1!Spider’s web and close up of capture strand - spider silk protein

Chp 2 (cont.) Organic Molecules

Molecular Diversity is Based on Carbon

An organic molecule contains both carbon and hydrogen. Ex: Methane - a simple organic molecule

C atoms can bond to 4 other atoms – chains, rings, branches

A chain of C atoms is called a carbon skeleton

Methane

Double bonds.

2-Butene Skeletons may have double bonds, which can vary in location.

Cyclohexane

1-Butene

Benzene Skeletons may be arranged in rings. Rings.

3!

What is the chemical formula for Butane and Isobutane?

Carbon skeletons vary in length.

Branching. Skeletons may be unbranched or branched. Butane Isobutane

Propane Ethane Length.

Carbohydrate polymer

Protein polymer

Nucleic acid polymer Monomer

Monomer Monomer

4!

  Large organic molecules are called macromolecules

–  Aka. polymers b/c they are made from same units linked together (draw train cars linked)

–  The repeating units are called monomers

Cells Make Lots of Large Molecules From a Limited Set of Small Molecules

5!

 During dehydration synthesis, an enzyme binds two monomers, releasing a water molecule

Building a polymer chain

H

OH H

OH

H OH

Unlinked monomer

Dehydration reaction

Longer polymer

Short polymer

OH H

H OH

Unlinked monomer

Dehydration reaction

Short polymer

H2O

6!

 Hydrolysis is the reverse reaction, it breaks polymers into monomers

Breaking a polymer chain

H

H2O

OH

H OH OH H

Hydrolysis

7!

 Carbohydrates include small simple sugars and large polysaccharides

– Monosaccharides are the monomers of carbs

– Exs: Glucose and Fructose

Bees with honey, a mixture of 2 different monosaccharides

Organic Molecules: Carbohydrates

What do you think a chemical formula would be for “carbo” “hydrate”?

8!

 Molecular formula of a monosaccharide is a multiple of CH2O –  Glucose is C6H12O6

Monosaccharide structures

 Monosaccharides are the main fuel for cellular work

9!

  Two monosaccharides can join to form one disaccharide (a dehydration synthesis reaction)

– Glucose bonding to fructose forms sucrose, table sugar

– Glucose linked to galactose = lactose, sugar found in milk

What problem is associated with this disaccharide in some people?

10!

 Starch and glycogen = polysaccharides in plant and animal respectively, storage of ___________

 Cellulose = polysaccharide in plant cell walls, structural support

Polysaccharides are long chains of carbohydrates

11!

  Lipids = hydrophobic (water _________ )

–  Long-term energy storage

–  Not large

–  Not built of monomers

  Fats = lipids made from glycerol and fatty acids

–  Long hydrocarbon chains

–  Saturated fatty acid vs. unsaturated fatty acid

Organic Molecules: Lipids

Formation of a fat molecule

13!

Phospholipids & Sterols are Also Lipids

  Phospholipids = main component of cell membranes

  Similar to fats, but imp. differences

— Two fatty acids

— Hydrophilic head and hydrophobic tails

✶  Form stable bilayer in water

 Steroids = lipids with 4 fused rings

 Cholesterol = common component of animal cell membranes

– Starting material for sex hormones

– Too much in the blood can lead to atherosclerosis

Fig. 3.9C Cholesterol, a type of steroid

14!

15!

Atherosclerosis  

16!

  The monomers of proteins are amino acids

–  Protiens; hair, cartilage, muscle, antibodies, enzymes, hemoglobin

–  3-D structure directly related to function

–  Made from genetic info (DNA) found in the _______ of the cell

Organic Molecules: Proteins

17!

 Amino acids structure: amino group, carboxyl group, central carbon atom, and an R group

  Linked together by dehydration reactions   Links called peptide bonds

–  Carboxyl group bonded to amino group (C-N bond)

Fig 3.11C Peptide bond formation

H

H

N C C O

OH H

H N + C

H

R

C O

OH H2O

H

H

N C C N C C

R H R OH

O

Peptide bond

Dipeptide Amino acid

Dehydration reaction

Amino group

H

R

Amino acid

Carboxyl group

H O H

18!

 A polypeptide chain has hundreds or thousands of aa’s linked by peptide bonds

–  Amino acid sequence of polypeptide determines shape

–  Shape determines its specific function

Polypeptides must fold into a protein to work

Groove Groove

Space-filling model of lysozyme Ribbon model of lysozyme

Four Levels of Protein Structure

Amino acids

Primary structure

Alpha helix

Hydrogen bond

Secondary structure Pleated sheet

Polypeptide (single subunit of transthyretin)

Tertiary structure

Transthyretin, with four identical polypeptide subunits Quaternary structure

19!

  If protein’s shape is altered, it may no longer function

– Denaturation = polypeptide chains unravel, lose their shape, and lose their function

– Can happen w/ changes in salt concentration, heating, changes in pH

– Ex. Frying an egg (egg white is protein)

20!

21!

Organic Molecules: Nucleic Acids

 DNA and RNA are nucleic acids

 Monomers of nucleic acids are nucleotides

✶ Nucleotides have 3 parts

– A 5-C sugar called ribose in RNA and deoxyribose in DNA

– A phosphate group

– A nitrogenous base A nucleotide

22!

There are 5 types of nucleotides

Nucleotides form nucleic acids

 DNA - 2 polynucleotide strands wrap around each other, double helix –  2 strands are held together

by __________ bonds

–  A pairs with T, and C pairs with G, producing base pairs

 RNA is a single strand

Figure 15C DNA double helix 23!

Clicker Question #5

Which monomer is incorrectly paired?

A.  protein: monopeptide B.  carbohydrate: monosaccharide C.  nucleic acid: nucleotide D.  lipid: no monomer

2.5 Mastering Concepts

Explain hydrolysis and dehydration synthesis in large molecules