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Anatomy & Physiology I
Lecture 1
The Human Body and its Chemistry
What is Anatomy?
• Anatomy – The study of structure
• Subdivisions:
– Gross or macroscopic (e.g., regional, systemic, and
surface anatomy)
– Microscopic (e.g., cytology and histology)
– Developmental (e.g., embryology)
What is Physiology?
• Physiology – the study of the function of the
body
• Subdivisions based on organ systems
(e.g., renal or cardiovascular physiology)
– Often focuses on cellular and molecular level
– Body's abilities depend on chemical reactions in
individual cells
Anatomy & Physiology
• Anatomy and physiology are inseparable
• Function always reflects structure
Keys to Success
• Mastery of anatomical terminology
• Ability to focus at many levels (systemic to
cellular to molecular)
• Study of basic physical principles (e.g., electrical
currents, pressure, and movement)
• Study of basic chemical principles
Figure 1.1 Levels of structural organization.
Atoms
Organelle
Smooth muscle cell
Molecule
Chemical level
Atoms combine to
form molecules.
Cellular level
Cells are made up
of molecules.
Cardiovascular
system
Heart
Blood
vessels
Slide 1
Smooth muscle tissue
Tissue level
Tissues consist of
similar types of cells.
Blood vessel (organ)
Smooth muscle tissue
Connective tissue
Epithelial
tissue
Organ level
Organs are made up of different types
of tissues.
Organismal level
The human organism is made
up of many organ systems.
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Organ system level
Organ systems consist of different
organs that work together closely.
Figure 1.3a The body’s organ systems and their major functions.
Hair
Skin
Nails
Integumentary System
Forms the external body covering,
and protects deeper tissues from injury.
Synthesizes vitamin D, and houses
cutaneous (pain, pressure, etc.)
receptors and sweat and oil glands.
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Figure 1.3b The body’s organ systems and their major functions.
Bones
Joint
Skeletal System
Protects and supports body organs,
and provides a framework the muscles
use to cause movement. Blood cells
are formed within bones. Bones store minerals.
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Figure 1.3c The body’s organ systems and their major functions.
Skeletal
muscles
(c) Muscular System
Allows manipulation of the environment,
locomotion, and facial expression.
Maintains posture, and produces heat.
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Figure 1.3d The body’s organ systems and their major functions.
Brain
Spinal
cord
Nerves
Nervous System
As the fast-acting control system of
the body, it responds to internal and
external changes by activating
appropriate muscles and glands.
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Figure 1.3e The body’s organ systems and their major functions.
Pineal gland
Pituitary
gland
Thyroid
gland
Thymus
Adrenal
gland
Pancreas
Testis
Ovary
Endocrine System
Glands secrete hormones that
regulate processes such as growth,
reproduction, and nutrient use
(metabolism) by body cells.
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Figure 1.3f The body’s organ systems and their major functions.
Heart
Blood
vessels
Cardiovascular System
Blood vessels transport blood,
which carries oxygen, carbon dioxide,
nutrients, wastes, etc. The heart
pumps blood.
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Figure 1.3g The body’s organ systems and their major functions.
Red bone
marrow
Thymus
Lymphatic
vessels
Thoracic
duct
Spleen
Lymph nodes
Lymphatic System/Immunity
Picks up fluid leaked from blood vessels
and returns it to blood. Disposes
of debris in the lymphatic stream.
Houses white blood cells (lymphocytes)
involved in immunity. The immune
response mounts the attack against
foreign substances within the body.
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Figure 1.3h The body’s organ systems and their major functions.
Nasal
cavity
Pharynx
Larynx
Bronchus
Trachea
Lung
Respiratory System
Keeps blood constantly supplied with
oxygen and removes carbon dioxide.
The gaseous exchanges occur through
the walls of the air sacs of the lungs.
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Figure 1.3i The body’s organ systems and their major functions.
Oral cavity
Esophagus
Liver
Stomach
Small
Intestine
Large
Intestine
Rectum
Anus
Digestive System
Breaks down food into absorbable units
that enter the blood for distribution to
body cells. Indigestible foodstuffs are
eliminated as feces.
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Figure 1.3j The body’s organ systems and their major functions.
