The Amazing Molecule: Water

All living things are made of chemicals.

Understanding life requires an understanding of chemistry.

Biochemistry- the chemistry of life helps us understand todays biological questions!

Covers 75% of the earths surface

Single most abundant compound in all living things

Average male = 60% water

Average female = 50% water

Average infant = 73% water

H2O

Neutral Molecule

10 protons

10 electrons

With 8 protons in its nucleus, an oxygen atom has a much stronger attraction for electrons than does a hydrogen atom with its single proton.

The oxygen end of the molecule has a slight negative charge and the hydrogen end of the molecule has a slight positive charge

The attraction between a hydrogen atom on one water molecule and the oxygen atom

Because of their partial positive and negative charges, polar molecules such as water can attract each other.

Cohesion

Adhesion

Surface tension

High Heat of Vaporization

Universal Solvent

Facilitate Chemical Reactions

water molecules are drawn together, which is why drops of water form beads on a smooth surface.

Cohesion also produces surface tension, explaining why some insects and spiders can walk on a pond’s surface.

attraction between molecules of different substances.

a meniscus: because the adhesion between water molecules and glass molecules is stronger than the cohesion between water molecules.

A result of Cohesion

explaining why some insects and spiders can walk on a pond’s surface

large amount of heat energy is needed to cause those molecules to move faster and raise the temperature of the water until becomes vapor

Large bodies of water (oceans and lakes) can absorb large amounts of heat with only small changes in temperature. This protects organisms living within from drastic changes in temperature

Honor’s Biology

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Although a cell is mostly water, the rest of the cell consists mostly of carbon-based molecules

Organic chemistry is the study of carbon compounds that are necessary for life

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It has four electrons in an outer shell that holds eight

Carbon can share its electrons with other atoms to form up to four covalent bonds

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Attach to other carbons

Form an endless diversity of carbon skeletons

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Large molecules are called polymers

Polymers are built from smaller molecules called monomers

Biologists call them macromolecules

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Proteins

Lipids

Carbohydrates

Nucleic Acids

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Polymers are made by stringing together many smaller molecules called monomers

Nucleic Acid Monomer

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Cells link monomers by a process called dehydration synthesis (removing a

molecule of water)

This process joins two sugar monomers to make a double sugar

Remove

H

Remove OH

H2O Forms

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Also called “condensation reaction”

Forms polymers by combining monomers by “removing water”.

HO H

HO HO H H

H2O

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Cells break down macromolecules by a process called hydrolysis (adding a molecule of water)

Water added to split a double sugar

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Separates monomers by “adding water”

HO HO H H

HO H

H2O

Carbohydrates: Made up of monosaccharides

Lipids: Made up of glycerol and fatty acid molecules

Proteins: Made up of Amino acids

Nucleic acids: Made up of nucleotides

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Carbohydrates are made up of

simple sugars (monosaccharides):

Small sugar molecules in soft drinks

Long starch molecules in pasta and potatoes

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CHO Examples: A. monosaccharide B. disaccharide C. polysaccharide

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Monosaccharide: one sugar unit

Examples: Glucose (C6H12O6)

Fructose

Galactose glucose

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Glucose is found in sports drinks

Fructose is found in fruits

Galactose is called “milk sugar”

-OSE ending means SUGAR

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Glucose & fructose are isomers because their structures are different, but their chemical formulas are the same

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Disaccharide: two sugar unit

Examples: Sucrose (glucose+fructose)

Lactose (glucose+galactose)

Maltose (glucose+glucose)

glucose glucose

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A disaccharide is a double sugar

They’re made by joining two monosaccharides

Involves removing a water molecule (dehydration synthesis)

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Polysaccharide: many sugar units

Examples: starch (bread, potatoes)

glycogen (stored in liver)

cellulose (lettuce, corn)

glucose glucose

glucose glucose

glucose glucose

glucose glucose

cellulose

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Complex carbohydrates

Composed of many sugar monomers linked together

Polymers of monosaccharide chains

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Starch

Glycogen

Cellulose

Glucose Monomer

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Starch is an example of a polysaccharide in plants

Plant cells store starch for energy

Potatoes and grains are major sources of starch in the human diet

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Glycogen is an example of a polysaccharide in animals

Animals store excess sugar in the form of glycogen

Glycogen is similar in structure to starch because BOTH are made of glucose monomers

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Cellulose is the most abundant organic compound on Earth It forms cable-like fibrils in the tough walls that enclose plants

It is a major component of wood

It is also known as dietary fiber

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SUGARS

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Most animals cannot derive nutrition from fiber

They have bacteria in their digestive tracts that can break down cellulose

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Simple sugars and double sugars dissolve readily in water

They are hydrophilic, or “water-loving”

WATER MOLECULE

SUGAR MOLECULE

-OH groups make them water soluble

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Lipids are hydrophobic –”water fearing”

CHO

Do NOT mix with water

FAT MOLECULE

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General term for compounds which are not soluble in water.

Lipids are soluble in hydrophobic solvents. “stores the most energy”

Examples: 1. Fats 2. Phospholipids 3. Oils 4. Waxes 5. Steroid hormones 6. Triglycerides

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Five functions of lipids:

1. Long term energy storage

2. Protection against heat loss (insulation)

3. Protection against physical shock

4. Chemical messengers (hormones)

5. Major component of membranes (phospholipids)

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Triglycerides: composed of 1 glycerol and 3 fatty acids.

