Topic 3: Macromolecules

What are macromolecules

Large complex molecules

What are the four classes in the cell of macromolecules?

Carbohydrates *Polymer

Lipids

Nucleic acids *Polymer

Proteins *Polymer

What are polymers?

Molecules consisting of many similar or identical building blocks linked by covalent bonds

What are monomers?

Small molecule used as a building block for polymers

What happens during the synthesis of polymers (dehydration reaction)?

Covalent bond formed between monomers

Water molecule is lost
Requires energy

Requires enzymes

What happens during the degradation of polymers ((hydrolysis reaction)?

Breaks covalent bonds between two monomers

adds H2O

releases energy

requires enzymes

What are the functions of sugar and sugar polymers?

Source of energy

Source of carbon to make other molecules

Structural components of the cell

Monomer: monosaccharide

“Simple sugar”

One carbonyl and many hydroxyls (one per carbon)

Forms rings in solution

Alpha glucose

Beta glucose

Glucose (aldehyde)

Fructose (a ketone)

Glucose (enantiomers)

Galactose

Are glucose and fructose enantiomers?

No they are structural isomers

What are Monosaccharides joined by to form polymers?

Joined by bond called glycosidic linage, it Is a covalent bond and is formed by dehydration reaction

Polysaccharides

More than 2 monosaccharides joined by glycosidic linkages

-Polymer

-2 functions: energy storage and structure

What is starch (storage polysaccharide)?

-Only found in plants

-Polymer of glucose monomers joined by α-1,4-glycosidic bonds

-Helical structure

What is glycogen (storage polysaccharide)?

o Found in animal liver and muscle cells, and bacteria

o Glucose polymer with α-1,4-glycosidic bonds

o Helical structure

o Branched

What is cellulose (structural polysaccharide)?

Found in plant cell walls

Polymer of glucose with β-1,4-glycosidic linkages

Unbranched, linear structure (not helical)

Forms strong bundles

What are lipids in cells

Fats

Phospholipids

Sterols

Characteristics of Lipids

At least partially hydrophobic

Lots of non-polar bonds
Low water solubility

Not polymer (but still macromolecule)

What are the functions of fat?

Energy source, insulation, protection

What are the two components of fat?

1) Glycerol

-3 carbons

2) Fatty Acids

-3 hydroxyl

What is fat made out of?

1 glycerol + 3 fatty acids = triacylglycerol (attached by ester linkages)

How is it formed?

Formed by dehydration reaction

What are the function of phospholipids?

Main component of cell membrane

What are the characteristics of phospholipids?

Are amphipathic (part hydrophobic, part hydrophilic)

Similar to fat, except 3rd C of glycerol attached to phosphate group

Spontaneously assemble into bilayers

-Acts as boundary between call and environment

What are the functions of sterols?

Cell membrane, signalling molecules

What are the properties of sterols?

-Non-polar

-Carbon skeleton of 4 fused rings

Functions and characteristics of cholesterol

-Component of anime cell membrane

-Precursor to all other sterols

-Synthesized in liver; consumed in animal fats

-High levels may clog arteries

What is variation in fatty acids due to?

Length of H-C chain

#, location, and type of double bonds

Structure of Saturated Fatty acids

No Double bonds

Straight molecules

→Can pack close together

→Solid at room temperature

Ex: Saturated fats, red meat, butter

Structure of Unsaturated fatty acids

One or more double bonds

Bend at double bond

→Can’t pack closely together

→Liquid at room temperature

Ex: Unsaturated fat, oils, fish, plants

Cis fatty acids

Hydrocarbon chain at the same side

natural

bent molecule

Trans fatty acid

Hydrocarbon chain opposite sides

Unnatural

Straight molecule 

Hydrogenated oils

Hydrogen synthetically added to unsaturated dats to remove double bonds

Done because it becomes less perishable, ore solid at room temp, don’t separate

Examples: Margarine, peanut butter

What are the two types of nucleic acids?

DNA and RNA

What are the functions of DNA?

Genetic material of the cell

Contains all instructions for cell structure and function

Direct its own replication

Directs RNA synthesis

What are the functions of RNA?

