Chapter 3: Cell Structures

1. Chapter 3: Cell Structures 3.2: Cell Features and Cell Organelles Buck Salinas 2012

2. The Cell Theory • 1938: MattiasSchleiden concluded cells made up every part of a plant • 1939: Theodor Schwann claimed that animals were also made of cells • 1958: Rudolph Virchow determined that cells come only from other cells • These three observations form the CELL THEORY, which states: • All living things are made of one or more cells. • Cells are the basic units of structure and function in organisms. • All cells arise from existing cells. Buck Salinas 2012

3. Cell Size • Small cells function more efficiently than large cells. • This is because they have a high surface area to volume ratio. • We have lots of small cells so that all the substances that leave and enter cells have a large surface area to do it. If the surface area-to-volume ratio is too low, substances do not have enough space to move across. Buck Salinas 2012

4. Common Cell Features • Cells share common structural features, including: • Cell membrane • Cytoplasm • Cytoskeleton • Ribosomes http://visual.merriam-webster.com/animal-kingdom/simple-organisms-echinoderms/animal-cell.php Buck Salinas 2012

5. Common Cell Features • Cell Membrane: outer boundary of the cell, regulates what enters and leaves a cell • Cytoplasm: the cell interior, which contains many structures • Cytoskeleton: a system of microscopic fibers that suspend structures inside the cell • Ribosomes: cellular structures on which proteins are made • Additionally, all cells contain DNA (unless they lose their DNA later). Buck Salinas 2012

6. Prokaryotic Cells • Prokaryote: the smallest and simplest cells, single-celled organisms that lack a nucleus and other internal compartments (organelles). • Because they have no organelles, they cannot carry out many specialized functions. • The familiar prokaryotes that cause infection belong to a type of prokaryotes called bacteria. Buck Salinas 2012

7. Characteristics of Prokaryotes • Exist in a broad range of environmental conditions. • A prokaryote’s enzymes and ribosomes are free to move around in the cytoplasm because there are no internal compartments (organelles). • Prokaryotes have a cell wallsurrounding the membrane for structure and support. • Prokaryotes lack a strong internal support system. • Prokaryotes have a cell wall made of polysaccharides connected to amino acids. • Some cell walls are surrounded by a capsule which allows prokaryotes to stick to things! • Many prokaryotes also have flagella—long, threadlike structures for movement. Buck Salinas 2012

8. Eukaryotic Cells • Eukaryotes: an organism with a cell nucleus • Some eukaryote cells use flagella, others have hairlike cilia for movement. • Nucleus: an internal compartment that houses the cell’s DNA. • Organelles: an internal compartment that carries out specific activities in the cell. • A complex system of internal membranes connects some organelles inside the cytoplasm. Buck Salinas 2012

9. The Cytoskeleton • Provides the interior framework of an animal cell. • Composed of protein fiber network anchored to plasma membrane. • Three types of fibers: • Actin fibers: long slender microfilaments, shape the cell • Microtubules: hollow tubes, the highway system for transport of information • Intermediate fibers: provide a frame for ribosomes and enzymes Buck Salinas 2012

10. 09/14/12 DOL • 1-4. On the provided whiteboard, draw a basic cell and label 4 parts found in ALL cells. • 5. Next, draw something special that is only found in Eukaryotic cells that contains DNA and label this part. Circle the label.

11. The Cell Membrane • The inside of the cell (cytoplasm) is contained by the cell membrane. • The cell membrane is fluid and selectively permeable, allowing only certain substances in the environment to pass through. Buck Salinas 2012

12. The Cell Membrane as a Barrier • The selective permeability of the membrane is caused by the way phospholipids interact with water. • A phospholipid has a polar “head” and two nonpolar “tails” • Lipid Bilayer: the arrangement of phospholipids in the cell membrane. Nonpolar tails make up the interior of the bilayer because water in and out of the cell repels the nonpolar tails. • Ions and most polar molecules are repelled. Lipids are allowed to pass through. Buck Salinas 2012 Photos: http://www.bioteach.ubc.ca/Bio-industry/Inex/

13. Membrane Proteins • Various proteins are located in the lipid bilayer. • Proteins are made of amino acids. Some amino acids are polar, others are nonpolar. • The nonpolar part of a membrane protein is attracted to the interior of the lipid bilayer but repelled by the water on either side. This holds the protein in place. • Membranes contain different proteins. • Marker Proteins: attached to a carbohydrate advertise cell type. • Receptor Proteins: bind signal molecules outside the cell. • Enzymes: involved in biochemical reactions in the cell. • Transport: aid in the movement of substances into and out of the cell. Buck Salinas 2012

14. 09/20/12 DOL #1 • On your whiteboard, draw a phospholipid. • Label the parts and indicate if each part is polar or non polar. • Finally, draw a small section of the lipid bilayer that demonstrates how the phospholipids are oriented.

