Chapter 5 notes

The structure and function of

Macromolecules

Concept 5.1

Polymer: a long molecule consisting of similar or identical building blocks- like a train with many cars- monomers: repeating units that are the building blocks

Diversity of life is based around 40 or 50 polymers

Concept 5.1

Monomers are connected together by dehydration synthesis (anabolic)- covalent bond w/ the loss of H2O

Polymers are broken down by hydrolysis (catabolic)- reverse rxn. of dehydration synthesis- “break with water”

Concept 5.1

Dehydration removes a watermolecule, forming a new bond

Short polymer Unlinked monomer

Longer polymerDehydration reaction in the synthesis of a polymer

HO

HO

HO

H2O

H

H

H

4321

1 2 3

(a)

Concept 5.1

Hydrolysis adds a watermolecule, breaking a bond

HO

HO HO

H2O

H

H

H321

1 2 3 4

Concept 5.2

Carbohydrates: include sugars and polymers

Monosaccharides (monos = single; sacchar = sugar)- molecular formula is CH2O

- ex. Glucose (C6H12O6)

- most sugars are rings when aqueous

Concept 5.2

(a) Linear and ring forms (b) Abbreviated ring structure

Concept 5.2

Disaccharide: two monosaccharides joined by a glycosidic linkage- formed by dehydration synthesis- glucose + glucose = maltose + H2O

- glucose + fructose = sucrose + H2O

Concept 5.2

(b) Dehydration reaction in the synthesis of sucrose

Glucose Fructose Sucrose

MaltoseGlucoseGlucose

(a) Dehydration reaction in the synthesis of maltose

Concept 5.2

Polysaccharides: polymers w/ few hundred to a few thousand monomers-fcn. of a polysaccharide is determined by monomers and positions of glycosidic linkages

Concept 5.2

Storage polysaccharides- starch: found in plants; consists only of glucose monomers (1-4 linkage); how plants store glucose (chloroplasts)- glycogen: polymer of glucose found in animals; stored in liver and muscle cells

Concept 5.2

Structural polysaccharides- cellulose: major component of plant cell walls- note: 2 ring structures of glucose (alpha and beta )- cellulose is composed of all glucose- cellulose = “insoluble fiber”

Concept 5.2

(a) and glucose ring structures

Glucose Glucose

Concept 5.2

Concept 5.2

Glucosemonomer

Cellulosemolecules

Microfibril

Cellulosemicrofibrilsin a plantcell wall

0.5 µm

10 µm

Cell walls

Carbohydrates

Structural polysaccharides (cntd.)- chitin: carbohydrate used by arthropods to build exoskeletons

- also used to make decomposable surgical thread

Concept 5.2

The structureof the chitinmonomer.

(a) (b) (c)Chitin forms theexoskeleton ofarthropods.

Chitin is used to makea strong and flexiblesurgical thread.

Concept 5.3

Lipids: little or no affinity for water; consist mostly of hydrocarbons- 3 families: fats, phospholipids, steroids

Fat: composed of 2 parts- glycerol: 3 carbon alcohol w/ hydroxyl - fatty acids: long carbon skeletons w/ carboxyl groups

Concept 5.3

Fatty acid(palmitic acid)

(a) Dehydration reaction in the synthesis of a fat

Glycerol

Concept 5.3

Fatty acids can vary in length and in the number and location of double bonds- “saturated”: no double bonds; most animal fats; solid at room temp.- “unsaturated”: has one or more double bonds which removes H atoms; plants and fish; liquid at room temp.

Concept 5.3

(a) Saturated fat

Structuralformula of asaturated fatmolecule

Stearic acid, asaturated fattyacid

Concept 5.3

(b)Unsaturated fat

Structural formulaof an unsaturatedfat molecule

Oleic acid, anunsaturatedfatty acid

cis doublebond causesbending

Concept 5.3

The major fcn. of fats is energy storage.- 1g of fat stores more than twice as much energy as 1g of a polysaccharide- mammals stock food reserves in adipose cells

Concept 5.3

Phospholipids: similar to fats but have only 2 fatty acid tails; 3rd hydroxyl group joins to a phosphate group- show ambivalent behavior to water

- head= polar (hydrophilic); tail= nonpolar (hydrophobic)

