BIO exam; right version


Terms in this set (...)

Light the drives photosynthesis
red and blue light
antenna complex
when photons strike this, the photon energy is trnasferred to large protein molecules; the proteins undergo brief shape change in order to breifly store the energy in their electron orbitals; eventually the electron jumps to an electron acceptor that can hold the energy stably; some of the energy causes shape changes of the acceptor and nearby molecules; this is the way to store energy so that it can be used later to make sugar molecules and ATP
Chloroplast thykaloid membranes
this is where energy and electron transfer occurs
photon energy
it is donated to the antenna comples chlorophyll molecules
this is the electron acceptor of the excited electron that results from the photon striking the antenna complex
cytochrome complex
this is where the energy from the movement of an excited electron jumping from donor to acceptor eventually piles up
these are proteins that have iron-heme structures which bind extra electrons easily
Concentration gradient of H+
the shape changes of all of the proteins causes protons to be transported from one side of the thykaloid membrane to the other; this energy-requiring active transport creates a large "blank" across the membrane; these then bind to and move through a very complex protein aggregate that makes ATP from ADP and phosphate ions
The energy that is put into the ATP
the energy that is put into the "blank" comes from the energy of the proton gradient trying to equilibriate
The energy that creates the gradient
the energy that creates the "blank" comes from the movement of protons into the pheophytin and cytochrome protein complexes and then out the other side into the middle space of the thykaloid
the energy which makes the proteins move
the energy that makes the "blanks" move comes from the light photons that excited the electrons to give their energy to the proteins which bind and release protons
Electrons that travel through the cytochrome complex
Electrons that travel through the "blank" lose almost all of their extra energy they gained from the photons in photosystem 2; but they enter electron acceptor molecules in photosystem 1 and the cycle repeats
2 molecules of NADPH from 2 molecules of NADP and 2 protons
the cycle of photons exciting electrons and energy being transferred through photosystems 1 and 2 repeats until their is enough energy to make 2 molecule of "blank" from 2 molecules of "blank" and 2 "blanks"
The calvin cycle
the "blank" is the cycle that uses the NADPH in reactions to make sugar from carbon dioxide
The enzyme ribulose bis-phosphate
the enzyme "blank" is the enzyme that carries out the reaction during the calvin cycle
The first step of the calvin cycle
the "blank" step of the calvin cycle includes the ribulose bisphosphate five carbon sugar molecule, and also 1 molecule of CO2 that is added covalently to the 5-carbon sugar and then broken down into two 3-carbon sugars
the second step of the calvin cycle
the "blank" step of the calvin cycle is where ATP energy is used to help the reduction of the 3-phosphoglycerate (3 carbon sugar) to glyceraldehyde-3-phosphate. NADPH produced during photosynthesis donates the electrons that reduce the carbon atoms of 3-PG to produce G-3-P
end of first set of notes
start of plant diversity
innovations that allow plants to adapt to life on land: for gathering water
spore, seed
innovations that allow plants to adapt to life on land: for protecting gametes and offspring
innovations that allow plants to adapt to life on land: for improving reproduction rate
water impermeable surface layers like cuticle, stomata (pores on leaves), to regulate water loss
innovations that allow plants to adapt to life on land: for saving water inside the plant
innovations that allow plants to adapt to life on land: vascular tissue to gather water and nutrients from a distance
xylem, phloem
innovations that allow plants to adapt to life on land: vascular tissue to help move water and nutrients around in the plant
"blank" is the aquatic species most closely related to land plants; hint: its an aquatic stonewart
"blank" are non-vascular plants that dont have tubes for transport of materials through the plant tissues
reprduction in aquatic species
reproduction in "blank" species (chara is last plant species to do this simple kind of reproduction): only the zigote is diploid, all other forms of the plant are haploid; the diploid zygot undergoes meiosis to form haploid spores that form an adult; male and female gametes are formed in haploid tissues know as gametangia;
"blank" are the simple cell aggregates that are the ancestors of the gametophytes of terrestrial plants
Alternation of generation
"blank of blank" refers to the type of reproduction that goes from gametophyte (haploid )to sporophyte (diploid) to gametophyte (haploid )and so on
All terrestrial plants
all "blank" plants carry out reproduction by producing two distinct multicellular structures that produce the male or female gametes
Process of alternation of generation
the process of "blank" refers to the process by which haploid gametes (eggs and sperm) are released from two separate, distinct gametophytes (one male, one female). One male and one female gamete form a diploid zygote which then develops into the alternate form of the same plant, the sporophyte.
