lecture 1-concepts of life, cell theory and scientific method

7/21/2019 Lecture 1-Concepts of Life, Cell Theory and Scientific Method

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ology 11- Lecture 1- Concepts of Life, Cell

eory and Scientific Method

Concepts of Life

The Chemistry of Life

Scientific Method

This handout is for lecture use only and not

for commercial reproduction and

distribution.

Biology is the study of life

The Concept of Life

most contemporary biologists define life as a

particular set of processes that result from the

organization of matter

life resists a

simple, one-

sentence

definition, yet

we can

recognize life bywhat living

things do

Characteristics of All Forms of Life

Organization and

OrderReproduction

Growth and development

Energy

processing

Response to the

environment Metabolism/

Homeostasis Evolutionary adaptation

All forms of life share common

properties/characteristics

1. Organization and Orderthe highly ordered structure

that typifies life

2. Energy processingthe use of chemical energy to

power an organisms activities and chemical

reactions

3. Metabolism/Homeostasisan ability to control an

organisms internal environment

4. Response to the environment/Movementan

ability to respond to environmental stimuli

5. Reproductionthe ability of organisms to

reproduce their own kind

6. Growth and developmentconsistent growth and

development controlled by inherited DNA

7. Evolutionary adaptation variation, change and

adaptation


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1. Organization and Order

living things have a complex organization



characteristics of

life emerge from

an organisms

organization

Atom Smallest unit of an element composed ofelectrons, protons and neutrons

Molecule Union of two or more atoms of the same ordifferent element

Specialized structure composed of complex

molecules within a living cellOrganelle

Cell Structural and functional unit of livingthings; consists of organelles

Tissue Group of cells with common structure andfunction

Organ Group of tissues functioning together for aspecific task

Organ system Composed of several organs functioningtogether

Organism Individual containing organ systems

Population Organisms of the same species in aparticular area

Community Interacting populations in a particular area

Ecosystem Community plus the physical environment

Biosphere Regions of the Earths crust, water andatmosphere inhabited by living things

rganisms

rganization and

rder

Biosphere

Madagascar

Ecosystem:

Forest in

Madagascar

Community:

Allorganisms in

the forest

Population:

Groupofring -tailedlemurs

Organism:

Ring-tailedlemur

Organsystem:

Nervous system

Organ:

Brain

Tissue:

Nervous tissue

Nerve

Spinalcord

Brain

Organelle:

Nucleus

Cell:

Nerve cellNucleus Atom

Molecule:

DNA

characteristics of

life emerge from

an organismsorganization


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2. Metabolism and Homeostasis

Metabolism-

The chemical

processes

occurring within

a living cell or

organism that

are necessaryfor the

maintenance of

life.

Homeostasis-

ability or

tendency ofan

organism or cell to

maintain internal

equilibrium by

adjusting its

physiological

processes.

2. Metabolism and Homeostasis

3. Energy Processing

energy utilization

organisms take

in energy and

transform it to

do work

4. Reproduction

organisms produce their own kind

5. Growth and Development

heritable programs (DNA) direct pattern of

growth and development

5. Growth and Development


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6. Irritability and movement

capable of response to environmental stimulus

Irritability is a state of extreme sensitivity to stimulation of any kind.

7. Variation, change, and evolution


African wild

dogCoyote Fox Wolf Jackal

Thousands to

millions of years

of natural selection

Ancestral canine


6. Variation, change, and evolutionOrganization and Order Energy processing

Regulation/Homeostasis Response to the environment

Reproduction Growth and development

Evolutionary adaptation
http://www.ojibway.ca/harmonia2.jpg


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Living organisms obey chemical and physical laws

Organisms are composed of matter

Matter is made up of elements

Compound is a substance consisting of two or more

different elements combined in a fixed ratio

Atom is the smallest unit of matter

Molecule is the union of two or more atoms.

25 of the 92 natural elements are known to be

essential to life.

carbon (C), oxygen (0), hydrogen(H), and nitrogen

(N)-make up 96% of living matter.

