Cells Alive - PC\|MAC

Cells Alive - PC\|MAC

Cell Growth and Division Chapter 10 In Your Notebook Materials move through cells by diffusion. Oxygen and food move into cells, while waste products move out of cells. How does the size of a cell affect how efficiently materials get to all parts of a cell? Work with a partner to complete this activity. 1. On a sheet of paper, make a drawing of a cell that has the

following dimensions: 5 cm x 5 cm x 5 cm. Your partner should draw another cell about one half the size of your cell on a separate sheet of paper. 2. Compare your drawings. How much longer do you think it would take to get from the cell membrane to the center of the big cell than from the cell membrane to the center of the smaller cell? 3. What is the advantage of cells being small? Think About It

When a living thing grows, what happens to its cells? Does an organism get larger because each cell increases in size or because it produces more cells? What is there about growth that requires cells to divide and produce more of themselves? Limits to Cell Size

All cells can increase in size Eventually they have to divide Two Reasons for division Larger cells place more demands on DNA Larger cells less efficient moving materials across cell membrane Reason #1 Information Overload Even though the cell gets larger its

DNA does not Example: small town small library limited number of books people have to wait to borrow books If town grows so does demand for books have to build bigger library DNA is our genetic library Reason #2 Exchanging Materials

Need to get food in and waste out as quickly as possible Want large surface area to volume ratio Traffic Problems If town only had two-lane main street leading to center of town as town grows traffic gets congested becomes difficult to move goods in and out

Same for cell cant get Oxygen and nutrients in and waste products out So cells dont keep growing larger even if organism does Cell Division Process by which a cell divides into two new daughter cells

DNA replicates Cuts down on DNA overload Reduces cell volume So materials can move in and out quickly In Your Notebook Write two short summary statements that explain why information overload and exchanging materials limit cell

size. Types of Reproduction - #1 Asexual Production of genetically identical offspring from a single parent Simple, efficient, effective Population can grow quickly Used by single-celled organisms Bacteria

Used by multi-celled organisms budding Asexual The Good & The Bad Advantages For bacteria, when conditions are right, faster reproduction means better chance of survival As long as conditions stay right being genetically identical is also

good Disadvantage When conditions change everyone dies Types of Reproduction - #2 Sexual Fusion of two cells Need mommy and daddy Offspring inherit some of their

genetic information from each parent Used by most animals and plants Also many single celled organisms Sexual The Good & The Bad Advantages When seasons affect food supply it can be better to take time to find mate and

grow and develop offspring Provides genetic diversity If environment changes some offspring may have right combination of characteristics to survive Disadvantage Takes a long time Cant do it alone In Your Notebook

Use a Venn Diagram to compare asexual and sexual reproduction Look on page 277 if you need ideas 10.2 Cell Division The cell cycle represents the events that take place as a cell grows, prepares for division, and then divides into two new cells. Once two new cells have formed,

they each begin the cycle anew. Like other cycles, the cell cycle is broken into phases. Different types of cells and cells from different organisms may show slight variations in some of the phases of the cycle, but the general course of events is similar for all living things. In Your Notebook 1. Why do you think it is advantageous for cells to

go through the different events of the cell cycle (such as copying their genes or building the materials needed for division) in an ordered way? What might happen if a cell underwent all of these activities at once? 2. Why do you think that it is important for a cell to grow in size during its cell cycle? 3. What might happen to a cell if all of the events leading up to cell division took place as they should, but the cell did not divide?

Think About It What role does cell division play in your life? What happens when you are finished growing? Does cell division stop? What if you break a bone or get a cut? What about general wear and tear Like on your skin, digestive system or

even your blood? Chromosomes Bundled packages of DNA Read What is the role of chromosomes in cell division on page 279 Prokaryotic Chromosomes Prokaryotes have no nucleus

DNA Found in cytoplasm Single, circular chromosome Eukaryotic Chromosomes More DNA than prokaryotes Multiple chromosomes in cell Fruit flies 8 Humans 46 Carrots - 18

Found in nucleus Contain DNA and proteins (histones) Eukaryotic Chromosomes Which side, left or right, shows the smallest structures, and which shows the largest? The Cell Cycle A series of events during which the

cell grows, prepares for division then divides into two daughter cells. Prokaryotic Cell Cycle Binary Fission Result: Two genetically identical daughter cells In Your Notebook

Why does the cell duplicate its DNA? What might happen if the membrane did not indent and pinch off? The Eukaryotic Cell Cycle Four phases G1, S, G2 and M Timing of cycle depends on the

type of cell Phases of Cell Cycle G1 Most growing happens here Cell increases in size Makes new proteins and organelles G = Gap