to produce more gametophytes so reproduction can continue
the sporophytes job is to "blank"
The gametophyte
the "blank" protects the gametes from dessication in terrestrial environments
Aquatic plants
"blank" plants generally dont have gametophytes; they release gametes made in the gametangia directly into the water
Sperm motility allows more frequent fertilization
the advantage of sperm motility is that is allows "blank"
flowering plants
"blank" are the most highly evolved land plants, and still have multicellular gametophytes
Alternation of generations
"blank" made it possible for land plants to evolve from aquatic forms because the gametes are protected by being part of a multicellular structure
other evolutionary adaptations that facilitated the spread of plants from water to land are "blank" : to protect zygotes
vascular systems
other evolutionary adaptations that facilitated the spread of plants from water to land are "blank" : to facilitate water uptake and distribution throughout the plant
other evolutionary adaptations that facilitated the spread of plants from water to land are "blank" : to increase surface area of the plant exposed to light and the number of cells available to produce sucrose (hint: they arose from branchin vascular tissue)
they had to grow in very moist environments so they can get enough water
the bryophyte species of plants are seedless plants with no vascular systems; in order to compensate for no vascular systems they had: "blank"
Bryophyte species have special cells that send out processes called rhizoids (much smaller and less efficient than roots)
the bryophyte species of plants are seedless plants with no vascular systems; in order to compensate for no roots they had: "blank"
motile sperm during rainy periods
Bryophytes reproduced by have "blank" that are released from male gametophytes directly into the water
Gametophytes get smaller while sporophytes get larger
as phylogeny proceeds what happens to the size of the gametophytes and sporophytes
"blank" is a feature early plants had where there's only one kind of spore that produces both sperm and eggs
"blank" is a feature more evolved species of plants have where there are male and female gametophytes
microsporangial cells make the "blank"
macrosporangia make the "blank"
. Since there are two forms of gametophyte, the species don't have to rely totally on rain to allow sperm-egg contact
the advantage of repdroducing using the heterspory method is that "blank"
alternation of generations
This form of reproduction is a derived characteristic of land plants
sessile; immobile
The multicellular gametophytes of plants allow sexual reproduction of species that are "blank"
"blank" has a cost in that recessive mutations would be expressed and may be deletarious to the sporophyte fern (fern in this example)
"blank" are terrestrial plants that have roots, vascular systems, and seeds but not flowers. The adult plant is almost entirely the sporophyte form. There are small male and female gametophyte structures, usually pine cones.
"blank" are flowerin plants and are monocots and dicots. The names refer to an event that occurs soon after seed germination, the formation of cotyledons (primary shoots). Monocots have a single cotyledon, dicots have two. There are some not-terribly-important anatomical differences between monocots and dicots, but in general the two are very similar
Angiosperm reproduction
"blank" plant reproduction: Male and female reproductive organs are commonly found in the same plant, sometimes separated (male flowers and female flowers) sometimes in the same flower. Angiosperms also appear as different sexes, female plants and male plants.
monocots have parallel veins while dicots have a central vein with branches running out to the edges of the leaf
one difference between monocots and dicots that refers to the veins in the leaves is that "blank"
"blank" function to attract pollinators and thus increase the probability of zygote formation
sepal, petal, stamen (male), and carpel (female), are the 4 layers of modified leaves that "blank" consist of
Attractants of pollinators
color, odor, and reward are the 3 "blank"
a perfect flower
a "blank" flower is one which has all 4 layers and contains both male and female reproductive tissues (it is monoecious).
