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BIOL 1F25 - Exam Prep

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Brock University
Nicholas D Vesprini

Biology – Metabolism Scientific method: when a question arises about the natural world, the scientific method provides the accepted, logical path to the answer -we develop a hypothesis using reasoning Inductive reasoning: creating a general statement from our observations Deductive reasoning: moving from the general hypothesis to a specific situation -an if, then statement is an ideal situation for a scientific experiment -when designing and running the experiment, we must control all variables otherwise we cannot draw any valid conclusions Variable: a factor that can be changed in an experiment to test whether and how it affects the outcome -our hypothesis must be testable Statistical significance: an experimental result that would occur by chance in less than 1 experiment in 20; the accepted level in modern science -observation, experimentation and analysis are the basis for scientific reasoning Theory: a general uniting principle of science upheld by observation and many experiments; not facts but rather extremely well supported explanations of the natural world that nobody has disproved -organic chemicals are usually made my organisms and always contain carbon; carbon is flexible and can bond covalently with four other atoms leading to an almost infinite set of carbon structures -in organic compounds, carbon often bonds with two carbons and two hydrogens; the resulting hydro- carbon compounds can be chain or ring structures -attached to the carbon/hydrogen core are functional groups that determine the compounds reactivity Functional groups: subunit on an organic molecule that helps determine how it reacts with other chemicals -organic compounds are grouped into four main categories: carbohydrates, lipids, proteins and nucleic acids -carbohydrates are organic molecules that are quite abundant in organisms; composed of carbon, hydrogen and oxygen in a ratio of 1:2:1 -many carbohydrates are saccharides (sugars); glucose and fructose are both simple sugars, they are called mono-saccharides because they have one ring of 6 carbons with 12 hydrogens and 6 oxygens attached -oligosaccharides and polysaccharides are longer sugar chains -disaccharides such as sucrose and lactose are common in the human diet -glycogen is a polysaccharide sugar molecule stored in animal tissue; glycogen is stored in muscles and the liver where it is readily broken down when needed -unlike glycogen, starch is a fairly long, straight chain of sugars; plants store energy in starch, often in roots, tubers and grains -cellulose another polysaccharide has a binding pattern similar to glycogen; often used in structural fibers in plants and is the main component of paper -carbohydrates are the best energy source for the human body Hydrolysis: digestive enzymes insert a water molecule between adjacent monosaccharides in the chain, disrupting the convalent bond between sugars and releasing one sugar molecule Dehydration synthesis: a molecule of water is removed from adjacent glucose molecules, allowing them to bond; by adding water digestive enzymes separate glucose molecules from glycogen and starch; once glucose enters a cell, it can be completely metabolized into carbon dioxide and water, producing energy through the process of cellular respiration Lipids: such as oils, waxes and fats are long chain organic compounds that are not soluble in water; because water does not dissolve lipids, they form a perfect barrier between these aqueous compartments; lipids are composed of carbon, hydrogen and oxygen, but have far fewer oxygens than do carbohydrates; as the proportion of stored lipids in the body rises, people become overweight Fatty acid: a long chain of hydrogens and carbons; a carboxyl (acid) group is attached to the end carbon which gives it the name fatty acid; these chains are hydrophobic; the carboxyl group is the only hydrophilic location -there are two types of fatty acids: saturated fats have no double bonds between carbons in the fat chains; for this reason they are completely saturated with hydrogens and cannot hold anymore; the straight chains of hydrocarbons in a saturated fat allow the individual chains to pack close together; saturated fats such as butter are sold at room temperature -unsaturated fats have at least one double bond between adjacent carbons; this puts a crimp in the straight carbon chain preventing close packing of the molecules; as a result, unsaturated fats are liquid at room temperature; examples of this include vegetable oils Triglycerides: three fatty acids attached to a glycerol backbone; the most abundant fat in the body; the body manufactures triglycerides as nonpolar, uncharged storage molecules; in adipose (fat) tissue, excess calories are stored in droplets of triglycerides Prostaglandins: eicosanoids are essential lipids that serve as raw materials for prostaglandins; short- chain fatty acids that regulate local signaling processes; when nearby cells detect prostaglandins they respond immediately with the sensation of pain; aspirin blocks prostaglandins from reaching their cellular target, whereas ibuprofen competes for the site where prostaglandins bind to cells Cholesterol: integral part of cell membranes that allows for flexibility and growth; high blood cholesterol has been linked to heart disease, so dietary restriction of cholesterol is often suggested; because your body synthesizes cholesterol, it is difficult to manage cholesterol levels solely by diet -sex hormones estrogen and testosterone are two steroids that are responsible for the enormous changes of puberty; anabolic steroids are related to testosterone and stimulate growth of the muscles -millions of different proteins are all formed from just 20 amino acids; an amino acid is composed of a central carbon atom with four groups attached to it: a hydrogen atom, an amino group, a carboxyl group, and a radical group/side chain (R); the R group determines the activity of the