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Welcome to Biology 121
“Concepts of Biology”
Fall 2015
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Page numbers correspond to the 3rd,4th & 5th edition of our text.
WHAT IS BIOLOGY?
 Biology is the study of living Organisms
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Life at its Many Levels (p.17)
 The universe (and life) show levels of organization
from simple to complex, small to large:
* Some whole organisms are single-celled (bacteria, yeast) & thus “skip”
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the tissue, organ, & system levels.
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Unity of Life: Common Characteristics
of all Living Things (p. 7)
What characterizes living things?
DNA: basis of Inheritance & reproduction.
Obtain, process, & use energy via metabolism.
Sense & respond to changes in environment.
 Maintain homeostasis: “A state where the internal
environment is maintained within a range life can
tolerate”.
 Reproduce
 Evolve (change) over generations (p. 10).
 Evolution: 'Life's Unifying Theme' --all life shares a
common ancestry (p. 10-12)
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Modern Biology Stands on 4 Key
Scientific theories:
1) The Cell theory:
 All organisms composed of 1 or more cells, etc.
 Basis for our understanding of cells, tissues, organs, growth,
reproduction, etc.
2) The Central Dogma:
 Basis of heredity: Information stored in DNA, transcribed to
RNA & used to generate proteins (= the 'drivers' of biological
activity).
3) The Theory of Evolution by Natural Selection:
 Biological populations change (evolve) when genetic variability
provides some individuals a higher chance of survival &
reproduction in their particular environment.
 Explains biological diversity & ecological interactions.
4) The Ecosystem Concept:
 Living organisms interact with each other & their environment
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to form ecosystems.
WHAT IS BIOLOGY?
 Biology is the study of living organisms
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The Process of Science p. 4-7 (14-16)
 Scientific Methods: Logical, repeatable approaches to
explaining nature.
 “Evidence-based thinking”
 Observe aspect of nature & ask a question.
 Develop a hypothesis (tentative answer).
 Using hypothesis, make a prediction.
 Test prediction with experiments, observations,
models, etc; evaluate & analyze results.
 Objectively report results & conclusions.
 Scientific theory: An accepted body of knowledge
derived from multiple hypotheses that have withstood
many testings.
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Part 1: The Cell Theory
Chapters 2 & 3: Life’s Chemical Basis
What are cells made of?
Atoms (p 25).
Atomic nucleus:
 protons (positive charge).
 neutrons (no charge).
Electrons:
 Suround atomic nucleus.
 negative charge.
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Molecules:
 2 or more atoms that have reacted & bonded
together (p. 27).
 Various types of chemical bonds may form
between atoms:
O
H
H
A water molecule: 2 hydrogens bonded to oxygen
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Important Chemicals for Life
 Water: 2-hydrogens & 1-oxygen.
 majority of living matter (p. 29-31) .
 Other “inorganic” molecules
 ions + or – charged (have gained or lost electrons).
 Salts (release ions when dissolved)
 Others (acids, bases, etc) p. 31-32.
 Organic molecules (carbon-based): Chapter 3
 Many kinds, often large, & elaborate
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Organic Molecules: The Molecules of
Life (Ch. 3)
 Carbon-based molecules (p. 38):
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Carbon "backbone"
Hydrogen
Other elements (O, N, S, P, etc.)
4 main types
Hydrogen
HHHHH
O=C-C-C-C-C-H
HHHH
Other elements
(often O, N, P, or S)
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Carbon “backbone”
Carbon’s Versatile Bonding Behavior:
(p. 38)
 Carbon can form 4 different bonds:
 Result: Complex structures are possible:
Glucose
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Giant Molecules from Smaller Building
Blocks: Polymerization (p. 39)
 Cells often link many small organic molecules together:
 Monomers: basic subunits.
 Polymers: large molecule chains composed of many
monomers.
dehydration
reaction
LEU
LYS
GLT
Monomers
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LEU
GLT
hydrolysis
reaction
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LYS
LYS
Polymer
LEU
A LA
Organic Molecules: Carbohydrates (p. 40)
 Most abundant organic in nature.
 (Carbon, Hydrogen, oxygen in 1:2:1 ratio)
 Exist as simple sugars or as polymers.
 Simple sugars:
 3-carbon sugars (glyceraldehyde)
 Pentoses (5C) (ribose)
 Hexoses (6C) (glucose, fructose)
 Uses: Energy source, building blocks for other
molecules.