Dioecious plants
"blank" plants are imperfect because the two sexes are part of different plants
attract animals that will scatter the seeds after eating the fruit
the purpose of fruit is it "blank"
single carpel (or several fused carpels) of one flower
simple fruits develop from a "blank"
many seperate carpels of one flower as in berries
aggregate fruits develop from "blank"
many carpels of many flowers as in pineapple
multiple fruit develops from "blank"
start of animal diversity
During "blank", cells come in contact with each other as they slide against each other. The contact allows the cells to instruct each other what to become later in development.
Radial or bilaterall
the two basic kinds of body plans for embryos (symmetry) are either "blank or blank"
a "blank" is a fluid-filled space within an animals animal's body surrounded by tissue that is derived from the middle layer of early embryos, the mesenchyme. True "blank" animals have mesoderm surrounded cavities.
"blanks" have coeloms bordered by mesoderm on one side but by endoderm (gut, the innermost early embryo tissue layer) on the other
tube within a tube body plan
In this "blank" body plan, the gut is one tube and the body wall is the other. In between there is a completely mesoderm-lined coelom or a pseudocoelom. All these internal spaces are filled with fluid.
feeding and movement
two major adaptations that defined early animal evolution are "blank and blank"
holometabolous metamorphosis,
"blank" metamorphosis, (a complete remodeling) is where Animals that undergo metamorphosis may do so in a fashion such that the early form, the larva, goes into a phase (pupa) where the larval structures are largely lost and adult structures are formed
The other strategy for metamorphosers is to have a 'nymph' form, one that looks like the adult. During "blank" metamorphosis relatively slight changes occur. But metamorphosis can occur more than once, causing greater changes in the ultimate adult.
"blank" are the first to have 3 distinct tissue types made of similar cells - endoderm (gastroderm), mesoderm (mesoglea), and ectoderm (epidermis).
"blank" have anuses formed from the blastopore during early development and the mouth formed from the other end of the archenteron (gastric tube).
"blank" (more primitive than deuterostomes) have mouths formed from the blastopore and anuses formed from the other end of archenteron.
the notochord
the "blank" , present in all chordate embryos, is a longitudinal, flexible rod located between the digestive tube and the nerve cord. It is composed of large, fluid-filled cells encased in fairly stiff, fibrous tissue. It provides skeletal support throughout most of the length of the animal.
the phylum chordata (vertebrates)
the phylum "blank" consists of sharks, rays, bony fish, amphibians, reptiles, birds, and mammals
bony fish
"blank" are the most numerous group of vertebrates, both in individuals and species
"blank" are animals whose embryos are protected by one or more membranes
amniotic egg
eveolution of the "blank" egg expanded the success of vertebrates on land
start of plant structure and function
"blank" absorb water, minerals, fixed nitrogen from the soil.
Mineral ions
"blank" are needed to give some proteins such as chlorophyll and numerous enzymes particular shapes required for their activity.
dermal, ground, and vascular
the three plant tissues are "blank blank and blank"
dermal (epidermis)
outer tissue layer; ). It carries out absorption in the roots and forms protective coverings (eg, waxy cuticle, corky bark) of the shoots and leaves
dermal layer (endodermis)
surrounding the vascular tissue in the roots
vascular tissue
blank tissue comprises the xylem and phloem tubes which move water (xylem), nutrients (phloem), and minerals from the point of synthesis or absorption to the rest of the plant.
ground (basic) tissue
blank tissue cells carry out most of the metabolic activities of the plant and provide structure.
