Molecules

Macromolecules

Large molecules composed of smaller molecules

Complex in structure

Monomer, polymer, isomer

Monomer → single unit of a polymer (e.g. an amino acid or sugar)

Polymer → repeater units (e.g. glycogen or protein)

Isomer → similar make up of atoms, different structure

Polymer characteristics

Long molecule consisting of many similar building blocks → e.g. carbs, proteins, nucleic and fatty acids

Can disassemble by hydrolysis

Assemble by dehydration

Four types of organic molecules

Carbohydrates → “the sugars”

Proteins → made from amino acids

Fats → steroids, fatty acids, eicosanoids, triglycerides

Nucleic acids → in DNA and RNA

Fuel sources for the body

Glucose and simple sugars

Glycogen → polymer of glucose

Fats/fatty acids → polymers of hydrocarbons

Proteins and peptides

Monosaccharides characteristics

Simple sugars → easy to break down for energy or stored as glycogen

May be linear or can form rings

Aldoses → aldehyde group, HC=O at end

Ketones → ketone group, C=O middle

Disaccharides characteristics

Two simple sugars bond → enzymes break them down easily in digestion

Polysaccharides characteristics

Storage form for sugars → gylcogen (in animals), starch, cellulose

Storage polysaccharides (glycogen, starch)

Glycogen → glucose monomers, storage form of glucose animals (liver and muscle)

Starch → polymer of glucose, plants, easy to break down in digestion

Structural polysaccharides (cellulose)

Cellulose → is a polymer of glucose (plant cell walls)

• is difficult to break down → microbes partially digest, “fibre”

Fibre (soluble fibre)

Complex carb

Soluble fibre:

• sources → whole grains, fruits, legumes, seeds and husks, vegetables

• Lower blood cholesterol by binding dietary cholesterol so less absorbed

• Slow glucose absorption

• Holds moisture in stools, softening them

• May lower risk of heart disease and diabetes

Fibre (insoluble fibre)

Insoluble fibre:

• increase fecal weight → helps form soft, bulky stools which improve GI motility

• May reduce risk of constipation, hemorrhoids, diverticulosis, and colon cancer

• Speed fecal passage through colon

• Provide bulk and feelings of fullness

Sources → brown rice, fruits, legumes, seeds, vegetables, wheat bran, whole grains

Lipids - fats characteristics

Lipid-soluble, not water soluble

Non-polar

Hydrophobic

Constructed from a single glycerol and usually three fatty acids

Fat acids characteristics

Hydrocarbon chains

Fatty acids can be saturated or unsaturated

Saturated and unsaturated fatty acids

Saturated:

• maximum number of hydrogen atoms → have no double bonds

• Tend to be solid at room temperature

Unsaturated:

• one or more double bonds

• Usually liquid at room temperature

Triglycerides characteristics

Fat consists of a glycerol sugar plus 3 fatty acid chains

Triglycerides proved protection, insulation, and energy

Phospholipid characteristics

Have only two fatty acids → and a phosphate

An important component of cell membranes:

• amphiphatic → has polar and non-polar regions, non-polar regions make it impermeable to water

• Has a bilayer arrangement found in cell membranes

Steroids characteristics

Important group of hormones:

• cholesterol base

• Reproductive hormones

• Cortisol is stress hormone

Signalling lipids (eicosanoids, leukotrienes)

Eicosanoids:

• signalling molecule (hormone-like) in the immune response, childbirth, blood pressure control and cell growth (prostaglandins)

Leukotrienes:

• released from mast cells and basophils → signal for swelling and inflammation in the lung

Proteins characteristics

Structure to the body, regulate processes, provide protection, assist in muscle contraction, transport substances, and serve as enzymes

Proteins in cell membranes → act as receptors, carriers, channels

Enzymes characteristics

Acts as a catalyst, speeding up reactions

Most body reactions require enzymes

Tripeptide characteristics

Consists of three amino acids linked together

Amino acid sequences

Can vary resulting in almost an endless number of combinations

Each amino acid has unique chemical characteristics and electrical charges, the resulting shapes can be very complex

Protein structure

Amino acids

Dipeptides / peptides → 2 or more amino acids linked together by peptide bonds

Polypeptides → longer chains

Proteins → several polypeptides bonded together for functions

Denaturation

Protein unravels and loses its conformation → e.g. changes in pH or temperature

Renaturation is rare

Nucleic acids characteristics

Deoxyribonucleic acid (DNA) → double helix, genetic code

Ribonucleic acid (RNA) → single-stranded, guides protein synthesis

DNA vs RNA

Made up of nucleotides → polynucleotides are chains of nucleotides

Nucleotides characteristics

Each contains phosphate group, sugar and nitrogenous base → nucleoside is sugar and nitrogenous base

Nucleotide monomers

Made up of nucleosides and phosphate groups

The nitrogenous bases of DNA:

• form hydrogen bonds

• Complementary fashion → A with T only, C with G only

Nucleotide polymers

Nucleotides linked by the -OH group on the 3‘ carbon of one nucleotide and the phosphate on the 5’ carbon on the next

The sequence of bases is unique in each gene

The DNA double helix characteristics

Two polynucleotides that spiral around an imaginary axis

• form a double helix

• Anti parallel

Adenosine Triphosphate (ATP)

ATP is the principal energy-storing molecule in the body