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  • 1. Biology 11 IB Earland Topic 2 – Cells 2.1 Cell Theory 2.1.1 Outline the cell theory 2.1.6 Explain the importance of the surface area to volume ratio as a function of 2.1.2 Discuss the evidence for the cell theory limiting cell size 2.1.3 State that unicellular organisms carry out all the functions of life 2.1.7 State that multicellular organisms show emergent properties 2.1.4 Compare relative sizes of molecules, cell membrane thickness, viruses, 2.1.8 Explain that cells in unicellular organisms differentiate to carry out bacteria, organelles, and cells, using the appropriate SI units specialized functions by expressing some of their genes but not mothers 2.1.5 Calculate the linear magnification of drawings and the actual size of 2.1.9 State that stem cells retain the capacity to divide and have the ability to specimens in images of know magnification differentiate along different pathways 2.1.10 Outline one therapeutic use of stem cells Text Book Pages 1-14 Workbook Pages 57-65 The Cell Theory is Summarized into five points listed below: 1. All living things are composed of cells 2. Cells are the smallest unit of life 3. New cells are formed only by the division of pre-existing cells 4. The cell contains inherited information (genes) that provide instructions for growth and development 5. The cell is the site of all the chemical reactions of life (metabolism) *** 4 & 5 were not part of the original cell theory! Evidence that Supports the Cell Theory: Fill in the table below using Table 1.2 p. 4 in your text (in your own words please) Theory Statement Evidence Living things are made up of cells Cells are the smallest units of life Cells come from pre-existing cells Cells contain a blueprint for growth, development, and behavior Cells are the site of the chemical reactions of life So How Big are these Cell Things? Reference Fig 1.18 in your text & P. in your workbook Below is a table of the microscope sizes that you should be familiar with: Unit Abbr. Metric Conversion Conversion factor Kilometer km 1000m 103 m m 1m Centimeter cm 102 m mm 0.001m micrometer um 0.000 001m nm 10-9 m 1
  • 2. Biology 11 IB Earland Feature Actual Size Relative Size Comparison Molecule 1 nm 1 dime Membrane thickness 10nm 10x larger 3 text books stacked Virus 100 nm 100x Grade 8 student Bacteria 1um 1000x A large classroom Organelle 10 um 10,000 x school Animal cell 100 um 100,000x campus *Molecules are too small to be seen with any time of microscope! Recall SI Units and Unit Conversions: 5mm = ? nm 4.4cm = ?nm 6.8mm=? um 3.5cm = ? cm 7.1 um = ? cm 1520nm = ?mm Surface Area to Volume Ratio Read P. 5 of your text book & Complete p. ` in your Workbook Write a paragraph in the space below explaining the importance of the surface area to volume ration as a factor limiting cell size. There are two hints below to help you.  The rate of heat production/waste production/resource consumption of a cell is a function of its volume  The rate of exchange of materials and energy (heat) of a cell is a function of its surface area Drawing Specimens: Complete p. in your workbook Finding Total Magnification and the Diameter of the Field of View Total Magnification = (power of the eye piece) x (Power of the objective lens) Field of View = diameter of circle you can see for each magnification Using a ruler, you find the field of view for low power (4.5 mm)Then, from this measurement, the FOV for the other powers is calculated using the formula: FOVx = FOV low x Maglow Ex: FOVmed = 4.5mm x (40/100) = 1.8 mm Magx Power Total Magnification Diameter of FOV in mm Diameter in um High 400x 0.45 mm 450 um Medium 100x 1.8 mm 1800 um Low 40x 4.5 mm 4500 um Actual Size of Specimen: estimate how many could fit end to end across the diameter of the field of view, then use the following formula Size of Specimen = diameter of FOV # of objects the fit across Drawing Magnification: this is used to determine how many times bigger your drawing is than the actual size Drawing Magnification = drawing size Actual size 2
  • 3. Biology 11 IB Earland Scale Bars: Images often carry a scale bar which is a line on the image that shows how long the line is in the real specimen. The easiest way to add a scale bar is to find the actual size of the specimen and then draw a line beside the specimen indicating the measurement Functions of Life: All organisms exists in either a unicellular or multicellular form and must be able to carry out the following functions:  Metabolism  Reproduction  Homeostasis  Growth  Response  Nutrition Cells There are two fundamentally different types of cells: prokaryotes (before a nucleus) - includes bacteria and cyanobacteria (photosynthetic bacteria) eukaryotes (true nucleus) – where DNA is organized into chromosomes, involving proteins includes both plant and animal cells Cell Reproduction & Differentiation: Unicellular organisms are structurally simple in that they perform all the functions and