Academic Science Biology Cells, Genes, and Cancer

SNC2D Grade 10 Academic Science Biology Cells, Genes, and Cancer Studying the Structure of Cells ● a cell is the smallest unit that can perform the functions of life ● microscopes allows individuals to see cells, and this allowed the advancement of medicine (ex.: germs cause diseases) ● microscopy is the science of using microscopes to view samples of objects ● the nucleus is an organelle that controls the cell’s activities ○ typically the only organelle visible from a light microscope ○ there are 3 main parts to the nucleus: ■ the nucleolus: makes ribosomes (which help to make proteins) ■ nuclear membrane: protects the contents of the nucleus ■ nuclear pores: allow materials, such as ribosomes in and out of the nucleus ● a micrograph is a photo taken with a microscope ● the cell theory ○ all living organisms are made of one or more cells ○ the cell is the basic organizational unit of life ○ all cells come from pre-existing cells ● the cytoplasm is the cytosol and organelles contained by the cell membrane (everything inside the cell membrane except the nucleus) ○ cytosol is the fluid material between the cell membrane and the nucleus ● cells can have different functions (specialized cells—brain cell vs. muscle cell) but they still contain the same organelles ● Many organelles are related to proteins in some way (storage, production, transport etc.) ○ proteins allow cells to carry out life processes that keep you healthy; essential to growth and repair of body tissue ● the organelles (specialized structure in a cell) found in cells are (either plant or animal; or both plant and animal) ○ cell membrane ■ separates the inside of the cell from the external environment (controls flow of materials into and out of the cell) ○ cytoplasm ■ includes the cytosol, the organelles and other life supporting materials (sugar, water etc.) ■ all contained by cell membrane (everything inside membrane; outside nucleus) ○ mitochondria (mitochondrion) ■ where energy is released from glucose to fuel cell activities ○ ribosomes ■ helps produce proteins (which make up much of a cell’s structure and are required for activities necessary for cell survival) ■ Some ribosomes float in the cytoplasm, others are attached to E.R. ○ endoplasmic reticulum ■ a network of membrane-covered channels that transport materials made in the cell; is connected to the nucleus ○ vesicles ■ membrane covered sacs that transport and/or store materials inside the cell ■ sometimes help these materials cross the cell membrane ○ Golgi body ■ sorts and packages proteins and other molecules for transport out of the cell ○ nucleus ■ controls all cell activities ○ vacuoles ■ contains water and other materials and are used to store/transport small molecules ■ plant cells tend to have one large vacuole; animal cells have several vacuoles ○ cytoskeleton ■ filaments and tubules that provide a framework for the cell (structure; “skeleton”) ■ provides tracks for vesicles and organelles to move on ○ cell wall (PLANT ONLY) ■ tough rigid structure lying just outside a plant cell’s membrane ■ provides structure for the cell ○ chloroplasts (PLANT ONLY) ■ trap energy from the sun to make glucose (glucose trapped is broken down in mitochondria to power cell activities) ○ lysosome (ANIMAL ONLY) ■ package of digestive enzymes that break down old/damaged organelles and waste ● cellular respiration occurs in all cells—changes glucose into energy ○ glucose + oxygen = carbon dioxide + water +energy Genes: Answers and Questions ● the nucleus contains a master set of instructions that determines what each cell will become, how it will function, and how long it will live before being replaced ○ these instructions are carried in chromosomes—a thread like structure made mostly of DNA ● every plant and animal species has a specific number of chromosomes in the nucleus of each cell ○ humans have 46 chromosomes (there are 23 types—1 from each parent) ● in the cells of most plants and animals, chromosomes come in pairs—one of each pair comes from each parent when an egg and sperm unite ○ in humans, 23 from the mother, 23 from the father ● chromosomes are made of a material called DNA (deoxyribonucleic acid) ○ each chromosome consists of a single molecule of DNA ● DNA is the material found in the cell nucleus that contains genetic information ● DNA is divided into segments, called genes ● ● ● ● ● ● ● ● ● ● ○ genes are segments of DNA that control protein production (the type of protein, and when they’re made), thus controlling the cell’s activities and structure each rung of a DNA molecule, along with the piece of the ladder’s side to which the rung is attached, is a building block molecule there are 4 types of building block molecules: A (adenine), C (cytosine), G (guanine), T (thymine) ○ the order in which the A, C, G, T building blocks are strung together, is called the genetic code (building blocks for DNA) ○ the genetic code is different for every individual (except identical twins) a gene is a relatively small part of a DNA molecule—each DNA molecule consists of hundreds of thousands of genes DNA controls many features, like hair and eye color, and your ability to digest