Biology 203

Question 1

Evolution

Answer 1

Progressive change in inherited characteristics
from generation to generation
– Mechanism involved

Question 2

Natural selection

Answer 2

Natural variation among individuals of any population of
organisms
– Some differences may improve the chances of survival

Question 3

Origin of Species

Answer 3

Species arose from a succession of ancestors

Question 4

Cornerstone of modern biology

Answer 4

Bacterial antibiotic and antiviral resistance
– Modern agriculture
– Commercial hunting and fishing
– Cancer research

Question 5

Matter

Answer 5

Organisms are composed of matter

Matter is anything that takes up space and has
mass

• Matter consists of chemical elements in pure form
and in combinations called compounds

Question 6

Elements

Answer 6

Matter is made up of elements

An element is a substance that cannot be broken down to other substances by chemical reactions

Question 7

Compounds

Answer 7

A compound is a substance consisting of two or more elements in a fixed ratio

A compound has characteristics different from those of its elements.

Question 8

Atoms

Answer 8

Each element consists of
unique atoms

An atom is the smallest unit
of matter that still retains
the properties of an
element

Question 9

Subatomic Particles

Answer 9

Atoms are composed of subatomic
particles

Relevant subatomic particles include:
– Neutrons (no electrical charge)
– Protons (positive charge)
– Electrons (negative charge)

Neutrons and protons form the atomic nucleus
• Electrons form a cloud around the
nucleus
• Neutron mass and proton mass are
almost identical and are measured in
daltons

Question 10

Atomic structure : Isotopes and atoms

Answer 10

Atoms of different elements differ in their
number of subatomic particles:

Isotopes of an element have same number of
protons but different number of neutrons:

Question 11

Radioactive Isotopes

Answer 11

Some applications in biological
research
– Dating fossils
– Tracing atoms through metabolic
processes
– Diagnosing medical disorders 

Dangers
– Radionuclides released into the
environment
• Radioactive contamination
• Radiation poisoning

Question 12

Radiocarbon Dating

Answer 12

Dating method utilizing the
naturally occurring radioisotope
– Carbon-14 (14C)
– Developed by Willard Libby (1949)

Plants fix atmospheric carbon
dioxide (C02) into organic material
– Photosynthesis
– Consumption by animals

Question 13

Radiocarbon Dating 2

Answer 13

14C declines at a fixed exponential
rate
– Radioactive decay
– Half-life = 5,730 years

• Compare remaining 14C to that
expected for atmospheric 14C
(constant due to cosmic rays)
– Age of sample is determined

Question 14

PET Scan: Medical Use For

Radioactive Isotopes

Answer 14

Positron-emission tomography
– Detects location of intense chemical
activity in the body

• Glucose labeled with radioactive
isotope (Fluorine-18)
– Emission of subatomic particles
– Collision with electrons made available
by chemical reactions in the body

• PET scanner detects the energy
released in these collisions
– Maps “hot spots”
– Gives both anatomic and metabolic
information

Question 15

PET Scan

Answer 15

Bright yellow color
– Cancerous throat tissue

• Other Applications
– Brain imaging
– Cardiovascular disease/stroke
– Musculo-skeletal imaging

Question 16

Electrons are Distributed

in Shells of Orbitals

Answer 16

The first shell
– Has only an s orbital that is spherical in shape

• The second shell
– Has another s orbital and 3 p orbitals that are shaped somewhat like dumbbells

Question 17

Electrons are Distributed

in Shells of Orbitals (2)

Answer 17

Each orbital contains a maximum of two electrons
• Chemical behavior of an atom
– depends mostly on number of electrons in outermost shell called valence electrons

Question 18

Energy Levels of Electrons /

Electron Shells

Answer 18

Electrons in an atom vary in the amount of potential
energy they possess (fixed, discrete amounts)

Different discrete energy levels correlate with
average distance of electron from nucleus
(electron shells)

Question 19

Excitation of Chlorophyll by Light

Answer 19

When a pigment absorbs
light
– it goes from a ground state
to an excited state
• Which is unstable

• When excited electrons fall
back to the ground state
– Photons are given off
• An afterglow called
fluorescence

• If illuminated, an isolated
solution of chlorophyll will
fluoresce
– Giving off light and heat

Question 20

Chemical Bonds: Linking Atoms Together

Covalent Bonds

Answer 20

Sharing of a pair of valence electrons by two atoms
• Shared electrons count as part of each atom’s valence shell
• Form when two atomic nuclei
share one or more pairs of electrons filling their orbitals
• The orbitals have orientations
in space that give molecules three-dimensional shapes

Question 21

Chemical Bonds: Linking Atoms Together

Covalent Bonds 2

Answer 21

A molecule
– Consists of two or more atoms held
together by covalent bonds

• A single covalent bond, or single bond
– sharing of one pair of valence electrons

• A double covalent bond, or double
bond,
– Sharing of two pairs of valence electrons

Question 22

Ionic Bonds

Answer 22

Atoms
– Sometimes strip electrons from their bonding partners
• Example
– The transfer of an electron from sodium to chlorine

• After the transfer of an electron, both atoms have charges
• A charged atom (or molecule)
– Called an ion

Question 23

Whats an Ionic Bond?

