molecules of (3-PGA) (36C)
50
Second Step Calvin cycle
Reduction: 12 molecules 3-PGA (36C) are reduced using ATP and NADPH from the ligh dependent reaction to generate 12 molecules of G3P (36C). The 12 molecule sof G3P can go to make 1 molecule of glucose (2 molecules G3P 6C make one 6C) or the other 10 go to G3P (30C) to regenerate the substrate for recycling
51
3rd step calvin
SUbstrate regeneration: the 10 molecuels fo G3P (30C) use 6 additional ATP molecules to form light dependent reaction to regenerate 6 m0lecules of ribulose 30C.
52
What can RubisCO do
catalyzes two reactions.
1. Carboxylation: C3 Carbon fixation when CO2 is bound to RUbisCO in the energy of ATP and the reductive power of NADPH are used to create high energy C-C bonds
2. Photorespiration: when O2 is bound to RubisCO the energy of ATP and reductive power of NADPH are waster breaking C-C bonds and generating CO2 and heat waste of ATP and NADPH to heat loss
53
How do C3 plants deal with poor C fixing catalyst
they synthesize lots of the enzyme
54
How do CAM and C4 plants deal with poor C-fixing catalyst
prevent photorespiration by seperating rubisCO from oxygen. the trapping and release occur in different cells (mesophyll and bundle sheath)
55
explain C4 metabolism
CO2 i scaptured in mesohpyll cells and reacts with C3 compount PEP. The reaction produces Malate that is carreid between cells (CO2 is trapped and travels to another cell) and then CO2 is delivered to bundle sheath and the C3 PEP is regenerated
56
CAM metabolism
IN the night CO2 is captured accumating as a C4 compound (mesophyll cell vacuole) and in the Day CO2 is released and C3 regeneration in the same cell (mesophyll cell cytosl)
57
why do plants need water
cool down leaf surface through transpiration to help RubisCO. Serve as medium for biochemcial reaction (splitting), facilitate cell growth by generating high turgor pressure, source of protons adn electrons for syntehsizing carbs and does not need water to distribute sugars and minerals using transpiration
58
what is an essential nutrient
absolutely required for normal growth and reproduction of a palnt. the element is specific and cannot be replaces, if removed there will be no growth.
59
WHat are the macronutirents
Nitrogen, phosphorous, potassium, calcium, magnesium and sulfur
60
What are macronutrients used for
they are building blocks of plant biomass (carbs, lipids, proteins, nucleic acids).
61
what does N, P and S get used for
create building blocks
62
hat does potassium get used for
maintain osmotic potential
63
what is magnesium used for
capture light (found in chlorophyll)
64
calcium used for
maintain integrity of memrbanes
65
WHat do micronutirents form soil do
used as co-factors in enzymes and pigments, important roles in redox reactions and usually toxic in high concentrations.
66
What is in top soil
Horizon O: humus (organic material and macronutrients)
Horizon A: organic matter and leached minerals. Source of macro and micro nutrients
67
Subsoil
Horizon B: mineral precipitates. Source of micronutirents
68
what is horizon C
weathered rock
69
What are the topsoil quality parameters
Composition: presence of macro and micro nutrients.
- Organic composition: humus is rich in organic matter (macro)
-Inorganic: parent rocks with different mineral and pH content micronutrient
Texture: root penetration, water availability and oxygen availability
- Too loose will cause loss of water. If roots are alive respiration occurs. Needs oxygen, water and nutrients and air pockets for oxygen
- The particle size and chemcial properties of inorganic layer determine availability fo water, nutrient and oxygen.
Charge: Mobility and bioavailability of cationic and anionic nutrients
- mobility and bioavailability of cationic and anionic nutrients.
70
If there is less water in soil what happens to the roots
the roots grow to reach nutrients
71
what happens to roots in sandy soil
rools grow as there is mroe drainage of water and nutrients
72
what is the charge of clay and organic soil
organic soil and clay are negative, The positive ions (K+ and Ca 2+) are not available for uptake bny roots as they bind to the clay or organic particle. Teh negative ions (Cl-) are available for uptake
73
What happens to cation availability in low pH soil
The cations increase their bioavailability in acidic soil.
This is because the H+ ions adhere to the negatively charged soil than the mineral cations (Ca 2+). The H+ ions that take the place of the mineral cations on the soil particles, leave the compounds in solution where they can be taken up by the plant roots or leached due to rain
74
where do the protons come from to displace th cations on soil
the root hairs give H+ to repalce the ions attached to soil particles to allow release of ions for take up by root hairs.