activities of life within a single cell Multicellular organisms in contrast, are made up of many cells and therefore most of their cells are highly specialized to do specific functions. Emergent Properties of multicellular organisms: the properties in total of a multicellular organism are greater than the sum of the individual parts Cell Specialization in Multicellular organisms: The nucleus of each cell contains DNA in Chromosomes. Chromosomes are linear sequences of Genes, and genes control the development of each cell. Gene:  A specific region of a chromosome which is capable of determining the development of a specific characteristic of an organism  A piece of the DNA which codes for a protein Differentiating: is when a cell becomes specialized because only some of its genes are being activated and expressed. (all cells contain all the DNA, but each individual cell only uses parts of its DNA depending on its specialization).  Once a cell has differentiated and become specialized, it can not change its specialization and can only reproduce cells of the same specialty Stem Cells: Cells that have not differentiated. Ie. They maintain the ability to divide and differentiate into any cell type. Research: o growing embryonic stem cells so they can be used to replace lost cells due to injury o repair lost brain cells due to Alzheimer’s and Parkinson’s o Diabetes cure Controversy: stem cells come from embryos often from IVF laboratories resulting in the death of the embryo. Read p.18 & Understand Fig 1.16 3
  • 4. Biology 11 IB Earland 2.2 Prokaryotic Cells 2.2.1 Draw and label a diagram of the ultra-structure of Escherichia coli as an example of prokaryote 2.2.2 Annotate the diagram with the functions of each named structure 2.2.3 Identify structures from 2.2.1 in electron micrographs of E.coli 2.2.4 State that prokaryotic cells divide by binary fission What is a Prokaryotic Cell?  First cells on earth  Common ancestor of all other cells  Smaller than Eukaryotic cells (<1um)  Lack membrane bound organelles  DNA is not enclosed in a membrane  Cell wall made of peptidoglycan  Cells divide by Binary Fission (asexual)  Ex. bacteria  Basic Features: o Cell wall o Flagella o Pilli o Plasma o Ribosomes o Cytoplasm membrane o Nucleoid Draw and Annotate Fig 1.15 p. 16 Below of Escherichia coli What is a disadvantage of prokaryotic cells having DNA free in the cytoplasm without a nuclear membrane? What is a disadvantage of prokaryotic cells lacking membrane bound organelles? 2.3 Eukaryotic Cells 2.3.1 Draw & Label a diagram of the ultra structure of a liver cells as an example of an animal cell 2.3.2 Annotate the diagram with the functions of each named structure 2.3.3 Identify structures from 2.3.1 in electron micrographs of liver cells 2.3.4 Compare prokaryotic & eukaryotic cells 2.3.5 State three differences between plant and animal cells 2.3.6 Outline two roles of extra cellular components Read Extension p. 17 Watch “Cell Biology” -Write a paragraph to summarize what you learned in the video regarding how it is believed that Eukaryotic cells organelles were once prokaryotes and the evidence that supports this theory. -Make a time-line outlining the events that the video addressed Eukaryotic Cells: Using p. 15 & 16 of your text. Annotate a drawing of both a plant and an animal cell: 4
  • 5. Biology 11 IB Earland Note: The Nucleus, Endoplasmic Reticulum, Ribosomes, Golgi Apparatus work together in Protein Synthesis Note: The Chloroplast and Mitochondria work together in Energy production PLASMA (CELL) MEMBRANE the thin, outer membrane that separates the cell's interior from its external environment. The plasma membrane also separates each cell from its neighboring cells, so that each cell is an individual entity. It is very thin (about a billionth of a meter) and requires an electron microscope to see it. Sometimes, the plasma membrane forms fingerlike projections called MICROVILLI. These microvilli increase the surface area of the plasma membrane. Some body cells have projections on the cell surface that are involved in cellular movement. CILIA are hairlike cellular projections that occur in large numbers on the surface of certain cells. The cilia move in unison, creating a current that propels substances in one direction across the cell surface. FLAGELLA are long in proportion to the size of the cell and are used in moving the entire cell. CYTOSOL The term CYTOPLASM refers to all of the cellular contents located between the plasma membrane and the nucleus. The semifluid portion of the cytoplasm is the CYTOSOL. The organelles are suspended in the cytosol. So, the cytoplasm includes the cytosol and all the organelles (except the nucleus). The CYTOSOL is a thick, elastic, semitransparent fluid which contains mostly water (75-90%). It also contains proteins, lipids, carbohydrates, salts, and other solutes. Many chemical reactions take place in the cytosol. CYTOSKELETON Suspended in the cytosol are very small tubules and