carry out photosynthesis
central vacuole
allow water balance and turgor pressure to e regulated
cell wall
gives the rigidity of the edge of the plant
continuous tube like openings connecting one cell with its neighbor
cell walls
blank are made of cullulose fibrils primarily; cellulose microfibrils are always parallel in each individual layer
paranchymal cells
blank cells cells tend to have thin cell walls and do most of the metabolism for a plant - photosynthesis, sugar synthesis, etc. They are active cells with lots of organelles
meristematic (dividing)
plant cells are either permanent and dont divide or they are "blank" and do
all meristem cells are blank
collenchymal cells
are less active metabolically, have thicker walls, and tend to be part of the plant support system. Their thicker cell walls have moderate amounts of cellulose microfibrils
sclerenchymal cells
blank cells are support cells that have thick secondary cell walls strengthened with lignin. Such cell walls are relatively strong and resist deformation. At functional maturity most sclerenchymal cells die, leaving the cell wall. The cell walls are so thick there's very little lumen (inner space of the cell) where the cell (protoplast) used to be before it died. These cells make massive amounts of strong cell wall and then die. Wood and fruit stones/pits are sclerenchymal.
vascular system
Xylem is the root-to-shoot water-conducting system of plants. Xylem tubes move water and minerals upwards from the roots. The tubes consist of sclerenchymal cell walls surrounding open space; the cells (protoplasts) that made the cell walls died and disappeared. Before they died they made plasmodesmata tubes from cell to cell. Thus, the hard cell walls still have these openings for water to pass through on its way up the plant. Tracheids are long tubes of end-to-end strings of long cell walls. Tracheids are massed side-to-side in large bundles. Vessel elements are similar to tracheids but individual units have much larger diameters than tracheids; the fluid-filled open space in the middle is larger. Fluid is 'pulled' up tracheids and vessel elements by negative pressure generated by evaporation.
Vessel elements and tracheids also contain lots of other sclerenchymal cells for support. In trees, xylem is the "wood".
phloem tubes
Phloem tubes move organic food molecules both up and down the plant. "Sieve-tube member" cells are sclerenchymal and are aligned end-to-end with a cell wall plate perforated by many plasmodesmata between cells. These cells are not dead but they do lack many organelles (like the nucleus) and they cannot make their own nutrients. Water and molecules traveling through phloem cross from cell-to-cell through plasmodesmata.
Companion cells (parenchymal) 'take care of' the sieve-tube member cells by feeding them through small plasmodesmata channels that pierce the cell walls between them.
Apical meristem cells
blank cells cells are found at the primary stem tip, at stem axillae (nodes), and at root tips. These meristem cells give rise to the 3 primary stem cell types
protoderm type
Stem cells divide and their progeny become dermal tissue cells
ground meristem
Stem cells divide and produce ground tissue cells, parenchymal cells carrying out photosynthesis, metabolism, nutrient storage, etc.
procambium (vascular meristem)
Stem cells divide and progeny differentiate to form vascular tissues. Some form xylem at the inner edge of the procambium, others form phloem at the outer edge of procambium
the root cap
the blank, the growing tip that has no hairs, is covered by a shield of flat cells for protection as the root grows through soil. These outer root cap cells are sloughed off and are replaced by division of root meristem cells. This zone of proliferation in the center of the root cap is part of the primary apical meristem population of stem cells.
blanks usually have fibrous roots (root balls)
blanks have tap roots, and lateral extensions (secondary roots)
an embryonic root
a blank root is a radicle
adventitious roots
blank roots develop from stems
apical meristem cells
increase length of roots and shoots/ plant body in general
the vascular cambium is a lateral meristem
that adds cells to increase the diameters of roots and shoots; adds new xylem tissue inwardly and new phloem tissue outwardly
there is also a protoderm meristem
blank meristem on the outer edges of shoots and roots that provides new epidermal cells
primary growth
blank growth occurs during the first year and is the complete growth of most plants
woody plants
continue to grow and lay down tissue for consecutive eyars
secondary growth
in blank growth it is the vascular cambium that produces the cells that make the plant larger in diameter
cork cambium
blank cambium is a meristem located outside the vascular cambium and under the corky layer of bark; These cells divide and their progeny differentiate to produce the cork-like tissues at the outer edge of tree bark.