certain foods (lactose intolerant) ○ DNA controls this through genes, which control the type of proteins your cells can make the job of genes is to control the manufacture of proteins each protein is designed to do a specific job—some proteins help build parts of your body’ others carry materials throughout your body DNA screening is the process of testing individuals to determine whether they have the gene or genes associated with certain genetic diseases Down syndrome can be screened from a fetus—fluid is drawn from the amniotic sac; the fluid is isolated for cells, and a micrograph of the chromosomes in these cells is taken ○ doctors examine the chromosomes—someone with Down syndrome will have an extra chromosome PKU is tested from a blood sample to detect the presence /absence of specific proteins in the blood ○ the presence/absence of a specific protein can indicate that the genes aren’t functioning correctly Huntington’s disease can be detected by identifying the existence of a specific gene—if a person has this gene, 100% certainty they’ll develop Huntington (50% chance of getting disease if 1 parent has it) ○ ethical issues related to testing for Huntington—gives those who have it unnecessary pain (con); reduces stress of uncertainty for those at risk (pro) ● the genetic code is universal—DNA building block molecules (A, T, C, G) produce the code for proteins in all types of organisms (bacteria, plants, animals) ● if a particular gene could be transferred between two different types of organisms, one species could then make proteins usually made only by the other species ● transgenic organisms are organisms whose genetic information has been altered with the insertion of genes from another species ● transgenic organisms are known very little for their long term consequences ○ how do GMO (plants) affect the consumers of it (humans) ○ is transplanting organs from transgenic animals (pigs) a good idea—spread viruses pigs are immune to, into humans ● cloning is the process of creating identical genetic copies of an organism ● for example, taking a part of a plant, rooting it, and therefore producing more plants that are exact copies of the parent plant ● a mutation is the change in the DNA of an organism ● because genes code for specific proteins based on the order of the DNA building blocks, a change in the order of A, T, C, G is known as mutation ● mutations alter the structure of the protein it produces ○ it alters how well the protein can do its job ○ example: A mutation in the gene that codes for the blood protein hemoglobin causes abnormal functions of the blood and red blood cells in people with sickle cell anemia. ● mutations are caused by mutagens—substances/factors that cause a DNA mutation (damages DNA) ○ example: sun’s UV rays, x-ray, chemicals (mercury) ● a mutation occurs, when the sequence of A, T, C, G building blocks change ● not all mutations are harmful ○ a mutation that occurs on the non-genetic part of the DNA molecule isn’t harmful ○ even mutations that change proteins, aren’t 100% of the time harmful ● gene mutations are partly to blame for some diseases ○ gene therapy corrects faulty genes—not much success though Cells from Cells ● cell reproduction is the process by which new cells are formed ● cell reproduction and the reproduction of a multicellular organism is different ○ in cells, one parent creates 2 daughter cells (that are identical in genes) ○ in multicellular organisms, 2 organisms create 1 baby (don’t contain identical genes to both parents) ● cell division is the process by which a parent cell divides into 2 daughter cells ● for single celled organisms, cell division is the main process by which individuals reproduce ● in multicellular organisms, cell division is the process by which a fertilized egg becomes an adult with millions of cells ● cell division also occurs when cells become too large to perform efficiently the functions of survival ● the cell membrane plays a significant role in a cell’s functions of survival ○ molecules of food and oxygen get delivered to every cell in your body, and enter the cell through its membrane (process known as diffusion) ● cell membrane is a barrier which everything must pass on its way into or out of the cell ● diffusion is the movement of molecules from areas of high concentration to low concentration ● the diffusion of water is known as osmosis ● the cell membrane is selectively permeable—allows certain substances to go through, and rejects certain substances from going through ● the surface of the cell must be big enough to allow for the entry of all of the oxygen and nutrients needed by the cell’s organelles, nucleus, and cytosol ● as cells use these nutrients, they become bigger (more volume) ● a cell needs enough surface area to service its volume ○ as a cell become larger, the surface area to volume ratio decreases ● a cell can’t be too big, or else it will not have enough surface area for the passage of all the nutrients it needs and the wastes it produces ○ therefore, when a cell reaches a certain size, it must divide to produce smaller cells (which have a higher SA:V ratio) ● you can’t divide a cell simply by cutting it down the middle to form