filaments that make up the cytoskeleton which provides support and shape to the cell, and is involved in cellular movement (ex of cilia & flagella). It is the bone and muscle of the cell. CELL INCLUSIONS Suspended in the cytosol of some cells are what are called CELL INCLUSIONS. Cell inclusions are chemical substances that are produced by specific cells and stored in their cytosol. GLYCOGEN which is a starch-like complex carbohydrate that is stored in liver cells. When the body needs some quick energy, the liver cells can break down the glycogen into glucose and then use it for energy. FATS are cell inclusions found in fat cells. Fat can also be broken down to produce energy. The pigment MELANIN is a cell inclusion stored in certain cells of the skin, hair and eyes. NUCLEUS is the control center of the cell. It is surrounded by a double-layered membrane called the nuclear envelope. The nucleus contains DNA, the hereditary genetic material of the cell. DNA controls the structure and activities of a cell by providing the instructions for protein synthesis. Proteins act as hormones, enzymes, pigments, and structural components of organelles. A dark staining body, the NUCLEOLUS (or up to four nucleoli) inside the nucleus is the site of ribosome synthesis. RIBOSOMES receive genetic instructions from the nucleus to produce specific proteins. So, ribosomes are the sites of protein synthesis. Some of the ribosomes float free in the cytosol; free ribosomes synthesize proteins that are to be used inside the cell. Other ribosomes are attached to the outer membranes of the ENDOPLASMIC RETICULUM (ER). The ribosomes embedded on the ER are involved in the synthesis of proteins that are to be exported or SECRETED outside the cell. *All organelles, with the exception of the ribosomes, are surrounded by a phospholipid bilayer membrane, similar to the plasma membrane. ENDOPLASMIC RETICULUM is an extensive system of interconnected membrane tubes or channels that coils and twists through the cytosol. The endoplasmic reticulum membrane is continuous with the nuclear envelope of the nucleus and the plasma membrane. Endoplasmic reticulum consists of parallel membranes that enclose narrow channels. There are 2 types of endoplasmic reticulum (ER): smooth ER and rough ER. The SMOOTH ER is smooth because it does not have ribosomes on its surface. ROUGH ER has ribosomes embedded on its surface. SMOOTH ER is involved in the production of LIPIDS (fat-like substances). For example, smooth ER produces CHOLESTEROL, which is part of the plasma membrane. Smooth ER produces STEROID HORMONES such as the sex hormones (estrogen, progesterone, testosterone), which are secreted from the cell. The smooth ER is also involved in the DETOXIFICATION of substances: Liver cells have a lot of smooth ER, because smooth ER detoxifies drugs and alcohol. ROUGH ER has ribosomes attached to the external surface giving it a granular appearance. As proteins are assembled on the ribosomes, the proteins make their way into the rough ER channels (cisterns). The rough ER packages these proteins into round membranous sacs called VESICLES. These vesicles pinch off from the rough ER and make their way to the GOLGI APPARATUS. 5
  • 6. Biology 11 IB Earland GOLGI APPARATUS looks like 4-8 flattened membrane sacs stacked like dishes. Tiny membranous sacs or VESICLES are located nearby. The vesicles that bud off from the rough ER migrate to the Golgi apparatus and fuse with the Golgi apparatus membranes. Inside the Golgi apparatus, the proteins that were made by the ribosomes of the rough ER are modified in some way. These modified proteins are then packaged in vesicles and sent to their destination. Some of these vesicles contain proteins that are to be SECRETED or released from the cell. These SECRETORY VESICLES migrate to the plasma membrane and discharge their contents from the cell. Other vesicles produced by the Golgi apparatus are called LYSOSOMES. LYSOSOMES are membrane-enclosed spheres that contain powerful digestive enzymes capable of digesting substances that are inside the cell (intracellular digestion): - white blood cells, which ingest bacteria, contain large numbers of lysosomes. The digestive enzymes in the lysosome are used to digest and destroy the ingested bacteria - Lysosomes can also engulf old, worn-out organelles and break them down with digestive enzymes. The digested components of the organelles are then returned to the cytosol for recycling into new organelles MITOCHONDRIA are small, kidney bean-shaped organelles. Each mitochondrion has a smooth outer membrane, but the inner membrane is made up of a series of folds. Mitochondria are called the "powerhouses of the cell", because they produce ATP (adenosine triphosphate). ATP is a molecule that stores a great deal of energy. When the cell breaks down ATP, it releases energy that the cell can use. ATP is like the gasoline that powers your car or the electricity that powers your lights. Active cells, such as