Chapter 2: The Chemistry of Life

Merged flashcards from Chapter 2, McGraw Hill Anatomy and Physiology Ninth Edition, by Kenneth S. Saladin.

Organic chemistry

The study of compounds containing carbon

Carbon molecule categories

Carbohydrates, lipids, proteins, and nucleic acids

Properties of carbon

Has four valence electrons to bind with each other and other atoms, can make groups with a carbon backbone

Macromolecules

Large organic molecules with high molecular weights

Polymers

Macromolecules made of a series of identical subunits called monomers (e.g. starch → 3000 glucose monomers)

Polymerization

Joining monomers to form a polymer

Dehydration synthesis

Covalently binding monomers to form a polymer; where OH and H groups are removed to make water as a byproduct

Hydrolysis

Splitting polymers into monomers with water; where OH and H groups are added to monomers that are broken through enzymes

Carbohydrates

Hydrophilic, organic molecules like sugars and starches that are converted to glucose and oxidized to make ATP; with a formula of (CH₂O)_n where n = number of carbon atoms

Monosaccharides

The simplest carbohydrates, they are monomers

Glucose, galactose, and fructose

The three important monosaccharides that are produced by digesting more complex carbohydrates; they are all isomers of each other with the formula C₆H₁₂O₆

Disaccharides

Sugars made up of two covalently bonded monosaccharides

Sucrose (table sugar)

A disaccharide made up of glucose and fructose

Lactose (milk sugar)

A disaccharide made up of glucose and galactose

Maltose (sugar in grain)

A disaccharide made up of glucose and glucose together

Oligosaccharides

Short chains of three or more monosaccharides (at least 10); ____saccharides → a few

Polysaccharides

Long chains of monosaccharides (at least 50); ____saccharides → many

Glycogen

A polysaccharide that stores dense energy in the liver, muscles, and brain

Starch

Energy storage in plants that is digestable by humans

Cellulose

Structural molecule in plants that is important for dietary fiber but indigestible to us

Glycolipids and glycoproteins

Carbohydrates that are conjugated with lipids or proteins, where chains of sugars attach to these molecules

Proteoglycans

Gels that hold cells and tissues together and fill the umbilical cord and eye, and lubricates joints

More carbohydrate than protein

Lipids

Hydrophobic, organic molecules with a high ratio of hydrogen to oxygen - more calories per gram than carbohydrates

Fatty acids

Chains of 4-24 carbon atoms with a carboxyl and methyl group on the ends; they are obtained from food

Saturated fatty acids

Fatty acids with carbon atoms linked by single covalent bonds; “saturated” with as much hydrogen as possible

Unsaturated fatty acids

Carbon atoms linked by some double covalent bonds, has potential to add hydrogen

Polyunsaturated fatty acids

An unsaturated fatty acid with multiple double bonds between carbons

Triglycerides

Fatty acids linked to glycerol which store energy and help shock absorption

Trans-fatty acids

Fatty acids with two covalent C - C bonds in opposites on each side of the C = C double bond; they resist enzymatic breakdown in the body and deposit in the arteries

Cis-fatty acids

Fatty acids with two covalent C - C bonds in the same direction adjacent to the C = C double bond

Phospholipids

Similar to neutral fats, but one fatty acid is replaced by a phosphate group - the tails are hydrophobic, while the phosphate head is hydrophilic; making them good for cell membranes

Eicosanoids

20-carbon compounds derived from arachidonic acids; they send hormone-like signals between cells and include prostaglandins which plays an important role in inflammation

Steroids

Type of lipid with 17 carbon atoms in four rings

Cholesterol

The “parent” steroid from which other steroids are synthesized, they are important for nervous system function and cell membranes

High-density lipoproteins (HDLs)

“Good cholesterol,” has a lower ratio of lipid to protein and may prevent cardiovascular disease

Low-density lipoproteins (LDLs)

“Bad cholesterol,” has a lower ratio of protein to lipids and contributes to cardiovascular disease

Proteins

Polymers of amino acids, they are peptides with more than 50 amino acids

Amino acids

A carbon with amino (-NH₂), carboxyl (-COOH), and radical (R) attachments; the R group determines the properties of this

Peptide

Two or more amino acids joined by peptide bonds

Peptide bonds

Joins the amino and carboxyl groups of two amino acids through dehydration synthesis

Dipeptides

A peptide with 2 amino acids

Tripeptides

A peptide with 3 amino acids

Oligopeptides

A peptide with between 3 and 15 amino acids

Polypeptides

A peptide with between 15 and 50 amino acids

Conformation

A unique, three dimensional shape of protein crucial to function; these are reversible to affect change

Denaturation

Extreme conformational change that destroys function; extreme heat or pH can cause permanent this

Primary structure

Structure comprised of a sequence of amino acids within a protein molecule; it is encoded by genes

Secondary structure

Coiled or folded shape held together by slight hydrogen bonds between C = O and N - H

