Chapter 7: Cell Structure and Function The Discovery of the Cell

1. Chapter 7: Cell Structure and FunctionThe Discovery of the Cell • Early Microscopes allowed us to see cells for the first time! • The earliest lenses in Europe allowed us to see the quality of cloth and tiny insects, which appeared small and blurry. • Scientists didn’t use microscopes to study nature until the 1600’s. 7-1 Life is Cellular

2. Anton van Leeuwenhoek(1632-1723) Discovered the new world of microorganisms when he looked at pond water through his microscope. Leeuwenhoek greatly improved the quality of lenses

3. “Cells” named by Robert Hooke Robert Hooke was one of the first to look at objects under the microscope. Robert Hooke looked at cork (from the Cork Oak Tree). He thought the compartments looked like little rooms, or “cells”. The name stuck.

4. The History of the Cell Theory • In 1838, Matthias Schleiden stated that all plants are made of cells. • In 1839, Theodore Schwann stated that all animals were made of cells. • In 1855, Rudolf Virchow stated that cells could only come from other cells. - This is unlike how we bake cakes or build automobiles.

5. The Cell Theory • All living things are made of cells. • Cells are the basic units of structure & function in living things. • New cells are produced from existing cells.

6. Cells come in all shapes & sizes But, all cells have 2 characteristics in common: • They have a cell membrane at some point in their lives. • They contain DNA.

7. There are 2 categories of cells: • Prokaryotes • Cells that do not have a membrane-bound nucleus. • Eukaryotes • Cells that do have a membrane-bound nucleus. • Pro = before • Eu = true • Karyon=kernel

8. The type of cell is based on the presence (or absence) of a nucleus & organelles. • Nucleus –large membrane bound organelle. • Contains the cell’s DNA. • Controls many of the cell’s activities. • Organelle –specialized structure that performs important functions w/in the cell. • “Tiny organs”

9. Prokaryotes • The first cells (bacteria) • Generally smaller & simpler than eukaryotic cells. • Have DNA, but it’s not contained in a membrane-bound nucleus. • Most are unicellular. • Despite their simplicity, prokaryotes: • Grow • Reproduce • Respond to their environment • Some are mobile.

10. Eukaryotes • Generally larger & more complex than prokaryotes. • Contain membrane bound organelles and a nucleus. • Can be unicellular or multicellular. • Found in animals, plants, fungi, and protists

15. Pro-k vs. Eu-kReview Prokaryotes Eukaryotes Nucleus Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Mitochondria Cytoskeleton Cell membrane Contain DNA

16. Plant vs. Animal Cell Cell Wall Chloroplasts Animal Cells Plant Cells Cell membrane Ribosomes Nucleus Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Mitochondria Cytoskeleton Centrioles

17. Cell Structures 7-2 Cell wall – provides support & protection for a cell Cell walls are found in plants, algae, fungi, and most prokaryotes But, NOT animals! Cell walls are made from fibers of carbohydrates and proteins (p. 173) Follow along in your textbook...

18. Cells can be subdivided into 2 main parts: 1.Cytoplasm – portion of the cell between the nucleus and the cell membrane. Includes the organelles Do not confuse the cytoplasm with the cytosol... Analogy: cytoplasm is like vegetable soup cytosol is like the broth

19. 2. Nucleus – the control center of the cell • Contains almost all of the cell’s DNA, the coded instructions for making proteins & other important molecules. The nuclear envelopeis a double membrane that surrounds the nucleus. Found in eukaryotic cells only • On the nuclear envelope you will find • nuclear pores. These pores allow • materials to move in & out of the nucleus • Proteins • RNA • Other molecules (p. 175)

20. Chromatin –a granular material visible w/in the nucleus. • It consists of DNA tightly coiled around proteins. • Most of the time chromatin is spread throughout the nucleus. • However, when a cell divides, chromatin condenses to form chromosomes.

