Human Anatomy & Physiology Chapter 2 Biochemistry

Human
Anatomy
& Physiology
SEVENTH EDITION
Elaine N. Marieb
Katja Hoehn
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slides
prepared by Vince Austin,
Bluegrass Technical
and Community College
C H A P T E R
2
Chemistry
Comes Alive
P A R T B

Biochemistry
 Organic compounds
 Contain carbon, are covalently bonded, and are
often large
 Inorganic compounds
 Do not contain carbon
 Water, salts, and many acids and bases

Properties of Water
 High heat capacity – absorbs and releases large
amounts of heat before changing temperature
 High heat of vaporization – changing from a liquid
to a gas requires large amounts of heat
 Polar solvent properties – dissolves ionic
substances, forms hydration layers around large
charged molecules, and serves as the body’s major
transport medium

Properties of Water
 Reactivity – is an important part of hydrolysis and
dehydration synthesis reactions
 Cushioning – resilient cushion around certain body
organs
PLAY InterActive Physiology®:
Fluid, Electrolyte, and Acid/Base Balance: Introduction to Body Fluids

Salts
 Inorganic compounds
 Contain cations other than H+ and anions other
than OH–
 Are electrolytes; they conduct electrical currents

Acids and Bases
 Acids release H+ and are therefore proton donors
HCl  H+ + Cl –
 Bases release OH– and are proton acceptors
NaOH  Na+ + OH–

Acid-Base Concentration (pH)
 Acidic solutions have higher H+ concentration and
therefore a lower pH
 Alkaline solutions have lower H+ concentration
and therefore a higher pH
 Neutral solutions have equal H+ and OH–
concentrations

Acid-Base Concentration (pH)
 Acidic: pH 0–6.99
 Basic: pH 7.01–14
 Neutral: pH 7.00
Figure 2.13

Buffers
 Systems that resist abrupt and large swings in the
pH of body fluids
 Carbonic acid-bicarbonate system
 Carbonic acid dissociates, reversibly releasing
bicarbonate ions and protons
 The chemical equilibrium between carbonic acid
and bicarbonate resists pH changes in the blood
PLAY InterActive Physiology®:
Fluid, Electrolyte, and Acid/Base Balance: Acid/Base Homeostasis

Organic Compounds
 Molecules unique to living systems contain carbon
and hence are organic compounds
 They include:
 Carbohydrates
 Lipids
 Proteins
 Nucleic Acids

Carbohydrates
 Contain carbon, hydrogen, and oxygen
 Their major function is to supply a source of
cellular food
 Examples:
 Monosaccharides or simple sugars
Figure 2.14a

Carbohydrates
 Disaccharides or double sugars
Figure 2.14b
PLAY Disaccharides

Carbohydrates
 Polysaccharides or polymers of simple sugars
Figure 2.14c
PLAY Polysaccharides

Lipids
 Contain C, H, and O, but the proportion of oxygen
in lipids is less than in carbohydrates
 Examples:
 Neutral fats or triglycerides
 Phospholipids
 Steroids
 Eicosanoids
PLAY Fats

Neutral Fats (Triglycerides)
 Composed of three fatty acids bonded to a glycerol
molecule
Figure 2.15a

Other Lipids
 Phospholipids – modified triglycerides with two
fatty acid groups and a phosphorus group
Figure 2.15b

Other Lipids
 Steroids – flat molecules with four interlocking
hydrocarbon rings
 Eicosanoids – 20-carbon fatty acids found in cell
membranes
Figure 2.15c

Representative Lipids Found in the Body
 Neutral fats – found in subcutaneous tissue and
around organs
 Phospholipids – chief component of cell
membranes
 Steroids – cholesterol, bile salts, vitamin D, sex
hormones, and adrenal cortical hormones

Representative Lipids Found in the Body
 Fat-soluble vitamins – vitamins A, E, and K
 Eicosanoids – prostaglandins, leukotrienes, and
thromboxanes
 Lipoproteins – transport fatty acids and cholesterol
in the bloodstream

Amino Acids
 Building blocks of protein, containing an amino
group and a carboxyl group
 Amino group NH2
 Carboxyl groups COOH

Amino Acids
Figure 2.16a–c

Amino Acids
Figure 2.16d, e

Protein
 Macromolecules composed of combinations of 20
types of amino acids bound together with peptide
bonds
Figure 2.17

Protein
bonds
H
R
H
R
C C
Figure 2.17
Amino acid Amino acid
Dehydration
synthesis
Hydrolysis
Peptide bond
H
Dipeptide
N +
H
C
H
O
N
H
C
H
O H2O
H2O
H
N
H
R
C
C
H
O
N
R
C
C
H
O
OH OH OH

Protein
bonds
H
R
N +
H
R
C C
Figure 2.17
H
C
H
O
N
H
C
H
O
OH OH

Protein
bonds
H
R
H
R
C C
Figure 2.17
Dehydration
synthesis
N +
H
C
H
O
N
H
C
H
O H2O
OH OH

Protein
bonds
H
R
H
R
C C
Figure 2.17
Dehydration
synthesis
Peptide bond
H
Dipeptide
N +
H
C
H
O
N
H
C
H
O H2O
H
N
H
R
C
C
H
O
N
R
C
C
H
O
OH OH OH

