Chemistry
Lecture 2
Overview
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Energy and matter
Atoms, molecules, and chemical bonds
Importance of organic and inorganic
nutrients and metabolites
Structure and function of carbohydrates,
lipids, proteins, and nucleic acids
Enzymes and ATP help run the metabolic
reactions of the body
Energy


The capacity to do work (put matter into
motion)
Types of energy


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Kinetic – energy in action
Potential – energy of position; stored (inactive)
energy
Energy is easily converted from one form to
another
During conversion, some energy is “lost” as
heat
Why is chemistry important to
anatomy and physiology?
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Chemistry is the science that deals
with matter
Matter is anything that takes up space
and has mass
Smallest stable units of mass are
atoms
Elements vs. Molecules
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Elements are atoms of one particular
type (from the periodic table)
Molecules are groups of atoms that
contain more than one element
Elements found in the body
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13 principal elements
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Oxygen (O)
Carbon (C)
Hydrogen (H)
Nitrogen (N)
Calcium (Ca), phosphorus (P), potassium (K),
sulfur (S), sodium (Na), chlorine (Cl),
magnesium (Mg), iodine (I), and iron (Fe)
13 trace elements

(e.g. zinc, manganese)
Elements with unfilled electron
shells are reactive

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To become stable they form chemical
bonds.
Three main types of chemical bonds

Intramolecular:
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
Ionic bonds (charged atoms resulting from
the gain or loss of electrons)
Covalent bonds (electrons are shared)
Intermolecular

Hydrogen bonds
Ionic and covalent bonds
Molecules: atoms held together by
covalent bonds
 Salts: molecules held together by ionic
bonds
Q: What are the strongest type of bonds?

Importance of water
The body is mostly water (~2/3rds of
total body weight) so all chemical
reactions in the body occur in water
Covalent bonds are much stronger than
ionic bonds in water
Water properties
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Water can dissolve organic and
inorganic molecules making a solution
Water is needed for chemical reactions
Water can absorb and retain heat
Water is an effective lubricant
Water properties

Water has all these amazing properties
due to their ability to form hydrogen
bonds
Hydrogen bonds: weak bonds
between molecules
Mixtures and Solutions

Mixtures – two or more components
physically intermixed (not chemically
bonded)

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Solutions – homogeneous mixtures of
components
Colloids (emulsions) – heterogeneous mixtures
whose solutes do not settle out
Suspensions – heterogeneous mixtures with
visible solutes that tend to settle out
Essential Molecules

Nutrients:

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essential molecules obtained from food
(you have to eat them to get them)
Metabolites:

molecules made or broken down in the
body
Organic vs. inorganic
Organic molecules:
 Always contain carbon with hydrogen, and
sometimes oxygen
 Often soluble in water
Inorganic: Electrolytes, minerals, and
compounds that do not contain carbon with
hydrogen.
 Important examples: oxygen, carbon
dioxide, water, inorganic acids and bases,
salts
Vitamins and Minerals
Vitamins and minerals are essential
nutrients that are required in very small
amounts for healthy growth and
development.
Examples?
 They cannot be synthesized by the
body and are essential components of
the diet.
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Vitamins
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Organic substances necessary for
metabolism
There are 13 known vitamins (e.g. A,
B1, D, K)
Some are fat soluble while others are
water soluble
Are Coenzymes that help carry out
the reactions of metabolism
Minerals
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Inorganic compound (often salts or
elements) necessary for proper body
function
Can be bulk or trace minerals
Are Cofactors in metabolic reactions
Electrolytes
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Inorganic ions (usually minerals) that
conduct electricity in solution
Electrolyte balance is maintained in all
body fluids; imbalance seriously disturbs
vital body functions
Electrolytes
Table 2–3
Biological Macromolecules

Life depends on four types of organic
macromolecules:
1. Carbohydrates
2. Lipids
3. Proteins
4. Nucleic acids
Can you think of an example of each?
1. Carbohydrates
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Contain carbon, hydrogen and oxygen
in a ratio of 1:2:1
Account for less that 1% of body
weight
Used as energy source
Called saccharides
Glucose is a monosaccharide
Disaccharides
Sucrose
Lactose
Polysaccharides
Starch
 Glycogen
 Cellulose
All are long strings of glucose molecules
Difference lies in how they are bonded
together
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Polysaccharides
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PLAY
Polysaccharides or polymers of simple
sugars
Polysaccharides
Figure 2.14c
Polymers