Carries all information in our cells

Essential for protein synthesis 

What is the composition of nucleic acid

Chain of nucleotides

Attached by phosphodiester linkage 

→3’ -OH of one nucleotide attached to 5’ -P of the next nucleotide 

Deoxyribonucleotide

Ribonucleotide

Thymine (T)

Adenine (A)

Cytosine (C)

Guanine (G)

DNA structure

2 strands twist around each other to form double helix

fixed width of 2nm

phosphodiester backbone on outside of helix

nitrogenous bases are inside helix

fixed width of double helix means a purine (2 ring nitrogenous base) must pay with a pyrimidine (one ring)

Composition of strands in DNA?

Strands are specifically connected by H bonds between bases

→called base pairs

→2 contacts between A and T

→2 contacts between C and G (stronger

Two strands are antiparallel

RNA strand composition?

Exists as a single strand

Each has a unique shape due to internal base pairing

Still follow are pairing rules

→ A and U (2 H bonds)

→ G and C (3 H bonds)

How are protein in cells?

Hemoglobin, collagen, insulin etc

Functions of protein?

Enzymes

Transport proteins

Hormones

Receptors

Motor proteins

Structural proteins

Structure of amino acid (monomer)

-Central (alpha) carbon

-Amino group

-Carboxyl group

-R group = 20 different structures

-Ionized in the cell

Four classes of amino acids?

Non polar

Polar, uncharged

Polar, positively charged

Polar negatively-charged

Structure and formation of the Polymer: Polypeptide

Chain of amino acid monomers

Covalent bond called peptide bond

▪ Carboxyl group of one AA covalently joined to amino group of the

next AA

▪ Formed by a dehydration reaction

How can a polypeptide be a protein?

A polypeptide is a linear polymer of amino acid monomers connected by peptide bonds

A protein is a polypeptide that has been folded into a unique 3D shape

What is a protein?

One or more polypeptides folded together into a specific shape

Has four levels of protein structures that all occur simultaneously

Primary structure of protein

Unique order of amino acids in a polypeptide

• Bond type: peptide covalent

• Determined by DNA sequence 

Secondary structure of protein

Repetitive coiling or folding of protein

• Bond type: H-bond in the polypeptide backbone

        o Between amino group of one AA and carboxyl group of another AA

alpha helix structure 

secondary structure and created by hydrogen bond in the backbone of polypeptide

-repetitive coiling

-H bond between every 4th amino acid in the helix

beta sheet 

second secondary structure

repetitive folding

2 regains of peptide chain lie side by side and are connected by hydrogen bonds

Tertiary structure 

• Overall shape of single polypeptide

• Due to interactions between

side chains

Hydrogen bond side chain location in tertiary structure

H bonds between polar side chains

Ionic bond side chain location in tertiary structure

Ionic bonds between oppositely charged side chains

Hydrophobic interaction side chain in tertiary structure

Non polar side chains aggregate inside protein and exclude water

Polar side chains exposed on protein surface and nteract with water

Disulfide bond side chain location in tertiary structure

__________________ between

the side chains of cysteine (AA) in _____________________

Quaternary structure 

Multiple polypeptides folded together

o Each has its own 1°, 2°, and 3° structure

• Stabilized by same 4 types of side chain interactions as 3° structure (H-bonds, Ionic bonds, Hydrophobic interactions, Disulfide bonds)

• Protein may contain

o Multiple copies of same polypeptide; OR

o Several different polypeptides

How can protein have so many functions?

Protein shape is directly related to function

o All polypeptides have the same backbone

o Each has a different order of amino acids → controls shape → controls function

What might possibly when changes to the primary structure occur?

Changes can alter or eliminate protein function

o Different amino acid in primary sequence =

→ different side chain

→ forms different bonds (in tertiary structure)

→ changes overall shape

→ different shape = different/no function

What if a protein unfolds?

Denaturation: When protein unfolds and loses its normal shale

Causes a loss of function

Primary sequence conservative changes to protein

New AA has same properties as old AA

→ Similar bonds can form

→ Change has minimal effect on function

Primary sequence non-conservative changes to protein

New AA has different than old AA  properties

→ Different bonds can form

→ Protein function is affected

What breaks interactions between side chains and causes a protein to denature?

High temperature

Change in pH

Organic solvents

Chemicals that disrupt bonds