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Micro and Plant reading logs
Terms in this set (19)
Differences in bacterial cell wall make-up
While most eukaryotes' cell wall is made up of cellulose, the bacterial cell wall is made up of peptidoglycan. This is a polymer composed of modified sugars cross-linked by short polypeptides. This cell wall enclosed the entire bacterium and anchors other molecules that extend from its surface. Archaeal cell walls contain a variety of polysaccharides and proteins, but they lack peptidoglycan.
Bacteria reproduce by binary fission. In this process, bacteria, which are single celled, divides into two identical daughter cells. Before binary fission occurs, the cell must copy its DNA and segregate these copies to opposite ends of the cell. Then the many types of proteins that comprise the cell division machinery assemble at the future division site. Protein monomers of FtsZ assemble into a ring-like structure at the center of a cell. Other components of the division apparatus then assemble at the FtsZ ring. It is then positioned so that division splits that cytoplasm and does not damage the DNA in the replication process. The cytoplasm is divided in two, and in many bacteria, a new cell is synthesized. The order and timing of these processes (DNA replication, DNA segregation, division site selection, invagination of the cell envelope and the synthesis of a new cell wall) are tightly controlled.
Ways bacteria get genetic recombination
Bacteria get genetic recombination by transformation, transduction, and conjugation. Transformation is when the DNA molecule of the donor cell is taken up by another recipient cell and its offspring inherit some characters of the donor cell. When different strains of bacteria are found in a mixed stage, either in culture or nature, some of the resulting offspring possess a combination of the characters of the parent strains. In transduction, the DNA molecule that carries the hereditary characters of the donor bacterium are being transferred to the recipient cell through a bacterial phage particle. Conjugation is when two bacteria lay side by side and a portion of their genetic material is slowly passed from one bacterium, a male, to a the female cell that is adjacent.
Communication in bacteria
Bacteria communicate by a process called Quorum sensing. This is a system of stimuli and response correlated to population density. Bacteria that use this process continuously produce and secrete certain signaling molecules called pheromones. The bacteria also have a receptor that can specifically detect the signaling molecule, the inducer. When the inducer binds to the receptor, it activates the transcription of certain genes. The greater the number of bacteria cells in a given environment, the greater chance there is for the signal to be activated.
Similarities and differences between protists
Protists are similar because the way in which they reproduce is asexually. Some protists can perform sexual and asexual reproduction, but most of them perform asexual. Also, they perform gas exchange in a similar way as well. They use simple diffusion to move gas into and out of their cells. Osmoregulation is also a similar function in protists. Most of the waste removal in protists are done by the contractile vacuole, but other methods are also used. Protists communicate in very different ways. Some release pheromones, excrete enzymes, release toxins, or use Quorum sensing.
Reproduction in fungi
Fungi can reproduce asexually and sexually. In asexual reproduction, the fungi produces their offspring by budding, or performing mitosis. In sexual reproduction, a positive and a negative haploid spores join. This joins the two cell's nuclei, mixing their DNA, creating a new offspring.
Communication in fungi
Fungi communicate through their septa. The septa is one of the cell-walls that divide a fungal hypha into cells. The septa generally have pores that are large enough to allow ribosomes, mitochondria, and even nuclei to flow from cell to cell. These pores also allow cellular signals to flow from cell to cell.
Water potential in plants
Water potential is the concept that helps describe the tendency of water to move into and out of areas. Water moves from areas of high concentration to areas of low concentration. Plants become strong and rigid when water moves into their cells.
Angiosperm reproduce using a process called double fertilization. This involves two sperm in the pollen tube and one egg. A single haploid sperm and a haploid egg fertilize into a diploid zygote. The other haploid sperm combines with the two polar nuclei of the large cell, forming a triploid.
Purpose and mechanism of double fertilization
This process involves the joining of a female gametophyte with two male gametes (sperm). Upon reaching the female gametophyte, one sperm fertilizes the egg to form a zygote. The other sperm combines with the two polar nuclei, forming a triploid nucleus in the center of the large cell of the female gametophyte. This large cell will then give rise to the endosperm, which is a food-storing tissue in the seed. Double fertilization ensures that endosperm develop only in ovules where the egg has been fertilized.
