exam 1 review cards

Question 1

According to the endosymbiosis theory, what is the origin of the first photosynthetic eukaryotic cells?

Answer 1

The first photosynthetic eukaryotic cells originated through endosymbiosis about 3.5 billion years ago. The first instance of endosymbiosis was between a non-photosynthetic bacterium and a host, where the prokaryote consumed the bacterium, and the bacteria eventually became dependent upon the host for survival. This bacterium would become the ancestral mitochondria. A second series of endosymbiosis would occur between a host cell containing a mitochondrion and a cyanobacteria, where the cyanobacteria would also become dependent on the host cell and become a chloroplast.

Question 2

How long ago did land plants first appear on earth?

Answer 2

475 mya

Question 3

How did plants change the conditions on earth? How did those changes allow for animal life on earth?

Answer 3

Plants changed Earth’s conditions in several ways. Firstly, plants created organic matter on Earth that could be consumed by other organisms. Secondly, plants producing oxygenic photosynthesis increased the amount of O2 in the atmosphere, allowing for other organisms to survive. This oxygenic photosynthesis also contributed to the creation of the ozone layer, which protects life from harmful UV-C wavelengths.

Question 4

What is the origin of land plants? What are the ancestors of land plants?

Answer 4

Land plants originated from Chlorophytes, or green algae. They evolved from chlorophytes 470mya as they transitioned from aquatic environments to dry land. This benefitted the plants because of the lack of competition or predators, and the abundance of light, CO2 and minerals compared to aquatic enviroments.

Question 5

What do land plants and Charales have in common?

Answer 5

Plants and Charales have…
1.Cellulose in the cell wall
2. Formation of a phragmoplast during cell division
3. Plasmodesmata

Question 6

What are the five key characteristics of land plants?

Answer 6

apical meristems
alternation of generations
walled spores produced In sporangia
multicellular gametangia
Multicellular-dependant embryos

Question 7

What is meant by dependent embryos?

Answer 7

Embryos derive nutrients from the mother plant which facilitates self-supporting land structures.

Question 8

What does alternation of generation mean? What are a sporophyte and a gametophyte?

Answer 8

True for all plants, where cells go throigh meiosis to produce 1n spores which give rise to a multicellular 1n organism, the GAMETOphyte (gametes!!! 1n!!!). These gametes will then fuse for reproduction and create a zygote, which will then give rise to the DIPLOID SPOROphyte generation (makes spores!!!). sporophyte generation is typically more prevelant

Question 9

Compare the life cycles of a moss, a fern, a gymnosperm and an angiosperm?

Answer 9

moss:
gametophyte not dependant on the sporophyte. Sporophyte is the minor part of the plant, functioning as an extension of the gametophyte
fern:
dom. The sporophyte produces gametophyte, gametes fusie to make new sporophyte. sporophyte grow on gametophyte but the sporophyte is bigger.
gynosperms: male and female cones. male produces pollen for eggs called the microspore, and the female produces eggs called the megaspore. megaspore acts as womb where seed is formed with an embryo and is protected.
angio:
contains male and female parts inside the flower. contains pollen sac, stamen, petal, carpel ovule and sepel.

Question 10

n which types of plants are gametophytes not autotrophic?

Answer 10

seed plants (gymno and angio)

Question 11

How does the haplobiontic life cycle of the Charales differ from the diplobiontic life cycle of land plants?

Answer 11

Haplobiontic life cycle of Charales: haploid gametophyte, fertilization results in diploid zygote, meiosis results in haploid spores, spores develop into haploid gametophytes, cycle starts over. Diplobiontic life cycle of land plants: both haploid (gametophyte) and diploid (sporophyte) are multicellular, sporophyte dominant. Haploid gametophyte produces sperm and egg cells, fertilization results in diploid zygote, zygote develops into diploid sporophyte, meiosis results in haploid spores, spores released and develop into haploid gametophytes, cycle starts over.

Question 12

What are the characteristics of angiosperms that distinguish them from other plants? What are three advantages of angiosperms?

Answer 12

Angiosperms have flowers and fruit-enclosed seeds. Angiosperms 1. animals help plant reproduce by bringing pollen to stigma
2. seed enclosed in fruit, allows animals to disperse
3. endosperm. yummy.

