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Chemical Constituents
of Cells
Organic v. Inorganic Molecules
Organic molecules
• Contain C and H
• Usually larger than inorganic molecules
• Dissolve in water and organic liquids
• Carbohydrates, proteins, lipids, and nucleic acids
Inorganic molecules
• Generally do not contain C
• Usually smaller than organic molecules
• Usually dissociate in water, forming ions
• Water, oxygen, carbon dioxide, and inorganic salts
1
Chemical Constituents
of Cells
Organic v. Inorganic
Molecules
2
Inorganic Substances
Water
• Most abundant compound in living material
• Universal Solvent
• Many solutes are dissolved in our body’s water
• Many ionic compounds (NaCl) dissociate or break apart in water
• Participates in many chemical reactions (cells and fluid)
• Dehydration (synthesis) – water is removed from adjacent atoms to
form a bond between them.
• Hydrolysis (degradation) – water is used to break bonds between
molecules.
•Water is an excellent temperature buffer
• Absorbs and releases heat very slowly
•Water provides an excellent cooling mechanism
• It requires a lot of heat to change water from a liquid to a gas. If water
does change form and evaporates, it leaves a cool surface behind.
3
Inorganic Substances
Water (Cont)
•Water serves as a lubricant
• Mucus, joints and internal organs.
•Two-thirds of the weight of an adult human
• Major component of all body fluids (about 70%)
• Medium for most metabolic reactions
• Important role in transporting chemicals in the body
Oxygen (O2)
• Used by organelles to release energy from nutrients
in order to drive cell’s metabolic activities
• Necessary for survival
•Gas that is transported in the blood.
4
Inorganic Substances
Carbon dioxide (CO2)
• Waste product released during metabolic reactions
• Must be removed from the body
Inorganic salts
• Abundant in body fluids
• Sources of necessary ions (Na+, Cl-, K+, Ca2+, etc.)
• Play important roles in metabolism
5
Organic Substances
• Contains the atoms carbon (and hydrogen)
• Small molecules (monomers or building blocks) are
covalently bonded
•Together to form large polymers or macromolecules
•Water is usually involved in the formation and breakage of
bonds between monomers.
•Dehydration synthesis – removal of water to form a covalent
bond
between monomers;
•Hydrolysis – using water to break bonds between monomers.
6
(a)
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
(b)
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
(c)
Example reactions
Dehydration synthesis of sucrose and its breakdown by hydrolysis
Water is
released
+
Water is
consumed
Glucose
Copyright © 2010 Pearson Education, Inc.
Fructose
Sucrose
Monomer 2
Organic Substances
• Four major classes found in the cells include;
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids
8
Organic Substances
Carbohydrates (Sugars)
• Provide energy to cells
• Supply materials to build cell structures
• Water-soluble
• Contain C, H, and O
• Ratio of H to O close to 2:1 (C6H12O6)
• Monomers (building blocks)
• Monosaccharides – glucose, fructose, galactose
• Disaccharides ( 2 monosaccharides covalently bonded together):
maltose = glucose + glucose
sucrose = glucose + galactose
lactose = glucose + frutose
• Polysaccharides – many glucose molecules covalently bonded
together.
Glycogen = animal storage carbohydrate; stored in liver
and skeletal muscles
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Cellulose = starch/ plant storage carbohydrate
Organic Substances
Carbohydrates (Sugars)
•Function = energy storage/energy source
• How is the energy that is stored in carbohydrates release?
• CELLULAR RESPIRATION OVERVIEW
oxygen
↓
glucose → H2O + CO2
↓
energy (ATP)
10
Organic Substances
Carbohydrates
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H
O
C
H
H
C
O
O
C
H
H
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
H
H
C
O
H
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
H
C
O
H
H
C
O
H
H
C
O
H
H
(a) Some glucose molecules
(C6H12O6) have a straight
chain of carbon atoms.
O
C
H
C
H
O
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.
11
Organic Substances
Carbohydrates
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
O
O
O
O
(b) Disaccharide
(a) Monosaccharide
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O
O
O
(c) Polysaccharide
12
Organic Substances
Lipids
• Soluble in organic solvents; insoluble in water
•Types
• Fats (triglycerides)
•Used primarily for energy; most common lipid in the body
• Contain C, H, and O but less O than carbohydrates (C57H110O6)
• Building blocks are 1 glycerol and 3 fatty acids per molecule
• Saturated
•
•
•
•
Have only single bonds between carbons in their fatty acid chains
Are solid at room temperature
Are animal fats
Are nutritionally “BAD” fat
•Unsaturated
• Have one or more double bond between the carbons in their fatty acid
chains
• Are liquid at room temperature - oils
• Are plant fats
• Are nutritionally “GOOD” fat
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Organic Substances
Lipids
• Fats (triglycerides)
•Trans fats
•
•
•
•
Unsaturated fats that have been solidified by artificial means
Not produced nor maintained in the body
Include margarine
The WORST type of fat
•Function = energy storage/energy source
H
H
H
H
C
C
C
O
O
O
H
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
O
H
H
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
C
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
O
H
H
H
H
H
H
C
C
C
C
C
C
H
H
H
H
H
H
H
14
Glycerol
portion
Fatty acid
portions
Organic Substances
Lipids
• Phospholipids
• Building blocks are 1 glycerol, 2 fatty acids, and 1 phosphate per
molecule -Triglyceride with the substitution of a polar phosphate group
(PO4) for one fatty acid
• Hydrophilic and hydrophobic
• Function = Major component of cell membranes
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H
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
H
H
C
O
Fatty acid
H
C
O
Fatty acid
H
C
O
Fatty acid
H
Glycerol portion
(a) A fat molecule
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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
15
Organic Substances
Lipids
• Steroids
• Four connected rings of carbon
• Widely distributed in the body, various functions
• Function = Component of cell membrane; Used to
synthesize hormones
• Cholesterol
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
H2
C
C
H
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
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(a) General structure of a steroid
(b) Cholesterol
Organic Substances
Proteins
• Amino Acid Structure
• Protein building blocks are
•Amino group
amino acids
•R group
• Amino acids held
•Carboxyl group
together with peptide bonds
•Types of amino acid
H
20 different based on R-groups or
C
H C
C H
H
side chains
H C
C H
S
R
H
N
C
C
H
H
O
OH
(a) General structure of an amino
acid. The portion common to all
amino acids is within the oval.
