BIO 100 Chapter 8 Notes
BIO 100 Chapter 8 Notes BIO 100
Popular in Introductory Biology
Popular in Department
This 5 page Class Notes was uploaded by Lauren Tebbe on Wednesday September 28, 2016. The Class Notes belongs to BIO 100 at Eastern Kentucky University taught by Kenneth Blank in Fall 2016. Since its upload, it has received 9 views.
Reviews for BIO 100 Chapter 8 Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 09/28/16
Chapter 8 BIO notes 1 The Basics of Cellular Respiration o Binary fission is a type of cell division in bacteria that produces two bacterial cells. These processes are forms of asexual reproduction because they produce new cells that are identical to the original. o Sexual reproduction which involves a sperm and an egg introduces variation to the offspring. o "All cells come from preexisting cells" just as this states, all organisms come from preexisting organisms. o Cellular reproduction involves two important processes: growth and cell division. o During growth, a cell duplicates its contents like organelles and its DNA. o Cell Division the DNA and other cellular contents of the parent cell are distributed to the daughter cells (beginning and resulting cells) 2 Chromosomes o An important event that occurs in preparation for cell division is DNA replication which is the process by which a cell copies its DNA o DNA and associated proteins are packaged into a set of chromosomes which allows it to be distributed to the daughter cells o Proteins and enzymes work to replicate in the nucleus of the cell. 3 Chromatin to Chromosomes o When eukaryotic cells are not undergoing cell division, the DNA and associated proteins have the appearance of thin threads called chromatin. o Chromatin is around a core of eight protein molecules o Protein molecules are histones and each bead is called a nucleosome o A human cell has 46 chromosomes o Prior to cell division, chromosomes are duplicated which is composed of sister chromatids held together by a centromere 4 The Cell Cycle: Interphase, Mitosis, and Cytokinesis o The cell cycle is an orderly sequence of stages that take place between the time a new cell has arisen from the division of the parent cell to the point when it has given rise to 2 daughter cells. o It consists of interphase (time when the cell performs its usual functions), mitosis (nuclear division), and cytokinesis (division of cytoplasm). 5 Interphase o Cell cycle spends most of its time in this phase. o DNA replication occurs in the middle of interphase and serves as a way to divide interphase into 3 phases: G1, S, and G2. o G1 is phase before replication and G2 is the phase following DNA synthesis, G stands for growth. o G1 includes doubling its organelles and accumulating materials that will be used for DNA replication o S stands for synthesis where each chromosome has one chromatid consisting of a single DNA double helix and by the end has sister chromatids where DNA replication occurs. o G2 phase extends from the completion of DNA replication to the onset of mitosis where cell synthesizes the proteins that will be needed for cell division like proteins found in microtubules which play an important role in cell division. o Nerve cells remain in G0 stage. 6 M (Mitotic) Phase o Where cell division occurs o The type of nuclear division associated with cell cycle is called mitosis which accounts for why this stage is called the M phase. o Duplicated nuclear contents are distributed equally, same number and kinds of chromosomes. o Each chromatid is a single DNA double helix containing the same sequence of base pairs as the original chromosome. o Sister chromatids separate and care daughter chromosomes. o Most eukaryotic cells have an even number of chromosomes because each parent has contributed half of the chromosomes to the new individual. 7 The Spindle o Most eukaryotic cells rely on a spindle (cytoskeletal structure) to pull the chromatids apart. o A spindle has spindle fibers made of microtubules. Assemble to take over the center of cell and separate chromatids and then disassemble. o A centrosome is the primary microtubule organizing center of a cell and animal cells have a 2 barrel like structure on this called centrioles. o Centrosome duplication occurs at the start of the S phase and completes by the G2 phase. During M phase they separate and move to opposite side forming the spindle 8 Phases of Mitosis in Animal and Plant Cells o Mitosis has four phases: prophase, metaphase, anaphase, and telophase. o Prophase: chromosomes condense consisting of 2 sister chromatids held with a centromere and the spindle begins to assemble between separating centrosomes. Disappearance of nucleolus and breakdown of nuclear envelope and chromosomes move towards the poles of the spindle fibers. o Metaphase: chromosomes are aligned in the middle and spindle fibers go to opposite poles. o Anaphase: sister chromatids separate and become daughter chromosomes, each pole receives a set of daughter chromosomes and chromosomes separate. o Telophase: the spindles disappear as new nuclear envelope form around daughter chromosome and division of cytoplasm begins. o Mitosis is usually followed by the division of the cytoplasm or cytokinesis which begins during telophase and continues after the nuclei have formed the daughter cells 9 Cytokinesis in Animal and Plant Cells o Cytokinesis follows mitosis. o When mitosis occurs but cytokinesis does not, a multinucleated cell occurs (fungi, slime mold, etc.) o Cleavage furrow in animal cells is an indentation of the membrane between the two daughter nuclei and begins as anaphase draws to a close and deepens with a band of actin filaments called the contractile ring and continues to contract the cytoplasm until there are two independent daughter cells. o Cytokinesis in plant cells occurs by a process where the rigid cell wall surrounds plant cells and does not permit cytokinesis by furrowing. It actually builds a new plasma membranes and cell wall between daughter cells. o A cell plate is simply newly formed plasma membrane that expands outward until it reaches the old plasma membrane and fuses with it. 10 The Cell Cycle Control System o The importance of cell cycle control can be appreciated by comparing the cell cycle to the events that occur in a washing machine. o The cell cycle's control system ensures that G1, S, G2, and M phases occur in order and only when the previous phase has been successfully completed. 