Chapter 2
Chemical Level of Organization
Chapter 3
DNA and RNA
Diffusion and Osmosis
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Atoms, Ions, and Molecules: Matter, Atoms,
Elements, and the Periodic Table
• Human body is composed of matter
– Three forms:
• solid (e.g., bone)
• liquid (e.g., blood)
• gas (e.g., oxygen)
• Matter is composed of atoms
– Atom, smallest particle that exhibits the chemical properties of
an element – arranged in the periodic chart
Figure 2.1a
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IIA
IIIA
1
IVA
VA
VIA
VIIA
Increasing electronegativity
H
2
He
1.008
3
4
Li
Be
6.941
9.012
11
12
Na
Mg
22.99
24.31
19
VIIIA
5
1
Atomic number
H
Element symbol
B
20
K
Ca
39.10
40.08
22
23
24
25
Fe
27
Si
17
S
Cl
30.97
2.07
35.45
33
34
35
36
Br
Kr
79.90
83.80
53
54
28.09
Zn
Ga
63.55
65.38
69.72
46
47
48
49
50
51
52
41
42
43
44
45
Ge As
72.64
18
Ar
39.95
Cu
54.94
32
Ne
20.18
16
Ni
Mn
52.00
F
19.00
10
P
58.69
Cr
31
9
15
58.93
V
50.94
30
O
15.99
Co
Ti
47.87
40
Al
N
14.01
29
44.96
39
14
4.003
8
7
28
Sc
55.85
13
26.98
26
21
C
12.01
10.81
Atomic mass number
1.008
6
74.92
Se
78.96
37
38
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
85.47
87.62
88.91
91.22
92.91
95.94
98.00
101.1
102.9
106.4
107.9
112.4
114.8
118.7
121.8
127.6
126.9
131.3
55
56
57
72
73
74
75
76
77
78
79
80
81
82
83
84
Cs
Ba
La
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
132.9
137.3
138.9
178.5
180.9
183.8
186.2
190.2
192.2
195.1
197.0
200.6
204.4
207.2
209.0
209.0
210.0
222.0
87
88
89
104
105
106
107
108
109
110
111
112
112
114
115
116
117
118
Fr
Ra
Ac
Rf
Db
Sg
Bh
Hs
Mt
Ds
Rg Uub Uut
223.0
226.0
227.0
267.0
268.0
271.0
272.0
270.0
276.0
281.0
60
61
62
63
64
274
85
At
86
Rn
Uuq Uup Uuh Uus Uuo
277
277
289.0
288.0
293.0
292.0
294.0
65
66
67
68
69
70
71
58
59
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
140.1
140.9
144.2
145.0
150.4
152.0
157.3
158.9
162.5
164.9
167.3
168.9
173.0
175.0
90
91
92
103
Th
Pa
232.0
231.0
U
238.0
93
94
Np
Pu
237.0
244.0
95
96
Am
Cm
243.0
247.0
97
Bk
247.0
98
99
100
101
102
Cf
Es
Fm
Md
No
251.0
252.0
257.0
258.0
259.0
Lr
262.0
Increasing electronegaativity
IA
Figure 2.1b
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Most Common Elements of the Human Body
Major elements
(collectively compose more than 98% of body weight)
Symbol
(b)
Lesser elements
(collectively compose less than 1% of body weight)
% Body weight
Symbol
% Body weight
O
Oxygen
65.0
S
Sulfur
0.25
C
Carbon
18.0
K
Potassium
0.20
H
Hydrogen
10.0
Na
Sodium
0.15
N
Nitrogen
3.0
Cl
Chlorine
0.15
Ca
Calcium
1.5
Mg
Magnesium
0.05
P
Phosphorus
1.0
Fe
Iron
0.006
Atoms, Ions, and Molecules: Matter, Atoms,
Elements, and the Periodic Table
The components of an atom
• Atoms composed of three subatomic particles:
– protons
• mass of one atomic mass unit (amu)
• positive charge of one (+1)
– neutrons
• mass of one amu
• no charge
– electrons
• 1/1800th mass of a proton or neutron
• negative charge of one (-1)
• located at varying distance from the nucleus in regions called orbitals
Atoms, Ions, and Molecules: Matter, Atoms,
Elements, and the Periodic Table
The periodic table
• Elements differ in number of subatomic particles
• Periodic table displays:
– chemical symbol
• unique to each element
• usually identified by first letter, or first letter plus an additional letter
– C is carbon
- atomic number
number of protons in an atom of the element
located above symbol name
elements arranged by anatomic number within rows
- average atomic mass
mass of both protons and neutrons
shown below the element’s symbol on the table
Atoms, Ions, and Molecules: Matter, Atoms,
Elements, and the Periodic Table
Diagramming Atomic Structures
• An atom has shells of electrons
surrounding the nucleus
– Each shell with a given energy
level
– Each shell holding a limited
number of electrons
– Innermost shell two electrons,
second shell up to eight
– Shells close to the nucleus: must be
filled first
Nucleus:
Figure 2.2b
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Shell model
Energy
shell
8 protons
8 neutrons
8 electrons
(b)
Proton (+)
Neutron (no charge)
Electron shells:
Electron (–)
Atoms, Ions, and Molecules: Isotopes
• Isotopes are different atoms of the same element
–
–
–
–
Have same number of protons and electrons
Have different numbers of neutrons
Exhibit essentially identical chemical characteristics
One usually predominant
• Carbon exists in three isotopes:
– carbon-12, with 6 neutrons
• most prevalent type
– carbon-13, with 7 neutrons
– carbon-14 , with 8 neutrons
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Carbon–12
Carbon–13
Carbon–14
6 protons
6 neutrons
6 electrons
6 protons
7 neutrons
6 electrons
6 protons
8 neutrons
6 electrons
Figure 2.3
Atoms, Ions, and Molecules: Isotopes
Clinical View: Medical Imaging of the Thyroid Gland
Using Iodine Radioisotopes
– Radioisotopes- Are unstable because they contain excess neutrons
– Lose nuclear components in the form of high energy radiation (alpha
particles, beta particles, gamma rays)
• introduced into the body during medical procedures
– Used by cells in a similar manner to nonradioisotopes
– Can trace products of metabolic reactions that use these elements
– Thyroid gland darker in areas where less radioactive iodine
taken up
– Can help locate a nodule
– Biological half-life, the time required for half of the radioactive material
from a test to be eliminated from the body
Atoms, Ions, and Molecules: Chemical
Stability and the Octet Rule
• Periodic table organized into columns based on
number of electrons in outer shell (valence shell)
– Column one, with hydrogen, lithium, sodium, potassium
• all with one electron in their outer shell
– Each consecutive column with one additional electron in outer shell
– Elements in column VIIA with a full valence shell
• results in chemical stability
• helium, neon, etc., chemically inert (noble gases)
Atoms, Ions, and Molecules: Chemical
Stability and the Octet Rule
• Elements tend to lose, gain, or share electrons to