A polymer is any molecule made up of
several repeating units. Starch is a
polymer of glucose.
2. Lipids
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Contain carbon, hydrogen, and oxygen
but the ratio of C:H is 1:2 (much less
O)
May also contain other elements,
phosphorous, nitrogen, and sulfur
Form essential structures in cells
Are important energy stores
Lipids: Triglycerides (Fats and
Oils)

Consist of 3 fatty
acids and glycerol
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Insulation
Energy
protection
Q: What ‘s the
difference
between
saturated and
unsaturated?
Lipids: Steroids and
Cholesterol
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All consist of a
complex ring
structure
Lipids: Phospholipids
Amphipathic
3. Proteins
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Consist of chains of
amino acids liked
together by peptide
bonds
Enzymes are
proteins
Protein Structure
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Proteins are the most abundant and
important organic molecules
Basic elements:
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carbon (C), hydrogen (H), oxygen (O),
and nitrogen (N)
Basic building blocks:

20 amino acids
Protein Structure – 4 levels
Primary: amino acid sequence
Secondary: Hydrogen bonds form spirals
or pleats
Tertiary: Secondary structure folds into a
unique shape
Quaternary: several tertiary structures
together
Figure 2–20a
Protein structure
Shape and Function
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Protein function is based on shape
Shape is based on sequence of amino
acids
Denaturation:

loss of shape and function (due to heat,
pH change or other factors)
Protein Functions
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support:
 structural proteins
movement:
 contractile proteins
transport:
 transport proteins
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buffering:
regulation of pH
metabolic
regulation:
 enzymes
coordination and
control:
 hormones
defense:
 antibodies
Proteins: Enzymes
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Enzymes are catalysts:
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proteins that lower the activation energy of a
chemical reaction
are not changed or used up in the reaction
Other factors that speed up reactions:
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Increased temperatures
Smaller particles
Higher concentrations
Activation Energy
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Chemical reactions in cells cannot
start without help
Activation energy gets a reaction
started
Figure 2–7
Characteristics of Enzymes
Figure 2.20
Energy In, Energy Out
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Exergonic reactions:

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produce more energy than they use
Endergonic reactions:

use more energy than they produce
KEY CONCEPT

Most chemical reactions that sustain
life cannot occur unless the right
enzymes are present
How Enzymes Work
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Substrates:


reactants in enzymatic reactions
Active site:

a location on an enzyme that fits a
particular substrate
Active site
Amino acids
+
How
Enzymes
Work
Enzyme (E)
Substrates (S)
Enzyme-substrate
complex (E-S)
H2O
Free enzyme (E)
Peptide bond
Internal rearrangements
leading to catalysis
Figure 2–21
Dipeptide product (P)
4. Nucleic acids
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Contain C, H, O, N,
and P
DNA and RNA are
nucleic acids
Nucleotide consists
of

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
Sugar
Phosphate group
Nitrogenous base
Structure of
DNA
Figure 2.22b
A nucleotide: ATP
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Energy storage for
cells
Many enzymes use
ATP
Provides a way to
run reactions that
are otherwise
endergonic
(require energy)
Membrane
protein
Pi
P
Solute
ATP is the
energy currency
of the cell
Solute transported
(a) Transport work
ADP
+
Pi
ATP
Relaxed smooth
muscle cell
Contracted smooth
muscle cell
(b) Mechanical work
Pi
X
P
X
Y
+ Y
Reactants
Product made
(c) Chemical work
Figure 2.24
Compounds Important
to Physiology
Table 2–8
Summary


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

Energy and matter
Atoms, molecules, and chemical bonds
Importance of organic and inorganic
nutrients and metabolites
Structure and function of carbohydrates,
lipids, proteins, and nucleic acids
Enzymes and ATP help run the metabolic
reactions of the body