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3 – 25 – 99 /1st lecture for Test three/Tuesday Introduction to PLANTS Chapter 18 p. 348 - 359

Fungi are not always harmful to plants. Some play a benefactor role such as the Mycorrhizal fungus. Together, the root of a tree and the fungus form an intimate, mutually beneficial association called Mycorrhiza. The fungi absorb phosphorus and other essential minerals from the soil and these nutrients are then available to the plant. The sugars produced by the plant nourish the fungi. The fungi can make a tree more resistant to disease, thereby reducing the need for pesticides that kill disease causing organisms. But citrus growers use fungus killing chemicals to control fungi that cause diseases. Plants transformed the landscape, creating new environmental opportunities for protists and prokaryotes and making it possible for herbivorous animals and their predators to evolve on land. What is a PLANT? Plants are multicellular eukaryotes that make up organic molecules by photosynthesis. Algae is a separate kingdom. Algae is adapted for aquatic life while plants live on the terrestrial land. The entire algae body has direct access to water and obtains CO2 and minerals from the water. The aquatic ancestors of plants changed drastically as they became adapted to the challenges of living on land. One such challenge is loss of water to the air. Helping plants retain water is a waxy CUTICLE that covers their aerial parts (stems and leaves). Gas exchange cannot occur directly through the cuticle, but CO2 and O2 diffuse across the leaf surfaces through tiny pores called STOMATA. A plant must be able to obtain chemicals from both soil and air, two very different media. A plant must be able to hold itself upright, because air holds no support. Its roots help do both these challenges. The roots provide anchorage and absorb water and mineral nutrients from the soil. Mycorrhizae greatly enhance this absorption. Some plants have a type of immortality like the redwoods. There is no reason for their cells to die out. They can divide continuously forever (Meristematic Tissue). McClure’s Chalkboard outline • Algae • Ferns (Vascular plants) • Mosses/Bryophytes • Gymnosperms/Conifers • Angiosperms (Flowering plants)

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While obtaining light and chemicals from the environment, a plant must be able to conduct water and minerals upward from its roots to its leaves and to distribute sugars produced in the leaves throughout its body. Performing these functions, a network of narrow tubes, the vascular system, extends throughout the plant body. The vascular system is divided into two types of tissue. • Xylem – made out of dead cells forming microscopic pipes that convey water and

minerals up from the roots. • Phloem – Consists of living cells and distributes sugars throughout the plant. Algae

have no comparable transport system. Algae is in the Kingdom Protista. Both plants and many algae produce gametes in gametangia, structures that consists of protective jackets of cells surrounding the gamete – producing cells. PPLLAANNTT DDIIVVEERRSSIITTYY PPRROOVVIIDDEESS CCLLUUEESS TTOO TTHHEE EEVVOOLLUUTTIIOONNAARRYY HHIISSTTOORRYY OOFF

TTHHEE PPLLAANNTT KKIINNGGDDOOMM p. 350 Two distinct lineages arose from ancestral plants 425 million years ago. One of these lineages gave rise to modern plants called Bryophytes, a group that includes the mosses. Bryophytes lack xylem and phloem. The other lineage of plants, the Seedless Vascular Plants have xylem and phloem as well as embryonic development within gametangia. Their vascular tissues provide support, enabling stems to stand upright and grow tall on land. Then the vascular plants separated into the Gymnosperms (Conifers, cone bearing) and the Angiosperms (seed flowing Plants) 360 million years ago. The seed plant lineage accounts for nearly 90% of the approx. 265,000 species of living plants. Seed plants have adapted well to become successful. These plants make seeds, which do not require a water layer for fertilization. Instead of producing sperm that swim to the eggs, they produce pollen, a vehicle that transfers nonflagellated sperm forming cells to the female parts of the plant. Pollen is carried passively by wind or animals and the arrival of pollen at the female is called Pollination. Among the earliest seed plants were the gymnosperms. Their seed is said to be naked because it is not contained in a fruit. Today the conifers, pine, spruce, fir, and many other needlelike leaves are the largest group of gymnosperms. About 130 million years ago the flowering plants or angiosperms diverged from the gymnosperm lineage.

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In summary, Four key adaptations for life on land mark the main lineages of the plant kingdom. 1. Gametangia, which protect against gametes, zygotes and embryos from dying out,

are present in all plants. 2. Vascular tissues (phloem and Xylem) mark a lineage that gave rise to most modern

plants. 3. Seeds appeared in a lineage that dominates the plant kingdom today 4. Flowers mark the angiosperm lineage, which is the dominant group of seed plants.

HAPLOID AND DIPLOID GENERATIONS ALTERNATE IN PLANT LIFE CYCLES Plants have life cycles very different from ours. Each of us is a diploid individual. The only haploid stages in the human life cycle are the sperm and eggs. Plants have alternating generations: Diploid (2n) individuals called SPOROPHYTES and haploid (n) individuals called GAMETOPHYTES generate each other in the life cycle.

