Go over homework, discuss labs
Modern Biology p. 3C, 43
Cabbage indicator
Today
Water
As we discussed last time, waster is a polar compound. What kind of bond does water have? (polar covalent) Which atom is postively charged? Which is negatively charged? This means that the electrons are not shared equally between the oxygen and hydrogen atoms. (Draw water on the board). Water has several properties that make it essential to life. One is the previously mentioned polarity. Water's polarity makes it an excellent solvent. Water is sometimes referred to at the "universal solvent" becuause of its ability to solubilize a wide variety of compounds. A second property of water is that of the attraction between water and solid surfaces known as adhesion. This adhesion allows water to actually defy gravity on a small scale. Water can actually travel upward through a narrow tube against the force of gravity. As mentioned last class, water's ability to form hydrogen bonds is also important. One effect of hydrogen bonding in water means that water cools down and heats up slowly. When water is heated up, the energy must first overcome the hydrogen bonds before the temperature of the water can increase. Conversly heat is release when water cools and hydrogen bonds are formed. In organism, this means that cells can maintain even temperatures even in the face of changing environmental conditions. Coastal areas, ocean temperature.
Macromolecules
Macromolecule literally means large molecule. Most of lifes macromolecules are polymers. Can anyone give me an example of a polymer? A polymer is a large molecule made up of repeating small molecules linked together. The subuints that serve as the builiding blocks of polymers are known as monomers. Monmers are linked together by a process known as condensation synthesis (draw on board). Polymers are broken down by the reverse process known as hydrolysis (to break with water)
Four classes of bio-macromolecues
Carbohydrate
The most common carbohydrates are sugars and starches. The simplest sugars are know as monosaccharides or simples sugars (glucose, galactose, fructose). Generally have structure CH2O. Glucose is the sugar that is probably the most important for living organism at least in terms of abundance. Table sugar (sucrose) is a disaccharide of glucose and fructose. One form of long chain polysaccharides are called starches. Glycogen (a polymer of glucose) is the storage form of sugar in animals. Plants also store sugar as starch. Bonds in starch are alpha linkages.
Cellulose is also a polymer of glucose and is found in plant cells. Both are made from glucose, but the difference is the carbons between which bonds are fomed. bonds on cellulose are beta likages. Beta linkages require different enzymes. Only a few organisms have enzymes that are able to hydrolyze cellulose.
Another important polysaccharide is chitin. Chitin is the material that makes up the exoskeletons of insects. The monomer is chitin is a glucose molecule with a nitrogen containing group bonded to one of the carbons. Chitin also makes up the bodies of some fungi.
Lipids
Lipids are what are known as hydrophobic compounds, that is they do not dissolve in water, (what happens when you mix water and oil). Three categories of lipids are fats, phospholipids and steriods.
Fats
Fats are large moleculs constructed from glycerol and fatty acids, draw on board. Acid end, hydrocarbon tail.
Saturated, unsaturated, trans fat. Most animal fats are saturated (lard, butter), solidify at room tempurature.
The major function of fats is energy storage. Food labels are based on a 2000 calorie diet. Most people have 600-800 calories stored in glycogen. Even the skinniest person has >50,000 calories stored in body fat. Fats also serve as insulation and cushioning for vital organs. Two fatty acids are essential for the human diet as they cannot be synthesized. The C-H bond has more energy than C-O bond which is why fats have more energy than carbohydrates.
Phospholipids.
Phopholipids have two fatty acids instead of three. The third carbon of glycerol is joined to a phophate group. Further small molcules can be joined to the phophate group. Draw on board. Phopholipid bilayer (biological membranes). Hydrophobic and hydrophilic properties.
Steroids
Steroids have a ring structure (4 interconnected rings). Different steroids have different groups attached to the rings. Cholesterol is a steroids. Many hormones, including the sex hormones (estrogens and testosterones) are steroids.
Other
Fats include waxes and some pigments.
Protein
Poteins account for more than 50% of the dry weight of cells and are instrumental to nearly all cell functions. Proteins perform a wide variety of functions from structural support, storage, to transport of other molecules. A human has tens of thousands of different proteins each with a unique function.
Amino acids
Amino acids are the building blocks of proteins. Draw basic amino acid structure (Carbon, hydrogen, NH2, COOH, R group). There are 20 amino acids that are the alphabet of protein structure. Amino acids are linked by peptide bonds formed between the acid group of one amino acid and the amino group of another amino acid. Chains of amino acids are called polypeptides. Proteins can be made of one or more polypeptides.
Protein Structure
Proteins can have up to four levels of structure. The primary structure of a protein is its amino acid sequence. The secondary structure of protein consists of regular coiling or layering as a result of hydrogn bonds along the polypeptide backbone (acid and amino groups). Alpha helix and beta sheet. The tertiary structure is a result of interactions between the amino acid side chains. Can be hydrogen bonding as well as covalent bonds. A protein has quaternary structure if it contains more than one peptide subuint. A proteins stucture is determined by its amino acid sequence.
Nucleic acids
nucleic acid structure-sugar (ribose or deoxyribose), phosphate, nitrogenous base (purine A,G-double ring, pyrimidine C,T,U-single ring)
A-T(U), G-C
There are two types of nucleic acids, DNA, RNA. These are the molecules that allow living organism to reproduce. DNA is the genetic material that organism inherit from their parents. Double helix structure (Campbell p.88)
RNA's function is to translate DNA into protein synthesis.
http://www.biology.arizona.edu/biochemistry/biochemistry.html Do the large molecules problem set
http://ocw.mit.edu/OcwWeb/Biology/7-012Fall-2004/VideoLectures/
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCHEM2.html
http://webcast.berkeley.edu/course_details.php?seriesid=1906978265 lecture 2
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