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Day 3 September 2nd 2014 –Water, Macromolecules, and

Chemistry

Dr. Amy B. HollingsworthNatural Science Biology

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Last time in class• We discussed

– What is science? Pseudoscience?– What is Biology?– The Scientific Method– Experiments– Empirical – Theories– Hypotheses– Controls– Variables– The Placebo Effect

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1. Pseudoscience: individuals make scientific-sounding claims that are not supported by trustworthy, methodical scientific studies.

2. Anecdotal observations: based on only one or a few observations, people conclude that there is or is not a link between two things.

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“Four out of five dentists surveyed recommend sugarless gum for their patients who chew gum.”

• “How do they know what they know?”

• Maybe the statement is factually true, but the general relationship it implies may not be.

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Anecdotal Observations do not include a

sufficiently large and representative set of observations of the world

data are more reliable than anecdotes

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1.18 A few important themes tie together the diverse topics in biology.

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Two Unifying Themes

Hierarchical organization

The power of evolution

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1.18On the road to biological literacy: what are the major themes in biology?

Four Chief Areas of Focus

1.The chemical, cellular, and energetic foundations of life

2. The genetics, evolution, and behavior of individuals

3. The staggering diversity of life and the unity underlying it

4. Ecology, the environment, and the subtle and important links between organisms and the world they inhabit

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Chapter 2: Chemistry

Raw materials and fuel for our bodiesLectures by Mark Manteuffel, St. Louis Community College

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Learning Objectives• Describe what atoms are,

their structure, and how they bond.

• Understand water’s features that help it support all life.

• Describe carbohydrates—their structure and function.

• Describe lipids—their structure and function.

• Describe proteins—their structure and function.

• Describe nucleic acids—their structure and function.

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Atoms

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2.1 Everything is made of atoms. An element is a

substance that cannot be broken down chemically into any other substances.

An atom is a bit of matter that cannot be subdivided any further without losing its essential properties.

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Atomic Numbers

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Atomic Structure:The nucleus, protons, and neutrons

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Atomic Structure: Electrons

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Isotopes

insert new fig 2.4

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Radioactive Atoms

• A few atomic nuclei are not stable and break down spontaneously.

• These atoms are radioactive.

• They release, at a constant rate, a tiny, high-speed particle carrying a lot of energy.

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Why do isotopes matter?

• Food preservation• Carbon Dating• Disease Diagnosis• Disease Treatment

• http://www.ehow.com/info_8746700_importance-isotopes.html

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25 Elements Found in Your Body and the Big 4

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Atoms can bond together to form

molecules or compounds.

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Covalent Bonds

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Ions and Ionic Bonds

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2.4 A molecule’s shape gives it unique characteristics.

• Molecular Personalities

• Shape determines function

• Physical properties such as:

»Taste»Smell

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Molecular Interactions and Insect Mating Behavior

Think about our termite lab!

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2.4 Hydrogen bonds make water cohesive.

Insert fig 2-13

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2.5 Water has unusual properties that make it critical to life.

• Cohesion

• Large heat capacity

• Low density as a solid

• Good solvent

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Cohesion

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Heat Capacity

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Low Density as a Solid

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Living systems are highly sensitive to acidic and basic conditions.

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Hydrogen Ions and Hydroxide Ions

Ionized Hydroxide Molecule

OH -

Non-Ionized Water Molecule

H2OO O

H H H

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pH Scale

The amount of H+ in a solution is a measure of its acidity and is called pH.

Acids

Bases

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H+ Ions and Acids• H+ very reactive

• Acids can donate H+ to other chemicals

• Stomach acids

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Bases

• Low H+• High OH

• Antacids• Baking soda, seltzer, milk of

magnesia

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Blood pH

Buffers• can quickly absorb

excess H+ ions to keep a solution from becoming too acidic

• can quickly release H+ ions to counteract any increases in OH concentration

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Carbohydrates are fuel for living machines.

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2.7 Carbohydrates include macromolecules that function as fuel.Health topics of

the year

• Low-carb diet?

• Hi-carb diet?

• “Carbo-loading”?

• Fiber intake?

What are carbohydrates?

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Carbohydrates

• C, H, and O

• Primary fuel for organisms

• Cell structure

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Energy is in the chemical bonds!

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Take-home message 2-7

Carbohydrates are the primary fuel for running all cellular machinery and also form much of the structure of cells in all life forms. Carbohydrates contain carbon, hydrogen, and oxygen, and generally have the same number of carbon atoms as they do H2O units.

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Take home message 2.7

• The C-H bonds of carbohydrates store a great deal of energy and are easily broken by organisms.

• The simplest carbohydrates, including glucose, are monosaccharides or simple sugars.

• They contain from three to six carbon atoms.

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2.8 Glucose provides energy for the body’s cells.

• Fuel for cellular activity

• Stored temporarily as glycogen

• Converted to fat

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Glucose

Most carbohydrates— ultimately converted into glucose

Blood sugar

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What is “carbo-loading”?

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Take home message 2.8

• Glucose is the most important carbohydrate to living organisms.

• Glucose in the bloodstream can be used as an energy source, can be stored as glycogen in the muscles and liver for later use, or can be converted to fat.

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2.9 Many complex carbohydrates are time-released packets of energy.

• More than 1 sugar (monosaccharide) unit

• Disaccharides– sucrose– lactose

• Polysaccharides– starch– cellulose

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Chemical Fuel

Preliminary Processing

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2.10 Not all carbohydrates are digestible.

Chitin

Cellulose

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Insert new fig 2-26

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Fiber

• “Roughage”

• Colon cancer prevention/reduction

• Termites ecological role

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Lipids store energy for a rainy day.

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Why does a salad dressing made with vinegar and oil separate into two layers shortly after you shake it?

Hydrophobic

Hydrophilic

2.11 Lipids are macromolecules with several functions, including energy storage.

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Take-home message 2.11

Lipids are non-soluble in water and greasy to the touch.

They are valuable to organisms in long-term energy storage and insulation, membrane formation, and as hormones.

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2.12 Fats are tasty molecules too plentiful in our diets.

Glycerol: “head” region

Fatty acid “tails”

Triglycerides

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Fat molecules contain much more stored energy than carbohydrate molecules.

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Saturated and Unsaturated Fats # of bonds in the hydrocarbon chain in a fatty

acid Health considerations

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Take-home message 2.13 Characterized by long hydrocarbon

tails, fats effectively store energy in the many carbon-hydrogen and carbon-carbon bonds.

Their caloric density is responsible for humans’ preferring fats to other macromolecules in the diet, and is also responsible for their association with obesity and illness in the modern world.

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2.13 Cholesterol and phospholipids are used to build sex hormones and membranes.

Not all lipids are fats

The sterols

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Cholesterol

• Important component of most cell membranes.

• Can attach to blood vessel walls and cause them to thicken.

• Cells in our liver produce almost 90% of the circulating cholesterol.

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Steroid Hormones

Estrogen

Testosteronesynthetic variants of testosterone

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Phospholipids and Waxes

• Phospholipids are the major component of the cell membrane.

• Waxes are strongly hydrophobic.

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