1. the root hairs exude H+ directly into soil suing H+ ATPases which requires energy
2. the root hairs produce H+ indirectly as a consequence of cell resp (spontaneous)
75
What is the Liebig law of minimum
nutrient limitation. Growth is controlled by the limiting factor and resource availability. It is what gets depleted first not what is least abundant
76
what is eutrophication
something aout fertilizign entire ecosystem
77
what do lateral roots do
anchor the plant and enables long idstance scouting for water and minerals in soil
78
what do root hairs do
increase surface area of the root enhancing short distance mineral and water uptake. when roots find nutrients it forms root hairs to catch nutrients
79
what happens to root hair sin nutrient poor soil
grow long and dense root hairs (20-30 fold) to increase surface area to compensate for low nutreint availability. The root hairs plasma membrane contains many sleective ion channels and high affinity ion transporters that take nutreitns and filter out toxins
80
explain apoplastic route
water flows through the extracellular spaces and bypasses the plasma membrane (no filtering and ends in the endodermis (filtering)
Its fast and goes around cells and ends with filtering with symplastic.
81
Casparian strip.. what does it do
iN the apoplastic route it stops at casparian strip makign it go through the memrbane. It has a hydrophobic barrier in the cell wall that stops water passage and reroutes the water to symplastic route. This is to filter out toxins (detoxificaiton)
82
Symplastic route
water crosses the root hair plasma memrbane, filtering, and moves to cell using plasmodomestamata (channel between plant cells that water can mpove through) and ends in the vasculature
83
what happens if too high toxin concentration from root hairs
it can make it through the channels and enter the vasculature otherwise the casparian strip will block them
84
if a gene involved in biosynthesis of the casparian strip what would happen to the cellular accumulation of toxic cations in the leaf cells?
It would increase rapidly if the stomata are open
Why you must say if stomata are open is because open stomata causes loss of water by transpiration which means the plant will uptake water but won't be able to filter causing accumulation of toxin. If it's closed it will be a slower process.
85
what gradients control movement of nutrients across plant cell membranes
chemical and electrical
86
what is chemical gradient
movoement from high to low concentration
87
what is electrical gradient
opposite charges attract. Across membrane is measured as voltage
88
which side of memrbane is negative and positive
intracellular space of membrane is more negative than extracellular.
89
what modifies the electrochmecial potential of the cell
the proton gradient. Creating proton gradient requries metabolic energy (ATP). The proton pump creates a proton conentration across the plasma memrbane and the pumps increase electrical gradeint across the plasma memrbane. The charging pushes the protons across the gradeint causign the inside to bevcome more positive and the outside to beocme more negative causing electrical gradient.
90
What way does nutrient acquision go in roots
root hairs always against concentration gradient. Nutrient moves soil to root against concentration to generate proton gradient. The root hairs store the energy as proton gradient to facilitate nutreint acquision
91
Channels?
regualte passive transport (spontaneous) in favor fo the electrochemical potential
92
transporters?
regualte active transport (no spontaneous) against the electrochemcial potential.
93
How do cations enter root hairs
enter root hairs in favour of the electrical gradient and against concentration gradient. To transport positive charges, proton pumps generate an electrical gradient that is strong enough to overcome the unfavourable concentration gradient
94
How do anions enter the cell
Enter cell against concentration and electrical gradient
TO transport the co-transporters use the proton gradient to obtain energy and overcome unfavourable electrical and concentration gradient.
1. Protons are pumped out and generate an electrical potential
2. Protons now have strong tendency to return to cell in favour of electrochemcial potential
3. anions use the nergy accumulated by the proton gradient to hitchhike wiht them inside the cell
95
what mecahnisms prevent excess uptake of toxic coumpounds in plants
passive exclusion:
Active exclusion and sequestration into vacuoles:
binding and detoxification
96
passive exclusion?
there are no membrane transporters/channels to facilitate transport
- Toxic compounds can still enter cell using ion channels with low selectivity
- prevents transport of toxins across the plasma membrane in root hairs (symplastic route) and endodermis/casparian strip (apoplastic)
97
sequestration into vacuoles?
Plants store harmful ions in the central vacuole or transport them to the extracellular media.
The vacuole is delimited by a lipid membrane named tonoplast
The vacuole isolates the toxic compounds from the cytosol
AN H+/Na+ antiporter leads to accumulation of Na+ inside the vacuole
During detoxification, Na+ crosses the tonoplast (vacuolar membrane) against a concentration and a chemical gradient
Protons are pumped into the vacuole to create a proton gradient. This proton gradient is exploited to drive transport of Na+ into the vacuole (antiport)
98
Binding/detoxification?