Answer 23

A cation
– A positively charged ion

• An anion
– A negatively charged ion

• An ionic bond
– An attraction between
an anion and a cation

Compounds formed by ionic bonds
– Called ionic compounds, or salts

• Salts
– Sodium chloride (table salt)
– Often found in nature as crystals

Question 24

Electronegativity

Answer 24

An atom’s attraction for the electrons in a covalent bond.

The more electronegative an atom, the more strongly it pulls shared electrons toward itself

• In a nonpolar covalent bond
– the atoms share the electron
equally
• In a polar covalent bond
– one atom is more electronegative
– The atoms do not share the
electron equally
• Unequal sharing of electrons
– Causes a partial positive or negative charge for each atom or molecule

Question 25

Hydrogen Bonds

Answer 25

A hydrogen bond

Forms when a
hydrogen atom covalently bonded to one electronegative atom is also
attracted to another
electronegative atom

• In living cells
– The electronegative partners are usually oxygen or nitrogen atoms

Question 26

Van der Waals Interactions

Answer 26

Van der Waals interactions
–
Attractions between molecules that are
close together as a result of these charges

• If electrons are distributed
asymmetrically in molecules or atoms
– They can result in “hot spots” of positive or negative charge

• Collectively, such interactions can be strong
– As between molecules of a gecko’s toe hairs and a wall surface

Question 27

Carbohydrates

Answer 27

Carbohydrates Serve as Fuel
and Building Material

Carbohydrates
– Sugars
– Polymers of sugars

• Simplest carbohydrates
– Monosaccharides or single
sugars
•
 Carbohydrate macromolecules
– Polysaccharides
• Polymers composed of many sugar building blocks

Question 28

Monosaccharides

Answer 28

• Monosaccharides
– Molecular formulas usually multiples of CH2O

• Glucose (C6H12O6)
– Most common monosaccharide
• Grape sugar
• Corn sugar
• Blood sugar
– One of the main products of photosynthesis
– Source of energy
• Glycolysis

Monosaccharides are classified by
– The location of the carbonyl group (as aldose or ketose)
– The number of carbons in the carbon
skeleton

Question 29

Carbohydrates in CH2O

Answer 29

Contain Carbon, Hydrogen and Oxygen in the

ratio CH2O

Question 30

Monomers

Answer 30

The simplest Carbohydrates are the Simple Sugars,
these are classified by:

Type of Carbonyl group  Ketone  Ketose

Aldehyde  Aldose

or by
Number of Carbon atoms:
3 C’s  Triose
4 C’s  Tetrose
5 C’s  Pentose
6 C’s  Hexose
Note: suffix …ose indicates a sugar

Question 31

Linear and Ring Forms

Answer 31

Though often drawn as linear skeletons, in aqueous solutions many sugars form rings
– Chemical equilibrium between the linear and ring structures greatly favors the formation of rings

• Monosaccharides serve as a major fuel for cells and as raw material for building molecules

Question 32

Examples of Disaccharide Synthesis

Answer 32

Disaccharide formation
– Dehydration reaction joins two monosaccharides
• This covalent bond is called a
glycosidic linkage

• Maltose
– Malt sugar

• Sucrose
– Table sugar

• Lactose
– Galactose and Glucose
– Milk sugar

Question 33

Polysaccharides

Answer 33

Polysaccharides
– The polymers of sugars
– Storage and structural roles

• Structure and function of
a polysaccharide
– Determined by its sugar monomers and the
positions of glycosidic linkages

Question 34

Storage Polysaccharides

Answer 34

Starch
– Storage polysaccharide of plants
– Consists entirely of glucose monomers

• Plants
– Store surplus starch as granules
• Within chloroplasts and other plastids

– Unbranched
• Amylose

– Branching
• Amylopectin
–(16) Slide 8

Question 35

Glycogen: An Animal Polysaccharide

Answer 35

Glycogen
–Storage polysaccharide in animals
– More branched then amylopectin
• 
Humans and other vertebrates
– Store glycogen mainly in liver and muscle cells
• Granules in the cytoplasm

• Glycogen debt
– “Hitting the wall”
– Marathon runners
• Extreme fatigue

Question 36

Structural Polysaccharides

Answer 36

The polysaccharide cellulose
– Major component of the tough wall of plant cells
– Most abundant organic compound on Earth
– Alternative fuel source
• Cellulose is a polymer of glucose
– Like starch
– Glycosidic linkages differ
• The difference is based on two ring forms for glucose: alpha () and beta ()

Question 37

The Arrangement of Cellulose in Plant Cell Walls

Answer 37

Polymers with (alpha) glucose are helical

• Polymers with (beta) glucose are straight

• In straight structures
• H atoms on one strand can
bond with OH groups on other strands

• Parallel cellulose molecules held
together this way are grouped into microfibrils
• Form strong building materials for plants
• Major constituent of paper
• Only component of cotton