Kidney
Ureter
Urinary
bladder
Urethra
Urinary System
Eliminates nitrogenous wastes from the
body. Regulates water, electrolyte and
acid-base balance of the blood.
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Figure 1.3k–l The body’s organ systems and their major functions.
Mammary
glands (in
breasts)
Prostate
gland
Ovary
Penis
Testis
Scrotum
Ductus
deferens
Uterus
Vagina
Male Reproductive System
Overall function is production of offspring. Testes
produce sperm and male sex hormone, and male
ducts and glands aid in delivery of sperm to the
female reproductive tract. Ovaries produce eggs
and female sex hormones. The remaining female
structures serve as sites for fertilization and
development of the fetus. Mammary glands of
female breasts produce milk to nourish the newborn.
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Uterine
tube
Female Reproductive System
Overall function is production of offspring. Testes
produce sperm and male sex hormone, and male
ducts and glands aid in delivery of sperm to the
female reproductive tract. Ovaries produce eggs
and female sex hormones. The remaining female
structures serve as sites for fertilization and
development of the fetus. Mammary glands of female
breasts produce milk to nourish the newborn.
Homeostasis is the key to A&P
• Maintenance of relatively stable internal
conditions despite continuous changes in
environment
• A dynamic state of equilibrium
• Maintained by contributions of all organ
systems
Figure 1.4 Interactions among the elements of a homeostatic control system maintain
stable internal conditions.
3 Input: Information
sent along afferent
pathway to control
center.
2 Receptor
detects
change.
Receptor
1 Stimulus
produces
change in
variable.
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Control
Center
Afferent
pathway
Efferent
pathway
BALANCE
Slide 1
4 Output: Information sent
along efferent pathway to
effector.
Effector
5 Response
of effector
feeds back to
reduce the
effect of
stimulus and
returns
variable
to homeostatic
level.
Homeostatic Control
• Negative Feedback mechanisms
• Positive Feedback mechanisms
• Primarily a function of endocrine (BIO202) and
nervous system (BIO201)
Negative Feedback
• Most feedback mechanisms in body
• Response reduces or shuts off original
stimulus
– Variable changes in opposite direction of initial
change
• Example: sweating when you’re hot, shivering
when you’re cold
Positive Feedback
• Response enhances or exaggerates original
stimulus
• May exhibit a cascade or amplifying effect
• Usually controls infrequent events that do not
require continuous adjustment
– contraction during labor or blood clotting
Homeostatic Imbalance
• Disturbance of homeostasis
• Increases risk of disease
– genetic
– age
Terminology of Anatomy
• Always use directional terms as if body is in
anatomical position
• Right and left refer to body being viewed, not
those of observer
Figure 1.7a Regional terms used to designate specific body areas.
Cephalic
Frontal
Orbital
Nasal
Oral
Mental
Cervical
Upper limb
Acromial
Brachial (arm)
Antecubital
Thoracic
Sternal
Axillary
Mammary
Antebrachial
(forearm)
Carpal (wrist)
Abdominal
Umbilical
Manus (hand)
Pollex
Pelvic
Inguinal
(groin)
Palmar
Digital
Lower limb
Coxal (hip)
Femoral (thigh)
Patellar
Pubic (genital)
Crural (leg)
Fibular or peroneal
Pedal (foot)
Tarsal (ankle)
Thorax
Abdomen
Back (Dorsum)
Metatarsal
Digital
Hallux
Anterior/Ventral
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Figure 1.7b Regional terms used to designate specific body areas.