Question 13

Discuss the characteristics of plants that distinguish them from animals.

Answer 13

Cell walls: Plant cells have cell walls, but animal cells do not.
Autotrophic: Almost all plants are autotrophic, which means they produce their own food through photosynthesis. Animals are heterotrophic, which means they depend on plants for food.
Motility: Plants are usually sessile, but animals are motile at some stage of their life cycle.

Question 14

What is totipotency?

Answer 14

Any cell can differentiate into another cell.
ex. parenchyma, collenchyma and sclerenchyma

Question 15

Explain the following sentence: “Development is to plants what behavior is to animals”.

Question 16

Describe the different types of plant tissue: meristems, epidermis, ground and vascular. Explain their functions.

Question 17

What is the cambium?

Question 18

What are parenchyma cells?

Answer 18

Specialized cells that can differentiate into collenchyma and sclerenchyma. exist all throughout the plant body.

Question 19

What is the cork cambium? What is the periderm?

Question 20

What is xylem? What is phloem? What types of cells are present in the vascular tissue?

Question 21

Are the cells that make the xylem vessels dead or alive at maturity? Are the cells that make the phloem vessels dead or alive at maturity? Do these phloem cells have nuclei? Do they have ribosomes?

Question 22

What is endodermis? What is the Casparian strip? What is suberin?

Question 23

What are guard cells? What are stomata? What is their function?

Question 24

Describe the general structure of a root, a shoot, a leaf and a flower (in a typical hermaphroditic plant).

Question 25

What are the main differences between plant and animal cells?

Question 26

What are the main differences between cellular membranes in plants and animals?

Question 27

How does the lipid composition of cellular membranes relate to cold acclimation in plants?

Question 28

What important organelles derived from the endoplasmic reticulum are common in seeds?

Answer 28

seed storage proteins. three types based on their solubility: albumins: soluble in water, globulins: soluble in dilute salt solutions, & prolamins: soluble in alcohol or acids/bases.

Question 29

What are protein bodies?

Answer 29

Protein bodies are organelles that store the seed storage proteins. Depending on the type of seed storage protein being stored, there can be different types of protein bodies.

Question 30

What are oleosomes? What are the components of these organelles?

Answer 30

seeds that accumulate oils. They are proteins from the smooth ER
components: oleosin/caleosin (proteins), phospholipid monolayer. ER tubule (connects to ER), droplets of oil on oleosome.

Question 31

What is meant by “acid growth theory”? Describe experiments that led to the elucidation of the mechanism of acid growth.

Answer 31

Lower pH results in more plant growth. Oxin increases acidity by increasing the activity of the hydrogen pump

Question 32

What is an essential element? How many have been identified?

Answer 32

An element a plant needs to live and can find in its environment

Question 33

What is the difference between a macronutrient and a micronutrient?

Answer 33

Macronutrients require more of that substance (N, K) than a micronutrient

Question 34

For the following ions, indicate whether their concentration is higher in the cytoplasm or outside the cell, and what kind of transport (passive, primary active, secondary active) across the cell membrane is responsible for maintaining the concentration gradient:

Answer 34

Anions: Higher conc in the cytoplasm
K+: higher conc. in cytoplasm, accumulates passively
Na+: higher conc outside of cell, actively transports outside of cell
Ca++, H+, Mg+: higher conc. outside the cell wall, actively transport out of cell

Question 35

What are plastids?

Answer 35

Plastids are photosynthetic organelles in plant cells, aka chloroplasts. There different types, proplastid: no thylakoids yet, jut inner envelope, outer envelope, and stroma. Chloroplast: have chlorophyll (present in dead parenchyma cells). Chromoplast: carotenoids, such as lycopene (in tomatoes, think RED). Leucoplast: colorless. Amyloplast: types of leucoplasts, for instance starch, lipids, and proteins. Etioplast: the outcome of a proplastid not receiving light so therefore not getting chlorophyll.

Question 36

What does a plant need to grow from seed and complete its life cycle? What is the difference between how plants and animals obtain the required nutrients?