daughter cells ○ what would happen if the nucleus wasn’t exactly in the center of the cell ○ there would be an uneven amount of chromosomes in the daughter cells ● there are 2 main parts to cell division: ○ mitosis: the process by which the duplicated contents of the cell’s nucleus divide into 2 equal parts ○ cytokinesis: the separation of the 2 nuclei and cell contents into 2 daughter cells ● all cells need to have the exact same genes (ALL 46 in a human) in order to function correctly, and produce the required proteins ○ therefore, the parent cell can’t just divide its chromosomes into 2 —this would mean each daughter cell would have half the required chromosomes needed to survive ● a parent cell makes a copy of every chromosome before it divides—it gives one copy to each of the 2 daughters ● the copying process is called DNA replication—the process by which DNA is copied, creating sister chromatids joined at the centromere ○ during replication, the two copies remain attached to each other by the centromere ● Chromosomes are typically long, loose threads until the cell is about to divide. ○ just before cell division, the chromosomes become thicker and bulgy ● at roughly the same time as DNA replication, the centrosome organelle doubles (cell has 2 copies) ○ centrosome help organize the tubules that make up cytoskeleton ● mitosis has 4 phases: ○ PROPHASE ■ replicated chromosomes coil in various ways until they are finally condensed (short) and thick ■ membrane around nucleus begins to break down; nucleolus disappears ■ the two centrosomes/centrioles (not centromere) head toward the opposite ends of the cell ■ extending from the centrosomes are spindle fibers (microtubules) towards the centromeres of the sister chromatids ○ METAPHASE ■ longest phase of mitosis ■ centrosomes reach the opposite ends of the cell and the chromosomes move towards the middle of the cell ■ eventually all chromosomes line up along the center of the cell ■ each centromere becomes attached to two spindle fibers—one from each centrosome ○ ANAPHASE ■ shortest phase ■ the proteins holding the two chromatids together at the centromere break apart ■ the spindle fibers pull one of the sister chromatids towards each of the poles (once chromatids separate, they become chromosomes) ■ the cell has twice as many chromosomes as usual at this point ○ TELOPHASE ■ the spindle fibers start to disappear ■ membranes form around the 2 new daughter nuclei —one at the end of each cell ■ within each nucleus, a nucleolus appears ■ chromosomes become less coiled and harder to see (longer and thinner) ● cytokinesis occurs after mitosis ● the division of the rest of the cell (the cytosol and organelles) usually begin before telophase is complete ● cytokinesis is different between plant and animal cells ○ ANIMAL CELL ■ a ring of specialized proteins around the middle of the cell starts to contract ■ the contraction pinches the cell membrane until the parent cell is divided into 2 parts ■ each daughter cell has a complete set of chromosomes in a nucleus and its own share of cytosol and organelles ○ PLANT CELL ■ the rigid cell wall makes it necessary for cytokinesis to be different in plants than animals ■ the Golgi body starts to produce small vesicles— each vesicle contains materials needed to form a cell wall (a structure that helps to form the cell wall in the process of plant cell cytokinesis) ■ the vesicles line up between the two new nuclei forming a cell plate—it grows outward and joins the old cell wall ■ new cell walls are secreted on each side of the cell plate, dividing cytoplasm in 2 ■ the new membrane forms inside the cell walls The Cell Cycle ● the lifespan of different cells varies ○ some cells live a rough life (exposed to constant abrasion and toxins) meaning they need to be replaced more ○ stomach(2 days) and skin cells (20 days) are replaced the most frequently ● some cells are encouraged to divide, while others are encouraged to “stay as they are” ○ molecules/proteins carry signals in cells, sharing info about when the cell should divide ● there are 2 main phases in a cell cycle ○ interphase ■ periods of growth in the life of a cell; consists of 2 growth stages (more organelles, cell grows larger or else it would be smaller and smaller), and a DNA replication stage (aka synthesis; forms sister chromatids) ○ cell division ■ mitosis and cytokinesis ● cell cycle checkpoint is a point in the cell cycle when proteins determine whether cell division should or should not occur ● there are 3 main points when a cell checks itself: ○ before DNA replication—does cell have enough nutrients to support growth ○ before mitosis—has the DNA replicated ○ before cytokinesis—has mitosis occurred correctly; are there normal amounts of chromosomes in the nuclei ■ very important—many cells leave the cycle at this point, as often, more cells of that type aren’t needed (body doesn’t need cell to divide—they enter a nondividing stage; most cells in human body are at this stage) ● when cells leave cycle, they become non dividing—carries out its functions until death ○ they can leave cycle in order to die also ● cell division won’t occur if: ○ there aren’t enough nutrients to support cell growth ○ DNA