Cephalic
Otic
Occipital (back
of head)
Upper limb
Acromial
Brachial (arm)
Cervical
Olecranal
Antebrachial
(forearm)
Back (dorsal)
Scapular
Vertebral
Lumbar
Manus (hand)
Sacral
Metacarpal
Gluteal
Digital
Perineal (between
anus and external
genitalia)
Lower limb
Femoral (thigh)
Popliteal
Sural (calf)
Fibular or peroneal
Pedal (foot)
Calcaneal
Back (Dorsum)
Plantar
Posterior/Dorsal
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Directional Terms
• Superior (cranial)
– above
• Inferior (caudal)
– below
• Anterior (ventral)
– in front of
Directional Terms
• Posterior (dorsal
– behind
• Medial
– on the inner side
• Lateral
– on the outer side
Directional Terms
• Proximal
– closer
• Distal
– distant or farther
• Superficial
– close to body surface
• Deep
– away from body surface
Two Divisions of the body
• Axial
– Head, neck, and trunk
• Appendicular
– Limbs
Body Planes and Sections
• Body plane
– Flat surface along which body or structure may be
cut for anatomical study
• Sections
– Cuts or sections made along a body plane
Body Planes
• Three most common
• Lie at right angles to each other
– Sagittal plane
– Frontal (coronal) plane
– Transverse (horizontal) plane
Figure 1.8 Planes of the body with corresponding magnetic resonance imaging (MRI) scans.
Frontal plane
Median (midsagittal) plane
Transverse plane
Transverse section
(through torso,
inferior view)
Pancreas
Frontal section
(through torso)
Median section
(midsagittal)
Aorta
Spleen
Arm
Liver Heart
Left and
right
lungs
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Inc.
Liver
Spinal cord
Subcutaneous fat layer
Body wall
Rectum
Intestines
Vertebral column
Body Cavities
• Two sets of internal body cavities
– Closed off to outside environment to provide
protection
• Dorsal body cavity
• Ventral body cavity
Figure 1.9 Dorsal and ventral body cavities and their subdivisions.
Cranial
cavity
Cranial cavity
(contains brain)
Vertebral
cavity
Superior
mediastinum
Dorsal
body
cavity
Thoracic
Pleural
cavity
(contains heartcavity
Pericardial cavity
and lungs)
within
the mediastinum
Vertebral cavity
(contains spinal
cord)
Diaphragm
Abdominal cavity
(contains digestive
viscera)
Abdominopelvic
cavity
Pelvic cavity
(contains urinary bladder,
reproductive organs, and
rectum)
Dorsal body cavity
Ventral body cavity
Lateral view
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Anterior view
Ventral body
cavity
(thoracic and
abdominopelvic
cavities)
And it goes on and on and on...
The Chemistry of Life
• Review
• What is energy?
• What is the conservation of energy?
Forms of Energy
• Chemical energy
– Stored in bonds of chemical substances
• Electrical energy
– Results from movement of charged particles
• Mechanical energy
– Directly involved in moving matter
• Electromagnetic energy
– Travels in waves (visible light, ultraviolet light, and
x-rays)
Energy Conversion
• The chemical and electrical energy produced
by molecules in the cells allows for mechanical
energy of tissues and organs.
Elements of Life
• Four elements make up 96.1% of body mass
•
•
•
•
Carbon (C)
Hydrogen (H)
Oxygen (O)
Nitrogen (N)
Figure 2.1 Two models of the structure of an atom.
Nucleus
Nucleus
Helium atom
Helium atom
2 protons (p+)
2 neutrons (n0)
2 electrons (e–)
2 protons (p+)
2 neutrons (n0)
2 electrons (e–)
Planetary model
Proton
Neutron
Electron
Electron
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Orbital model
Figure 2.2 Atomic structure of the three smallest atoms.
Proton
Neutron
Electron
Hydrogen (H)
(1p+; 0n0; 1e–)
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Helium (He)
(2p+; 2n0; 2e–)
Lithium (Li)
(3p+; 4n0; 3e–)
Atoms to Molecules
• Three types of bonds:
1. Ionic bonds
2. Covalent bonds
3. Hydrogen bonds
Figure 2.6a–b Formation of an ionic bond.
+
Sodium atom (Na)
(11p+; 12n0; 11e–)
Chlorine atom (Cl)
(17p+; 18n0; 17e–)
Sodium gains stability by losing
one electron, and chlorine becomes
stable by gaining one electron.
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Sodium ion (Na+)
—
Chloride ion (Cl–)
Sodium chloride (NaCl)
After electron transfer,
the oppositely charged ions
formed attract each other.
Figure 2.7a Formation of covalent bonds.
Reacting atoms
Resulting molecules
+
or
Structural formula
shows single bonds.
Carbon atom
Hydrogen atoms
Formation of four single covalent bonds:
Carbon shares four electron pairs with
four hydrogen atoms.