obtain complete outer shells with eight electrons
– Known as the octet rule
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Number of valence electrons
1
IA
Figure 2.4
2
IIA
3
IIIA
4
IVA
5
VA
6
VIA
7
VIIA
8
VIIIA
He
H
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
Ions and Ionic Compounds
• Chemical compounds
– Stable associations between two or more elements combined in a
fixed ratio
– Classified as ionic or molecular
• Ionic compounds are structures composed of ions
held together in a lattice of ionic bonds
• Ions
– positive or a negative charge
– Are produced from the loss or gain of an electron or electrons
– Are used very commonly in the body with significant physiological
functions
• e.g., Na+ for electrical signals in neurons
• e.g., Ca2+ for blood clotting and muscle contraction
• e.g., Cl- in stomach acid, and many more
Figure 2.5
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Na
11p
(a) Sodium atom (Na)
+
Cl
17p
(b) Chlorine atom (Cl)
=
Na+
Cl–
11p
17p
(c) Sodium ion (Na+)
Chloride ion (Cl–)
Cl–
Na+
Cl–
Na+
Cl–
Na+
Cl–
Na+
Cl–
(d) Lattice salt crystal of NaCl
Common
Ions in the
Human body
and Their
Physiological
Significance
(Table 2.1a)
Common
Ions in the
Human body
and Their
Physiological
Significance
(Table 2.1b)
Covalent Bonding, Molecules, and
Molecular Compounds
• Sharing of electrons between atoms results in a
covalently bonded molecule
• Most molecules are composed of two or more different
elements
– Termed molecular compounds
• examples include carbon dioxide (CO2) but not molecular oxygen (O2)
• Molecular formula
– Shows the chemical constituents and their ratios in a molecule
• Structural formula
– Shows number and types of atoms
– Also shows their arrangements within the molecule
– Provides a mean for differentiating isomers
• molecules with the same number and kind of elements arranged differently in
space
Covalent Bonding, Molecules, and Molecular
Compounds: Molecular and Structural Formulas
• Glucose versus galactose versus fructose
– All with the same molecular formula, with 6 carbon, 12 hydrogen, and
6 carbon
– Atoms arranged differently
• Isomers may have different chemical properties
Figure 2.6
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Molecular formula
Glucose
Galactose
Fructose
(C6H12O6)
(C6H12O6)
(C6H12O6)
6 CH2OH
5C
H
6 CH2OH
O
H
HO
H
Structural formula
4C
OH
H
H
HO
(a)
5C
5
O
4C
C1
OH
H
H
OH
3C
C2
3C
C2
H
OH
H
OH
(b)
HOCH2
O
OH
H
C1
4C
C1
H
OH
H
3C
OH
(c)
HO
C2
H
CH2OH
Covalent Bonding, Molecules, and Molecular
Compounds: Covalent Bonds
• A covalent bond is formed when atoms share
electrons
– Occurs when both atoms require electrons
– Occurs with atoms that have four to seven electrons in their outer shell
• Four elements of the human body form covalent
bonds most commonly:
–
–
–
–
oxygen (O)
carbon (C)
hydrogen (H)
nitrogen (N)
Covalent Bonding, Molecules, and Molecular
Compounds: Covalent Bonds
The number of bonds an atom can form
• Simplest covalent bond formation occurs between
two hydrogen atoms
– Each sharing its single electron
• Oxygen needs two electrons to complete outer shell
– Forms two covalent bonds
• Nitrogen forms three bonds
• Carbon forms four bonds
Molecular Structure of Water and the
Properties of Water: Molecular Structure
• Water
Figure 2.12
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Water (H2O)
+
+
–
H
H
+
+
–
–
O
+
–
+
–
–
Hydrogen bonds form
between water molecules.
Water is a polar molecule due
to unequal sharing of electrons.
(a)
Hydrogen
bonds
(b)
– Composes two-thirds of the
human body by weight
– Polar molecule composed of
one oxygen atom bonded to
two hydrogen atoms
– Oxygen atom with two
partial negative charges
– Hydrogen with a single
positive charge
– Can form four hydrogen
bonds with adjacent
molecules
• central to water’s properties
Phases of water
• Water present in three phases, depending on
temperature:
– gas (water vapor)
– liquid (water)
• almost all water in the body in this phase
– solid (ice)
• Functions of liquid water:
– transports
• substances dissolved in water moved throughout the body
– lubricates
• decreases friction between body structures (e.g., serous fluid)
– cushions
• absorbs sudden force of body movements (e.g., cerebrospinal fluid)
– excretes wastes
• unwanted substances dissolved in water and eliminated
Molecular Structure of Water and the
Properties of Water: Properties
Cohesion, surface tension, and adhesion
• Cohesion
– The attraction between water molecules due to hydrogen bonding
• Surface tension
– The inward pulling of cohesive forces at the surface of water
– Causes moist sacs of air in the lungs to tend to collapse
• surfactant (mixture of lipids and proteins) helps prevent this
• Adhesion
– The attraction between water molecules and a substance other
than water
Figure 2.4 6
Molecular Structure of Water and the
Properties of Water: The Universal Solvent
• Water is the solvent of the body
• Substances that dissolve in water are called solutes
• Water called the universal solvent because most
substances dissolve in it
– The chemical properties of a substance determine whether it will
dissolve
• Nonpolar molecules do not dissolve within water
– Substances termed hydrophobic, “water-fearing”
– Cohesive water molecule “force out” nonpolar molecules
– Hydrophobic substances require carrier proteins to be transported
within the blood
• fats, cholesterol unable to dissolve within water
Acidic and Basic Solutions, pH, and Buffers:
pH, Neutralization, and the Action of Buffers
• The pH is a measure of H+
– The relative amount of H+ in a solution
– Expressed as a number between 0 and 14
• greater H+ = lower pH value
• The pH of plain water is 7
Solutions with equal concentrations of H+ and OHAre neutral
Have a pH of 7
Solutions with greater H+ than OHAre acidic
Have a pH < 7 taste sour
Solutions with greater OH- than H+
Are basic (alkaline)
Have a pH >7 taste bitter
Figure 2.15
Copyright © The McGraw–Hill Companies, Inc. Permission required for reproduction or display.