Answer 36

Essential Elements
Plants obtain required nutrients from them being dissolved in water then taken in through the roots.
Animals obtain their nutrients from consuming food or liquids.

Question 37

What is an essential element? How many have been identified?

Answer 37

An essential element is defined as one that is an intrinsic component in the structure or metabolism of a plant or whose absence causes severe abnormalities in plant growth, development, or reproduction and may prevent a plant from completing its life cycle. Some essential elements are
Macro: N,K,Ca,Mg,Ph,S,Si
Micro: Cl, Pe,B,Mn,Na,Zn,Cu,Ni,MO
Group 1: N, S
Nitrogen and sulfur constitute the first group of essential elements. Plants assimilate these nutrients via biochemical reactions involving oxidation and reduction to form covalent bonds with carbon and create organic compounds (e.g., amino acids, nucleic acids, and proteins).
2: P, Si, B. The second group is important in energy storage reactions or in maintaining structural integrity. Elements in this group are often present in plant tissues as phosphate, borate, and silicate esters in which the elen1ental group is covalently bound to an organic molecule (e.g., sugar phosphate).
3. K, Ca, Mg, Cl, Zn, Na. The third group is present in plant tissue as either free ions dissolved in the plant water or ions electrostatically bound to substances such as the pectic acids present in the plant cell wall/part of C compounds. Elements in this group have important roles as enzyme cofactors, in regulating osmotic potentials, and in controlling membrane permeability. Mg is part of the chlorophyll compound and Cl is part of photosynthesis. K is used for maintaining turgor pressure. Na is only for C4 and CAM plants.
4. Fe Mn Cu Ni Mo. The fourth group, comprising metals such as iron, has important roles in reactions involving electron transfer. In other words, it is important for energy storage or structural composition. Cu, Ni and MO used for reactions.

Question 38

What is a hydroponic culture?

Answer 38

Hydroponic cultures are growth layouts that do not use soil. Air must be present to provide oxygen for the roots so there is a large air stone in the hydroponics tank to provide ample air bubblage for the root system to absorb the oxygen.

Question 39

What is the nature of the symbiotic relationship between Mycorrhizal fungi and plant roots?

Answer 39

Mycorrhizal fungi grow around the roots of gymno and angiosperms, where the fungus increases Phosphorus concentrations for the plant in exchange for sugars. Mycorrhizal fungi are absent in extreme conditions.

Different types of fungi are…
Ectomycorrhiza:
Found around roots and external cells in gymnos and woody angiosperms
Endomycorrhiza:
Found between cells and inside cells in the cortex forming arbuscules. Minerals get transported out of fungi, and sugars and imported into the fungus.
Rhizobia:
Special nitrogen-fixing bacteria.

Question 40

What creates the voltage across the plasma membrane in plant cells? How is this different from what happens in animal cells?

Answer 40

The active transport of H+ across the plasma membrane creates a membrane potential. The inside of the cell is negative w/ respect to the outside. The membrane potential results in uneven distribution of ion across the cell membrane w/out active transport. Plant H+ ATPase is not found in animals or in yeast, although similar enzymes are present in some bacteria and protists.

Question 41

What is meant by the term “active transport”? What is the difference between “primary” and “secondary” active transport?

Answer 41

Movement of solutes across membranes down their free-energy gradient is facilitated by passive transport mechanisms. whereas movement of solutes against their free-energy gradient, known as active transport and requires energy input. Primary active transport is the direct coupling of a metabolic energy source such as ATP hydrolysis, oxidation-reduction reaction, or light absorption to active transport by a carrier protein. Secondary active transport uses energy stored in the proton motive force or other ion gradient and operates by symport or antiport.

Question 42

How can the operation of the plasma membrane H+-ATPase affect (a) the diffusion of K+ through membrane channels, and (b) the accumulation of sugars from the apoplast into the cell?

Answer 42

a) K+ can travel in or out through membrane channels using passive transport
(b) secondary active transport

Question 43

Detection of external signals by plant cells often results in a transient rise in the concentration of Ca2+ ions in the cytoplasm. What transport processes can cause such an increase in cytoplasmic Ca2+, and what transport processes can remove the excess Ca2+ and restore the level of Ca2+ to its resting state?