Phosphorus (P), sulfur (S), calcium (Ca), potassium

(K), and a few other elements account for most of the

remaining 4% of an organism's

weight.


Chemistry of life is special

based on carbon compounds (organic chemistry)

70% water

depends largely on chemical reactions in aqueous solution

enormously complex

Small carbon-containing molecules, most of the carbon atoms in cells are incorporated

into enormous polymeric molecules.

Macromolecules enable cells and organisms to grow and reproduce as well as to do all

the other things that are characteristic of life.

Atom

The smallest unit of an element, consisting of at least one proton and

(for all elements except hydrogen) one or more neutrons in a dense

central nucleus, surrounded by one or more shells of electrons.

In electrically neutral atoms, the number of protons equals the number

of electrons.

Atoms remain intact in chemical reactions except for the removal,

transfer, or exchange of certain electrons.


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Comparison of covalent and ionic bonds. Atoms can attain a

more stable arrangement of electrons in their outermost

shell by interacting with one another. An ionic bond is

formed when electrons are transferred from one atom to

the other. A covalent bond is formed when electrons are

shared between atoms

Molecule: cluster of atoms held together by covalent bonds

Covalent and Noncovalent Chemical Bonds

STRENGTH (kcal/mole)

BOND TYPE LENGTH (nm) IN VACUUM IN WATER

Covalent 0.15 90 90

Noncovalent: ionic 0.25 80 3

hydrogen 0.30 4 1

van der Waalsattraction

(per atom)

0.35 0.1 0.1

van der Waals force-a weak force of attraction between electrically neutral

molecules that collide with or pass very close to each other. The attraction is much

weaker than a chemical bond.

Hydrogen bond- a chemical bond formed between an electropositive atom (typically

hydrogen) and a strongly electronegative atom, such as oxygen or nitrogen. Hydrogen

bonds are responsible for the bonding of water molecules in liquid and solid states, and

are weaker than covalent and ionic b onds.

Making and breaking of covalent bonds are violent events and in

living cells they are catalyzed by enzymes.

Noncovalent bonds as a rule are much weaker; important in

situations where molecules have to associate and dissociate

readily to carry out their functions.

Polar covalent bonds are extremely important in biology because

they create permanent dipoles that allow molecules to interact

through electrical forces.

Molecule

-a group of two or more atoms linked

together by sharing electrons in a

chemical bond.

-molecules are the fundamental

components of chemical compounds and

are the smallest part of a compound that

can participate in a chemical reaction.

Covalent

Noncovalent: ionic

hydrogen

van der Waalsattraction

(per atom)

Hydrogen bond

-a chemical bond formed between an

electropositive atom (typically hydrogen)

and a strongly electronegative atom,

such as oxygen or nitrogen.

-are responsible for the bonding of water

molecules in liquid and solid states, and

are weaker than covalent and ionic

bonds.

Four emergent properties of water

contribute to Earths fitness for life

Cohesion

Ability to moderate temperature

Expansion upon freezing

Versatility as a solvent

Cohesion -the force of attraction that

holds molecules of a given substance

together.


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Cohesion






Cohesion




The four main families of small organic

moleculesin cells.

These small molecules form the monomeric

building blocks, or subunits, for most of the

macromolecules and other assemblies of the

cell. Some, like the sugars and the fatty acids,

are also energy sources.

Organic Molecules

The reaction of two monosaccharides to form a disaccharide.

This reaction belongs to a general category of reactions termed

condensation reactions, in which two molecules join together as a result of

the loss of a water molecule. The reverse reaction (in which water is

added) is termed hydrolysis.

This common type of covalent bond between two sugar molecules is

known as a glycosidic bond

Fatty acid

-is composed of a hydrophobic hydrocarbon chain to which is attached a hydrophilic

carboxylic acid group.

-Palmitic acid is shown here. Different fatty acids have different hydrocarbon tails. (A)

Structural formula. The carboxylic acid group is shown in its ionized form. (B) Ball-and-stick

model. (C) Space-filling model.