H+ Concentration
H+
H+
H+
0
10–1
1
Hydrochloric acid (HCl): 1
10–2
2
Lemon juice, stomach acid: 2–3
[H+]
10–3
3
H+
H+
H+
Decreasing
pH
10–4
H+
4
10–5
5
H+
H+
H+
<
OH–
Decreasing
[H+]
Increasing
pH
H+
H+
H+
H+
>
OH–
Increasing
H+
H+
H+
H+
H+
Examples
100
H+
H+
pH Value
Wine: 2.4–3.5
Grapefruit juice: 3
Tomato juice: 4.7
Urine: 6
Milk, saliva: 6.3–6.6
Acidic
10–6
6
Neutral
10–7
7
Basic
10–8
8
10–9
9
10–10
10
Antacid: 10.5
10–11
11
Household ammonia: 10.5–11
10–12
12
Household bleach: 12
10–13
13
10–14
14
Pure water: 7
Human blood: 7.4
Seawater: 8
Sodium hydroxide (NaOH): 14
Acidic and Basic Solutions, pH, and Buffers:
pH, Neutralization, and the Action of Buffers
• Neutralization occurs when an acidic or basic
solution is returned to neutral
– Acids neutralized by adding base
• e.g., medications to neutralize stomach acid containing base
– Bases neutralized by adding acid
• Buffers help prevent pH changes if excess acid or
base is added
– Act to accept H+ from excess acid or donate H+ to neutralize base
• carbonic acid (weak acid) and bicarbonate (weak base) buffer blood pH
• both help maintain pH in a critical range
Biological Macromolecules:
General Characteristics
• Organic molecules, molecules that contain carbon
– Most are a component of living organisms
– Biological macromolecules (biomolecules) are a subset
• Inorganic molecules, all other molecules
• Four classes of biomolecules in living systems:
–
–
–
–
lipids
carbohydrates
nucleic acids
proteins
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Functional
Group
Structural
Formula
Properties
Structural Diagram of Example Molecule
Representative
Molecules
CH2OH
Hydroxyl
• Polar
• Forms hydrogen bonds
• Increases molecules’
solubility in water
OH
C
• Carbohydrates
• Proteins
• Nucleic acids
• Lipids
O
H
C
Figure 2.17
H
H
C
OH
H
C
C
OH
HO
H
OH
Glucose
• Polar
• Forms hydrogen bonds
• Increases molecules’
solubility in water
O
Carbonyl
C
• Carbohydrates
• Nucleic acids
H
H
O
C
C
H
H
Acetaldehyde
• Polar
• Forms hydrogen bonds
• Increases molecules’
solubility in water
• Acts as an acid
O
Carboxyl
(carboxylic acid)
C
OH
• Polar
• Forms hydrogen bonds
• Increases molecules’
solubility i n water
• Acts as a base
H
N
Amine
H
H H H H H H H H H H H H H H H H H
O
• Proteins
• Lipids
C
HO
C C C C C C C C C C C C C C C C C H
H H H H H H H H H H H H H H H H H
Fatty acid
H
• Proteins
• Nucleic acids
N
H
H
O
C
C
OH
CH3
Alanine
NH2
N
C
C
N
HC
O
Phosphate
O
O–
P
O–
• Polar
• Forms hydrogen bonds
• Increases molecules’
solubility in water
• Forms phosphodiester
bonds
• Acts as an acid
(shown here with
hydrogens released)
N
CH
C
N
• Nucleic acids
• Phospholipids
• ATP
O
H2C
O
P
O
P
O–
O
O
O–
P
O–
C
C
H
O
O
C
C
OH
OH
H
Adenosine triphosphate (ATP)
NH2
Sulfhydryl
S
H
• Forms disulfide bridge
• Proteins
H
O
C
C
CH2
S
H
Cysteine
OH
O–
Biological Macromolecules:
General Characteristics
Polymers
• Molecules made up for repeating subunits, termed
monomers
– Monomers identical or similar in chemical structure
– Examples are carbohydrates, nucleic acids, proteins
• carbohydrates with sugar monomers
• nucleic acids with nucleotide monomers
• proteins with amino acid monomers
Biological Macromolecules:
General Characteristics
Copyright © The McGraw–Hill Companies, Inc. Permission required for reproduction or display.
Dehydration
• Dehydration synthesis (condensation)
Anabolic reaction
–
–
–
–
Occurs during the synthesis of biomolecules
One subunit looses an –H
Other subunit loses an –OH
New covalent bond formed and water produced
H2O
Synthesis
(a)
• Hydrolysis reaction
Catabolic reaction
Hydrolysis
H2O
– Occurs during the breakdown of biomolecules
– An –H added to one subunit
– An –OH added to another subunit
Digestion
(b)
Biological Macromolecules: Lipids
• Lipids – made from fatty acids
– Functions: energy storage, insulation, and cushioning
– Are in cell membranes and hormones
– Occur in four primary classes:
• Triglycerides- energy storage
–
–
–
–
Most common form of lipid in living things
Used for long-term energy storage in adipose tissue
Also used for structural support, cushioning, and insulation
Formed from a glycerol molecule and three fatty acids
• Phospholipids- cell membranes
• Steroids – Composed of hydrocarbons arranged in a multiringed structure
– Include cholesterol, steroid hormones (e.g., testosterone), and bile salts
• Eicosanoids
– Have functions in the inflammatory response, in the nervous system, and all body
systems ex. prostaglandins
Biological Macromolecules: Lipids
• Fatty acids – vary in length
– Are varied in the number of double bonds
• saturated if they lack double bonds
• unsaturated if they have one double bond
• polyunsaturated if they have two or more double bonds
• Adipose tissue
– Forms triglycerides when energy is excess
• termed lipogenesis
– Breaks down triglycerides when needed
• termed lipolysis
Other lipids
Glycolipids
lipid molecules with carbohydrate attached
associated with the plasma membrane
involved in cellular binding
Fat soluble vitamins vitamins A, E, and K
Figure 2.25a
Copyright © The McGraw–Hill Companies, Inc. Permission required for reproduction or display.
(a) Lipids Nonpolar and amphipathic molecules with four major subclasses
Triglycerides (storage form)
H
H C OH
H C OH
H C OH
Fatty acid (saturated
or unsaturated)
H
Triglycerides are the most
Adipose connective tissue common form of lipid in living
cells with fat droplets
things. They are used for
long-term energy storage,
structural support, cushioning,
and insulation of the body.
