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Biochemistry

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There are four main classes of biopolymers lipids, proteins, carbohydrates, and nucleic acids * Tro: Chemistry: A Molecular Approach, 2/e – PowerPoint PPT presentation

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Title: Biochemistry


1
Biochemistry
  • Biochemistry is the study of the chemistry of
    living organisms
  • Much of biochemistry deals with the large,
    complex molecules necessary for life as we know
    it
  • However, most of these complex molecules are
    actually made of smaller, simpler units they
    are biopolymers
  • There are four main classes of biopolymers
    lipids, proteins, carbohydrates, and nucleic acids

Tro Chemistry A Molecular Approach, 2/e
2
Lipids
  • Lipids are a family of compounds that are
    generally insoluble in water (ie. Non-polar).
  • Classes of Lipids
  • Waxes fatty acid and long chain alcohol (ester)
  • Fats Oils glycerol three fatty acids
  • Phospholipids glycerol 2 fatty acids
    phosphate an amino alcohol
  • Sphingolipids fatty acid sphingosine
    phosphate an amino alcohol
  • Glycolipids fatty acid glycerol or
    sphingosine one monosaccharide.
  • Steroids a fused ring structure of three
    cyclohexanes and one cyclopentane.

3
Fatty Acids
  • Long chain carboxylic acids.
  • 12 18 Carbons are the most common.
  • Stearic acid is most often found in animal fat.

CH3CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH
2COOH
And it can also be represented like this
4
Fatty Acids
  • Can be saturated all C-C single bonds.
  • Can be mono-unsaturated one C-C double bond.
  • Ex) Oleic Acid found in olives and corn.
  • CH3(CH2)7CHCH(CH2)7COOH
  • Can be poly-unsaturated more than one C-C
    double bond.
  • Ex) Linoleic Acid found in soybeans and
    sunflowers.
  • CH3(CH2)4CHCHCH2CHCH(CH2)4COOH
  • In the Unsaturated acids, the cis isomer is
    usually found.

5
Physical Properties of Fats and Oils
  • The repeating zigzag shape of saturated fatty
    acids found in fats allows them to fit close
    together leading to strong attractions. As a
    result, a fat is solid at room temperature.
  • The unsaturated fatty acids found in oils do not
    stack together because of the double bonds. As a
    result, an oil is a liquid at room temperature.

6
Fats and Oils
  • Fats and oils are the most common lipids.
  • Often called triglycerides because they are a
    tri-ester of glycerol and three fatty acids.
  • Tristearin consists of three stearic acid
    molecules reacting with glycerol.

7
Reaction to Produce a Fat or Oil
3 H2O
8
Steroids and Cholesterol
  • Steroids are any compounds containing the steroid
    nucleus (Pictured at right).
  • Cholesterol is the most important and abundant
    steroid in the body.
  • You cannot exist without this substance!
  • The sex hormones and the adrenocortical hormones
    depend on cholesterol for their synthesis.

9
Cholesterol and Hormones
Cholesterol, Estrogen, and Testosterone
10
Carbohydrates
  • Simple Sugars have the formula Cn(H2O)n and were
    once thought to be hydrates of Carbon.
  • The Carbon cycle.
  • ___________
  • 6CO2 6H2O energy ? C6H12O6 6O2
    _____________

11
Types of Carbohydrates
  • Monosaccharides do not hydrolyze into smaller
    units.
  • Disaccharides consist of two mono units joined
    together these will hydrolyze.
  • Polysaccharides consist of many mono units and
    are sometimes called complex carbohydrates.

12
Monosaccharides
  • Have between three and eight C atoms.
  • Number of Cs determines whether it is a triose
    (3), tetrose (4), pentose (5), hexose (6), etc.
  • All have at least two OH groups and the term
    polyhydroxy- is sometimes used.
  • Will also have either an aldehyde or ketone
    group.
  • Aldehyde aldose and ketone ketose.
  • Molecules are written with the C backbone in a
    vertical direction.

13
Monosaccharides
  • Ketose or Aldose?
  • How many chiral carbons?

14
Monosaccharides and Chirality
  • Large monosaccharides have several chiral Cs.
  • If the lowest chiral C has the OH group on the
    left, then it is called the L isomer. If it is
    on the right, then it is called the D isomer.
  • Hint Cs with double to the O are not chiral and
    the -CH2OH groups are also not chiral.

15
Glucose
  • How many chiral carbons?
  • Is this the D or L isomer?
  • Note D-glucose is oxidized in the body to
    produce energy and L-glucose cannot be oxidized.

16
Cyclic Structure
  • In solution, glucose and other mono-saccharides
    become cyclic.

17
Disaccharides
  • Composed of two mono units.
  • Some common ones are
  • Sucrose Glucose Fructose
  • Lactose (Milk sugar) glucose galactose
  • Maltose glucose glucose
  • In the presence of water and an acid catalyst,
    these linked molecules will split apart back into
    their mono units.

