3- Biological Molecules
Importance of Carbon
Molecules containing Carbon are organic molecules
● Carbon has 4 valence electrons- chemical bonding form covalent bonds with up to four
different atoms serves as the “backbone” for the macromolecules
Carbon- Covalent Bonds
● Each carbon has four electrons in the outer shell
● It forms four covalent bonds to “fill” the outer shell
● This allows it to achieve the “octet rule”
Hydrogen + Carbon= Hydrocarbon
● Energy is released from hydrocarbons when they combust.
● release many biproducts (CO2, CH4, etc.)
● release particulate matter
● Build up of ozone
Carbon can form five-and six membered rings (closed chain)
● Single or double bonds may connect the carbons in the ring
● Nitrogen may be substituted for carbon
Isomers- same chemical formula, different structure
Organic molecules – all contain carbon
● May also contain hydrogen, oxygen, nitrogen, and some other minor elements
Monomer- one unit/ subunit of a molecule
● Mono= one
Polymer- a chain of units/ subunits linked together
● Poly = many
Synthesis- to make
When simple biological molecules join to form complex molecules they do this through a process called
dehydration synthesis.
● In your notes, using this model develop a definition for dehydration synthesis
Hydrolysis
Hydro= water
Lysis= to cut
Hydrolysis – process of breaking polymers down into individual monomers
Hydrolysis shown here - disaccharide maltose is broken down to form two glucose monomers
Enzymes- biological catalysts
proteins
● speed up chemical reactions
● do not take part in chemical reactions (no electron exchange)
Examples:
Carbohydrates – broken down by amylase, sucrase, lactase, maltase
Lipids – broken down by lipases
Proteins – broken down by pepsin and peptidase
Enzymes names end in “ase”
Biological Molecules
Carbohydrates
Monomer: Simple sugars
● Glucose
● Galactose
● Fructose
○ found in grains, fruits, and vegetables
○ Provide energy to body in from of glucose
○ Represented by the general formula (CH₂O)
○ Ratio of Carbon:Hydrogen:Oxygen is 1:2:1
Three main subtypes:
● Monosaccharides
● Disaccharides
● Polysaccharides
Monosaccharides usually have 3-7 carbons
● End with the suffix –ose
● Contain a carbonyl group C=O
● Aldoses - carbonyl group (indicated in green) at the end of the carbon chain
● Ketoses - carbonyl group in the middle of the carbon chain
● Trioses – three carbons
● Pentoses – five carbons
● Hexoses – six carbons
Structural isomers/ formula (C₆H₁₂O₆)
● Glucose – important source of energy
● Galactose – part of lactose/ milk sugar
● Fructose - part of sucrose/ fruit
Monosaccharides exist as linear chain or ring-shaped molecules.
● Assume ring structure in aqueous solutions
● Five- and six-carbon monosaccharides exist in equilibrium between linear and ring forms
● Fructose and ribose also form rings
● they form five-membered rings as opposed to the six-membered ring of glucose
● Linear structure becomes ring due to a hydrogen bond
Disaccharides form when two monosaccharides are linked in a dehydration reaction
● Example of disaccharide formation
● Glucose + Fructose = Sucrose (disaccharide)
● Two monomers are joined by glycosidic bond
● Water is also released
● carbon atoms in a monosaccharide are numbered from the terminal carbon closest to the
carbonyl group
Cellulose- Makes cell walls of plants
● Provides structural integrity to plants
● Each layer of polysaccharides align flipped relative to the next one making a fibrous
structure.
Chitin is a polysaccharide, but note, it also contains nitrogen
Lipids
Lipids are a diverse group of non-polar hydrocarbons
Non-polar hydrocarbons are hydrophobic (water-fearing)
Lipid bi-layer in plasma membranes
● Hydrophilic heads: water loving, oriented towards interstitial fluid
● Hydrophobic tails: water fearing, oriented towards each other.
Functions of lipids
● Long-term energy stores
● Provide insulation from environment for plants and animals
● Serve as building blocks for some hormones
● Important component of cellular membranes
Types of lipids
● Fats
● Oils
● Waxes
● Phospholipids
● Steroids
● Fats – Contain two main components
● Glycerol
● Fatty Acids
● Triacylglycerol – formed by joining three fatty acids to a glycerol backbone
The glycerol molecules are attached to the fatty acids via an ester linkage (dehydration)
Three molecules of water are released in this reaction
Saturated Fat: Saturated with hydrogen
Stearic acid is a common saturated fatty acid .
