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What order did the “-trophs” evolve in, and why? How old is the photosynthetic process?
Autotrophs developed after heterotrophs because heterotrophs had consumed the majority of the free-floating organic molecules. Photosynthetic process is 3.4 billion years old.
How did autotrophs contribute to the earth’s evolution?
Earth’s atmosphere was altered as O2 accumulated. Initially O2 collected in the oceans. Around 700 million years ago it began to reach the levels we are accustomed to. This created the ozone layer (O3) and allowed for aerobic respiration.
Where did plants evolve? Why?
When the ocean was nearly exhausted of its nutrients development began to occur along nutrient rich shores. Plants began to move to land after developing ways to deal with the lack of water (roots, stems, leaves, stomata).
The living and nonliving components and characteristic of an area.
Give an overview of plant’s importance (agriculturally).
- Plants provide macronutrients, essential amino acids (9), and phytochemicals.
- The major antioxidants (carotenoids and flavanoids) are phytochemicals.
What is taxol? How is it generated?
Harvested from the Pacific Yew, taxol inhibits the growth of cancer cells.
Explain basic cell theory, and describe the two major types of cells.
- Cell theory: All organisms are composed of one or more cells, and all cells come from existing cells.
- Eukaryotic cells: Contain membrane-bound organelles, and have DNA packed into a nucleus.
- Prokaryotic cells: Have no organelles and DNA is found free-floating in an area called the nucleoid.
What are the two main areas of a plant cell, and what do they encompass?
- Cell wall: Middle lamella, primary wall, secondary wall, plasmodesmata
- Protoplast: nucleus and cytoplasm (everything internal to cell wall)
Describe Primary Cell Wall composition.
- Cellulose: the most abundant organic compound on earth
- Hemicullulose: functions to glue cellulose fibers together
- Pectin: helps make wall flexible because of its water loving properties
- Glycoproteins and enzymes
What is the middle lamella?
Secreted by primary cell walls it is mostly pectin and acts as a region of union between adjacent cell walls.
Describe secondary walls
- Found in some plants as a second layer internal to primary walls.
- Chemically different from primary walls due to presence of lignin and higher proportion of cellulose
- Extremely thick compared to primary walls
- Contains thinner spots called primary pits which have a high distribution of plasmodesmata
What properties does lignin have? What chemical is derived from lignin and what are its functions?
- Imparts toughness (rigidity) to the cell
- Protects against pathogenic invasion
- Gives plants resistance to decay (although specialized fungi may still cause death of tree)
- DMSO (dimethyl sulfoxide) alleviates pain, but has been banned due to studies revealing it could result in eye damage.
What are the three major functions of cell walls?
The cell won’t pop under pressure, determines overall shape and provides rigidity, and has many enzymes that help with secretion and absorption
What are the types of plant plastids with a structural and functional description of each type.
- Chloroplasts: green due to chlorophyll pigment. Functions include photosynthesis, amino acid synthesis, and fatty acid synthesis.
- Chromoplasts: red/orange/yellow due to carotenoids. Give fruits and vegetables their characteristic colors, functionally not well understood other than to attract insects to plant through coloration.
- Leucoplasts: colorless due to lack of pigment. Act as a warehouse, storing starch, oils, or proteins. Includes amyloplasts (for starch).
Define thykaloids, stroma, and grana.
- thykaloids: system of membranes in a plastid.
- stroma: homogenous matrix in a plastid.
- Grana: stacks of thylakoids in chloroplasts
Describe how various plastids can evolve.
- The protoplast is the “stem cell” of plastids, with the ability to turn into a chromoplast, leucoplast, or develop (through a process) into a chloroplast.
- The three plastids share an interesting ability to alter themselves and become a different plastid: mature chloroplast <-> chromoplast <-> amyloplast
- Large membrane enclosed region filled with fluid containing salts, proteins, etc
- Tonoplast: membrane surrounding vacuoles
- Contains anthocyanins (soluble pigments) that contribute to flower color
- Waste crystals may be deposited here and enzymes help recycle old organelles
- Helps to maintain the rigidity of the plant cell.
What are the characteristics that make a plant cell unique?
Cell wall, plastids, and a vacuole
What tissue allows for plant growth? How is this different than animals?
- Meristem tissue: permanent regions that allow for continuous growth throughout the lifespan of the plant. (similar to a stem cell) (apical meristem tissue found on the tips of roots and stems).
- In animals the majority of all cells are able to reproduce, but are mostly done growing early in the lifespan.
Describe the meristem cell specialization pattern to primary meristems and primary tissues.
- Apical meristem -> Protoderm -> dermal tissue system (epidermis)
- Apical meristem -> Ground meristem -> ground tissue system (ground tissues) (parenchyma, collenchyma, and schlerenchyma)
- Apical meristem -> procambium -> vascular tissue system (primary xylem and primary phloem)
What is the general structure of tissues in a given part of the plant?
