Week 2: Chapter 2
Week 2: Chapter 2 Biology 1010 (Anderson)
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This 12 page Class Notes was uploaded by Emily Johnson on Wednesday September 21, 2016. The Class Notes belongs to Biology 1010 (Anderson) at Austin Peay State University taught by Kelly Anderson in Fall 2016. Since its upload, it has received 4 views. For similar materials see Principles of Life 1 in Biology at Austin Peay State University.
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Date Created: 09/21/16
Biology 1010 Week of 8/299/2 8/29: Chapter 2 cont. Water and Life: ● Life began evolving in water and evolved for about 3 billion years before spreading to land. ○ Land dwellers still rely on water. ○ Our cells are composed of 7095% water. ● Droughts can be detrimental to ecosystems, forcing organisms to adapt. ○ Crop damage, dust storms, and famine can be a result. ● One example of organisms adapting to their environment is cacti in deserts. Water’s LifeSupporting Properties: ● Water has 4 lifesupporting properties that make it essential for the survival of humans. ○ Water has a cohesive nature. ○ Water has a strong resistance to temperature change. ○ Frozen water floats. ○ Water is a common solvent. Cohesion: ● Water molecules stick together as a result of hydrogen bonding. ● Cohesion is the tendency of like molecules to stick together. ● Cohesion is what allows water to evaporate against gravity and enables photosynthesis in trees and other plants. ● Surface tension is another quality of cohesion. Water’s surface tension is much higher than other liquids, and is what allows for bugs to skim across its surface. Temperature: ● Water’s ability to resist temperature change is a result of hydrogen bonding. ● Heat and temperature are related, but different ○ Heat is the amount of energy associated with the movement of atoms and molecules. ○ Temperature is a measure of the intensity of heat. ● Water can absorb and store a lot of heat, while only changing a few degrees in temperature. ● When water is heated, energy disrupts hydrogen bonds; when it cools, the hydrogen bonds reform. ● Water’s ability to resist temperature changes impacts the temperatures of coastal communities. Coastal communities tend to be cooler as a result. ● Water stores heat during warming periods and releases heat during cooling periods. ● One example of this is evaporative cooling. Humans experience this as sweating. Frozen Water Floats: ● When most liquids get cold, their molecules move together and freeze; when water gets cold, its molecules move apart, forming ice. ● A chunk of ice has fewer water molecules than an equal volume of liquid water. ● Ice floats because it is less dense than liquid water. Ice floats because of hydrogen bonding: ○ In liquid water, hydrogen bonds constantly break and reform ○ In ice, stable hydrogen bonds hold molecules apart, making it less dense. ● Floating ice insulates the water beneath it, making it possible for aquatic life to exist. Water as a Solvent: ● A s olution is a mixture of 2 or more substances. ● A solvent is the dissolving agent. ● A solute is what is being dissolved. ● One example is sweet tea. Sugar is dissolved into the tea, so sugar is the sol e. ● When water is the solvent, the result is an aqueous solution. ○ Fluids in our bodies ○ Tree sap ● Water can dissolve a variety of solutes necessary for life. Acids, Bases, and pH ● A chemical compound that releases hydrogen ions is an acid. ● A compound that accepts hydrogen ions and removes them from a solution is a ase. ● Scientists use the pH scale to measure acidity and basicity. ● 0 = most acidic, 14 = most basic. ● pH of 06.9 is an acid. ● pH of 7 is neutral. ● pH of 7.114 is a base. ● Each pH unit represents a tenfold change in concentration. So, there is a 10x difference in concentration between a pH of 1 and a pH of 2. Between pH 1 and pH 3 there is a 100x difference in concentration. ● Buffers resist pH change. ○ They accept hydrogen when it’s in excess. ○ They donate hydrogen when it’s depleted. ● 25% of carbon dioxide output is absorbed by oceans and turned into carbonic acid. 8/31: Ch. 3 Molecules of Life: Organic Compounds Organic Compounds: ● A cell is mostly water. The rest is composed of carbonbased molecules. ● Carbon forms large, complex molecules necessary for life’s function. ● Organic compounds are carbonbased molecules. Carbon: ● Carbon can share 4 electrons in covalent bonds. ● It can use its bonds to: ○ Attach to other carbons ○ Form endless carbon