Comparison of Ionic, Polar Covalent, and Nonpolar Covalent Bonds

Formation of an Ionic Bond

• A valance electron from Na is transferred to Cl• Cl now has 18e and 17p resulting in a – charge• Na has 10e and 11P resulting in a + charge.

Nonpolar and Polar Covalent Bonds

Non polar covalent Bonds equally share electrons

Polar covalent bonds share electrons unequally

Hydrogen Bonds• Too weak to bind atoms together

– (intra-molecular bonds= within molecule)

• Important as inter-molecular bonds– between to different molecules– Important for giving proteins (enzymes) and

DNA both shape and functionality.

• Hold water molecules together– Responsible for surface tension in water

Hydrogen Bonds in Water

Hydrogen Bonds

Properties of Water• Water makes up to 50-80% of all living cells. • Water stabilizes internal temperature of the body

– Hydrogen bonds stabilize large shifts in temperature

• Evaporate cooling (sweating) is critical from maintaining 98.6 degrees temperature in hot environments or increased physical workloads.

• Water is necessary for all biochemical reactions that take place in the body.

Polarity of Water

• Oxygen has a greater electronegativity.

• Hydrogen’s one electron spend more time in Oxygen's outermost energy level.

• The result is more electrons around the oxygen making it more negative.

• Hydrogen losses its electron. Its proton is unopposed making it more positive.

Properties of Water

• Water makes up to 50-80% of all living cells. • Water stabilizes internal temperature of the body

– Hydrogen bonds stabilize large shifts in temperature

• Evaporate cooling (sweating) is critical for maintaining 98.6 degrees temperature in hot environments or increased physical workloads.

• Water is necessary for all biochemical reactions that take place in the body.

Properties of Water• Water is a powerful splitting agent. (Hydrolysis) means

water splitting. Occurs in breaking down reactions• Is known as the universal solvent. ( Polarity allows it to

dissolve stuff.) water molecules slit the ionic bonds in Na+Cl-

Polarity

• Polar molecules associate with water and will dissociate from lipids (fats) . – Polar = hydrophilic (philic = loving)– Lipophobic (lipid fearing)

• Non-polar molecules associate with lipids will not associate with water and are considered to be – Non-polar = hydrophobic (water fearing)– Lipophilic= Lipid loving

Organic Compounds• Organic compounds contain carbon as the backbone.

• It has the ability to create 4 covalent bonds which is important for making large complex structures.

• Organic compounds include :– Carbohydrates (sugars)– Lipids (fats and oils)– Proteins ( muscle, enzymes)– Nucleic acids (DNA and RNA)

• They may be built up or broken down depending on what the system requires.

• May have a variety of functional groups

Dehydration Synthesis

• Dehydrate( remove water)/ Synthesis( Build) • Monomers bond together to form a polymer with the

removal of a water molecule (dehydration)• Removal OH– of one and H+ of the other hydroxyl group

forms the water. – A covalent bond will result.

Hydrolysis

• Translates into Water/splitting• Addition of a water to a polymer causes (lysis) of the

covalent bond joining the 2 monomers.– Reestablishes the hydroxyl groups in both monomers

• All digestion reactions consists of hydrolysis reactions

Monomers/Polymers

Carbohydrates Monosaccharides Polysaccharides

Fats (lipids) Glycerol + 3 fatty Acids Triglycerides

Protein Amino acids Polypeptide

Nucleic Acidsnucleotides DNA, RNA

Dehydration Synthesis

Hydrolysis

CarbohydratesHydrophilic organic molecule that : contain carbon, hydrogen, and

oxygen 1:2:1 atomic ratio( carbo/carbon:hydrate/H2O)

– i.e. glucose = C6H12O6

• Names of carbohydrates– word root sacchar- or the suffix -ose often used

• Glucose is a monosaccharide which functions as a major fuel source for the cells.

Carbohydrates

• Dehydration synthesis reactions allow the cell store excess carbohydrates in the form of glycogen.

• Hydrolysis reactions allow the cell to break the bonds holding the polysaccharide together allowing it to release more simple sugars.

