Chapter 2 Sec. 3-4

1. Chapter 2 Sec. 3-4 The Cell in Action

2. Section 3:Objectives • Explain the process of diffusion • Describe how osmosis occurs • Compare passive and active transport • Explain how large particles get into and out of cells.

3. Exchange with the Environment • An organism is sort of like a factory. • It must be able to do 2 things: • Obtain energy and raw materials • Get rid of waste • These things help keep cells healthy so that they can divide. • The exchange of materials between a cell and its environment takes place at the cell membrane.

4. Exchange with the Environment • Diffusion: the movement of particles from regions of higher density to regions of lower density • Diffusion occurs within and between living cells. • Cells do not use energy for diffusion.

5. Exchange with the Environment

6. Exchange with the Environment • Example: • When someone makes coffee, diffusion is occurring. • The coffee pot represents the inside of the cell and the coffee filter represents the cell membrane. • Semi-permeable: only certain substances can pass through

7. Exchange with the Environment • Osmosis: the diffusion of water through a semipermeable membrane • Osmosis is important to cellular functions. • Osmosis occurs in plant cells: • When a wilted plant is watered, it enters the cell membrane and supplies the plant with water. The plant then looks healthy.

8. Exchange with the Environment • Small particles, such as water and sugar, cross the cell membrane through channels • Active transport: movement of particles across cell membrane with energy • High to low concentration • Passive transport: movement of particles across cell membrane without energy • Diffusion and osmosis are examples

9. Exchange with the Environment

10. Exchange with the Environment • Larger particles enter/exit the cell by one of the following 2 processes: • Endocytosis: process by which a cell membrane surrounds a particle without the use of energy • Exocytosis: process by which a cell releases a particle by enclosing the particle in a vesicle that then moves to the cell’s surface and fuses with the cell membrane

11. Exchange with the Enviroment

12. EXOCYTOSIS “Exo”= Exit “Osis”= Process Large particles are packaged in vesicles  vesicle travels to cell membrane  cell releases particle ENDOCYTOSIS “Endo” = To enter “Osis” = Process Cell comes into contact with particle  cell membrane wraps around particle  particle enters cell Exchange with the Environment

13. Cell Membrane

14. Phospholipids

15. Diffusion Examples

16. Osmosis Example

17. Section 3: Review Questions • 1) What is the difference between active and passive transport? • 2) What takes place at the cell membrane? • 3) Is energy required for diffusion? • 4) List 1 example of diffusion. • 5) When is osmosis important? • 6) How do small particles cross the cell membrane?

18. Section 4: Objectives • Describe photosynthesis and cellular respiration. • Compare cellular respiration with fermentation.

19. From Sun to Cell • Nearly all energy that fuels life comes from the sun. • Plants capture energy from the sun and change it into food through a process called photosynthesis. • What happens to the food plants make?

20. From Sun to Cell • Plant cells contain chlorophyll, a green pigment that absorbs light energy. • This gives plants their green color. • Where is the chlorophyll located in plant cells?

21. From Sun to Cell • Plants use the energy captured by chlorophyll to change carbon dioxide and water into food. • Glucose is the food that plants make. • Glucose is a simple sugar. (carbohydrate)

22. From Sun to Cell • Animal cells have different ways of getting energy from food: • Cellular respiration: uses oxygen to break down food • Fermentation: breakdown of food without the use of oxygen

23. From Sun to Cell • Respiration = “breathing” • Food is broken down into CO2 and H2O. • Most of the energy released maintains body temperature. • Some of the energy is used to form ATP. • Most of cellular respiration takes place in the cell membrane.

24. From Sun to Cell • Fermentation example: • One example of fermentation is when your muscles and tissues produce lactic acid. • The buildup of lactic acid contributes to muscle fatigue and causes a burning sensation.

25. Chapter 2 Sec. 4 Recap • 1) T/F Nearly all energy that fuels life comes from the sun. • 2) What is chlorophyll? • 3) What type of substance is glucose? • 4) List 2 ways animal cells get energy from food. • 5) In plant cells, list 2 things that food is broken down into. • 6) List one example of fermentation.

26. Section 3: Objectives • Explain how cells produce more cells. • Describe the process of mitosis. • Explain how cell division differs in plant and animal cells.

27. The Cell Cycle • As you grow, you pass through different stages. • Cells also pass through different stages (cell cycle: life cycle of a cell) • Growth begins when the cell if formed and ends when the cell divides.

28. The Cell Cycle • Before a cell divides, it copies its DNA. • DNA is the hereditary material that controls cell division. • The DNA of a cell is organized in structures called chromosomes. • Why is copying DNA important in cell division?

29. The Cell Cycle • Prokaryotic cells are less complex than eukaryotic cells. • Cell division in bacteria is called binary fission. • It results in 2 cells, each with one copy of the DNA.

30. The Cell Cycle • Eukaryotes are more complex than prokaryotic cells. • Eukaryotes contain more DNA than prokaryotic cells. • Different eukaryotes have different numbers of chromosomes. • What is the total # of chromosomes in humans? • How many pairs of chromosomes is that?

31. The Cell Cycle • The eukaryotic cell cycle has 3 major stages: • 1st phase: cell copies organelles and chromosomes • Once chromosomes are copied they are called chromatids • 2nd phase: chromatids separate(enters mitosis) • 3rd phase: cell splits into 2 cells

32. The Cell Cycle • Cell division begins at the cell membrane. • The division of cytoplasm is called cytokinesis. • Eukaryotic cells that have a cell wall form a cell plate which divides the cell in half.

33. The Cell Cycle • There are 6 steps to mitosis: • Interphase • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis

34. Diffusion/Osmosis Critical Thinking Exercise • Cell A contains 70% water and is normal. Cell B contains 85% water and is abnormal. Cell B continually takes in water and cannot release any. From what we have learned about diffusion, answer the following questions: • What part of the cell is not working properly? • If this continues what will happen to the cell? • Why is this not a characteristic of diffusion working properly?

35. Cell Cycle: Review Questions • The cell cycle begins when the cell is _______ and ends when the cell ______. • Before a cell divides, it copies its _____. • Cell division in bacteria is called ______. • Different eukaryotes have different numbers of ________. • List the 6 steps of mitosis. • ___________ cells are less complex than eukaryotic cells.

36. Chapter 2 Sec. 3-4 Vocabulary Review • 1) _____: a series of chemical reactions that convert the energy in food molecules into a useable form of energy called ATP • 2) _____: the movement of substances across the cell membrane without using the cell’s energy • 3) _____: the diffusion of water molecules only through a membrane • 4) _____: a process by which glucose is broken down into smaller molecules

37. Chapter 2 Sec. 3-4 Vocabulary Review • 5) ____: a series of chemical reactions that convert light energy, water, and carbon dioxide into glucose and give off oxygen • 6) ____: a reaction that eukaryotic and prokaryotic cells can use to obtain energy from food when oxygen levels are low • 7) ____: the movement of substances through the cell membrane only by using the cell’s energy

38. Chapter 2 Sec. 3-4 Vocabulary Review • 8) _____: when molecules pass through a cell membrane using special proteins called transport proteins • 9) _____: the movement of substances from an area of higher concentration to an area of lower concentration • 10) ____: the process in which the cell takes in a substance by surrounding it with the cell membrane • 11) ____: the process by which a cell’s vesicles release their contents outside the cell