Cell Structure and Function Unit 7

1 Robert Hooke named cell while looking at cork in 1665

2 Anton van Leeuwenhoek saw tiny organisms in pond water in 1674 called them “animalcules”

3 The cell theory states: All living things are composed of cells. (1838 Schleiden said all plants; 1839 Schwann said all animals) Cells are the basic units of structure and function in living things. New cells are produced from existing cells. (1858, Rudolf Virchow)

4 Tools of the trade: Light vs. Electron

5 electron microscopes 1000 times better magnification than light microscopes must be placed in a vacuum chemically preserve their samples first and then carefully remove all of the water transmission electron microscopes (TEMs) must be cut first into ultrathin slices so that you can see what is inside scanning electron microscopes (SEMs) produces stunning three-dimensional images See the surface

7 Even though cells come in all shapes and sizes, what do all cells have? DNA Cell Membrane What are the levels of organization for a living thing? Cell – Tissue – Organ – Organ System In order to have different tissues and organs, cell must specialize for different functions.

Carry out all 8 characteristics of living things, but… No nucleus Usually smaller and simpler Usually unicellular organism Example: bacteria

9 prokaryotes - monerans

10 Have a nucleus Contain several structures and internal membranes Can be unicellular (protists) or multicellular organisms Larger, more complex, and have a large diversity (specialized)

11 Prokaryotes vs. Eukaryotes

12 Nucleus: the control center Contains DNA that contains the code to make proteins and other important molecules Has double-layer membrane with pores Has a nucleolus, which is a small dense region where ribosomes are made

13 Cytoplasm Fluid-filled portion of the cell outside the nucleus Organelles are found here; literally means “little organs”

14 Vacuoles: Storage Saclike membranes that store things like water, salts, proteins and carbohydrates

15 Specialized Vacuoles In plants, have one central vacuole that stores water that helps hold cell shape with water pressure Contractile vacuoles in some protists contract to expel water from the cell

16 Lysosomes: the clean-up crew Small organelles filled with enzymes Break down lipids, proteins and carbohydrates into smaller molecules that the cell can use Break down old organelles and other unwanted/foreign material All animals have these and some specialized plant cells

17 Cytoskeleton: structure Helps the cell maintain shape and helps with cell movement Help with internal organization Helps with transport within the cell, acting as a conveyor belt

The cytoskeleton is made up of microfilaments and microtubules 18 The cytoskeleton is made up of microfilaments and microtubules Microfilaments: thin structures that help with support and cell movement (contract and relax for amoebic movement) Microtubules: important for cell shape and cell division

19 Centrioles Microtubules found only in animal cells near the nucleus Help organize chromosomes on a network of microtubule fibers during cell division

20 Cilia and Flagella Microtubules found on the cell surface that help with movement Always in a 9 + 2 arrangement

21 Ribosomes: the machine! Where proteins are assembled Made of RNA and protein Found in the cytoplasm and attached the ER

22 Endoplasmic Reticulum (ER) ER with ribosomes attached is called Rough ER Rough ER - Modify proteins made by the ribosomes that will be released/secreted from the cell or incorporated into the cell membrane Once the proteins are modified, they leave the ER by pinching off into a vesicle Found around the nucleus Help transport materials in the cell

23 Smooth ER Smooth ER (no ribosomes attached) is key in creating cell membrane lipids and detoxifying (drugs)

24 Golgi Apparatus Stack of flattened membranes Vesicles containing proteins leave the ER and then merge with the Golgi Apparatus Here the proteins are modified, sorted and packaged either for storage in the cell or to be transported outside the cell They are then shipped out through another vesicle

25 Making a Protein DNA is encoded into mRNA in the nucleus mRNA leaves the nucleus to go to the ribosomes Ribosomes read the mRNA and create a protein based on the code Proteins enter the Rough ER for modification and then are shipped via vesicles Vesicles merge with Golgi Apparatus where they are further modified and then packaged and shipped out through another vesicle

27 Chloroplasts Found in plants and other photosynthetic organisms Capture energy from the sun and convert it into a glucose (contains chemical energy): photosynthesis Two membranes Contain stacks of membranes called granum Contain chlorophyll – green pigment that absorbs light

28 Chloroplasts

29 Mitochondria: the power plant Found in nearly all eukaryotic cells Convert chemical energy in glucose into energy that the cell can use easier (ATP) Have two membranes Inner membrane is folded up inside the organelle

30 Endosymbiotic Theory Mitochondria and chloroplast both contain DNA So, theory proposes that a symbiotic relationship between primitive eukaryotic cells and the prokaryotic cells within them over time evolved into the eukaryotic cells we know today

31 Cell Wall To support, shape and protect the cell; rigid Lie outside the cell membrane Porous to allow things like water, O2, and CO2 to pass easily In plants (cellulose) and prokaryotes

32 Cell Membrane: traffic control ALL cell have them! Flexible lipid bilayer that regulates what enters and leaves the cell, and also protects and supports

33 lipids in the cell membrane Hydrophobic tails are “protected” from water by forming a double layer with only the hydrophylic end coming in contact with water

34 Fluid Mosaic Model Various proteins are contained within the cell membrane, and many of these may have carbohydrate chains attached The variety creates a mosaic These proteins are able to move freely among the lipids in the lipid bilayer, making it appear to be a fluid

35 Fluid Mosaic

36 What do the proteins and carbohydrates do in the cell membrane? Proteins serve as channels and pumps to help move things in and out across the cell membrane Some proteins have a carbohydrate chain attached, and these serve to help cells recognize other cells like an identification card

37 Selectively Permeable Describes cell membranes because some things are allowed to enter and others are not Also called semi-permeable

38 Plant vs. Animal Cells

39 Cell Specialization We have seen the difference in prokaryotes and eukaryotes, and.. We have seen the difference in plant and animal cells. The human body contains 210 different types of cells out of the approximate 100 trillion cells in your body! These cells vary in shape, size, and the amount of organelles that they contain, all dependent upon the cell’s function

40 Different Human Cells