MOSSES HAVE A DOMINANT GAMETOPHYTE Gametes develop in gametangia on the gametophytes. The flagellated sperm require a film of water in which to swim to the egg, which stays in its gametangium on the gametophyte. After fertilization, the zygote remains in the gametangium. There it divides by mitosis and develops into a Sporophyte. Meiosis occurs in the sporangia at the tips of the sporophyte stalks. Haploid spores resulting from meiosis are released. Later they undergo mitosis and develop into Gametophytes, completing one life cycle. In mosses, the gametophyte is said to be Dominant because it is larger, and the sporophyte depends on it for nourishment. In nearly all other plants, the sporophyte is dominant, with the gametophyte usually depending on it for nourishment.

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FERNS, LIKE MOST PLANTS, HAVE A DOMINANT SPOROPHYTE The life cycle of a fern illustrates a dominant sporophyte generation. All we usually see in a fern is the sporophyte. Fern gametophyte often have a distinctive heart – like shape. Like mosses, ferns have a flagellated sperm that requires moisture to reach the egg. The zygote remains on the gametophyte, where it develops into a Sporophye. Cells in sporangia undergo meiosis, producing haploid spores. These spores, in turn, develop into gametophytes by mitosis. Today, about 95% of all plants, including all seed plants, have a dominant sporophyte generation in their life cycle. As seed plants evolved, their dominant sporophyte became adapted to house all plant’s reproduction stages. The evolution of pollen, produced by the dominant sporophyte was key step in the adaptation of seed plants to dry land. By providing transport for sperm – producing cells, pollen makes it possible for sperm to reach and fertilize the eggs without being in water.

Gymnosperms called Conifers, cone bearing, replaced the swamp forests Of the earliest seed plants, the most successful were the gymnosperms. The group of gymnosperms that prevailed after the swamps dried up and that is still dominant among the gymnosperms today is the conifers – naked seed plants that produce cones. The pine tree is a typical conifer.

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A Pine tree is a Sporophyte with tiny gametophytes in its cones A pine tree is itself a sporophyte; the gametophyte generation consists of microscopic stages that grow inside the tree’s cones. A pine tree bears two types of cones. The hard, woody ones we usually notice are female cones. The female cone has many hard radiating scales, each bearing a pair of Ovules. Male cones are generally much smaller than female cones; they are also soft and short-lived. Each scale on the male cone produces many sporangia, each of which makes numerous spores by meiosis. Male gametophytes, Pollen Grains, develop from spores. When male cones are mature, the scales open and release a cloud of pollen. Pollen grains house the cells that will develop into sperm. Pollination occurs when a pollen grain lands in the ovule, and a haploid spore cell begins developing into the female gametophyte. Not until months later do eggs appear within the female gametophyte. A tiny tube grows out of the pollen grain and eventually releases sperm into the egg. Fertilization does not occur until more than a year after pollination. Following fertilization, the zygote develops into a sporophyte embryo and the whole ovule transforms into a seed. The seeds fall to the ground or dispersed by wind or animals. When conditions are favorable, it germinates. Eventually it will turn into a tree. In Summary, all the reproductive stages of conifers are housed in cones borne on sporophytes. The ovule is a key adaptation – protective device for all the female stages in the life cycle as well as the site of pollination, fertilization and embryonic development. The ovule becomes the seed, a major factor in the success of the cones and the flowering plant on land.

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Angiosperms dominate most landscapes today Today, worldwide, there are about 400 times more species of Angiosperms than gymnosperm, and nearly 80% of all plants are angiosperms. Whereas gymnosperms supply most of our lumber and paper, Angiosperms supply nearly all our food and much of our fiber for textiles.

The FLOWER is the Centerpiece of Angiosperm and Reproduction A flower is actually a short stem with four sets of modified leaves called Sepals, Petals, Stamens and Carpals. At the bottom of the flower are the Sepals. The Petals are the “pretty” part of the flowers that attract birds to it for pollination. The actual reproductive structures are multiple stamens and one or more carpels. Each Stamen (male) consists of a stalk with an ovary at the base and a sticky tip known as the Stigma (female), which traps pollen. The ovary, in which the eggs develop. As we see in the next modules, a seed develops from each ovule, and the fruit develops from the ovary. From lecture: Algae have no heating problems. They get nutrients by diffusion. There is no problem with gravity. In kelps, there are floatation devices on them. They need to get the maximum surface area to get the sun’s rays. No roots or vessels. They are Non – vascular. They are firmly held to rocks. They get Oxygen from the water and give off wastes. They are Unicellular.

The Angiosperm plant is a Sporophyte with Gametophytes in its flowers Meiosis occurs in the anthers of the flower and lead to the male gametphytes or pollen grains. Meiosis in the ovules leads to the female gametophyte, each of which produces an egg. Pollination occurs when a pollen grain, carried by the wind or an animal, lands on the stigma. As in gymnosperms, a tube grows from the pollen grain to an egg. And a sperm fertilizes the egg creating a zygote. A seed develops from each ovule. Each seed consists of an embryo ( a new sporophyte) surrounded by a store of food and a seed coat. While the seed develops the ovary’s wall thickens, forming the Fruit that encloses the seeds. Fruits help disperse the seeds. An animal will eat it and digest the seed. When conditions are favorable, the seed germinates and the embryo grows into a mature Sporophyte, completing the life cycle of a Flowering Plant. A FRUIT, the ripened ovary of a flower, is a special adaptation that helps disperse seeds. Some angiosperms depend on wind for dispersal. The fruit of flowering plants usually develops and ripens so quickly, so the seeds can be produced and dispersed in a single growing season. The dispersal of seeds in fruit is one of the reasons angiosperms are so numerous and widespread.