15. Cell Structure Ch. 3.3 Buck Salinas 2012

16. The Nucleus • Controls most functions of the cell. • Surrounded by a double membrane known as the nuclear envelope, made of two lipid bilayers. • Nuclear pores, small channels, are scattered over the surface of the nuclear envelope so substances made in the nucleus can move into the cytoplasm. • The hereditary information of a cell is coded in the DNA, which is stored in the nucleus. Buck Salinas 2012

17. Ribosomes and the Endoplasmic Reticulum • Eukaryotic cells have a system of internal membranes that play a role in the processing of proteins. • Cells make proteins on ribosomes. Each ribosomes is made of proteins and RNA. Some ribosomes are found “free” in the cytoplasm (cytosol) while others are on the surface of the endoplasmic reticulum. Buck Salinas 2012

18. Production of Proteins • Proteins that are exported from the cell are made on ribosomes on the surface of the endoplasmic reticulum. • Endoplasmic Reticulum: a system of internal membranes that move proteins and other substances through the cell. Made of a lipid bilayer. • The ER with ribosomes is called rough ER. • The rough ER helps transport the proteins made by the ribosomes. • Each protein crosses the membrane and enters the ER. The portion of the ER with the protein pinches off to form a vesicle. • Vesicle: a small, membrane-bound sac that transports substances in cells. • The rest of the ER with no ribosomes is the smooth ER. • Makes lipids and breaks down toxic substances. Buck Salinas 2012

19. Packaging and Distribution of Proteins • Vesicles that contain newly made proteins move through the cytoplasm from the ER into an organelle called the Golgi Apparatus. Enzymes in the Golgi modify the proteins and enclose them in new vesicles. • Golgi Apparatus: a set of flattened, membrane-bound sacs that serve as the packaging and distribution center of the cell. • Lysosomes: other vesicles which are small, spherical organelles that contain the cell’s digestive enzymes. The ER, Golgi, and Lysosomes work together in protein production, packaging, and distribution. Buck Salinas 2012

20. Mitochondria • Mitochondria: an organelle that harvests energy from organic compounds (biomolecules) such as sugar such as to make ATP. • Cells like muscle cells that use a lot of energy can have thousands of mitochondria. • The outer membrane is smooth, the inner membrane is folded. These membranes are where the chemical reactions take place. • Mitochondrial DNA: independent of nuclear DNA, similar to bacterial DNA Buck Salinas 2012

21. Plant Cells • Plant cells have there additional structures not found in animal cells. • Cell Wall: a thick wall of proteins and carbohydrates including cellulose. Supports and maintains cell shape. • Chloroplasts: Organelles that use light energy to make sugar. Have DNA like mitochondria. • Central Vacuole: a large membrane-bound space that stores water and helps to make the cell rigid so plants can stand upright. Buck Salinas 2012

22. 09/20/12 DOL #2 • On the whiteboards, draw FOUR organelles we learned about today. Next to each organelle, BRIEFLY describe the function (what it does!) of the organelle!

23. Journal Entry • Write down three new things you learned about bacteria. • Are bacteria as bad as you thought? Explain. • At the end of 5 minutes, I want to see at least FIVE written sentences!

24. Bacteria Ch. 20.2 Buck Salinas 2012

25. Bacteria: A Prokaryote Bacteria (Prokaryotes)Differ from Eukaryotes in at least seven ways: • Internal Compartmentalization—bacteria don’t have them, while eukaryotes do. • Cell Size—prokaryotes like bacteria are smaller than eukaryotes. • Multicellularity—prokaryotes like bacteria are never multicellular, eukaryotes can have multiple cells. • Chromosomes—prokaryotes have one circular chromosome, eukaryotes have linear chromosomes. • Reproduction—prokaryotes only reproduce asexually, through binary fission while eukaryotic reproduction varies by species. • Flagella—prokaryotic flagella are less complex than eukaryotic flagella. • Metabolic Diversity—bacteria have many metabolic abilities that eukaryotes do not have. Buck Salinas 2012

