Molecules of Life

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Molecules of Life

• Chapter 3

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Molecules of Life
Glucose 4 models

• Molecules of life are synthesized by living cells
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids
• Structure to Function
• Molecules of life differ in three-dimensional
  structure and function
• Carbon backbone
• Attached functional groups
• Structures give clues to how they function
• Organic Compounds
• Consist primarily of carbon and hydrogen atoms
• Carbon atoms bond covalently with up to four
  other atoms, often in long chains or rings
• Functional groups attach to a carbon backbone
• Influence organic compounds properties

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Biological Molecules are Organic Compounds

• Carbon atom
• Basis of all organic compounds
• Tetravalent can form four covalent bonds
• Forms bonds most often with O, H, or N
• Functional groups are
• Combinations of important elements with distinct
  chemical properties
• Transferred as a unit from one atom to another
  atom
• Critical to most metabolic reactions

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Functional Groups The Importance of Position
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Processes of Metabolism

• Cells use energy to grow and maintain themselves
• Enzyme-driven reactions build, rearrange, and
  split organic molecules
• Building Organic Compounds
• Cells form complex organic molecules
• Simple sugars ? carbohydrates
• Fatty acids ? lipids
• Amino acids ? proteins
• Nucleotides ? nucleic acids
• Condensation combines monomers to form polymers

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What Cells Do to Organic Compounds
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Macromolecules

• Macromolecules are large polymers composed of
  smaller building blocks
• Macromolecules may contain many different
  functional groups.
• Four major groups of macromolecule

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Macromolecules
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The Formation of Macromolecules

• Monomers assemble to form polymers through
  similar process.
• Dehydration synthesis removal of a water
  molecule links two monomers
• Hydrolysis addition of water breaks bond between
  monomers degrades polymer

The process of dehydration synthesis uses energy,
which is stored in the bond that is made.
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Condensation and Hydrolysis
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Carbohydrates-The Most Abundant Ones

• Carbohydrates have carbon, hydrogen, and oxygen,
  in a 121 ratio
• Carbohydrates are produced through
  photo-synthesis by plants, algae, and some
  bacteria.
• Carbohydrates are instant energy sources,
  transportable or storable forms of energy, and
  structural components for living organisms.
• Three main types of carbohydrates
• Monosaccharides (simple sugars)
• Oligosaccharides (short chains)
• Polysaccharides (complex carbohydrates)

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Monosaccharides
Simple Sugars

• Monosaccharide comes from two Greek words meaning
  single (mono) and sweet (saccharon). They are
  simple sugars (C3-C9) for energy storage and
  utilization.
• Glucose (C6H12O6) is the primary energy-storage
  molecule in the living things.
• Fructose has the same molecular formula as
  glucose, but is much sweeter than glucose.

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Monosaccharides
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Disaccharides

• Disaccharide is a molecule with two
  monosaccharides linked by a dehydration reaction.
• Disaccharides are used by many organisms (e.g.,
  plants) as transport forms of sugar.
• Sucrose is a common transport form of sugar in
  plant. Lactose (milk sugar) is produced by many
  mammals to feed their young.

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Polysaccharide as Energy Storage Form

• Organisms convert soluble carbohydrates,
  monosaccharides, to an insoluble form,
  polysaccharide, to be stored for long.
• Polysaccharides macromolecules formed from many
  monosaccharides linked together
• Polysaccharides play roles as energy storage form
  as well as structural components in both many
  organisms.
• Starch is the energy storage form in plants
  while animals use a highly branched
  polysaccharide, glycogen(??).
• Glycogen storage granules can be seen
• in the cytoplasm of liver cells, muscle
• cells, and some types of white blood cells

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Polysaccharides

• Functions of polysaccharides storage, structure,
  recognition
• Storage of energy starch, glycogen
• Structural materials cellulose, chitin,
  polysaccharides of bacterial cell wall
• Cell surface polysaccharides are recognition
  molecules
• Starch and glycogen are storage molecules, made
  from amylose (????, a(1?4) links, unbranched) and
  amylopectin (???, a(1?4) and a(1?6) links,
  branched)
• Cellulose Structural support for plant cells
• Glucose polysaccharide with bonds in straight
  orientation
• Glycogen Animal energy, branched
• Starch Plant energy, branched or unbranched
• Chitin(???) and cellulose (???) are structural
  molecules
• Chitin Exoskeleton of arthropods such as
  butterfly and crab
• Modified sugars in chains

