Biology 1424 Exam 1 Notes

Chapters 3, 4, 5, 6

 

CHAPTER 3 CELLS:

 

2.      Robert Hooke first used the term cell for the small cubicles he observed in a thin section of cork in 1665.  Robert Brown was the first to observe name the nucleus in 1835.   Matthias Schleiden and Theodor Schwann proposed the cell theory in 1838-39. Louis Pasteur had many great accomplishments, but in this unit we will recognize his experiments with microorganisms, which conclusively disproved the spontaneous generation of life.   Rudolf Virchow observed the process of cell division and mitosis in the late 1860’s.

3.      The cell theory states that all living things are composed of cells and cell products and that cells are produced by preexisting cells.

4.      Magnification is the apparent increase in size of an object, while resolution is the ability to see the object or the ability to distinguish the distinctness of two distinct points.  Contrast is the ability to distinguish various shades of light and dark or color.

5.      Cell size is determined by the ratio of cell surface area to cell volume. The volume of the cell increases at a faster rate than the surface area of the cell. Volume increases by a power of 3 while surface area increases by a power of 2. Other factors such as cell shape, surface folding or metabolic rate are also involved in size determination.

6.      Cell wall - A rigid non-living wall located outside the cell membrane. In land plants the cell wall is composed of cellulose and hardening materials such as lignin.  Suberin, another material found in the cell wall is a waxy compound that is involved in water proofing some tissues.  The cell wall provides protection and support for the cell.

7.      The primary cell wall is the first wall produced by the plant cell.  It is composed of loosely arranged fibers of cellulose, which allow the cell to grow and stretch.  Young tissues and soft tissues are composed of cells that only have a primary cell wall.  Many mature and hard tissues contain cells with one or more layers of secondary wall are deposited inside the primary wall.  The secondary wall is composed of tightly arranged fibers of cellulose, which are often hardened by lignin.  Secondary walls can be very thick in wood and other supporting tissues.  The living cell produces cell wall material.   In multicellular plants the middle lamella is located between plant cells.  It is often filled with a gel-like material, pectin, which helps cells adhere to each other.

8.      Plasmodesmata are cytoplasmic connections that pass through the cell walls of adjacent cells.  They allow the movement of ions and small molecules from cell to cell.

9.      Membrane function:

a.      PLASMA MEMBRANE

·        Separate the living cell from the nonliving environment.

·        Control or play an active role in the movement of substances into and out of the cell.

·        Sense and interact with the external environment.

·        Involved with cell identity and interactions with other cells.

b.     INTRACELLULAR MEMBRANES

·        Responsible for the structural integrity of most cellular organelles and ultrastructures.

·        Compartmentalizes the cytoplasm, forming unique chemical regions or environments.

·        Provides surface area for the attachment of enzymes and cellular structures such as ribosomes.

·        Involved with numerous biochemical processes.

·        Facilitates transport and secretion through the action of transport vesicles.

10.  The current model for membrane structure is the fluid mosaic model. This model includes the following structural concepts.

·       The primary structural component of cellular membranes are phospholipids which form bilayers when mixed with water. Other membrane lipids include glycolipids and sterols.

·       Embedded within this lipid bilayer are numerous proteins involved with transport, cell identity, recognition and reception.

LIPID BILAYER PROPERTIES:

·         PHOSPHOLIPIDS include two hydrophobic fatty acid tails which are repelled by water, and a phosphate/choline region which is hydrophilic (attracted to water). Phospholipids are amphipathic, meaning they are composed of both non-polar (hydrophobic) and polar (hydrophilic) regions.

·         GLYCOLIPIDS are likewise made up of a non-polar lipid region and a polar region composed of one or more sugars.

·         STEROLS such as cholesterol (animals) and phytosterols (plants) are non-polar except for polar functional groups such as the hydroxyl group.

·         PHOSPHOLIPIDS are organized into bilayers due to the fatty acid regions being repelled by water thus being turned toward each other. The phosphate "heads" are attracted by water thus forming both exposed surfaces. Phospholipids exhibit considerable lateral movement within the membrane, but do not cross from one layer of the bilayer to the other. Movement helps maintain fluidity.

