The Cell in Action. The Exchange with the Environment, Cell Energy, and the Cell Cycle

Transcription

1 The Cell in Action The Exchange with the Environment, Cell Energy, and the Cell Cycle

2 References Information and Most Images Holt Science & Technology, North Carolina, Grade 7. Holt, Rinehart and Winston: A Hartcourt Education Company, Chapter 14: Pages

3 Exchange with the Environment What is diffusion and osmosis? Passive and Active Transport? Endocytosis and Exocytosis?

4 Turn & Talk What would happen to a factory if its power were shut off or its supply of raw materials never arrived? What would happen if the factory couldn t get rid of it s garbage? Talk with your lab partner about these questions and write down your answers in your interactive notebooks.

5 How is the cell like the factory? An organism must be able to: Obtain energy Obtain raw materials Get rid of wastes These functions help keep cells healthy so they can divide. Cell division allows organisms to grow and repair injuries. At the cell membrane is where the exchange of materials takes place.

6 Diffusion Diffusion is the movement of particles from regions of higher density to regions of lower density. In this experiment, dye is poured on top of a layer of gelatin. At first, it is easy to see where the dye ends and the gelatin begins. But over time, the line between the two layers will blur. The tiny moving particles (which everything is made of) travel from where they are crowded to where they are less crowded. The dye particles are more crowded at the top and they move to where they are less crowded inside the gelatin. Diffusion also happens within and between living cells and they don t need energy for diffusion.

7 Diffusion of Water Cells of organisms are surrounded by and filled with fluids that are mostly water. Diffusion of water through cell membranes is so important to life processes. Osmosis the diffusion of water through a semipermeable membrane Semipermeable only certain substances can pass through Water is made up of particles, called molecules. Pure water has the highest concentration of water molecules (H 2 O). When you mix something, such as sugar, with water, you lower the concentration of water molecules. Over time, as you can see above, water molecules move from the liquid with the higher concentration of water molecules through the semipermeable membrane to the liquid with the lower concentration of water molecules (sugar water).

8 The Cell & Osmosis Osmosis is important to cell functions by keeping concentrations of cell particles in balance. Example: Red Blood Cells Red blood cells are surrounded by plasma, which is made up of water, salts, sugars and other particles. If red blood cells were in pure water, the water molecules would flood into the cells and cause them to burst (hypertonic). When red blood cells are put into a salty solution, the concentration of the water molecules inside the cell is higher than the concentration outside this would make water move out of the cells and the cells would shrivel up (hypertonic).

9 Transport Small Paricles Passive transport the movement of substances across a cell membrane without the use of energy by the cell. Active transport the movement of substances across the cell membrane that requires the cell to use energy

10 Transport Large Particles Endocytosis the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle (sacs formed from pieces of cell membrane) to bring the particle into the cell.

11 Transport Large Particles Exocytosis the process in which a cell releases a particle by enclosing the particle in a vesicle that then moves to the cell surface and fuses with the cell membrane

12 Cell Energy Why do cells need energy?

13 Turn & Talk Why do you get hungry? Talk with your lab partner about this question. Write your answers in your interactive notebook.

14 Cells Need Energy Feeling hungry is your body s way of telling you that your cells need energy All cells need energy to live, grow, and reproduce Plant cells get their energy from the sun (photosynthesis) Animal cells get their energy from food.

15 Plant Cells Photosynthesis Plant molecules have molecules (pigments) that absorb light energy. Chlorophyll is the main pigment used in photosynthesis and is found in chloroplasts. Plants use energy captured by the chlorophyll to change carbon dioxide and water into food (glucose) When plants make glucose, they convert the sun s energy into a form of energy that can be stored. Photosynthesis also produces oxygen.

16 Animal Cells Cellular Respiration Cellular respiration the process which cells use oxygen to produce energy from food Fermentation the breakdown of food without the use of oxygen Cellular respiration will release more energy from a given food than fermentation will.