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4 – 6 – 99 /2nd lecture for Test three/Tuesday Continue w/the introduction to PLANTS – Chapter 31

Chapter 31 Another essay question will be, “Explain Double Fertilization in flowering plants.” About 10 points. Explain both haploid/diploid life cycles for full credit. Plants have a haploid and diploid generation that they rotate during their cell stages. Mosses started as gametophytes then sporophytes took over.

There are Two Major Groups of Angiosperms: MONOCOTS & DICOTS Angiosperms have dominated the land for over 100 million years and there are about 235,000 species of flowering plants living today. Plant biologists classify angiosperms in 2 groups, called monocots and dicots, on the basis several structural features. The words “monocot” and “dicot” refer to the first leaves that appear on the plant embryo. These embryonic leaves are called seed leaves or cotyldons. A monocot embryo has one seed leaf; a dicot embryo has two seed leaves. Monocot stems have Vascular tissue, tissues that transport water and nutrients, arranged in a complex array of bundles. The flowers of most monocots have their petals

and other parts, in multiples of 3. The ROOTS of MONOCOTS form a fibrous system – a mat of threads – that spreads out below the soil surface. With most of their roots in the top few centimeters of soil, monocots, especially grasses, make excellent ground cover that reduces erosion. Most angiosperms are DICOTS. This group includes most shrubs and trees, except the conifers. Dicot leaves have a multibranched network of veins and dicot stems have a vascular bundles arranged in a ring. The dicot flower has petals in multiples of four or five. The large, vertical root of a dicot, known as a taproot, goes deep in the soil.

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THE PLANT BODY CONSISTS OF ROOTS AND SHOOTS p. 610 Among the evolutionary adaptations that made it possible for plants to move onto land were the ability to take up water and minerals from the soil, to absorb light and take in CO2 from the air for photosynthesis and to survive dry conditions. Neither the root nor the shoot can survive without the other. Lacking chloroplasts and living in the dark, the roots would starve without sugar and other organic nutrients transported from the photosynthetic leaves of he shoot system. PlANT CELLS AND TISSUES ARE DIVERSE IN STRUCTURE AND FUNCTION Plant cells are unique in several ways. Many have chloroplasts, which contain the photosynthetic pigment chlorophyll. Mature plant cells often have a large vacuole. A plant tissue composed of more than one type of cell is called a complex tissue. The vascular tissues of plants – tissues that conduct water and food – are complex tissues. Vascular tissue called XYLEM contains water – conducting cells that convey water and dissolved minerals UPWARD from the roots. Vascular tissue called PHLOEM contain sieve – tube members that transport sugars from the leaves or storage tissue to other parts of the plant. Food conducting cells AKA Sieve – Tube Members are arranged end to end forming tubes.

PRIMARY GROWTH LENGHTENS ROOTS AND SHOOTS Most plants continue to grow as long as they live, a condition known as indeterminate growth. Most animals are characterized by determinate growth – they cease growing after reaching a certain size.

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p. 620 Overview: The Sexual life cycle of a Flowering Plant In flowering plants, the structure specific to reproduction is the flower. A flower is actually a compressed shoot and its main parts, the sepals, petals, stamens and carpels are modified leaves. The Sepals are usually green and look more like leaves than the other flower parts. The Petals are often the bright and colorful – so it can advertise itself to insects and other pollinators. The Flower’s reproductive organs are the stamens and carpel. The STAMENS are male. At the tip of each stamen is an anther, a sac in which pollen grains develop. Pollen grains house the cells that become sperm. The carpal is the female organ of the flower. The tip of the carpel, the stigma, is the receiving surface for pollen grains brought from other flowers, or from the same flowers, by wind or animals. The base of the carpel is the OVARY, which houses the reproductive structure called the OVULE. The OVULE contains the developing egg and cells that support it.

p.620 THE DEVELOPMENT OF POLLEN AND OVULES CULMINATES IN FERTILIZATION

Recall that the life cycles of all plants include alternation of haploid (n) and diploid (2n) generations. The DIPLOID plant body is called the SPOROPHYTE. A Sporophyte produces special structures, the anthers and ovules in angiosperms, in which cells undergo meiosis. The resulting haploid cells then divide mitotically and each becomes a multicellular, GAMETOPHYTE, the plant’s HAPLOID generation. At fertilization, the male and female gametes unite, producing a diploid zygote. The life cycle is completed when the zygote divides by mitosis and develops into a new sporophyte. We begin with the development of the MALE gametophyte, the pollen grain which are located in the male anthers. Each cell first undergoes meiosis, forming four haploid cells called spores. Each spore then divides by mitosis forming two haploid cells, called the Tube Cell and the Generative Cell. A thick wall forms around these cells and the resulting pollen grain is ready for release from the anther.

