Chapter 2: Chemistry Raw materials and fuel for our bodies Lectures by Mark Manteuffel, St. Louis...

Chapter 2: Chemistry

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

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.

Learning Objectives

Describe lipids—their structure and function.

Describe proteins—their structure and function.

Describe nucleic acids—their structure and function.

2.1–2.3

Atoms form molecules

through bonding.

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.

Atomic Structure:The nucleus, protons, and

neutrons

Atomic Structure: Electrons

Atomic Numbers

Insert new figure 2.3

Take-home message 2.1

Everything around us, living or not, is made from atoms, the smallest unit into which material can be divided.

Atoms all have the same general structure.

They are made up of protons and neutrons in the nucleus and electrons, which circle far around the nucleus.

2.2 An atom’s electrons determine how (and whether) the atom will bond with other atoms.

Electron shells

Electron Shells

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The Versatility of Carbon

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Isotopes

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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.

Take-home message 2.2

The chemical characteristics of an atom depend upon number of electrons in their outermost shells.

Atoms are most stable and least likely to bond with other atoms when their outermost electron shell is full.

2.3 Atoms can bond together to form molecules or compounds.

Products of bonding!

Molecules

Covalent Bonds

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Ions

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Ions and Ionic Bonds

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Hydrogen Bonds

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Insert fig 2-12

Take-home message 2.3

Atoms can be bound together in three different ways.

Covalent bonds, in which atoms share electrons, are the strongest.

Take-home message 2.3

In ionic bonds, one atom transfers its electrons to another and the two oppositely charged ions are attracted to each other, forming a compound.

Take-home message 2.3

Hydrogen bonds, which are weaker than covalent and ionic bonds, involve the attraction between a hydrogen atom and a polar molecule.

2.4–2.6

Water has features

that enable it to

support all life.

2.4 Hydrogen bonds make water cohesive.

Insert fig 2-13

Take-home message 2.4

Water molecules easily form hydrogen bonds, giving water great cohesiveness.

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

Cohesion

Large heat capacity

Low density as a solid

Good solvent

Cohesion

Take home message 2.5

The hydrogen bonds between water molecules give water several of its most important characteristics:• cohesiveness• reduced density as a solid• the ability to resist temperature changes• broad effectiveness as a solvent for ionic and

polar substances

2.6 Living systems are highly sensitive to acidic and basic conditions.

Hydrogen Ions and Hydroxide Ions

Ionized Hydroxide Molecule

OH -

Non-Ionized Water Molecule

H2OO O

H H H

pH Scale

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

Acids

Bases

H+ Ions and Acids

H+ very reactive

Acids can donate H+ to other chemicals

Stomach acids

Bases

Low H+High OH

AntacidsBaking soda, seltzer, milk of

magnesia

Take-home message 2.6

The pH of a fluid is a measure of how acidic or basic a solution is and depends on the concentration of dissolved H+ ions present.

The lower the pH, the more acidic the solution

Acids, such as vinegar, can donate protons to other chemicals while bases, including baking soda, bind with free protons.

2·7–2·10 Carbohydrates

are fuel for living

machines.

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?

Four Types of Macromolecules

Carbohydrates

Lipids

Proteins

Nucleic acids

Carbohydrates

C, H, and O

Primary fuel for organisms

Cell structure

Energy is in the chemical bonds!

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.

Take-home message 2.7

Carbohydrates contain carbon, hydrogen, and oxygen, and generally have the same number of carbon atoms as they do H2O units.

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.

Take home message 2.7

As the chemical bonds of carbohydrates are broken down and other more stable bonds are formed, a great deal of energy is released that can be used by organisms.

2.8 Glucose provides energy for the body’s cells.

Fuel for cellular activity

Stored temporarily as glycogen

Converted to fat

Glucose

Most carbohydrates— ultimately converted into glucose

Blood sugar

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.

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

More than 1 sugar (monosaccharide) unit

Disaccharides• sucrose• lactose

Polysaccharides• starch• cellulose

Chemical Fuel

Preliminary Processing

Starch

> 100’s of glucose molecules joined together

Barley, wheat, rye, corn, and rice

Glycogen—“animal starch”

Complex Carbohydrates

“Time-release” fuel pellets

Take-home message 2.9

Multiple simple carbohydrates sometimes link together into more complex carbohydrates.

Types of complex carbohydrates include starch, the primary form of energy storage in plants, and glycogen, a primary form of energy storage in animals.

2.10 Not all carbohydrates are digestible.

Chitin

Cellulose

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Fiber

“Roughage”

Colon cancer prevention/reduction

Termites ecological role

Take-home message 2.10

Some complex carbohydrates, including chitin and cellulose, cannot be digested by most animals.

Such indigestible carbohydrates in the diet, called fiber, aid in digestion and have numerous health benefits.

2.11–2.13

Lipids store energy

for a rainy day.

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.

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.

2.12 Fats are tasty molecules too plentiful in our diets.

Glycerol: “head” region

Fatty acid “tails”

Triglycerides

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

Fat molecules contain much more stored energy than carbohydrate molecules.

Take-home message 2.12

Fats, including the triglycerides common in the food we eat, are one type of lipid.

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.

2.13 Cholesterol and phospholipids are used to build sex hormones and membranes. Not all lipids are fats

The sterols

Phospholipids and Waxes

Phospholipids are the major component of the cell membrane.

Waxes are strongly hydrophobic.