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Molecule of methane gas (CH4)
Figure 2.7b Formation of covalent bonds.
Reacting atoms
Resulting molecules
+
Oxygen atom
Oxygen atom
Formation of a double covalent bond: Two
oxygen atoms share two electron pairs.
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or
Structural formula
shows double bond.
Molecule of oxygen gas (O2)
Figure 2.7c Formation of covalent bonds.
Reacting atoms
Resulting molecules
or
+
Nitrogen atom
Nitrogen atom
Formation of a triple covalent bond: Two
nitrogen atoms share three electron pairs.
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Structural formula
shows triple bond.
Molecule of nitrogen gas (N2)
Two Types of Covalent Bonds
1. Nonpolar covalent bonds
– electrons shared equally between atoms
2. Polar covalent bonds
– electrons shared unequally between atoms
Figure 2.8a Carbon dioxide and water molecules have different shapes, as illustrated by molecular models.
Carbon dioxide (CO2) molecules are
linear and symmetrical. They are nonpolar.
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Figure 2.8b Carbon dioxide and water molecules have different shapes, as illustrated by molecular models.
–
+
+
V-shaped water (H2O) molecules have two
poles of charge—a slightly more negative
oxygen end (–) and a slightly more positive
hydrogen end (+).
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Polar vs Non Polar Covalent Bonds
• How different in electronegativity are the
atoms binding
• C – electron neutral
• O, N, P, Cl – electronegative
• H, Na - electropositive
Hydrogen bond
• the weak attraction of a partially positive
hydrogen to an electronegative atom
• produced by the polarity of the molecule
– dipole
• water, sugars, organic acids and bases and
ions can participate
Figure 2.10a Hydrogen bonding between polar water molecules.
+
–
Hydrogen bond
(indicated by
dotted line)
+
–
–
+
–
+
+
+
–
The slightly positive ends (+) of the water molecules
become aligned with the slightly negative ends (–)
of other water molecules.
© 2013 Pearson Education, Inc.
Question?
• How do hydrogen bonds relate to solubility in
water?
Chemical Reactions
• Occur when chemical bonds are formed,
rearranged, or broken
• Four types
– Synthesis (combination) reactions
– Decomposition reactions
– Exchange reactions
Synthesis Reactions
• A + B AB
– Atoms or molecules combine to form larger, more
complex molecule
– Always involve bond formation
• Anabolic
Figure 2.11a Patterns of chemical reactions.
Synthesis reactions
Smaller particles are bonded
together to form larger,
more complex molecules.
Example
Amino acids are joined together to
form a protein molecule.
Amino acid
molecules
Protein
molecule
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Decomposition Reaction
• AB A + B
– Molecule is broken down into smaller molecules
or its constituent atoms
– Reverse of synthesis reactions
– Involve breaking of bonds
• Catabolic
Figure 2.11b Patterns of chemical reactions.
Decomposition reactions
Bonds are broken in larger
molecules, resulting in smaller,
less complex molecules.
Example
Glycogen is broken down to release
glucose units.
Glycogen
Glucose
molecules
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Exchange Reactions
• AB + C AC + B
– Also called displacement reactions
– Involve both synthesis and decomposition
– Bonds are both made and broken
Figure 2.11c Patterns of chemical reactions.
Exchange reactions
Bonds are both made and broken
(also called displacement reactions).
Example
ATP transfers its terminal phosphate
group to glucose to form glucosephosphate.
