Bellwork: Thurs. Oct. 22, 2015: (1st BELLWORK for new unit!!) Main reasons why cells divide: more demands are put on its DNA when it becomes larger. The cell has more trouble moving enough nutrients and wastes across the cell membrane. when it becomes larger.

Mitosis Meiosis Notes 5

Notes: 10 – 1 Cell Growth

Think of few problems that this would cause. Imagine: What if all classes at IRHS were held in the gym…at the same time? How well do you think that would work? What would some problems be? Think of few problems that this would cause.

What if instead of having more than one vending machine on campus, there was only one vending machine for all of IRHS? OMG… no more junk food!

Why would this be a problem? What if IRHS had a room filled with vending machines but only a single door in and out? Why would this be a problem?

Students Trampled in Vending Machine Frenzy for Last Poptart

DNA Overload The information controlling cell function is stored in the DNA molecule When a cell is small, the information stored in that DNA is able to meet all of the cell's needs. But as a cell increases in size, it usually does not make extra copies of DNA. If a cell were to grow without limit, an “information crisis” would occur. https://www.youtube.com/watch?v=wuXSEOKNxN8

Ratio of Surface Area to Volume Surface area = length × width × number of sides Volume = length × width × height Ratio = surface area / volume If the length of the cell doubled, what would happen to the cell's surface area compared to its volume? The cell's surface area would be equal to 2 cm × 2 cm × 6 = 24 cm2. The volume would be equal to 2 cm × 2 cm × 2 cm = 8 cm3. The cell's ratio of surface area to volume would be 24 / 8, or 3 : 1. What if the length of the cell triples? The cell's surface area now would be 3 cm × 3 cm × 6 = 54 cm2. The volume would be 3 cm × 3 cm × 3 cm = 27 cm3. The ratio of surface area to volume would be 54 / 27, or 2 : 1. Note that the volume increases much more rapidly than the surface area, causing the ratio of surface area to volume to decrease. This decrease creates serious problems for the cell. Click on the activity at right to see how changes in the size of a cell affect surface area, volume, and ratio of surface area to volume. A bigger ratio of surface area to volume is better for exchange!

Food, oxygen, and water enter a cell through its cell . Exchange of Materials Food, oxygen, and water enter a cell through its cell . membrane Waste products in the same way. leave/exit rate of exchange depends on cell surface area - which is the total area of its cell membrane. BUT… rate at which food and oxygen are used up and waste products are produced depends on the cell's volume.

How does a whale stay warm in freezing water? A low surface area to volume ratio! As an animal increases in size, its volume increases more rapidly than its surface area. This means that there is less surface area, skin, exposed to the freezing water in comparison to the volume.

Where do you think this rabbit (Sylvilagus audubonii) lives and how can you tell? The desert! Note the surface area to volume ratio of the ears.

When a living thing grows, what happens to its cells? In most cases, living things grow by producing more cells. On average, the cells of an adult animal are no larger than those of a young animal—there are just more of them. Does an animal get larger because each cell increases in size or because it produces more of them?

In most cases, living things grow by producing more cells. On average, the cells of an adult animal are no larger than those of a young animal—there are just more of them.

So how do we go from this…

…to this? Cell Growth and Division!

Process by which cells divide into two new daughter cells is called________________ Mitosis https://www.youtube.com/watch?v=Cg4ASxSKH2o

They increase at the same rate. Q1. As a cell increases in size, which increases more rapidly, its surface area or its volume? Surface Area Volume They increase at the same rate. Tips: The New Slide button is on the Standard toolbar. You can also click Insert>New Slide.

Low surface area to volume ratio, i.e. 2:1 Q1. Which do you want for better exchange of materials across the cell membrane? Low surface area to volume ratio, i.e. 2:1 Equal surface area to volume ratio, i.e. 1:1 High surface area to volume ratio, i.e. 6:1 Tips: The New Slide button is on the Standard toolbar. You can also click Insert>New Slide.

Q3. Which of the following is a reason why cells divide? All of the DNA can’t fit within a single cell. DNA becomes diluted as a cell increases in size. The larger a cell becomes, the more demands the cell places on its DNA. DNA doesn’t increase in size fast enough to keep up with a cell’s growth. Tips: The New Slide button is on the Standard toolbar. You can also click Insert>New Slide.

Q4. Which of the following is another reason why cells divide? As a cell gets larger, it becomes more susceptible to attack. The cell has more trouble moving enough nutrients and wastes across the cell membrane. There isn’t enough room in the organism to accommodate larger cells. As a cell gets larger, its membrane gets weaker until it bursts. Tips: The New Slide button is on the Standard toolbar. You can also click Insert>New Slide.

What are the two main reasons why cells divide? 1. The larger a cell becomes, the more demands the cell places on its DNA. 2. In addition, the cell has more trouble moving enough nutrients and wastes across the cell membrane. Tips: The New Slide button is on the Standard toolbar. You can also click Insert>New Slide.

Process by which cells divides into two new daughter is called Mitosis

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