chapter 2 power point le

8/3/2019 Chapter 2 Power Point Le

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Vanders

Human Physiology

The Mechanisms of Body FunctionTenth Editionby

Widmaier Raff Strang The McGraw-Hill Companies, Inc.

Figures and tables from the book, with additional comments by:

John J. Lepri, Ph. D.,

The University of North Carolina at Greensboro

Chapter 2


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Molecules you need to know Carbohydrates

Lipids Proteins

Nucleic acids


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Introduction forChapter 2

Chemical composition of the body

The three-dimensional shape of a molecule determines

its function.

Atoms interact and bond by various means and with

varying strength of association.

Ions are the result of a mismatch between the numbers

of protons and electrons.

Carbohydrates, proteins, lipids, and nucleic acids have

essential roles in cell physiology.


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Atoms are made up of subatomic particles:

an atomic nucleus with neutrons and protons

and a surrounding cloud of electrons.

Humans are large collections of

tissues and organ systems.

Organ systems are large collections of

extracellular matrixes and cells.

Cells are large collections of

organelles and molecules.

Molecules are small to large collections of

elements whose atoms are held together

by chemical bonds.


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In a methane molecule, each of 4 hydrogen atoms is

covalently bonded (sharing electrons with) to a carbon atom.

Figure 2-1


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There are several ways to express the structure of molecules.

Structure helps us understand function.

Two dimensions:

Three dimensions:

Space-filling models:

Figure 2-2


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Table 2-3:

Most frequently encounteredionic forms of elements.

An ion results when a molecule

gains or loses one or more electrons.Ions are mismatched in the number

of protons and electrons, and are

therefore electrically charged.

What is an ion?

The origin of an ions proton-electron mismatch is indicatedby the sign (plus or minus) and number of signs:

Cl- represents a chlorine atom that has gained an electron.

Ca++ represents a calcium atom that has lost two

electrons.


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Rotations of

bonds can

result in major

rearrangementsof a molecules

three-dimensional

shape, and,

therefore, its

molecular function.

becoming a ring

linear chain

Figure 2-3


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Table 2-4:

Examples of non-polar and polar

bonds, and ionized chemical groups.

Like dissolves like applies here:

polar compounds, including water molecules, readilyassociate with each other, whereas

non-polar compounds readily associate with each

other, including such compounds in cell membranes.

Hydrophilic, or water-loving, compounds, e.g., NaCl,dissolve readily in water.

Hydrophobic, or water-fearing, compounds, e.g., fats, do

not dissolve readily in water, but will dissolve readily

into non-polar solvents, even cell membranes.


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In each water molecule,

the shared electronsspend more time

close to the larger oxygen

atom, making that area

slightly electronegative

compared to the areanear the hydrogen atoms.

The dotted lines betweenwater molecules represent the

hydrogen bonds, resulting

from the weak electrical

attractions.

Figure 2-4


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Solvent + Solute(s) = A Chemical Solution

To describe the number of dissolved solutes ina solution, we refer to the chemical concentration

of the solute, which is the amount of solute present

in a given volume of solvent.

The molecular weight (MW) of a solute reveals

the number of grams of that solute you would

need to add to one liter (L) of solvent to produce

a 1-molar solution, e.g.:

C6H12O6 (glucose) has a MW of 180, so

to make a 1M glucose solution,

add 180 g of glucose to 1 L of water.


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Positive sodium ions (Na+)

are attracted to negative

chloride ions (Cl-) to form

ionic bonds.

Water, because of its regions of

polarity, is a solvent that readily

dissolves Na+Cl- .

Figure 2-5


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In a collection of

amphipathic molecules,e.g., phospholipids,

similar regions

will spontaneously

arrange themselves

with other similar regions.

Here, the non-polar regions

associate with each other

and the polar regions form

hydrogen bonds with the

surrounding (polar) water

molecules.

Figure 2-6


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Covalent bonds (share electrons)

e.g., methane, CH4 (Figure 2-1)

Ionic bonds (opposite charges attract)

e.g., sodium chloride, Na+Cl- (Figure 2-5)

Hydrogen bonds (attraction of H to O or N)

e.g., between H2O molecules (Figure 2-4)

van der Waals forces (like dissolves like)

e.g., between lipid molecules (Figure 2-6)

STRONG

WEAK

Strength and type of chemical bonds and interactions:


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The pH value indicates the acidity of a solution.

