Unit 1: Cellular Energetics

• Part I – Macromolecules

• Part II – Enzymes

• Part III – Cellular Respiration

• Part IV – DNA Replication

• Part V – Protein Synthesis

Part I – Macromolecules

The questions:

• What are monomers? What are polymers?

• How are polymers synthesized (built) and hydrolyzed (broken down)?

Dehydration Synthesis (condensation)

– Reaction that joins molecules together by removing water

– Polymerization = the synthesis of a polymer– Polymers are built from monomers via dehydration

synthesis

• Breaks polymers into their constituent monomers (“building blocks”) by lysing (breaking) bonds through the addition of water.

Hydrolysis

1. Carbohydrates (polysaccharides)• Contain CHO

• General molecular formula = CH2O

• Aldoses and Ketoses vary in location of carbonyl group -C=O– Aldoses have carbonyl on ends (glucose)– Ketoses have carbonyl within molecule (fructose)

Monomer = monosaccharide

Disaccharides (double sugars)

• 2 monosaccharides joined by a glycosidic linkage– Covalent bond formed between two monosaccharides

by dehydration synthesis

Examples of disaccharides• Maltose = glucose + glucose

• Sucrose = glucose + fructose

• Lactose = glucose + galactose

Polysaccharides (many sugars)• Long polymers of many monosaccharides

• Architecture & function determined by position of glycosidic linkages– Alpha linkages are breakable by Eukaryotes

• Starch, glycogen

– Beta linkages are NOT • Cellulose, chitin

Types of Polysaccharides

A. Structural polysaccharides: – Beta glycosidic linkages– Cellulose - plant cell walls, structural molecule– Chitin - exoskeleton in insects, arachnids,

crustaceans

B. Food storage molecules – Alpha glycosidic linkages– Starch- food storage molecules in plants– Glycogen- food storage molecules in animals

2. Lipids

• Group shares one common trait – no affinity for water

• Do NOT consist of monomers → polymers• Highly varied group• Biologically important:

– Fats– Phospholipids– Steriods

A. Fats

• Made of glycerol and 3 fatty acids• Saturated fatty acids (animal fats) are carbon

chains with single bonds only– Ex: Butter, lard; solids at room temp.

• Unsaturated fatty acids (plant fats) have at least one double bond (kinks in chain)– Monounsaturated = only one double bond– Polyunsaturated = many double bonds

• Ex: Vegetable oils; liquid at room temp

“Hydrogenated” fatty acids

• Hydrogen is artificially added to replace double bonds with single bonds.

• Liquids are solidified

• Ex: peanut butter, margarine

B. Phospholipids

• 2 fatty acids (tails) attached to phosphate group “head”

• When placed in water they self assemble into a micelle

C. Steroids

• Lipids characterized by carbon skeletons consisting of four fused rings

• Ex. Cholesterol– Common component of animal cell membranes (this

is why animal meat is higher in cholesterol)– Precursor from which other steroids, including sex

hormones, are synthesized

3. Proteins

• Most diverse of all macromolecules

• Humans have over twenty thousand proteins in their bodies, each performing a specific function

General Categories of Proteins

1) Structural: Spider silk

2) Storage : Egg white

3) Transport: Hemoglobin

4) Hormonal: Insulin

5) Receptor: Transport protein

6) Contractile: Actin & myosin

7) Defensive: Antibodies

8) Enzymatic: Digestive enzymes

Monomers = Amino Acids• 20 total amino acids• 8 “essential” AA’s; must be derived from food• 12 can be synthesized by body• THREE TYPES

– Non-polar (8)– Polar (7)– Electrically charged (acidic, basic) (5)

General structure of amino acid

• All amino acids have a carboxyl group (-COOH) on one end and an amino group (NH

3) on the other

• R group determines their interactions with one another to form secondary, tertiary, and quaternary structure

Polymers = polypeptides

• Formed by dehydration synthesis

• Peptide bonds: bonds between adjacent amino acids

Protein shape determines function

• Primary structure: sequence of amino acids

• Secondary Structure: coiling or folding of polypeptide chain in repeated patterns– Ex: Alpha helices– Ex: Beta pleated sheets

• Tertiary structure: irregular contortions from interactions between side chains (R-groups) with one another– H-bonds– Disulfide bridges– Hydrophobic interactions

• Quaternary structure: 2 or more polypeptide chains aggregated into 1 functional molecule

4. Nucleic Acids

• Nucleic acids are the building blocks of both DNA and RNA– DNA directs its own replication, transmits

genetic information to future offspring, and controls RNA synthesis

– RNA controls protein synthesis

Nucleotides

Monomer = Nucleotides

• Nucleotide - building block of nucleic acids

• Composed of three subunits:

1) Pentose sugar (ribose or deoxyribose)

2) Phosphate groups comprise the “sugar-phosphate” backbone

3) Nitrogenous bases = variable portions of the molecule

DNA vs. RNA

Polymer = polynucleotide• Adjacent nucleotides are

joined by covalent bonds called phosphodiester linkages between the -OH on one nucleotide and the phosphate on the next nucleotide

Complementary Base Pairing• Always a Pyrimidine with a Purine

– Purines are Adenine & Guanine– Pyrimidines are Cytosine, Thymine (DNA only),

and Uracil (RNA only)

Complementary Base Pairing

Why Do Bases Bond This Way?

• Hydrogen bonds:– A and T form two hydrogen bonds

– G and C form three hydrogen bonds

• Therefore, there is no way to bond inappropriately

Base Pairing

A

T

Base Pairing G

C

Macro Structure of DNA

• Double Helix- “Twisted Ladder” of A-T and G-C base pairing

• DNA contains genes (thousands) that code for proteins

• In association with proteins (histones) DNA makes chromosomes (46 in humans)

• Stored in nuclei of Eukaryotic cells