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Carbohydrates:
 Disaccharides: 2 linked simple sugars (p. 41).
 Sucrose (=table sugar): Nature’s most plentiful sugar!
 Polysaccharides: (p. 42)
 (many sugars in a polymer)
 Starch: Plant food storage.
 Glycogen: Animal food storage.
Part of a polysaccharide
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Structural Polysaccharides
 Cellulose:
 Plant cell walls (p.41)
 Chitin:
 External skeletons of some
animals (insects, etc).
 Fungal cell walls.
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Centipede: Chitinreinforced body.
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Wood: Contains
cellulose
Fungus: Chitin cell
walls.
Lipids (p. 43):
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Greasy/ oily; not soluble in water
Mostly just carbon & hydrogen.
Functions:
 Energy storage (more than 2x energy/gram than
carbohydrates).
 Cell membranes.
 Certain hormones.
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Types of Lipids:
 Fats and oils (p. 43-44):
 Structure: 3 fatty acids + glycerol (= Triglyceride)
 Saturated (no double bonds) vs. saturated
 Important for energy storage.
Saturated fatty acid
Unsaturated fatty acid
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Types of Lipids (Continued):
Steroids: (p. 45).
 stabilize membranes (Cholesterol, etc)
 steroid hormones.
Waxes: repel water, lubricate.
Phospholipids: (p. 60; chapter. 4).
 2 fatty acids + 1 phosphate + glycerol
 Important part of cell membranes
Water soluble
Not water soluble
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Proteins & Amino Acids (p. 46):
 Amino acids (p. 46):
 Small organic molecules,
contain nitrogen
 20 types.
Some of the 20 Amino Acids
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Proteins (p. 47)
 Polymers of amino
acids (p. 47).
 Interacting chemical
properties of amino
acids cause a protein to
coil & fold into a specific
3-D shape (p. 48).
 A protein's 3-D shape
determines it’s function.
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Hemoglobin: the oxygen transport protein
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of blood.
Proteins: the Most Diverse Organic
Molecules (p.46):
 Structural Proteins: “The stuff of spider webs or
feathers, bone, hair & other body parts”.
 Enzymes: Enable (speed up) biochemical reactions.
 Nutritious (storage) proteins: seeds, eggs, etc.
 Transport proteins: transport substances in cells.
 Contractile proteins: Movement, muscles!
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Metabolism is Controlled by Proteins!
Metabolism:
 The Cell's many chemical reactions.
Metabolic pathway:
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An orderly series of reactions:
Each step mediated by a particular enzyme (p. 46)
Thousands of metabolic pathways the body.
 Thousands of enzymes needed!
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Enzymes: Catalyze Biochemical
Reactions in Cells (p. 80-82 in Ch 5)
 3-D shape is important for enzyme function.
 Lock and Key model (p.82):
substrate
Enzyme
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Product
Enzyme - substrate
complex
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Nucleotides & Nucleic Acids (p. 49)
 Nucleotides: Small organic molecules with a
phosphate* + a 5-C sugar + a nitrogen-containing
base.
 Functions:
 Building blocks for DNA & RNA (p. 49-50).
 Energy carrier: ATP.
Base (with N)
 Others.
Phosphate
Sugar
* Phosphate: a chemical group that
contains the element phosphorus
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Diagram of a nucleotide
ATP: The Cell’s Energy Battery
(p. 79-80 in Ch. 5)
Problem: Many reactions require energy.
Solution: Couple them with an energy-releasing reaction!
1. Cells use respiration (= fuel consumption) to release
energy.
2. This energy used to make ATP.
p
p
p
ATP
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Doing Cellular Work With ATP (P. 79-80)
3. The ATP/ ADP cycle:
Phosphates
p
p
p
ATP
Respiration
p
p
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Released energy,
biochemical work
p
ADP
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Nucleic Acids: Polymers of
Nucleotides (P. 49-50)
 DNA
 2 antiparallel strands made of 4 types of nucleotides.
 Nucleotide bases “pair” with those on opposite strand.
 Double helix (spiral).
 Combinations of thousands of base-pairs store genetic
information: Blueprint for cell’s proteins.
 RNA
 Single strand of nucleotides
 Several types; Transmit DNA instructions to cell.
3´
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5´
A
T
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G
C
T
A
C
G
3´
5´
The End
Version 15.09
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