+
Adenosine triphosphate (ATP)
Glucose
+
Adenosine diphosphate
(ADP)
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Glucosephosphate
Oxidation-Reduction Reactions
• Are decomposition and exchange reactions
– Electron donors lose electrons and are oxidized
– Electron acceptors receive electrons and become
reduced
• “LEO the lion says GER”
• C6H12O6 + 6O2  6CO2 + 6H2O + ATP
Energy in Chemical Reactions
• All chemical reactions are either exergonic or
endergonic
• Exergonic reactions—net release of energy
– Catabolic and oxidative reactions
• Endergonic reactions—net absorption of
energy
– Anabolic reactions
Rates of Reactions
• Chemical equilibrium occurs if neither a
forward nor reverse reaction is dominant
• Affected by:
– Temperature
Rate
– Concentration of reactant
– Catalysts: Rate
• Enzymes are biological catalysts
Rate
Biochemistry
• Study of chemical composition and reactions
of living matter
• The chemical interactions between water,
salts, acids/bases and organic molecules
Water
• Most abundant inorganic compound
– 60%–80% volume of living cells
• Most important inorganic compound
– Due to water’s properties
Properties of Water
• High heat capacity
– Absorbs and releases heat with little temperature
change
– Prevents sudden changes in temperature
• High heat of vaporization
– Evaporation requires large amounts of heat
– Useful cooling mechanism
Water as a solvent
• Polar solvent
– Dissolves and dissociates ionic substances
– Dissolves polar molecules
• Hydrophilic – water loving
• Hydrophobic – water fearing (hating)
Water as a reactant
• Necessary part of hydrolysis and dehydration
synthesis reactions
Salts
• Ionic compounds that dissociate into ions in
water
• Ions (electrolytes) conduct electrical currents in
solution
• Ionic balance vital for homeostasis
• Common salts in body
– NaCl, CaCO3, KCl, CaPO4
Acids and Bases
• Acids are proton donors
– Release H+ into solution
• Bases are proton acceptors
– Take up H+ from solution
– Release OH- into solution
Acids and Bases in the body
• Important acids
– HCl, HC2H3O2 (HAc), and H2CO3
• Important bases
– Bicarbonate ion (HCO3–) and ammonia (NH3)
pH – the measure of acidity
• pH is a mathematical function
pH = - log[H+]
the logarithm is a function of exponents
Linear relationship between y and x
The measure of acidity
• pH = - log[H+]
• It measures the concentration of protons (H+)
in a solution.
• High H+ concentration = low pH (acidic)
• Low H+ concentration = high pH (basic)
H+ vs OH-
Figure 2.13 The pH scale and pH values of representative substances.
Concentration
(moles/liter)
[OH−]
[H+] pH
Examples
1M Sodium
hydroxide (pH=14)
100
10−14
14
10−1
10−13
13
10−2
10−12
12
10−3
10−11
11
10−4
10−10
10
10−5
10−9
9
10−6
10−8
8
10−7
10−7
7 Neutral
10−8
10−6
6
10−9
10−5
5
10−10
10−4
4
10−11
10−3
3
10−12
10−2
2
10−13
10−1
1
100
0
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Increasingly basic
Oven cleaner, lye
(pH=13.5)
Household ammonia
(pH=10.5–11.5)
Household bleach
(pH=9.5)
Egg white (pH=8)
Blood (pH=7.4)
Increasingly acidic
Milk (pH=6.3–6.6)
Black coffee (pH=5)
Wine (pH=2.5–3.5)
Lemon juice; gastric
juice (pH=2)
1M Hydrochloric
acid (pH=0)
Regulation of pH
• pH is regulated by kidneys, lungs, and
chemical buffers
• All biomolecules properties and functions
influenced by pH
Buffers
• Buffers resist abrupt and large swings in pH
– Release hydrogen ions if pH rises
– Bind hydrogen ions if pH falls
• Carbonic acid-bicarbonate system (important
buffer system of blood):
The Biological Environment
•
•
•
•
•
•
water
salts
acids/bases
buffers
pH
temperature
The Biological Players
•
•
•
•
Carbohydrates
Lipids
Proteins
Nucleic Acids
The Primary Reactions
• Dehydration synthesis
• Hydrolysis
• Creating polymers out of monomers
• Breaking down polymers to produce
monomers
Figure 2.14 Dehydration synthesis and hydrolysis.
Dehydration synthesis
Monomers are joined by removal of OH from one monomer
and removal of H from the other at the site of bond formation.
Monomer 1
+
Monomer 2
Monomers linked by covalent bond
Hydrolysis
Monomers are released by the addition of a water molecule, adding OH to one monomer and H to the other.
