A&P Lab: Chemical Digestion Lab

Macromolecules

• large molecules composed of thousands of covalently connected atoms

Polymer

• a long molecule consisting of many similar building blocks

• carbohydrates, proteins, nucleic acids

Monomers

• small building-block molecules

• lipids

Dehydration reaction

Two monomers bond together through the loss of a water molecule

Hydrolysis

• adds a water molecule, breaking a bond

• polymers are disassembled to monomers

• reverse of dehydration reaction

Dehydration

removes a water molecule, forming a new bond to create a polymer

Carbohydrates

• sugars and polymers of sugars

• monosaccharides

• macromolecules: polysaccharides (polymers)

Monosaccharides

• simplest carbohydrates, simple sugars

• molecular formula: multiples of CH2O

• most common: glucose (C6H12O6)

Polysaccharides

• polymers of sugars, storage and structural roles

• structure and function determined by sugar monomers and position of glycosidic linkages

Lipids

• do not form polymers

• hydrophobic, consists of hydrocarbons (nonpolar covalent bonds)

• fats, phospholipids, and steroids

Fats

• constructed from glycerol (1) and fatty acids (3)

• creates a triacylglycerol or triglyceride

Fatty acids

• carboxyl group (COOH) attached to long carbon skeleton

• 3 fatty acids join with 1 glycerol to create a triacylglycerol or triglyceride

Proteins

• consists of one or more peptides

• polypeptides

• amino acids

Polypeptides

• polymers built from a set of 20 monomers called amino acids

• each has a unique linear sequence of amino acids, its primary structure

Amino acids

• organic molecules with carboxyl and amino groups

• differ in properties due to differing side chains, R groups

• linked by peptide bonds

Protein shape and function

• primary structure

• secondary structure

• tertiary structure

• quaternary structure

Primary structure of protein

sequence of amino acids

Secondary structure

• hydrogen bonds between amine and carboxylic acids groups of backbone

• alpha-helix and beta-sheets

Tertiary structure

• interactions between R-groups

• ionic, dipole-dipole, hydrogen bonds, van der Waals, disulfide

Quaternary structure

interactions between polypeptide subunits

Factors that influence protein activity

• temperature, salt concentration, pH changes

• may disrupt protein structure and cause loss of function

Nucleic acids

• polymers called polynucleotides, made up of nucleotides (monomers)

• nucleotide

• nucleoside

• sugars are either ribose (RNA) or deoxyribose (DNA)

Nucleotides

• consists of nitrogenous base, a pentose sugar, and a phosphate group

• monomer of polynucleotide

• portion without the phosphate group is called nucleoside

Nucleoside

portion of nucleotide without the phosphate group

Enzymes

• large protein molecules (catalysts)

• digestive enzymes (hydrolases)

Catalysts

speed up reactions but are unaffected themselves

Hydrolases

• digestive enzyme

• break intermolecular bonds by adding water

Substrate

molecules in which a particular enzyme acts

Production of enzymes

• salivary glands (amylase)

• stomach glands (pepsin)

• pancreas (pancreatin, proteases, lipases, ribo/deoxyribonucleases)

• microvilli of small intestine (brush border enzymes)

Salivary glands

amylase—carbohydrates

Stomach glands

pepsin--protein

Pancreas

• pancreatin--amylase

• proteases, lipases, ribo/deoxyribonucleases--carbs, protein, fat, nucleic acids

Microvilli of small intestines

brush-border enzymes--last stages of carbs, proteins, nucleic acids

Lactase

enzyme that breaks up the disaccharide lactose (milk sugar)

Pepsin

• in the stomach, at acidic pH

• in small intestines, degraded and reabsorbed

Trypsin

in the intestines, at more neutral pH

Bile salts

• derived from cholesterol

• made in liver, stored in gallbladder

• delivered to duodenum when fatty meal arrives

• hydrophobic and hydrophilic ends prevents fat droplets from joining: emulsification

Emulsification

hydrophobic (polar) and hydrophilic (non-polar) ends stick to fat and water, preventing fat droplets from forming larger droplets

Lipase

acts on the lipids

Deglutition

• swallowing

• buccal (voluntary)

• pharyngeal-esophageal (involuntary)

Peristalsis

waves of contraction followed by relaxation

Segmentation

local contraction followed by relaxation designed to mix chyme with digestive enzymes for digestion and spread chyme over intestinal walls for absorption