muscle cells and sperm cells, have large numbers of mitochondria because they use a great deal of energy. During the 1980s, Lynn Margulis proposed the theory of endosymbiosis to explain the origin of mitochondria and chloroplasts from permanent resident prokaryotes. According to this idea, a larger prokaryote (or perhaps early eukaryote) engulfed or surrounded a smaller prokaryote some 1.5 billion to 700 million years ago. Instead of digesting the smaller organisms the large one and the smaller one entered into a type of symbiosis known as mutualism, wherein both organisms benefit and neither is harmed. The larger organism gained excess ATP provided by the "protomitochondrion" and excess sugar provided by the "protochloroplast", while providing a stable environment and the raw materials the endosymbionts required. This is so strong that now eukaryotic cells cannot survive without mitochondria (likewise photosynthetic eukaryotes cannot survive without chloroplasts), and the endosymbionts can not survive outside their hosts. Nearly all eukaryotes have mitochondria. Mitochondrial division is remarkably similar to the prokaryotic methods that will be studied later in this course. PLASTIDS Plastids are also membrane-bound organelles that only occur in plants and photosynthetic eukaryotes, and include chloroplasts (site of photosynthesis), leukoplasts (storage of starch, proteins and oils) and chromoplasts (storage of pigments associated with the bright colours of flowers and/or fruits). Chloroplasts are the sites of photosynthesis in eukaryotes. They contain chlorophyll, the green pigment necessary for photosynthesis to occur, and associated accessory pigments (carotenes and xanthophylls) in photosystems embedded in membranous sacs, thylakoids (collectively a stack of thylakoids are a granum [plural = grana]) floating in a fluid termed the stroma. Chloroplasts contain many different types of accessory pigments, depending on the taxonomic group of the organism being observed. Like mitochondria, chloroplasts have their own DNA, termed cpDNA. Chloroplasts are thought to have originated by endosymbiosis of a prokaryotic alga. VACUOLES & VESICLES Areas of storage for a cell. Vacuoles in plants may occupy salts, ions, and other substances in addition to water. The vacuole helps keep the cell wall stiff and the plant body crisp. Vesicles is used to describe a cellular product packaged for secretion. CENTRIOLES Found in animal cells only, as a pair (in a region called the centrosome). They are composed of sets of microtubules (stringy protein molecules that also appear near the cell membrane). They form the spindle fibres during cell division. Summary of Eukaryotic Organelles and Areas Name Main Function Cell Type Cytoplasm Contains the Organelles Plant & Animal Endoplasmic Reticulum Transportation Plant & Animal Rough ER Protein transport & processing Plant & Animal Smooth ER Lipid synthesis & transport Plant & Animal Ribosomes Protein synthesis Plant & Animal Lysosomes Intracellular digestion Animal & some plant 6
  • 7. Biology 11 IB Earland Golgi Apparatus Storage, packaging & transport Plant & Animal Mitochondria Cellular Respiration- ATP formation Plant & Animal Nucleus Control center housing chromosomes Plant & Animal Chloroplasts Photosynthesis- Glucose production Plant Centrosome Aids in cell division No centrioles in plant Vacuole Storage - water Plant Lg & animal sm Comparison of Prokaryotic & Eukaryotic Cells Prokaryotic Cells Eukaryotic Cells DNA in a ring without protein DNA with proteins as chromosomes/chromatin DNA free in cytoplasm Nucleoid region DNA in nucleus with a nuclear membrane No membrane bound organelles Membrane bound organelles Less than 10um More than 10um Cell wall made of peptidoglycan Cell wall in plants & Fungi, made of cellulose Small 70S ribosome’s Larger 80S ribosome’s Comparison of Plant & Animal Cells Plant Cell Animal Cell Cell wall with cell membrane inside Plasma membrane with no cell wall Chloroplasts No chloroplasts Large central vacuoles No or very small vacuoles Store carbohydrates as starch Store carbohydrates as glycogen Do not contain centrioles within the Centrosome area Do contain centrioles within the Centrosome area Cell wall gives a rigid cell shape that is often angular Lack of cell wall results in cell flexibility and rounding Extracellular Components of Cells: The extracellular matrix (ECM) of many cells is made up of collagen fibers & glycoproteins (sugars & proteins) that form fiber like structures and anchor to the membrane.  Allow attachment between adjacent cells The plant cell wall maintains cell  Allow for cell-to-cell interactions shape, prevents excessive water o Gene expression & coordinated cell action uptake, and holds the whole plant o Directing differentiation up against the force of gravity.  Cell migration & movement Animal cells secrete glycoproteins that form the extracellular matrix. Answer the following questions: This functions in support, adhesion 1. Why do muscle cells have large numbers of mitochondria? and movement. 2. Name two organelles that are similar to prokaryotic cells. 3. If plants have chloroplasts for photosynthesis, then why do they also need mitochondria 4. Are all Eukaryotic cells part of multicellular organisms? Explain 7
