Organic Compounds

all living things fall into one of four classes of macromolecules: carbohydrates, lipids, proteins, and nucleic acids

macromolecules are polymers built from monomers

• polymer: a long molecule consisting of many similar building blocks
• these small building-block molecules are called monomers
• three of the four classes of life’s organic molecules are polymers: carbohydrates, proteins, and nucleic acids

carbohydrates (CH2O) → ratio 1:2:1

• carbohydrates serve as fuel and building material
• they can be divided into three categories: monosaccharides, disaccharides, and polysaccharides
  • monosaccharides, simple sugars, are the simplest carbohydrates
  • glucose is the most common monosaccharide
  • all monosaccharides contain two functional groups: carbonyl (C=O) and a hydroxyl (OH)
  • monosaccharides serve as major fuel for cells and as raw material for building molecules
  • disaccharides are formed by joining two monosaccharides
  • sucrose, eg. table sugar
  • lactose, eg. sugar in milk
  • suffix is “-ose” for most sugars
  • carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks
  • made by linking many monosaccharides
    • eg. starch is a chain of many glucose molecules
  • have storage and structural roles
    • storage polysaccharides—starch and glycogen
    • structural polysaccharides—cellulose and chitin

storage polysaccharides

• chitin is present in plants and consists entirely of glucose monomers
• glycogen is present in animals and consists entirely of glucose monomers; it is how animals store sugars
  • humans and other vertebrates store glycogen mainly in liver and muscle cells
  • perennials: never die—need stored sugars (starch) to build stem and leaves in the Spring, then photosynthesize

structural polysaccharides

• chitin is found in the exoskeleton of arthropods (a kind of animals)
  • also provides structural support for the cell walls of many fungi
• cellulose is a major component of the tough wall of plant cells, also made of glucose monomers
  • humans can’t digest cellulose because we lack the enzymes to break the beta linkages between glucose molecules; we can break it down to some extent, but not at the molecular level

lipids

• the most biologically important lipids are fats, oils, phospholipids, cholesterol, and steroids
• lipids are non-polar parts of living things which contain long hydrocarbon tails
  • consist of a glycerol head and fatty acid tails
• triglycerides consist of a glycerol head and three fatty acid tails
  • provide us with the most energy per gram of any substance
• fats
  • saturated fats
  • animal fats like butter and grease
  • solidify at room temperature
  • carbons are “saturated” with hydrogen
  • unsaturated fats
  • plant oils like olive oil and peanut oil
  • remain liquid at room temperature
  • have hydrocarbon tails, long chains if C-H that are linked because the carbons are not saturated with hydrogen (C=C)
• phospholipids
  • material of all cell membranes
  • phospholipid-glycerol, two fatty acids, and a phosphate group polar heads and non-polar tails
  • polar heads are hydrophilic (have an affinity to water)
  • non-polar tails are hydrophobic (repel water)
• steroid: a lipid molecule in which the carbon solution forms four fused rings
• cholesterol: an important steroid in animal cell membranes
  • can help membranes stay fluid by keeping the phospholipids from packing tightly together
  • used to make essential molecules such as hormones, fat-soluble vitamins, and bile acids

functions of lipids/fats

1. energy storage (MAIN FUNCTION)
2. humans and other mammals store their fat in adipose cells
3. adipose tissue cushions vial organs and insulates the body

proteins

• all enzymes are made of protein, but not all proteins are enzymes
• protein: a polymer made of amino acid monomers
  • there are 20 amino acids; the human body can produce twelve, so we need eight from our diet
• proteins have hundreds of functions, here are a few major ones:
  • work as enzymes
  • some are embedded in cell membranes that assist in the transport of substances
  • antibodies of the immune system are proteins
  • serve as hormones (chemical messengers)
  • muscle cells are made of protein and contract
  • structural proteins--collagen, ligaments, tendons
• different proteins differ in number and order/arrangement of amino acids
  • amino acids are covalently bonded by peptide bonds
  • a polypeptide is a chain of amino acids with many peptide bonds
  • peptide bonds are connectors—if you have 40 amino acids, you will have 39 peptide bonds (one connecting each to the next)
  • a protein consists of one or more polypeptides
  • the sequence of amino acids determines the shape of a protein; its shape determines its function
• denaturation: a process which changes the shape of a protein
  • temperature and pH level are the two main causes of denaturation
• since the shape of the protein determines its function, the protein can no longer perform its function once it has been denatured

nucleic acids

• nucleic acid: a polymer made of monomers called nucleotides
  • eg. DNA, RNA
• nucleotide: a monomer consisting of sugar, a phosphate group, and a nitrogen-containing base

enzymes

• activation energy: the amount of energy that must be absorbed for a chemical reaction to start
• catalyst: a substance that decreases the activation energy needed to start a chemical reaction, therefore speeding up the rate of the reaction
• enzyme: a catalyst made of protein which is present in living things
  • structure dictates function
  • changes in pH and temperature can affect shape and function
  • high fever/hypothermia denatures enzymes, causing functional problems

common characteristics of organic compounds

• soluble in organic solvents, insoluble in water
• high molecular weight
• contain complex structures
• properties are dependent on their functional groups
• most consist of some combination of carbon, hydrogen, and oxygen
• usually combustable in nature

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