·         STEROLS such as cholesterol are located between the phospholipid tails of the interior of the membrane. This helps keep the lipids from packing together thus becoming less fluid. Sterols help maintain membrane fluidity.

·         GLYCOLIPIDS have their carbohydrate regions exposed at the cell surface, thus they are involved with cell recognition and identity.

MEMBRANE PROTEINS - LOCATION AND FUNCTION:

·         PROTEINS BY LOCATION:

q       INTEGRAL PROTEINS - These proteins are suspended within one layer of the bilayer or they may span the entire bilayer. Integral proteins are exposed on one or both surfaces of the membrane.

q       PERIPHERAL PROTEINS - These are located on the membrane surface, usually loosely associated with an integral protein.

·        PROTEIN FUNCTION:

q       TRANSPORT PROTEINS - Involved with the movement of substances across the membrane.

q       CARRIERS - Bind to specific molecules then change shape moving the molecule across the membrane.

q       CHANNEL PROTEINS - Serve as pores for the movement of ions or small polar molecules across the membrane.

o       REGULATED - Open or close by the action of molecular gate.

o       NON-REGULATED - Continually open.

q       RECOGNITION PROTEINS - Have oligosaccharides attached to the outer surface. Unique for particular cell types. Function as a cellular finger print.

q       RECEPTOR PROTEINS - Serve as binding sites for hormones or other substances that may need to move across the membrane or substances that by binding to the membrane may stimulate or inhibit cellular metabolism.

q       ADHESION PROTEINS - Proteins involved with attachment of the cell surface adjacent cells, tissues, etc.

q       CYTOSKELETAL PROTEINS - Proteins of the cytoskeleton that are associated with or attached to the cell membrane.

11.  The endoplasmic reticulum is a complex network of membrane sheets and vesicles that are found throughout the cytoplasm. and is the most extensive portion of the endomembrane system.. The ER is continuous from the outer layer of the nuclear envelope to the cell membrane.

·     Rough ER

q       Studded with ribosomes on its outer surface.

q       Involved in the synthesis of secretory proteins and membrane

·     Smooth ER

q       Involved in lipid metabolism, the synthesis of lipids, phospholipids and steroids.

q       Involved in cellular detoxification.

q       Active in carbohydrate metabolism..

q       Stores calcium ions necessary for muscle metabolism.

12.   11. Golgi complex or dictyosome - Stacks of membrane vesicles derived from the ER which are involved in the modification, packaging and secretion of cellular products.

13.  Mitochondria - Double membrane bound organelles that serve as the site of aerobic cellular respiration.  The inner membrane is deeply and contains the pigments of the electron transport system.  Between the inner and outer membranes is the intermembrane space and the compartment enclosed by the inner membrane is the matrix.  The roles of these structures will be discussed in the unit on respiration.

14.  Plastids - Double membrane bound organelles unique to plants involved with photosynthesis and storage.

• Proplastids - Disorganized mass of membranes found in unspecialized plant which give rise to mature plastids.
• Chloroplast - Plastid involved with photosynthesis, contains photosynthetic pigments such as chlorophyll.
• Chromoplast - A plastid that contains non-photosynthetic pigments that provide color in plant structures such as flower petals and the skin of ripe fruit. Not involved in photosynthesis.
• Leucoplast - Colorless plastids involved in the storage of compounds such as carbohydrates, lipids or proteins.

15.  Microfilaments - Protein filaments, 7 to 9 nm in diameter, which are involved in cellular movement such as cytoplasmic division, movement of organelles, cytoplasmic streaming, muscle contractions and facilitates cellular shape.  Intermediate filaments - Protein filaments, 8 to 12 nm in diameters, not involved with movement, but provide strength in regions of stress.  Microtubules - Protein tubule composed of spiral chain of protein globules (tubulin) which are involved with cellular movements such as flagella, cellular organelles and chromosomes. Also contribute to the maintenance of cell shape.

