Chapter 7: Cell Structure and Function

1. Chapter 7: Cell Structure and Function 7-1 Life is Cellular A. Discovery of the Cell 1. Scientists who contributed to cell discovery a. Robert Hooke -Discovered tiny chambers in cork -named chambers cells b/c reminded of cells in monastery b. Leeuwenhoek -used microscope to see “animalcules”— tiny living organisms in water c. Schleiden -plants made of cells d. Schwann -animals made of cells e. Virchow -new cells come from division of existing cells

2. f. Cell Theory -cells are basic unit of life -all living things composed of cells -new cells produced from existing cells B. Prokaryotes and Eukaryotes 1. Nucleus (nuclei) a. Membrane enclosed structure which contains genetic material (DNA) b. Controls cell activities 2. Two (2) categories of cells a. Eukaryote -contains nucleus separated by membrane from rest of cell -specialized structures and membranes -unicellular or multicellular -larger, more complex cell type

3. b. Prokaryote -does not have a nucleus to enclose genetic material (DNA found within the cell) -less complex, no specialized structures -unicellular, must perform all characteristics of life -bacteria 7-2 Eukaryotic Cell Structure A. Comparing Cell to a Factory 1. organelles a. Cell structures w/specialized function b. “little organs” 2. Two (2) major parts a. Nucleus b. Cytoplasm -area outside nucleus which contains organelles

4. B. Nucleus 1. contains cell’s DNA instructions for making proteins 2. surrounded by nuclear envelope w/pores (materials can move in/out) 3. chromatin a. Granular material b. Composed of DNA bound to protein c. Long strands 4. Chromosomes a. Condensed (compacted) chromatin 5. Nucleolus a. Dense region inside nucleus b. Beginning of ribosome production/assembly

5. C. Ribosomes 1. small particles of RNA and protein 2. produces proteins following DNA instructions from nucleus 3. smallest organelle 4. two types -free -attached

6. D. Endoplasmic Reticulum (ER) 1. Two types a. Rough ER -studded w/ribosomes -site of protein synthesis -modifies (changes) proteins -exports proteins b. Smooth ER -no ribosome attachment -contains enzymes w/specialized tasks -ex: breaks down drugs in liver makes cell membrane lipids

7. E. Golgi Apparatus 1. modifies, sorts, packages proteins from ER 2. proteins are stored or secreted for use F. Lysosomes 1. organelles filled w/enzymes 2. breaks down or digest lipids, carbohydrates, proteins to be used by cell 3. breaks down organelles which have lost their usefulness 4. Animal cells only 5. Tay-Sachs disease a. Lysosomes do not function properly b. “junk” builds up in cell c. Fatal 6. “clean-up crew”

8. G. Vacuoles 1. Sac-like structures 2. Storage of water, salts, carbohydrates, proteins 3. plants a. Large, single vacuole b. Supports stems/leaves -wilting 4. animal or a single-celled organism a. Several small vacuoles b. Cell homeostasis c. Contractile vacuole-excess water is pushed out

9. H. Energy producing organelles 1. Mitochondria (mitochondrion-singular) a. converts stored food energy in useable form b. “powerhouse of cell” c. double-membrane (outer/inner membrane) d. humans inherit from female 2. Chloroplast a. plants only b. captures sunlight energy and converts into chemical energy (photosynthesis) c. double membrane d. contains chlorophyll 3. Organelle DNA

10. I. Cytoskeleton 1. protein filament network 2. used to maintain cell shape and movement 3. Two types of cytoskeleton a. Microfilament -threadlike -cell framework -movement b. Microtubules -tubule shaped -cell shape -mitotic spindles (centrioles) *only found in animal cells *used to separate chromosomes in cell division -cell movement by projection(s) *cilia (cilium-sing)—short, hair-like *flagella (flagellum-sing)—long, tail-like

11. 7-3 Cell Boundaries A. Cell membrane 1. regulates what enters/leaves cell 2. protection/support 3. found in plant and animal 4. lipid bilayer a. Flexible structure b. Strong barrier c. Composed of: -proteins *forms channels through membrane *allows movement in/out -carbohydrates *forms chains attached to outer surface of proteins *chemical ID cards for cell identification

12. B. Cell Wall 1. Found in plants, algae, many prokaryotes 2. outer most boundary 3. support/protection 4. fibers of carbohydrates/proteins 5. composed of cellulose a. Main component of wood/paper C. Diffusion Through Cell Boundaries 1. Concentrations a. Solution -mixture of 2 or more substances -solute—dissolved substance -solvent—what does the dissolving b. Measured as mass of solute in a given volume (mass/volume) -12 g NaCl in 3 liters H2O -12g/3 L or 4g/L

13. 2. Diffusion a. Particles in constant motion b. Definition— -PARTICLES move from area of more concentration to low concentration until particles are equally spread out (particles are in equilibrium) *after equilibrium is reached particles continue to move in fairly equal numbers (no change in concentration) c. Passive transport (no energy required)

14. D. Osmosis 1. Types of membranes a. Permeable -allows substances to pass through b. Impermeable -does not allow substances to pass through c. Selectively permeable -allows some substances to pass through, others not 2. Definition a. Diffusion of WATER through a selectively permeable membrane c. Passive transport b. handout

15. 3. Types of solutions (3) a. Isotonic (equilibrium) -same strength -equal amount of water movement -cell size does not change b. Hypertonic (concentrated) -above strength *more sugar to water -more water moves out -cell size shrinks c. Hypotonic (diluted) -below strength *less sugar to water -more water moves in -cell swells

16. 4. Osmotic Pressure a. Cells must balance water intake/loss by osmotic pressure b. Cells handle osmotic pressure by: -most large organism cells are isotonic *cell conc. are = #blood cells/plasma -plants have cells walls to withstand extreme pressure *with time the increased pressure makes plants more vulnerable to injury -unicellular organisms have contractile vacuoles to pump out excess water

17. E. Facilitated Diffusion 1. Molecules are facilitated (helped) across membrane 2. Protein channels allow movement of particular substances across different membranes (proteins are facilitators) a. Ex: RBC’s have protein channels to allow glucose only to pass in either direction 3. Passive transport F. Active Transport 1. Energy required to move molecules across membrane 2. Movement is against concentration difference (low to high concentration)

18. 3. Types of active transport a. Membrane-associated pumps (energy- requiring) -Ca, K, Na ion pumps in organisms b. Particle movement -endocytosis *particles/fluid are taken in by a pocket forming around it *pocket breaks off to form vacuole *2 types #phagocytosis—large food particle taken in #pinocytosis—fluids are taken -exocytosis *release of materials from cell (contractile vacuole)

19. 7-4 Diversity of Cellular Life A. Unicellular Organisms 1. must perform all characteristics of life 2. yeast, algae, bacteria (prokaryotes) B. Multicellular organisms 1. Cells are specialized to form specific task (cell specialization) 2. Specialized animal cell examples a. RBC—transport O2 b. Pancreas—food digestion, high in ribosomes, rough ER, Golgi apparatus, vacuoles c. Muscles—fibers (cytoskeleton- microfilaments) 3. Specialized plant cell examples a. Guard cells—regulates gas exchange in leaves

20. C. Levels of organization 1. Individual cell 2. Tissues (4 types) a. Similar type cells performing a particular function -epithelial, connective, muscle, nervous 3. Organs a. Groups of tissues that work together -muscle (heart)—muscle, connective, nervous tissues 4. Organ system a. Groups of organs work together to perform a specialized function b. 11 major systems 5. Organism