  • 8. Biology 11 IB Earland 2.4 MEMBRANES 2.4.1 Draw and label a diagram to show the structure of a membrane 2.4.2 Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes 2.4.3 List the functions of membrane proteins 2.4.4 Define diffusion and osmosis 2.4.5 Explain passive transport across membranes by simple diffusion and facilitated diffusion 2.4.6 explain the role of protein pumps and ATP in active transport across membranes 2.4.7 explain how vesicles are used to transport materials within a cell between the rough E.R., G.A., and plasma membrane 2.4.8 Describe how the fluidity of the membrane allows it to change shape, break and re-form during endocytosis and exocytosis Membrane Structure: p.21-30 See Fig 2.13 p. 50 Polar Hydrophilic Region (water loving) Non-Polar Hydrophobic Region (water hating) See Cross-Sectional View of the Phospholipids bilayer Fig 1.19 p. 21. What is the functional implication of having a double layer of phospholipids? GO TO YOUR WORKBOOK P. 101 AND USE FIG. 1.17 P. 21 TO ANNOTATE THE DIAGRAM BELOW A: glycoprotein (carbohydrate attached) to extrinsic protein B: carbohydrate (attached to lipid – glycolipid) C: intrinsic protein D: carbohydrate (glycolipid) E: cholesterol F: phospholipid inside cells - cytoskeleton Proteins: - embedded into Fluid Matrix - Integral Proteins: - Peripheral Proteins: Basic Structure: =Proteins Their 6 general functions are:  Hormone binding sites  Cell-to-cell communication  Enzymatic action  Channels for passive transport  Cell adhesion  Pumps for active transport 8
  • 9. Biology 11 IB Earland Carbohydrate (sugar) attached to proteins act as distinctive antigens by which cells can recognize each other - glycoprotein -when attached to a protein, the complex is called a glycoprotein - glycolipids -also exist in the cell membrane, a carbohydrate portion attached to a lipid molecule Cholesterol is also present in the plasma membrane. Cholesterol is a LIPID (fat-like molecule) that gives rigidity and strength to the plasma membrane, and is found in the hydrophobic area Transport Across the Membrane: (IB learning Outcomes 2.4.4 2.4.8 p. 22-30) - The structure of the cell surface membrane, the nuclear membrane and the membranes of the organelles allow them to be selectively permeable, and provide for a variety of transport mechanisms. - Control of the exchange across membranes depends on the physical and chemical properties of the membrane and the molecules moving through them. Passive Transport VS Active Transport Transport Types 1. Diffusion (passive transport – no energy required) - the movement of molecules from an area of high concentration to low (down a concentration gradient - caused by random movement of molecules (Brownian motion) – dependent on temperature, size of the molecules, and size of the gradient - in cells, diffusion is limited to small molecules and ions that freely move across the membrane: water, oxygen and carbon dioxide, lipid soluble molecules - Recall: the rate of diffusion is instrumental in determining cell size 2. Osmosis (passive transport) - the movement of water from an area of high concentration of water (low concentration of solute) to low concentration of water (high concentration of solute) through a SELECTIVELY permeable membrane - described in terms of tonicity of the solution with respect to the cell - hypertonic solution: has a higher concentration of solute - hypotonic solution: has a lower concentration of solute - isotonic solution: has the same concentration of solute 9
  • 10. Biology 11 IB Earland 3. Facilitated Diffusion - involves the use of transport proteins that are specific to certain solutes – with specific binding sites - it is believed that the protein changes shape to allow the transport of a solute down a concentration gradient 4. Active Transport (active – requires an energy input from the cell) - involves the use of transport proteins, but takes place against a concentration gradient - ex: the Na+/K+ pump 5. Endocytosis (active) - used to transport larger molecules across the membrane and INTO the cell - there are two types of endocytosis (both consume cell membrane) - pinocytosis – the cell gulps in extracellular fluid into small vesicles - phagocytosis – the cell extends pseudopodia and wraps the particles into a vacuole, which will later fuse with a lysosome for digestion 6. Exocytosis (active) - used to transport large molecules out of the cell – usually vesicles budded from the ER or GA - a vesicle will move towards and fuse with the cell membrane, spilling its contents into the extracellular fluid - exocytosis and endocytosis generally balance each other resulting in no change in the size of the cell 10