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ABCT 1101/ABCT1D04
Introductory Life Science

INTRODUCTORY LIFE SCIENCE
At our 3rd lecture, we want to discuss

• The building blocks of biological organisms
– Carbohydrates, proteins, lipids and nucleic acids

• Cell structure and function
– Cell membrane, ER, Golgi, cytoskeleton, nucleus
– Plant cell vs. animal cell

Simple Chemistry for Life Science
• Each element consists of one kind of atom.
– An atom is the smallest unit of matter that still
retains the properties of an element.

– An atom contains subatomic particles including
proton, neutron, and electrons.

2

Protons
Nucleus

2
2
Nucleus

Neutrons
Electrons

2e–
Electron cloud

Simple Chemistry for Life Science
• Atomic structure of the 4 common elements.
– The number of electrons in the outermost shell
determines the chemical properties of an atom
Electron

First electron shell
(can hold 2 electrons)

Hydrogen (H)
Atomic number  1

Outer electron shell
(can hold 8 electrons)

Carbon (C)
Atomic number  6

Nitrogen (N)
Atomic number  7

Oxygen (O)
Atomic number  8

Simple Chemistry for Life Science
• Chemical reactions enable atoms to give up or
acquire electrons, completing their outer shells.
• Chemical reactions usually result in atoms
– staying close together and
– being held together by attractions called chemical
bonds.

Examples of chemical bonds
Electron configuration

H

H

Hydrogen gas (H2)

O

O

Oxygen gas (O2)
H

H

C

H
Methane (CH4)

H

Structural formula

Space-filling model

Ball-and-stick model

Simple Chemistry for Life Science
• Twenty-five elements are essential to people.
• Four elements make up about 96% of the weight of
most cells:
– oxygen,
– carbon,

– hydrogen, and
– nitrogen.

© 2013 Pearson Education, Inc.

Simple Biochemistry for Life Science
• A cell is mostly water (H2O).

• The rest of the cell consists mainly of carbonbased molecules. • Carbon forms large, complex, and diverse
molecules necessary for life’s functions.
• Organic compounds are carbon-based
molecules.

Simple Chemistry for Life Science
Carbon (C): 18.5%

Oxygen (O):
65.0%
Calcium (Ca): 1.5%

Phosphorus (P): 1.0%
Potassium (K): 0.4%
Sulfur (S): 0.3%
Sodium (Na): 0.2%
Chlorine (Cl): 0.2%
Hydrogen (H):
9.5%

Nitrogen (N):
3.3%

Magnesium (Mg): 0.1%
Trace elements: less than 0.01%
Boron (B)
Chromium (Cr)
Cobalt (Co)
Copper (Cu)
Fluorine (F)
Iodine (I)
Iron (Fe)

Manganese (Mn)
Molybdenum (Mo)
Selenium (Se)
Silicon (Si)
Tin (Sn)
Vanadium (V)
Zinc (Zn)

Simple Biochemistry for Life Science
• Carbon can form an endless diversity of carbon skeletons varying in size and branching pattern.

Double bond
Carbon skeletons vary in length

Carbon skeletons may be unbranched
or branched

Carbon skeletons may have double bonds,
which can vary in location

Carbon skeletons may be arranged in rings

Simple Biochemistry for Life Science
• There are four categories of large biological
molecules:
– carbohydrates,
– lipids,
– proteins, and
– nucleic acids.

Large biological Functions
molecules

Carbohydrates

Components

Examples

Monosaccharides:
glucose, fructose;
Disaccharides:
lactose, sucrose;
Polysaccharides:
starch, cellulose

Dietary energy;
storage; plant
structure
Monosaccharide

Lipids

Proteins

Long-term
energy storage
(fats);
hormones
(steroids)

Enzymes,
structure,
storage,
contraction,
transport, etc.

Components of
a triglyceride

Side
group

Fats (triglycerides);
steroids
(testosterone,
estrogen)

Lactase
(an enzyme);
hemoglobin
(a transport protein)

Amino acid

Nucleic acids

Information
storage

T

Nucleotide

DNA, RNA

Carbohydrates
Functions

Components

Examples

Monosaccharides:
glucose, fructose:
Disaccharides:
lactose, sucrose:
Polysaccharides:
starch, cellulose

Dietary energy;
storage; plant...
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