1. Unit 3 Obj. 1.1.1, 1.1.2 Cell Structure

2. What is a cell? • The basic unit of life • Discovered in 1665 by Robert Hooke • He thought they looked like the rooms monks lived in, so he called them “cells”

3. Cell History Continued • Anton van Leeuwenhoek used a hand held microscope to look at pond scum and scrapings from his teeth in 1673 • He thought they look like little animals

4. What kinds of cells are there? • Prokaryotes = no nucleus • Example: Bacteria • Eukaryotes = have a nucleus • Example: Animals, plants

5. What kinds of organisms are there? • Unicellular = made of only one cell • Multicellular = made of two or more cells

6. Cell Theory • Contributed to by Theodor Schwann and Matthias JakobSchleiden in 1839 and Rudolf Virchow in 1858. • Three main ideas: • 1. All living things are made of cells. • 2. Cells are the basic unit of structure and function in all living things. • 3. New cells come from pre-existing cells.

7. What are organelles? • Organelles are specialized parts of eukaryotic cells that have specific functions within the cells • Make the cell more efficient and complex

8. Nucleus • Contains the genes that control the cell = DNA • Chromatin = uncoiled DNA • Chromosomes = coiled DNA • Surrounded by nuclear envelope = double membrane • The “information center” of the cell

9. Nucleolus • Makes rRNA and assembles ribosomes • Not surrounded by a membrane • Cells can have 1-3 • Disappears when the cell divides

10. Plasma Membrane • Provides protection • Helps cell communicate • Transports substances in and out of cell • Keeps the cell together • Made of a phospholipidbilayer (phosphate head, lipid tail, two layers) • The head is hydrophilic (loves water), the tails are hydrophobic (fears water) • Selectively permeable

11. Mitochondria • Where the cell performs respiration makes ATP, a molecule the cell can use as energy for work • Major site of metabolism  the more mitochondria per cell you have, the higher your metabolism will be • Folded inner membrane (cristae)  more surface area for chemical reactions

12. Rough endoplasmic reticulum • Rough ER • Called “rough” because it is studded with ribosomes • Makes proteins • The “highway” of the cell  transports proteins

13. Smooth endoplasmic reticulum • Smooth ER • Lacks ribosomes • Makes lipids • Also the “highway” of the cell  an interconnected network of tubules and vesicles

14. Ribosomes • Protein synthesis = making proteins using RNA from the nucleus to assemble amino acids into proteins • Can be floating in cytoplasm or attached to a membrane

15. Lysosomes • Contain digestive enzymes • Digest food, worn out organelles, viruses, etc. • Can also act as a “self-destruct button” and cause the cell to lyse itself apoptosis • The “janitor,” “hit man,” and “suicide bomber” of the cell

16. Golgi Apparatus • Processes and packages macromolecules that are synthesized by the cell in vesicles (membrane bound packages) • Secretion • Found in eukaryotes only

17. Cytoskeleton • Made of protein – microtubules and microfilaments • “Framework” of cell • Provides structural support

18. Cytoplasm • Jelly-like substance that helps fill up the cell and suspend organelles • Site of many metabolic reactions

19. Plasmid • DNA molecule that is separate from and can replicate independently from chromosomal DNA • Usually found in prokaryotes

20. Flagellum • Tail-like projection from cell • Helps cell move by whipping around in a circle  similar to helicopter blade

21. Cilia • Small, hair-like projections • Used to help cell move and sense environment

22. Pseudopodia • “False foot” • Temporary projections of eukaryotic cells • Usually found in amoeba • Cells use extension and contraction to move around

23. Eyespots • Photoreceptive organelle = can sense light • Usually found in unicellular photosynthetic cells, like green algae • Allows the organism to respond to light and swim towards it or away from it

24. Centriole • Only found in animal cells • Made of microtubules • Help the cell divide

25. Cell Wall • Only found in plant cells • Shapes and supports the cell • Provides additional protection • Made of cellulose = humans cannot digest

26. Chloroplast • Found only in plant cells • Contains chlorophyll = pigment that gives plants their green color • Traps sunlight to make glucose (food) • Site of photosynthesis

27. Vacuole • Stores water, sugar, salts, nutrients, wastes, etc. • Large and central in plant cells • Small or not present in animal cells

28. Plant cells vs. Animal cells

29. To be or not to be… multicellular • What are some advantages? • Differentiation each cell performs a specific task, allowing the organism to be more efficient • More control over internal conditions • Greater motility  able to move around and avoid predators and find more food • Genetic diversity  greater chance for positive traits • What are some disadvantages? • Harder to reproduce  must find a mate first • Need more resources

30. Some different cells in our bodies

31. Cell Differentiation • Different cells have specific jobs and functions • Can only happen in multicellular organisms • Structure determines function • For example: • In humans, muscle cells are extra long and narrow with multiple nuclei. • However, the doughnut-shaped red blood cells lose their nuclei early in their development and contain hemoglobin, which binds to oxygen.

32. How do cells differentiate? • Start out as stem cells = unspecialized, “blank slate,” can become any cell in the body • Development is usually triggered by hormones  cells start to specialize

33. Cell communication • Cells use multiple methods to communicate • Electrical or chemical signals • Recall: The cell membrane is made of a phospholipidbilayer with hydrophobic and hydrophilic parts. • It is called the fluid mosaic model fluid = hydrophobic inner layer slides around, mosaic = made of different parts, such as proteins and lipids • Studded with transport proteins and receptors so things can pass through

34. Why is it important for cells to communicate? • Cells can sense changes in environment • Processes can be activated or deactivated • Cells can communicate with other cells

35. Electrical Signals • Cells are very, very close together • Gap junctions = pores in cell membranes that touch another pore in an adjacent cell membrane • Nerve cells(neurons)= cells that are specialized to send signals through the body in one direction only • Messages can be voluntary or involuntary • 2 main parts of a neuron = axon and dendrite

36. Chemical Signals • Can be very long distance  hormones are special proteins that get released into the bloodstream and travel around the whole body • Must be VERY specific to make sure that the right cell receives the message • Receptor = part of cell that receives the message • Can be very short distance or moderate distance