skeletons Carbon Chemistry: ● The simplest organic compounds are hydrocarbons. ○ The simplest hydrocarbon is methane. ● Larger hydrocarbons form fuel for engines. ● Each type of organic molecule has a unique structure that impacts its function. Its unique properties depend on: ○ Its carbon skeleton ○ The atoms that are attached ● Groups of atoms that participate in reactions are functional groups. Macromolecules: ● There are 3 categories of macromolecules: ○ Carbohydrates (Sugars and Starches) ○ Proteins (Amino Acids) ○ Nucleic Acids (DNA and RNA) ● Polymers = Macromolecules ● Polymers are made by stringing monomers together. ● A d ehydration reaction ○ Links 2 monomers ○ Removes a molecule of water ● Organisms have to break down macromolecules. Animals break them down through digestion. ● Hydrolysis is the breakdown of polymers by adding a molecule of water and reversing a dehydration reaction. Biological Molecules: ● There are 4 biological molecules: ○ Carbohydrates ○ Lipids ○ Proteins ○ Nucleic acids Carbohydrates: ● Carbohydrates consist of sugars and polymers of sugar. ○ Small sugars, like in soda ○ Longer sugars, like in potatoes (starch) ● Carbohydrates are a source of energy and allow for compounds to be formed. ● In plants, they serve as a building material. Monosaccharides: ● The simplest carbohydrate is a monosaccharide (mono=one, sacchar=sugar). ● Simple sugars cannot be broken down by hydrolysis. They are in their simplest form. ● 2 examples of monosaccharides are glucose and fructose. Fructose is the sweeter of the 2. Honey contains both glucose and fructose. ● Glucose and fructose are isomers, molecules with the same molecular formula but a different structure. ● Minor differences in atom arrangements give isomers very different properties. ● Monosaccharides (mainly glucose) are the main fuels for cellular work. ● In water, monosaccharides form a ring. ● Your cells rapidly break down glucose and extract the stored energy. CO2 is given off as “exhaust”. Disaccharides: ● A disaccharide is 2 monosaccharides formed by a dehydration reaction. ● Common disaccharides include: ○ Lactose (found in milk) ○ Maltose (found in beer) ○ Sucrose (table sugar) ● Sucrose: ○ Most common disaccharide ○ Rarely used as a sweetener in the US ● Most processed foods in the US used highfructose corn syrup. Highfructose corn syrup is formed by a process that converts natural glucose to a sweeter fructose. ● The US is one of the world’s leading markets for sweeteners. ● The average American consumes about 100lb or 45k of sugar a year. ○ Mainly sucrose and highfructose corn syrup. ● Overconsumption can lead to diabetes and heart disease. Polysaccharides: ● Polysaccharides are complex carbohydrates. ● They are composed of long chains of sugar. (Poly = many). ● Starch: ○ Familiar example of a polysaccharide. ○ Used by plant cells to store energy. ○ Consists of long strings of glucose monomers. ● Potatoes and grains are a major source of starch in our diet. ● Animals use digestive enzymes to break down bonds between glucose monomers through hydrolysis. Glycogen: ● Animals store excess glucose in the form of glycogen. ● Glycogen is stored in the liver and muscle cells. ● Glycogen is converted to glucose when it is needed. ● Athletes eat a lot of carbs in order to produce glycogen. Cellulose: ● Most abundant organic compound on earth. It is a polysaccharide. ● Cellulose forms cable like fibrils in the cell walls of plant cells. ● Most animals can’t break down cellulose. Animals that are able to break it down have microorganisms in their digestive tract to help. ● Fiber is not direct nutrition, but it is beneficial to your body and helps maintain a healthy digestive system. ● Monosaccharides and disaccharides dissolve easily in water. Almost all carbohydrates are hydrophilic, or waterloving. Lipids: ● Lipids are neither macromolecules or polymers. ● Lipids are hydrophobic, meaning they are unable to mix with water. ● A typical triglyceride is composed of: ○ A glycerol molecule ○ 3 fatty acids ○ Formed in a dehydration reaction Fats: ● Fats perform essential functions: ○ Energy storage ○ Insulation ○ Cushioning ● If the carbon skeleton of a fatty acid has fewer hydrogen atoms that the maximum, it is unsaturated. ● If a carbon skeleton has the maximum number of hydrogen atoms, it is saturated. ● Most animal fat has a high proportion of saturated fats and is solid at room temperature. It can be unhealthy in excess because it builds up inside blood vessels. ● Most plant and fish oils are