16.  The eukaryotic nucleus is surrounded by a two layered nuclear membrane (envelope) which separates the interior of the nucleus from the cytoplasm. The genetic material is dispersed in the nucleus as a complex network of DNA and protein called chromatin. A granular region in the nucleus composed of granules of rRNA is the nucleolus. This is the location of genes that code for the production of rRNA. The fluid portion of the nucleus is the nucleoplasm. Chromosomes are only found in dividing cells. They are composed of DNA organized into short compact structures prior to cell division.

17.  Vacuoles - Membrane sacs that contain various materials such as food, waste, etc.  Plant cell membranes, also called the central vacuole, play a central role in the life of the plant cell.  The central vacuole is involved with turgor, cell growth, the storage of dangerous metabolites, toxins and even pigments involved with color in some flower petals or the skin of certain fruit.  Turgor results from internal water pressure in plant cells due to the diffusion of water into the cell vacuole which pushes outward against the cell wall causing the wall to stretch and become rigid.  Turgor results from plant roots being in contact with soil water which is hypotonic to plant cells. As a result water diffuses into plant cells until the internal physical pressure equals the osmotic tendency (force) to diffuse into the cell.  Turgor is responsible for much of the support and form of soft plant tissues.  As young cells grow, the central vacuole absorbs water causing the cell to elongate.

17.  Prokaryotes vs. Eukaryotes

18.  Plant vs. animal cells.

 

18.  Define the following terms.

a.        Cell Cycle – The life cycle of a cell from division to division, includes both the non-dividing and dividing phases of the cell.

b.        Mitosis  - The division of the nucleus in which daughter nuclei are identical in ploidy to the mother nucleus.

c.         Cytokinesis  - Division of the cytoplasm.    

d.        Chromosome - Condensed DNA protein complex, results from the coiling of strands of chromatin at the beginning of mitosis.

e.        Homologous Chromosomes – Like chromosomes, have genes for the same characteristics located at the same locus.

f.           Chromatids – After a chromosome duplicates it is composed of two identical copies, sister chromatids.

g.        Centromere – The point where two chromatids are joined together.

h.         Kinetochore – A deposit of protein located at the centromere on each chromatid.

i.           Kinetochore Microtubules – A spindle fiber or bundle of microtubules that extends from the mitotic pole to the kinetochore, contract to pull sister chromatids apart during mitosis.

j.           Nonkinetochore Microtubules – Microtubules that extend from the mitotic poles past the mitotic equator of the cell, involved with the elongation of the cell during mitosis.

k.         Haploid - condition in which there is only one set of chromosomes in the nucleus of the cell. This means that the cell has one chromosome of each kind.

l.           Diploid - condition in which there are two sets of chromosomes in the nucleus, that is two chromosomes of each type in the cell.

19.  The cell cycle is the period of time required for the cell to complete one life cycle, that is from one division to the next. The cell cycle includes a nondividing period, interphase, and a dividing period, either mitosis or meiosis. Interphase is divided into three phases, G1, S and G2. G1 is a period of cell growth and a time when the cell is synthesizing necessary nucleotides and proteins for the duplication of DNA. The S phase is the time during which DNA is duplicated, and G2 is a final phase of growth and the synthesis of proteins and materials needed for mitosis. Mitosis is the period or time during which the chromosomes and nucleus is dividing. It is divided into four phases, but requires much less time than interphase.

20.  Mitosis is divided into prophase, metaphase, anaphase and telophase.   Listed below is an outline of the events of each phase.

a.      Prophase

·         Chromosomes coil becoming visible under the light microscope.

·         Chromosomes continue to coil, shortening and thickening, until they become short rod-like structures.

·         Centrosome duplicates with the two centrosomes moving toward opposite poles of the cell to establishing the mitotic spindle. Centrosomes of animal cells contain a pair of rod-like bodies called centrioles.

b.     Prometaphase

·         The nuclear envelope disintegrates.

·         The nucleolus disappears.

·         Kinetochore microtubules (spindle fibers) extend from each centrosome and attach to the kinetochore of the centromere of each duplicated chromosome.

·         Each duplicated chromosome consist of two complete copies of the original chromosome. Each copy is a chromatid, with the two sister chromatid being attached at the centromere.