- arranged in a bilayer, or double layer

Concept 5.3

(b)Space-filling model(a) (c)Structural formula Phospholipid symbol

Fatty acids

Hydrophilichead

Hydrophobictails

Choline

Phosphate

Glycerol

Hyd

rop

ho

bic

tai

lsH

ydro

ph

ilic

hea

d

Concept 5.3

Steroids: lipids with a carbon skeleton consisting of 4 fused rings- differ in functional groups attached to rings- Cholesterol: found in animal cell membranes; precursor for other steroids

Concept 5.3

Concept 5.4

Proteins: account for more than 50% of the dry weight of most cells- used for structural support, storage, transport, signaling, movement, and defense

Concept 5.4

Proteins are polymers constructed from the same set of 20 amino acids- called polypeptides- consist of one or more polypeptides folded and coiled into specific conformations

Concept 5.4

Amino acids are the building blocks of proteins- carbon is bonded to an animo group, a carboxyl group, a hydrogen atom, and a variable (R)- grouped according to side chains (nonpolar, polar, acidic, basic)

Concept 5.4

Concept 5.4

Concept 5.4

Amino acids are bonded together by a peptide bond- carboxyl group of one amino acid connects w/ the amino group of another (dehydration synthesis)

Concept 5.4

Concept 5.4

Four levels of protein structure- primary structure: unique sequence of amino acids- even a slight change can affect a proteins conformation and ability to function

- ex. Sickle-cell disease

Concept 5.4

Concept 5.4

- secondary structure: coils or folds that are a result of hydrogen bonds at regular intervals

- helix: delicate coil held together by hydrogen bonding between every fourth amino acid

- pleated sheets: two or more regions lie parallel to each other

Concept 5.4

Concept 5.4

- tertiary structure: irregular contortions from interactions between side chains (R groups)

- hydrophobic interactions: nonpolar side chains cluster in the core, away from water

- van der Waals interactions help hold them together

Concept 5.4

- disulfide bridges: covalent bond between two cysteine monomers (have sulfhydryl groups)

- ionic bonds and hydrogen bonds also contribute

Concept 5.4

Concept 5.4

- quaternary structure: overall protein structure resulting from combining of multiple subunits

The unique conformation endows each protein with a specific function

Concept 5.4

Concept 5.4

Concept 5.4

The unique conformation endows each protein with a specific function- denaturation: protein unravels and losses its conformation

- pH, [salt], temperature

Concept 5.5

Compounds that are responsible for determining the amino acid sequence of a polypeptide.

Two types of nucleic acids- deoxyribonucleic acid (DNA)- ribonucleic acid (RNA)

Flow of genetic information: DNA RNA Protein

Concept 5.5

mRNA

Synthesis ofmRNA in thenucleus

DNA

NUCLEUS

mRNA

CYTOPLASM

Movement ofmRNA into cytoplasmvia nuclear pore

Ribosome

AminoacidsPolypeptide

Synthesisof protein

1

2

3

Concept 5.5

Nucleotides are the monomers (building blocks) of nucleic acids-nucleotide = nitrogenous base + pentose (5-carbon sugar) + phosphate

Concept 5.55 end

Nucleoside

Nitrogenousbase

Phosphategroup Sugar

(pentose)

(b) Nucleotide

(a) Polynucleotide, or nucleic acid

3 end

3C

3C

5C

5C

Nitrogenous bases

Pyrimidines

Cytosine (C) Thymine (T, in DNA)Uracil (U, in RNA)

Purines

Adenine (A) Guanine (G)

Sugars

Deoxyribose (in DNA) Ribose (in RNA)

(c) Nucleoside components: sugars

Concept 5.5

Two families of nitrogenous bases:- pyrimidines: single ring; cytosine (C), thymine (T), and Uracil (U)

- purines: double ring; adenine (A), and guanine (G)

Concept 5.5

Difference between DNA and RNA is in the sugar. DNA lacks an oxygen atom attached to its number 2 carbon

Polynucleotide: nucleotides are joined by phosphodiester linkage

Concept 5.5

DNA molecules have two polynucleotides that form a double helix.- Watson and Crick (1953)- A binds to T; C binds to G; forms two complementary strands