Biology 111 - Chapter 3 - FTCC

Organic molecules

Molecules that contain both carbon and hydrogen atoms.

Biomolecules

Four classes of organic molecules in living organisms: carbohydrates, lipids, proteins, and nucleic acids.

Functional groups

Clusters of specific atoms bonded to the carbon skeleton that determine the chemical reactivity and polarity of organic molecules.

Hydroxyl group

A functional group that is polar and forms hydrogen bonds, present in sugars and some amino acids.

Carbonyl group

A functional group that is polar, present in sugars, and can be an aldehyde or ketone.

Carboxyl group

An acidic functional group present in fatty acids and amino acids.

Amino group

A polar and basic functional group that forms hydrogen bonds, present in amino acids.

Sulfhydryl group

A functional group that forms disulfide bonds and is present in some amino acids.

Phosphate group

A functional group present in nucleotides and phospholipids.

Carbon atom

An atom with six electrons, capable of forming four covalent bonds.

C—C bond

A very stable bond between carbon atoms.

Carbon skeleton

The carbon chain of an organic molecule, also known as its backbone.

Isomers

Organic molecules that have identical molecular formulas but different arrangements of atoms.

Monomer

A repeating unit that makes up a polymer.

Polymer

A molecule composed of many repeating units (monomers).

Dehydration reaction

A chemical reaction in which subunits are joined together by the formation of a covalent bond and water is produced.

Hydrolysis reaction

A chemical reaction in which a water molecule is added to break a covalent bond.

Carbohydrates

Biomolecules that consist of monosaccharides as subunits and form polysaccharides.

Lipids

Biomolecules composed of glycerol and fatty acids that do not form polymers.

Proteins

Biomolecules made of amino acids as subunits, forming polypeptides.

Nucleic acids

Biomolecules composed of nucleotides as subunits, forming DNA and RNA.

Starch

A polymer formed from glucose subunits through dehydration reactions.

Digestion of starch

A hydrolysis reaction that breaks down starch into glucose monomers.

Ethane

A 2-carbon hydrocarbon that can be converted to ethanol by replacing an H with -OH.

Ethanol

A hydrophilic molecule formed from ethane by the addition of a hydroxyl group.

Enzymes

Special molecules required for cells to carry out dehydration synthesis and hydrolysis reactions; they speed up chemical reactions.

Catalysts

Substances that increase the rate of a chemical reaction without being consumed or changed by the reaction.

Monosaccharides

Single sugar molecules with a backbone of 3 to 7 carbon atoms, also known as simple sugars.

Hexoses

Monosaccharides that contain six carbon atoms.

Pentoses

Monosaccharides that contain five carbon atoms.

Disaccharides

Carbohydrates formed by joining two monosaccharides during a dehydration reaction.

Lactose

A disaccharide composed of galactose and glucose, known as milk sugar.

Sucrose

A disaccharide composed of glucose and fructose, commonly known as table sugar.

Maltose

A disaccharide composed of two glucose molecules.

Lactase

An enzyme that breaks down lactose into galactose and glucose.

Polysaccharides

Polymers of monosaccharides that serve as energy-storage and structural molecules.

Glycogen

A polysaccharide that provides energy storage in animals.

Cellulose

A polysaccharide found in the cell walls of plants, the most abundant organic molecule on Earth.

Chitin

A polysaccharide found in the cell walls of fungi and in the exoskeleton of some animals.

Peptidoglycan

A polymer found in the cell walls of bacteria.

Fats

Lipids that provide long-term energy storage and insulation in animals.

Oils

Lipids that provide long-term energy storage in plants and their seeds.

Phospholipids

Lipids that are a component of plasma membranes.

Steroids

Lipids that serve as components of plasma membranes and include sex hormones.

Waxes

Lipids that provide protection and prevent water loss, found in plant surfaces and as beeswax.

Triglycerides

Lipids also known as fats and oils, consisting of one glycerol molecule linked to three fatty acids.

Unsaturated Fatty Acids

Fatty acids with one or more double bonds between carbons, typically liquid at room temperature.

Saturated Fatty Acids

Fatty acids with no double bonds between carbons, typically solid at room temperature.

Trans Fatty Acids

Triglycerides with at least one bond in a trans configuration.

Phospholipid Structure

Consists of one glycerol molecule linked to two fatty acids and a modified phosphate group.

Fatty acids

The fatty acids (tails) are nonpolar and hydrophobic.

Modified phosphate group

The modified phosphate group (head) is polar and hydrophilic.