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Then on the FEMALE side: We follow the development of the flower parts that form the female gametophyte and eventually the egg. In most species, the ovary of a flower contains several ovules. An ovule contains a central cell surrounded by a protective covering of smaller cells. Then central cell enlarges and undergoes meiosis, producing four haploid cells. Three of these cells usually degenerate, but the Surviving One ( Called the Spore) enlarges and divides mitotically, producing a multicellular structure called the Embryonic Sac. Housed in several layers of protective cells produced by the sporophyte plant, the embryo sac is the female gametophyte. The sac contains a large central cell with two haploid nuclei. One of its other cells is the haploid egg, ready to be fertilized.

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POLLINATION The first step leading to fertilization is pollination – the delivery of pollen to the stigma of a carpel. Most angiosperms are dependent on animals to transfer their pollen. After pollination, the pollen grain germinates on the stigma. Its tube cell gives rise to the pollen tube, which grows downward into the ovary. Meanwhile, the generative cell divides mitotically, forming two sperm. When the pollen tube reaches the base of the ovule, it enters the embryo sac through a pore and discharges both its sperm. One sperm fertilizes the egg forming the Zygote. The other sperm contributes its haploid nucleus to the large central cell of the embryo sac. This cell, now with a triploid (3n) nucleus, will give rise to tissue that nourishes the embryo that develops from the zygote. The formation of both a zygote and a cell with a triploid nucleus is called DOUBLE FERTILIZATION. This occurs only in plants, mainly in angiosperms. Then comes the fruit stage…

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THE OVULE DEVELOPS INTO A SEED After fertilization, the ovule containing the triploid central cell and the zygote, begins developing into a seed. The triploid cell divides and develops into a nutrient – rich multicellular mass called the endosperm. The endosperm nourishes the embryo until it becomes a self-supporting seedling. The zygote divides mitotically repeatedly. The result of embryonic development in the ovule is a mature seed. The ovule’s coat has lost most of its water and has formed a resistant SEED COAT that encloses the embryo and its food supply, the ENDOSPERM. When you split the seed of the monocot and dicot, you can see a difference in structure. In the bean, a dicot, the embryo is an elongated structure with two fleshy cotyledons. The embryonic root develops just below the point at which the cotyledons are attached to the rest of the embryo. The bean seed contains no endosperm, because its cotyledons absorb the endosperm nutrients as the seed forms. The nutrients pass from the cotyledons to the embryo when it germinates. The kernel of corn, a monocot, is actually a fruit containing one seed. Everything is the seed, except the coat which is the fruit dried over it. The corn seed contains a large endosperm and a single cotyledon. FRIUTS, one of the most distinctive features of angiosperms, develop at the same time seeds do, but from the outer Ovary.

THE OVARY DEVLOPS INTO A FRUIT A FRUIT is a thickened Ovary! The fruit is specialized as a vessel that houses and protects seeds and helps disperse them from the parent plant. A corn kernel is a fruit, as is a peach or pineapple. Pea pod to a pea plant. The wall of the ovaries becomes the pod. The ovules develop into the seeds. In an apple for example, the part we discard, the CORE, is a thickened OVARY and therefore the true fruit. Apples, pea pods are simple fruits – those that develop from a flower with a single carpel and ovary. A Multiple fruit, a pineapple, develops from a group of separate flowers tightly clustered together. When the walls of the ovaries start to thicken, they fuse together and become incorporated into one fruit. Each of the pineapple’s many parts develops from a separate flower.

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• Describe Cellular Respiration Each cell must maintain its own energy supply by oxidizing glucose molecules to produce ATP, adenine triphosphate. This occurs in three main stages. The first stage is glycolysis which begins in the cytoplasm with the breakdown of a 6 – Carbon sugar molecule by expending 2 ATP’s. A net 2 ATP results when 2 pyruvic acid is formed and 4 NADH move onto the Electron Transport Chain. The 2 pyruvic acids diffuse into the mitochondria where each pyruvic acid loses a C atom and an Acetyl coenzyme A (CoA) is attached on to it. 2 carbons enter the Krebbs Cycle when the CoA splits off to be recycled and the 2 C attaches on to a 4 C molecule. As it passes through the cycle 2 ATP, 3 NADH & 1 FADH are produced for each CoA. So 4 ATP, 6 NADH & 2 FADH are produced for one glucose molecule. The 6 NADH & 2 FADH enter the Electron Transport Chain. NADH & FADH lose their electrons to the ETC. NADH acts as a shuttle for electrons to travel down the ETC. At the end of the ETC the electrons form water. As the electrons move down the chain Hydrogen ions are released from the matrix into the intermembrance space. Like water behind a dam, they build up a higher gradient outside until they are funneled back into the matrix through the ATP Synthase channel. This channel has an enzyme that catalyzes the phosphorylation of ADP to form ATP as the H ions move down the ATP Synthase. This results in 34 ATP to form a grand total of about 36 ATP for each glucose molecule.

