Transcript (H) +

HUMAN ANATOMY & PHYSIOLOGY
CHAPTER 2: BIOCHEMISTRY
-THE CHEMICAL BASIS OF LIFE
1
Chemical Basis of Life
Why study chemistry in an
Anatomy and Physiology class?
- Body functions depend on cellular functions
- Cellular functions result from chemical changes
- Biochemistry helps to explain physiological processes
2
Chemical Basis of Life
Matter – anything that takes up space and has mass –
composed of elements
Elements – atoms of the same element are identical
• 11 Bulk elements – required by the body in large amounts
 carbon, oxygen, hydrogen, and nitrogen make up 96% of
the human body
• 15 Trace elements - required by the body in small
amounts
Atoms – smallest particle of an element
3
4
Table 2.1 Some Particles of Matter
5
Atomic Number and Atomic Mass
 Atomic number
 Number of protons in an atom’s nucleus
 Identifies the element
 Atomic Mass
 Mass of a single atom
 Equal to the number of protons plus the
number of neutrons in the nucleus
How many protons, neutrons, and electrons
does carbon have?
What is the atomic mass of carbon?
6
Molecules and Compounds
Molecule – particle formed when two or more atoms
chemically combine – form a covalent bond –
C6H12O6
O2
Compound – particle formed when two or more atoms of
different elements chemically combine
Molecular formulas – depict the elements present and
the number of each atom present in the molecule
H2
C6H12O6
H2O
7
Bonding of Atoms
• Bonds form when atoms combine with other atoms
•Electrons are shared or transferred during bonding
• Electrons of an atom occupy regions of space called
electron shells which circle the nucleus
• For atoms with atomic numbers of 18 or less, the following
rules apply:
• The first shell can hold up to 2 electrons
• The second shell can hold up to 8 electrons
• The third shell can hold up to 8 electrons
8
Bonding of Atoms
• Lower shells are filled first
• If the outermost shell is full, the atom is stable
-
+
Hydrogen (H)
0
-
-
+
+ 0
+
0
0
0
+
+
0
-
-
Helium (He)
Lithium (Li)
-
9
Bonding of Atoms: Ions
Ion
• An atom that gains or loses electrons to become stable
• An electrically charged atom
Cation
• A positively charged ion
• Formed when an atom loses electrons
•K+, Ca2+
Anion
11p+
12n0
Sodium atom (Na)
17p+
18n0
Chlorine atom (Cl)
• A negatively charged ion
• Formed when an atom gains
electrons
• Cl-, O210
Types of Bonds
Ionic Bonds – between a metal and a nonmetal
• An attraction between a cation and an anion
• Formed when electrons are transferred from one atom to
another atom
•NaCl MgBr2
Na+
+
11p+
12n0
17p+
18n0
Sodium ion (Na+)
–
Cl–
Chloride ion (Cl–)
Sodium chloride
11
Types of Bonds
Covalent Bonds – between nonmetals
 Formed when atoms share electrons
 H2O C6H12O6
H
-
H
-
H2
-
+
+
+
+
-
Hydrogen atom
+
Hydrogen atom
• Hydrogen atoms form single bonds
• Oxygen atoms form two bonds
• Nitrogen atoms form three bonds
• Carbon atoms form four bonds
Hydrogen molecule
H―H
O=O
N≡N
O=C=O
12
Bonding of Atoms:
Structural Formula
• Structural formulas show how atoms bond and are arranged in
various molecules
H
H
H
H2
O
O
O2
H
O
H2O
O
C
O
CO2
13
Bonding of Atoms:
Polar Molecules
Covalent Polar Molecules
• Molecule with a slightly negative end and a slightly positive end
• Results when electrons are not shared equally in covalent bonds
• Water is an important polar molecule
Slightly negative ends
(a)
Slightly positive ends
14
Hydrogen Bonds
Hydrogen Bonds
• A weak attraction between the positive end of one polar
molecule and the negative end of another polar molecule
• Formed between water molecules
• Important for protein and nucleic acid structure
H
H
O
H
O
H
O
H
O
H
H
O
(b)
Hydrogen bonds
H
H
H
15
Chemical Reactions
Chemical reactions occur when chemical bonds form or
break among atoms, ions, or molecules
Reactants are the starting materials of the reaction
Products are substances formed at the end of the chemical
reaction
NaCl  Na+ + ClReactant
Products
16
Types of Chemical Reactions
1. Synthesis Reaction – 2 or more reactants combine to
form a larger product
A + B  AB
2. Decomposition Reaction – chemical bonds are broken to form
a simpler chemical structure
AB  A + B
3. Exchange Reaction – chemical bonds are broken and new
bonds are formed
AB + CD  AD + CB
Reversible Reaction – the products can change back to the
reactants
A + B n AB
17
Acids, Bases, and Salts
Electrolytes – substances that dissociate to release
ions in water
+
NaCl  Na + Cl
Acids – substances that dissociate to release hydrogen ions
in solution
HCl  H+ + Cl-
Bases – substances that dissociate to release hydroxide ions
(OH-) in solution
NaOH  Na+ + OH-
Salts – electrolytes formed by the reaction between an
acid and a base
HCl + NaOH  H2O + NaCl
18
Acid and Base Concentration
pH scale - indicates the concentration of hydrogen ions in
solution
Neutral – pH 7;
indicates equal
concentrations of H+
and OH-
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Acidic
Relative
+
Amounts H
+
of H (red)
3.0
and OH–
2.0
apple
(blue)
gastric juice
juice
Acidic – pH less than
7; indicates a greater
concentration of H+
5.3
4.2
cabbage
tomato
juice
8.4
7.4
6.6
Sodium
cow’s Human biocarbonate
blood
milk
6.0
corn
pH 0
1
Acidic
2
3
4
5
H+ concentration increases
6
8.0
7.0
Egg
Distilled white
water
7
Neutral
8
10.5
milk of
magnesia
11.5
Household
ammonia
Basic
OH–
9
10
11
12
13
14
OH– concentration increases
Basic (alkaline)
Basic or alkaline – pH greater than 7;
indicates a greater concentration of OH-
19
Neutralization and Buffers
 Neutralization occurs when an acid and base
react to form a salt and water in a
displacement reaction.
 HCl + NaOH  NaCl + H2O
 Buffers act as acids when pH is high and
bases when pH is low – keep the pH at a
narrow, consistent level
 Carbonic acid-bicarbonate system.
Chemical Constituents
of Cells
Inorganic molecules
• Generally do not contain C and H
• Usually smaller than organic molecules
• Usually dissociate in water, forming ions
• Water, oxygen, carbon dioxide, and inorganic salts
Organic molecules
• Contain C and H
• Usually larger than inorganic molecules
• Dissolve in water and organic liquids
• Carbohydrates, proteins, lipids, and nucleic acids
21
Inorganic Substances
Water
 Most abundant compound in living material
 Two-thirds of the weight of an adult human
 Major component of all body fluids
 Medium for most metabolic reactions
 Dehydration reaction – synthesis reaction – removal of a
water molecule as a bond is formed between two small
molecules to form a larger molecule
 Hydrolysis reaction – - decomposition reaction - uses water
to break the bonds of a compound
22
Inorganic Substances
 Water (cont.)
 Important role in transporting chemicals in the body
 High specific heat – absorbs and gives up heat slowly,
allowing water, and therefore the body, to maintain a
relatively constant temperature