+
Monomer 1
Monomers linked by covalent bond
Example reactions
Dehydration synthesis of sucrose and its breakdown by hydrolysis
Water is
released
+
Water is
consumed
Glucose
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Fructose
Sucrose
Monomer 2
Carbohydrates
• Sugars and starches
• Polymers
– Contain C, H, and O [(CH20)n]
• Three classes
– Monosaccharides – one sugar
– Disaccharides – two sugars
– Polysaccharides – many sugars
Figure 2.15a Carbohydrate molecules important to the body.
Monosaccharides
Monomers of carbohydrates
Example
Example
Hexose sugars (the hexoses shown here are isomers)
Glucose
Fructose
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Galactose
Pentose sugars
Deoxyribose
Ribose
Figure 2.15b Carbohydrate molecules important to the body.
Disaccharides
Consist of two linked monosaccharides
Example
Sucrose, maltose, and lactose
(these disaccharides are isomers)
Glucose
Fructose
Sucrose
Glucose
Glucose
Maltose
Galactose
Lactose
Glucose
Figure 2.15c Carbohydrate molecules important to the body.
Polysaccharides
Example
Long chains (polymers) of linked monosaccharides
This polysaccharide is a simplified representation of
glycogen, a polysaccharide formed from glucose units.
Glycogen
Functions of Carbohydrates
• Major source of cellular fuel (glucose)
• Structural molecules (DNA/RNA)
• Give function of proteins
• Identification tag for cells and cellular function
– ABO blood type
Lipids
• Insoluble in water
• Main types:
– Triglycerides or neutral fats
– Phospholipids
– Steroids
– Eicosanoids
Triglycerides
• Called fats when solid and oils when liquid
• Composed of three fatty acids bonded to a
glycerol molecule
• Main functions
– Energy storage
– Insulation
– Protection
Figure 2.16a Lipids.
Triglyceride formation
Three fatty acid chains are bound to glycerol by dehydration synthesis.
+
Glycerol
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+
3 fatty acid chains
Triglyceride, or neutral fat
3 water
molecules
Saturation of Fatty Acids
• Saturated fatty acids
– Maximum number of H atoms on C
– Solid animal fats (butter)
• Unsaturated fatty acids
– Reduced number of H atoms on C due to double
bonds
– Plant oils (olive oil)
Phospholipids
• Modified triglycerides:
– Glycerol + two fatty acids and a phosphorus (P) containing group
• “Head” and “tail” regions have different
properties
• Important in cell membrane structure
Figure 2.16b Lipids.
Amphipathicity
“Typical” structure of a phospholipid molecule
Two fatty acid chains and a phosphorus-containing group are attached to the glycerol backbone.
Example
Phosphatidylcholine
Polar “head”
Nonpolar “tail”
(schematic
phospholipid)
Phosphorus-containing
group (polar “head”)
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Glycerol
backbone
2 fatty acid chains
(nonpolar “tail”)
Steroids
• Steroids—interlocking four-ring structure
– Cholesterol, vitamin D, steroid hormones, and bile
salts
• Most important steroid
– Cholesterol
– Important in cell membranes, vitamin D synthesis,
steroid hormones, and bile salts
Figure 2.16c Lipids.
Simplified structure of a steroid
Four interlocking hydrocarbon rings
form a steroid.
Example
Cholesterol (cholesterol is the
basis for all steroids formed in the body)
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Proteins
• Proteins are polymers
• Amino acids (20 types) are the monomers in proteins
– Joined by covalent bonds called peptide bonds
• Unique chemical properties of amino acids
give proteins their unique function
– Contain amine group and acid group
Figure 2.17 Amino acid structures.
Amine
group
Acid
group
Generalized
structure of all
amino acids.
Glycine
is the simplest
amino acid.
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Aspartic acid
(an acidic amino
acid) has an acid
group (—COOH)
in the R group.
Lysine
(a basic amino
acid) has an amine
group (—NH2) in
the R group.
Cysteine
(a basic amino acid)
has a sulfhydryl (—SH)
group in the R group,
which suggests that
this amino acid is likely
to participate in
intramolecular bonding.
Figure 2.18 Amino acids are linked together by peptide bonds.
Dehydration synthesis:
The acid group of one amino
acid is bonded to the amine
group of the next, with loss
of a water molecule.
