Download The Nature of Life

The Nature of Life
•Some properties of life
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Life Displays Order
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Life Uses Energy
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•Energy flows through an ecosystem
• Usually entering as sunlight and exiting as heat
Sunlight
Ecosystem
Producers
(plants and other
photosynthetic
organisms)
Heat
Chemical
energy
Consumers
(including animals)
Figure 1.4
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Heat
A Closer Look at Cells
•The cell
• Is the lowest level of organization that can
perform all activities required for life
• all enclosed by a membrane
• all use DNA as genetic information
Figure 1.5
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25 µm
Outer membrane
and cell surface
CELL
Cytoplasm
Nucleu
s
Figure 1.10
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Carbon-based Life
•Essential elements
• Include carbon,
hydrogen, oxygen, and
nitrogen
• Make up 96% of living
matter
•A few other elements
•Make up the remaining
4% of living matter
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Carbon is Special
•The backbone of
biological molecules
•All living organisms are
made up of chemicals
based mostly on this one
element --> organic
chemistry
•The bonding versatility of
carbon allows it to form
many diverse molecules,
varying in length and
shape
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Molecular Components of Cells
•Carbohydrates
• food energy, sugars and starches
• structure (cellulose)
•Lipids/fats
• Can store energy
• Major ingredient in cell membranes
•Proteins
• Work-horses of cells
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Proteins
Proteins have many roles inside the cell
•Some serve as structural elements
•Enzymes serve as catalysts to biochemical
reactions in cell
•Built from amino acids
•organic molecules possessing both amino
group [N bonded to 2 H and 1 C] and carboxyl
group [COOH]
•Differ in their properties due to differing side
chains, called R groups
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Enzymes
• Are a type of protein that acts as a catalyst,
speeding up chemical reactions
1 Active site is available for
a molecule of substrate, the
reactant on which the enzyme acts.
Substrate
(sucrose)
2 Substrate binds to
enzyme.
Glucose
OH
Enzyme
(sucrase)
H2O
Fructose
H O
4 Products are released.
Figure 5.16
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3 Substrate is converted
to products.
Proteins
Proteins have many roles inside the cell
•Some serve as structural elements
•Enzymes serve as catalysts to biochemical
reactions in cell
•Built from amino acids
•organic molecules possessing both amino
group [N bonded to 2 H and 1 C] and carboxyl
group [COOH]
•Differ in their properties due to differing side
chains, called R groups
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Amino Acid Monomers
• 20 different amino acids make up proteins
CH3
CH3
H
H3N
+
C
CH3
O
H3N+
C
H
Glycine (Gly)
O
C
H3N
+
C
–
H
Alanine (Ala)
O
C
CH2
O
H3N
+
C
–
H
Valine (Val)
CH2
CH
CH3
CH3
O
CH3
CH3
O
C
H3C
O
H3N
C
–
H
Leucine (Leu)
+
O
CH
C
O
C
–
H
Isoleucine (Ile)
O–
Nonpolar
CH3
CH2
S
NH
CH2
CH2
H3N+
C
H
CH2
O
H3N+
C
O–
Methionine (Met)
C
H
H3N+
C
O–
Phenylalanine (Phe)
Figure 5.17
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CH2
O
C
H
O
H2C
CH2
H2N
C
O
C
H
C
O–
Tryptophan (Trp)
Proline (Pro)
O–
OH
OH
Polar
CH2
H3N
+
C
CH
O
H3N+
C
C
O–
H
Serine (Ser)
CH2
O
H3N+
C
O–
H
C
CH2
O
C
H
H3N
C
+
O–
CH2
O
H3N
+
C
Electrically
charged
H3N+
O
O–
NH3+
O
CH2
C
CH2
CH2
CH2
CH2
CH2
CH2
CH2
O
C
H3N
+
C
O
CH2
C
H
O–
H3N+
C
H
Aspartic acid
(Asp)
O–
C
O
C
O–
H
Glutamine
(Gln)
NH2
C
H
H3N
C
Asparagine
(Asn)
C
O–
CH2
+
Basic
O
C
CH2
O
H
Acidic
–
C
O–
H
Tyrosine
(Tyr)
Cysteine
(Cys)
Threonine (Thr)
C
NH2 O
C
SH
CH3
OH
NH2 O
Glutamic acid
(Glu)
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NH2+
Lysine (Lys)
–
H3N+
C
H
C
H
CH2
C
NH
CH2
H3N+
CH2
O
O
NH+
O
C
O–
O
C
O–
Arginine (Arg)
Histidine (His)
Nucleic Acids
• Nucleic acids store and transmit hereditary
information
• Genes
• Are the units of inheritance
• Program amino acid sequences
• Are made of nucleic acids
•There are two types of nucleic acids
•Deoxyribonucleic acid (DNA)
•Ribonucleic acid (RNA)
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DNA Stores Information
• Set of operating
instructions for cell directs RNA synthesis
and protein synthesis
through RNA
• Way of passing down
information through
generations
DNA
1
Synthesis of
mRNA in the nucleus
mRNA
NUCLEUS
CYTOPLASM
mRNA
2 Movement of
mRNA into cytoplasm
via nuclear pore
3
Figure 5.25
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Ribosome
Synthesis
of protein
Polypeptide
Amino
acids
The DNA Double Helix
• Cellular DNA molecules
• Have two 'zipper edges' that spiral around an
imaginary axis
• Form a double helix backbone
•The base sequence of 'zipper teeth'
•Adenine (A), guanine (G), thymine (T), cytosine
(C)
•unique for each gene
•The bases in DNA form bonds in a
complementary fashion (A with T only, C with G
only)
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• The DNA double helix
• Consists of two anti-parallel nucleotide strands
5’ end
3’ end
Sugar-phosphate
backbone
Base pair (joined by
hydrogen bonding)
Old strands
A
3’
end
Nucleotide
about to be
added to a
new strand
5’ end
3’ end
Figure 5.27
5’ end
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New
strands
3’ end
Nucleus
DNA
Cell
A
C
Nucleotide
T
A
T
A
C
C
G
T
A
G
T
A
Figure 1.7
(a) DNA double helix. This model shows
each atom in a segment of DNA.Made
up of two long chains of building
blocks called nucleotides, a DNA
molecule takes the three-dimensional
form of a double helix.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
(b) Single strand of DNA. These geometric shapes and
letters are simple symbols for the nucleotides in a
small section of one chain of a DNA molecule.