High heat of vaporization

- takes a large amount of heat to change water
from liquid to gas

- used in evaporative cooling of the body
23
Inorganic Substances
Oxygen (O2) and Carbon Dioxide (CO2)
oxygen is needed by cells to carry out
cellular respiration in the mitochondria
 Oxygen is received by respiratory system
and delivered by circulatory system (RBC’s)
 carbon dioxide is waste gas from cellular
respiration

24
Inorganic Substances
Inorganic salts
• Abundant in body fluids
• Sources of necessary ions (Na+, Cl-, K+, Ca2+, etc.)
• Play important roles in metabolism
25
Organic Substances:
Carbohydrates
• Provide energy to cells
• Supply materials to build cell structures
• Water-soluble
• Contain C, H, and O
ef • Ratio of H to O close to 2:1 (C H O )
6 12 6
• Monosaccharides (simple sugars) – glucose, fructose,
galactose, xylose, and ribose
• Disaccharides (double sugars) – sucrose (glucose and
fructose), maltose, lactose – composed of 2 simple sugars
joined together by dehydration reactions
• Polysaccharides (complex sugars) – glycogen, cellulose –
composed of many monosaccharides chemically joined by
dehydration reactions
26
Organic Substances
Carbohydrates
H
O
C
H
H
C
O
O
C
H
H
C
O
H
H
H
H
H
C
O
H
H
C
O
H
H
(a) Some glucose molecules
(C6H12O6) have a straight
chain of carbon atoms.
C
O
O
C
H
C
H
O
H
O
H
H
H C
O
O
C
C
H
O
H
H
(b) More commonly, glucose
molecules form a ring structure.
(c) This shape symbolizes
the ring structure of a
glucose molecule.
27
Organic Substances:
O
Carbohydrates
O
O
O
(b) Disaccharide
(a) Monosaccharide
O
O
O
(c) Polysaccharide
28
Organic Substances:
Lipids –
• Soluble in organic solvents; insoluble in water
•4 major types – triglycerides, phospholipids, steroids,
and prostaglandins
• Composed of C, H, O; but fewer O’s than
carbohydrates
- some also contain P
H
H
C
O
O
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
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
H
H
H
H
H
H
H
H
H
H
H
H
O
H
H
H
29
Organic Substances:
Lipids
 Triglycerides
• formed from a fatty acid and glycerol (a sugar)
• the most plentiful source of stored energy to our bodies
• Two types:
•
•
Saturated- contain only single bonds
Unsaturated- contains one(mono) or more(poly) double bonds
•
Short, unsaturated fats are liquids (oils) and come from plants.
H (butter and meat fat) and come
• Long, saturated fats are solid
from animals.
H
H
O Fatty acid
H
O Fatty acid
H
O Fatty acid
H
glycerol
portion
30
Organic Substances:
Lipids
• Phospholipids
• Building blocks are 1 glycerol, 2 fatty acids, and 1 phosphate per
molecule
• Hydrophilic (water soluble) and hydrophobic (water insoluble)
• Major component of cell membranes
H
H
H
C
O
Fatty acid
H
C
O
Fatty acid
H
C
O
Fatty acid
H
Glycerol portion
(a) A fat molecule
H
C
O
Fatty acid
H
C
O
Fatty acid
O
H
C
H
O
P
O–
O
Water-insoluble
(hydrophobic)
“tail”
H
H
C
C
H
H
H
N
H
Water-soluble
(hydrophilic)
“head”
Phosphate portion
(b) A phospholipid molecule
(the unshaded portion may vary)
(c) Schematic representation
of a phospholipid molecule
31
Organic Substances:
Lipids
• Steroids
• Four connected rings of carbon
• Widely distributed in the body, various functions
• Component of cell membrane
• Used to synthesize hormones
• Cholesterol
H2
C
(a) General structure of a steroid
C
H
(b) Cholesterol
CH
CH2
CH
C
C
H2