·         Then microtubules pull on the chromosomes from each pole causing considerable agitation as the chromosomes move toward the center of the mitotic spindle.

·         Non-kinetochore microtubules extend from mitotic pole to pole, ultimately pushing the poles apart causing the cell to elongate.

c.      Metaphase

·         Centromeres move to the equatorial plane of the cell (metaphase plate). This is a plane equidistant between the mitotic poles and perpendicular to the axis of the mitotic spindle.

·         Non-kinetochore microtubules push the mitotic poles apart elongating the cell.

d.     Anaphase

·         Anaphase begins as the chromatids separate at the centromere. Each sister chromatid becomes an independent chromosome and sister chromatid moves to opposite poles of the cell, thus sister chromatids ends up as chromosomes in different nuclei at the conclusion of mitosis.

·         Chromosomes continue to move to the poles of the cell as kinetochore microtubules shorten.

e.      Telophase

·         Telophase is more or less the opposite of prophase.

·         Chromosomes collect in dense clumps at the poles of the cell.

·         Chromosomes begin to uncoil, dispersing into the chromatin network.

·         Nuclear envelope regenerates.

·         Nucleolus reappears.

·         The cytoplasm usually divides in a process called cytokinesis.

CHAPTER 4 TISSUES:

1.        Meristems are composed of cells that retain the ability to divide.  Simple tissues are composed of only one cell type while complex tissues contain several different cell types.

2.        Apical meristems are located at the tips of the stems and roots.  The vascular cambium and cork cambium are lateral meristems that produce lateral growth.  The vascular cambium produces secondary xylem to the inside and secondary phloem to the inside, while the cork cambium produces the cork cells of the outer bark of woody roots and stems.  Tissues produced by a cambium are secondary tissues while those produced by meristems are secondary tissues.  An intercalary meristem is located at the base of the stem or at the nodes of plants that do not have an apical meristem and produces growth in length.  Note that the vascular cambium is only in dicots, and that the cork cambium only in woody plants.

3.        Recognize that primary tissues are derived from the cells produced by an apical or intercalary meristem and that secondary tissues develop from cells produced by a cambium or other lateral meristem like the cork cambium.

4.        Parenchyma cells are large, thin walled (primary cell wall only), living cells at maturity.  They are involved with photosynthesis and storage.  The photosynthetic cells of the leaf are parenchyma cells called chlorenchyma.  Collenchyma, also living at maturity have some thickening of the secondary cell wall.  Collenchyma cells provide support or protection in regions of stress, are involved with storage and even photosynthesis in some cases  Sclerenchyma tissue is composed of cells that are usually non-living at maturity.  They have very thick cell walls and provide support, strength and protection.  Sclerids are small somewhat round cells with very thick cell walls, while fibers are very long.

5.        The epidermis is a simple tissue usually only one cell thick.   It is an outer protective layer of cells found on non-woody roots, stems and leaves.  Root hairs are extensions of individual root epidermal cells that greatly increase the absorptive surface area of the root.  The periderm is the corky bark of woody roots and stems.  It is composed of several layers of cell and includes the cork cambium and cork.

6.        The cutical is a waxy layer on the outer surface of the epidermis of leaves and stems.  Cutin is the waxy material that makes up the cuticle.  Stomata are openings in the epidermis of leaves and stems that functions in gas exchange.  Guard cells are a pair of cells that form the stomata.  Guard cells can change shape to open and close the stomata.  Lenticels are openings in the bark of woody stems that allow gas exchange.  Cork cells are non-living at maturity and make up the outer portion of the woody bark.   Suberin is a waxy material in the cell walls of cork cells that makes them waterproof.  and root hairs.

7.        Xylem is a complex vascular tissue involved with structural support and the transport of water and minerals upward in plants.  The functional elements in xylem are tracheids and/or vessels.  Functional xylem cells are non-living at maturity, have thickened secondary cell walls and provide passage ways for the transport of water and minerals.  Tracheids are long thin cells with tapering end walls.  Water moves through pits as it passes from tracheid to tracheid.  While tracheids are more common in more primitive plants, vessels are common in more advanced plants.  Vessels are usually larger in diameter, stacked end to end and have reduced or no end cell walls.  Xylem tissue also contains parenchyma cells and fibers.

