Chapter 4

1. Chapter 4 Cell Structure and Function

2. 1. What is a cell? • A cell is the smallest unit that can carry on all of the processes of life.

3. 2. Early scientists that led to the cell theory: • Anton van Leeuwenhoek (1600s) – given credit for developing the 1st mini microscope, looked at pond water and made detailed drawings • Robert Hooke – coined the term “cell” when he looked at slices of cork and dead plant cells • Robert Brown (1833) – observed a dark structure near the center of the cell (we now know this is the nucleus) • Matthias Schleiden (1838) – stated all plants are made of cells • Theodor Schwann (1839) – discovered all animals are made of cells • Rudolph Virchow (1855) - stated all cells come from the division of preexisting cells

4. 3. Cell Theory • All living things are composed of cells. • Cells are the basic units of structure and function in living things. • All cells come from preexisting cells.

5. 4. 8 Characteristics that all living things share • Consist of organized parts (cells) • Obtain energy from their surroundings • Perform chemical reactions • Change with time (evolution) • Respond to their environments • Reproduce • Maintain constant internal environment (homeostasis) • Share a common history

6. 5. Relationship between a cell’s shape and it’s function Nerve cells: communication • Diversity of shape reflects diversity of functions • Can be simple or complex depending on its function • Cell shape evolved to allow the cell to perform its function effectively Skin cells: protection Blood cells: transport

7. 6. What factor limits the size that most cells are able to obtain? • Limited by the relationship of the cell’s outer surface area to its volume • Most cells range from 10 -100µm

8. 7. What is the problem with cells getting too large? • As a cell grows, it’s volume increases much faster than its surface area • The surface area (the membrane) would not allow materials to enter or leave the cell quickly enough to meet the cell’s needs. • Therefore, most cells are microscopic in size.

9. 8. Three Basic Parts of the Cell: • Plasma Membrane – regulates what enters and leaves the cell • Cytoplasm – site of many chemical reactions of the cell • Material between the cell membrane and the nucleus • Contains the organelles of the cell • Control Center – controls all of the cells activities • Either free-floating DNA in center of the cell (Prokaryotes) OR a membrane bound organelle called a nucleus (Eukaryotes)

10. 9. Two basic types of cells • Prokaryotes – organisms whose cells lack nuclei and other organelles (i.e. bacteria) • Eukaryotes – organism whose cells contain nucleiand other organelles Pro- = before Eu- = true -karyon = kernel/nucleus

11. 10. What is an organelle? • A well-defined, intracellular body that performs specific functions for the cell. • Ex/mitochondrion produces energy (in the form of ATP) for the cell

12. Prokaryote vs. Eukaryote Typical Prokaryote (a bacterium):

13. 11. Prokaryote vs. Eukaryote

14. 11. Units of Organization CELLS  TISSUE  ORGANS  ORGAN SYSTEM  ORGANISM

15. 12. PROKARYOTIC CELL DIAGRAM CELL WALL – protection PILI – used for attachment to surfaces CELL MEMBRANE – Regulates what enters and leaves DNA – controls all cells activities FLAGELLA – moves the cell RIBOSOME – makes proteins

16. Animal Cell cytoplasm Nucleus Nucleolus Nuclear envelope Rough ER mitochondria lysosome ribosomes Cell (Plasma) membrane Golgi apparatus Smooth ER

17. Plant Cell *’s = organelles only found in plant cells, NOT animal cells Rough ER Nuclear envelope Smooth ER Nucleus Nucleolus * Central Vacuole * Golgi Apparatus Mitochondria * Cell Wall * Cytoplasm Cell (Plasma) membrane * Chloroplast *

18. Cell Membrane – outer boundary • In plants & animals • Structure: • Phospholipid bilayer • hydrophilic heads, hydrophobic tails • Contains lipids (bilayer), proteins (channels), and carbohydrate chains (identification cards) • Function: • Regulates what enters and leaves the cell • Semi-permeable membrane • Protection and support

19. Nucleus - control center • In plants and animals • Structure: • Genetic material called chromatin (DNA + proteins) • Function: • Information center of the cell • Protects DNA • Directs/controls cell activities

20. Nucleolus - • In plants & animals • Structure: • Made of RNA + proteins • Small, darkened region inside of nucleus • Function: • where ribosomes are made

21. Mitochondria • In plants & animals • Structure: • Double membrane • Cristae - inner folds, increase surface area • Outer membrane for protection of organelle • Function: • “Powerhouse” of the cell – produces ATP’s (cell energy) • Able to self-replicate ( # in cells with high energy need) • Releases energy from food for the organism to use in the process of cellular respiration

22. Ribosomes • In plants & animals • Structure: • Little “dots” • Small (25 nm) ball-like structures • Found free-floating in cytoplasm or attached to rough endoplasmic reticulum • Composed of RNA and protein • Function: • Synthesis of proteins (where proteins are made)

23. Endoplasmic Reticulum • In plants & animals • Structure: • Network of flattened sacs • Can be rough (w/ ribosomes) or smooth (w/o ribosomes) • Function: • Transport materials within or out of cell – intracellular highway • Synthesis of macromolecules • Rough - proteins, lipids, carbs • Smooth - lipids

24. Lysosome • In animals only • Structure: • Small, circular structures • Found only in animal cells • Contain digestive enzymes • Function: • Digestion of: • Worn out organelles • Debris • Large ingested particles • Lysosomes are responsible for your hands not being webbed!!

25. Golgi Apparatus • In plants & animals • Structure: • Flattened stacks of membranes that are not connected • Vesicles fuse with Golgi and get released from Golgi • Function: • Collection, modification, packaging of proteins and other substances • Vesicles attach, deposit materials • Golgi modifies materials based on needs • Vesicles attach to membrane and distribute modified substances

26. Vacuole • In plants - 1 large, central • In animals – several small • Function: • Storage of water, salts, proteins, carbohydrates, waste products • Pressure system for plants, prevents wilting • Special vacuole: contractile vacuole - prevents excess water intake, leading to cell-bursting found in freshwater PROTISTS like a paramecium

27. Cell Wall – • Only in plants, bacteria, fungi • Structure - • Lies outside the cell membrane • Made of fibers of cellulose (plants) • Very porous • Function • Helps to protect and support the cell • Gives rectangular shape to plant cells

28. Chloroplasts • Only in plants • Structure: • Inner membranes (thylakoids) surrounded by an outer membrane • Function: • Conversion of light energy (sun) into chemical energy (glucose/food) during the process of PHOTOSYNTHESIS • Other Plastids: • Chromoplasts – Store pigments (ex. carrot root cells, flower petals) • Amyloplasts - Store food/starch

29. Cytoskeleton - framework • In plants– microtubules, intermediate filaments, microfilaments • In animals– all • Function: maintains cell shape and provides internal support • Microtubules - hollow tubes of proteins, hold organelles in place, maintain shape, act as tracks that guide organelle movement • Intermediate filaments – rods that anchor organelles in place • Microfilaments – long & threadlike, used for cell movement • Cilia – short, hairlike projections used for cell movement • Flagella – long, taillike projections used for movement • Centrioles – organize microtubules during cell division

30. Who Am I? (quick review) • I stated all plants are made of cells • I stated all cells come from the division of preexisting cells • I coined the term “cell” when I looked at slices of cork and dead plant cells • I am given credit for developing the 1st mini microscope and I looked at pond water and made detailed drawings • I discovered all animals are made of cells

31. List 3 organelles you learned about today. • Describe the function of each of the organelles you listed. • Yes, you should write your name on the paper