H

H-C----O

H-C----O

H-C----O

H

glycerol

O

C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3

fatty acids

O

C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3

O

C-CH2-CH2-CH2-CH

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Glycerol Fatty Acid Chains

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Unsaturated fatty acids have less than the maximum number of hydrogens bonded to the carbons (a double bond between carbons)

Saturated fatty acids have the maximum number of hydrogens bonded to the carbons (all single bonds between carbons)

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Single

Bonds in

Carbon

chain

Double bond in carbon

chain

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Most animal fats have a high proportion of saturated fatty acids & exist as solids at room temperature (butter, margarine, shortening)

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Most plant oils tend to be low in saturated fatty acids & exist as liquids at room temperature (oils)

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Dietary fat consists largely of the molecule triglyceride composed of glycerol and three fatty acid chains

Glycerol

Fatty Acid Chain

Condensation links the fatty acids to Glycerol

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• Cell membranes are made of lipids called phospholipids

• Phospholipids have a head that is polar & attract water (hydrophilic)

• Phospholipids also have 2 tails that are nonpolar and do not attract water (hydrophobic)

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The carbon skeleton of steroids is bent to form 4 fused rings

Cholesterol is the “base steroid” from which your body produces other steroids

Estrogen & testosterone are also steroids

Cholesterol

Testosterone

Estrogen

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Proteins are polymers made of monomers called amino acids

CHONS

All proteins are made of 20 different amino

acids linked in different orders

Proteins are used to build cells, act as

hormones & enzymes, and do much of the

work in a cell

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Amino acids have a central carbon with 4 things boded to it:

Amino group –NH2

Carboxyl group -COOH

Hydrogen -H

Variable group -R

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Cells link amino acids together to make proteins

The process is called

dehydration synthesis

Peptide bonds form

to hold the amino

acids together

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Four levels of protein structure:

A. Primary Structure

B. Secondary Structure

C. Tertiary Structure

D. Quaternary Structure

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Hydrogen bond

Hydrogen bond

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Amino acids bonded together by peptide bonds (straight chains)

aa1 aa2 aa3 aa4 aa5 aa6

Peptide Bonds

Amino Acids (aa)

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The primary

structure is the

specific sequence

of amino acids in

a protein

Called

polypeptide

Amino Acid

Secondary protein structures occur when protein chains coil or fold

Coil – alpha helix

Fold – beta sheet

Results from hydrogen bonds

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Secondary structures bent and folded into a more complex 3-D arrangement of linked polypeptides

Bonds: H-bonds, ionic, disulfide bridges (S-S)

Call a “subunit”.

Alpha Helix

Beta Pleated Sheet

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Composed of 2 or more “subunits” Globular in shape Form in Aqueous environments Example: enzymes (hemoglobin)

subunits

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Substitution of one amino acid for another in

hemoglobin causes sickle-cell disease

(a) Normal red blood cell Normal hemoglobin

1 2 3

4 5

6 7. . . 146

(b) Sickled red blood cell Sickle-cell hemoglobin

2 3 1

4 5

6 7. . . 146

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Blood sugar level is controlled by a protein called insulin

Insulin causes the liver to uptake and store excess sugar as Glycogen

The cell membrane also contains proteins Receptor proteins help cells recognize

other cells

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INSULIN

Cell membrane with proteins &

phospholipids

Enzymes are an important class of catalysts in living organisms Mostly protein

Thousands of different kinds

Each specific for a different chemical reaction

Often end in ase (lactase breaks down lactose)

Enzymes work on substances called substrates

Substrates must fit into a place on an enzyme called the active site

Enzymes are reusable!

The lactase enzyme breaks the bond between glucose and galactose so you can digest lactose (milk).

Lactose free milk contains the same sugars but they are already broken down = easier to digest for those lactose intolerant.

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Nucleic acids are composed of long chains of nucleotides linked by dehydration synthesis.

CHONP

Function: Dictate amino acid sequences/how proteins are made

Source of all genetic information

Two types:

a. Deoxyribonucleic acid (DNA)

b. Ribonucleic acid (RNA)

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O

O=P-O

O

Phosphate

Group

N

Nitrogenous

base

(A, G, C, or T)

CH2

O

C1 C4

C3 C2

5

Sugar

(deoxyribose)

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Nitrogenous base (A,G,C, or T)

Phosphate group

Thymine (T)

Sugar (deoxyribose)

Phosphate

Base

Sugar

Nucleic acids

are polymers of

nucleotides

Nucleotide

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Nucleotides include: phosphate group pentose sugar (5-carbon) nitrogen bases: adenine (A) thymine (T) DNA only uracil (U) RNA only cytosine (C) guanine (G)

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Each DNA nucleotide has one of the following bases:

Thymine (T) Cytosine (C)

Adenine (A) Guanine (G)

–Adenine (A)

–Guanine (G)

–Thymine (T)

–Cytosine (C)

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Two strands of DNA join together to form a double helix

Base pair

Double helix

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P

P

P

O

O

O

1

2 3

4

5

5

3

3

5

P

P

P O

O

O

1

2 3

4

5

5

3

5

3

G C

T A

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Ribose sugar has an extra –OH or hydroxyl group

base uracil (U) instead

of thymine (T)

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ATP is used by cells for energy

Adenosine triphosphate

Made of a nucleotide with 3 phosphate groups

Organic Compounds Lab

A substance used to show the presence of another substance

Color change = positive test

(the substance is present)

Use it as a control – to make sure the indicators are working.

No color change with water = indicators are working

Sudan III stain – red is a positive test

Brown paper bag – Lipids leave translucent spots (grease spots)

Starch – Iodine- blue/black is a positive test

Sugar – Benedict’s solution – **MUST BE HEATED!!!!*

blue/green changes to orange/yellow = positive test

Biuret reagent - varying shades of purple = positive test