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Complex Carbohydrates Bonding Patterns
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Complex Carbohydrates Starch, Cellulose, and
Glycogen

• Starch and glycogen are storage molecules, made
  from amylose (????, a(1?4) links, unbranched) and
  amylopectin (???, a(1?4) and a(1?6) links,
  branched)

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Complex Carbohydrates Starch, Cellulose, and
Glycogen

• Cellulose Structural support for plant cells
• Glucose polysaccharide with bonds in straight
  orientation

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Complex Carbohydrates Starch, Cellulose, and
Glycogen

• Glycogen Animal energy, branched

c Glycogen. In animals, this polysaccharide is a
storage form for excess glucose. It is especially
abundant in the liver and muscles of highly
active animals, including fishes and people.
Structure of cellulose
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Complex Carbohydrates Chitin

• Chitin(???) and cellulose (???) are structural
  molecules
• Chitin Exoskeleton of arthropods such as
  butterfly and crab
• Modified sugars in chains

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Fats and Lipids

• Lipids are usually used by many organisms as a
  long term energy storage form.
• Lipid can store more energy than polysaccharides
  per unit weight.
• Fats are large, nonpolar, water-insoluble
  molecules used as energy reserves and protection
• Three important categories of lipid
• 1) Oils, fats, and waxes
• 2) Phospholipids
• 3) Steroids
• Lipid functions
• Major sources of energy
• Structural materials
• Used in cell membranes

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Molecular Structure and Behavior of Lipids

• Lipid Unlike the protein, nucleic acid, and
  polysaccharide, not polymers
• Contain high levels of chemical energy
• Have few polar functional groups Do not dissolve
  in water
• Functional roles of lipids Energy storage,
  membrane constituents, hormones, fat-soluble
  vitamins (Vit-E), thermal insulator, biological
  regulator prostaglandin
• Fatty acids hydrophilic carboxylate
  hydrophobic chain, may be saturated (no double
  bonds) or unsaturated (contain 1 double bonds).
• Virtually all biologically produced unsaturated
  fatty acids contain cis double bonds, which
  induce a bend in the molecules

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Fats

• Lipids with one, two, or three fatty acid tails
• Saturated
• Unsaturated (cis and trans)
• Triglycerides (neutral fats )
• Three fatty acid tails
• Most abundant animal fat (body fat)
• Major energy reserves

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Saturated or Unsaturated Fatty Acids

• Fatty acids of most plant triglycerides are
  unsaturated. Animal fat, in contrast, are often
  saturated and occur as hard fats.
• Diets with large amount of saturated fats may
  contribute to clogged arteries and raise the risk
  of developing cardio-vascular diseases.

Trans and Cis Fatty Acids
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Lipids are Composite Molecules

• Oil and fat are built from two different kinds of
  subunits Glycerol and three attached fatty
  acids. The resulting molecule is called
  Triglyceride (?????).
• Triglycerides are storage and transport form of
  fat in the body.

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Triacylglycerol (Fat) glycerol triester of FA

• Triacylglycerol three fatty acids are esterified
  to glycerol, the resulting molecule is a fat (if
  solid at room temperature) or an oil (if liquid
  at room temperature).
• Fats are rich in unsaturated fatty acids are
  typically oils.
• Esterification of the fatty acids to make fats
  greatly diminishes the hydrophilic nature of the
  polar end of the original fatty acid.
  Consequently, fats are very nonpolar and do not
  form micelles readily. Fats are used to store
  energy in adipocytes.

• Function of fat storage
• -Energy production oxidation of fat to
  generate ATP for metabolic process.
• -Metabolic oxidation of fats yields 37 kJ/g,
  carbohydrates and proteins yield only 17 kJ/g
• -Heat production Some cells oxidize
  triacylglycerols for heat production
• -Insulation layer of fat cells as thermal
  insulator

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Phospholipids

• Phospholipids are the major structural components
  of all cell membranes.
• Differ from fats, phospholipids are composed of
  glycerol, 2 fatty acids, and a phosphate group.
• Functional groups (serine, ethanolamine, choline,
  or inositol) attach to phosphate to form diverse
  types.

