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