Chapter 7: Cell Structure

1. Chapter 7: Cell Structure

2. Section 1: Introduction to Cells • Cells – the smallest unit of life; all living things are made of one or more cells • Robert Hooke – English monk in 1665; observed cork under a microscope & saw “little boxes”. Named these “boxes” cells after the rooms monks lived in.

3. Anton van Leeuwenhoek – Dutch 1673; first to observe living cells

4. II. Cell Theory • Evidence for Cell Theory: • Matthias Schleiden – proposed all plants are made of cells • Theodor Schwann – proposed all animals are made of cells • Rudolf Virchow – proposed all cells come from other (preexisting) cells

5. Three Components of cell theory: • All living things are made of one or more cells. • Cells are the basic unit of structure & function in an organism. • Cells only come from the reproduction of other living cells. • Modern Cell Theory also includes: • Energy flow occurs within cells • Heredity information (DNA) is passed on from cell to cell • All cells have the same basic chemical composition

6. III. CellDiversity • Looking at cells • Size – range from microscopic to visisble with naked eye. • Limited by a cell’s surface area-to-volume ratio • If cell is too large, it takes too long for materials to travel through it • Shape – spheres, cubes, flat, have extensions (branched), smooth or rough surfaces.

7. Examples of Cell Shapes

8. IV. Cell Features • Internal Organization = how the inside is divided into regions/areas for specific functions. • Cell Membrane – cell’s outer boundary • Cytoplasm – fluid cytosol & any cellular structures suspended in cytosol

9. Nucleus – cellular structure that houses DNA • Organelles – membrane-bound cellular structures that carry out specific functions in a cell

10. Types of Cells • Eukaryotes – cells with membrane-bound organelles & nucleus • Prokaryotes – lack membrane-bound organelles & nucleus

11. Section 2: Inside the Eukaryotic Cell • Cell Membrane – outer layer that surrounds the cell that allows nutrients & wastes in and out of the cell • Selectively Permeable – some materials are allowed through, either in or out of the cell • Made of . • Due to the make up of the cell membrane, only certain materials can pass through it.

12. Cytoplasm – gelatin-like aqueous fluid (cytosol) & the organelles suspended in it • Vesicle – small, spherical membrane sac that transports proteins

13. Directing Cell Activity • Nucleus – “brain” of the cell; directs all cell activities, cell division, & the making of proteins (DNA is stored here) • Nuclear Envelope – double membrane around nucleus; has pores (holes) that allow certain molecules in or out • Nucleolus – spherical area inside the nucleus that makes RNA & ribosome parts.

14. Ribosomes – made of RNA & proteins • Makes proteins • Can find them floating free in the cytoplasm (“free”) or attached to the E.R. (bound).

15. IV. Protein Processing Organelles • Endoplasmic Reticulum – system of internal membranes • Rough E.R. – covered with ribosomes; aids ribosomes in making proteins & transporting them by making vesicles • Smooth E.R. – not covered with ribosomes; makes steroids, breaks down toxins, & regulates calcium levels

17. Golgi Apparatus – system of flattened membranes • Modifies, packages, and secretes different molecules in vesicles. • Assists E.R. in modifying proteins that are leaving the cell.

18. V. Energy Production Organelle • Mitochondria – “power house of the cell” • Makes ATP! • Has a 2nd, inner membrane that has folds called cristae. • Has its own DNA.

19. VI. Other Organelles • Lysosomes – contains enzymes that digests proteins, DNA/RNA, old organelles, bacteria, etc. • Vacuoles – can help maintain water concentrations, store food, etc. • Cillia & Flagella – both help move the cell • Cilliaare tiny hairlike projections. • Flagella is a single long whip-like tail

21. VII. Framework of the Cell • Cytoskeleton – web of protein fibers that supports the cell & its organelles • Microfilaments – long thin fibers of the protein actin; pulls the membrane in & out in some places • Microtubules – thick hollow fibers of the protein tubulin; molecules move through it • Intermediate Fibers – moderately thick & anchors organelles in place

23. VIII. Plant Cells – have some organelles not present in animal cells • Cell Wall – rigid, inorganic layer surrounding the cell membrane; made of cellulose & other carbohydrates

24. Central Vacuoles • Fluid-filled organelles that store water, ions, enzymes, & wastes • Can take up 90% of the space/volume of a cell • Chloroplasts • Have two membranes & their own DNA • Absorb sun light & converts it to food (photosynthesis)

25. Plant Cell

26. Animal Cell

27. Section 3: From Cell to Organism • Diversity in Cells • Prokaryotes – cells that lack membrane-bound organelles & nucleus • Vary in shape, how they obtain food & use energy, makeup of the cell wall, & how they move. • Flagella • Pili– short, thick outgrowths; attach prokaryote to surfaces or other cells

28. Prokaryote Cell

29. Eukaryotes – cells with membrane-bound organelles & nucleus • Animal vs. Plant Cells • Eukaryote cells vary in internal makeup so that cells can become specialized for certain functions • Muscle cells use large amount of energy, so they contain many mitochondria!

30. II. Levels of Organization Cells  Tissues  Organs  Organ System  Organism • Tissues – group of cells that have similar structures & functions • Muscle tissue, bone tissue, vascular tissue in plants • Organs – different tissues arranged together to perform a specific function • Heart, lung, leaf

31. Organ System – group of organs that work together to perform a set of functions, or a major body function • Circulatory system, shoot systems of plants • Organism – interaction of all organ systems to carry out all life processes • Human, Oak tree

32. Levels of Organization

33. III. Body Types • Unicellular – entire body of an organism is one cell • Colonial – cells that live as a connected group but do not depend on each other for survival • Multicellular – cells are specialized to perform one or a few functions of life • Differentiation – process by which cells develop specialized forms & functions • Life depends on the interaction of all the cells!

34. Unicellular, Colonial, & Multicellular