Function of phospholipids

Form plasma membranes of cells.

Phospholipid bilayer

In water, phospholipids aggregate to form a phospholipid bilayer (double layer).

Orientation of phosphate heads

Polar phosphate heads are oriented towards the water.

Orientation of fatty acid tails

Nonpolar fatty acid tails are oriented away from water.

Hydrophobic core

Nonpolar fatty acid tails form a hydrophobic core.

Kinks in tails

Kinks in the tails keep the plasma membrane fluid across a range of temperatures.

Functional groups in steroids

Various functional groups attached to the carbon skeleton.

Function of steroids

Component of animal cell membrane, regulation.

Examples of steroids

Cholesterol, testosterone, estrogen.

Difference between testosterone and estrogen

Testosterone and estrogen are sex hormones differing only in the functional groups attached to the same carbon skeleton.

Cholesterol as a precursor

Cholesterol is the precursor molecule for several other steroids.

Cholesterol and cardiovascular disorders

Cholesterol can also contribute to cardiovascular disorders.

Properties of waxes

Solid at room temperature, waterproof, resistant to degradation.

Function of waxes

Protection.

Examples of waxes

Earwax (contains cerumen), plant cuticle, beeswax.

Peptide bond

A peptide bond is a covalent bond between amino acids.

Protein composition in cells

As much as 50% of the dry weight of most cells consists of proteins.

Peptides

Two or more amino acids joined together are called peptides.

Polypeptides

Long chains of amino acids joined together are called polypeptides.

Function of proteins

A protein is a polypeptide that has folded into a particular shape, which is essential for its proper functioning.

Denatured proteins

When a protein loses its proper shape, it is said to be denatured.

Causes of denaturation

Exposure of proteins to certain chemicals, a change in pH, or high temperature can disrupt protein structure.

Levels of protein structure

Proteins can have up to four levels of structure: Primary, Secondary, Tertiary, Quaternary.

Primary structure

Primary structure is the linear sequence of amino acids.

Secondary structure

Secondary structure is characterized by the presence of alpha helices and beta (pleated) sheets held in place with hydrogen bonds.

Tertiary structure

Tertiary structure is the overall three-dimensional shape of a polypeptide.

Stabilization of tertiary structure

It is stabilized by the presence of hydrophobic interactions, hydrogen, ionic, and covalent bonding.

Quaternary structure

Consists of more than one polypeptide.

Chaperone proteins

Help proteins fold into their normal shapes and may also correct misfolding of new proteins.

Prions

Misfolded proteins that have been implicated in a group of fatal brain diseases known as TSEs.

TSEs

A group of fatal brain diseases associated with prions.

Mad cow disease

An example of a TSE.

DNA (deoxyribonucleic acid)

Genetic material that stores information for its own replication and for the sequence of amino acids in proteins.

RNA (ribonucleic acid)

Performs a wide range of functions within cells which include protein synthesis and regulation of gene expression.

Nucleotide

Composed of three parts: a phosphate, a pentose sugar, and a nitrogen-containing (nitrogenous) base.

Types of nucleotides in DNA

Contains adenine, guanine, cytosine, and thymine.

Types of nucleotides in RNA

Contains adenine, guanine, cytosine, and uracil.

Dehydration synthesis reactions

Join nucleotides together to form a linear molecule called a strand.

Backbone of nucleic acid strand

Composed of alternating sugar-phosphate molecules.

RNA structure

Predominately a single-stranded molecule.

DNA structure

A double-stranded molecule composed of two strands held together by hydrogen bonds between the nitrogen-containing bases.

Complementary base pairing

Adenine (purine) makes hydrogen bonds with thymine (pyrimidine), and cytosine (pyrimidine) makes hydrogen bonds with guanine (purine).

Number of purines and pyrimidines

The number of A + G (purines) always equals the number of T + C (pyrimidines).

Comparing DNA and RNA: Sugar

DNA contains deoxyribose, while RNA contains ribose.

Comparing DNA and RNA: Bases

DNA contains adenine, guanine, thymine, and cytosine; RNA contains adenine, guanine, uracil, and cytosine.

ATP (Adenosine Triphosphate)

A nucleotide composed of adenine and ribose (adenosine) and three phosphates.

High-energy molecule

ATP is high-energy due to the presence of the last two unstable phosphate bonds, which are easily broken.

Hydrolysis of ATP

Yields ADP (adenosine diphosphate), an inorganic phosphate, and energy to do cellular work.