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Describe Double Fertilization in Angiosperms/Flowers In Double Fertilization of an angiosperm, sperm fertilizes the egg in the ovary and another sperm joins with a large central cell with two haploid nuclei in the flower’s embryonic sac to become an outer covering called endosperm. Pollen is taken from an anther of one plant to the stigma of another plant by wind or an animal. Male gametophytes in the anther under meiosis to form 4 haploid spores, then each spore divides mitotically to form 2 cell haploid cells. A thick wall forms around this grain. Now it is ready to be transported off. The Stigma is the female part of the plant. Down in the ovaries, the ovule contains a central cell. This central cell undergoes meiosis, producing 4 haploid cells. One cell survives and divides mitotically, producing a multicellular structure called the Embryonic Sac, the female gametophyte. The sac contains a central cell with 2 haploid cells and the haploid egg. In pollination, a pollen grain is delivered on a stigma, which grows a pollen tube down into the ovary. Then the sperm divides mitotically to form 2 sperms. When the tube reaches the Embryonic Sac, one sperm fertilizes the egg while the other fertilizes the central cell, now a triploid cell (3n). The Zygote divides mitotically to turn into a mature seed. The triploid cell develops into a seed coat called the endosperm that encloses the embryo. The fruit develops at the same time the seeds do & surrounds the endosperm. The fruit is a thickened ovary that protects the seeds and aids in their disbursement.

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4 – 8 – 99 /3rd lecture for Test 3/Thursday Continue w/PLANTS Monocots/Dicots & Growth – Chapter 31

Chapter 6 ATP Production

p.613 Vascular tissue called XYLEM contains water – conducting cells that convey water and dissolved minerals upward from the roots. Vascular tissue called PHLOEM contains sieve – tube members that transport sugars from leaves or storage tissues to other parts of the plant.

PRIMARY GROWTH LENGTHENS ROOTS & SHOOTS Most plants continue to grow as long as they live, a condition known as indeterminate growth. Most animals are characterized by determinate growth – we cease growing after a certain size. Indeterminate growth in all plants is made possible by tissues called Meristematic Tissue (teacher’s term) – Meristems (text term). A meristem consists of unspecialized cells that divide and generate new cells and tissues. Meristems at the tips of roots and in the terminal (top) and axillary buds of shoots are called apical meristems. Cell division in the apical meristems produces the new cells that enable a plant to grow in length. The lengthwise growth produced by apical meristems is called primary growth, 10 This accounts for the tall growth in such trees as the Sequoia.

Secondary growth increases the girth of woody plants. An increase in a plant’s girth is called secondary growth. Happens in trees and dicots. Seen in trees, shrubs, and vines whose stems last from year to year and consist mainly of thick layers of dead tissue, called wood. The vascular cambium has given rise to two new tissues, one is the secondary xylem, next to the inner surface of the vascular cambium. The other is the secondary phloem, just outside the vascular cambium. The secondary xylem makes up the wood of a tree, shrub or vine. Tree cutters cut at the phloem area so the tree will eventually die. No sugar is being transported to the leaves. The tree conservationist put metal rings inside the tree to stop them.

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p.86 Chloroplasts & mitochondria make energy available for cellular work. These Two organelles are both composed of membranes with enzyme assembly lines. Chloroplasts in photosynthetic organisms use solar energy to make glucose from carbon dioxide and water. In this process, light is converted to chemical energy and oxygen escapes as a by product. Mitochondria present in all eukaryotes, consume oxygen in cellular respiration, using the chemical energy stored in glucose to make ATP. We get most of our energy from the sun. Choloroplasts in plants and photosynthetic protists convert light energy to chemical energy. NO ANIMAL CAN DO THIS. Energy does not recycle. In carrying out the activities of life, we lose energy in the form of heat. Because heat cannot be used to make ATP we have to make our own. Organisms must be constantly supplied with energy. Every cell has to make its own ATP. Plants and animals have mitochondria. ATP can be stored for later use. Root cells have ATP to use sugar.

Cellular Respiration banks energy in ATP molecules

Harvesting energy is the fundamental function of cellular respiration. This equation indicates that the starting (reactant) molecules glucose and oxygen come apart and their atoms regroup to form the products CO2 & H2O. In the process, glucose releases chemical bond energy, which the cell stores in the chemical bonds of ATP.

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Our whole metabolism is based on building and tearing covalent bonds. We are based

on digesting glucose. Essay will be: What happens in the mitochondria & cytoplasm The electrons are key in photosynthesis. Photosynthesis will be matching

ATP – 3 Phases • GLYCOLYSIS – Splitting of glucose which occurs in the cytoplasm. • KREB CYCLE/ CITRIC ACID Cycle – occurs in the mitochondria • Electron Transport System occurs in the mitochondria.

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4 – 13 – 99/Tuesday 4th lecture for test3