Protein
bonds
Figure 2.17
Peptide bond
H
Dipeptide
H
N
H
R
C
C
H
O
N
R
C
C
H
O
OH

Protein
bonds
Figure 2.17
Hydrolysis
Peptide bond
H
Dipeptide
H2O
H
N
H
R
C
C
H
O
N
R
C
C
H
O
OH

Protein
bonds
H
R
H
R
C C
Figure 2.17
Hydrolysis
Peptide bond
H
Dipeptide
N +
H
C
H
O
N
H
C
H
O
H2O
H
N
H
R
C
C
H
O
N
R
C
C
H
O
OH OH OH

Structural Levels of Proteins
 Primary – amino acid sequence
 Secondary – alpha helices or beta pleated sheets
PLAY Chemistry of Life:
Introduction to Protein Structure
Proteins: Primary Structure
Proteins: Secondary Structure

 Tertiary – superimposed folding of secondary
structures
 Quaternary – polypeptide chains linked together in
a specific manner
Proteins: Tertiary Structure
Proteins: Quaternary Structure

Figure 2.18a–c

Figure 2.18b,d,e

Fibrous and Globular Proteins
 Fibrous proteins
 Extended and strand-like proteins
 Examples: keratin, elastin, collagen, and certain
contractile fibers

Fibrous and Globular Proteins
 Globular proteins
 Compact, spherical proteins with tertiary and
quaternary structures
 Examples: antibodies, hormones, and enzymes

Protein Denuaturation
 Reversible unfolding of proteins due to drops in
pH and/or increased temperature
Figure 2.19a

Protein Denuaturation
 Irreversibly denatured proteins cannot refold and
are formed by extreme pH or temperature changes
Figure 2.19b

Molecular Chaperones (Chaperonins)
 Help other proteins to achieve their functional
three-dimensional shape
 Maintain folding integrity
 Assist in translocation of proteins across
membranes
 Promote the breakdown of damaged or denatured
proteins

Characteristics of Enzymes
 Most are globular proteins that act as biological
catalysts
 Holoenzymes consist of an apoenzyme (protein)
and a cofactor (usually an ion)
 Enzymes are chemically specific

 Frequently named for the type of reaction they
catalyze
 Enzyme names usually end in -ase
 Lower activation energy

Figure 2.20

Mechanism of Enzyme Action
 Enzyme binds with substrate
 Product is formed at a lower activation energy
 Product is released
PLAY How Enzymes Work

Active site
Amino acids
Enzyme (E)
Enzyme-substrate
complex (E-S)
Substrates (S)
H2O
Internal rearrangements
leading to catalysis
+
Free enzyme (E)
Peptide bond
Dipeptide product (P)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 2.21

Active site
Amino acids
Enzyme (E)
Enzyme-substrate
complex (E-S)
Substrates (S)
H2O
+

Active site
Amino acids
Enzyme (E)
Enzyme-substrate
complex (E-S)
Substrates (S)
H2O
Internal rearrangements
leading to catalysis
+

Nucleic Acids
 Composed of carbon, oxygen, hydrogen, nitrogen,
and phosphorus
 Their structural unit, the nucleotide, is composed
of N-containing base, a pentose sugar, and a
phosphate group

Nucleic Acids
 Five nitrogen bases contribute to nucleotide
structure – adenine (A), guanine (G), cytosine (C),
thymine (T), and uracil (U)
 Two major classes – DNA and RNA

Deoxyribonucleic Acid (DNA)
 Double-stranded helical molecule found in the
nucleus of the cell
 Replicates itself before the cell divides, ensuring
genetic continuity
 Provides instructions for protein synthesis

Structure of DNA
Figure 2.22a

Structure of DNA
Figure 2.22b

Ribonucleic Acid (RNA)
 Single-stranded molecule found in both the
nucleus and the cytoplasm of a cell
 Uses the nitrogenous base uracil instead of
thymine
 Three varieties of RNA: messenger RNA, transfer
RNA, and ribosomal RNA

Adenosine Triphosphate (ATP)
 Source of immediately usable energy for the cell
 Adenine-containing RNA nucleotide with three
phosphate groups

Adenosine Triphosphate (ATP)
Figure 2.23

P Pi
Solute Solute transported
(a) Transport work
Contracted smooth
muscle cell
(b) Mechanical work
X P X
Y
Pi
Product made
Relaxed smooth
muscle cell
Y
+
Reactants
Membrane
protein
ATP
(c) Chemical work
ADP
+
Pi

P
Solute
Membrane
protein
ATP
(a) Transport work

P Pi
Solute Solute transported
Membrane
protein
ATP
(a) Transport work
ADP
+
Pi

Relaxed smooth
muscle cell
ATP
(b) Mechanical work

Contracted smooth
muscle cell
Relaxed smooth
muscle cell
ATP
(b) Mechanical work
ADP
+
Pi

X P
+ Y
Reactants
ATP
(c) Chemical work

X P X
Y
Y
+
Pi
Reactants Product made
ATP
(c) Chemical work
ADP
+
Pi

Human Anatomy & Physiology Chapter 2 Biochemistry

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