This means it contains no carbon-carbon double bonds in the carbon-backbone
Pack tightly and exist as solids at room temperature (butter, fat in meats, etc)
May be associated with cardiovascular disease – should be limited in your diet
Unsaturated Fats: easier for the body to break down and store as energy
Oleic acid is a common unsaturated fatty acid
● Contains at least one carbon-carbon double bond in carbon chain backbone
Monounsaturated fat = one double bond
Polyunsaturated fat = more than one double bond
● Most unsaturated fats are liquids at room temperature – referred to as oils
● Each double bond of an unsaturated fat may be in one of two positions
Cis configuration – hydrogens on same side of chain
Trans configuration – hydrogens on opposite side of chain
Cis-acids have a kink in the chain
● They cannot be packed tightly
● Liquid at room temperature
Trans-acids – no kink
● Can pack tightly together
● Can be created through processing
● Foods with trans fat may increase LDL cholesterol in humans (bad for heart)
Essential fatty acids – required but not synthesized by the body – must be part of diet
● Omega-3 fatty acid (found in salmon, trout, tuna)
● Omega 6-fatty acid
These fats are heart healthy
● Reduce risk of heart attack, reduce triglycerides in blood, lower blood pressure
● Long fatty acid chains esterified to long chain alcohols
● Hydrophobic and prevent water from sticking to surface
● Found on the feathers of some aquatic birds and on the surface of leaves from certain plants
Phospholipids
Phospholipid - molecule with two fatty acids and a modified phosphate group attached to a glycerol
backbone
● The phosphate may be modified by the addition of charged or polar chemical groups
● Two common chemical groups that attach to phosphate are choline and serine
Plasma Membrane
Key Properties
● Fluid and Flexible
● can self repair
● Can hold proteins (protein channels)
● Are semipermeable
Steroids
● Steroids have a closed-ring structure
● Four linked carbon rings
● Many have a short tail
Structure is different from that of other lipids
● They are hydrophobic
● They are insoluble in water
● Cholesterol is the most common steroid
● Synthesized in liver
Precursor to
● Other hormones such as testosterone and estradiol
● Vitamin D
● Bile salts
Proteins
● Most abundant organic molecules
● Have a diverse range of functions
● Regulatory functions
● Structural functions
● Protective functions
● Transport
● Enzymes
● Toxins
Enzymes – catalysts in biochemical reactions
● Specific enzyme for specific substrate
● Types of enzymes
Catabolic – breakdown substrates
Anabolic – build more complex molecules
Catalytic – affect the rate of reaction
Amino acids are the monomers that make up proteins
● Fundamental structure (Draw and label)
● Central carbon atom (α-carbon)
● Amino group (-NH₂)
● Carboxyl group (-COOH)
● Hydrogen
● Side chain (R-group)
20 common amino acids commonly found in proteins
Each amino acid has a different R group (variant group) determine the chemical nature of each amino
acid
● Nonpolar aliphatic
● Polar
● Positively charged
● Negatively charged
● Nonpolar aromatic
Amino acids are represented by a single uppercase letter or three letters
● Valine = V or Val
● Aspartic Acid = D or Asp
Essential Amino acids – the following must be supplied in diet for humans
● isoleucine
● leucine
● cysteine
Polypeptide – a chain of amino acids joined together in peptide linkages
Protein – a polypeptide or multiple polypeptides
● Often combined with non-peptide prosthetic groups
● Has a unique structure and function
● Many proteins are modified following translation (process of creating a new protein)
Primary structure – the unique sequence of amino acids in a polypeptide
● Amino acid sequence is based upon gene encoding that protein
●
● A change in the nucleotide sequence of DNA could lead to a change in amino acid
●
● This could lead to a change in protein structure and function
Tertiary structure – the unique three dimensional structure of a polypeptide
Tertiary structure of proteins is determined by a variety of chemical interactions
● hydrophobic interactions
● ionic bonding
● hydrogen bonding
● disulfide linkages
Quaternary Structure – interactions between several polypeptides that make up a protein
● Weak interactions between subunits help stabilize the structure
Proteins: Denaturing
● Protein structure and shape can be changed if chemical interactions are broken
● Protein structure/shape can change with altering primary structure due to:
● Changes in pH
● Changes in temperature
Denaturation – Changes in protein structure that leads to changes in function
Nucleic Acids
Nucleic acids – constitute the genetic material of living organisms
Two types of nucleic acid
● deoxyribonucleic acid (DNA)
● Double Stranded
● Adenine, Cytosine, Guanine, and Thymine
● Deoxyribose Sugar
ribonucleic acid (RNA)
● Single Stranded (usually)
● Adenine, Cytosine, Guanine, and Uracil
● Ribose Sugar
Location of Nucleic Acid
● Nucleus of eukaryotic cells
○ Eu= True
○ Karyote= nucleus
● Cytoplasm of Prokaryotic Cells
○ Pro= Before
○ Karyote= nucleus
● Mitochondria
● Chloroplasts