Alternative to storage in the vacuoles Metallothioneins
These are cystein (S-based) proteins with high affinity for metals that are localized in the cytosol
Metals get trapped in the protein that is then loaded into secretory vesicles and exported out of the cells (exocytosis)
99
Mutualism?
involves exchange of goods or services between two species. Each species involved in mutualism must receive a benefit from the interaction and the benefit usually comes with a cost
100
Myzcorrhizae (fungi)? what is the flow, what does it do
bidirection flow of nutrients. FUngus delivers inorganic nutrients to the plant and plant delivers fixed organic carbon to fungus. The plant will become nutreint deficient once it uses up nutrients in soil whereaase one with fungi can keep gettinng nutreints provided
101
N2 fixing bacteria?
N2 is abundant but it has a storm triple bond that is difficult to break making it not available to plants. The bacteria (N-fixers) evolved to fix N2 into ammonium that the plant can readily take up from soil
N2 fixation is catalyzed by Nitrogenase that needs to get separated from O2 (breaking N2 is also energetically costly)
The enzyme is poisoned by oxygen
SO: the symbiosis with N2 fixing bacteria occurs in legume nodules which are rood nodules on roots of plants that associate with the symbiotic nitrogen fixing bacteria (Rhizobia)
The plant convert N2 to NH4+ and makes it available to the plant in exhchnage for energy
The plant gives sugar and hemoglobin to bacteria. The hemoglobin takes the oxygen to allow the bacteria to work.
102
how is oxygen taken up in the nodules
Leghemoglobin is an oxygen binding protein produced in legumes in response to infection by N2-fixing bacteria
Buffers the concentration of free oxygen in the cytoplasm of the infected root cells preventing the inactivation of the bacterial Nitrogenase enzyme
The Nitrogenase enzyme converts N2 to NH4+ and the N2 fixing bacteria makes it available to the plant in exchange for sugar
103
AT the end of inspiration what is the composition of gas at the bronchus compared to air
similar O2 and CO2 levels
104
What is the composition of air in the alveoli after exchage occurs in comaprison to air
more CO2 and lower Oxygen than air
105
WHat is VD
the anatomical dead space (trachea, bronchi and bronchioles) not involved in gas exchange
106
what is wrong with dead space
makes lungs inefficient as when we breath we take some stale air that is trapped in airway. The volume of fresh air that reaches alveoli is tidal (volume air going in and out) minus the dead space volume
107
what is FRC
functional residual capacity, volume of air left in the lyngs after a normal quiet exhalation
108
explain fish heart circuit circulatory system. What type is it
Single circuit (linear)
109
what are th two chambers of the fish heart
atrium: which transfers blood to ventricles. Atrium is thin and weakly contracts because blood passively trickles from veins. Very little contraction at end pushes last bit of blood
Ventricle: pushes blood out of the heart. There are many blood vessels, so high resistance, so more push needed meaning more muscles and thicker walls. The contraction increases pressure to push it to lower pressure elsewhere
110
What are the two steps of cardiac cycle
1. systole: contraction, pressure increases
2. Diastole: relaxation, pressure decreases
111
what insures unidirectional flow
valves
112
where are the valves in fish heart
entrance of atrium, between atrium adn ventricle and exit of ventricle
113
what is flow of blood in fish
veins, atrium, ventricle, artery
114
what is the cardiac cycle of a mammal
1. ventricular diastole (valves to arteries closed --> all valves closed)
2. ventricular diastole (valves from atria open) blood trickle passively form atria to ventricle but no atria contraction
3. atrial systole (valves from atria open
4. ventricular systole (all valves closed)
5. ventricular systole (valves to arteries open)
115
what is the pathway of blood in mammal
veins to atrium to ventricle to artery
116
how does no backflow occur
unidirectional valves, and open or close passively in response to pressure
117
what blood does left heart deal with
oxygenated
118
what blood does right heart deal with
deoxygentated
119
which direction is arteries and veins
arteries away
veins return
120
compare left and right side of the heart
left side contracts more forcefully, has more muscular wall, because it pushes with greater force to aorta and pressure generated is greater. This is because it supplies blood to systemic circulation--> all organs and tissues in the body.