Answer 43

Ca2+ pump in primary active transport. Na+ and Ca++ are actively transported out of the cytoplasm. They can move into the cytoplasm through channels.
Passive transport can cause an inc.
Active transport can cause a dec.

Question 44

In the transport of an ion from the soil solution to the xylem, what is the minimum number of times it must cross a cell membrane? What transport mechanisms are likely to be involved at each membrane?

Answer 44

The minimum number of times an ion must cross the cell membrane is twice because it makes must cross the Casparian strip and then for xylem loading. Mechanisms include traveling via symplastically and apoplastically.

The apoplast is the continuous system of cell walls, intercellular air spaces, and the lumens of nonliving cells (e.g., xylen, conduits and fibers). In this pathway, water moves through cell walls and extracellular spaces without crossing any membrane as it travels across the root cortex.
2. The symplast consists of the entire network of cell cytoplasm interconnected by plasmodesmata. In this pathway, water travels across the root cortex via the plasmodesmata.

Question 45

For the following ions, indicate whether their concentration is higher in the cytoplasm or outside the cell, and what kind of transport (passive, primary active, secondary active) across the cell membrane is responsible for maintaining the concentration gradient:

Anions, K+, Na+, Ca++, H+

Answer 45

anions - higher in, secondary active
K+ - higher in, passive
Ca++ - Lower in, Primary active
Na+ - lower in, secondary active
H+ - lower in, primary active
Transport across the plasma membrane

Question 46

How is the pH of the cytoplasm regulated?

Answer 46

The pH of the cytoplasm is regulated through oxin, which increases acidity by increasing the activity of the hydrogen pump. The hydrogen pump pumps out H+ ions from the vacuole.

Question 47

What is xylem loading?

Answer 47

Xylem loading is the process of transporting out of the xylem parenchyma thru the symplast, and into the hollow, dead xylem tubes, where movement is facilitated through the bulk flow of water.

Question 48

In terms of kinetics, what is the difference between simple diffusion and facilitated diffusion by a carrier?

Answer 48

Simple diffusion requires no expense of energy, it entails the use of a preexisting gradient between concentrations to transport between areas. Facilitated diffusion is the use of a preexisting gradient between areas as well, except that a carrier such as a channel is needed to access the area.

Question 49

What is a symporter? What is an antiporter? Give an example of each type of transporter on the plasma membrane of a plant cell. Give an example of each of them on the tonoplast.

Answer 49

Symporters and antiporters are considered secondary active transport that use electrochemical potential (pH gradient) as a source of energy.
Symporters bring anions, sucrose, and amino acids into the cell.
Antiporters push Na+ out of the cell, as well as Ca++ and sucrose into the vacuole(?) Possibly also ABC transporters.

Question 50

What are ABC transporters? What type of molecules are they involved in transporting across the tonoplast?

Answer 50

ABC transporters are ATP-binding cassette transporters that transport anthocyanins across the tonoplast to the vacuole.

Question 51

What are metal hyperaccumulators? Why can some plants accumulate more metals than others?

Answer 51

Metal hyperaccumulators are plants that can uptake heavy metals and other plants. They can uptake almost 10x the amount than regular plants.

Question 52

Why do some plants take in more metals than others?

Answer 52

Some plants have a higher biomass than others. This means that there is more area in the plant to sequester the toxin and they require larger amounts of absorption because they are a larger plant. Plants also have to be hardy and easy to cultivate.

Question 53

What is phytoremediation? What are the different ways in which plants can be used to clean up the soil from harmful metals or organic compounds.

Answer 53

Phytoremediation is the process of using plants and microbes for environmental cleanup. Methods used are phytoextraction, degradation, Phytostimulation, phytovolatilization, and rhyzofiltration.
Phytodegradation involves the degradation of contaminants absorbed into the plant. These plants can then be recycled into cardboard. Unfortunately, photodegrading plants struggle to grow in toxicity.
Phytostimulation involves the breakdown of the toxins using microbes in the root area but it’s a slow process.
Phytovolatilization involves the uptake and transpiration modifying these toxins via plant
Rhyzofiltration allows the rhizosphere to decontaminate water and wastewater. Plants must be growth elsewhere for this purpose.

