Transcript Chapter 24

John E. McMurry • Robert C. Fay
C H E M I S T R Y
Fifth Edition
Chapter 24
Biochemistry
Lecture Notes
Alan D. Earhart
Southeast Community College • Lincoln, NE
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Biochemical Energy
Metabolism: The sum of the many organic reactions
that take place in cells.
C, H, O (food molecules) + O2
CO2 + H2O + energy
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Biochemical Energy
Catabolism: The reaction sequences that break
molecules apart. These reactions generally release
energy.
Anabolism: The reaction sequences that put building
blocks back together to assemble larger molecules.
These reactions generally absorb energy.
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Biochemical Energy
The primary metabolic function of ATP is to drive reactions.
ATP is a “high-energy molecule” and releases a large
amount of energy when it reacts.
Why is it needed?
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Biochemical Energy
This step is important in the breakdown of
dietary carbohydrates:
This reaction is energetically unfavorable.
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Biochemical Energy
Energetically unfavorable reactions can be coupled
with energetically favorable ones:
Glucose + HOPO32ATP + H2O
Glucose + ATP
Glucose 6-phosphate + H2O
DG° = +13.8 kJ/mol
ADP + HOPO32- + H1+
DG° = -30.5 kJ/mol
Glucose 6-phosphate + ADP + H1+
DG° = -16.7 kJ/mol
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Amino Acids and Peptides
Amino Acid: A molecule that contains both a basic
amine group (-NH2) and an acidic carboxyl group
(-CO2H).
Peptide Bond: An amide bond.
Polypeptide: Short chains of up to 100 amino acids.
Amino Acids and Peptides
All 20 common amino acids are a-amino acids:
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Amino Acids and Peptides
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Amino Acids and Peptides
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Amino Acids and Peptides
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Amino Acids and Peptides
Amino Acids and Molecular
Handedness
Amino Acids and Molecular
Handedness
For a molecule to be chiral, the central carbon
must have four different groups attached to it.
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Amino Acids and Molecular
Handedness
Of the 20 common amino acids, 19 are chiral. All 19
of them are one specific enantiomer:
Proteins
Protein: Biological polymers made up of many amino
acid molecules linked together to form a long chain.
Residue: An individual amino acid in a protein.
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Proteins
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Proteins
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Proteins
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Levels of Protein Structure
Primary Structure: This specifies the protein’s amino
acid sequence which determines its overall shape and
function.
Secondary Structure: This specifies how segments of
the protein chain are oriented into regular patterns.
Tertiary Structure: Specifies how the entire protein
chain is coiled and folded into a specific threedimensional shape.
Quaternary Structure: Specifies how several protein
chains can aggregate to form a larger unit.
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Levels of Protein Structure
Primary Structure
How important is the relationship between the sequence
of amino acids to the function of the protein?
The disease sickle-cell anemia is caused by a genetic
defect whereby valine is substituted for glutamic acid at
only one position in a chain of 146 amino acids.
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Levels of Protein Structure
Secondary Structure
Alpha-(a-) Helix
Hydrogen
bond
Levels of Protein Structure
Secondary Structure
Beta-(b-) Pleated Sheet
Levels of Protein Structure
Tertiary Structure
Carbohydrates
Carbohydrate: A large class of organic molecules
commonly called sugars and related to glucose.
-ose suffix since it’s a sugar
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Carbohydrates
Monosaccharide: A simple sugar (carbohydrate) such
as glucose or fructose that can’t be broken down into
smaller molecules by hydrolysis with aqueous acid.
Polysaccharide: A complex sugar (carbohydrate)
such as cellulose or starch that is made up of many
simple sugars linked together.
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Handedness of Carbohydrates
D-form = “right-handed”
L-form = “left-handed”
Cyclic Structures of
Monosaccharides
Some Common Disaccharides
and Polysaccharides
Lactose
Also known as “milk sugar” since it is the major
carbohydrate present in mammalian milk.
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Some Common Disaccharides
and Polysaccharides
Sucrose
Also known as “plain sugar” and is probably the
most common pure organic chemical in the world.
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Some Common Disaccharides
and Polysaccharides
Cellulose
Cellulose is inedible because we do not have the
appropriate enzymes to digest the polysaccharide chain.
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Some Common Disaccharides
and Polysaccharides
Starch
Some Common Disaccharides
and Polysaccharides
Glycogen
Also known as “animal starch” since it serves the same
purpose in animals that starch serves in plants.
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Lipids
Lipid: A naturally occurring organic molecule that
dissolves in a nonpolar organic solvent when a sample
of plant or animal tissue is crushed or ground.
Lipids
Fats and Oils
All fats and oils are triacylglycerols, or triglycerides,
esters of glycerol with three long-chain carboxylic
acids called fatty acids.
Lipids
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Lipids
Steroids
A steroid is a lipid whose structure is based on a
tetracyclic (four-ring) system.
Nucleic Acids
Nucleic Acid: A biological polymer made up of
nucleotide units linked together to form a long chain.
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Nucleic Acids
The sugar in RNA
(ribonucleic acid)
The sugar in DNA
(deoxyribonucleic acid)
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Nucleic Acids
Cyclic Amine Bases in DNA and RNA
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Nucleic Acids
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Nucleic Acids
Base Pairing in DNA: The
Watson-Crick Model
Base pairing
Base Pairing in DNA: The
Watson-Crick Model
Nucleic Acids and Heredity
Chromosome: A threadlike strand of DNA in the
nucleus of a cell. Each chromosome is made up of
several thousand genes.
Gene: A segment of a DNA chain that contains the
instructions necessary to make a specific protein.
Transfer of Genetic Information
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Nucleic Acids and Heredity
Replication
Nucleic Acids and Heredity
Transcription
Nucleic Acids and Heredity
Translation
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