Intro to Cells

1. Intro to Cells Eukaryotes vs Prokaryotes Plasma Membrane

2. Two Basic Cell Types • All cells contain organelles • Small, specialized structures • Has a specific function in the cell • Prokaryotes • Do not contain any membrane-bound organelles • Most unicellular organisms • Example: bacteria • Eukaryotes • Contain membrane-bound organelles • Most multicellularoranisms • Example: humans • Note: amoebas, algae and yeast are unicellular but eukaryotes

3. Prokaryotes vs. Eukaryotes Eukaryotic cells are generally 1- 100 time bigger than prokaryotes

4. Cell Organelles

5. Animal Cell

6. Cell Organelles • Organelle= “little organ” • Found only inside eukaryotic cells • Everything in a cell except the nucleus is cytoplasm • Clear, gelatinous fluid inside the cell

7. Plasma Membrane • Boundary of the cell • Made of a phospholipidbilayer

8. Cytoskeleton • Acts as skeleton and muscle • Provides shape and structure • Helps move organelles around the cell • Made of three types of filaments

9. Nucleus • Control center of the cell • Contains chromatin, strands of genetic material (DNA) that condense to make chromosomes • Surrounded by a double membrane • Usually the easiest organelle to see under a microscope • Usually one per cell

10. Nucleolus • Inside the nucleus • Makes ribosomes

11. Ribosome • Site of protein synthesis • Found attached to rough ER or floating free in cytoplasm • Produced in a part of the nucleus called the nucleolus

12. Endoplasmic Reticulum • A.k.a. “ER” • Connected to nuclear membrane • Highway of the cell • Rough ER: studded with ribosomes; it makes proteins • Smooth ER: no ribosomes; it makes lipids

13. Golgi Apparatus • Looks like a stack of plates • Stores, modifies and packages proteins • Molecules transported to and from the Golgi by means of vesicles

14. Lysosomes • Garbage disposal of the cell • Contain digestive enzymes that break down wastes Which organelles do lysosomes work with?

15. Mitochondria • “Powerhouse of the cell” • Cellular respiration occurs here to release energy for the cell to use • Bound by a double membrane • Has its own strand of DNA Which type of cell do you think has the most mitochondria present?

16. Cell Wall • Found in plant and bacterial cells • Rigid, protective barrier • Located outside of the cell membrane • Made of cellulose (fiber)

17. Chloroplast • Found only in plant cells • Contains the green pigment chlorophyll • Site of food (glucose) production • Bound by a double membrane

18. Vacuoles • Large central vacuole usually in plant cells • Many smaller vacuoles in animal cells • Storage container for water, food, enzymes, wastes, pigments, etc.

19. Centriole • Aids in cell division • Usually found only in animal cells • Made of microtubules Where else have we talked about microtubules?

20. Quick Review • Which organelle is the control center of the cell? Nucleus • Which organelle holds the cell together? Cell membrane • Which organelles are not found in animal cells? Cell wall, central vacuole, chloroplasts • Which organelle helps plant cells make food? Chloroplasts • What does E.R. stand for? Endoplasmic reticulum

21. AMore in depth look at the plasma membrane

22. Plasma Membrane • Flexible boundary between the cell and its environment • Allows a steady supply of nutrients (ie: glucose, amino acids, lipids) to come into the cell no matter what the external conditions are

23. Plasma Membrane maintains homeostasis • Too much of any nutrient can be harmful to the cell • If levels become too high  the excess is removed through the plasma membrane • Maintains cells balance (homeostasis)

24. The Plasma Membrane is Selectively Permeable • Selective permeability: a process in which a membrane allows some molecules to pass through while keeping others out • Similar to a window screen (lets fresh air in but keeps most insects out) • Water is allowed to freely enter but other particles such as sodium and calcium ions must be allowed into the cell only at certain times

25. Structure of Plasma Membrane Phospolipid Molecule • Recall: Lipids are large molecules composed of • Glycerol + 3 fatty acids • If a phosphate group replaces a fatty acid then a phospholipid is formed. • Glycerol + 2 fatty acids + phosphate group Polar Head (includes phosphate group Nonpolar tail (fatty acids)

26. Plasma membrane is composed of a phospholipidbilayer • Has 2 layers of phospholipids back to back

27. Create a Drawing • Drawing must be similar to drawing on page 177 and must include: • A title • Labeled parts • Colored • On back of drawing: • Facts about the phospholipid bilayer • All bold faced words (include definitions) • Additional Facts should include information you think is important? (at least 8 facts in addition to bold faced words)

28. Important Facts • 2 fatty acid tails – nonpolar (hydrophobic) • Avoids water • Head containing phosphate group – polar (hydrophilic) • Allows the cell membrane to interact with its watery environment • Water molecules will not easily move through the barrieer because they are stopped by the water insoluble layer of fatty acid tails.

29. More important facts… • Fluid Mosaic Model • Model of plasma membrane – describes the plasma membrane as a phospholipid bilayer with embedded proteins • Phospholipids move within the membrane just like water molecules move with currents in a lake • Proteins also move (like boats with their decks above water and hulls below) • Proteins create a “mosaic” or pattern

30. More facts… • Other components of the membrane: • Cholesterol • Helps to stabilize the phospholipids by preventing fatty acid tails from sticking together • Transport proteins • Span the entire membrane • Help form the selectively permeable membrane that regulates which molecules enter and which molecules leave • Move needed substances and waste through the plasma membrane