blanks are continuous sheets of paranchymal cells that function to move nutrients laterally within a shoot; they are responsible for bringing nutrients to cells located relatively far from the phloem
blanks are small pore like openings in the bark of young twigs; the pore allows gas exchange and slight movement of water vapor to the outside environment
start of animal tissue
four basic animal tissues
epithelium, connective tissue, muscle, and nerve
4 kinds of connective tissue
CT proper, bone, cartilage, and blood
ct proper
Proper Loose (areolar) connective tissue proper (CTP) is 'packing material' found between other kinds of tissue. The softer parts of your body have loose CT as a major component. There are two kinds of dense CTP, irregular and regular. Regular DCT is made of parallel arrays of strong collagen fibers and is found in especially tendons, immensely strong CT that holds muscles onto bones. Dense irregular has a high proportion of collagen fibers and the fibers are not parallel to each other. Dermis of your skin is a rather dense CTP in many spots. Adipose CT (fat) is loose CTP with lots of fat cells in it. The fat serves as an energy store for the animal.
blank is made of calcium phosphate crystals bound to collagen fibers. It is very strong yet not brittle (somewhat flexible). The crystals are attached to the collagen fibers.
blank is incompressible, strong, and slick (low friction surface for joints).
blank is completely different from the other connective tissues; it's not really a CT but has been classified as CT for centuries. It is a liquid (plasma) with cells in it.
loose connective tissue proper
blank has relatively lots of cells, fewer and smaller collagen fibers, more liquid/gel 'ground substance' and more extracellular fluid than dense connective proper has.
It is a soft extracellular matrix that fills space, provides padding, and gentle support.
dense CTP
blank has Massive amounts of thick collagen fibers, very few cells, very little ground substance; The thick cables are made of very many individual collagen fibers attached to each other
blank in vertebrae and other bone joints is not elastic, it's called 'hyaline'.
All blanks consist of cells embedded in a thick matrix with fibers to give it strength.
blank cells (osteocytes) are embedded in blank matrix, a complex array of collagen fibers and crystals of calcium phosphate. The crystals make the matrix solid and the fibers allow a little flexibility (so you don't break your bones every time you fall).
Nerve tissue
blank tissue tissue senses stimuli and transmits signals from one part of the animal to another.
Muscle tissue
There are three kinds of muscle - skeletal, cardiac (heart), and smooth.
Skeletal muscle is composed of bundles of long fibers. Each fiber is a cell and contains many nuclei (up to hundreds/thousands of nuclei). Skeletal muscle fibers appear cross-striated in the microscope. Skeletal muscle is 'voluntary' muscle.
Cardiac muscle is also cross-striated but is made of single-nucleus cells connected end-to-end.
Smooth muscle is not striated and is composed of single cells attached to each other. There are no multinucleated fibers. Smooth muscle is found in the digestive tract, blood vessels, respiratory tubes, the uterus, and many other locations.
Blood consists of red and 'white' blood cells suspended in a liquid (plasma). The function of blood is not really connective even though it is usually categorized as a connective tissue. It simply functions to transport molecules from place to place within an animal's body.
is one of the four basic tissues of Animals. Different types of epithelium are found in different anatomical locations.
Stratified squamous epithelium (many layers of flat cells) is found where there's lots of stress and strain and abrasion such as skin (integument) and parts of the GI tract (mouth, esophagus, anus). Simple squamous (single layer of flat cells) is found where diffusion of molecules from one place to another is common - lungs, capillaries, etc.
Simple columnar and cuboidal epithelia are found where molecules are transported from one side of the epithelium to the other as in the GI tract and many glands.
simple squamous (one layer of flat cells)
is usually found where transport across the tissue is important - small blood vessels (capillaries) and capillaries in the lungs (gas exchange).
simple columnar
columnar is found where molecules are transported from one place to another like in the small intestine
an organ
(stomach, brain, eye, liver, etc) is made up of different kinds of tissue, each contributing something to the overall function of the organ. Most organs contain epithelium (more than one kind), connective tissue proper (more than one kind), and nerve. Blood of course is always present inside blood vessels. Bone is not found as part of an organ except in unusual species and circumstances.
organs are organized into systems
Digestive system (mouth, esophagus, stomach, small and large intestines, rectum, anus). Respiratory system (mouth/nose, trachea, bronchi, lungs), etc.