Phases of Cell Cycle S phase S = Synthesis DNA replicated Phases of Cell Cycle G2 Preparing for division Organelles and molecules for division

produced G1, S and G2 are together known as Interphase Phases of Cell Cycle M Phase Cell division Includes mitosis and cytokinesis

Mitosis Division of nucleus Cytokinesis Division of cytoplasm Whats a Chromosome? Chromatin uncoiled DNA Chromatid coiled DNA Centromere where duplicate strands attach

Mitosis Four steps to divide nucleus prophase, metaphase, anaphase & telophase Prophase Genetic material in nucleus condenses Chromosomes become visible Spindle starts to form

Centrioles move toward poles Nucleolus disappears Nuclear envelope starts to break down Mitosis Four steps to divide nucleus prophase, metaphase, anaphase & telophase Metaphase

Chromosomes line up in middle of cell Spindle fibers connect to centromeres Mitosis Four steps to divide nucleus prophase, metaphase, anaphase & telophase Anaphase

Sister chromatids separate and move apart Move along spindle fibers to opposite ends of cell Mitosis Four steps to divide nucleus prophase, metaphase, anaphase & telophase Telophase

Chromosomes spread out into tangle of chromatin Nuclear envelope reforms Spindle breaks apart Nucleolus reforms In Your Notebook Create a chart that lists two important

pieces of information about each phase of mitosis. Cytokinesis Now that the nucleus is split we have to divide the cytoplasm Animals Membrane drawn in and pinches apart Plants

Cell plate forms between new nuclei Cells Alive http://cellsalive.com/mitosis.htm In Your Notebook You are going to write a memoir as if you were a cell that just divided. Answer the following as you go:

Why did you decide to divide? Were there signals that told you it was time? Describe how you divided. What happened? In what order? Talk about why each process you went through was important to you and your daughter cells. 10.3 & 10.4 Regulating The Cell Cycle and

Cell Differentiation In Your Notebook Name two things that might go wrong if the cell cycle is not carefully regulated. Controls on Cell Division Cells grown in dish in lab will stop dividing when they touch other cells Scrape away neighboring

cells and the cells left start dividing again When you are injured the cells at the edge start dividing until healing process is done. Cyclins and Regulatory Proteins Cyclins Family of proteins that tell cell when it is time to divide, duplicate chromosomes of enter

next phase of cell cycle Internal Regulators Respond to events inside cell Wont let cell enter mitosis without duplicating chromosomes first External Regulators Looks at things outside the cell Growth factors stimulate growth and division

Apoptosis Programmed cell death Helps shape structure of tissues and organs We dont have webbed feet because cells in between toes are programmed to die If they dont you have disease known as syndactily

Cancer These cells dont respond to signals that control growth Divide uncontrollably Caused by: Gene defect Smoking Chewing tobacco Radiation exposure

Viral infection Cancer Treatments Surgery Physical removal of tumor Radiation Targeted beam that kills rapidly dividing cells Chemotherapy

Targets rapidly dividing cells throughout body Hair, skin and digestive system cells normally divide rapidly so the healthy cells as well as the cancer cells are damaged This makes your hair fall out Gives you mouth sores Intense nausea In Your Notebook What makes cancer cells different from healthy

cells? When researchers develop drugs to fight cancer, what characteristics of cancer cells do you think they target? The human body contains 100,000,000,000,000 cells. Starting with one cell how many divisions would you need to get to this number? One Cell To Many

We are start out as a single cell, become embryo, then adult Differentiation Process by which cells become specialized Pg 293 Stem Cell Development Embryo Totipotent

Can become anything Blastocyst Four days of development Hollow ball with cluster of cells inside Pluripotent Can become almost anything Stem Cell Development

Embryonic Stem Cells The cluster of cells inside the blastocyst Pluripotent Can become practically anything in the body Adult Stem Cells Multipotent More limited potential but can develop into many different types of cells Bone marrow stem cells can become several different types of blood cells

Stem cells in brain can produce neurons or nerve cells Stem Cell Research Benefits These cells could be used to repair or replace damaged cells and tissues Heart attack Paralysis Ethical Issues

Right now using embryonic stem cells kills embryo Is the embryo entitled to the rights and protections of any human being? On the horizon Working to extract cells without harming embryo Finding ways get adult stem cells to act like embryonic ones In Your Notebook Why is differentiation important to

multicellular organisms? What are the three different types of stem cells and their respective potential to differentiate? How might technological advances help address the ethical concerns surrounding stem cell research?

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