18
Sucrose
19
Polysaccharides
  • This is essentially a polymer of glucose units
    (usually).
  • Plant Starch exists in two forms Amylose and
    Amylopectin.
  • Amylose is a long,continuous chain of glucose
    molecules. Typically has 250 4000 units.
  • Amylopectin is a branched chain of glucose
    molecules. Branches are about every 25 units.

20
Polysaccharides
  • Animal Starch is also called ___________. This
    is essentially a branched chain as well.
  • Branches are about every 10 15 units.
  • ____________, found in cell walls of plants and
    animals, is also a long chain of glucose units
    much like amylose.

21
Polysaccharides
  • The linkage between each unit in cellulose is
    different (b linkage) and is resistant to
    hydrolysis.
  • Humans do not possess the enzymes to break this
    material down for energy as some animals do.
  • We often refer to this material in our diet as
    fiber.

22
Amino Acids and Proteins
23
The Amino Acids
  • Are the building blocks of all proteins.
  • Twenty different versions of these.
  • All contain the carb. acid and amine functional
    groups.
  • Center C is called the alpha Carbon and it is
    chiral (except in Glycine)
  • Abbreviated by three letter designations.

24
Amino Acids
  • The R groups can be non-polar, polar, acidic, or
    basic.

Serine
Alanine
Non-polar R group
Acidic R Group
25
The Peptide Bond
  • Amino acids link together by the reaction of a
    carboxylic acid on one with the amine of another.
  • The linkage between the two is called a peptide
    bond.

26
Peptide Formation
  • Reaction to form peptide bond between any two
    amino acids is a condensation type

27
Primary Structure
  • Chains of 3 50 amino acids are called
    polypeptides.
  • When more than 50 amino acids are joined, we
    usually call it a protein.
  • The specific sequence of amino acids in a protein
    is called the primary structure.
  • Our DNA codes for only a limited number of
    specific sequences for making proteins.
  • Approximately 100,000 different proteins found in
    humans.

28
Secondary Structure
  • This refers to how the amino acids along the
    polypeptide are arranged in space.
  • The three most common types are
  • Alpha Helix - which is a corkscrew shape of the
    chain that results from Hydrogen bonding between
    every fourth amino acid. All of the R groups
    then are pointed outward.
  • Beta-Pleated Sheet rows of amino acids are held
    flat with HB keeping them rigid.
  • Triple Helix is three peptide chains woven
    together like a braid. HB is also a powerful
    force that holds this together.

29
Alpha Helix Beta-Pleated Sheet
30
Tertiary Structure
  • This is the overall 3D shape of the protein.
  • The types and interactions of the R groups are
    important in this area.
  • Globular proteins, like hemoglobin and insulin,
    have a very compact and round shape. The
    non-polar R groups point inward and the polar R
    groups point outward and this makes these
    proteins soluble in water.
  • Fibrous proteins, like keratin (hair, skin),
    consist of long, thin, fibrous shapes.
    Cross-linking is an important aspect and
    determines whether you have curly or straight
    hair.

31
Tertiary Structure
32
Overview of Protein Structures
33
Albumin
34
Lysozyme
35
Nucleic Acids
  • Basic structure is a polymer of four different
    bases.
  • Each nucleotide consists of three parts a sugar,
    a base, and a phosphate group.

36
Nucleotide Structure
  • Each nucleotide has three parts a cyclic
    pentose, a phosphate group, and an organic
    aromatic base
  • The pentoses are the central backbone of the
    nucleotide
  • The pentose is attached to the organic base at C1
    and to the phosphate group at C5
  • The phosphate groups then link to each other to
    form a polymer

37
DNA and RNA
  • Deoxyribonucleic Acid is found primarily in the
    nucleus of the cell.
  • Ribonucleic Acid is found throughout the cell.
  • The sugar molecule Ribose differs by a single
    oxygen atom.

38
Bases
  • In DNA, the four cyclic bases are Adenine,
    Guanine, Cytosine, and Thymine. In RNA, Thymine
    is replaced by Uracil.

39
Base Pairing in DNA
40
Base Pairing in DNA
  • The bases in nucleic acids are complementary
    they precisely pair with another base.
  • Adenine pairs with Thymine via two hydrogen bonds
  • Guanine pairs with Cytosine via three hydrogen
    bonds

41
Linking Nucleotides
42
Linking Nucleotides
43
Genetic Structure
  • Each sequence of three nucleotides is called a
    codon
  • A codon codes for one amino acid
  • AGT Serine
  • ACC Threonine
  • This is universal for all living things!

44
DNA Double Helix
45
DNA Double Helix
  • Base pairing generates the helical structure
  • In DNA, the complementary bases hold strands
    together by H-bonding
  • allow replication of strand

46
DNA Replication
47
Protein Synthesis
  • Transcription ? translation
  • In nucleus, DNA strand at gene separates and a
    complementary copy of the gene is made in RNA
  • messenger RNA mRNA
  • The mRNA travels into the cytoplasm where it
    links with a ribosome
  • At the ribosome, each codon on the RNA codes for
    a single amino acid, and these are joined
    together to form the polypeptide chain

Tro Chemistry A Molecular Approach, 2/e
48
Protein Synthesis
Tro Chemistry A Molecular Approach, 2/e
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