An organ system is a complex array of tissues and organs coordinated to carry out a particular set of processes.
levels of organization in the nervous system
The response of a single nerve cell to a change in its plasma membrane causes a large series of changes propagated through chains of nerve cells that culminate in some sort of action or perception by the animal (person).
start of nutrient gathering plants
surface to volume ratio probelm
Therefore there is a maximum size to which a cell can grow. The maximum size is that which allows enough nutrients to move across the cell's PM for the cell to survive.
All living organisms need nitrogen to make proteins and other sorts of macromolecules.
Neither plants nor animals can use the nitrogen gas (N2) in the air. Nitrogen must first be 'fixed', turned into a useable form such as an amine or nitrate. Animals get their fixed nitrogen by eating plants while plants get their fixed nitrogen from soil bacteria. Fixed nitrogen enters plants through the roots.
solute potential
tendency of water to move by osmosis
When water diffuses through a membrane it is called osmosis but in reality it is still just simple diffusion down a concentration gradient (higher to lower concentration). The higher water concentration is the place that has the lower concentration of 'solutes'. Solutes are molecules dissolved in the water and the more solute molecules there are the fewer water molecules can be present.
methods of diffusion
Osmosis/diffusion of water molecules through a membrane like a cell plasma membrane occurs in two ways. (1) water molecules diffuse directly between the lipid molecules of the membrane, and (2) there are protein facilitated-diffusion channels (aquaporins) in the membrane that allow water to diffuse through a channel in the middle of the protein. A water channel is like a small hose. Aquaporin channels greatly increase the rate of water diffusion.
pressure potential
tendency of water to move in response to pressure; Hydrostatic pressure built up by diffusion of water into a plant cell's cytoplasm is resisted by the rigid cell wall.
water flow across a membrane
can be reversed by applying pressure
water potential
consists of solute potential and the water pressure potential
What happens to plant cells when the solute pressure or water pressure change.
When the solute concentration inside a cell is higher than outside, water moves into cell—from an area with high water potential to an area with low water potential; from high water concentration to low water concentration.
Water diffuses into the cell until the water potentials are equal. At that point there is no net movement of water.
a flacid cell
is one that has zero pressure potential
plant cells
Plant cells can use ATP energy to move water into the vacuole and 'pump up' the cell. Different kinds of movements of stems and leaves are driven by this kind of regulation of water movement.
stoma guard cells and active transport
Stoma guard cells use energy (active transport) to move water into their vacuoles so as to close the stoma at night or when the plant loses too much water during transpiration on a hot, dry day.
movement of water up roots and shoots
Plants must be able to take up water from the environment (eg, moist dirt) and to move it up the plant roots and stems so all the cells get some. The strategy for always being able to do this is to regulate the water potential Ψ within all its cells and tissues such that Ψ is increasingly negative as you go up the plant, from roots to shoots to leaves. Water will always follow the path leading to lower water potentials.
root structure
In roots, vascular tissue (xylem and phloem) is in the center, surrounded by a dermal cell layer, the endoderm. Water must diffuse from the environment, through cell membranes into root cells and then find a path to the vascular cylinder.
water travels from root hairs to xylem via two routes
Within plant tissues water travels from one cell to another by diffusing DOWN the water potential gradient.
Plant cells commonly have open channels (plasmodesmata) between neighboring cells, an easy route for water to take if the water potential is different between cells. This is the 'symplastic route'.
Water can also diffuse entirely within the intercellular space, primarily within the cell wall. This is the 'apoplastic route'.