Genetic information is encoded in specific sequences
of the four types of nucleotides (their names are
abbreviated here as A, T, C, and G).
• DNA replication – 'unzipping' of two strands to
make new, complementary strand
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The “Book” of DNA
Level
Base pair
Codon
Gene
Bacterium
Human
Atoms
Bits
10
100
10,000
10,000,000
3,000,000,000
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1
6
1000
1,000,000
6,000,000,000
Language analog
Letter
Word
Sentence
Short book
Encyclopedia
•The Genetic Code
•Uses a four “letter” alphabet with specific
pairing rules
•Contains redundancy because 4 x 4 x 4
codons could specify 64 amino acids
•Does not require perfect fidelity in copying
because of cross-checking elsewhere
•Extends to the huge information content of 3
billion base pairs and 25,000 genes (in humans)
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The Genetic Code
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Now...
•The Modern Tree of Life
•Maps evolution via the gradual deviation of
the base pair sequences in DNA or RNA
•Shows relationships between species
•Does not depend on identifying or recognizing
distinct species
•True diversity of life found almost entirely
within microscopic realm
•WORK IN PROGRESS!
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The Modern Tree of Life
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Three Domains of Life
•At the highest level, life is classified into three
domains
• Bacteria
• Archaea
• Eukarya
•The “species” concept is tricky. Its normally
defined by the ability to reproduce (and by a
similar appearance) but many organisms can
clone or reproduce asexually, and microbes don’t
look very different from each other.
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• Life’s three domains
4 µm
Bacteria are the most diverse
and widespread prokaryotes
and are now divided among multiple
kingdoms. Each of the rod-shaped
structures in this photo is a bacterial cell.
DOMAIN ARCHAEA
Figure 1.15
Many of the prokaryotes known
0.5 µm
as archaea live in Earth‘s
extreme environments, such as salty lakes
and boiling hot springs. Domain Archaea
includes multiple kingdoms. The photo
shows a colony composed of many cells.
Protists (multiple kingdoms)
100 µm
are unicellular eukaryotes and
their relatively simple multicellular
relatives.Pictured here is an assortment of
protists inhabiting pond water. Scientists are
currently debating how to split the protists
into several kingdoms that better represent
evolution and diversity.
Kingdom Plantae consists of
multicellula eukaryotes that carry
out photosynthesis, the conversion
of light energy to food.
Kindom Fungi is defined in part by the
nutritional mode of its members, such
as this mushroom, which absorb
nutrientsafter decomposing organic
material.
Kindom Animalia consists of
multicellular eukaryotes that
ingest other organisms.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
•Domain Bacteria and domain Archaea
• Consist of prokaryotes, cells without nuclei
•Domain Eukarya, the eukaryotes
• Includes the various protist kingdoms and the
kingdoms Plantae, Fungi, and Animalia
•Simple, single-celled organisms or microbes
dominate life on Earth: 5000x more mass in
ocean microbes than all humans combined
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cells and Energy
• We know cells are the ingredients of life...
• And that they carry the instructions for life...
• But how do they MAKE
LIFE?
Light energy
ECOSYSTEM
• Cells need:
CO2 + H2O
• Materials
Photosynthesis
in chloroplasts
Cellular
respirationin
mitochondria
Organic
+ O2
molecules
• Energy
ATP
powers most cellular work
Figure 9.2
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Heat
energy
ATP
•Cells can build incredible
variety of molecules from limited
set of starting materials --> due
to enzyme variety and...
•ATP!
•Used to store and
release energy for nearly all
chemical manufacturing
•Once produced, can be
used to provide energy for
any cellular reaction
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ATP
Completely recyclable!
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Categorizing Life by Carbon and Energy
•Metabolism comes down to needing primary raw
material of life – carbon – and energy
• Carbon sources
• Eating = heterotroph
• Environment = autotroph
• Energy sources
• Sunlight = photo(synthesis)
• Organic compounds (food) = chemo• Neither = inorganic chemicals w/o C from
environment
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Categorizing Life by Carbon and Energy
•Liquid water is the final ingredient in metabolism
• Allows organics to float within cell --> readily
available for chemical reactions
• Medium of transport for chemicals to and within
cells, way to transport waste away
• Ingredient in many metabolic reactions within cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings