THE CELL

1. THE CELL

2. Cell Structure and Communication

3. Cell Size • 1. Higher plant cells, 10-100 µm long • 2. Bacterial cells, 0.5-1.0 µmlong • 3. Pear tree leaf contains ~ 50 million cells • 4. Full grown pear tree contains ~ 15 trillion cells

4. The Cell Wall • 1. Found outside plasma membrane • 2. Consists of mostly cellulose • cellulose molecules grouped into bundles known as microfibrils • 3. Pectins form the middle lamella • 4. First formed walls called primary walls, then secondary walls may be formed • 5. Lignin may be part of cell wall giving mechanical strength to wall • 6. Plasmodesmata interconnect living plant cells

5. Communication Between Cells • 1. Plasmodesmata • fine strands of cytoplasm interconnect plant cells

6. Cellular Components

7. The Plasma Membrane • 1. Outer boundary of living cell, extremely thin • 2. Mosaic structure composed of phospholipids and proteins • 3. Unit membrane structure seen with electron microscope

8. Plasma Membrane

9. The Nucleus • 1. Most conspicuous organelle, generally spherical or ellipsoidal in shape • 2. Control center of the cell, stores hereditary information • 3. DNA in nucleus makes a copy of itself (RNA) as a blueprint for directing proteinsythesis • 4. Contains 2 membranes (outer and inner), called the nuclear envelope, which contains pores to allow passage of certain molecules • 5. Outer membrane connected to endoplasmic reticulum • 6. Nucleoplasm is the granular-appearing fluid inside the nuclear envelope • 7. Nucleoli are larger bodies noticeable in the nucleoplasm • • involved in RNA synthesis • 8. Chromatin is the thread-like DNA strands which shorten and condense intochromosomes when the cell is ready to divide • • chromatin composed of DNA and protein

10. Nucleus

11. The Endoplasmic Reticulum • 1. Complex system of membrane channels • 2. Outer surface of membranes may be covered with ribosomes • 3. Called “rough” ER because of pebbly appearance • 4. “Smooth” ER has no ribosomes • 5. Protein synthesis, secretion and storage associated with rough ER

12. Endoplasmic Reticulum

13. Ribosomes • 1. Occur free in cytoplasm, mitochondria and chloroplast, or associated with rough ER • 2.Roughly ellipsoidal in shape, approximately 17-25 nm in diameter • 3.Function in protein synthesis by linking amino acids together • 4. Ribosome composed of two subunits, made up of RNA and proteins

14. Ribosomes

15. Dictyosomes • 1. Groups of flat, roundish sacs, organized into stacks • 2. Collecting and packaging centers for proteins and other molecules like carbohydrates • 3. Golgi complex is continuous with endoplasmic reticulum canals on one side and to secretary vesicles leading the cell membrane on the other.

16. Dictyosomes

17. Plastids Three Types • 1. Chloroplasts • 2. Chromoplasts • 3. Leucoplasts

18. Plastids • 1. Three Types • a. Chloroplasts • 1) Most common type, green in color • 2) Stroma, enzyme containing region • 3) Grana membranes called thylakoids, suspended in the stroma

20. Plastids type cont • b. Chromoplasts • 1) Contain colored pigments such as carotenoids • 2) Give orange, red, and yellow colors to various plant parts • c. Leucoplasts • 1) Colorless • 2) Types • i) Amyloplasts, store starch granules • ii) Elaioplasts, store oils

21. Chromoplasts from red pepper

22. Leucoplasts

23. Plastids type cont • 2. Proplastids • • all plastids develop from these

24. Mitochondria • 1. “Power-houses” of the cell • 2. Function in generation of ATP, the energy molecule of the cell • 3. Small organelles, 1-3 µm in length, look like tiny membranes • 4. Outer and inner membranes present • • inner membrane has inward extensions or folds called cristae

25. Mitochondria

26. Microbodies • 1. Small spherical organelles, bounded by a single membrane • 2. Contain enzymes which function in photosynthesis, photorespiration, and conversion of fats to carbohydrates • 3. Lysosomes • a. Store digestive enzymes (more typical of animal cells) • b. Digestive activities similar to vacuoles of plant cells • 4. Microbodies seen only with an electron microscope

27. Lysosomes

28. Microbodies

29. Vacuoles • 1. Membrane bound sacs filled with a watery fluid called cell sap • • vacuolar membrane called the tonoplast • 2. Cell sap contains salts, sugars, organic acids, and may contain water-soluble pigments • called anthocyanins(red blue in color) • 3. Vacuoles are small and numerous in size in newly formed cells but increase in size as cell matures

30. The Cytoskeleton • 1. Microtubules • a. Unbranched, thin, hollow tube-like structures • b. Composed of protein • c. 15-25 nm in diameter and of various lengths • d. Found inside plasma membrane, help control the addition of cellulose to the cell wall • e. Other functions, vesicle transport, motility of flagella and cilia, and component of mitotic spindle

31. Microtubules

32. The Cytoskeleton cont. • 2. Microfilaments • a. Long protein filaments approximately 6 nm in diameter • b. Often grouped together in bundles • c. Function in cytoplasmic streaming and as part of the framework of the cell

33. The Cytoskeleton cont. • 3. Cyclosis • a. cytoplasmicstreaming exhibited by all living cells • b. Function • • facilitates exchange and movement of materials within a cell • c. Movement • • microfilaments and microtubules are thought to be responsible for generating the movement of the cytoplasm

34. Higher Plant Cells versus Animal Cells

35. A. Unique Structures of Plant Cells • 1. Cell walls • 2. Plasmodesmata • 3. Cell plate

36. B. Minor Differences • 1. Plant cells lack centrioles • • animal cells have these • 2. Plant cells contain plastids • • animal cells have none • 3. Vacuoles, common in plant cells • • either small or absent in animal cells

37. Turks cap lilly