RV pushes blood to the pumponary circulation taht supplies blood ot the lungs alveoli
121
compare systemic to pulmonary
systemic has longer and more tubes than pulmonary so it has more resistance. The LV also fight sagainst gracity to bring blood back into th eheart
122
How are cardiac cells connected
by gap junctions at a structure called the intracalated disk to allow electrical signals to travel from cell to cell
123
hwo does contraction occur in rhythm
atria together, ventricles togeteher, atria before ventricle sand ventricles contract apex tupward to go agaisnt gravity
124
What are the steps of electrical signals through the heart
Directly from cell to cell
Via specialized conducting pathways→ specialized cardiac muscle cells that have lost their ability to contract and conduct the electrical signal very fast
Step 1: Impulse conduction→ electrical signal generated at SA node
Step 2 a: The electrical signal goes rapidly to the AV node via internodal pathways
The cells from atria are not connected via gap junctions to the cells of the ventricles
The only connection from atria to ventricles is through the AV nodes and the bundle of HIs
The AV node delay the electrical signal so that all the atrial cells are contracting before ventricular cells start their contraction
Step 2 B: The electrical signal spreads more slowly across the atria (from cells to cells via their gap junction) cells contact
Meanwhile the AV node delays the signal from being passed onto the ventricle making sure all atrial cells have contracted
Step 3: the electrical signal moves very rapidly through the ventricular conducting pathway to reach the tip or apex of the heart
At the apex, the electrical signal will be passed to ventricular cells and then spread on to other ventricular cells via gap junctions
Step 4: The electrical signal spreads upward from the apex. The ventricular cells at the apex start contracting and the contraction spread upward squeezing the blood into the arteries opening at the top of the ventricles
125
explain relation of Q to blood vessels
flow rate does not change, btu the speed does in relation to cross section. Blood therefore moves slow through capillaries to allow time for substances to be exchanged
126
pressure change in arteries compared to left ventricle
Pressure change in the arteries is much smaller than the left ventricle
The aorta acts as a pressure reservoir
Big arteries have thick, muscular and eleastic walsl to withstand high pressure→ their walls are stretchy
During Systole:
More blood enters the aorta than leaves the aorta so pressure rises
Some of the blood is stored in the aorta and the aorta expands like a balloon
During Diastole:
No more blood enters aorta
The elastic recoil of the walsl causes the aorta to release the stored blood into circulation
The blood continues to flow through the arteriens, arterioles, capillaries and veins→ pressure drops slowly
The next beat increases the aortic pressure
127
WHen flow reaches branches what happens
the fluid will take path of least resistance so they resistance is equal so flow is distributed equalyy. FLow is alwyas the same, if radius of one pathway is different then it will get less than the rest.
128
what of the arterioles regualtes flow
vasoconstriction adn vasodilation
129
How do plants prevent water loss thorugh open stomata
stomata are located on the leaf underside (abaxial side) reducing temp in the abaxial side to prevent water loss
Protecting and hiding stomatal pores: create invaginations (crypts) in the epidermal layer to shield stomata from wind and using trichomes (little hairs) to allow moisture to build up, increasing humidity near stomata and reduce water loss
Creating hydrohphobic barriers: thick cuticle and increase wax depositno on leaves and stem surfaces to protect plants from water loss
Improve water efficiency during the day (C4 carbon concentration mecahnisM) where there is mesophyll cell and bundle sheath cell
Opening stomata at night: desert species open during night to reduce transpiration. Thsi CO@ is stored as organic acid as there is no photosynthesis at night. The organic acid breaks down releasing CO2 during the day. Photosynthesis takes place during the day with closed stomata hence minimizing water loss
130
DUring the sumemr where does the phloem go
down
131
Which direction does xylem go
roots to shoots
131
during the winter which direction does the phloem go
up (roots to shoots)
132
WHat does xylem carry
water nad minerals
133
what does phloem carry
water and sugars
134
How are xylem and phloem connected
Water is laoded into the xylem but the close association of xylem an dphloem allows transfer of water by osmosis between them. XYlem and Phloem form vascular bundles which are the water and nutrient conducting system
135
What determines water movement in plants
water potential which is the potential energy of water relative to potential energy of pure water, represented as pressure MPa
Quantifies tendency of waterto move from one area to another due to osmosis, mechanical pressure adn additional factors
136
what are the components of water potential
solute potential and pressure potential, solute potential is always negative
137
How are animals and plants different in how they determine flow of water
animals are open circuits that change volume until solute concentration reaches equilibrium where solute potential determines flow of water, there is no pressure potential. The hypotonic solution animal cells expand so they cannot build pressure.
IN plants the water potential determiens flow of water (closed circuit) they have thick walls that cant expand so they have to build pressure. The pressure potential (turgor pressure) is the tendancy of water to move in response to physical pressure (push or pull.
