Biology 250

1. Biology 250 Chapter 4

2. Robert Hooke Microscopes opened a whole new world • Looked at cork under a microscope • Gave cells their name These remind me of the rooms monks sleep in which are called cells…. I shall call these little boxes cells!

3. Anton van Leeuwenhoek And this guy…. • 1st to look at living cells • Took scrapings of tartar from his teeth I saw “many small animalcules, the movement of which was pleasing to see!”

4. The Cell Theory • All living things are composed of one or more cells. • The cell is the basic unit of structure and function in all living things. • All cells come from the reproduction of existing cells. Proposed by Schleiden, Schwann and Virchow

5. So… why are cells so small? Surface Area to Volume Ratio: As a cell increases in size, the surface area increases with the square of the diameter but the volume increases with the cube. Eventually, the volume of the cell gets so large The cell cannot get nutrients to the center Or wastes to the surface fast enough. The cell dies.  Everything a cell needs to live has to come in through its surface. All wastes must leave through its surface.

6. Two Main Types of Cells Prokaryotic – Do NOT have a nucleus or organelles surrounded by membranes. These are BACTERIA. Eukaryotic – DO have a nucleus and organelles surrounded by membranes. Everything BUT bacteria! Animal Cell Plant Cell Organelle – A cell part which performs a function for the cell.

7. There are two main types of eukaryotic cells: Animal Cells and Plant Cells. Both contain many of the same organelles. Aaaaaaand yes, you have to be able to name and describe all of them.

8. Organelles of the animal cell • Cell Membrane: • Surrounds all cells. • Controls what enters and leaves the cell • Selectively Permeable – Only allows certain substances to enter/exit the cell. • Composed of a lipid (fat) bilayer (2 layers of a special kind of fat called a phospholipid)

9. Fluid Mosaic Model: The cell membrane behaves as a fluid. Phosolipids and both types of proteins can move around freely. Contains 2 layers of phospholipids. The type of fat that makes up the membrane. Also contains 2 types of proteins: Peripheral Proteins – Located on the inner surface or outer surface of the membrane. Integral Proteins: Located inside of the membrane. This is a model of the cell membrane.

10. Organelles of the animal cell Cytoplasm: The clear, jelly-like substance which makes up the bulk of the cell. • Mitochondrion • Makes ATP (energy) for the cell. • Nicknamed: The Powerhouse of • the cell. • Has two membranes, an inner • membrane and an outer • membrane.

11. Ribosomes – Located free floating in the cytoplasm OR embedded in the rough endoplasmic reticulum. FUNCTION: make proteins Organelles of the animal cell • Endoplasmic Reticulum • Acts as an intracellular highway. • Two Types • Rough ER – Studded with ribosomes. Makes proteins for export. • Smooth ER – Breaks down toxic substances.

12. Organelles of the animal cell Golgi Apparatus: Processes and packages proteins for export. Lysosomes: Contain digestive enzymes. Break down old & worn out organelles, cellular debris and wastes. They say it looks like a stack of flattened pancakes!

13. Some cells also have the ability to move. Those cells have one of the following: Organelles of the animal cell Flagellum: Long, and whiplike. Enables movement. Cilia: Short, hairlike, very numerous. Enable movement. Cytoskeleton The cytoskeleton is a network of fibers called microtubules and microfilaments. It provides structure and support to the cell.

14. Let’s look at the nucleus: The nucleus controls the activities of the cell. Organelles of the animal cell Nuclear Envelope: The double membrane that surrounds the nucleus. Contains pores to allow material to enter/exit. Nucleolus: Round ball inside the nucleus which makes ribosomes. Chromatin: The DNA of the cell in it’s unwound form.. When it’s wound up, it becomes chromosomes.

15. Organelles of the animal cell • Cell Membrane • Cytoplasm • Mitochondrion (mitochondria) • Endoplasmic Reticulum • Smooth ER • Rough ER • Ribosomes • Golgi Apparatus • Lysosomes • Cytoskeleon • Flagellum (flagella) • Cilia (cillium) • Nucleus • Nuclear Envelope • Nucleolus • Chromatin

16. Break Time

17. Review Time! Can you give the function of these organelles? Cell Membrane Ribosomes Nucleus Cytoplasm Flagellum Nuclear Envelope Cytoskeleton Cilia Nucleolus Endoplasmic Reticulum Mitochondrion Chromatin Smooth ER Lysosome Golgi Apparatus Rough ER

18. Plants have most of the organelles that animals do (except the ones for movement) plus 3 more! Vacuole: Takes up a lot of space! Filled with fluids and wastes. Chloroplasts: Contain the green pigment chlorophyll and make food for the plant through photosynthesis. Cell Wall: Rigid structure made of cellulose. Supports plant. Enables plants to stand upright.

19. Levels of Multicellular Organization • Some organisms are made from more than one cell and their cells are organized. • Tissue – A group of similar cells working together to perform a common task. • Organ – A group of tissues working together to perform a common task. • Organ System – A group of organs working together to perform a common task. • Organism – All the organ systems working together

20. Questions?