There is a third route as well, the 'transmembrane route'. Here, water crosses from cell wall space (intercellular) to cell cytoplasm and vice versa by crossing the plasma membrane. Movement of water across the cell membrane is usually by osmosis, sometimes by diffusing through a protein-lined channel
Water uptake and the casparian strip: routes of water movement in plants
casparian strip
a water impermeable waxy layer within the cell wall
when there is a casparian strip
this means that all the water and all the solutes that move from the dirt into the central part of the root, the vascular cylinder, by apoplastic route must be able to pass through the endodermis cell membranes (the transmembrane route); this helps the plant exclude particular types of molecules
casparian strip
is made by the endoderm cells on the sides where they touch other endoderm cells
endodermis cells
use active transport to pump ions into the space around xylem tracheids, making the more negative and thus attracting water from the endodermis cells (which in turn, replace the water with that flowing in from the environment through root epidermis cells)
movement of fluids and solutes through the root tissues to the vascular channels is osmotic flow
the movement within the xylem tubes is bulk flow (water and solutes flow together)
water surface tension
results from the polar nature of water
the cohesion-tension theory
Xylem vessels, especially tracheids, are very small diameter and thus surface tension at an air-water interface is very high as the water molecules try to move up the tube at the edges, pulling others from below. The hydrogen bond-forming ability of water molecules makes them cohere while their tendency to bind to anything that has slight electric charge (ie, 'polar' molecules) allows them to creep along surfaces to which they bind. In xylem tubes (a cell wall) the water molecules bind to the cellulose fibers of the cell wall and creep upwards, pulling cohered water molecules below them up as well. The result is that water will rise up a small diameter tube until gravity equals the force of cohesion and adhesion. Surface tension allows water to move up small-diameter tubes farther than up large-diameter tubes.
water molecules in tracheids of a leaf move out onto air surface to evaporate
the evaporation increases surface tension at the top of the xylem tubes and thus, pulls more water molecules out onto the air surface and thus more water is pulled up the tube from the roots
start of nutrient distribution in plants
CO2 enters a leaf and is converted to sugar; O2 enters all cells and is used to help produce the ATP to make new useful molecules
pulls water up xylem and other very small-diameter tubes
Liquid water in the xylem
flows out into the empty space among the mesophyll cells in the center of the leaf; it begins to evaporate and the water vapor diffuses rapidly out the stomata openings into the environment
Adaptations to dry environments for dry environment plants (xerophytes)
#1-they place stomata inside pockets that extend into the leaf and then having little hair like cell extensions to disrupt air flow to reduce the evaporation rate;
#2- another way is to make very thick, water impermeable cuticle layers on surfaces exposed to air
-dry environment plants tend to have lots of long roots to gather what little water that might be available
made of waxy substances like suberin
the sucrose made in photosynthetic tissues is transported by the phloem to all other cells of the plant
source cells and sink cells
cells that make phloem/sucrose are source cells; those to which it is transported and in which sucrose is used, are sink cells
sucrose rich fluid moves from one phloem sieve tube member cell to its neighbor through plasmodesmata
moves through tubes via pressure flow generated by the active transport of sucrose into phloem cells
xylem sap movement is via transpirational pull
passive simple diffusion
fat-soluble molecules dissolve in the lipids of a cells plasma membrane and diffuse through it; simple diffusion is only for th molecules that are soluble in the cell membrane
facilitated diffusion
is facilitated by protein channels that provide a water-filled channel for water-soluble molecules to diffuse through
is a form of facilitated diffusion in which the movement of one molecule such as protons is coupled to the movement of another ex: sucrose
active transport
a form of facilitated diffusion in which energy (atp usually) is used to force integral membrane proteins to change shape and to physically move solute molecules from a region of lower concentration to a region of higher concentration
active transport
transported molecule attaches to protein; protein changes shape and puts transported molecule on opposite side of membrane where the concentration was higher; then the protein dissociates from the transported molecule; can use thermal energy for the release when the affinity is low
moving sucrose into a cell using atp indirectly