11 Cell Cycle Checkpoints o Checkpoints delay the cell cycle until certain conditions are met: G1, G2, and the mitotic checkpoints. o Once the cell passes the G1 checkpoint it is committed to division and if it does not pass it will enter G0. The cell's DNA integrity is checked at this point as well, if damaged, protein p53 stops and initiates repair and if it is beyond repair it goes to cell death: apoptosis. o G2 verifies that the DNA has been replicated o Mitotic checkpoint is between metaphase and anaphase to make sure the chromosomes are properly attached to the spindle and will be distributed accurately to the daughter cells. 12 Internal and External Signals o Checkpoints are controlled by internal and external signals. o Internal signals are called cyclins which is levels of proteins must be accurate for the cell to proceed to G1 and S and G2 and M phase. o Enzymes called kinases remove phosphate from ATP often acts as an off/on switch for cellular activities, active in removal of the nuclear membrane and the condensation of chromosomes early in prophase. o External signals consist of growth factors and hormones. Growth stimulates tissue repair. o The cell cycle can be inhibited by cells coming into close contact with each other. o Cells keep dividing and then stop due to the phenomenon termed contact inhibition. o A telomere is a repeating DNA base sequence at the end of the chromosomes and have been likened to the protective caps on the ends of shoelaces because they ensure chromosomal stability. When these become too short, the cell begins to die. 13 Apoptosis o This is often defined as programmed cell death because the cell progresses through a typical series of events that bring about its destruction. o Cell division and apoptosis are opposing processes that keep the number of cells in the body at an appropriate level. o The number of somatic cells (body cells). 14 The Cell Cycle and Cancer o Cancer is a genetic disease caused by lack of control in the cell cycle. Development of cancer is from mutations that disrupt the many redundant regulatory pathways that prevent normal cells from taking on the characteristics of cancer. o Carcinogenesis is the development of cancer. o With a mutation, tumor cells release a growth factor which causes neighboring blood vessels to branch into the cancerous tissue (process of angiogenesis). Even more mutations cause the cancer cells to produce enzymes that degrade the basement membrane and invade underlying tissues. o Cancer cells are motile, able to travel through the blood or lymphatic vessels to other parts of the body where they start distant tumors in the process called metastasis. o Carcinogenesis is more likely to begin in cells that have the capacity to enter the cell cycle 15 Proto-Oncogenes and Tumor Suppressor Genes o Special proteins help regulate the cell cycle at checkpoints. o When cancer develops the cell cycle occurs repeatedly due in large part to mutations in two types of genes: 1. Proto-oncogenes which is code for proteins that promote the cell cycle and inhibit apoptosis. Think of a gas pedal of a care since they accelerate the cell cycle. 2. Tumor suppressor genes are code for proteins that restrains the cell cycle and promote apoptosis. Think of a car brake because it stops cell cycle and cells dividing inappropriately. Mutations may occur when mutations cause genes to become nonfunctional. 16 Proto-oncogenes become Oncogenes o Proto-oncogenes become cancer-causing genes called oncogenes when they mutate. o Proto promote the cell cycle and oncogenes accelerate the cell cycle. o A mutation that causes a proto-oncogene to become an oncogene is a "gain of function" mutation o A growth factor is a signal that activates a cell-signaling pathways by bringing about phosphorylation of signaling protein 17 Tumor Suppressor Genes Become Inactive o These mutations are called "loss of function" mutations because when they mutate they no longer inhibit cell cycle. o The retinoblastoma protein controls the activity of a transcription activator called E2F 18 Other Genetic Changes and Cancer o Telomeres control regulatory division o When telomeres become too short, the chromosomes cannot be replicated properly and the cell cycle is stopped o When chromosomes of cancer become unstable, portions of the DNA double helix may be lost, duplicated, or jumbled. These events are called translocations o A Philadelphia chromosome is the result of a translocation between chromosomes 9 and 22. o RB Gene is a tumor suppressor o RETGene is an abnormal allele of the RET gene o Genetic testing can be done in BRCA, RET, and RB genes 19 Characteristics of Cancer o Cancers are classified according to their location o Carcinomas are in the epithelial tissue in organs, sarcomas are cancers in muscle tissue, leukemia's are cancers in the blood. o Cancer cells have the following characteristics: 1. Cancer cells lack differentiation, they are immoral 2. Cancer cells have abnormal nuclei, they are enlarged and contain unusual number of chromosomes, gene amplification 3. Cancer cells do not undergo apoptosis, just continue to divide 4. Cancer cells form tumors, piling together on top of one another, lost all restraint 5. Cancer cells undergo metastasis and promote angiogenesis. A benign tumor is contained with a capsule and cannot invade other tissues but can become malignant (invasive) and escape that capsule in a process known as metastasis. 6. Angiogenesis allows for formation of new blood vessels to get nutrients and oxygen in the tumor to make it grow larger 20 Cancer Treatment o Removal of tumor o But since cancer divides rapidly, radiation and chemotherapy are more common treatments o Hormonal therapy also prevents cell division preventing the cells from receiving the signal they need for continued growth and division. 21 Prevention for cancer o To lower risk of cancer, avoid smoking, sunbathing, and excessive alcohol drinking. o Increase consumption of foods that are rich in vitamin A and C o Avoid salt or pickled foods o Vegetables and cabbage family foods!