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The Molecular Building Blocks of Life

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Title: The Molecular Building Blocks of Life


1
The Molecular Building Blocks of Life

2
Objectives
  • 3.2.1 Distinguish between organic and inorganic
    compounds.
  • 3.2.2 Recognize the physical differences
    between the macromolecules that are the
    building blocks of life.
  • 3.2.3 State the uses for carbohydrates, lipids,
    nucleic acids, and proteins

3
The Importance of carbon
  • Cells are 70-95 water, the remainder is mostly
    carbon-based compounds.
  • Proteins, DNA, carbohydrates, lipids
    distinguish living matter from inorganic
    material all are composed of carbon atoms
    bonded to each other to atoms of other
    elements, including H, O, N, S, P (percentages
    are quite uniform in all life).
  • oxygen (65 percent)
  • carbon (18 percent)
  • hydrogen (10 percent)
  • nitrogen (3 percent)
  • phosphorus (1 percent) and
  • sulfur (0.2 percent).

4
Organic chemistry
  • Organic chemistry is the study of carbon
    compounds.
  • Produced not only in biological processes, they
    can also be synthesized by non-living reactions.
  • Organic compounds range from simple CH4
    (below), to complex molecules, like proteins
    DNA (at right).

5
Organic chemistry
  • Organic compounds contain carbon hydrogen
    together!
  • CH4 methane, C8H18 octane, C6H12O6 glucose
  • If a carbon compound is not accompanied by
    hydrogen, it is considered inorganic.
  • CO2 inorganic (no H)
  • CCl4 inorganic (no H)
  • CoCl2 inorganic (no C)
  • CaHPO4 inorganic (no C)
  • HCl inorganic (no C)
  • Dont be fooled!

6
Atomic carbon
  • Carbon atoms are the most versatile building
    blocks of molecules.
  • With a total of 6 e-, a C atom has 2 in the first
    shell and 4 in the second shell.
  • Only outer shell elec- trons are involved in
    chemical reactions, so C has 4 e- to
    share (it makes 4 attachments).

7
Carbon is tetravalent
  • Carbon shares 4 electrons.

Note C makes 4 attachments, but H makes only 1.
8
Carbon is tetravalent
  • Carbon can bond with itself there are still
    always 4 attachments (4 bonds).
  • Ethylene (-ene signifies a double bond)
  • Isomers of butyne
  • (-yne signifies a triple bond) still
    a total of four bonds on each
    carbon atom.

9
Carbon is tetravalent
  • The e- configuration of C lets it form covalent
    bonds with many different elements.
  • In carbon dioxide, one C atom forms 2 double
    bonds with 2 different O atoms. The structural
    formula, O C O, shows that each atom has
    completed its valence shells. CO2 is the source
    for all organic molecules in organisms via the
    process of photosynthesis.

10
Carbon is tetravalent
  • Another example
  • Urea, CO(NH2)2, is a simple organic
    molecule in which each atom has enough
    covalent bonds to
    complete its valence shell.
  • H needs 1 e-
  • O needs 2 e-
  • N needs 3 e-

11
Hydrocarbons
  • Hydrocarbons organic molecules that consist of
    only C H.
  • Hydrocarbons are the major component of
    petroleum.
  • Petroleum is a fossil fuel because it consists of
    the partially decomposed remains of organisms
    that lived millions of years ago.

12
Carbon-based life forms
  • Life on Earth is based on carbon.
  • Four types of carbon molecules are building
    blocks.
  • Carbohydrates
  • Lipids
  • Nucleic acids
  • Proteins

13
Carbohydrates
  • Function fuel and building material made of
    equal amounts of CH2O (carbon hydrates). H 2x
    O.
  • Monosaccharides (simple sugars).
  • Ex glucose
  • Disaccharides (double sugars).
  • Ex sucrose
  • Polysaccharides are long chains of
    monosaccharides.
  • Ex starch (in flour)

14
Carbohydrates
  • Monosaccharides have molecular formulas that are
    some multiple of CH2O. Ex glucose - C6H12O6.
    (H 2x O)
  • Most names for sugars end in ose glucose,
    ribose.
  • Disaccharides form from monosaccharides by
    dehydration (an H and an OH are removed).

Glucose glucose produces maltose (and water)
15
Carbohydrates
  • Polysaccharides are polymers of hundreds to
    thousands of monosaccharides.
  • Function in energy storage (used as needed).
  • Ex starch (plants) glycogen (in animals
    livers)
  • Function as strong building materials. Ex
    cellulose

16
Lipids
  • Lipids are hydrophobic dont mix with water.
  • In a triglyceride, three fatty acids (same or
    different) are joined to glycerol. Made of C, H,
    O, but the HO ratio is much greater than 21.