It includes the amino group
(—NH2) and the carboxyl group
(—COOH). The "R" group,
or the "rest of the molecule,“
is what makes each amino
acid unique.
H
C
H
C
H
N
C
C
H
H
O
OH
(b) Cysteine. Cysteine has an
R group that contains sulfur.
H
H
C
H
N
C
C
H
H
O
OH
Phenylalanine. Phenylalanine
has a complex R group.
Improper metabolism of
phenylalanine occurs in the
disease phenylketonuria.
17
Organic Substances
Proteins
Function of Proteins
• Structural material
•Keratin in hair, nails, and
skin
• Transport
•hemoglobin
• Chemical Messengers
•Hormones
•Neurotransmitters
•Movements
•Actin and myosin in muscle
•Catalysts
•Enzymes
• Protein building blocks are
amino acids
• Amino acids held
together with peptide bond
•Length of amino acid change may
vary;
•Peptide = 2-100 aa’s
•Polypeptide = 100 –thousands of
aa’s with a function
•Protein = 100-thousands of aa’s
with a specific function.
•Defense
•Antibodies
18
Organic Substances
Proteins
Four Levels of Protein Structure
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Amino acids
H
(a) Primary structure—Each
oblong shape in this
polypeptide chain represents
an amino acid molecule. The
whole chain represents a
portion of a protein molecule.
H
(c) Tertiary structure—
The pleated and coiled
polypeptide chain of a
protein molecule folds
into a unique threedimensional structure.
C
(b) Secondary structure—The
polypeptide chain of a protein
molecule is often either pleated
or twisted to form a coil. Dotted
lines represent hydrogen bonds.
R groups (see fig. 2.17)
are indicated in bold.
H
N
C
H
C
O
C
R
N
O
C
H
H
H
R
R
H
H
N
O
C
R
N
C
H H
H
Pleated
structure
N
N
C
H
R
C
C
O
N
H
H
O
C
H
H
H
N
C
O
H
R
H
C
N
R
H
C
Coiled
structure
O
HO
H
O
H
N
C
N
C
C
C
O
R
N
C
C
H
C
H
H
R
R
C
O
C
R
C
C
C
O
N
R
H
N
N
N
C
C
H O
H
C
O
N
R
C
HO
R
R
C
H
C
H
C
Three-dimensional
folding
H
C
H
H
C
C
O
O
N
O
C
H
C
H
H
R
C
H
R
(d) Quaternary structure—Two or
more polypeptide chains may be
connected to form a single
protein molecule.
H
C
N
H
O
19
Protein Denaturation
The loss of 3-dimensional conformation (shape) of a protein.
The results in loss of function.
•
Reasons for denaturation;
•Extreme pH values
•Extreme temperature values
•Harsh chemicals (disrupt bonding)
•High salt concentrations
20
Animation:
Protein Denaturation
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21
Organic Substances
Nucleic Acids
• Carry genes
• Encode amino acid sequences of proteins
• Building blocks are nucleotides – 3 parts
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P
B
S
• DNA (deoxyribonucleic acid) – double polynucleotide
• RNA (ribonucleic acid) – single polynucleotide
22
Organic Substances
Nucleic Acids
• Carry genes
• Encode amino acid sequences of proteins
• Building blocks are nucleotides – 3 parts
•Pentose sugar (5-C)
•Nitrogenous base
•Phosphate group
P
B
S
23
Organic Substances
Nucleic Acids
• DNA (deoxyribonucleic acid) – double polynucleotide
•Structure:
•Sugar deoxyribose
•Base – adenine (A), thymine (T), cytosine (C), guanine (G)
•Double stranded; strands held together by H-bonds
between bases on the opposite strands;
•A complements T (2 hydrogen bonds)
•C complements G (3 hydrogen bonds)
•Function = genetic material
•DNA directs protein synthesis
• DNA contains all necessary information needed to sustain and
• reproduce life
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Organic Substances
Nucleic Acids
• RNA (ribonucleic acid) – double polynucleotide
•Structure:
•Sugar = ribose
•Base – adenine (A), cytosine (C), guanine (G), uracil (U)
(replaces thymine),
•Function = transport DNA code during protein systhesis
•DNA directs protein synthesis
25