Phospholipid structure and the orientation of phospholipids in

membranes.

In an aqueous environment, the hydrophobic tails of

phospholipids pack together to exclude water. Here they have

formed a bilayer with the hydrophilic head of each

phospholipid facing the water.

Lipid bilayers are the basis for cell membranes.


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A small part of a protein molecule.

*peptide bonds,

*N-terminus, terminates in an amino group, and the other, the C-terminus, in a

carboxyl group.

The 20 amino acids found in proteins. Both

three-letter and one-letter abbreviations are

listed. As shown, there are equal numbers of

polar and nonpolar side chains.

Three types of noncovalent bonds that help

proteins fold. Although a single one of these

bonds is quite weak, many of them often form

together to create a strong bonding

arrangement, as in the example shown. As in

the previous figure, R is used as a general

designation for an amino acid side chain.

The regular conformation of the polypeptide backbone

observed in the helix and the sheet

The NH of every peptide bond is hydrogen-bonded to the

C=O of a neighboring peptide bond located four peptide

bonds away in the same chain

A protein formed as a symmetric assembly of two d ifferent

subunits.

Hemoglobin is an abundant protein in red blood cells that

contains two copies of globin and two copies of globin.

Each of these four polypeptide chains contains a heme molecule

(red), which is the site where oxygen (O2) is bound. Thus, each

molecule of hemoglobin in the blood carries four molecules of

oxygen.

A small part of one chain of a

deoxyribonucleic acid (DNA) molecule.


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Figure 2-65. The synthesis of polysaccharides, prot eins, and nucleic

acids. Synthesis of each kind of biological polymer involves the loss of

water in a condensation reaction. Not shown is the consumption of

high-energy nucleoside triphosphates that is required to activate each

monomer prior to its addition. In contrast, the reverse reactionthe

breakdown of all three types of polymersoccurs by the simple

addition of water (hydrolysis).

Three families of macromolecules. Each is a

polymer formed from small molecules (called

monomers, or subunits) linked together by

covalent bonds.

Unifying Themes in Biology

1. THE CELL

2. HERITABLE INFORMATION

3. EMERGENT PROPERTIES

4. REGULATION

6. ENERGY AND LIFE

5. INTERACTION WITH THE ENVIRONMENT

7. UNITY AND DIVERSITY

8. EVOLUTION

9. STRUCTURE/FUNCTION

10. SCIENTIFIC INQUIRY

11. SCIENCE, TECHNOLOGY AND SOCIETY

1. THE CELL

1. THE CELL 1. THE CELL


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THE CELL THEORY

all organisms are composed of similar units of organization,

called cells

formally articulated in 1839 by Matthias Schleiden &

Theodor Schwann and has remained as the foundation of

modern biology

predates other great paradigms of biology including

Darwin's theory of evolution (1859), Mendel's laws of

inheritance (1865), and the establishment of comparative

biochemistry (1940)

The Cell Theory is to Biology as Atomic Theory is to Physics

FORMULATION OF THE CELL THEORY

In 1839, Theodor Schwann published his book on animal

and plant cells

He summarized his observations into three conclusions

about cells:

3) Cells form by free-cell formation, similar to the formation of crystals

(spontaneous generation)

1) The cell is the unit of structure, physiology, and organization in living

things.

2) The cell retains a dual existence as a distinct entity and a building block in

the construction of organisms.

The correct interpretation of cell formation by division was

finally promoted by others and formally enunciated in

Rudolph Virchow's powerful dictum, "Omnis cellula e

cellula"... "All cells only arise from pre-existing cells".

THE MODERN TENETS OF CELL THEORY

6. All energy flow (metabolism & biochemistry) of life occurs

within cells.

1. All known living things are made up of cells.

2.The cell is structural & functional unit of all living things.

3. All cells come from pre-existing cells by division.

(Spontaneous Generation does not occur).

