Bio Chapter 5 Study Guide

Polymer

A long molecule consisting of many similar or identical building blocks linked by covalent bonds (like how a train consists of a chain of cars).

Monomer

The repeating smaller molecules that serve as building blocks of a polymer. Some have functions of their own.

Dehydration synthesis (condensation reaction)

A reaction in which two molecules are covalently bonded to each other with the loss of a water molecule.

Each monomer contributes part of the water molecule released during the reaction. One provides a hydroxyl group (—OH) and the other provides a hydrogen (—H).

This is repeated as monomers are added to the chain one by one, creating a polymer.

Hydrolysis

The bond between monomers is broken by the addition of a water molecule.

Hydrogen from water attaches to one monomer, and hydroxyl group attaches to the other.

Polymers are disassembled to monomers.

Carbohydrate

Include sugars and polymers of sugars.

Provides short-term energy storage.

Monosaccharide

Simple sugars. The monomers from which more complex carbohydrates are built. Generally have molecular formulas that are a multiple of the unit CH₂O.

Disaccharide

Two monosaccharides joined by a glycosidic linkage.

Glycosidic bond

A covalent bond formed between two monosaccharides by a dehydration reaction.

Polysaccharide

Macromolecules, polymers with a few hundred to a few thousand monosaccharides, joined by glycosidic linkages.

α-glucose

The configuration where the hydroxyl group attached to the number 1 carbon is positioned below the plane of the ring.

β-glucose

The configuration where the hydroxyl group attached to the number 1 carbon is positioned above the plane of the ring. “Upside down” compared to its neighbors.

Starch

Plants store this. A polymer of glucose monomers as granules within cellular structures known as plastids (including chloroplasts). Can “bank” this to store energy, withdrawing it when needed through hydrolysis.

All the glucose monomers are in the α configuration. Certain molecules are largely helical.

Glycogen

A polysaccharide that animals store. A polymer of glucose that is extensively branched. Stored in liver and muscle cells. Hydrolysis of this releases glucose when demand for sugar increases.

Cellulose

A polysaccharide that is a major component of plant cell walls.

The glucose monomers are all in the β configuration. The molecule is straight, and is never branched.

Lipid

Does not include true polymers, and generally not big enough to be considered macromolecules. They mix poorly, if at all, with water. Consist mostly of hydrocarbon regions. Includes fats, steroids, and phospho______.

Fat

Large molecules constructed from glycerol and fatty acids through dehydration reactions. Hydrophobic.

To make one, three fatty acid molecules are each joined to glycerol by an ester linkage (a bond formed by a dehydration reaction between a hydroxyl and carboxyl group).

The main function is long-term energy storage.

Fatty acid

Has a long carbon skeleton (16-18 carbon atoms in length). The carbon at one end of the skeleton is part of a hydroxyl group (hence acid), and the rest of the skeleton is a hydrocarbon chain.

The nonpolar C—H bonds in the hydrocarbon chains are the reason fats are hydrophobic.

Glycerol

An alcohol (each of its three carbons bears a hydroxyl group) that constructs fats.

Saturated fatty acid

A fatty acid in which there are no double bonds between carbon atoms composing a chain, so as many hydrogen atoms as possible are bonded to the carbon skeleton.

Unsaturated fatty acid

Has one or more double bonds, with one fewer hydrogen atom on each double-bonded carbon. Nearly every double bond in naturally occurring fatty acids is cis, which creates a kink in the hydrocarbon chain wherever it occurs.

Phospholipid

Major constituents of cell membranes. Has two fatty acids attached to glycerol instead of three.

3rd hydroxyl group of glycerol is joined to a phosphate group which has a negative electrical charge in the cell. An additional small charged or polar molecule is usually also linked to the phosphate group.

One end is hydrophobic (hydrocarbon tails), the other is hydrophilic (phosphate group + its attachments heads). When added to water, they form a bilayer that shields fatty acid tails from water. Heads are on the outside of it, in contact with water. Tails point toward the interior, away from the water.

Steroid

Lipids characterized by a carbon skeleton consisting of four fused rings.

Cholesterol

A type of steroid. Common component of animal cell membranes. Synthesized in the liver and obtained from the diet.

Protein

A biologically functional molecule made up of one or more polypeptides, each folded and coiled into a specific three-dimensional structure.

All constructed from the same set of 20 amino acids, linked in unbranched polymers.

Catalyst

Chemical agents that speed up chemical reactions without being consumed by the reaction.

Enzyme

A protein that acts as a catalyst to regulate metabolism. It is able to do its job over and over again, so it keeps cells running by carrying out the processes of life.

Polypeptide

A polymer of amino acids.

Amino acid

An organic molecule with both an amino group and a carboxyl group.

At the center is an asymmetric carbon atom called the alpha (α) carbon, whose four different partners are an amino group, carboxyl group, hydrogen atom, and a variable group (R group, also called side chain) which differs with each.

It is the sequence of these in a protein that determine the three-dimensional shape it will have.

