Biology Notes Ch 5 PDF

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Biology Notes from Chapter 5 - Professor Mummaw...

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CHAPTER 5: STRUCTURE & FUNCTION OF LARGE BIOLOGICAL MOLECULES Dehydration Reaction - A form of biochemical reaction wherein a water molecule is lost or removed from the reacting molecule - Dehydration removes a water molecule, forming a new bond Macromolecules - Polymers are formed when 2 or more monomers are connected during a dehydration or condensation reaction - This chemical reaction can be reversed to produce monomers during a reaction called hydrolysis Hydrolysis Reaction - The reaction of water with another chemical compound to form two or more products, involving ionization of the water molecule and usually splitting the other compound - Hydrolysis adds a water molecule, breaking a bond

Four Families of Organic Molecules Monomeric Form - Simple Sugar (Monosaccharide)

Polymeric Form - Disaccharide, Oligosaccharide, Polysaccharide

- Amino Acid

- Protein

- Fatty Acid

- Lipid

- Nucleotide

- Nucleic Acid

CHAPTER 5: STRUCTURE & FUNCTION OF LARGE BIOLOGICAL MOLECULES Sugars or Carbohydrates - All have the elements  (CH2O)n , where n=3-8 (ex. Glucose: C6H12O6) - Ketoses or Aldoses - Linear or Ring 

In aqueous solution, C of Aldehyde or Ketone group tends to react with -OH group

- Isomers - Cellular Functions 

Food Sources



Energy Storage



Modifying Element A polysaccharide can also react with itself to form a ring structure

- C of the aldehyde or ketone group in the ring form can also react with -OH group of another monosaccharide to form a disaccharide via glycosidic linkage - Glycogen & Starch: storage polysaccharides (animal & plant respectively) - Cellulose & Chitin: structural polysaccharides (plant & animal respectively) Cellulose - Chain of glucose linked by glycosidic linkages (hard to break bonds) Cellulase – enzyme that breaks bonds of cellulose (present only in a few bacteria & fungi) Fatty Acids (Lipids) - Amphipathic (i.e. having both hydrophilic & hydrophobic parts) - Various Lengths of C Chain - Some with double bonds (i.e. unsaturated hydrocarbons) - Cellular Functions: Food source, Energy Storage, & Membrane Structure

CHAPTER 5: STRUCTURE & FUNCTION OF LARGE BIOLOGICAL MOLECULES Fatty Acids Cont’d - Fatty Acids are stored as fats & oils in the form of triglycerides Triglyceride Molecule & Adipose Tissue - Phospholipids 

Glycerol backbone



2 fatty acids



Phosphate group with additional functional group attached

- Main component of Biological Membranes Amino Acids Parts of an Amino Acid - Central Carbon - Amino Group (ionize at pH 7) - Carboxyl Group (ionize at pH 7) - Hydrogen - R Group (side chain) (20 different) - Form Proteins & they in turn have a wide variety of functions 

Structural



Receptors



Enzymes



Channels



Transporters



Signaling Molecules

CHAPTER 5: STRUCTURE & FUNCTION OF LARGE BIOLOGICAL MOLECULES Enzymes - help speed up chemical reactions Metabolism – Sum of all the chemical reactions that occur in an organism Point of an enzyme: there is a basic requirement of energy needed to break bonds for a chemical reaction - Enzymes bind to reaction molecules or put them under stress, lowering the activation energy & making it easier to break bonds & start a reaction Formation of a Peptide Bond & Polypeptide Backbone - When 2 amino acids are positioned so that the carboxyl group of one is adjacent to the amino group of the other, they can become joined by a dehydration reaction - The resulting covalent bond is called a peptide bond - Repeated over & over this process yields a polypeptide (polymer of amino acids linked by peptide bonds) Proteins - “R groups” or “Side Chains” make amino acids unique 

Nonpolar



Uncharged, Polar



Charged, Acidic



Charged, Basic

- Properties of Side Chains of Amino Acids in a protein will determine the proteins 3-D Shape - 3-D Shape or Native Confirmation is crucial to a protein’s function - A functional protein consists of 1 or more polypeptides that have been precisely twisted, folded, & coiled into a unique shape.

CHAPTER 5: STRUCTURE & FUNCTION OF LARGE BIOLOGICAL MOLECULES Proteins Cont’d - The order of amino acids determines what the 3-D conformation will be. 3 Levels of Structure: Primary, Secondary, & Tertiary (used to organize the folding within a single polypeptide) - Quaternary structure arises when 2 or more polypeptides join to form a protein The function of a protein is an emergent property resulting from its specific molecular order Primary Structure The primary structure of a protein is its unique sequence of amino acids - Lysozyme, an enzyme that attacks bacteria, consists on a polypeptide chain of 129 amino acids - The precise primary structure of a protein is determined by inherited genetic information Secondary Structure The secondary structure of a protein results from hydrogen bonds at regular intervals along the polypeptide backbone - Typical shapes that develop from secondary structure are coils (an alpha helix) or folds (beta pleated sheets) Tertiary Structure Tertiary structure is determined by a variety of interactions among R groups & between R groups & the polypeptide backbone - These interactions include hydrogen bonds, ionic bonds, hydrophobic interactions and van der Waals Interactions - While these interactions are relatively weak, disulfide bridges, strong covalent bonds that form between the sulfhydryl groups (SH) of cysteine monomers, stabilize the structure

CHAPTER 5: STRUCTURE & FUNCTION OF LARGE BIOLOGICAL MOLECULES Quaternary Structure Quaternary Structure results from the aggregation of two or more polypeptide subunits (ex. Collagen is a fibrous protein of three polypeptides that are supercoiled like a rope & Hemoglobin is a globular protein with two copies of two kinds of polypeptides) Proteins Cont’d - A protein’s conformation can change in response to the physical & chemical conditions - Alterations in pH, salt concentration, temperature, or other factors can unravel or denature a protein Nucleotides Three Parts: Nitrogenous Base, Phosphate Group, & Five Carbon Sugar - Nucleotides bond together to form nucleic acids - Nucleic acids are important for gene expression - DNA  RNA  Protein - In addition to their role as the monomers from which nucleic acids are formed, nucleotides serve other important functions: Energy Currency, Coenzymes, & Signaling (2nd messengers or intracellular mediators)...