high in unsaturated fats and liquid at room temperature (the exception is coconut oil). ● Hydrogenation adds hydrogen to fatty acid chains and converts unsaturated fats to saturated fats. This creates trans fats. 9/2: Ch. 3 Continued: Steroids: ● Steroids are lipids, but they are very different in structure and function. ● All steroids have a carbon skeleton with 4 fused rings. ● Cholesterol: ○ Common steroid ○ Associated with cardiovascular disease ○ Is a key component of cell membranes ○ Serves as a “base steroid” for estrogen and other steroids ● Synthetic anabolic steroids: ○ Variants of testosterone ○ Mimics the effects ○ Can reduce the output of hormones ○ Can be used to treat injuries, but is abused by athletes to enhance performance. ○ Side effects include low sex drive, infertility, and liver damage. Proteins: ● Proteins are constructed from amino acid monomers. ● Proteins account for 50% of weight of dry cells (when water is taken out). ● Proteins allow for the body to conduct most of the activities performed in everyday life. ● Proteins form enzymes: chemicals that catalyze a chemical reaction. ● Proteins’ shapes allow them to function. A recurring theme of this chapter is the correlation between function and structure. ● Major types of proteins: ● Proteins are made up of a combination of a set of 20 amino acids. ● Each amino acid consists of a central carbon atom bonded to 4 covalent partners. ● 3 attachment groups: ○ A carboxyl group ○ An amino group ○ A hydrogen atom. ● Amino acids link together through dehydration reactions. This will be a common theme this chapter. ● The bond formed is called a peptide bond. ● Long chains of peptide bonds are called polypeptides. ● A functional protein consists of 1 or more polypeptide chains twisted into a unique shape. Proteins as Polymers: ● Your body contains tens of thousands of proteins. ● Proteins differ in their arrangement of amino acids. Think of the 20 amino acids like an alphabet. ● The sequence of amino acids in a protein is its primary structure. ● A very slight change in primary structure can have big effects. The substitution of 1 amino acid in hemoglobin can result in sickle cell disease. ● Proteins with 1 polypeptide has 3 levels of structure. Proteins with more than 1 have 4 levels of structure. ● A protein’s three dimensional structure recognizes its corresponding molecule and enables it to carry out its specific function (like a puzzle piece). ● A protein is sensitive to its environment: ○ Temperature changes can denature the structure of a protein and make it unable to do its specific task ○ A change in pH can do the same, but b uffers help. ○ High temperatures (104+) can lead to denatured proteins. ● Denatured proteins are the cause of: ○ Alzheimer’s ○ Parkinson’s ○ Mad cow disease ● Prions are misfolded brain proteins. Prions are only caused by exposure to prions of an animal (via meat, etc.) ● Prions can infiltrate the brain and cause other proteins to misfold, like a chain reaction. ● Prions are linked to Alzheimer’s. Nucleic Acids: ● Nucleic acids are macromolecules that store information and provide direction for proteins. ● Nucleic acids form DNA and RNA. ● DNA resides in cells in chromosomes, contained in the nucleus of eukaryotic cells. ● A gene is a unit of inheritance. It is a specific stretch of DNA that programs for a specific amino acid segment to be built. ● The chemical code of DNA is translated from nucleic acid language to protein language via RNA. ● Gene segments allow for RNA to form. ● Nucleic acids are polymers made from nucleotide monomers. ● Each nucleotide has 3 parts: ○ 5carbon sugar (either deoxyribose or ribose) ○ Phosphate group ○ Nitrogenous base ■ Adenine ■ Thymine ■ Cytosine ■ Guanine ● Nitrogenous bases: ○ Adenine bonds with thymine ○ Cytosine bonds with guanine ○ Thymine and cytosine are single ringed ○ Adenine and guanine are double ringed. ● Adenine and thymine bond with a hydrogen bond. This allows the DNA to unzip and form RNA. ● RNA acts as a messenger, going from DNA and traveling to proteins to deliver instructions. ● Dehydration reactions: ○ Link nucleotides into polynucleotides ○ Form covalent bonds between the sugar of 1 nucleotide and the phosphate of another. ○ Creates the backbone for DNA. RNA and DNA: ● 3 main differences: ○ RNA uses the sugar ribose while DNA uses deoxyribose. ○ RNA is usually single stranded, DNA is a double helix. ○ RNA uses the nitrogenous base uracil instead of thymine.
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