Glycerol
Fatty acid
Blood
Eicosanoids (local acting molecules)
Phospholipids
Steroids
Component
of plasma
membrane
Cholesterol
Precursor for steroid
hormones and bile salts
Plasma membrane
Chemical
barrier of
cells
Polar head
Nonpolar tails
Prostaglandins
Prostacyclins
Thromboxanes
Leukotrienes
Major
Classes of
Lipids
(Table 2.3)
Biological Macromolecules: Lipids
Clinical View—Fatty Acids: Saturated,
Unsaturated, and Trans Fats
• Most animal fats are saturated
– Most solid at room temp
• Most vegetable fats are unsaturated
– Most liquid at room temp
– Generally healthier
– Can be converted to saturated fats through hydrogenation
• Partial hydrogenation can lead to trans fats
– Increase the risk of heart attack and stroke
Biological Macromolecules: Carbohydrates
• Carbohydrates
– An –H and an –OH usually attached to every carbon
– Chemical formula is (CH2O)n
• n the number of carbon atoms
– Monosaccharides
• simple monomers(sugars)
• Formula:
• Examples:
– Disaccharides
• formed from two monosaccharides
• Formula:
• Examples:
– Polysaccharides
• formed from many monosaccharides
• Examples:
Biological Macromolecules: Carbohydrates
Glucose and Glycogen
• Glucose
–
–
–
–
–
Six-carbon carbohydrate
Most common monosaccharide
Primary nutrient supplying energy to cells
Concentration carefully maintained
Bound into the polysaccharide glycogen during glycogenesis
• Liver and skeletal muscle store excess glucose following a meal
– Broken down from glycogen during glycogenolysis
• Liver breaks down glucose from glycogen as needed
Copyright © The McGraw–Hill Companies, Inc. Permission required for reproduction or display.
Figure 2.20
Glycogenesis
CH2OH
C
O
H
C
H
OH
H
H
C
OH
HO
C
C
H
OH
(a) Glucose
Glycogenolysis
(b) Glycogen
Figure 2.21
Copyright © The McGraw–Hill Companies, Inc. Permission required for reproduction or display.
Monosaccharides
6–carbon sugars (hexose)
CH2OH
CH2OH
O
HO
H
OH
H
OH
H
OHCH2
O
H
H
H
5–carbon sugars (pentose)
HO
CH2OH
OH
Galactose
O
H
HO
OH
OHCH2
H
H
H
O
OH
H
OH
H
H
OH
OH
Ribose
Fructose
H
H
H
OH
H
Deoxyribose
(a)
Disaccharides
CH2OH
CH2OH
O
H
H
OH
H
HO
O
H
O
H
H
OH
OH
HO
Sucrose
H
O
H
H
OH
CH2OH
H
(b)
CH2OH
H
H
OH
OH
H
H
CH2OH
H
O
H
HO
H
H
OH
O
CH2OH
Lactose
O
H
H
OH
OH
H
HO
H
CH2OH
H
O
H
O
H
OH
Maltose
H
H
H
OH
OH
OH
Biological Macromolecules: Proteins
• Proteins serve a vast array of functions
–
–
–
–
–
–
–
Serve as catalysts (enzymes) in metabolic reactions
Act in defense
Aid in transport
Contribute to structural support
Cause movement
Perform regulation
Provide storage
Protein
Functions
(Table 2.5)
Biological Macromolecules: Proteins
General protein structure
• Proteins composed of one or more strands of
monomers
• Monomers are amino acids
– 20 total in living organisms
– Have an amine and a carboxylic acid functional group
• both covalently linked to same carbon atom
– Carbon also covalently bonded to a hydrogen and different side chain
structures
• referred to as the R group
• distinguish different amino acids from one another
– Amino acids covalently linked by peptide bonds
Figure 2.24
Copyright © The McGraw–Hill Companies, Inc. Permission required for reproduction or display.
Amino acid
Carboxylic
acid
Amine
H
Peptide bond
Peptide bond
H
H
O
N
C
C
R
R group (1 of 20
different structures)
OH
H
H
H
O
N
C
C
OH
R
(a)
H
H
H
O
N
C
C
OH
R
H2O
(b)
Polymer protein
Carboxylic
acid
Amine
H
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
N
C
C
N
C
C
N
C
C
N
C
C
N
C
C
N
C
C
N
C
C
N
C
C
N
C
C
N–terminal
(c)
R
R
R
R
R
R
R
R
R
OH
C–terminal
Copyright © The McGraw–Hill Companies, Inc. Permission required for reproduction or display.
Glycine
(Gly)
Nonpolar
H
O
C
C
OH
NH2
Isoleucine
(Ile)
H
O
C
C OH
H
O
NH2
C
C
H
C
CH3
CH
H
CH3 CH3
Alanine
(Ala)
NH2
H
O
C
C
Leucine
(Leu)
OH
NH2
Phenylalanine
(Phe)
H
O
C
C OH
NH2
CH2
CH2
CH2
CH3
CH3 CH3
H
O
C
C
OH
Tryptophan
(Trp)
H
O
NH2 C
C
CH2
OH
CH2
C
HN
OH
CH3
Polar
Serine
(Ser)
NH2
H
O
C
C
Threonine
(Thr)
H
OH
Asparagine
(Asn)
O
NH2
C
C
OH
C
CH3
CH2
NH2
OH
CH3
OH
H
O
C
C
OH
Glutamine
(Gln)
NH2
H
O
C
C
CH2
CH2
C
CH2
NH2 O
Tyrosine
(Tyr)
OH
NH2
Charged
NH2
H
O
C
C
NH2
CH2
CH2
O
H
O
C
C
Histidine
(His)
NH2
OH
H
O
C
C
CH2
CH2
C
C
O
C
C
C
O–
HC
O–
OH
Lysine
(Lys)
OH
NH2
H
O
C
C
Arginine
(Arg)
OH
CH2
H
N
N
H+
CH
NH2
H
O
C
C
CH2
CH2
CH2
CH2
CH2
NH3+
NH
NH2
Cysteine
(Cys)
NH2+
CH2 CH
O
C
O–
CH2 CH2
NH2
H
O
C
C
Methionine
(Met)
OH
NH2
H
O
C
C
CH2
CH2
S
CH2
H
S
OH
CH3
Allows bends
in protein chain
Forms
disulfide bond
Always the first amino acid
in a protein sequence
(may be removed following
synthesis of protein)
OH
CH2
CH2
Proline
(Pro)
OH
(+) Charge
Aspartic acid
(Asp)
OH
O
C
(–) Charge
Glutamic acid
(Glu)
H
CH2
NH2 O
Special functions
Figure 2.26
NH2
Valine
(Val)
NH2+
Protein Structure: Amino Acid Sequence and
Protein Conformation
• Primary structure, linear sequence of amino acids
Copyright © The McGraw–Hill Companies, Inc. Permission required for reproduction or display.