amino acid -individual amino acids combine to form proteins, using peptide bonds that form between the amino group of one amino acid and the carboxyl group of the next; the resulting two-amino-acid compound is called a dipeptide; as more amino acids join the growing chain, it becomes a polypeptide; as a rule of thumb, when the amino acid count exceeds 100, the compound is called a protein -the folding and interacting of adjacent amino acids determine the shape of a protein; if they repel one another the protein bends outward, if they attract via weak hydrogen bonds, they bend inward Protein: have four levels of structural complexity: their primary structure is the unique order of amino acids in the chain; nearby amino acids interact with hydrogen to form either alpha helixes or beta pleated sheets, which is the secondary structure; the tertiary structure emerges from interactions between adjacent amino acids of the helical or pleated sheets, creating a complex coiling and folding; this structure is a result of the hydrophobic and hydrophilic portions of the molecule twisting to either associate with water or to hide from it inside the molecule; the quaternary structure emerges from the looping of two or more strands around one another; the final shape of a protein is either globular or fibrous -the shape of a protein molecule determines its function and the final shape is determined by its primary structure; in sickle anemia, a change of one amino acid from the normal hemoglobin protein creates a protein that fails to deliver oxygen correctly; a sickled hemoglobin molecule becomes sharp, deforming the entire red blood cell into the sickle shape; these cells can get lodged in small blood vessels, causing pain and interfering with oxygen flow to the tissues -when a protein unfolds or radically alters its folding pattern in response to environmental changes we call it denatured; this happens when we cook, i.e. as we heat an egg, proteins in the clear white unfold, forming a cloudy mass; this reaction is not reversible, denaturing is often permanent -enzymes serve as catalysts for biochemical reactions; meaning that they facilitate a specific reaction without being altered during it; catalysts bring the reactants together, so a reaction can occur more quickly; the active site of a protein is shaped to bind to one specific substrate; after the substrate binds, the enzyme provides an environment for the specific chemical reaction to occur Nucleic acid: the fourth and final class of organic compounds; these are large molecules composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus; nucleic acids store and process an organism’s hereditary information; the two types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) -DNA exists in the nucleus of our cells, it contains hereditary (genetic) information of the cell; DNA encodes the information needed to build proteins, to regulate physiological processes and to maintain homeostasis; the sugar in DNA is a deoxyribose meaning it lacks an oxygen, whereas RNA contains a simple ribose sugar -DNA has four bases: adenine (A), thymine (T), cytosine (C), and guanine (G); RNA also has these four bases with one change; in RNA, uracil (U) appears instead of thymine -DNA is a double stranded molecule, to fit the two DNA strands of one macromolecule together neatly and precisely, the strands lie antiparallel to one another; meaning that although they lie parallel, they run in opposite direction -RNA is not a storage unit and may occur inside or outside the nucleus; it serves to regulate cellular metabolism, produce proteins, and govern developmental timing; RNA is usually a single stranded molecule, however nucleic acids are more stable when paired; to achieve stability, RNA strands will fold back on themselves, pairing up A:U and C:G, similar to DNA; the shape of the RNA molecule often dictates its function -our energy storage system provides short and long term storage; short term energy storage uses a high-energy system that is reversible and instantly available; the most common storage is adenosine triphosphate or ATP -ATP powers all cellular activity, from forming proteins to contracting muscles; long term storage includes glycogen in muscles and liver, and triglycerides packed into specialized storage cells called adipocytes; ATP is composed of an adenine bonded to a ribose sugar with three phosphates attached; these phosphate bonds carry a lot of energy in their covalent bonds -when ATP is hydrolyzed, the third phosphate bond breaks, releasing inorganic phosphate and the energy that held the ATP molecule together, forming adenosine diphosphate (ADP); this released energy drives cellular activity; the ATP-ADP energy storage system is readily available and renewable; when glucose is broken down, the released energy can be used to recombine the inorganic phosphate to the ADP, generating a new ATP molecule Nutrients: the cells of our body require nutrients in usable form to maintain homeostasis and create ATP; a nutrient is any compound required by the body; the two main types of nutrients are macronutrients (carbohydrates, lipids and proteins) and micronutrients (vitamins and minerals) -from these macronutrients, the body synthesizes cellular components such as the cell membrane, enzymes, organelles, and even entirely new cells during cell division -we require micronutrients for the proper functioning of essential compounds such as the enzymes of cellular respiration -carbohydrates are our best source of energy; when we ingest carbs we are left with energy, water and carbon dioxide; they are composed of carbon, hydrogen and oxygen -lipids or fats are a second class of macronutrients; they are long chains of carbon molecules, but they have many more carbon atoms and far fewer oxygen atoms than do carbohydrates; fats can either be saturated meaning that every space in the carbon chain is occupied with hydrogens or unsaturated meaning that there are one or more double bonds in the carbon chain -in the case of unsatur
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