The concentration of free hydrogen ions in a solution isthe primary determinant of that solutions acidity:

pH= -log[H+]remember that the representation [x]

is a quick way to state the chemicalconcentration of solute x

When the number in [H+] is high, the value of pH is low,

owing to the way the math works.

Thus,

an acidic solution has a pH < 7.

pH 7 is considered neutral,

and pH > 7 is considered alkaline (basic).


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Both representations of glucose show the many covalent

bonds that make this monosaccharide an energy-rich

molecule.

Figure 2-7


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A difference in the position of the indicated OH group is

the structural difference between the monosaccharides

glucose and galactose.

Figure 2-8


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The disaccharide sucrose and a water molecule result from

the linkage of the monosaccharides glucose and fructose

(energy input is required and intermediate stages are not

shown here).

Figure 2-9


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Glycogen is a polysaccharide that serves as a high-energy

storage polymer made up of glucose units. When needed,

these glucose units are released into the blood for energy-

transfer reactions.

Figure 2-10


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Glycerol and fatty acids are subunits for the formation of:

triglycerides (among the bodys fats), and phospholipids

(membrane components).Figure 2-11


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Cholesterol molecules promote membrane fluidity and serve

as starting materials for the synthesis of steroid hormones.

Figure 2-12


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Side chains can be:

non-polar groups

or

polar groups

or

ionized groups

All amino acids have:

an amino group,

a carboxyl group, and a

varying side chain [R]

Figure 2-13


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Peptide bonds are covalent bonds that connect

neighboring amino-acids together to form a polypeptide.

[Intermediate stages are not shown].

Figure 2-14


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This necklace cartoonindicates the linear

sequence of neighboring

amino-acid components

in a protein and also shows

that the side-chains caninteract (see also Figure 2-17).

Each colored bead

represents one of the

component amino acids.

Figure 2-15


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A space-filling cartoon

of the protein myoglobins

3-D shape or conformation.

Each dot represents the

location of a single aminoacid.

Figure 2-16


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Chemical interactions between non-adjacent amino acids

in a protein range from strong (covalent bonds, 4) to

weak (van der Waals, 3), but all of these interactions play

essential roles in determining protein conformation.

Figure 2-17


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Many proteins include regions where helical structure is

apparent: these result from hydrogen bonding between

regularly spaced peptide bonds.

Figure 2-18


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Many proteins also include regions where structures called

beta sheets are apparent: these result from H-bonding

between certain non-adjacent amino acids.

Figure 2-19


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Table 2-6:

Bonding forces between atoms

and molecules.

Covalent bonds (share electrons)

e.g., methane, CH4 (Figure 2-1)

Ionic bonds (opposite charges attract)

e.g., sodium chloride, Na+Cl- (Figure 2-5)

Hydrogen bonds (attraction of H to O or N)

e.g., between H2O molecules (Figure 2-4)

van der Waals forces (like dissolves like)

e.g., between lipid molecules (Figure 2-6)

Strength and type of chemical bonds and interactions:

STRONG

WEAK


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Some proteins include regions with covalent bonds

between sulfhydryl groups of non-adjacent cysteines.

Figure 2-20


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Figure 2-21

A three-dimensional, space-filling cartoon (partial) depiction

of hemoglobin, a protein that plays a key role in gas transport.


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DNA is made up of a chain of deoxyribonucleotides

and RNA is made up of a chain of ribonucleotides.

or:

adenine,

guanine,

thymine

or:

adenine,

guanine,

uracil

Figure 2-22


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The sequence of

bases in DNA and in

RNA is held together

by phosphate-sugarbonds.

You will learn later

how this sequence

is an information code.

Figure 2-23


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A T

G C

Hydrogen bonds between

complementary bases hold

together the DNA double helix.

Figure 2-25

Figure 2-24


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ATP serves as the energy currency of the cell since the

hydrolysis that removes one phosphate group is

accompanied by a discrete and controllable energy release.

Figure 2-26


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T

he End.

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