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

Take-home message 2.13

Cholesterol and phospholipids are lipids that are not fats.

Both are important components in cell membranes.

Cholesterol also serves as a precursor to steroid hormones, important regulators of growth and development.

2.14–2.18

Proteins are versatile

macromolecules that

serve as building

blocks.

2.14 Proteins are bodybuilding macromolecules.

Amino Acids

Twenty different amino acids

Strung together to make proteins

Take-home message 2.14

Unique combinations of 20 amino acids give rise to proteins, the chief building blocks of physical structures that make up all organisms.

Proteins perform myriad functions, from assisting chemical reactions to causing blood clotting to building bones to fighting microorganisms.

2.15 Proteins are an essential dietary component. Growth

Repair

Replacement

Food labels indicate an item’s protein content.

Why is this insufficient for you to determine whether you are protein deficient, even if your protein intake exceeds your recommended daily amount?

Complete Proteins

Have all essential amino acids

Incomplete proteins

Complementary proteins

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Which answer below will provide all of the essential amino acids in a meal?

1. Hamburger2. Corn and a legume (complementary)3. Apple4. Both 1 and 2 are correct.

Take-home message 2.15

Twenty amino acids make up all the proteins necessary for growth, repair, and replacement of tissue in living organisms.

Take-home message 2.15

Of these amino acids, about half are essential for humans: they cannot be synthesized by the body so must be consumed in the diet.

Complete proteins contain all essential amino acids, while incomplete proteins do not.

2.16 A protein’s function is influenced by its three-dimensional shape.

Peptide bonds

Primary Structure

The sequence of amino acids

Secondary Structure

Hydrogen bonding between amino acids

The two most common patterns:

• twist in a corkscrew-like shape

• zig-zag folding

Tertiary Structure Folding and

bending of the secondary structure

Due to bonds such as hydrogen bonds or covalent sulfur-sulfur bonds.

Quaternary Structure

When two or more polypeptide chains are held together by bonds between the amino acids on the different chains.

Hemoglobin

Egg whites contain much protein.

Why does beating them change their texture, making them stiff?

Egg whites contain much protein.

Why does beating them change their texture, making them stiff?

Why is wet hair easier to style than dry hair?

Why do some people have curly hair and others have straight hair?

Getting hair straightened at a hair salon involves…

Changing the t..

.

Reforming h

ydr...

Changing the p...

1 and 2.

25% 25%25%25%1. Changing the tertiary structure of the hair proteins.

2. Reforming hydrogen bonds that have been broken.

3. Changing the primary structure of the hair proteins.

4. 1 and 2.

Take-home message 2.16 The particular amino acid sequence of a

protein determines how it folds into a particular shape.

This shape determines many of the protein's features, such as which molecules it will interact with.

When a protein's shape is deformed, the protein usually loses its ability to function.

2.17 Enzymes are proteins that initiate and speed up chemical reactions.

Activation Energy

Chemical reactions occurring in organisms can either release energy or consume energy.

In either case, the reaction needs a little “push” in order to initiate the reaction―called activation energy.

Enzymes act as catalyst by lowering the activation energy.

An enzyme can reduce the activation energy in a variety of ways.

1. By stressing, bending, or stretching critical chemical bonds

2. By directly participating in the reaction3. By creating a microhabitat that is

conducive to the reaction4. By simply orienting or holding

substrate molecules in place so that they can be modified.

Classroom Catalyst

Why can’t we digest cellulose?

The polysaccharides amylose and cellulose are both made of glucose. Why can’t the enzyme salivary amylase breakdown both?

1. The orientation of the covalent bonds are different.

2. The active site of the enzyme cannot bind to glucose.

3. The enzyme cannot digest cellulose at normal body temperatures (32oC).

4. The covalent bonds in cellulose are stronger than in amylose.

Take-home message 2.17

Enzymes are proteins that help initiate and speed up chemical reactions.

They aren’t permanently altered in the process but rather can be used again and again.

2-18 Enzymes regulate reactions in several ways (but malformed enzymes can cause problems).

The rate at which an enzyme catalyzes a reaction is influenced by several chemical and physical factors.

Insert new figure 2-43, preferably broken into 4 stepped segments

Insert fig 2-43, pt 2

Insert fig 2-43, pt 3

Insert fig 2-43, pt 4

“Misspelled” Proteins

Incorrect amino acid sequence

Active site disruptions

PhenylketonuriaInsert fig 2-44 to right

Why do some adults get sick when they drink milk?

Lactase cannot function properly in this example because the….

1. shape is incorrect.

2. amino acid sequence is incorrect.

3. color is incorrect.

4. 1 and 2

When lactase is functioning correctly it…

lowers

the act.

..

incre

ases t

he ...

acts as a

n inh...

acts as a

n act...

25% 25%25%25%1. lowers the activation energy

required to digest lactose.2. increases the activation energy

required to digest lactose.3. acts as an inhibitor to decrease

the activity of enzymes that breakdown lactose.

4. acts as an activator to increase the activity of enzymes that breakdown lactose.

Take-home message 2.18

Enzyme activity is influenced by physical factors such as temperature and pH, as well as chemical factors, including enzyme and substrate concentrations.

Take-home message 2.18

Inhibitors and activators are chemicals that bind to enzymes, and by blocking the active site or altering the shape or structure of the enzyme can change the rate at which the enzyme catalyzes reactions.

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.