Vascular tissue embedded in ground tissue with dermal tissue forming the outer covering.
What are the two anatomical categories and 3 general-types of tissue classification?
- Anatomical: simple – tissue built from one cell type. Complex – tissue built from more than one cell type
- General: dermal, vascular, and ground
Describe the ground tissue system in complete detail (major tissues, cell types w/ function, etc)
- Three major tissues are parenchyma, collenchyma, and sclerenchyma.
- Parenchyma: living protoplasm, most common, have primary cell walls that are flexible (rarely have secondary walls), function to synthesize and store various organic products and to regenerate damaged tissue.
- Parenchyma cell examples include cells that store starch (via leucoplasts) in the stems and roots, the fleshy tissue of most fruit, and photosynthesizing cells in the leaf.
- Collenchyma: living protoplasm, have unevenly thickened primary walls (no secondary walls) which allow for enhanced structure in the young growing parts of the plant (herbaceous, not bark), found just interior to the epidermis in these areas, typically grouped into long strands for expanded support.
- Sclerenchyma: non-living protoplasm, rigid cells which have thickened secondary walls, commonly found in regions of the plant that are no longer elongating, walls are used as a skeleton for support. Two types of sclerenchyma cells exist…
- Fiber cells – long, tapered, and in groups; have a lumen in the center (include hemp in rope and flax fibers in linen). These appear red after a stain with only a small lumen in the center.
- Sclereids – very irregular shapes, impart hardness to nutshells and seeds coats and are gritty texture of fruits, appear red after a stain due to secondary wall.
Describe the vascular tissue system in complete detail (major tissues, cell types w/ functions, etc)
- Two major tissues are xylem and phloem, has as a transport and support role
- Xylem: non-living protoplasm, water and ion transport and support that runs throughout all organs, the protoplast disintegrates leaving only the thickened cell walls behind forming a nonliving tube for water and ion transport, the secondary walls have pits (thinner regions where only primary walls are present) which allow for the horizontal transfer of water.
- Cell types include tracheids, vessel elements, parenchyma cells, and fibers. Tracheids and vessel elements both have secondary walls (used for water transfer). Vessel elements are long tubes linked end-to-end which have perforations (no primary OR secondary walls) to allow for easy fluid transports as well as pits. Tracheids are spindle-shaped cells with pits that allow water to flow from cell to cell (they do not have perforations), they are common to gymnosperms and seedless vascular plants. Both tracheids and vessel elements secondary walls are often deposited as rings or spirals due to organ growth.
- Phloem: living protoplasm. Sucrose, organic compounds, and certain ion transport. Do not have secondary walls. Cell types include sieve elements, sclerenchyma, and parenchyma. Two major transport cells are sieve tube members (elements), and sieve cells which are less specialized food transport cells found in the gymnosperms.
- Sieve tube members are alive at maturity, but lack many organelles (remaining organelles are found pushed up against the wall – smooth ER, some plastids, mitochondria), the end walls between sieve tube members (sieve plates) help the flow of nutrients from cell to cell. All sieve tube members are associated with a companion cell which contains normal living protoplasm and the two are connected by numerous plasmodesmata. The nucleus and ribosomes of the companion cell govern the action of the sieve tube member.
- P-protein (phloem protein) along with callose polysaccharide work together to plug the sieve plates and sieve areas (pores that connect adjacent protoplasts) in response to injury, preventing leakage of nutrients.
Describe the dermal tissue system in complete detail (major tissues, cell types, w/ functions, etc)
- Single layer of tightly packed cells that covers and protects all young parts of the plant. Anatomically and functionally variable. Epidermal cells secrete cutin which forms the cuticle (waxy layer to prevent water loss).
- Guard cells – regulate the opening/closing of stomata (control movement of gas in/out of the plant)
- Trichomes – projections of the epidermis which have many roles (gives fuzzy leaf feeling, facilitates absorption, insulators, counter-insect defense, etc)
- The periderm exists in plants that grow wide (have secondary growth). The epidermis is replaced with a collection of cells called the periderm which is localized to stems and roots (part of bark). Essentially as the epidermis is sloughed off (like human skin) the periderm replaces it. The outer layer of cells are protective cork cells that have walls filled with suberin (lipid compound which creates a waxy outer coating). Lenticels are openings in the periderm that allow for air to pass through the periderm and into the internal tissues.
- The anatomy of the periderm from outside to inside is… 1. Dead epidermis, 2. Cork (phellem) – dead cells with walls filled with suberin, 3. Cork cambium – produces cork to the outside and phelloderm to the inside, 4. Phelloderm – made of living parenchyma cells.