Tertiary structure

A structure made by further bending and folding of proteins into globular and fibrous shapes due to hydrophobic-hydrophilic interactions and van der Waals forces

Globular proteins

Proteins in a compact tertiary structure within the cell membrane and can move freely in body fluids

Fibrous proteins

Slender filaments suited for roles in muscle contraction and strengthening of skin and hair

Quaternary structure

Structures comprised of two or more polypeptide chains due to ionic bonds and hydrophobic-hydrophilic interactions

Keratin

Tough structural protein of hair, nails, and skin surface

Collagen

Contained in deeper layers of skin, bones, cartilage, and teeth

Membrane transport

Diffusion of hydrophilic substances across cell membranes through protein channels

Enzymes

Proteins that function as biological catalysts to lower overall activation energy

They are named for the substrate with -ase as the suffix (e.g. lactase catalyzes the hydrolysis of lactose)

Substrate

The substance an enzyme acts upon

Steps to enzyme action

1. The substrate binds to the active site

2. The molecules form an enzyme-substrate complex

3. The enzyme releases reaction products

4. The enzyme repeats the process, as it is reusable

Optimal enzyme factors

Temperatures and pH (e.g. stomach vs salivary enzymes)

Cofactors

Non-protein “helper” molecules which are necessary for enzymatic functioning; includes minerals like iron, copper, zinc, and calcium

Coenzyme

Organic cofactors derived from vitamins (e.g. NAD⁺ which is derived from niacin and aids metabolism)

Metabolic pathway

The chain in which a reactant is modified by different enzymes to get an end product; the enzymes for each step are represented by Greek letters

Nucleotides

Organic compounds with a nitrogenous base, sugar, and a phosphate group; examples include ATP and cAMP

Adenosine triphosphate (ATP)

The body’s most important energy-transfer molecule; holds energy in covalent bonds between phosphates

Nucleic acids

Polymers of nucleotides; includes DNA for protein synthesis and RNA for genetic instructions

Energy

The capacity to do work; all body activities are work

Potential energy

Energy stored in an object but not currently doing work (e.g. water behind a dam)

Chemical energy

Potential energy in molecular bonds

Free energy

Potential energy available in a system to do useful work

Kinetic energy

The energy of motion which is doing work (e.g. water flowing through a dam)

Heat

The kinetic energy of molecular motion

Electromagnetic energy

The kinetic energy of moving packets of radiation called photons

Chemical reaction

Process in which a covalent or ionic bond is formed or broken

Chemical equation

Symbolizes the course of a chemical reaction; reactions on the left → products on the right

Decomposition reactions

Large molecule breaks down into two or more smaller ones; AB → A + B

Synthesis reactions

Two or more smaller molecules combine to form a larger one; A + B → AB

Exchange reactions

Two molecules exchange atoms or a group of atoms; AB + CD → ABCD → AC + BD

Reversible reactions

Reactions that can reverse under different circumstances; symbolized with a double-headed arrow

Law of mass action

Direction of reaction determined by relative abundance (quantity) of either side of equation

Increasing reaction rate causes

Rising temperature, concentrated reactants, catalysts like enzymes to lower the reaction energy

Metabolism

All chemical reactions of the body

Catabolism

Energy releasing (exergonic) decomposition reactions that break covalent bonds and produce smaller molecules

Anabolic reactions

Energy storing (endergonic) synthesis reactions that require energy input (e.g. production of fat)

Oxidation

A chemical reaction in which a molecule gives up electrons and releases energy

Reduction

Any chemical reaction in which a molecule gains electrons or energy

Oxidizing agent or reduced molecule

The molecule that accepts the electrons; oxygen is often the acceptor

Reducing agent or oxidized molecule

The molecule that donates electrons

Oxidation-reduction (redox) reactions

Oxidation of one molecule (giving away electrons) is always accompanied by reduction of another (gaining electrons); electrons are transferred as hydrogen atoms

Mixtures

Substances that are physically blended but not chemically combined; most are body fluids with water

Properties of water

Solvency, cohesion, adhesion, reactivity, thermal stability

Solvency

The ability to dissolve other chemicals; water is the universal this

Hydrophilic substances

Substances that dissolve in water; molecules that are this are polarized or charged (like sugar)

Hydrophobic

Substances that do not dissolve in water; molecules that are this are nonpolar or neutral (like fats)

Hydration spheres

Ionic bonds being overpowered by hydrogen bonds from water

Adhesion

The tendency of one substance to cling to another; water does this in membranes

Cohesion

The tendency of like molecules to cling to each other; water does this due to its hydrogen bonds and makes surface tension

Chemical reactivity

The ability to participate in chemical reactions; water does this into H⁺ and OH^-

Heat capacity

The amount of heat needed to raise the temperature of 1 gram of a substance by 1 degree C

Calorie

The base unit of heat that raises the temperature of 1 gram of water by 1 degree C

Thermal stability

The ability to stabilize the temperature of its surroundings; water can absorb high levels of heat and remove calories