hasn’t replicated ○ DNA is damaged ● some cells leave cycle to die (damaged beyond repair for example); the contents of cell leaks out irritating surrounding cells ● some cells die through suicide—a cell breaks down in an organized way ○ its contents are packaged and distributed for use in other cells ○ suicide is pre-programmed into a cell through its proteins from suicide genes ○ cells kill themselves in certain situations—for example, when cell survival is a threat to organism (cell infected with a virus) ■ proteins of cell kill it (protein from suicide genes) ○ cell suicide is how fingers form ● cancer is when cells with abnormal genetic material divide uncontrollably and can spread to other body parts ● some cells are transformed so that they ignore the checkpoints in the cell cycle ○ instead of leaving cycle to die, they divide repeatedly and excessively, forming a clump of cells (tumor) ○ a tumor is an abnormal clump/group of cells ● the abnormal cells, with further mutation, can become cancer ○ Cancer is a condition where cells with abnormal genetic material divide uncontrollably, spread to other body parts, and then continue to do so. ● cancer can be spread through the body by blood, and continue dividing there ● normal cells can undergo 20-30 rounds of cell division—any more may result in mutated cells ○ after 20-30 rounds, the cell commits suicide ○ in cancer cells, enzymes cause cells to be unaware of the need to commit suicide or make it impossible to commit suicide ● most cells stop dividing when they realize they’re not attached to surface; cancer cell doesn’t do that ● carcinogens are mutagens which cause cancer ○ asbestos, tobacco smoke etc. ● abnormal cells take up space from normal cells (they take nutrients away from normal cells) ○ tumors reduce effectiveness of other cells’ cancer cells usually have several mutations before control of cell division is lost Handouts and Slideshows ● prokaryotes vs. eukaryotes ○ eukaryotes have a membrane bound nucleus; prokaryotes don’t ● proteins ○ ribosomes make proteins ○ proteins enter E.R. for modification ○ E.R. packages proteins into vesicles ○ vesicles transport/carry protein to other organelles or the Golgi apparatus ○ Golgi uses vesicles to export proteins out of the cell ● animal cells have Lysosome, many vacuoles, and centrioles—plant cells don’t ● plant cell has cell wall, chloroplasts, one vacuole—animal cells don’t ○ cell wall provides structural support and prevents cell rupture (located outside cell membrane) ● central vacuole for plants controls “turgor pressure” ● cells need to divide because: ○ to reproduce (single-celled organisms) ○ to grow (make new cells) ○ to repair (to replace old or damaged cells) ● DNA has instructions that determine what each cell will become, how it will function, and how long it will live before being replaced ● each cell in a human body has 23 different chromosomes—there are 2 versions of each chromosome (one from each parent) ● each chromosome is a single molecule of DNA ● DNA is in the shape of a double helix ● genes code for 1 (or more ) protein ● DNA has 2 main parts: ○ the sugar-phosphate backbone (handrails) ○ nitrogen bases (rungs/steps of ladder—A-T, C-G) ● functions of proteins ○ structure ○ enzymes (make chemical reactions in body happen faster) ○ antibodies (immune system) ○ hormones ○ transport (of molecules) ○ contractile (help muscles contract for movement) ● a typical cell spends ¾ of cell cycle preparing for division ● mitosis is the process by which all cells except sex cells divide ● purpose of mitosis is to divide up DNA that has been copied and create two identical cells ● cytokinesis is the division of the cytoplasm; mitosis is the division of the nucleus ● all cells go through mitosis; all cells need to grow larger and repair old cells ● many cells leave cell cycle after mitosis (don’t need more cells of that type) ○ when cells leave the cell cycle, they become non-dividing ○ most cells in human body are non-dividing (muscle and nerve cells for example) ● if cells don’t get change to grow, they become smaller (eventually too small to function correctly) ● cancer is when cells have abnormal genetic material that are dividing uncontrollably and can spread to other body parts ○ cancer cells ignore the “stop signs” in the cell cycle, and divide repeatedly and excessively ○ cancer cells can’t stop dividing, don’t stick to surfaces or to other cells, doesn’t self-destruct, don’t specialize ○ cancer is when DNA is damaged ■ DNA is damaged through mutations (especially if damage is in regions that produce checkpoints/suicide proteins ■ DNA mutations are caused by carcinogens (tobacco, radiation, toxins, viruses like HPV, inherited from parents etc.) ○ benign is a slow-growing/non-growing tumor that doesn’t spread; malignant is a fast-growing tumor that can spread easily through body (through blood) ○ cancer cells take nutrients from normal cells ○ prevention (avoid carcinogens), early diagnosis (annual checkups), and treatment (surgery, radiation, chemo) ○ as we age, risk of cancer increases (weaker immune system, health complications, more likely DNA damaged) ○ family history is a factor but not a definite for getting cancer