8.        Phloem is a complex, vascular tissue that functions in the transport of foods in plants.  Sieve tube elements are the functional elements that transport food.  They are living at maturity, have no nucleus, are stacked end have perforated end cell walls called sieve plates.  Companion cells are small cells located along the side of sieve tube elements.  Companion cells have a nucleus and provide for the nuclear needs of sieve tube elements.  There are numerous plasmodesmata that connect companion cells and sieve tube elements.  Like xylem phloem tissue also contains parenchyma cells and fibers.

 

CHAPTER 5 ROOTS:

1.        Root systems are involved with anchoring the plant into the ground, absorption of water and minerals from the soil, food storage, water storage and reproduction.

2.        The radicle of the plant embryo produces the root.

3.        A fibrous root system is one that does not have one primary of main root, but is made up of many branching roots of more or less equal size.   In tap root systems there is usually one primary or main root that usually grows more or less straight down with smaller lateral or branch roots developing from it.

4.        Adventitious roots are roots that grow from stems or leaves; they develop from tissues other than roots.  Root hairs are extensions of individual root epidermal cells that greatly increase the absorptive surface area of the root.

5.        There is considerable development of cells and tissue that occurs in the first inch of the root tip.  Starting at the tip of the root we will explore each tissue and their functions.  The root cap is a cap-like layer of cells that develops over the tip of the root.  It provides protection from abrasion by soil p[articles and secretes a lubrication fluid that allows the root tip to more easily push through the soil.  Cells of the root cap and of the remainder of the root are produced by the apical meirstem that is located above the root cap.  Cells of the apical meristem retain the ability to divide, thus they produce the cells of the root cap and all primary growth in the root.  The Region of Elongation is just above the apical meristem, and is a region where cells elongate or grow rapidly.  It is this region that produces all growth in length.  Above the region of elongation is the Region of Maturation where cells mature into the mature and functional tissues of the root.

6.        The root hair zone is in the region of maturation.  Root hairs are extensions of individual root epidermal cells that greatly increase the absorptive surface area of the root.

7.Listed below is a comparison of the characteristics of monocots and dicots    which are the two classes of flowering plants.

 

Monocots	Dicots
One Cotyledon	Two Cotyledons
Narrow Leaves	Broad Leaves
Parallel Veins	Netted Veins
Floral Parts in 3’s	Floral Parts in 4’s or 5’s
Most Advanced

                                   

7.        Monocot roots have a central pith where dicot roots have a solid core of xylem.  Additionally bundles of xylem are located in a ring near the outside of the stele.  Bundles of phloem are located between and to the outside of the xylem and there is no vascular cambium in the roots of monocots.  The stele is the central cylinder of the root that contains the vascular tissue; it includes the tissues inside the endodermis.  Dicots have a solid core of xylem and no pith.  Phloem is found between the radiating arms of xylem and the vascular cambium is found between the xylem and phloem of the dicot root.  Both the monocot and dicot have a pericycle located just inside the endodermis.  Observe photos or diagrams of cross sections of monocot and dicot roots for a good comparison.

8.        The epidermis is an outer protective covering of cells on the outside of the root.  Near the root tip root hairs develop as extinctions of epidermal cells.  The cortex made up of the epidermis cortex parenchyma and the endodermis.  The cortex parenchyma is a region of large parenchyma cells located between the epidermis and endodermis.  The cortex parenchyma is involved with the transport of water across the root, food storage and water storage.  The endodermis is the inner most layer of the cortex.  The lateral surfaces of endodermal cells contain a waxy region the Casparian strip that prevents the movement of water through the cell walls of the endodermis.  As a result water must pass through the cytoplasm of the endodermal cells allowing control on the movement of ions and water into and out of the stele.  Some endodermal cells do not have a Casparian strip and sereve as passage cells that allow a rapid flow of water and minerals into the stele.  Ceel of the pericycle are meristematic and produce branch or lateral roots.  The pith, if present, is composed mostly of parenchyma cells involved with food storage.