Primary structure
Linear sequence of amino acids joined by peptide bonds
Figure 2.27a
Peptide bond
Amino acid
H
H
N
O
R
C
C
C
N
R
H
(a)
C
H
O
Biological Macromolecules: Nucleic Acids
– Macromolecules that store and transfer genetic information in cells
– Two classes deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)
Copyright © The McGraw–Hill Companies, Inc. Permission required for reproduction or display.
Nitrogenous base
The nucleotide
monomer
– Three components: sugar,
phosphate group, and a
nitrogenous base
• sugar a five-carbon
pentose
• phosphate group attached
at carbon five
• nitrogenous base attached
to same sugar at carbon
one
• nitrogenous base with
single-ring or double-ring
structure
NH2
P
N
Phosphate group
O
–O
P
N
O
N
CH2
O–
O
Sugar
OH in RNA
OH
H in DNA
(a) Nucleotide monomer
Figure 2.22a
Deoxyribonucleic acid (DNA)
Double-stranded nucleic acid
Found in chromosomes in the nucleus and in mitochondria
Has deoxyribose sugar, phosphate, and one of four nitrogenous bases:
adenine, guanine, cystosine, or thymine
does not contain uracil
Double-strands held together by hydrogen bonds
thymine paired with adenine; guanine paired with cytosine
– Responsible for directing the synthesis of proteins
• essential for multiple body functions
• over 10,000 different proteins in the human body
•Ribonucleic acid (RNA)
–Single-stranded nucleic acid
–Found in the nucleus and within cytoplasm of the cell
–Has ribose sugar, phosphate, and one of four nitrogenous bases:
•adenine, guanine, cystosine, or uracil
•does not contain thymine
Figure 2.22b
Pyrimidines
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NH2
O
C
C
HC
N
HC
C
CH3
C
Cytosine (C)
(both DNA and RNA)
Purines
O
C
N
C
C
NH
C
C
HC
HC
N
H
CH
C
N
Adenine (A)
(both DNA and RNA)
(b) Nitrogenous bases
N
H
N
NH
HC
C
O
Uracil (U)
(RNA only)
O
N
HC
N
H
Thymine (T)
(DNA only)
NH2
C
C
N
H
N
H
N
C
NH
HC
O
O
NH2
Guanine (G)
(both DNA and RNA)
Figure 2.22c-d
Copyright © The McGraw–Hill Companies, Inc. Permission required for reproduction or display.
U
Unique to RNA
P
O
5′
Phosphate
group
Nitrogenous
base
G
P
Sugar–phosphate
“backbone”
Nitrogenous
base
Nucleotide
Deoxyribose
sugar
O
Ribose
sugar
Nucleotide
Phosphate
group
P
A
A
P
P
O
T
G
P
Phosphodiester
bonds
C
P
T
P
Unique to DNA
C
P
A
O
P
Hydrogen bonds
between
nitrogenous bases
OH
3′
(c) RNA (single–stranded)
3′
(d) DNA (double–stranded)
5′
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chromosome
Figure 4.31b
T
A
Hydrogen bonds
C
G
Complementary
base-pairing
A
T
C
Sugarphosphate
backbone
C
Coiled chromatin
A
T
DNA
Histones
C
G
G
Nucleosome
(b) Levels of organization
Nitrogenous
bases
A
Function of the Nucleus and Ribosomes—
Transcription: Synthesizing RNA
Process of Transcription
• Three types of RNA produced during transcription:
– messenger RNA (mRNA)
– transfer RNA (tRNA)
– ribosomal (rRNA)
• Three events of transcription:
– Initiation DNA unwound by specific enzymes
– Bonds broken between DNA DNA strand copied by mRNA, termed template
strand
– Other strand, coding strand, not copied
– Termination Rewinding of DNA into double helix
Function of the Nucleus and Ribosomes—
Translation: Synthesizing Protein
• Translation
–
–
–
–
–
–
Synthesis of a new protein
mRNA threaded through ribosome
Code in nucleotide sequence of mRNA translated
Converted into amino acids to produce protein
Takes place at ribosomes within the cytoplasm
mRNA transcribed from genes
• linear sequence of nucleotides
• carries “instructions” for synthesizing proteins
• read three bases at a time, in codons
– Types of codons:
• start codon, AUG, signal to begin protein synthesis
• consecutive codons, code for amino acids
• stop codon, where mRNA reading ends
Function of the Nucleus and Ribosomes—
Translation: Synthesizing Protein
Required Structures
– Transfer RNA (tRNA)
• brings specific amino acids to a specific mRNA codon
• “cloverleaf” shape
• has region termed anticodon
– base pairs with complementary codon in mRNA
• has amino acid acceptor region
– where specific amino acid attaches to tRNA
– based on tRNA’s anticodon sequence
– Amino acids
• building blocks for protein synthesis
• 20 found in proteins of living things
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 4.35
Summary of
transcription
and translation
Transcription of
DNA in the
nucleus forms
RNA molecule
mRNA is processed
prior to exiting
nucleus
Translation of
mRNA into
protein occurs at
a ribosome in the
cytoplasm
1 Transcription. Occurs within the nucleus.
Pre-mRNA is transcribed from DNA and
processed to form mature mRNA prior
to leaving the nucleus.
Events in
nucleus
mRNA
Template
strand
Nucleus
mRNA processing
Mature
mRNA
exits the
nucleus
Protein
2 Translation.
Follows transcription;
mRNA is read to direct
tRNAs in adding
amino acids;
protein molecule
is formed.