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Sterols Cholesterol

• Membrane components precursors of other
  molecules (steroid hormones)
• Steroids
• With 4 carbon rings
• Important for membrane fluidity
• Risk factors for heart attack, high blood
  pressure, stroke

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Proteins- Diversity in Structure and Function

• Nucleic acid Store and transmit genetic
  information of the cell
• Protein Genetic information is expressed in the
  form of protein
• Functions of Proteins
• -Structural organization of cells and tissues
• -Metabolic process
• -Regulation
• -Defense
• -Communication
• -Transport and storage of small molecules
• -Enzymes catalyze biosynthesis and metabolism
• -Immunology Antibody
• -Protease
• Ex muscle contraction,
• immune response,
• blood clotting

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Amino Acids
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Amino Acids
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Protein Synthesis
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Hydrolysis of Protein
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Proteins Structures and Functions
Hierarchy of structural organization Structure
determines function Shape - globular or
fibrous - Primary sequence Primary
structure All of the information necessary for
folding the peptide chain into its "native
structure is contained in the primary amino acid
structure of the peptide. - Secondary - local
structures Secondary structure" refers to local
folding of the backbone of a linear polymer to
form a regular, repeating structure, determined
by the amino acid sequence and the solvent
environment in which it is located . - Tertiary
- overall 3-dimensional shape The overall shape
of a polypeptide arises from the different
regions of secondary structure folding upon each
other and is called the tertiary structure -
Quaternary - subunit organization Quaternary
structure involves two or more separate peptides.
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Levels of Protein Structure
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Levels of Protein Structure
barrel
c Protein tertiary structure A chains coiled
parts, sheetlike arrays, or both have folded and
twisted into stable, functional domains,
including clusters, pockets, and barrels.
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Levels of Protein Structure
D Protein quaternary structure Many weak
interactions hold two or more polypeptide chains
together as a single molecule.
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Why is Protein Structure So Important?

• Protein structure dictates function
• Sometimes a mutation in DNA results in an amino
  acid substitution that alters a proteins
  structure and compromises its function
• Example Hemoglobin and sickle-cell anemia

Normal Myoglobin Structure
a Globin. The secondary structure of this
polypeptide includes several helixes. The coils
fold up to form a pocket that cradles heme, a
functional group with an iron atom at its center.
The kind of molecular representation shown here
is called a ribbon model, after its appearance.
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Normal Hemoglobin Structure
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Sickle-Cell Mutation
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Sickle-Cell Mutation
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Clumping of cells in bloodstream
Circulatory problems, damage to brain, lungs,
heart, skeletal muscles, gut, and kidneys
Heart failure, paralysis, pneumonia, rheumatism,
gut pain, kidney failure
Spleen concentrates sickle cells
Spleen enlargement
Immune system compromised
Rapid destruction of sickle cells
Anemia, causing weakness,fatigue, impaired
development,heart chamber dilation
d Melba Moore, celebrity spokes-person for
sickle-cell anemia organizations. Right, range of
symptoms for a person with two mutated genes for
hemoglobins beta chain.
Impaired brain function, heart failure
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Prions and Protein Folding

• Prions (proteinaceous infectious particle) an
  unusual class of proteins that can transmit
  disease independently of nucleic acids.
• Diseases caused by prions include bovine
  spongiform encephalopathy (mad cow disease),
  scrapie in sheep, and kuru, Creutzfeldt-Jakob
  disease, fatal familial insomnia in humans.
• The protein believed to be responsible for
  transmitting the disease is called
  prion-related-protein, or PrP.
• Prp is present in many animals, including humans,
  in a non-pathological form called PrPc
  (prion-related protein cellular).
• Under certain circumstances, PrPc can change
  conformation to the sheet-rich structure, forming
  PrPsc (prion related protein scrapie).
• It is the PrPsc form that wreaks havoc with the
  nervous systems of infected individuals.

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Nucleotides, DNA, and RNAs

• Nucleotide structure, 3 parts
• Sugar
• Phosphate group
• Nitrogen-containing base

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Nucleotide Functions Reproduction, Metabolism,
and Survival

• DNA and RNAs are nucleic acids, each composed of
  four kinds of nucleotide subunits
• ATP energizes many kinds of molecules by
  phosphate-group transfers
• Other nucleotides function as coenzymes or as
  chemical messengers

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Nucleotides of DNA
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Two Forms of Nucleic acids

• Deoxyribonucleic acid (DNA) stores the
  information for making proteins
• Ribonucleic acid (RNA) decodes the hereditary
  information of DNA and directs the production of
  proteins

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DNA, RNAs, and Protein Synthesis

• DNA (double-stranded)
• Encodes information about the primary structure
  of all cell proteins in its nucleotide sequence
• RNA molecules (usually single stranded)
• Different kinds interact with DNA and one another
  during protein synthesis