TRANSPIRATION IN TREES/PHOTOSYTHESIS

Water transport system p. 632. Xylem has thick walls. How do we get water up into the trees many feet up without a pump. Because the xylem vessels are continuous. The solution of inorganic nutrients in a plant’s xylem tissue, called xylem sap, flows all the way up from the center of the root to the tips of the leaves in these tubes. The root cells actively pump inorganic ions into the xylem and the root’s endodermis holds the ions there. As ions accumulate in the xylem, water tends to enter by osmosis, pushing xylem sap upward ahead of it. This force called root pressure, can push push xylem sap up a few meters. But xylem sap is mainly pulled, rather than pushed, from the roots of a plant to the leaves. The pulling force is called TRANSPIRATION, which is the loss of water from the leaves and other aerial parts of the plant. Water leaving the leaves is transpiration, each water molecule that evaporates pulls up the next water molecule because of Hydrogen bonds. To get water into the plant cell you need osmosis. Transpiration can pull xylem sap up the tree because of cohesion & adhesion. Cohesion is the sticking together of molecules of the same kind. In case of water, hydrogen bonds make the molecules stick to one another. In contrast to cohesion, adhesion is the sticking together of molecules of different kinds. Water molecules tend to adhere to cellulose molecules in the walls of xylem cells. What effect does transpiration have on a vertical string of water molecules that tend to adhere to the walls of zylem tubes. The water molecule is pulled off by a large gradient between the moist interior of the leaf and the surrounding air. Cohesion resists the pulling force of the diffusion gradient but it is not enough to overcome it. The molecule breaks off and the opposing forces of cohesion and transpiration put tension on the rest of the molecular string. Adhesion of the string of water molecules to the walls of zylem cells assist the upward movement of the xylem sap by counteracting the downward pull of gravity.

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4 – 15 – 99/Tuesday 5th lecture for test3

Chapter 20 Tissues/Cells

Every cell has to make its’ own ATP. There are 5 levels of animal structure hierarchy

• Cellular level – CELLS are the first level of organization. • Tissue level – The jellyfish is all tissue. Tissue cells are cells that share a similar

function. They are fused cells • Organ level – ex. The heart. The Heart is made up of several types of tissue,

including muscle tissue, connective tissue and other types. • Organism level – Consisting of many organ systems. The organ systems are not

isolated but work together. But we still study them independently.

TISSUES ARE GROUPS OF CELLS WITH A COMMON STRUCTURE & FUNCTION

A tissue is a cooperative unit of many similar cells that perform the same specific function. The cells are specialized; meaning the have a particular structure that enables them to perform their tasks. There are THREE main types: 1. Simple SQUAMOUS epithelium – Has a single layer of cells, lining the air

chambers of the heart 2. Simple CUBOIDAL – forms ducts, ex. Forming a tube in the kidney. 3. Simple COLUMNAR – lining the intestine. Offers protection. They form tight

junctions so nothing can cross over it.

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I. CONNECTIVE TISSUE BINDS & SUPPORTS OTHER TISSUES

In contrast to epithelium, connective tissue consists of a sparse population of cells scattered through a nonliving substance called the matrix. The cells synthesize the matrix, which is usually a web of fibers embedded in a liquid jelly or solid. There are six major types of connective tissue. 1. Loose connective tissue – serves mainly as a binding and packing material, holding

other tissues and organs in place. Ex. under your skin. 2. Adipose tissue – contains fat which pads and insulates the body and stores energy.

Each adipose cell contains 3. Blood – is a connective tissue with a fluid rather a solid matrix. The blood matrix

called plasma, consists of water, salts and dissolved proteins. Red & white blood cells are suspended in the plasma. Blood functions mainly in transporting substances from one part of the body to another and in immunity.

4. Fibrous connective tissue – forming a ligament. Has a matrix of densely packed parallel bundles of collagen fibers. It forms tendons which attach to muscle bone and ligaments which join bones together.

5. Cartilage – a connective tissue that forms a strong flexible skeletal material. Cartilage commonly surrounds the ends of bones, where it forms a smooth, flexible surface. It also supports the nose and the ears and it forms the cushioning discs between our vertebrae.

6. Bone – is a rigid connective tissue. It has a matrix of collagen fibers embedded in calcium salts. This makes them hard without being brittle. Blood vessels and nerves enter the bone through the canals and keep the bone cells alive. Because bone contains living cells, it can grow with the animal.

II. MUSCLE TISSUE FUNCTIONS IN MOVEMENT

Muscle tissue which consists of bundles of long cells called muscle fibers is the most abundant tissue in a typical animal. Animals & humans have three types. 1. Skeletal – is attached to bones by tendons. It is responsible for the voluntary

movements/muscle contractions of the body. A Skeletal muscle fiber is packed with strands that have alternating light & dark bands. Because of these bands, it is called striated muscle. Adults have a fixed number of skeletal muscle cells. Exercise does not increase the number of our muscle cells, it simply enlarges those already present.

2. Cardiac – forms the contractile tissue of the heart. It too is striated. 3. Smooth – has a lack of striations. This is Involuntary muscle. This type of muscle is

found is the digestive tract, urinary bladder, arteries and other internal organs. The cells are shaped like spindles. They contract more slowly than skeletal muscles, but they can sustain contractions for a longer period of time.

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III. NERVOUS TISSUE FORMS A COMMUNICATION NETWORK The functional unit of nervous tissue is the nerve cell, the neuron, which is uniquely specialized to conduct nerve signals.

4 – 20 – 99/Tuesday 6th lecture for test3

Chapter 28 Nervous System From 4 –13 –99 lecture. Glial cells help out the nervous system. A schwann cell is a type of glial cell which is highly specialized.

The Nervous system receives sensory input, interpret it and send out appropriate commands.