CH
CH2
HC
C
H2C
HO
H2 C
CH3
CH3
H2 CH3 H
C
C
C
CH3
CH2
CH2
CH2
CH
CH3
CH2
C
H
32
Organic Substances:
Lipids
 Prostaglandins
 “tissue hormones”
 composed of a 20-carbon unsaturated fatty
acid that contains a 5-carbon ring
 formed and released from cell membranes in
response to a stimulus
 regulate the effects of hormones, influence
blood pressure and secretion of digestive
juices, and enhance the body immune system
and inflammatory response
33
Organic Substances:
Proteins
 2 main catergories according to purpose
1.
structural – form structures of the cells, tissues,
and organs of the body – include keratin of skin,
hair, and nails, parts of cell membrane, and
tendons
2. functional - shape determines the function –
allows it to fit with certain other chemicals and
cause some change in the molecules – enzymes,
insulin
34
Organic Substances:
Proteins
 Consist of amino acids joined together by peptide bonds
 Sequence of amino acids is what DNA actually codes for
 20 commonly occurring amino acids
 amino acids – each consist of an alpha carbon, an amine
group, carboxyl group, hydrogen, and a side chain – the
side chain (R) differentiates the amino acids
35
Organic Substances:
Proteins
36
Organic Substances:
Proteins
 Protein Structure
 Primary structure - linear sequence of amino
acids
 Secondary structure – regular folds or twists in
proteins – most common is alpha helix (spiral
staircase)
 Tertiary structure – when further folding of the
protein forms a globular molecule
 Quaternary structure – when two or more
polypeptide chains go together to form a
functional protein
37
Organic Substances:
Proteins
Primary structure
Secondary
Myoglobin
Hemoglobin, Antibodies
Tertiary
Quaternary
38
Organic Substances:
Proteins
 Dehydration reactions join amino acids together –
water is removed
 Hydrolysis reactions separate amino acids by
adding water
H
C
H
C
H
C
C
H
C
H
H
S
R
H
N
C
C
H
H
O
OH
H
C
H
C
H
N
C
C
H
H
O
OH
H
H
C
H
N
C
C
H
H
O
OH
39
Organic Substances:
Nucleic Acids
 Carry genes
 Encode amino acid sequences of proteins
 Building blocks are nucleotides
 Make up DNA (deoxyribonucleic acid) –
double polynucleotide
 Make up RNA (ribonucleic acid) – single
polynucleotide
40
Organic Substances:
Nucleic Acids
Nucleotides are composed of:
a. nitrogenous base (adenine, guanine, cytosine,
thymine, uracil)
b. phosphate group
c. pentose sugar (ribose or deoxyribose)
P
B
S
41
Organic Substances:
Nucleic Acids
RNA
DNA
 Single helix
 Double helix
 Sugar – ribose
 Sugar – deoxyribose
 Bases – adenine, cytosine,
 Bases – adenine, cytosine,
guanine, and uracil
guanine, and thymine
42
Organic Substances:
Nucleic Acids
Base pairs are held together by hydrogen bonds.
P
B
S
P
B
B
B
B
B
B
B
B
P
P
S
B
S
P
S
P
S
B
S
P
S
P
S
B
S
P
S
(a)
B
S
P
S
P
B
P
S
B
P
B
S
P
S
P
B
S
B
P
S
P
S
(b)
P
43
Metabolism
 Anabolism
 Dehydration synthesis reactions
 Joining together of simple molecules to form
more complex biomolecules
 Water is removed
 Requires energy
 Catabolism
 Hydrolysis decomposition reactions
 Breaking apart of complex biomolecules to form
simple molecules
 Water is added
 Releases energy
44
Organic Substances: Combined Forms
 ATP (adenosine triphosphate)
 Two extra phosphate groups are added to an
adenine-containing RNA nucleotide
 Transfers energy from one chemical pathway to
another
45
ATP
46