Events in
cytoplasm
tRNA
mRNA
Ribosome
Transcription – mRNA carries the code
DNA
C–G
T–A
G–C
A–T
C–G
G–C
mRNA
tRNA amino acid
C
G
U
A
aspartic acid
G
C
A
U
C
G
cysteine
G
C
(transcription) (translation)
(codons)
anticodons
Translation – tRNA translates the code
Protein synthesis – rRNA makes the protein
rRNA
assemble
amino
acids
make
the
protein
Biological Macromolecules: Nucleic Acids
Other important nucleotides
• Adenosine triphosphate (ATP)
– Nucleotide composed of nitrogenous bases adenine, ribose sugar, and
three phosphate groups
– Covalent bonds between last two phosphate groups
• release energy when broken
– Central molecule in chemical energy transfer within cells
• Nicotinamide adenine dinucleotide (NAD+) and
flavin adenine dinucleotide (FAD)
– Nucleotides participating in the formation of ATP
Energy, Chemical Reactions, and
Cellular Respiration
• All living organisms require energy
• We need energy to:
–
–
–
–
–
–
power muscle
pump blood
absorb nutrients
exchange respiratory gases
synthesize new molecules
establish cellular ion concentrations
• Glucose broken down through metabolic pathways
– Forms ATP, the “energy currency” of cells
Energy: Forms of Energy
Chemical Energy (A Form of Potential Energy)
energy stored in a molecule’s chemical bonds
Molecules function in chemical energy storage
– Triglycerides
• long-term energy storage in adipose tissue
– Glucose
• glycogen stores in liver and muscle
– ATP
• stored in all cells
• produced continuously and used immediately
– Protein
• can be used as a fuel molecule but has more important functions
Figure 3.3a
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a) Potential and Kinetic Energy
Potential Energy: The energy of position
Na+
Na+ ions have
potential energy due
to concentration
gradient difference
between the
outside and
inside of
the cell.
Na+
The Two States of Energy
Kinetic Energy: The energy of motion
Na+
Na+
Na+
Na+ ions
exhibit kinetic
energy as they
move down the
concentration
gradient.
Na+
Na+
Na+
Na+
Na+
Chemical Reactions: Chemical Equations
• Metabolism
– Collective term for all chemical reactions in the body
• Chemical reactions
– Occur when chemical bonds in existing molecular structures are broken
– New bonds formed
– Summary of changes written as a chemical equation
Chemical Reactions: Classification of
Chemical Reactions
• Classified based on three criteria:
– changes in chemical structure, changes in chemical energy, and whether the
reaction is irreversible or reversible
Classification Based on Changes in Chemical Structure
• Catabolism
– Collective term for all decomposition reactions
• Anabolism
– Collective term for all synthesis reactions
• Metabolism
– Collective term for all chemical reactions in the body
Chemical Reactions: Classification of
Chemical Reactions
• Decomposition reaction
– Initial large molecule broken down into smaller structures
• e.g., the hydrolysis reaction of sucrose into glucose and fructose
Figure 3.4a
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Decomposition reaction: A large molecule is broken down into smaller chemical structures; AB
CH2OH
CH2OH
H
O
H
OH
H
HO
H
O
H
O
H
CH2OH
CH2OH
H
OH
CH2OH
OH
OH
Sucrose
(a)
H
H
H2O
A+B
O
H
OH
+
H
HO
OH
H
OH
Glucose
O
H
H
H
OH
HO
CH2OH
OH
H
Fructose
Chemical Reactions: Classification of
Chemical Reactions
Classification Based on Changes in Chemical Structure
Synthesis reaction
– Two or more structures combined to form a larger structure
• e.g., the dehydration synthesis reaction forming a dipeptide
Figure 3.4b
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Synthesis reaction: Two or more atoms, ions, or molecules are combined to form a larger chemical structure; A + B
H2O
Amino acids
(b)
Dipeptide
AB
Chemical Reactions: Classification of
Chemical Reactions
Classification Based on Changes in Chemical Energy
• Exergonic reactions
– Reactants with more energy within their chemical bonds than products
– Energy released with net decrease in potential energy
– E.g., decomposition reactions
• Endergonic reactions
– Reactants with less energy within their chemical bonds than products
– Energy supplied with a net increase in potential energy
– E.g., synthesis reactions
Chemical Reactions: Classification of
Chemical Reactions
• ATP cycling
– The continuous formation and breakdown of ATP
– ATP formed from energy released in exergonic reactions
• fuel molecules from food oxidized
• energy in their bonds transferred to ADP and free phosphate to form ATP
– ATP oxidized
• released energy used for energy-requiring processes
– Only a few second worth of ATP present at a time
• formation of ATP occurs continuously to provide energy
Figure 3.7
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ATP
(a) ATP formation
(Endergonic reaction)
Triphosphate
group
P
Energy
supplied
P
Adenine
(b) Splitting ATP
(Exergonic reaction)
P
High-energy
bond
Ribose
Energy
released
ADP
P
Phosphate (Pi)
Adenine
Diphosphate
group
P
P
Ribose
P
Cellular Respiration
• Exergonic multistep metabolic
pathway
• Organic molecules oxidized
and disassembled by a series
of enzymes
• Potential energy in chemical
bonds released
• Energy used to make ATP
(endergonic process)
• Oxygen required
Cellular Respiration: Overview of
Glucose Oxidation
• Enzymes for glucose oxidation are found in both:
– The cytosol, semifluid cell contents
– The mitochondria, small organelles within the cell
• Stages of glucose oxidation:
– Glycolysis (anaerobic cellular respiration)
• occurs in cytosol
• can occur without oxygen
– citric acid cycle
– electron transport system
• other three collectively referred to as aerobic cellular respiration
• require oxygen
• occur in mitochondria
The role of mitochondria in the production of the high-energy compound ATP
Although most ATP production
occurs inside mitochodria,
the first steps take place in the
cytosol. In this reaction
sequence, called glycolysis
(glycos, sugar + -lysis, a
loosening), each glucose
molecule is broken down into
two molecules of pyruvate. The
pyruvate molecules are then
absorbed by mitochondria.
Glucose
CYTOPLASM
The energy released
during a series of steps
performs the enzymatic
conversion of ADP to
ATP, which leaves the
mitochondrion.
2 Pyruvate
MITOCHONDRION
Citric acid
cycle
Enzymes and
ADP +
phosphate coenzymes
of cristae
MATRIX
In the mitochondrial matrix, a
CO2 molecule is removed
from each absorbed pyruvate
molecule; the remainder
enters the citric acid cycle,
of TCA (tricarboxylic acid)
cycle, an enzymatic pathway
that systematically breaks
down the absorbed pyruvate
remnant into carbon dioxide
and hydrogen atoms.
The hydrogen atoms are
delivered to enzymes and
coenzymes of the cristae
which catalyze the
synthesis of ATP from
ADP and phosphate. At
the end of this process,
oxygen combines with the
hydrogen atoms to form
water molecules.
