Molecules of Life

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Molecules of Life
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Molecules of Life

• Molecules of life are synthesized by living cells
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

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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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An Organic Compound Glucose

• Four models

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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

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Building Organic Compounds

• Cells form complex organic molecules
• Simple sugars ? carbohydrates
• Fatty acids ? lipids
• Amino acids ? proteins
• Nucleotides ? nucleic acids
• Dehydration synthesis combines monomers to form
  polymers

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Dehydration synthesis and Hydrolysis
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Carbohydrates The Most Abundant Ones

• Three main types of carbohydrates
• Monosaccharides (simple sugars)
• Oligosaccharides (short chains)
• Polysaccharides (complex carbohydrates)
• Carbohydrate functions
• Instant energy sources
• Transportable or storable forms of energy
• Structural materials

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Oligosaccharides Sucrose
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Complex Carbohydrates Starch, Cellulose, and
Glycogen
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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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Greasy, Oily Must Be Lipids

• Lipids
• Fats, phospholipids, waxes, and sterols
• Dont dissolve in water
• Dissolve in nonpolar substances (other lipids)
• Lipid functions
• Major sources of energy
• Structural materials
• Used in cell membranes

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Fats

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

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Triglyceride Formation
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Phospholipids

• Main component of cell membranes
• Hydrophilic head, hydrophobic tails

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Waxes

• Firm, pliable, water repelling, lubricating

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Steroids Cholesterol

• Membrane components precursors of other
  molecules (steroid hormones)

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Protein Structure

• Built from 20 kinds of amino acids

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Four Levels of Protein Structure

• 1. Primary structure
• Amino acids joined by peptide bonds form a linear
  polypeptide chain
• 2. Secondary structure
• Polypeptide chains form sheets and coils
• 3. Tertiary structure
• Sheets and coils pack into functional domains

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Four Levels of Protein Structure

• 4. Quaternary structure
• Many proteins (e.g. enzymes) consist of two or
  more chains

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Levels of Protein Structure
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Levels of Protein Structure
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Levels of Protein Structure
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Levels of Protein Structure
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Why is Protein StructureSo 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

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Normal Hemoglobin Structure
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VALINE
HISTIDINE
LEUCINE
GLUTAMATE
VALINE
THREONINE
PROLINE
b One amino acid substitution results in
the abnormal beta chain in HbS molecules.
Instead of glutamate, valine was added at the
sixth position of the polypeptide chain.
sickle cell
c Glutamate has an overall negative charge
valine has no net charge. At low oxygen levels,
this difference gives rise to a water-repellent,
sticky patch on HbS molecules. They stick
together because of that patch, forming rod
shaped clumps that distort normally rounded red
blood cells into sickle shapes. (A sickle is a
farm tool that has a crescent-shaped blade.)
normal cell
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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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Denatured Proteins

• If a protein unfolds and loses its
  three-dimensional shape (denatures), it also
  loses its function
• Caused by shifts in pH or temperature, or
  exposure to detergent or salts
• Disrupts hydrogen bonds and other molecular
  interactions responsible for proteins shape

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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

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Nucleotides of DNA
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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

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covalent bonding in carbon backbone
hydrogen bonding between bases