Question 54

What is phytoextraction?

Answer 54

Toxins are sequestered from the soil through the plant extracting them. This requires that the plant be completely grown before it can start properly extracting toxins but the growth can be accelerated chemically.

Question 55

Speculate three possible ways plants can be genetically engineered to accumulate more metals. What proteins could you express in the plant to make it a hyperaccumulator?

Answer 55

Higher tolerance to high concentrations of heavy metals, higher amounts of accumulation and a faster rate of degradation for absorbed materials, in addition to higher biomass so the plant can uptake more materials at a time.

Question 56

What kind of ions and compounds accumulate in vacuoles? What kind of organic compounds accumulate in vacuoles in CAM plants? What type of transport is responsible for the accumulation of H+, anthocyanines, Ca++, and malate in vacuoles?

Answer 56

The ions vacuoles can accumulate are hydrogen (H+) and calcium (Ca++). The organic compounds vacuoles can accumulate are organic acids, such as malate in CAM plants. The transport responsible for H+, anthocyanines, Ca++, and malate is active transport, because they get pumped in with the use of energy.

Question 57

What are vacuoles? What are some of the functions of the vacuoles in plant cells?

Answer 57

Vacuoles are an organelles in plant cells, they can be small and there can be multiple vacuoles in one cell (usually young cells). Vacuoles used for storage of molecules, ions, organic acids. They can also be lytic vacuoles, that accumulate enzymes or toxic compounds and break them down.

Question 58

Using diagrams, describe the interconversions of different types of plastids. Explain the environmental conditions or changes that cause these changes in the plastids.

Answer 58

1. Proplastids get light = chloroplast
2. Proplastids lack light = etioplast
3. Chloroplasts lack light = etioplast
4. Etioplast get light = chloroplast
5. Amyloplast get light = chloroplast
6. Proplastid accumulate starch = Amyloplast
7. Chloroplast accumulate carotenoids = Chromoplast

Question 59

What kind of storage proteins accumulate in protein bodies? What type of storage proteins accumulate in the vacuoles?

Answer 59

Globulins accumulate in the vacuole. Globulin forms and buds off of the ER and is transferred to the Golgi apparatus and then transferred to the vacuole. After accumulating in the vacuole, the vacuole fragments, leading to the formation of protein bodies of globulin.

Question 60

What are peroxisomes?

Answer 60

Peroxisomes are a type of microbody that breaks down hydrogen peroxide, which protects cells from the oxidative effect of the compound.

Question 61

What are glyoxisomes? What is their function during seed germination?

Answer 61

Glyoxysomes are present in oil-storing seeds, and their function during seed germination for nutrition for the seedling. Since oils cannot be transported to the plant, the oils need to be converted to sugars and then transported to be used for nutrition. In the glyoxysomes, the fatty acids and glycerol from the triglycerides in the oil body are oxidated, and synthesis of the oil into sugar occurs. Help in production of sucrose, which can be transported to other parts of plant for energy.

Question 62

How are proteins targeted to the chloroplast, the mitochondria and the nucleus?

Answer 62

Proteins targeted to the chloroplast, mitochondria, or nucleus are synthesized on the free cytoplasmic ribosomes. Additionally, proteins targeted to the chloroplast may be targeted at a specific part of the chloroplast, such as the thylakoid membranes or the stroma.

Question 63

What is cytoplasmic streaming?

Answer 63

Cytoplasmic streaming is the movement of the cytoplasm in a cell in a circular or spiral flow along the cell’s membrane. Functions in nutrient distribution, waste removal, organelle positioning, and response to stimuli.

Question 64

What is the phragmoplast?

Answer 64

The phragmoplast is a structure that forms during cell division, has a role in forming the cell plate. Composed of microtubules and vesicles, and it forms during late cytokinesis.

Question 65

Name two processes that involve microfilaments in plants.

Answer 65

Cell division (cytokinesis) and cytoplasmic streaming.

Question 66

What is plant transpiration ratio? Is this higher for C3, C4 or CAM plants?