Peptide
bond
+
Amino acid
Dipeptide
Amino acid
Hydrolysis: Peptide bonds
linking amino acids together
are broken when water is
added to the bond.
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Figure 2.19a Levels of protein structure.
Amino acid
Primary structure:
The sequence of
amino acids forms
the polypeptide chain.
Amino acid
Amino acid
Amino acid
Amino acid
Figure 2.19b Levels of protein structure.
Secondary
structure:
The primary chain
forms spirals
(-helices) and
sheets (-sheets).
-Helix: The primary chain is coiled
to form a spiral structure, which is
stabilized by hydrogen bonds.
-Sheet: The primary chain “zig-zags”
back and forth forming a “pleated”
sheet. Adjacent strands are held
together by hydrogen bonds.
Figure 2.19c Levels of protein structure.
Tertiary structure:
Superimposed on secondary structure.
-Helices and/or -sheets are folded up
to form a compact globular molecule
held together by intramolecular bonds.
Tertiary structure of
prealbumin (transthyretin),
a protein that transports
the thyroid hormone
thyroxine in blood and
cerebrospinal fluid.
Figure 2.19d Levels of protein structure.
Quaternary structure:
Two or more polypeptide chains,
each with its own tertiary structure,
combine to form a functional
protein.
Quaternary structure of a
functional prealbumin
molecule. Two identical
prealbumin subunits join
head to tail to form the
dimer.
Proteins are
• Diverse in size, structure and function
•
•
•
•
•
Structural support
Biological catalysts
Chaperones
Hormones
Cellular signaling
Enzymes
• The biological catalysts
• Regulate and increase speed of chemical
reactions
• Lower the activation energy, increase the
speed of a reaction
Figure 2.20 Enzymes lower the activation energy required for a reaction.
WITHOUT ENZYME
WITH ENZYME
Less activation
energy required
Energy
Energy
Activation
energy
required
Reactants
Reactants
Product
Progress of reaction
Product
Progress of reaction
Figure 2.21 Mechanism of enzyme action.
Substrates (S)
e.g., amino acids
Energy is
absorbed;
bond is
formed.
+
Slide 1
Water is
released.
Product (P)
e.g., dipeptide
Peptide
bond
Active site
Enzyme (E)
Enzyme-substrate
complex (E-S)
1 Substrates bind at active
site, temporarily forming an
enzyme-substrate complex.
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2 The E-S complex
undergoes internal
rearrangements that
form the product.
Enzyme (E)
3 The enzyme releases
the product of the
reaction.
Nucleic Acids
• Deoxyribonucleic acid (DNA) and ribonucleic
acid (RNA)
• Monomer = nucleotide
– Composed of nitrogen base, a pentose sugar, and
a phosphate group
Figure 2.22 Structure of DNA.
Phosphate
Sugar:
Deoxyribose
Base:
Adenine (A)
Thymine (T)
Thymine nucleotide
Adenine nucleotide
Hydrogen
bond
Sugarphosphate
backbone
Deoxyribose
sugar
Phosphate
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
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Sugar
Phosphate
Functions of Nucleic Acids
• DNA
– our genome – the vast collection of our genes that
code the instructions for all cellular processes
• RNA
– protein synthesis (mRNA, tRNA, mRNA)
– protein expression (siRNA, miRNA)
ATP (GTP)
• Adenosine triphosphate
• Chemical energy in glucose captured in this
important molecule
• Directly powers chemical reactions in cells
• Energy form immediately useable by all body cells
Figure 2.23 Structure of ATP (adenosine triphosphate).
High-energy phosphate
bonds can be hydrolyzed
to release energy.
Adenine
Phosphate groups
Ribose
Adenosine
Adenosine monophosphate (AMP)
Adenosine diphosphate (ADP)
Adenosine triphosphate (ATP)
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Function of ATP/GTP
• Phosphorylation
– Terminal phosphates are enzymatically transferred
to and energize other molecules
– Such “primed” molecules perform cellular work
(life processes) using the phosphate bond energy
– Enzymes, called kinases, are the catalysts for
phosphorylating other proteins
Cellular Energy
• The chemical energy of ATP is transferred via
phosphorylation to create mechanical energy
used by the cell for work
Labs for Today
• Lab exercises 1 and 3