Describe DNA replication? The DNA helix opens up and replicates itself by the DNA polymerase. It begins at specific sites on the DNA strand and replicates in both directions. Parent strands open up to create bubbles of replication. Eventually all the bubbles merge to produce two daughter strands of DNA molecules. This process is divided into 3 phases: initiation, elongation and termination. Each strand starts with a 3 prime end that is attached to an OH group. At the other end of the 5 carbon sugar is the 5 prime end which is connected to a phosphate group. The DNA polymerase starts to link the DNA nucleotides to a growing daughter cell at the 3 prime end only and the resulting new strand starts to grow at the 5 prime end. This mirror image is called “anti-parallelism.” The DNA polymerase connects A to T with 2 hydrogen bonds and C to G with 3 hydrogen bonds and covalently bonds the nucleotide backbone together until two daughter strands are produced.

HOW ARE PROTEINS MADE? Proteins are made by ribosomes in the cytoplasm who get their instructions from the

mRNA strand. MRNA comes from the cell nucleus’ DNA. In the first process, transcription, an RNA polymerase moves along an opened strand

of DNA and copies only one side of it. C is matched with G and the A on the DNA is matched with U on the mRNA. After coming to a terminator site and the RNA

polymerase detaches and the resulting mRNA goes out into the cytoplasm after a few more revisions.

Now it goes to the ribosome to be translated. Translation is divided into three phases, initiation, elongation and termination. The mRNA molecule binds to a small ribosomal unit below the mRNA strand. Then a tRNA comes and binds to a start codon sequence

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on the mRNA strand. Then a large ribosomal unit binds to the small one; the tRNA fits into the P site on the large ribosome. Now it is a functioning ribosomal protein factory. Then an incoming tRNA fits next to the other tRNA on the A site. The A site reads the codon on the mRNA and makes an anticodon sequence to produce one amino acid. Then the growing polypeptide on the P site is moved onto the tRNA on the A site. Then the tRNA on the A site moves over to the P site, called Translocation, as the protein continues to elongate. The process continues until a stop codon is reached on the mRNA. The polypeptide is then freed from the tRNA and the ribosomes split up.

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Explain meiosis Meiosis in humans is the reproduction of gametes of the sex cells. The result will be four haploid cells with 23 chromosomes each. In prophase I, homologous chromosomes pair up to a form a tetrad. Then in a process called SYNAPSIS, the tetrads exchange information in a process called “crossing over.” Only the two innermost chromosomes will exchange genes. This is variability one. Then the spindle MT’s move to the poles and a spindle starts to form between them. The nuclear envelope disappears and the tetrads are moved to the center of the cell. This random alignment of the tetrads is called INDEPENDENT ASSORTMENT. Then in metaphase I, the spindle MT randomly grab at the kinetechore of the tetrads at their centromere region. This random picking of the tetrads is variability 2. In anaphase I, the chromosomes are pulled to the opposite poles but they do not separate into individual chromosomes; they remain as dyads at each pole. At the end of telophase 23 dyads are at each side of the cell and then in cytokinesis, the cell splits in two. There is no duplication after this stage going into meiosis II. In meiosis II, the chromosomes condense and the nuclear envelope again disappears during prophase II. In metaphase II, the third and final variability stage, the spindle MT’s grab onto the kinetechores and separate the chromosomes. Then each cell separates into 2 new daughter cells, similar to mitosis, but the resulting total is 4 daughter cells with 23 chromosomes each. This is done so an egg and sperm will fertilize into a zygote with the correct amount of 46 chromosomes to make a human. If the gametes did not go through the entire process of meiosis I and II, a sperm with 46 chromosomes would fertilize an egg with 46 chromosomes to make a zygote with 96 chromosomes.

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HOW DO WE REGULATE GENE REGULATION IN AN EUKARYOTIC CELL?

WHAT ARE DIFFERENCES BETWEEN GENE EXPRESSION IN BACTERIA AND EUKARYOTES?

Eukaryotic gene regulation is more complex than the bacterial lac operon model but both types of organisms regulate their expression of genes. Some differences are that eukaryotes are multi-cellular with a nucleus containing the DNA. So transcription and translation are not coupled in eukaryotes, unlike in bacteria. Eukaryotic genes are interrupted by non – coding DNA which is removed during splicing. Then the mRNA is modified in the nucleus so it can survive outside the nucleus and attach to the ribosomes. When a gene is to be expressed in an eukaryotic cell, ACTIVATOR PROTEINS, bind to the ENHANCERS on the DNA. The enhancers “fine tune” the amount of proteins to be made. There can be several enhancers used to make a protein. The enhancers come before the PROMOTER, unlike in the lac operon model. Then enhancers play a similar role to the operator in the lac operon model. Then after the activator proteins, such a GH, bind to the correct amount of enhancers other regulatory proteins bind to the activator proteins and the DNA strand is bent. These regulatory proteins now attach to the PROMOTER and an RNA polymerase comes to bind to the promoter. Then the gene is transcribed by the tRNA and an mRNA strand starts to grow. The RNA polymerase continues to make the mRNA strand until a terminator sequence comes and then the mRNA detaches from the RNA polymerase. In the lac operon model the DNA strand does not need to bend to start the transcription; only that the repressor leaves the operator so the RNA polymerase can read the gene for the lactose enzyme.