Answer 66

The plant transpiration ratio is the molecules of water lost by the plant per molecule of CO2 fixed. It is higher for typical C3 plants compared to C4 or CAM plants.

Question 67

How are stomata opened or closed? How do light and abscisic acid affect opening or closing of the stomata? What specific changes in ions increase or decrease turgor pressure in the guard cells?

Answer 67

The ratio of transpiration depends on the opening of the stomata, which is determined by the volume of guard cells.
Blue light causes opening of stomata by increasing ca++ concentration in the cytosol of guard cells. water out of guard cells decreases in volume of closing of stomata.
Abscisic acid causes closing of stomata by increasing Ca++ concentration in the cytosol of guard cells, and water out of guard cell decreases in volume for the closing of the stomata.

Question 68

What are the special characteristics of guard cells?

Answer 68

Guard cells have thinner, more extensible outer walls combined with a thickened, relatively inflexible inner wall. This is designed for the opening and closing of the stomata using osmotic pressure due to changing turgor pressures.
Guard cells are able to control how open or closed stomata are by changing shape. The guard cells change shape depending on the amount of water and potassium ions present in the cells themselves.

Question 69

In which conditions would transpiration be highest in a C3 plant?

Answer 69

Low humidity, high heat.

Question 70

What is cavitation? What mechanisms plants have to be able to transport water in the xylem despite cavitation?

Answer 70

Cavitation occurs when the air bypasses the endodermis and forms air bubbles in the xylem. These bubbles will expand due to negative pressure and this air bubble will block the water transport. However, if one vessel is blocked, sap can ascend through another one. New xylem is formed every year, replacing the blocked xylem.

Question 71

How does air relative humidity affect the transpiration rate of a leaf? How will a change in temperature affect transpiration rate?

Answer 71

It decreases the transpiration rate.
Higher temp = higher transpiration rate

Question 72

Describe the path followed by water from the soil, through the plant and into the atmosphere. Where in the path are the important resistances to water movement?

Answer 72

Water will be taken up through the roots by osmosis and the apoplastic, symplastic, and transmembrane pathways. Therefore, they go from the epidermis to the endodermis where the casparian strip is and the water is forces across the cell membrane.
Water is transferred through the xylem by cohesion and it travels through tracheids and vessel elements.
Cavitation can occur during this process; of which is a resistance to water movement.

Question 73

What is transpiration? What are the two reasons that make transpiration useful to the plant?

Answer 73

The evaporation of water from the surface of leaves and stems. It is created by a concentration gradient of water vapor between the intercellular space and the atmosphere.
1. Water evaporates in the intercellular spaces between the mesophyll cell of leaves, cooling the plant
2. transpiration increases the surface of water-air interface in the leaves which creates tension, pumping water and minerals to the leaves for photosynthesis.

Question 74

According to the current theory, what are the driving forces for the movement of water from the root to the top of a tree and into the atmosphere?

Answer 74

The cohesion of water molecules allows the movement of the water column in the xylem. It is driven by the tension produced in the leaves by transpiration. It is sustained by high cohesion of water molecules in the water column and is facilitated by the structure of the xylem.

Question 75

Describe root pressure and indicate when it might occur.

Answer 75

A positive hydrostatic pressure in the xylem of roots.
- occurs in the xylem of some vascular plants when the soil moisture level is high either at night or when transpiration is low during the day

Question 76

Describe the Casparian strip and its function. What is the most important substance in the Casparian strip, from the point of view of its function?

Answer 76

A band in the cell walls of the endodermis that is impregnated with the waxlike, hydrophobic substance suberin.
- prevents water and solutes from entering the xylem by moving between the endodermal cells

(most important substance is suberin and it is a polymer, lipid that is used for protection and healing)

Question 77

How does water move through the roots towards the xylem?

Answer 77

Through osmosis: from the epidermis to the endodermis
- Apoplastic pathway
- Symplastic pathway
- Trasnsmembrane pathway

Question 78

How is absorption surface in the roots increased?

Answer 78

permeability of cell walls in the root cortex

Question 79

What is the permanent wilting point? Is this the same for all plants in all soils?