4. Cells contains hereditary information which is passed from

cell to cell during cell division.

5. All cells are basically the same in chemical

composition.

2. HERITABLE INFORMATION

2. HERITABLE INFORMATION 3. EMERGENT PROPERTIES

Emergent property is a property which a collection or complex system has, but which the individual members do not have. For

example, the taste of saltiness is a property of salt, but that does not mean that it is also a property of sodium and chlorine,the two

elements which make up salt.


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3. EMERGENT PROPERTIES 3. EMERGENT PROPERTIES

4. REGULATION 5. INTERACTION WITH THE ENVIRONMENT

6. ENERGY AND LIFE 7. UNITY AND DIVERSITY


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7. UNITY AND DIVERSITY 7. UNITY AND DIVERSITY

Most classification schemes group organisms

into three domains:

Domain Bacteria

Domain Archaea

Domain Eukarya

Grouping Species: The Basic Idea

Taxonomy is the branch of biology that names and

classifies species into a hierarchical order

Kingdoms and domains are the broadest units of

classification

Ursidae

Ursus

Carnivora

Mammalia

Chordata

Animalia

Eukarya

Species Genus Fa mi ly O rd er Class Phylum Kingdom Domain

Ursus

americanus

(American

black bear)


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The evolutionary

view of life came

into focus in

1859 when

Charles Darwin

published The

Origin of Species

8. EVOLUTION The Origin of Species articulated twomain points:

Descent with modification (theview that contemporary speciesarose from a succession ofancestors)

Natural selection (a proposedmechanism for descent withmodification)

Some examples of descent withmodification are unity and diversity inthe orchid family

Darwin was struck by the diversity of animals on the

Galpagos Islands

Natural Selection

He thought of adaptation to the environment and the

origin of new species as closely related processes

As populations separated by a geographic barrier

adapted to local environments, they became separate

species

Natural selection can

edit a populations

heritable variations

Population with varied inheritedtraits

Elimination ofindividuals with certain traits

Reproductionofsurvivors

Increasingfrequencyoftraits that enhance

survival and reproductivesuccess

when humans choose organisms with specific characteristics as

breeding stock, they are performing the role of the environment

Artificial Selection

Example of artificial selection in animals: dog

breeding

Ger man shepher d Yorkshire terr ierEnglish springer

spanielM in i- da ch sh un d G ol de n r et ri ev er

Hundreds to

thousands of years

of breeding

(artificial selection)

Ancestral dog


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9. STRUCTURE/FUNCTION 10. SCIENTIFIC INQUIRY

11. SCIENCE, TECHNOLOGY AND SOCIETY

The goal of science is to understand natural

phenomena

Technology applies scientific knowledge for some

specific purposeScientific Method

The Nature of Science

Deductive Reasoning

Examining individual cases by applying accepted

general principles.

CopyrightMcGraw-Hill Companies Permissionrequired for reproductionor display

The Nature of Science

Inductive Reasoning

Discovering general principles through

examination of specific cases.

CopyrightMcGraw-Hill Companies Permissionrequired for reproductionor display


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Scientific Process

Observation - Careful observation of a process

or phenomenon

Hypothesis - Guess concerning the

observation

May generate multiple hypotheses.

Prediction - Expected consequences of a

correct hypothesis

Experiment - Test of a hypothesis

Scientific Process

Experiment - Test of a hypothesis

Controlled Experiment - All factors influencing the

experiment (controls) must be kept constant.

Conclusion - Draw a conclusion from the

results

Reject or fail to reject hypothesis

Theory and Certainty

Theory - set of hypotheses that have been

thoroughly tested over time, and generally

accepted by the scientific community

acceptance is always provisional

to the general public a theory is synonymous with a

guess due to lack of knowledge

Limitations of Science

Scientific study is limited to area that can be

observed and measured.

Cannot be used to address all questions.

Bound by practical limits

Temporal and spatial considerations

lecture 1-concepts of life, cell theory and scientific method

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