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Before going outside the nucleus, the mRNA is modified so it can survive outside the nucleus in the cytoplasm and to add to genetic variability. This modification process is absent from bacteria where there is no nucleus in the first place. On the mRNA strand are segments that not meant to be read called INTRONS and the segments to be read are called the EXONS. The introns are removed and the exons are spliced together to produce an mRNA molecule with a continuous coding sequence. This process is called RNA SPLICING. Then extra nucleotides are attached on both ends. A tail of Adenine nucleotides, about 100 – 300 long are added to the 31 end and a modified Guanine nucleotide is added to the 51 end. This is called the “5 prime cap” and functions in ribosome binding and mRNA stability. This final draft is then released out of the nucleus to be expressed by the ribosomes.

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4 – 22 – 99/Thursday 7th & last lecture for test3

Chapter 30 Muscles/Movement There are three kind of joints in the human skeleton. 1. Ball & Socket joints are in the hip & shoulder. 2. The Hinge Joint is in the knee. 3. The Pivot joint is at the elbow. Arthritis – inflammation of the joints affects one out every seven people in the U.S. The joints become stiff and sore and often swell, as the cartilage between the bones wears down. TEST THREE ESSAY: HOW DOES A SKELETAL MUSCLE CONTRACT?

The skeleton and muscles interact in movement.

Under its own power a muscle can only contract. Muscles are connected to bones by TENDONS made of fibrous connective tissue. The LIGAMENTS connect bone to bone.

Each muscle cell has its own contractile apparatus Skeletal muscle which is attached to the skeleton and produces body movements is made up of a hierarchy of smaller and smaller parallel strands. Each muscle fiber is itself a bundle of smaller MYOFIBRILS. A myofibril consists of repeating units called SARCOMERES. A sarcomere is the region between two dark narrow lines, called Z lines, in the myofibril. Functionally, the sarcomere is the contractile apparatus in a myofibril – the muscle fiber’s fundamental unit of action. The myofibril is composed of regular arrangements of two kinds filaments: thin filaments and thick filaments. The thin filament consists of a double strand of the protein actin and one strand of a regulatory protein, coiled around each other. Each thick filament consists of a number of parallel strands of the protein myosin. This specific arrangement of repeating units of thin and thick filaments is directly connected to the mechanics of muscle contraction.

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A MUSCLE CONTRACTS WHEN THIN FILAMENTS SLIDE ACROSS THICK FILAMENTS

The SLIDING – FILAMENT MODEL of muscle contraction explains the relationship between the structure of a sarcomere and its function. Contraction only shortens the sarcomere, it does not change the lengths of the thick and thin filaments. Parts of the myosin molecules called HEADS, bind with specific sites on the thin filaments. Energy for sliding comes from ATP. Also essential for muscle contraction are CALCIUM IONS ( Ca+), which trigger the initial events in sliding. • ATP binds to a myosin head, causing the head to detach from a binding site on actin. • Energy is made available for contraction when ATP is broken down (hydrolyzed) to

ADP and Phosphate, which remain bound to the myosin head. • The head gains some energy and its position changes as a result. In its new position

the myosin head is cocked like a pistol ready to fire. • The calcium comes in and “fires” the trigger – moving/contracting the muscle.

Thereby opening up another binding site on the actin molecule. The molecular event that actually causes sliding is called the POWER STROKE. The myosin head bends when ADP and P are released from it. The bending pulls the thin filaments toward the center of the sarcomere.

• Then the process repeats itself when ATP binds with myosin head. This cycle – detach, straighten out (cock), attach, bend – occurs again and again in a contracting muscle.

THE MECHANISM OF FILAMENT SLIDING figure 30.9b, page 599

MOTOR NEURONS STIMULATE MUSCLE CONTRACTION P. 600 The sarcomere of a muscle do not contract on their own. They must be stimulated to contract by Motor Neurons. A typical motor neuron can stimulate more than one muscle fiber because each neuron has many branches. A Motor Unit consists of a neuron and all the muscle fibers it controls. The motor neuron is the one that attaches to the muscle. Its axons form synapses, called NEUROMUSCULAR JUNCTIONS, with the muscle fibers. When a motor neuron

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sends out an action potential, its synaptic knobs release the neurotransmitter, ACTYCHOLINE. The more motor neurons stimulated, the more you could lift. It would take only a few motor neurons to lift a fork compared to lifting a ten-pound weight.

How does a motor neuron make a muscle contract? The initial events of stimulation are the same as those that occur at a synapse between the two neurons in the nervous system. The acetycholine that diffuses across the neuromuscular junction changes the permeability of the muscle fiber’s plasma membrane. The change triggers action potentials that sweep across the muscle cell membrane. The action potential goes into the muscle cell along membranous tubules that fold inward from the plasma membrane. Inside the cell, the action potentials make the ENDOPLASMIC RETICULUM release Calcium – CA+2 into the cytoplasm. The CA+2 (Calcium) then triggers the binding of MYOSIN to ACTIN, initiating filament sliding as previously described. When a muscle relaxes, the process reverses: motor neurons stop sending action potentials to the muscle fibers, the ER pumps calcium back out of the cytoplasm and the sarcomeres stop contracting.