Mechanism of seed germination
Seed germination occurs when there is enough water in the seed environment to break the outer coating of the seed. Imbibition is the uptake of water due to the low water potential of the seed. The seed has little water in it and therefore the water moves into the seed, allowing the water to break the outer coating to allow the seed to start to grow.
Purpose and formation of the fruit
Fruit is the developed ovary of a flower. Fruit protects the seeds inside the fruit and also aids in the process of dispersal. Fruit ripening usually coincides with the time that the seeds complete their development. The fruit will look and taste better when the seeds are fully developed.
Signal transduction in plants and the greening process
Signal transduction in plants occurs in three steps- the first step is reception. This is when the plant is hit with a light source and the phytochromes in the plant absorb the wavelength of light. The second step is transduction. This is when second messengers relay the signal that was received by the phytochromes. The final step is the response. This can either be the plant beings to grow in the direction of the light, the plant beings to green, or stem growth slows down. The greening process is known as de-etiolation. This is when a plant shoot undergoes a change in response to light. The plant will continue to grow until it flowers.
Jobs/discovery of auxin
The job of auxin is to stimulate stem elongation, promote formation of roots, regulate development of fruit, function in phototropism and gravitropism, promote the formation of lateral and adventitious roots, promotes vascular differentiation, and retards leaf abscission. Auxin was discovered by three scientists over the course of many years. Charles Darwin contributed his discovery of auxin in 1881 by performing an experiment on coleoptiles. In 1913, Peter Boysen-Jensen demonstrated that the light signal that the plants were receiving was not transfixed, but mobile by separating the tip from the remainder of the coleoptile by a cube of gelatin that prevented cellular contact
Overview of the other plant hormones
Cytokinins regulate cell division in the shoot and the roots. They also stimulate seed germination and promote nutrient movement into sink tissues. Gibberellins stimulate stem elongation, pollen development, and allow the pollen tube to grow. They also promote fruit growth, seed development and germination. They also regulate the sex determination of the plant. They assist the plant in the transition from juvenile to the adult phase of development. Brassinosteroids promote cell division and cell expansion in the shoots. In low concentrations, they promote root growth, but when in high concentration, it inhibits root growth. They promote seed germination and pollen tube elongation. Strigolactones promote seed germination, they control apical dominance, and control the attraction of mycorrhizal fungi to the roots. Abscisic acid (ABA) inhibits growth. It also promotes stomatal closure when there is a drought, promotes seed dormancy and inhibits early seed germination. Ethylene promotes the ripening of some types of fruit, promotes the triple response in seedlings, enhances the rate of senescence, and promotes root and root hair formation.
How plants respond to light (39.3)
Plants respond to light by bending towards the light. Plants have two light receptors- blue-light receptors, which initiate phototropism, and phytochromes, which absorb red and far-red light. Depending on the amount and type of light the plant absorbs, this determines when the plant will flower. They are able to tell the time of day and which season they are in.
Short-day plants flower in the late summer, fall, and winter when the light period is shorter than the critical length. They require long periods of darkness to flower. Long-day plants flower in late spring or early summer when the light period is longer than the critical length. Long-day plants require long periods of light in order to flower.
How plants respond to gravity, touch, drought, flooding, salt, heat and cold
Plants respond to gravity by growing in the direction of gravity. Roots display positive gravitropism, while shoots display negative gravitropism. Plants will grow in the direction from which they were touched. For example, the trees that are on the coast will grow in the same direction that the wind is blowing so that its branches do not break off. During a drought, plants close their stomata to prevent water loss If a plant becomes flooded, the plant will die. The plant will not be able to perform cellular respiration because all the water present is preventing the plant from reaching the oxygen that is in the environment. Too much salt in an environment will cause the plant to have a lower water potential, making the plant wither. The heat will cause the plant's enzymes to denature and disrupt their metabolism. During the cold, the fluidity of the cell membrane decreases. If the membranes freezes, the plant will die. In response, plants produce antifreeze proteins to protect the cells from the cold and prevent the membrane from freezing.
How plants defend themselves
Plants defend themselves in a very close way in which humans defend ourselves against diseases. Their cells try to fight off the disease. Also, the plant can have external factors that protect the plant. For example, some plants have thorns on their stems that, when an animal tries to eat it, will feel pain and therefore have a "taste aversion" and not try to eat that plant again.
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