17
Lipids
  • A saturated fat has no carbon-carbon double
    bonds, and it is straight.
    They pack together solid at room temperature.
  • Unsaturated fats have one or more carbon-carbon
    double bonds, and they bend. They cant get
    close to each other, so they are liquid at room
    temperature.

18
Lipids
  • Saturated fats come from animal products.
  • Ex butter, lard
  • A diet rich in saturated fats may contribute to
    cardiovascular disease (heart attack, stroke)
    through plaque deposits in arteries obesity,
    diabetes.

19
Lipids
  • Unsaturated fats come from plant fish products.
  • Ex olive oil, corn oil, safflower oil, fish
    oils.
  • Generally considered healthier for the heart.

20
Lipids
  • Functions of lipids
  • Nutrition 1g of fat contains twice as much
    energy as 1g of carbohydrate.
  • Protection cushions vital organs insulates
    them.
  • This subcutaneous layer is
    especially thick in whales,
    seals, and most other
    marine mammals.

21
Lipids
  • Functions of lipids
  • Phospholipids major components of cell
    membranes.
  • Have two fatty acids attached to glycerol and a
    phosphate group at the third position.

22
Lipids
  • Functions of lipids
  • Waxes reduce water loss by plants.
  • Carnauba wax
  • Steroids
  • Cholesterol is a component in animal cell
    membrane.
  • Many steroids are hormones.

23
Nucleic acids
  • All molecules of the body are programmed by a
    genetic code in the organisms DNA, a polymer of
    nucleic acids.
  • Nucleic acids store and transmit hereditary
    in- formation.
  • Made of C, H, O, N, P.

A nucleic acid
24
Nucleic acids
  • There are two types of nucleic acid polymers
  • Ribonucleic acid (RNA)
  • Single-stranded.
  • Contains adenine, guanine,
    cytosine, and uracil.
  • Sugar is ribose.
  • Deoxyribonucleic acid (DNA)
  • Double stranded.
  • Contains adenine, guanine, cytosine, and thymine.
  • Sugar is deoxyribose.

25
Proteins
  • Humans have at least 30,000 different proteins,
    each with a unique structure and function.
  • Functions include structural support, storage,
    transport of materials, intercellular signaling,
    movement, and defense.
  • Enzymes are one class of proteins that regulate
    metabolism by moderating chemical reactions.
  • All proteins are 3 dimensional.
  • All are constructed from the same set of 20
    monomers, called amino acids.
  • All are made of C, H, O, and N (2 also contain S).

26
Proteins
  • Amino acids are joined by
    dehydration the resulting covalent
    bond is called a peptide
    bond.
  • Polymers of amino acids are called
    polypeptides.

27
Proteins
  • A proteins function depends on
    its precise twisting, folding, and
    coiling into a unique
    shape.
  • The order of amino acids determines what the
    three- dimensional shape will be.
  • Folding of a protein occurs spontaneously an
    emergent property resulting from
    its specific molecular order.

28
Proteins
  • In individuals with sickle cell disease, abnormal
    hemoglobins develop because of a single amino
    acid substitution.

29
Proteins
  • Fibrous proteins are long, insoluble molecules .
  • For movement (muscle fibers)
  • For structure and support.  
  • Collagen in skin.
  • Cartilage connects tissues.
  • Keratin is found
  • in hair, horns, wool,
    nails, and feathers.

30
Proteins
  • Globular proteins are soluble and form compact
    spheroidal molecules in water.  
  • Antibodies for immunity.
  • Enzymes are involved in chemical reactions
    - metabolism (enzymes generally end in
    ase).
  • Transport proteins and receptor proteins in
    the cell membrane.

Hemoglobin transport of oxygen
31
Proteins
  • Transport proteins and receptor proteins in the
    cell membrane capture chemicals in the blood and
    may move them into the cell.

32
Proteins
  • Enzymes catalyze chemical reactions (metabolism).
  • One enzyme is specific for each chemical
    reaction.
  • Enzymes convert one substrate (the
    raw material) into some product.
  • Ex sucrase binds to sucrose and
    breaks this disac-
    charide into fruc-
    tose and glucose.
  • Enzymes end in ase.

33
Proteins
  • A proteins shape can change in response to
    changes in pH, salt concentration, temperature.
    These forces disrupt the bonds that maintain the
    proteins shape. This is called denaturation.
    Then the protein wont work right!
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