Digestion and Human Health - Notes
Food
- Food provides both matter and energy to the body.
- The body transforms food into matter and energy.
6.1 – The Molecules of Living Systems
- This section covers:
- The chemical nature of carbohydrates, lipids, proteins, and nucleic acids.
- How carbohydrates, lipids, and proteins are synthesized and broken down.
- Tests to identify macromolecules.
Macromolecules
- Macromolecules are large, complex organic molecules.
- Organic molecules contain carbon bonded to hydrogen and other atoms like oxygen, sulfur, and nitrogen.
Four Classes of Macromolecules
- The four classes of macromolecules are:
- Carbohydrates
- Lipids
- Proteins
- Nucleic acids
Macromolecules as Polymers
- Macromolecules are polymers.
- Polymers are long molecules formed by linking many small, similar subunits (monomers) together.
- Example: linking railroad cars to form a train (A-A-A-A-A-A-A-A-A-A-).
Assembling & Disassembling Molecules
- The body builds complex macromolecules from monomers (smaller similar subunits) through assembling.
- The body breaks down macromolecules into monomers through disassembling.
- Dehydration Synthesis and Hydrolysis Reactions are key processes.
Hydrolysis and Dehydration Synthesis
- Dehydration Synthesis: removes a water molecule to link monomers.
- Hydrolysis: adds a water molecule to break down polymers.
Key Terms Review
- Macromolecules: Large complex organic molecules.
- Organic Molecules: Contain carbon bonded to hydrogen and other atoms (O, S, N).
- Macromolecules are formed by dehydration synthesis, where a water molecule (H_2O) is removed to join monomers.
Dehydration Synthesis
- Dehydration synthesis is the synthesis of macromolecules, which removes water (H_2O).
Macromolecule Breakdown
- Macromolecules are broken down by hydrolysis, where water (H_2O) must be added.
Hydrolysis Reaction
- Hydrolysis is a reaction where macromolecules are broken down by adding water (H_2O).
Assembling & Disassembling Molecules
- Dehydration Synthesis: synthesis of macromolecules.
- Hydrolysis Reaction: macromolecules are broken down.
Carbohydrates
- Composed of carbon, hydrogen, and oxygen, in a 1:2:1 ratio (CH_2O).
Types of Carbohydrates
- Three types of carbohydrates (saccharides):
- Monosaccharide: 1 sugar unit.
- Disaccharide: 2 sugar units.
- Polysaccharide: many (>2) sugar units.
Classification of Carbohydrates
- Simple Sugars: monosaccharides and disaccharides.
- Complex Carbohydrates: polysaccharides.
Monomers of Carbohydrates
- Monomers (building blocks) of all carbohydrates are monosaccharides (C6H{12}O_6).
- Most common:
- Glucose
- Fructose (fruit & plants)
- Galactose (milk)
- Disaccharides are formed when 2 monosaccharides are joined together through dehydration synthesis.
Examples of Disaccharides
- Examples of disaccharides:
- glucose + glucose = Maltose (malt sugar)
- glucose + fructose = Sucrose (table sugar)
- glucose + galactose = Lactose (milk sugar)
Production of a Disaccharide
- Two monosaccharides combine through dehydration synthesis by removing (H_2O) to form a disaccharide and then a polysaccharide.
How Plants Store Energy
- Plants store energy as polysaccharides, specifically starch (e.g., potatoes).
- Structural polysaccharides include cellulose, found in cell walls of plants.
- Humans lack the enzymes to digest cellulose.
How Animals Store Energy
- Animals store energy as polysaccharides, specifically glycogen, which is highly branched and stored in the liver.
Structural Differences
- Starch, glycogen, and cellulose are all polysaccharides consisting of glucose subunits, but they have different structures.
Lipids
- Diverse group of macromolecules that are all insoluble in water.
- Provide 2.25 times more energy per gram than other biological molecules.
Functions of Lipids
- Functions:
- Fats & oils: long-term energy storage molecules.
- Phospholipids: components of cell membranes.
- Steroids: sex hormones like estrogen & testosterone.
Subunits of Lipids
- Subunits:
- 1 glycerol molecule (a 3-carbon chain).
- 3 fatty acids (composition may vary).
- Triglyceride = fat.
Saturated vs. Unsaturated Fats
- Saturated: C-C single bonds, saturated with hydrogen, solid at room temperature, animal-derived, associated with cardiovascular diseases.