sucrose diffuses down concentration gradient through plasmodesmata to get into the companion cell and then by facilitated diffusion through a transported to get into the leaf cell; atp is not used to force active transport, but instead to supply energy needed to make big molecules like proteins from the sucrose
moving sucrose into a cell using atp directly
atp is used to directly reduce the concentration of sucrose in the cytoplasm thus creating the concentration gradient that forces more sucrose into the cytoplasm from outside the cell; atp is used directly to change the shape of an active transport protein that moves sucrose across a membrane
mesophyll source cells
synthesize sucrose and are connected to other mesophyll cells and to bundle sheath cells by plasmodesmata; the bundle cells are around the phloem, the next destination of the sucrose
active transport of protons causes sucrose to be co-transported across membranes into or out of cells
this happens by transmembrane and apoplastic paths of diffusion; water moves by diffusion into the phloem tube along with the sucrose; this creates a high hydrostatic pressure which moves the sucrose to the sink cells where it is metabolized; as its metabolized, the concentration of sucrose within a sink cell will go down, causing more sucrose to enter; in the sink region water leaves the phloem because the loss of sucrose increases the water potential causing the water to move into the lower xylem and back up the plant
start of plant nutrition: soils, roots, nitrogen
humus layer
the humus layer of mature soils contains the nutrients plants need as well as lots of organisms needed to make more
the soild dwelling organisms
serve to loosen up soil, produce fixed nitrogen, and aid nutrient uptake by roots (fungi)
present in the soil, dissolved in water; also released from root hairs by being pumped acros the cell membranes by active transport
in root cells uses up O2 and produces CO2 which dissolves out of the cells and ombines with water outside the root to produce bicarbonate ions and more protons
the acid microenvironment
dissolves minerals from the surface of soil particles and the released ions can enter the root hair cell by crossing the plasms membrane via a channel
entry into root cells by cationic and anionic minerals and nutrients
cations and anions are moved into the root hair cells by way of protein transportes
plant cells use lots of atp energy to move protons to a region of higher proton concentration outside the cell
they do this because useful ions like potassium and magnesium can diffuse into the cells because there is a lower + charge in the cell than outside , an electrochemical gradient
the high concentration of H+ outside the root cells
allows anions to be symported into the cell; proton moves back into the cell through a transported that also carries a nitrate ion
fungi help plants get water and essential nutrients
Endomycorrhizae send the thinnest hyphae tips into the root cells and nutrient transfer occurs directly in the root cell cytoplasm; the hypphae tend to end in cells near the casparian strip to increase the rate of water transport
ectomycorrhizal fungal cells
dont penetrate into plant cells, they take up water and nutrients and distribute it by diffusional flow to the hyphae and from there by osmosis out of the fungal cell and into space around root cortex cells
nitrogen fixation: the role of soil bacteria in the nitrogen nutrition of plants
no plants or animals can use the nitrogen gas in the air; it has to be changed to nitrate or ammonium; this is a process of fixing nitrogen; once the nitrogen atoms in the form of nitrate or ammonium it can be taken up by plants and used to make useful molecules like protein and nucleic acid
nitrogen fixing
nitrogen fixing bacteria convert N2 to NH4 in a process that takes a lot of energy;
ammonifying bacteria
convert nitrogen that already organic to ammonium, the form of NH3 in water; organic nitrogen is mostly in the form of amines; this process doesnt take much energy so it can occur quickly
nitrifying bacteria
convert some of the ammonium to nitrate; some of the nitrate is taken up into the root cells and used to produce nitrogen-containing molecules for plants use; most of the nitrate is reconverted by denitrifying bacteria to elemental nitrogen which is a gas and quickly diffuses back into air
nitrogen fixation in legumes
pea plants and other legumes have a mutual relationship with N2 fixing bacteria. the plant offers an attractant the bacteria moved toward. when the bacteris enter the roots they get nutrients from the plant and the bacteria give the plant fixed N; the bacteria are inside the root
Nitrogen fixation by bacteria
root hairs release flavonoid that attracts rhizobia bacter; rhizobia move into root hairs; rhizobia proliferate inside root hair and cause an infection thread to form; infection thred grows into the cortex of the root where it bursts, releasing rhizobia inside cortex cells
hydroponic growth
is used to identify essential nutrients
magnesium is an essential ingredient of chlorophyll; plants with too little Mg-chlorophyll are chlorotic (yellowed)