26. Bacterial Cell Shapes • Bacterial cells are usually one of three basic shapes. • Bacillus: rod-shaped cells • Coccus: round-shaped cells • Spirillium: sprial-shaped cell • Species that form filaments (strings) are indicated by the prefix strepto- while those that form clusters are indicated by the prefix staphylo. • Members of the kingdom Eubacteria have a cell wall made of peptidoglycan (polysaccharides and amino acid chains). • Outside the cell wall and membrane, many bacteria have a capsule. • Capsule: a gel-like layer, allows bacteria to stick to things Buck Salinas 2012

27. Buck Salinas 2012 Bacterial Cell Shapes • Cell Walls: Eubacteria have two types of cell walls, distinguished by a dye called Gram stain (Gram negative, Gram positive). This is important because it helps determine the type of antibiotics needed to fight the bacteria. • Endospores: Some bacteria form thick-walled endospores around their chromosomes with a bit of cytoplasm when the bacteria are exposed to harsh conditions. This allows the bacteria to remain dormant and survive the environmental stress. • Pili: Allow bacteria to adhere to the surface of sources of nutrition. Also allow bacteria to connect and exchange genetic material. • Conjugation: a process in which two organisms exchange genetic material. In prokaryotes, pili from on bacterium connects to a second and genetic material is exchanged.

28. Obtaining Energy Bacteria can live in many conditions and obtain nutrients and energy in many ways. • Photosynthesizers: use light to make energy. • Carry out much of the photosynthesis in the world, often found in aquatic locations • Chemoautotrophs: obtain energy by removing electrons from inorganic molecules such as ammonia and hydrogen sulfide • Often live in the soil and are important to the environment and agriculture because they complete Nitrification for plants. • Heterotrophs: break down the bodies of dead organisms and make nutrients available to other organisms • Decomposers, break down dead material, can secrete poison into food, fix nitrogen. Buck Salinas 2012

29. Escherichia coli Buck Salinas 2012

30. Pathogenic Bacteria • Your body is full of resources such as minerals, fats, carbs, and vitamins. Bacteria have evolved means of obtaining these resources, and this can make us ill. • Heterotrophic bacteria obtain their nutrients by secreting enzymes that can metabolize their environment. If that environment is your body, it can cause problems! Buck Salinas 2012

31. Bacterial Toxins and Biowarfare • Bacterial Toxins: bacteria can also cause disease by secreting chemical compounds into the environment. • When bacteria grow in food and produce toxins, the toxins can make us sick. • Clostridium botulimun • Escheria coli O157:H7 • Biowarfare: the deliberate exposure of people to biological toxins or pathogens such as bacteria or viruses. Buck Salinas 2012

32. Antibiotics • In 1928, Alexander Fleming noticed a fungus in Penicilliumgenus growing on a bacterial culture. No bacteria grew near the fungus. • Scientists found that this fungus was useful at fighting bacterial infections. • Recently, some bacterial have become resistant to antibiotics. • Antibiotic Misuse: many people do not take the full course of antibiotics—they end their treatment too early allowing resistant bacteria to survive and reproduce. • Multiple-antibiotic Resistance: some bacteria have because resistant to several different antibiotics. Buck Salinas 2012

33. Importance of Bacteria • Probiotics: used to promote bacterial growth in the human digestive tract. Foods such as yogurt contain active cultures of bacteria and provide a source of bacteria for the human digestive tract. • Food and Chemical Production: • Many of the foods that we eat are processed by bacteria. • Pickles, buttermilk, cheese, sauerkraut, olives, vinegar, sourdough bread • Humans are also able to use bacteria for industrial uses including making acetone. • Genetic engineering allows bacteria to produce compounds. • Mining and Environmental Uses of Bacteria: • Mining companies can use bacteria to concentrate elements from ore. • Bacteria metabolize different compounds and are used to clean up oil and chemical spills. Buck Salinas 2012

34. 09/24/12 DOL • On the Venn Diagram side of your dry erase board, compare and contrast prokaryotes and eukaryotes. • At the end of 5 minutes, I want to see AT LEAST 3 points under prokaryotes, eukaryotes, and both! • More is even better!!!

35. Introduction to Microscopes • Today we will be using a light microscope, where light passes through one or more lenses to produce an enlarged image of a specimen.