Answer 79

It is the point where the water potential of the soil becomes lower than the of the plant. Even if the plant does not lose any water by transpiration it will wilt. This point is different for different plant species.

Question 80

How does water move in the soil towards the plant?

Answer 80

How does water move in the soil towards the plant?
It moves towards the soil through soil hydraulic conductivity. it moves from the soil towards the roots by bulk flow through the channels in the soil.

Question 81

Compare and contrast the structures, composition, and functions of primary versus secondary cell walls.

Answer 81

Primary Cell wall, unspecialized and similar, increase in surface area during expansion. Secondary cell wall forms after cell growth has stopped, smaller proportion of pectins and have lignin and suberin, unlike primary. Highly specialized in structure and composition so they vary between plant cells

Question 82

Describe the structures and composition of cellulose, hemicelluloses and pectin.

Answer 82

Cellulose- main component of cell wall, mad of glucose. Linear polysaccharide makes long chains that add strength to cell wall. Beta Glucan
Pectins- branch polysaccharides, rich in galactan acid. The loss of hydrogen ion results in a negative charge. They make up middle lamella and present in primary cell wall. Attract water molecules and regulate porosity of cell wall. Synthesized in Golgi and secreted in the cell.
Hemicelluslose- cross-linking, branch polysaccharides that have different types of monosaccharides (glucose, arabinose, etc.) adds strength to cell wall. Synthesized in Golgi and secreted in the cell.

Question 83

Give examples of the types of proteins present on the cell wall.

Answer 83

Nonezymatic proteins (Table 14.2) HRGP, PRP, GRP, AGP

Question 84

Where in the cell is cellulose synthesized? Discuss the nature of the enzyme involved, its appearance in the electron microscope, and its interactions with components of the cytoskeleton. What role does this interaction play during microfibril deposition?

Answer 84

Cellulose is synthesized on cell surface because of such long chain by enzymes (rosets?) (cellulose synthase?) on the plasma membrane, then passed to outside of cell. The enzyme uses UDP glucose obtained by sucroseto attach the subunits on the cellulose polysaccharide chains. The cellulose can cross link some of the microfibril adding support to the cell wall.

Question 85

What is lignin? Where is it produced?
What components of the cell wall are secreted via the Golgi in plant cells?

Answer 85

Lignin is a polymer made of monolignols (they will have a phenol ring). Synthesized in ER from coumaric acid. Lignin and hemicellulose are secreted via the golgi (any polysaccharide)

Question 86

What effects do microtubule poisons usually have on the directionality of plant cell expansion, and why?

Answer 86

The microtubules don’t polymerize correctly and the microfibers are not deposited horizontally, which would lead to vertical elongation in the root. The cell expands in all directions causing root to grow in a block shape

Question 87

What are ROS, when might they be produced, and what changes do they cause in the cell wall?

Answer 87

Reactive Oxygen Species (ex: H2O2 or O anions) they aid in crosslinking of monolignols to result in increased production of lignin to fortify plant cell and prevent further attack from pathogens

Question 88

What are plasmodesmata? Describe their structure.

Answer 88

ER gets cut when vesicles are fusing to form cell plates, the openings or “pores” are the plasmodesmata they bring together the cytoplasm of two cells.

Question 89

What kind of molecules can move through plasmodesmata? Is the movement of small molecules through plasmodesmata restricted?

Answer 89

Any molecule smaller than the small inclusion limit can move through (SIL=1 kilodalton, about 10 nucleotides) no protein or RNA can go through unless specialized

Question 90

Do any macromolecules move through plasmodesmata? Is this movement specific? How is the specificity determined? What are the implications in plant development?

Answer 90

Yes, otherwise the plant would not receive theses essential elements, and thus would not develop. This movement is specific and is determined by the macromolecule.

Question 91

How do viruses move from one cell to another in the plant? How do they get in the vascular system of the plant?

Answer 91

The plasmodemata determines if the virus moves to other cells. They would have to pass through the casparian strip to reach the vascular system.

Question 92

What is the symplast? What is the apoplast?