Peptide bond

When two amino acids are positioned so the carboxyl group of one is adjacent to the amino group of the other, they can become joined by a dehydration reaction. The resulting covalent bond with removal of a water molecule.

Denaturation

When pH, salt concentration, temperature, or other aspects of its environment are altered, the weak chemical bonds and interactions within a protein may be destroyed, causing it to unravel and lose its native shape.

Can also result from chemicals that disrupt hydrogen bonds, ionic bonds, and disulfide bridges that maintain a protein’s shape.

Can also result from excessive heat.

Nucleic Acid

Polymers made of monomers called nucleotides.

RNA

Ribonucleic acid.

Messenger ___ (m___) Interacts with a cell’s protein-synthesizing machinery to direct production of a polypeptide, which creates or folds into a protein.

Transfer ___ (t___) brings amino acids to the ribosome during the synthesis of a polypeptide.

Adenine, guanine, cytosine, uracil

More variable in shape. Versatile molecules.

DNA

Deoxyribonucleic acid.

The genetic material that organisms inherit from their parents.

The information that programs all the cell’s activities is encoded into the structure of this, but is not directly involved in running the operations of the cell. Proteins carry out these functions.

Adenine, guanine, cytosine, thymine

Always exists as a double helix.

Gene expression

The process of DNA providing directions for its own replication, as well as synthesis of RNA, and through RNA, controlling protein synthesis.

Purine

A family of nitrogenous bases. Has a six-membered ring fused to a five-membered ring. Adenine (A) and guanine (G).

Pyrimidine

A family of nitrogenous bases. Has one six-membered ring of carbon and nitrogen ions. Cytosine (C), thymine (T), uracil (U).

Deoxyribose

The sugar in DNA to which the nitrogenous base is attached. Lacks an oxygen atom on the second carbon in the ring.

Ribose

The sugar in RNA to which the nitrogenous base is attached.

Phosphodiester bond (linkage)

Adjacent nucleotides are joined by this, which consists of a phosphate group that links the sugars of two nucleotides.

Results in a repeating pattern of sugar-phosphate units called the sugar-phosphate backbone.

Double helix

DNA molecules have two polynucleotides or “strands” that wind around an imaginary axis.

Antiparallel

The two sugar-phosphate backbones of both strands of the double helix run in opposite 5’ → 3’ directions from each other. (Like a divided highway).

Examples of dehydration reactions

Formation of disaccharides (glycosidic bonds), formation of polypeptides (peptide bonds).

Anything that breaks apart H₂O into a hydroxyl group and hydrogen.

Examples of hydrolysis reactions

Digestion of disaccharides/polysaccharides by turning them into monosaccharides, breakdown of ATP.

Anything that breaks the bond between monomers by adding H₂O.

Monomers of carbohydrates

Monosaccharide

Functions of carbohydrates

To store short-term energy (starch and glycogen)

Monosaccharides are major nutrients for cells (cellular respiration, serve as raw material for synthesis of amino acids/fatty acids)

Polysaccharides provide sugars for cells or serve as building material for structures that protect a cell/organism (cellulose; plant cell walls).

Examples of carbohydrates

Glucose, fructose, maltose, sucrose, starch, glycogen, cellulose, chitin.

Monomers of lipids

Glycerol and fatty acids

Functions of lipids

Fats provide long-term energy storage. They also cushion vital organs and provide insulation.

Phospholipids form a boundary between the cell and its external environment and establish separate compartments within eukaryotic cells.

Steroids are a common component of animal cell membranes and serve as the precursor from which other steroids, such as sex hormones, are synthesized.

Examples of lipids

Trans fats, saturated fats, unsaturated fats, cholesterol.

Monomers of proteins

Amino acids

Functions of proteins

Regulate metabolism by acting as catalysts, play a role in defense, storage, transport, cellular communication, movement, or structural support. Carry out the instructions coded in DNA. Carry out the processes of life.

Examples of proteins

Enzymes, structural proteins, defense proteins

Monomers of nucleic acids

Nucleotides

Functions of nucleic acids

DNA stores the information and genetic material passed down from parents. Programs all the cell’s activities, while proteins have to carry it out.

RNA can direct production of polypeptides, which become proteins, and can bring amino acids to the ribosome during polypeptide synthesis.

Examples of nucleic acids

DNA, RNA

Functions of starch

Stores excess glucose, storing energy for plants for when they need it.

Functions of glycogen

Stores short-term energy for animals.

Functions of cellulose

Protects a plant’s cell wall.

Functions of chitin

Animals, specifically arthropods, use this to build their exoskeletons.

4 levels of protein structure

Primary structure - created by peptide bonds

Secondary structure - created by hydrogen bonds

Tertiary structure - created by hydrophobic interactions, disulfide bridges, van der Waals interactions

Quaternary structure - created by hydrophobic interactions, hydrogen bonds, ionic bonds, van der Waals interactions, disulfide bridges

Covalent bonds in DNA

Link DNA nucleotides together to form the long strands of each molecule.

Hydrogen bonds in DNA

Link the complementary bases of opposing strands together to form the double helix.