DMA

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DMA

• Body fat appears yellow in certain rabbits, but
  only when those rabbits eat plants that contain a
  yellow pigment molecule called xanthophyll.
  Design an experiment (hypothesis, IV, DV, CVs) to
  explore whether it is truly the effect of
  xanthophyll that makes the body fat yellow.

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DMA Solution

• If rabbits are fed leafy plants with xanthophyll
  then their body fat will be yellow.

IV xanthophyll plants DV fat color CVs gender,
age, nutrition, etc.
Use large groupswhy? Replicate!
3
Chemical Foundation for Cells

• Starr/Taggarts
• Biology
• The Unity and Diversity of Life, 9e
• Chapter 2

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Chapter 2 Focus on Chemistry Basics

• Atomic structure and bonding
• Ionic
• Covalent
• Hydrogen
• Properties of Water (end of unit)
• pH and buffers (end of unit)

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Key Concepts

• Atoms are the basic building blocks of matter
• Atoms have no overall electric charge unless they
  lose or gain electrons to become ions
• Whether an atom will interact with other atoms
  depends on the number and arrangement of its
  electrons

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Structure of Atoms

• Subatomic particles
• Protons - positive charge
• Electrons - negative charge
• Neutrons - no charge
• Atomic Number
• Number of protons
• Mass Number
• Number of protons number of neutrons

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Electrons and Energy Levels

• Shell model
• Shells Energy levels
• Shell closest to nucleus
  has the lowest
  energy
  level

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Shell Model of Distribution of Electrons in Atoms
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From Atoms to Molecules

• Molecule
• Two or more atoms bonded together
• Molecules form as a result of bonding

http//www.fhcrc.org/education/hutchlab/lessons/3d
/
http//www.dcu.ie/chemist/pratt/JGallery/JGallery
.htm
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Ions and Ionic Bonding

• Ion Any atom that has either gained or lost an
  electron
• Charged particle ( or -)
• Predict the ion for Na, Cl, and Ca

Fig. 2.8, p. 25
Fig. 2.8, p. 25
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Ions and Ionic Bonding

• Solution

Na
Cl-
Ca2
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Ions and Ionic Bonding

• Ionic bond - Association of two ions that have
  opposing charges after electrons are transferred
  (Ex. Sodium chloride, NaCl)
• Na and Cl-

-
Fig. 2.10a, p. 26
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Covalent Bonding

• Covalent bonds
• Sharing of a pair of electrons
• Single, Double, and Triple Bonds
• Example H2
• What would water look like?

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Covalent Bonding

• Water

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Covalent Bonding

• Water
• Non-polar or polar?
• Polar - atoms dont exert same pull on shared
  electrons

O is more electronegative
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Important Bonds in Biological Molecules

• Hydrogen bonds
• Electronegative atom of a molecule weakly
  interacts with a hydrogen atom

Hydrogen bonds may form between two or more
molecules
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DMA (100 to complete)

• What is the difference between ionic and covalent
  bonding?

http//www.healthchecksystems.com/images/omolecule
.gif
http//www.chm.bris.ac.uk/chjnh/gcse/pics/water_c
luster.jpeg
http//www.cem.msu.edu/reusch/VirtualText/Images/
nacl.gif
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Covalent Bonding

• Covalent bonds
• Sharing of a pair of electrons
• Single, Double, and Triple Bonds
• Example H2

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Hydrogen Bond Wrap-Up

• Hydrogen bonds
• Electronegative atom of a molecule weakly
  interacts with a hydrogen atom

Hydrogen bonds may form between two or more
molecules or within molecules
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Examples of H Bonds

• Water
• DNA

http//bioweb.wku.edu/courses/Biol220/chembond/Ima
ges/WaterHBonds.GIF
http//molvis.sdsc.edu/dna/pairs2.gif
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From Bonding to Biomolecules

• Next, we will consider the four main classes of
  biomolecules
• Carbohydrates
• Proteins
• Lipids
• Nucleic Acids

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Properties of Water

• Learn them and explore them!

O is more electronegative
WATER A POLAR MOLECULE
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Implications of Waters Polarity

• Water is attracted to other polar molecules
• Hydrophilic
• Water repels
  hydrophobic
  substances
• Hydrophobic

http//old.jccc.net/pdecell/chemistry/water3.gif
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Implications of Waters Polarity

• Water has several unique properties
• cohesiveness and adhesiveness
• a capacity to dissolve or repel substances
  (spheres of hydration)
• temperature-stabilizing effects
• These properties rely on H bonding

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Cohesion
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Cohesive/Adhesive

• Cohesion water sticks to itself
• Adhesion water sticks to other surfaces

Leaf
Root
http//www.tvdsb.on.ca/westmin/science/sbioac/plan
ts/cohesion.gif
27
Spheres of Hydration Around Two Charged Ions

• Salt (NaCl) dissolves in water and separates into
  Na and Cl-

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Temperature Stabilization

• Temperature is a measure of molecular motion
• H bonds must be broken before water can evaporate

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Water Lab
http//www.ascendingenterprises.com/images/water.g
if
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DMA

• Waters polarity results in three special
  properties. What are they and briefly explain
  them.

http//www.chm.bris.ac.uk/chjnh/gcse/pics/water_c
luster.jpeg
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Quick review

• What are the three types of bonding?
• What makes the bond types different from one
  another?
• Give examples of molecules with each style
  of bonding.

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Water Lab Debrief
http//www.scican.com/polysil/images/page1/polysil
_1_photo_1.jpg
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Water Lab Debrief
http//www.ianr.unl.edu/pubs/fieldcrops/graphics/s
oilh2o5.gif
http//www.tvdsb.on.ca/westmin/science/sbioac/plan
ts/cohesion.gif
34
Water Lab
Leaves
Red Dye
http//www.lakelandschools.org/EDTECH/GrowWithUs/r
ooney/rooney.htm
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Water Lab Debrief
http//www.biologylessons.sdsu.edu/classes/lab1/ja
r.gif
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The pH Scale

• Water molecules break apart to form H and OH-
  ions

H
OH-
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The pH Scale

• Water molecules break apart to form H and OH-
  ions

H2O
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The pH Scale

• Water molecules break apart to form H and OH-
  ions

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The pH Scale

• Water molecules break apart to form H and OH-
  ions

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The pH Scale

• Water molecules break apart to form H and OH-
  ions

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The pH Scale

• Water molecules break apart to form H and OH-
  ions

H
OH-
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pH Continued

• Scale 0 - 14
• Neutral 7
• Acid 0 to less than 7
• Base greater than 7 to 14
• Acid substance that donates H
• Base substance that accepts H

http//www.swbic.org/education/env-engr/chem/img00
001.gif
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Buffers Against Shifts in pH

• Buffer system partnership between a weak acid
  and the base that forms when dissolved in water,
  the two work to counter slight shifts in pH
• Example Blood pH (7.3 7.5)
• You breathe in oxygen and then through cell
  respiration make carbon dioxide.
• You have water in your blood plasma.
• Bicarbonate-carbonic acid buffer system
• H2CO3 ------gt HCO3- H
• HCO3- H ------gt H2CO3

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Another Buffer System

• Another example of one of the many buffer systems
  we have in place is the acetic acid system
• OH- CH3COOH ? CH3COO- H2O
• This system helps to maintain blood pH for
  metabolic reactions