Answer 92

Symplast the entire network of the cytoplasm connected by the plasmodesmata allows water to travel through root cortex through plasmodesmata
Apoplast water moves through cell wall without crossing through any membranes as it goes through the cortex

Question 93

Given two solutions which one has the higher water potential, the one with the lowest concentration of solute, or the one with highest concentration of solute?

Answer 93

The solution with the lower solute will result in higher water potential.

Question 94

What is the definition of water potential?

Answer 94

The free energy of water per volume of mole of water ata certain stage compared to pure water (the standard) Tells us the ability of the water to move or perform work. Measured in pressure units pascals or Mpascals

Question 95

What is the importance of the water potential concept in plant physiology? What are the components of water potential?

Answer 95

Water moves without force from areas of higher water potential to lower water potential. The components are solute potential and pressure potential.

Question 96

What is turgor pressure? Can plant cells have negative turgor pressure values? Can you calculate the turgor pressure of a cell from water potential and osmotic potential values?

Answer 96

Turgor pressure is the force the cell exerts against the cell wall. Plant cells can’t have negative tugor pressure. Yes you can calculate tugor pressur by subtracting osmotic potential and water potential.

Question 97

How does water move across small distances in plants?

Answer 97

The water moves by passive transport through diffusion or bulk flow due to pressure gradient.

Question 98

How does water move across a largely hydrophobic plasma membrane?

Answer 98

Through osmosis or plasmodesmata

Question 99

What is the driving force for osmosis?

Answer 99

A water potential gradient drives osmosis

Question 100

What are aquaporins?

Answer 100

A very complex transmembrane molecule, that crosses the cell membrane 6 times to make the channels that allow the water molecule to cross the cell membrane from the outside to the inside of the cell

Question 101

The following values correspond to the components of water potential in a plant cell:

Yp= 0 MPa, Ys= -0.732 MPa

Explain what these values mean. Is this plant cell that of a normal healthy leaf? Explain your reasoning.

Answer 101

Yp is pressure potential, positive in plant cells because tugor pressure inreases the free energy of water in the cell. Ys is solute potential, negative in solutions or cells because solutes decrease the free energy of solution.

Question 102

Describe the Casparian strip and its function. What is the most important substance in the Casparian strip, from the point of view of its function?

Answer 102

Impermeable strip made by cell walls of endodermal cells made of suberin. Prohibits water molecules from crossing into the vascular tissue.

Question 103

Discuss the various roles played by microtubules and microfilaments in plant cells. What is the arrangement of microtubules during the different stages of the cell cycle?

Answer 103

Microtubules play a role in cell division, cell shape & support, intracellular transport, and cilia & flagella. Microfilaments play a role in cytokinesis, cell shape & motility, an cytoplasmic, endocytosis & exocytosis, and pollen tube growth. During interphase, the microtubules are a part of the cell/s cytoskeleton. During prophase, the mitotic spindle begins to form. During metaphase, the mitotic spindle is formed and they extend from opposite poles in the cell. During anaphase, the microtubules shorten and pull the sister chromatids apart. During telophase, the nuclear envelope begins to form and the microtubules begin to disassemble. During cytokinesis, the microfilaments form a contractile ring.

Question 104

How are the new cell membrane and cell wall formed during cytokinesis?

Answer 104

The new cell membrane and cell wall are formed from a combination of phragmoplast formation, vesicle fusion, cell plate expansion, cell wall synthesis, and fusion with the plasma membrane.

Question 105

All cellular organelles in a plant cell have proteins encoded by nuclear genes. For these proteins, where does synthesis take place, in free ribosomes or the ER?

Answer 105

This depends on what organelle the proteins were targeted to. If the proteins were targeted to the chloroplast, mitochondria, or nucleus, the proteins were synthesized on the free cytoplasmic ribosomes. If they were targeted to other organelles, they were synthesized on the ribosomes attached to the endoplasmic reticulum.

Question 106

Describe the basic steps involved in the synthesis and processing of a typical secretory protein.

Answer 106

The basic steps involved in synthesis and processing of a typical secretory protein goes as follows: transcription, RNA processing, translation, targeting to the ER, translocation into the ER lumen, signal sequence cleavage, protein folding, vesicle transport, golgi processing, sorting/targeting, and finally vesicle secretion.