17 Animal Cells Cellular Respiration During cellular respiration, food is broken down into CO 2 and H 2 O and energy is released. Most of the energy released maintains body temperature and some of the energy is used to form adenosine triphosphate (ATP) which supplies energy that fuels cell activities In prokaryotic cells (no nucleus), cellular respiration takes place in the cell membrane. In eukaryotic cells (have a nucleus), cellular respiration takes place in the mitochondria

18 The Connection: Photosynthesis and Cellular Respiration Photosynthesis Makes glucose and oxygen which is used by animal cells to make ATP. Cellular respiration releases carbon dioxide and water. Cellular Respiration Cellular respiration releases carbon dioxide and water which is used by plant cells to make glucose. During photosynthesis, oxygen is released.

19 Fermentation When your cells can t get oxygen needed for cellular respiration, they use fermentation to get energy. Example: Muscles Fermentation in your muscles produces lactic acid. The build up of lactic acid contributes to muscle fatigue and a burning sensation. Example: Yeast Yeast forms carbon dioxide during fermentation. The bubbles of the CO 2 gas cause the dough to rise and leave small holes in bread after it is baked.

20 Review & Practice You and your lab partner complete the Cell Energy review pages. Glue into your interactive notebook. Hand in your interactive notebook to Mrs. Quick.

21 Lab Fermentation with Yeast Making bread In your interactive notebook: What is your hypothesis on what is going to happen to the dough when we let it sit during the rest period (after the dough is mixed) What are we going to see after we bake the bread? Were your hypothesis correct? If they were, what process was used by the yeast in order to create these situations?

22 The Cell Cycle By the time you read this sentence, your body has made millions of new cells!

23 The Life of a Cell Cell Cycle the life cycle of a cell The cell cycle begins when the cell is formed and ends when the cell divides and forms new cells. Before a cell divides it makes a copy of the DNA (deoxyribonucleic acid) DNA is organized into structures called chromosomes (in a eukaryotic cell, one of the structures in the nucleus that are made up of DNA and protein; the main ring of DNA) Copying of the chromosomes ensures and exact copy of the parent cell to the new cell.

24 Prokaryotic Cell Reproduction Binary fission cell division of prokaryotic cells ( splitting into two parts )

25 Eukaryotic Cell Reproduction Eukaryotic cells are more complex than prokaryotic cells. The chromosomes of eukaryotic cells contain more DNA than those of prokaryotic cells. However, more complex eukaryotes do not necessarily have more chromosomes than simpler eukaryotes (for example: Fruit flies have 8 chromosomes; potatoes have 48 chromosomes; and humans have 46 chromosomes)

26 Eukaryotic Cell Cycle Stages Three Stages Interphase: the cell grows and copies its organelles and chromosomes (after the chromosome is duplicated the two copies are called chromatids; held together at the region called the centromere)

27 Eukaryotic Cell Cycle Stages Mitosis: the process of cell division that forms two new nuclei, each of which has the same number of chromosomes There are four phases of Mitosis Prophase Metaphase Anaphase Telophase

28 Eukaryotic Cell Cycle Stages Cytokinesis the division of the cytoplasm of the cell The cell membrane begins to pinch inward to form a groove, which eventually pinches all the way through the cell forming two daughter cells If a eukaryotic cell has a cell wall, a cell plate forms in the middle of the cell. The cell plate contains the materials for the new cell membranes and cell walls. After the split, a new cell wall forms where the cell plate was.

29 Eukaryotic Cell Reproduction Cells Alive!

30 Review & Practice You and your lab partner complete the Cell Cycle review pages. Glue into your interactive notebook. Hand in your interactive notebook to Mrs. Quick.

31 Lab Foldable Cell Cycle Sheets are folded for you Project directions: All rectangles should contain a title, illustration (picture), and detailed description of that stage of the cell cycle The Cell Cycle (Title) Stage 1: Interphase Stage 2a: Mitosis Prophase Stage 2b: Mitosis Metaphase Stage 2c: Mitosis Anaphase Stage 2d: Mitosis Telophase Stage 3: Cytokinesis Illustrations MUST be colored neatly and labeled with straight lines (use a ruler). Writing MUST be legible. NO PENCIL. Grading Rubric should be turned in with your project