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The Cell in Action

The Cell in Action. Chapter 4. Exchange with the environment. Section 1. Introduction. An organism must be able to obtain energy and raw materials and get rid of wastes These functions keep cells healthy so that they can divide Cell division allows organisms to grow and repair injuries

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The Cell in Action

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  1. The Cell in Action Chapter 4

  2. Exchange with the environment Section 1

  3. Introduction • An organism must be able to obtain energy and raw materials and get rid of wastes • These functions keep cells healthy so that they can divide • Cell division allows organisms to grow and repair injuries • The exchange of materials between a cell and its environment takes place at the cell’s membrane

  4. What is Diffusion? • Diffusion: the movement from areas of high concentration to areas of low concentration • Diffusion happens within and between living cells • Diffusion also happens between non-living things • Diffusion does not require energy

  5. What is Diffusion? • Diffusion of Water • Osmosis: the diffusion of water through cell membranes • So important to life processes so it gets a special name • Important to cell processes • Also occurs in plant cells • Semipermeable: only certain substances can pass through

  6. Moving Small Particles • Channels: where small particles (such as sugars) cross the cell membrane • Made up of proteins in the cell membrane • Particles move by either passive or active transport • Passive transport: the movement of particles across a cell membrane without the use of energy • Particles move from areas of high concentration to an area of low concentration • Examples: diffusion, osmosis

  7. Moving Small Particles • Particles move by either passive or active transport • Active transport: a process of transporting particles that requires the cell to use energy • Usually involves the movement of particles from an area of low concentration to an area of high concentration

  8. Moving Large Particles • Large particles move into and out of the cell by processes called endocytosis and exocytosis • Endocytosis: the active-transport process by which a cell surrounds a large particle (ex: large protein) and encloses the particle in a vesicle to bring the particle into the cell

  9. Moving Large Particles • Exocytosis • Exocytosis: active-transport process in which large particles (ex: wastes) leave the cell • A vesicle forms around a large particle within the cell • The vesicle carries the particle to the cell membrane • The vesicle fuses with the cell membrane and releases the particle to the outside of the cell

  10. Cell energy Section 2

  11. From Sun to Cell • Nearly all of the energy that fuels life comes from the sun • Photosynthesis: process in which plants capture energy from the sun and change it into food

  12. From Sun to Cell • Photosynthesis • Pigments: molecules in plant cells that absorb light energy • Chlorophyll is the main pigment used • Plants use the energy captured by chlorophyll to change carbon dioxide and water into food • Food is in the form of the simple sugar glucose • Glucose is a carbohydrate • Photosynthesis also produces oxygen

  13. Getting Energy from Food • Animal cells have different ways of getting energy • Cellular respiration: uses oxygen to break down food • Fermentation: the breakdown of food without the use of oxygen

  14. Getting Energy from Food • Cellular respiration • During cellular respiration, food (such as glucose) is broken down into CO2 and H2O, and energy is released • Most of the process of cellular respiration takes place in the cell membrane of prokaryotic cells • In eukaryotic cells, cellular respiration takes place mostly in the mitochondria

  15. Getting Energy from Food • Connection between photosynthesis and respiration • Photosynthesis: cells use CO2 to make glucose, and the cells release O2 • Cellular respiration: cells use O2 to break down glucose and release energy and CO2 • Each process makes the materials that are needed for the other process to occur elsewhere

  16. Getting Energy from Food • Fermentation • When muscle cells can’t get the oxygen needed for cellular respiration, they use fermentation to get energy • Causes burning sensation • Another type of fermentation occurs in some bacteria and in yeast

  17. The Cell Cycle Section 3

  18. The Life of a Cell • Cell cycle: the life cycle of a cell • Begins when the cell is formed and ends when the cell divides and forms new cells • Before a cell divides, it must make a copy of its DNA • DNA is organized into chromosomes • Copying chromosomes ensure that each new cell will be an exact copy of its parent cell

  19. The Life of a Cell • Making More Prokaryotic Cells • Prokaryotic cells have ribosomes and a singular, circular DNA molecule but don’t have membrane-enclosed organelles • Binary fission: cell division in bacteria; means “splitting into two parts”

  20. The Life of a Cell • Eukaryotic Cells and Their DNA • The chromosomes of eukaryotic cells contain more DNA than those of prokaryotic cells do • Homologous chromosomes: chromosomes that have the same sequence of genes and the same structure

  21. The Life of a Cell • Making More Eukaryotic Cells • The eukaryotic cell cycle includes three stages: • Interphase • Cell grows and copies its organelles and chromosomes • Mitosis • Chromatids separate • Complicated chromosome separation process • Ensures that each new cell receives a copy of each chromosome • Four phases: prophase, metaphase, anaphase, telophase • Cytokinesis • Cell splits in two; these cells are identical to each other and the parent cell

  22. Interphase Metaphase Anaphase Prophase Telophase Cytokinesis • Interphase • Before mitosis begins, chromosomes are copied. Each chromosome is then two chromosomes. • Mitosis • Prophase: mitosis begins; the nuclear membrane dissolves.; chromosomes condense into rod-like structures. • Metaphase: the chromosomes line up at the equator

  23. Interphase Metaphase Anaphase Prophase Telophase Cytokinesis • Mitosis • Anaphase: chromatids separate and move to opposite sides of the cell • Telophase: nuclear membrane forms around each set of chromosomes; chromosomes unwind; mitosis stops • Cytokinesis • Cell pinches in two

  24. Mitosis and the Cell Cycle • Cytokinesis • In animal cells, division of the cytoplasm begins at the cell membrane • Cell membrane begins to pinch inward to form a groove, which eventually pinches all the way through the cell • Two daughter cells form • Division of cytoplams • In cells with cell walls, a cell plate forms in the middle of the cell • Cell plate contains the materials for the new membranes and cell walls

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