Macromolecules

BIOLOGICAL MACROMOLECULES

Carbohydrates

Proteins

Macromolecules

Lipids

Nucleic Acids

Monosaccharides

Carbohydrates

Carbohydrates' formula: CH2O Carbohydrates are classified into three subtypes

Disaccharides

Polysaccharides

• simple sugars, from 3-7 carbons. the most common are glucose, galactose, and fructose (C6H12O6).
• most monosaccharide names end with -ose.
• if it has an aldehyde group, it is an aldose
• if it has a ketone group, it is a ketose
• depending on the number of carbons, the names might vary.
• 3 carbons → trioses
• 5 carbons → pentoses
• 6 carbons → hexoses
• they can exist as linear chains, or as ring-shaped molecules.

• are formed when two monosaccharides undergo a dehydration reaction.
• a hydroxyl group of one molecule is combined with the hydrogen of another monosaccharide forming a covalent bond.
• this covalent bond is known as a glycosidic bond, they can be alpha or beta type.
• common disaccharides are
• lactose → composed of monomers glucose and galactose, found in milk.
• maltose → malt sugar, formed by a dehydration of two glucose molecules.
• sucrose → table sugar, composed of monomers glucose and fructose.

• a long chain of monosaccharides linked by glycosidic bonds. It might contain different types of monosaccharides.
• The most common polysaccharides are
• starch
• a mixture of amylose and amylopectin (polymers of glucose).
• in plants, provides food for the germinating embryo, and it is also a source of food for humans and animals
• glycogen
• made up of monomers of glucose.
• equivalent of animal starch. it is found in the liver and in muscle cells.
• cellulose
• made up of glucose monomers
• cell wall of plants is mostly made of cellulose.
• chitin
• made up of glucosamine, contains nitrogen.
• major component of fungal cell walls.

Fats and oils

Lipids

Mostly nonpolar compounds. Nonpolar molecules are hydrophobic. Lipids are classified into5 types:

Phospholipids

Steroids

Waxes

• fat molecule is made of glycerol and fatty acids.
• glycerol is alcohol with 3 carbons, 5 hydrogens, and 3 OH.
• fats are also called triacylglycerols or triglycerides.
• fatty acids are either saturated or unsaturated.
• saturated → there are only single bonds between carbons in the hydrocarbon chain.
• unsaturated → When the hydrocarbon chain contains a double bond
• most unsaturated fats are known as oils.
• cis fats → when hydrogens are present in the same plane
• trans fat → when hydrogen atoms are on two different planes.

• hydrophobic nature
• made up of long fatty acid chains esterified to long-chain alcohols.

• major constituents of the plasma membrane (outermost layer of animal cells)
• composed of a hydrophilic head (phosphate and glycerol), and hydrophobic tails (saturated and unsaturated fatty acids).

• have a fused ring structure
• they are included in lipids because of their hydrophobic nature and their insolubility in water.
• most common steroids are
• cholesterol
• cortisol

Enzymes

Proteins

Proteins are structural, regulatory, contractile, or protective They may serve as transport, storage, or membranes

Amino Acids

Structures

Hormones

• catalysts in biochemical reactions.
• each enzyme is specific for the substrate it acts on.
• catabolic enzymes → enzymes that break down their substrates

• chemical-signaling molecules, usually small proteins or steroids
• secreted by endocrine cells to regulate specific physiological processes like growth, development, metabolism, and reproduction.
• Check Table 3.1 in the book for functions.

• monomers that form proteins.
• fundamental structure → central carbon, bonded to an amino group (NH2), a carboxyl group (COOH), and a hydrogen atom.
• there are 20 amino acids in proteins.
• amino acids attach to each other using a covalent bond called a peptide bond.

• primary structure → unique sequence of amino acids.
• secondary structure → the local folding of the polypeptide in some regions.
• a-helix → spiral-like structure
• b-pleated sheet → looks like a folded paper
• tertiary structure → three-dimensional structure of a polypeptide
• quaternary structure → the interaction of several polypeptides

Nucleic Acids

They carry the genetic blueprint of a cell and carry instructions for the functioning of the cell. Two main types of nucleic acids DNA → deoxyribonucleic acid RNA → ribonucleic acid

RNA

DNA

• is the genetic material found in all living organisms
• found in the nucleus of eukaryotes and in organelles, chloroplasts, and mitochondria. In prokaryotes, DNA is not enclosed in a membranous envelope.
• genome → the entire genetic content of a cell
• double-helix structure. the outside is sugar and phosphate, and the lines in between are nitrogenous bases.
• DNA dictates the structure of mRNA in transcription.

• mainly involved in the process of protein synthesis. it is single-stranded.
• RNA indicates the structure of the protein in translation.
• four major types of RNA
• messenger RNA (mRNA) → given that DNA doesn’t leave the nucleus, mRNA serves as a messenger to communicate with the rest of the cell.
• ribosomal RNA (rRNA) → a major constituent of ribosomes on which mRNA binds. it is responsible for the proper alignment of ribosomes and mRNA.
• transfer RNA (tRNA) → it carries amino acids to the site of protein synthesis.
• microRNA (miRNA) → regulates gene expression by interfering with the expression of certain mRNA messages.

3.1 Synthesis of Biological Macromolecules

• Biological macromolecules: large molecules necessary for life. Built from smaller organic molecules
• Classified into four classes
• carbohydrates
• lipids
• proteins
• nucleic acids
• Macromolecules are the majority of a cell’s dry mass
• Composed of carbon, it might contain hydrogen, oxygen, nitrogen, and other minor elements.
• Macromolecules are made from subunits (building blocks) called monomers.
• Polymers: a chain of repeating monomers
• Dehydration synthesis: when monomers come together to build macromolecules and lose water in the process.
• Hydrolysis: polymers are broken down into monomers.
• Hydrolysis reactions are catalyzed (sped up) by specific enzymes.
• carbohydrates are catalyzed by amylase, sucrase, lactase, or maltase
• proteins are catalyzed by pepsin and peptidase, and hydrochloric acid
• lipids are catalyzed by lipases