9.         Specialized roots are identified and pictured in your text.  Please refer to the text for this information.

10.    The term mycorrhizae means “fungus root”, thus this is a mutualistic symbiotic association between the roots of most vascular plants and certain fungi.  The fungus assist the plant by increasing the absorption of water and minerals, especially phosphorus, from the soil.  In turn the roots provide food for the fungus.  Root nodules are not-like growth of root tissue causec by an infection of nitrogen fixing bacteria.  This is another mutualistic symbiotic association.  In this association the bacteria convert atmospheric nitrogen into nitrogen compounds which plants use in their matabolism and the bacteria receive food from the association.

 

CHAPTER 6 STEMS:

1.        Stems function in the transport of water, minerals and food; support, food and or water storage, leaf display, reproduction and the development and support of the shoot system.

2.        The following structures are common external features of a woody stem.  The terminal bud is located at the stem tip.  It is made up of leaf scales, embryonic leaves and the apical meristem.  Scales protect the delicate tissues of the apical meristem.  As one moves down the stem from the terminal bud we encounter slightly enlarged areas called nodes.  Nodes are regions of growth that produce leaves and lateral stem growth.  Bundles of meristematic tissue are lacated at the nodes.  These bundles of meristematic tissue produce lateral or axillary buds that produce leaves and lateral stems.  Leaf scars are also located at the node.  This is the point where last season’s leaf broke from the stem.  With in the leaf scar are leaf bundle scars where vascular bundles passed from the stem to the leaf petiole.  The space between two nodes if an internode.  The length of the internodes varies and is designed to separate and display the leaves for phothsynthesis.   Lenticels are located along the stem surface.  These are small raised areas in the bark that allow gas exchange.

3.        A longitudinal section of a stem tip will show many embryonic and developing tissues.   Observe drawings and photos in your text and lab handouts for location and appearance.  The apical meristem is composed of mitotic cells that produce the primary tissue of the stem.  The protoderm is the embryonic epidermis. The procambium develops into the vascular cylinder and the ground meristem matures into the cortex and pith.  Bud primordial and leaf primordial are embryonic buds and leaves that will mature as the stem grows.     <![endif]> 

4.        Observe drawings and photos of herbaceous dicot, woody dicot and monocot stem.  Be able to describe the anatomical differences.  Herbaceous dicots do not have any woody tissue.  Vascular bundles form a ring near the outside of the stem.  Herbaceous dicots have a large pith inside the ring of vascular bundles.  The vascular bundles of herbaceous dicots usually have a protective cap of fibers on the outside that provides support and protects the bundle from damage and herbivory.  The vascular bundles of woody dicots grow in contact with each other as the stem develops, thus forming a solid region of xylem, the wood of the plant.  Xylem is a complex tissue with parenchyma rays (xylem ray) involved in lateral transport and fibers involved with support.  Woody dicots have a vascular cambium that separates the xylem from the phloem.  The phloem is the inner bark while the cork and cork cambium form the outer bark.  As described earlier phloem is a complex tissue containing alternating layers of functional phloem and phloem fibers.  Regions of functional phloem and phloem fibers are separated from each other by phloem rays (cortex) made up of parenchyma cells.  Monsocot stems have vascular bundles scattered through out the stem, but more concentrated near the outside.  The vascular bundles of the monocot do not have a vascular cambium.  Even though there is a considerable amount os parenchyma tissue in the stem it is not divided into a cortex and pith but is simply the parenchyma.  There is no woody tissue associated with the monocot stem.

5.        Primary xylem is derived from the apical meristem, while secondary xylem is produced you activity of the vascular cambium.  Monocots have no secondary tissue.  Annual ring are rings in the xylem of woody plants produced by alternating bands of large xylem cells (spring wood) and small xylem cells (summer wood), thus in temperate regions annual rings correspond to years.  In the tropics rings form, but do not correspond to years, but more likely variations in growing conditions. Identify the function of each of the specialized stems listed on the slide, “Specialized Stems”.

6.        Specialized stems are identified and pictured in your text.  Please refer to the text for this information.