Chapter 20: Biochemistry

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• Chapter 20 Biochemistry

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Biochemistry

• Biochemistry is the study of chemistry that takes
  place in the living cell.
• There are several important classes of
  biochemical compounds
• Carbohydrates
• Lipids
• Amino acids and proteins
• Nucleic acids
• Vitamins and hormones

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Carbohydrates

• Carbohydrates contain carbon, hydrogen, and
  oxygen and have the general formula Cx(H2O)y
• Simple carbohydrates or sugars (like glucose,
  C6H12O6) are called monosaccharides.
• Disaccharides can be hydrolyzed to 2
  monosaccharides
• Disaccharide H2O 2 monosaccharides
• Polysaccharides are hydrolyzed to many
  monosaccharides
• Polysaccharide nH2O n
  monosaccharides

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Monosaccharides

• Monosaccharides contain a carbonyl group and
  several hydroxyl groups.
• If a monosaccharide is an aldehyde, it is called
  an aldose.
• If the monosaccharide is a ketone, it is a
  ketose.
• The names of the monosaccharides end in ose.

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MonosaccharidesClassification by Carbon Atoms

• Number of Carbon Monosaccharide
• Atoms Class
• 3 Triose
• 4 Tetrose
• 5 Pentose
• 6 Hexose

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Naming Classes can be Combined

• Glucose is an aldehyde with six carbon atoms. It
  is an aldohexose.
• Ribose is an aldehyde with five carbon atoms. It
  is an aldopentose.
• Fructose is a ketone with six carbon atoms. It
  is a ketohexose.

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Chiral Carbons

• A carbon that has four different groups around it
  is chiral. These four different groups can be
  arranged two different ways.
• There are four chiral carbons in the aldohexose.
  This leads to a possibility of 16 isomers.
• Different names designate these isomers.
• Isomers that have the OH group on the 5th carbon
  on the right is D-.
• Isomers that have the OH group on the 5th carbon
  on the left are L-.

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Sugars are Polyhydroxy Aldehydes and Ketones
Insert figure 20.2
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Cyclic Structures

• Cyclic structures are formed by aldohexoses when
  one of the hydroxyl groups react with the
  carbonyl group to form a hemiacetal

Or
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Mutarotation

• Opening and closing the ring structure is called
  Mutarotation

Or
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Common Monosaccharides
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Disaccharides

• Hydrolysis Products

Maltose H2O 2 glucose
Lactose H2O glucose galactose
Sucrose H2O glucose fructose
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Disaccharides
Beta acetal
fructose
glucose
galactose
Alpha acetal
glucose
Alpha acetal
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Polysaccharides

• Starch Made of glucose units bound by alpha
  acetal bonds. Digestible by humans. Source of
  energy in diet. Compose of amylose and
  amylopectin.
• Cellulose Made of glucose units bound by beta
  acetal bonds. Not digestible by humans. Source
  of fiber in diet.

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Metabolism

• When carbohydrates are metabolized, they are
  broken into glucose molecules. The glucose
  molecules combine with oxygen to yield CO2, H2O,
  and energy
• C6H12O6 6O2 6CO2 6H2O Energy

Carbohydrates supply approximately 4 kcal of
energy per gram.
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Lipids

• Lipids are biological compounds that are soluble
  in organic solvents and insoluble in water.
• Simple lipids are esters of glycerol and fatty
  acids.
• Phospholipids contain a phosphate group.
• Steroids have a ring structure.
• Prostaglandins have a wide range of effects.

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Triglycerides

• Triglycerides are esters of glycerol and fatty
  acids (long chain carboxylic acids).

3C17H35COOH
Stearic acid (a fatty acid)
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Fats and Oils

• Fats are solids derived from animals. They
  contain mostly saturated fatty acids.
• Oils are liquids derived from plants. They
  contain a larger proportion of unsaturated fatty
  acids.
• Saturated fatty acids contain no CC double
  bonds.
• Monounsaturated fatty acids contain one CC
  double bond.
• Polyunsaturated fatty acids contain more than one
  CC double bond.