37. Cells and Their Environments Chapter 4.1: Passive Transport Photo: http://www.chemistryland.com/CHM130S/07-Mole/Mole.htm

38. Passive Transport Movement across the cell membrane that does not require energy! Buck Salinas 2012

39. Diffusion • Your body responds constantly to external conditions to maintain a stable internal environment. • Homeostasis: the maintenance of constant internal conditions in spite of changing external conditions. • Homeostasis can be conducted in many ways including moving substances across the cell membrane with or without energy from the cell. Buck Salinas 2012

40. Random Motion and Concentration • Passive Transport: Movement across the cell membrane that does not require energy. • Concentration Gradient: a difference in the concentration of a substance across a space • Equilibrium: a condition in which the concentration of a substance is equal through Buck Salinas 2012

41. Movement of Substances • Particles of substances of a solution move around randomly. • Concentration gradients cause substances to move from an area of high concentration to an area of low concentration. • Diffusion: the movement of a substances from an area of high concentration to an area of lower concentration caused by the random motion of particles • The cell membrane is selectively permeable to substances; the nonpolar interior of the lipid bilayer repels ions and most polar molecules. • Many substances such as molecules and ions enter or leave the cells by diffusing across the membrane. • Concentrations are different inside the cell than they are outside, so substances move “down” the concentration gradient (high to low!). • Diffusion Video Buck Salinas 2012

42. Osmosis • Osmosis: the diffusion of water through a selectively permeable membrane • Because water molecules are so small, they can diffuse through the membrane even though they are polar. • Osmosis is caused because some water molecules are attracted to ions on one side or the other of the membrane. If the different sides of the cell have different concentrations of dissolved particles, they will have different concentrations of “free” water. Osmosis occurs as free water moves into the solution with the lower concentration of free water. Buck Salinas 2012

43. Hypertonic, Hypotonic, Isotonic • Three directions water can move in a cell: • Water moves out: hypertonic solutions cause a cell to shrink; the solution outside has a higher concentration of dissolved particles than cytosol (cytoplasm). • Water moves in: hypotonic solutions cause a cell to swell; the solution outside has a lower concentration of dissolved particles than cytosol (cytoplasm). Could cause a cell to burst. • No net water movement: isotonic solutions cause no change in cell volumes; the cytosol (cytoplasm) and outside solution have the same concentration of free water molecules. Buck Salinas 2012

44. Crossing the Cell Membrane • Osmosis Video • Most ions and polar molecules cannot pass across the cell membrane because they cannot pass through the nonpolar interior of the lipid bilayer. • However, polar substances can cross using transport proteins. • Transport Proteins: provide polar passageways through which ions and polar molecules can cross the cell membrane Buck Salinas 2012

45. Diffusion Through Ion Channels • Ions (Na+, K+, Ca2+, Cl-) are needed in cells but cannot diffuse across the cell membrane. • Ion Channel: a transport protein with a polar pore through which ions can pass. • The pores of some ions are always open. Other ion channels must be opened or closed based upon external stimuli. Buck Salinas 2012

46. Electrical Charge and Ion Transport • The rate of movement of a substance across the cell membrane is generally determined by the concentration gradient of the substance. • The movement of a charged particle, such as an ion, across the cell membrane is also influenced by the particle’s positive or negative electrical charge. • The direction of movement caused by an ion’s concentration gradient may oppose the direction of movement caused by the ion’s electrical charge, often affecting the diffusion of ions across the cell membrane. Buck Salinas 2012

47. Facilitated Diffusion • Most cells have a transport protein that can bind to a specific substance on one side of the cell membrane, carry the substance across the membrane, and release it on the other side. These are carrier proteins. • When carrier proteins transport substances down the concentration gradient, the transport is facilitated diffusion. • Facilitated Diffusion: a type of passive transport that moves substances down their concentration gradient WITHOUT using the cell’s energy Buck Salinas 2012

48. Cells and Their Environments Chapter 4.2: Active Transport Active Transport The transport of a substance across the cell membrane against its concentration gradient requiring energy from the cell. Buck Salinas 2012

49. Movement Against a Concentration Gradient • Facilitated diffusion can only transport substances down their concentration gradient. • Active Transport: the transport of a substance across the cell membrane against its concentration gradient • Active transport requires the cell to use energy because the substance is being moved against its concentration gradient. • Usually this energy comes from ATP. • Some active-transport processes involve carrier proteins which require energy and act as pumps to move substances against their concentration gradient. Buck Salinas 2012

50. Sodium-Potassium Pump • Extremely important in animal cells. • In a complete cycle, it transports three sodium ions (Na+) and two potassium ions (K+) into the cell because sodium cells are usually more concentrated outside the cell than inside, while potassium are usually more concentrated inside the cell. • The energy for this pump is provided by ATP. • This prevents sodium from accumulating in the cell (what would happen if there were too many). • Helps maintain the concentration gradient because this is used to transport other substances. Buck Salinas 2012