Figure 3.6 2
Figure 3.15
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cytosol
Mitochondrion
Cellular Respiration
Anaerobic cellular respiration
(glycolysis occurs in cytosol)
Glycolysis
Intermediate stage
Citric
acid
cycle
Electron transport system
Aerobic cellular respiration
(intermediate stage, citric acid cycle,
and electron transport system occur
in mitochondria)
Cellular Respiration—Glycolysis:
Anaerobic Cellular Respiration
• Glycolysis
– Anaerobic process in the cytosol
– Glucose broken down into two pyruvate molecules
• pyruvate’s fate dependent on oxygen availability
– Net production of 2 ATP and 2 NADH molecules
– Pathway contains ten enzymes
Summary of Glycolysis
• Glucose initial substrate
• Pyruvate final product
• Net 2 ATP formed (2 invested, 4 formed)
• Two NADH formed
Cellular Respiration—Glycolysis:
Anaerobic Cellular Respiration
The Fate of Pyruvate
• Chemical changes made to pyruvate depend upon
oxygen availability
– If sufficient O2 available, pyruvate enters mitochondria
– If insufficient O2 available, pyruvate converted to lactate
Cellular Respiration—Aerobic Cellular
Respiration: Citric Acid Cycle “KREB’S”
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Cyclic metabolic pathway
– ATP, 3 NADH, and 1 FADH2
formed during one cycle
– Occurs in mitochondria
– Requires oxygen
– Acetyl CoA initial substrate
– Two CO2 and one CoA produced
– 1 ATP, 3 NADH, 1 FADH2
formed per cycle
– Oxaloacetic acid involved in
first step and regenerated in last
step
– Two “turns” for one glucose
molecule
• 2 ATP, 6 NADH, 2 FADH2
Pyruvate
Acetyl CoA
CoA
OAA regenerated
CO2
NADH
NAD+
Citric
acid
cycle
FADH2
NAD+
NADH
CO2
FAD
NAD+
ATP
ADP
NADH
(a) Net chemical reaction of citric acid cycle
Cellular Respiration—Aerobic Cellular
Respiration: The Electron Transport System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• The electron
transport system
Cristae
Matrix
– Involves the transfer
of electrons from
NADH and FADH2
• energy released
used to make ATP
– Involves structures
located in the inner
membrane of
mitochondria
ATP
synthetase
Electron
carriers
Outer
compartment
Q
H+
H+
H+
H+
Outer
membrane
• electron carriers, H+
pumps, ATP
(a) Structures of the electron transport system
synthetase enzymes
(Figure 3.20)
H+
C
H + pumps
Figure 3.20c
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Glycolysis
NADH
NADH
Intermediate stage
Matrix
NADH
e-
FADH2
Citric
acid
cycle
e-
ATP
1 O
2 2
e-
ADP
+ Pi
H+
ATP synthetase
H2O
H+
H+
H+
H+
H+
H+
H+
H+
Electron carriers
H+ pumps
1 Electrons are transferred from NADH and
FADH2 through a series of electron carriers
within the cristae. O2 is the final electron
acceptor.
(c) Details of the electron transport system
2
Energy of electrons “falling” is used to move
H+ up its concentration gradient from the
matrix to the outer compartment.
3 ATP synthetase harnesses the kinetic energy
of the H+ “falling” down its concentration
gradient to bond ADP and Pi to form ATP.
Cellular Respiration: ATP Production
• ATP in glucose breakdown
Stage/Total
Glycolysis
Intermediate Stage
Citric Acid Cycle
Substrate level
phosphorylation
2 ATP
––
2 ATP
Total
4 ATP
Oxidative
phosphorylation
2 NADH to 6 ATP
2 NADH to 6 ATP
6 NADH to 18 ATP
2 FADH2 to 4 ATP
34 ATP
– Transport of NADH during glycolysis takes 1 ATP per NADH
– Total = 4 ATP + 34 ATP – 2 ATP = 36 ATP for one molecule glucose
Enzymes: Function of Enzymes
• Enzymes
–
–
–
–
Are catalysts that accelerate normal chemical activities
Decrease the activation energy of cellular reactions
Only facilitate reactions that would already occur
Increase the rate of product formation
• Chemical reactions
– Are termed uncatalyzed reactions if no enzyme present
– Are termed catalyzed reactions if enzyme present
Enzymes: Structure and Location
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Active site
Active site’s
specificity of
shape:
Substrate
– permits only a
single substrate
to bind
– helps catalyze
only one
specific reaction
Enzyme
(Figure 3.9)
Enzyme-substrate complex
Enzymes: Structure and Location
• Enzyme produced from normal protein synthesis within
cells
– Some remain within cells
• e.g., DNA polymerase which helps form DNA
– Some become embedded in plasma membrane
• e.g., lactase in walls of small intestine cells
• helps digest lactose
– Some are secreted from the cell
• e.g., pancreatic amylase
• released from pancreas to participate in starch digestion
Cofactors
– Molecules or ions required for normal enzyme function
– Associate with particular enzyme
– Nonprotein organic or inorganic structure
• organic cofactors called coenzymes
– e.g., vitamins or modified nucleotides serving as coenzymes
Figure 3.10a
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Decomposition reaction: Lactose digested to glucose and galactose
Lactose
1 The substrate binds
Glucose
Enzyme-substrate complex
(a)
3 The bond is
broken between
glucose and
galactose.
4 Products: Glucose
Substrate: Lactose
Enzyme: Lactase
shape, resulting in an
induced fit between
substrate and enzyme.
O
Galactose
2 The enzyme changes
to the enzyme, forming
an enzyme-substrate
complex.
and galactose are
released, and the
enzyme is free to
bind other substrates.