21. Another structure found in most nuclei is a nucleolus. • The nucleolus assembles ribosomes. (p. 176) Figure 7-7

22. Analogy...Comparing the Cell to a Factory • Organelles– means “little organs”. • Specialized structures that carry out specific functions in a cell... They each have a job to do. Organelles are found within the cytoplasm. As we learn about each organelle, we can compare it to parts of a factory. For example: the nucleus is like the boss who sends out instructions... DNA. Now lets look at organelles: ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, mitochondria, and chloroplasts

23. Ribosomes Ribosomes –small particles of RNA & protein found throughout the cytoplasm. • Ribosomes make proteins by following coded instructions that come from the nucleus. • These instructions are RNA (ribonucleic acid) • Cells that are major protein producers often have numerous ribosomes. ... Like an assembly line (p. 177)

24. Endoplasmic reticulum • Endoplasmic Reticulum (ER)– organelle in which components of the cell membrane are assembled and some proteins are modified. There are 2 portions to ER... Rough ER and Smooth ER • Rough ER • Involved in the synthesis of proteins. • Called “rough” b/c ribosomes are found on its surface • Newly made proteins enter the rough ER & are modified. • Smooth ER • No ribosomes are found on the surface • Contains collections of enzymes that perform special • tasks such as: Synthesis of membrane lipids • Detoxification of drugs • Liver cells tend to have a large amounts of smooth ER.

25. Rough and Smooth Endoplasmic reticulum Cross section of ER • RER • SER

26. Golgi Apparatus Proteins made in the ER move to the Golgi Apparatus (GA) The GA looks like a stack of closely opposed membranes, (or a stack of pita bread) • These proteins can be stored in the cell or secreted out of the cell.

27. Golgi apparatus See Figure 7-9 Factory analogy: Like a factory’s customized shop, where finishing touches are put on the products. Sequence pathway of proteins ... Central nucleus  Interconnected rough ER  Golgi  Outer plasma membrane

28. Lysosomes The clean up crew, Or recycling container Lysosome –small organelles filled w/ digestive enzymes. • Lysosomes are involved in: • Breaking down old organelles. • Digesting foreign matter in the cell.

29. Tay-Sachs -adisease is caused by lysosomes that fail to properly do their job. Fatal by the age of 4. More common in eastern European Jews Example of what can happen when cells don’t work

30. Vacuoles and Vesicles • Vacuoles –an organelle that stores materials such as: • Water • Salts • Proteins • Carbs • Plants have large central vacuoles that can hold water & wastes. Factory analogy – Storage and shipping containers Smaller vacuoles, especially those that transport substances within a cell, are called vesicles. (p. 179) Figure 7-10

31. Mitochondria & Chloroplasts • The power plants of a cell. • Most cells get their energy (E) in 2 ways: • Food (Heterotrophs) • Sun (Autotrophs)

32. Mitochondria: Can be found in almost all eukaryotic cells. Including plant cells. Converts chemical E into compounds that are easy for the cell to use. Ex: ATP (Adenosine Triphosphate) These high energy compounds are used to power growth, development, and movement (p. 180)

33. Mitochondria are enclosed by 2 membranes. • An outer membrane • An inner membrane • Highly folded on itself. • Creates more surface area for chemical reactions.

34. Chloroplasts: • Found in plants & some other orgs. • They capture sunlight & convert it into chemical E by photosynthesis. • This chemical E is then converted to ATP by mitochondria in the plant. • Also surrounded by 2 membranes. • Contains a green pigment called chlorophyll.

35. Chloroplasts

36. Organelle DNA • Chloroplasts & mitochondria contain their own DNA. • No other organelles do. • It is believed that both of these organelles are ancient descendants of prokaryotes. • This is called the endosymbiotic theory.

37. Cytoskeleton • Cytoskeleton –a network of protein filaments that helps the cell maintain its shape. • It is also involved in movement. • The cytoskeleton is made up of: • Microfilaments • Microtubules

39. Microfilaments: Threadlike Made of actin Forms a tough, flexible framework that supports the cell. Also responsible for cytoplasmic movement of the cell.

40. Microtubules: Hollow tube-like structures Made of tubulin Critical to maintaining cell shape. Also form structures called spindles during cell division. Tubulin is also used to make centrioles. Located near the nucleus. Help organize cell division. Microtubules also help w/ movement. They make up cilia & flagella. P. 181, fig. 7-11

46. Section 7-3 Cell Boundaries

47. Cell Boundaries 7-3 • All cells are surrounded by a thin barrier called the cell membrane. • Many cells also have a strong supporting layer around that membrane called the cell wall.

48. Cell Membrane • Cell membranes regulate what enters & leaves a cell. • They also aid in protection & support. • Nearly all cell membranes are a flexible, doublelayered sheet called a lipid bilayer. • P. 182, fig. 7-12

50. Along w/ lipids, the cell membrane also has proteins & carbohydrates embedded in it. The lipid bilayer is often called a mosaic, b/c it is made up of many different parts.