- Unsaturated: C=C double bonds, not saturated with hydrogen, liquid at room temperature, plant-derived, healthier choice.
Key Differences Between Saturated and Unsaturated Fats
- Saturated Fats:
- C-C single bonds only.
- Saturated with H – bonded to the maximum # of H atoms
- Fat is solid at RT
- Animal
- Associated with cardiovascular diseases
- Unsaturated Fats
- C=C double bonds.
- Not saturated with H – not bonded to the maximum # of H atoms
- Fat is liquid at RT
- Plant
- Healthier choice
Proteins
- Greatest structural complexity & functional diversity; makes up most cellular structures.
Functions of Proteins
- Functions:
- Transport – hemoglobin (O_2 carrying molecule in blood).
- Blood clotting – fibrin.
- Support – collagen.
- Immunity – antibodies.
- Catalysis – enzymes.
- Muscle action – actin & myosin.
- Chemical messengers – some hormones.
Subunits of Proteins
- Subunits (monomers): amino acids.
Amino Acid Structure
- Amino Acid Structure includes:
- Amino Group
- Carboxylic Acid Group
- R Group (Side Chain)
- \alpha- carbon
- Chemical formula of Amino Acid:
Unique Group in Amino Acids
- The R-group is unique to each amino acid.
- There are 20 a.a.’s - The body makes 11, other 9 = essential a.a.’s must obtain from diet.
- Amino acids are bonded together in long chains to form proteins by dehydration synthesis.
- The bond between amino acids is called a peptide bond.
Protein Structure
- Attraction and repulsion between R-groups of amino acids causes twisting and turning of the strand.
- Quaternary Structure: 4 polypeptide chains
R Groups and Protein Structure
- Charged R groups attract water (outside of protein).
- E.g., enzymes, hemoglobin.
- Uncharged R groups repelled by water (inside of protein).
- E.g., keratin in fingernails.
Protein Functions
- Transport – hemoglobin
- Blood clotting – fibrin
- Support – collagen
- Immunity – antibodies
- Catalysis – enzymes
- Muscle action – actin & myosin
- Chemical messengers – some hormones
Structural and Functional Diversity of Proteins
- Why are proteins more structurally and functionally diverse than carbohydrates and lipids?
Reasons for Protein Diversity
- There are 20 different amino acid R-groups, which provide a large number of possible combinations, resulting in the vast variety of proteins.
- Also, the 3D structure of the protein is highly complex due to the attraction/repulsion of the different R-groups of the various amino acids in the protein.
- The final shape of a protein’s three-dimensional structure determines its properties, and therefore the functions, of the protein.
Nucleic Acids
- Function: contain the chemical code that directs growth and development.
- Determine how a cell functions and the characteristics it has.
- There are 2 types of nucleic acids
- 1. DNA – deoxyribonucleic acid Contains genes – information needed to build the cell
- 2. RNA – ribonucleic acid Involved in making a protein
Nucleotides
- Nucleic acids consist of long chains of linked subunits called nucleotides.
- These subunits contain phosphate, a sugar, and a nitrogen base.
Vitamins
- Organic compounds that often help enzymes function.
- Small amounts needed by the body for tissue development, growth, and resistance to disease.
- Vitamins are coenzymes – chemicals needed to make enzymes function.
Minerals
- Minerals are inorganic compounds.
- Small amounts needed by the body.
- Help some chemical reactions to happen.
- Help build bones/cartilage.
- Readily absorbed into the bloodstream.
- Essential parts of molecules such as hemoglobin, hormones, enzymes, and vitamins.
Benedict’s Reagent
- Tests for monosaccharides.
- Reagent is light blue; it changes color in the presence of monosaccharides & some disaccharides.
Iodine Test
- Iodine Test for the presence of starch (polysaccharide)
Biuret Reagent
- Tests for proteins.
- Binds to peptide bonds
- Blue ----> purple
Biuret’s Reagent
- Tests for the presence of polypeptides and proteins
- Light blue – no change (solution remains blue) - Proteins not present ( - )
- The solution turns from blue to violet (deep purple) - Proteins are present ( + )
- The solution turns from blue to pink - Peptides are present ( + ) (Peptides - short chains of amino acid residues)
Translucent Test
- Translucent test for fats (brown paper bag)
- (+) Translucent (grease spot)
- (-) nontranslucent (no grease spot)