Enzymes: Classification and
Naming of Enzymes
• Enzyme names
– Generally based on:
• the name of substrate or product
• sometimes subclass
• suffix –ase
– E.g., pyruvate dehydrogenase transferring hydrogen from pyruvate
– E.g., DNA polymerase helping form DNA
– E.g., lactase digesting lactose
Enzymes: Enzymes and Reaction Rates
Effect of Temperature
• Three-dimensional shape of enzymes dependent on
temperature
– Human enzymes function best at optimal temperature
• normal to slightly elevated body temperature (95-104° F)
– Moderate fever
• results in more efficient enzyme activity
– Severe increases in temperature
• cause protein denaturation with loss of function
Enzymes: Enzymes and Reaction Rates
Effect of pH
• Enzymes function best at optimal pH
–
–
–
–
Between pH of 6 and 8 for most enzymes
Changes in H+ disrupting electrostatic interactions
Enzyme loss of shape, denaturation
Optimal pH may differ
• e.g., enzymes working in the lower pH of the stomach
Cellular Respiration: Other Fuel Molecules
That Are Oxidized in Cellular Respiration
• Other fuel molecules can be oxidized to generate
ATP
– Increases during conditions of starvation
– Fatty acids
• preferred molecule for muscle tissue at rest
• provide long-term energy reserves
• enzymatically changed two carbons at a time to form acetyl CoA
(beta-oxidation)
• acetyl CoA enters pathway at citric acid cycle
• can only be used aerobically
– Proteins
• different amino acids enter pathway at different points
• amine group removed and waste converted to urea and excreted
88
Membrane Transport—
Passive Processes: Diffusion
• Diffusion
– Describes net movement of a substance
– Moves from area of greater concentration to area of lesser
concentration
– Molecules and ions in constant motion due to kinetic energy
– If unopposed, continues until substance reaches equilibrium
• molecules evenly distributed throughout a given area
– “Steepness” of concentration gradient
• difference in concentration between two areas
• steeper gradient with a faster rate of diffusion
– Temperature
• higher movement with higher temperature
• results in faster rate of diffusion
Figure 4.7
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Membrane Transport—
Passive Processes: Diffusion
Cellular Diffusion
• Simple diffusion
–
–
–
–
Molecules passing between phospholipid molecules
Include respiratory gases (O2 and CO2), some fatty acids, ethanol, urea
Movement dependent on concentration gradient alone
Continue to move as long as gradient exists
• Facilitated diffusion
– Require assistance from plasma membrane proteins
– Maximum rate of transport determined by number of channels and
carriers
• higher rate with greater number of transport proteins
Figure 4.8
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Small nonpolar solutes move down
their concentration gradients.
Interstitial
fluid
Oxygen
Cytosol
Carbon dioxide
Figure 4.9a
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ions move down their concentration
gradient through water-filled channels.
Na+
Interstitial
fluid
Cytosol
(a) Channel-mediated diffusion
Na+
leak channel
K+ leak
channel
K+
Figure 4.9b
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Carrier proteins change shape to transport
molecules across the plasmamembrane.
Carrier-mediated diffusion
Interstitial
fluid
Glucose
Cytosol
Glucose carrier protein
(b) Carrier-mediated diffusion
Small, polar molecules assisted across membrane by
carrier protein
Transport substances such as glucose
Binding of substance causing change in carrier protein
shape
Move substances down their gradient
Membrane Transport—
Passive Processes: Osmosis
• Osmosis
– Passive movement of water through selectively permeable membrane
• membrane allowing passage of water
• membrane preventing passage of most solutes
– Occurs in response to differences in water concentration
• different concentrations on either side of a membrane
Semipermeable membrane allowing for passage of water only
Side A with more solutes initially
Water moving from side B to side A by osmosis
Continues until fluids equal in concentration
Figure 4.11
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Side A
Side B
Side A
Side B
Non-permeable solutes (glucose, Na+, protein)
Water molecules
Higher solute Semipermeable
concentration,
membrane
lower water
concentration
Lower solute
concentration,
higher water
concentration
Initial setup: Side A contains proportionately
more solute and less water.
Semipermeable
membrane
Final setup: Water moved by osmosis from side
B down the water gradient to side A until the
concentrations of side A and side B are equal.
Osmosis
Osmosis Isotonic solution
– Both cytosol and solution with same relative concentration of solutes
– saline with a concentration of 0.9% NaCl Isotonic to erythrocytes
– No net movement of water
• Hypotonic solution
–
–
–
–
Solution with a lower concentration of solutes than cytosol
E.g., erythrocytes in pure water
Water moving down concentration gradient
May cause cell lysis (rupture)
• hemolysis, term for ruptured red blood cells
• Hypertonic solution
–
–
–
–
Solution with a higher concentration of solutes than cytosol
E.g., erythrocytes in 3% NaCl pure water
Water moves down concentration gradient
May cause cell to shrink
• termed crenation
Figure 4.12
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Isotonic solution
Hypotonic solution
Interstitial fluid is less
concentrated than cytosol.
Interstitial fluid is the same
concentration as cytosol.
Erythrocyte
Water
leaves
cell.
Erythrocyte
Erythrocyte
SEM 11,550x
SEM 9030x
SEM 6900x
Interstitial fluid is more
concentrated than cytosol.
Water
enters
cell.
No net
movement
of water.
Normal erythrocytes
(a)
Hypertonic solution
Erythrocytes nearing hemolysis
(b)
Erythrocytes undergoing crenation
(c)
a: © Dennis Kunkel Microscopy, Inc./Phototake; b: © Dennis Kunkel Microscopy, Inc./Phototake; c: © Dennis Kunkel Microscopy, Inc./Phototake
Membrane Transport: Active Processes
Active Transport
–
–
–
–
Opposes the movement of solutes by diffusion
Solutes moved against a concentration gradient
Maintains gradient between cell and interstitial fluid
Uses energy directly from breakdown of ATP
Membrane Transport: Active Processes
Figure 4.13
• Ion pumps
– Active transport proteins
that move ions across
membrane
– Help cell maintain
internal concentration of
ions
– E.g., Ca2+ pumps in
plasma membrane of
erythrocytes
• prevent cell rigidity
from accumulated
calcium
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Erythrocyte
ADP
+Pi
ATP
Ca2+
pump
Ca2+
Cytosol
Interstitial
fluid
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cytosol
Interstitial fluid
Secretory
vesicle
Plasma
membrane
Figure 4.16
Vesicle membrane
1 Vesicle nears plasma membrane
Vesicular Transport
Requires vesicles
Membrane
proteins
membrane-bounded sac
filled with materials
Requires energy to
transport vesicles
– Exocytosis
• vesicle fuses with
membrane
• releases substances
outside the cell
• E.g., release of
neurotransmitters
from nerve cells
– Endocytosis
2 Fusion of vesicle membrane with plasma membrane
Plasma
membrane
opens
3 Plasma membrane opens to outside of cell
4 Release of vesicle components into the interstitial
fluid and integration of vesicle membrane
components into the plasma membrane
• vesicle encloses
material outside
cell
• fuses with
membrane to
release inside cell
• phagocytosis,
pinocytosis
Membrane Transport: Active Processes
• Phagocytosis
–
–
–
–
Occurs when cell engulfs large particle external to cell
Forms large extensions termed pseudopodia
Surround particle, enclosing it in membrane sac
Fuses with lysosome
• contents digested here
– Only in a few cell types
• E.g., white blood cells engulfing microbes
• Pinocytosis
–
–
–
–
–
Internalization of droplets of interstitial fluid
Multiple, small vesicles formed
All dissolved solutes taken into cell
Performed by most cells
E.g., cells of capillary wall