Disaccharides

• Major disaccharides– sucrose = table sugar

• glucose + fructose– Lactose = sugar in milk

• glucose + galactose– Maltose = grain products

• glucose + glucose

• All digested carbohydrates converted to glucose broken down in ATP (Cellular fuel).

Glycogen• Glycogen is an energy storage polysaccharide produced

by animals. 2 storage sites:– Liver cell: synthesize glycogen after a meal which can be broken

down later to maintains blood glucose levels.– Muscle cells: Store glycogen within the muscle at is only used by

the muscle cell.

Starch and Cellulose• Starch: is the storage form of sugar produced by plants. We

produce an enzyme that breaks the bonds between the sugars allowing digestion to occur. i.e. potatoes and grains

• Cellulose: provides structure to plants but contains a different type of bond. The β form is insoluble because we don’t produce the enzyme .i.e. dietary fiber

Lipids• Hydrophobic organic molecule

– Composed of carbon, hydrogen and oxygen– Better fuel source since it contains many more carbon and

hydrogen molecules.• There is an unlimited supply.

• Chain of 4 to 24 carbon atoms– carboxyl (acid) group on one end, methyl group on the

other and hydrogen bonded along the sides

• Classified – saturated - carbon atoms saturated with hydrogen – unsaturated - contains C=C bonds without hydrogen

Lipids Found in the Body

• Neutral fats – found in subcutaneous tissue and around organs.

• Phospholipids – chief component of cell membranes

• Steroids – cholesterol, bile salts, vitamin D, sex hormones, and adrenal cortical hormones

• Eicosanoids – prostaglandins, leukotrienes, and thromboxanes: – These play a role in various reactions in the body such as

inflammation and immunity.

• Lipoproteins – transport fatty acids and cholesterol in the bloodstream

• Fat-soluble vitamins – A,D, E, and K

Triglycerides

• Functions– energy storage in adipose (fat) tissue– Fats contain 9 kcal per gram where as

carbohydrates and proteins contain 4 kcal per gram.

• They contain more energy rich hydrogen.

– insulation • Prevent heat loss from the body

– protection• Adipose tissue cushions the organs.

Triglycerides (Neutral Fats)• Contain C, H, and O, but the proportion of oxygen in

lipids is less than in carbohydrates 3 • Fatty acids are bonded to a glycerol molecule during

dehydration synthesis.• At room temperature : Contain double bonds.

– when liquid called oils• often mono and polyunsaturated fats from plants

– when solid called fat• saturated fats from animals.

– No double bonds.• Function - energy storage, insulation and shock

absorption

Neutral Fats (Triglycerides)

• Composed of three fatty acids bonded to a glycerol molecule

Phospholipids

• Modified triglycerides with two fatty acid groups and a phosphorus group

Protein Functions– Catalysts

• proteins which are enzymes significantly increase the rate of a chemical reaction i.e. Salivary Amylase increases the rate of hydrolysis of starch.

– Structural• hold the parts of the body together i.e. collagen, elastin

and keratin – Communication

• act as chemical messengers between body areas .i.e. hormones such as insulin.

– Transport• allow substances to enter/exit cells• Carry things in the blood i.e. hemoglobin, lipoproteins,

Protein Functions

– Movement• Actin and myosin function in muscle contraction

– Defense• Antibodies( immunoglobulins) recognize and

inactivate foreign invaders( bacteria, toxins, and some viruses)

– Metabolism• Help regulate metabolic activities, growth and

development

– Regulation of pH• Plasma proteins such as albumin can function both

as an acid or a base. Therefore have an important role as a buffer

Amino Acids Structure

• Building blocks of protein• Amino and carboxyl

group groups are common in all Amino acids.

• R-group (radical group): 20 amino acids are different both structurally and from a functional level.

Different R- groups

Protein• Macromolecules composed of combinations of 20 types of amino

acids bound together with peptide bonds• Animal ,dairy and right combination of beans and rice are good

sources of protein.• Enzymes are specific types to proteins that enable reactions.