**water potential can be positive, zero or negative
138
Explain water potential in terms of what it determines
plants move water not by solute potentia lor pressure potential alone, it is by lowest water potential which is additoinof the always negtive solute potential and the positive, zero or negative pressure potential
139
Plant cells are closed circuits that develop pressure potential (turgor pressure) in response to osmosis
Osmosis pushed water inside the cell. Turgor pressure pushes water out
Loss of water (turgor pressure) leads to flaccid cells and wilting of plants
A plant cell develops pressure potential (turgor pressure) until the external and internal potentials are equal
Under these conditions there is no flow in or out of the cell as its at equilibrium
140
what is water potential when atmosphere is at 100% humidity (fog)
the water potential is zero because there is no dirving force for transpiration, and if this presis
141
what happens if 100% humidity persisits
plant become dwarfs as mineral transport is impaired
142
What direction of water potential does water flow up xylem
from least negative to most negative
143
what determines transpiration rates
when humidity is low, max transpiration occurs. Transpiration also occurs if stromata are open
144
how does evaporation occur
atmosphere evaporates water form leaf mesophyll cell genearting tension (negative pressure) which pulls xylem sap upwards. The negative pressure is transmitted to xylem column by cohesion and they move up due to cohesion force of H-bonds
145
How does xylem prevent vascular collapse due to negative pressure contraction
xylem clels have a thick lignified secondary cell wall compared to the cortex cells which are thin
146
WHat is embolism and how does it get fixed
the negative pressure in xylem causes embolism where the atmospheric pull outpaces water availability causing air to be pulled and air bubbles to form
to counteract this there are vessels that transport alrge amounts of water but can suffer embolksim adn then tracheids tranposrt smal amount fo water but is not affected by embolism as it has pits
147
what are pits
pits are a collection of dead cells that collect air bubbles and redirect the water flow. This enables loading of water and minerals from root cells usign difference of pressure to cross the pits.
148
In conifers what are xylem pits covered by
a water-permeable membrane called torus which filter out small particles
149
What is the first physical force that brings water and minerals up roots to xylem
The positive root pressure loads the xylem. AS high solute (mineral concentration in root cells) is higher than soil generating a negative water potential for uptake. This generates turgor pressure in root cells that push water and minerals towards xylem and up stem
150
How far can positive pressure from soil lift xylem sap
around 30cm, as it pulls till it hits equilibrium fo root pressure adn weigth of water column
151
what happens to plants smaller than 30cm
in these plants root pressure builds up during night inducing guttation, which is turgor pressure builds without transpiration (closed stomata).
152
what is guttation
the dew drops secretion resutls from positive root pressure pushing xylem sap out of the leaf surfaces and through specialized pressure valves called hydathodes
Somato not open, root pressure pulls in, pressure increases and xylem flows out
153
WHat is the second physical factor of water uptake
water rises because pward adhesive force between water and walls is larger than downward weight of water column
154
what is the height of water column inversely proportional to
the radius. In a wide tube a smaller amount of water contributes to upward adhesive force, and a narrow tube more does.
155
How high does adhesion take it
around 1.5-2m
156
what is the third physcial factor to pull water up
cohesion of water transport by transpiration
157
explain cohesion
the negeative of the atmosphere casues water to evaporate through stoamta. The evaporated ater is replaced by inner cells which generates negative pressure (tension_) to pull water column toward leaves. Water cohesion transmits the tension from leaf xylem to root. The water is laoded by roots by negative pressure (tension) and postive root pressure (osmosis)
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how high does cohesion take it
aorun 150cm or to height of tree
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what are xylem transport key cocnepts
Differences in water potential between atmosphere and the leaf intercellular space creates the negative pressure that pulls the xylem sap through a large tree
Other factors such as capillarity and positive root pressure, contribute significantly for the movement of xylem sap in smaller plants (e.g. guttation)
Water movement in plants requires no energy input from the plant
160
what is a source and sink
source is what provides sugars, and sink is the organ that needs or stores sugars
160
what are sieve cells
sugar conducting cell that lacks nucleus and major organelles making it metabolically inactive
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Where does phloem carry sugars and waters
from source to sink
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what are companion cells
sugar loading and unloading cell that has nucleus and major organelles making it metavbolically acitve (has visible mitochondria)
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what are the stpes of phloem sao
163
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how is sucrose transported
sucrose is passively transported followign the concentration gradient.
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Phloem unloading in storage sinks
in storage cells sucrose accumulates in the cell vacuole and will be used as an energy reserve
sucrose is actively transported to the vacuole to maintain facorable concentration gradient for uptake from companion cells
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