The Molecules of Life

1
The Molecules of Life

• Chapter 5

2
CARBON AND THE MOLECULAR DIVERSITY OF LIFE

• Although cells are 70-95 water, the rest
  consists mostly of carbon-based compounds.
• Proteins, DNA, carbohydrates, and other molecules
  that distinguish living matter from inorganic
  material are all composed of carbon atoms bonded
  to each other and to atoms of other elements.
• These other elements commonly include hydrogen,
  oxygen, nitrogen, sulfur, and phosphorus.

3

• The overall percentages of the major elements of
  life (C, H, O, N, S, and P) are quite uniform
  from one organism to another.
• While the percentages of major elements do not
  differ within or among species, variations in
  organic molecules can distinguish even between
  individuals of a single species.

4
Organic chemistry is the study of carbon compounds

• The study of carbon compounds, organic chemistry,
  focuses on any compound with carbon (organic
  compounds).
• While the name, organic compounds, implies that
  these compounds can only come from biological
  processes, they can be synthesized by non-living
  reactions.
• Organic compounds can range from the simple (CO2
  or CH4) to complex molecules, like proteins.
• Inorganic molecules are non-carbon based
  molecules

5

• Hydrocarbons are organic molecules that consist
  of only carbon and hydrogen atoms.
• 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.

6

• Monomer- a smaller molecular unit
• rings of C, H, and O are called monosaccharides
• Examples glucose, fructose, galactose, ribose,
  deoxyribose
• Glucose C6H12O6

7

• Polymers- are chains of monomers created by
  chemical reaction called condensation (also
  called dehydration synthesis)
• Simplest polymer is disaccharide
• Examples sucrose, lactose, maltose

8
Four Macromolecules for Life

• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids
• (will be discussed in later chapters)

9
Carbohydrates

• Carbohydrate organic compound made up of sugar
  molecules
• Sugars contain the elements carbon, hydrogen, and
  oxygen in the ratios of 121
• Monosaccharide
• one sugar unit also known as simple sugars
  (glucose)
• Disaccharide
• two sugar units also known as a double sugar
  (sucrose)
• Polysaccharide
• many sugar units (glycogen and starch)
• Sugar molecules (especially glucose) are the main
  fuel supply for cellular work

10

• Disaccharide

• Polysaccharide

11

• Cellulose- functions to provide structure to
  plants indigestible to mammals (fiber on food
  label)
• Chitin- functions in external skeleton of
  arthropods

12

• Glycogen- a polysaccharide that is stored in some
  animals
• It is more branched than starch
• In humans it is stored as granules in liver and
  muscle cells
• When the body needs energy, these molecules are
  broken down into glucose molecules and used

13
Proteins

• Greek word for 1st place
• Very important class of polymers
• Have roles in almost every job a cell does
• Amino Acid monomer (building block) of a protein
• Consists of a central carbon atom surrounded by
  an amino group, a carboxyl group, and a
  side-chain (that can be another molecule), and a
  hydrogen atom

14

• There are 20 different amino acids that can be
  arranged in a number of different ways
• Amino acids link together to form polypeptides
• Proteins are made up of one or more polypeptide
  chains
• Can have from 50 to more than 1000 amino acids
  arranged in any possible sequence
• Human cells make between 80,000-100,000 different
  proteins

15

• Proteins have a 3D shape determined by the
  interactions between the amino acids
• Denaturation the process in which a proteins
  natural three-dimensional structure is disrupted
• cooking an egg

16

• Enzymes specialized proteins that are the main
  catalysts of the chemical reactions that occur in
  organisms
• Reduce the amount of energy needed for a chemical
  reaction to occur
• What is a catalyst?
• Compounds that speed up chemical reactions
• (Does not get used up during a chemical reaction)
• Each enzyme catalyzes a specific type of chemical
  reaction
• Enzymes have a specific shape that fits each set
  of reactant molecules

17

• Substrate a specific reactant acted upon by an
  enzyme
• Active site the region of the enzyme in which
  the substrate fits
• Once the substrate fits together with the active
  site the reaction is catalyzed

18

• Functions of Proteins
• Enzymes
• Transport proteins
• Hemoglobin
• Hormones
• Insulin
• Chorionic gonadotropin
• Structural proteins
• Collagen

19
Lipids

• Composed of C, H, and O
• Insoluble in water (hydrophobic)
• Fats are biological molecules that have a
  three carbon backbone (called glycerol) attached
  to three fatty acids (long hydrocarbon tails)
• Solids fats
• Liquids oils
• Function in energy storage, insulation, organ
  protection

20

• Saturated Fat contains the maximum number of
  hydrogen atoms
• all the carbon atoms form single bonds
• Unsaturated Fat contains less than the maximum
  number of hydrogen atoms in one or more of its
  fatty acid chains
• Some of the carbons form double bonds

21

• Phospholipids
• Very important component of the cell membranes

22
(No Transcript)
23

• Steroid a lipid molecule in which the carbon
  skeleton forms four fused rings
• Classified as fats because they are hydrophobic
• Function as chemical signals in our bodies
• Hormones such as testosterone and estrogen
• Cholesterol is an essential molecule found in the
  membranes that surround your cellsit is also the
  starting point from which your body produces
  other steroids