Protein Structure• Primary structure

– amino acid linked together by peptide bonds. The order of the amino acids critical for both form and function. No hydrogen bonds formed.

• Secondary structure :The primary structure will now form hydrogen bonds and take one of 2 forms: – α helix (coiled), β-pleated sheet (folded)

• Tertiary structure– more hydrogen bonds form and increased interaction

between R groups in surrounding water results in protein taking a globular 3 dimensional shape.

• Quaternary structure– two or more separate polypeptide chains conjugate and form

a functional protein• Hemoglobin.

Structural Levels of Proteins• Primary – amino acid sequence• Secondary – alpha helices or beta pleated

sheets

Structural Levels of Proteins

• Tertiary – superimposed folding of secondary structures– Most enzymes are in this form.

• Quaternary – polypeptide chains linked together in a specific manner

Functional Proteins (Enzymes)

• Enzymes are chemically specific. They fit a specific substrate like a lock and key.

• Enzyme names usually end in –ase – for example Lactase will be specific for the substrate

lactose ( Glucose Galactose)» Gycosidic bond

• Frequently named for the type of reaction they catalyze i.e. hydrolases add water during hydrolysis reactions.

• lipase/lipids, protease/ proteins,• Act as biological catalysts which lower activation energy

allowing reactions to occur at faster rates.

Activation Energy

• Activation energy refers to the extra energy required to break an existing chemical bonds and initiate a chemical reaction.– Activation energy determines rate of reaction

(higher activation energy = slower reaction)– catalyst - substance that lowers the activation

energy by influencing (stressing) chemical bonds

Characteristics of Enzymes

Enzymatic Reaction Steps

Enzyme Substrate Complex

• Enzymes need their 3 dimensional structure – created by both Hydrogen

and disulfide bonds which is specific to a certain substrate.

– Proper conditions are needed to keep these enzymes functioning.

– pH – Temperature

Protein Denuaturation

• Hydrogen bonds are broken and tertiary level protein reverts back to primary structure. Peptide bonds are still intact.

Protein Denuaturation

• Proteins will become denatured if: – ∆ pH – ↑ temperature

• Hydrogen bonds are broken from complex tertiary level proteins to basic primary structure. – Peptide bonds are still

intact.• Visible changes you see

when frying an egg

Nucleic Acids

• Two major classes – DNA and RNA

• Composed of carbon, oxygen, hydrogen, nitrogen, and phosphorus

• Five nitrogen bases contribute to nucleotide structure

• Adenine (A) Thymine (T)

• Guanine (G) Cytosine (C)

• Uracil (U) replaces Thymine in RNA

NucleotidesThe structural unit of the a nucleotide is composed of • N-containing base A,T,C,G and U in RNA• Pentose sugar: Ribose, and deoxyribose • Phosphate group

Deoxyribonucleic Acid (DNA)

• Double-stranded helical molecule confined in the nucleus of the cell

• Helical shape is a result of H-bonds between a purine on one strand and a pyramidine on the other strand– A only pairs with T– G only pairs with C

• Replicates itself before the cell divides, ensuring genetic continuity

• Provides instructions for protein synthesis

Structure of DNA

Structure of DNA

Ribonucleic Acid (RNA)

• Single-stranded molecule • Made from the nucleotides that complimentary pair • A U G C• Three varieties of RNA: 1. messenger RNA: transcribe DNA and carry it out of

nucleus. 2. transfer RNA: Bring amino acids to site of protein

synthesis (ribosome). 3. ribosomal RNA: building blocks of ribosomes ,made

in the nucleolus

Adenosine Triphosphate (ATP) Adenine-containing RNA nucleotide with three

phosphate groups• Second and third phosphate groups are

attached by high energy covalent bonds• The 3rd high energy phosphate bond of ATP is

hydrolyzed producing ADP + P + energy– The cell can recycle the ADP and P back into

ATP using the energy harvested from dietary foods primarily carbohydrates and lipids.

• Source of immediately usable energy for the cell.– It is the currency that all cellular reactions

accept.

Adenosine Triphosphate (ATP)

Figure 2.22

How ATP Drives Cellular Work

Figure 2.23