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Insert figure 20.9
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Amino Acids

• Amino acids are the monomer units in the
  biological polymer protein.
• An amino acid contains a carboxyl group and an
  amino group

Carboxyl group
Amino group
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Zwitterion

• The carboxyl group transfers a proton to the
  amino group to form a zwitterion

Zwitterion
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Peptide Bond

• Two amino acids are joined by forming an amide
  between the carboxyl group of one amino acid and
  the amino group of the other amino acid

H2O
(A dipeptide)
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Peptides

• The amide link between amino acids is called the
  peptide bond.
• The compound formed when two amino acid are
  joined by a peptide bond is called a dipeptide.
• Three amino acids form a tripeptide.
• Ten or more amino acids form a polypeptide.
• When a polypeptide has a molecular weight of
  10,000 or more, it is called a protein.

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Protein Structure

• The amino acid structure is called the primary
  structure of the protein.
• The secondary structure is the way the amino acid
  chain coils around.
• The tertiary structure is the general overall
  shape of the protein molecule.

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Structure of a Segment of a Protein Molecule
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Enzymes

• Enzymes are proteins that act as biochemical
  catalysts.
• Enzymes can increase reaction rates by a factor
  of 106 1012.
• Some enzymes act by a lock-and-key mechanism.

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Lock and Key Enzyme Mechanism
Insert Figure 20.11
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Nucleic Acids

• Nucleic Acids serve as the information and
  control centers of the cell.
• There are two types of nucleic acids.
• 1. Deoxyribonucleic acid (DNA)
• 2. Ribonucleic acid (RNA)
• Nucleic acids are polymers composed of
  nucleotides.

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Nucleotides

• Nucleotides are composed of three parts
• 1. A base (a heterocyclic amine)
• 2. A sugar (ribose or deoxyribose)
• 3. A phosphate group (PO4)

base
sugar
Phosphate
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Sugars

• Sugars found in nucleotides are
• Ribose
• In RNA
• Deoxyribose
• In DNA

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Structure of a Nucleotide
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Bases

• Purine Bases
• Adenine (A) (in RNA and DNA)
• Guanine (G) (in RNA and DNA)
• Pyrimidine Bases
• Cytosine ( C) (in RNA and DNA)
• Thymine (T) (in DNA)
• Uracil (U) (in RNA)

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Phosphate
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Nucleic Acid Polymer

• Nucleotides are joined together through the
  phosphate group
• Base O Base O Base O
• Sugar-O-P-O-Sugar-O-P-O-Sugar-O-P-O
• OH OH
  OH

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DNA Structure

• Information stored in DNA and RNA is contained in
  the sequence of bases in the polymer chain.
• Watson and Crick determined that the structure of
  DNA involves two strands of nucleic acid polymer
  arranged in space as a double helix.

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Structure of DNA Double Helix
Insert figure 20.18
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Base Pairing

• Bases on the two strands are bound to each other
  between the strands by hydrogen bonding.
• Adenine is bound to Thymine
• Guanine is bound to Cytosine
• This creates two complementary strands.
• If one strand has a sequence AATCGTACG
• The other strand will be TTAGCATGC

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Protein Synthesis

• The information contained in a portion of a DNA
  molecule through its sequence of nucleotides will
  determine the primary structure of a protein.
• This sequence is called a gene.
• In a process called transcription, the
  information in the DNA is transferred to the
  messenger RNA (mRNA) through base pairing.

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mRNA and Protein Synthesis

• The base sequence carried by the mRNA determines
  the amino acid sequence.
• A set of three consecutive bases in the mRNA
  specifies one amino acid in the chain.
• Transfer RNA (tRNA) carries amino acids carry the
  amino acids to the proper site on the mRNA in the
  ribosomes to build the protein molecules.

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RNA Structure
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Vitamins

• Vitamins are organic compounds required in the
  diet in small amounts for proper functioning.
• Non-polar vitamins are fat-soluble
• A, D, E, and K
• Polar vitamins contain O and N and are termed
  water-soluble
• B complex and C

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Hormones

• Hormones are needed by the body to regulate body
  function.
• Hormones can be synthesized by the body.
• Hormones are produced in the endocrine glands
• Pituitary ovaries
• Thyroid testes
• Parathyroid placenta
• Adrenal pancreas
• Gastrointestinal track.

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Hormones

• Some hormones are proteins or polypeptides like
  insulin.
• Some hormones are steroids like estrogen and
  testosterone.
• Cholesterol is a steroid with no hormonal
  activity, but which is a main component of many
  cells.