Biological Molecules and Enzymes

Most biological molecules can be classified as ______, ______, ______ or _______ _______. Each of these types of molecules possesses a ______ skeleton. Together with ______ and ______, they form living cells and their environments.

_____ is the solvent in which the chemical reactions of living cells take place. 70 to 80 percent of a cell 's mas is made up of ______. Water is a small ______ molecule that can participate in hydrogen bonding. Most compounds as light as water would exist as a ____ at typical cell temperatures.

The ability of water molecules to form ______ bonds with each other elevates the ______ point; as a result, water remains in a _____ state in the cellular environment.

Hydrogen bonding also provides strong cohesive forces between water molecules, thus "squeezing" ________ (Greek: hydros ~ water, phobos ~fear) molecules away from water and causing them to aggregate.

By contrast, hydrophilic molecules or ionic compounds dissolve easily in water. (explain)

Besides ac ting as a solvent, water often acts as a ______ and ______. Most macromolecules of living cell s are broken apart via _______ (Greek: lysis ~ separation) and are formed via ________.

Define hydrolysis reaction (give an example)

Define dehydration reaction

Lipids are essential to life and perform a variety of functions in the body. While the types of lipids are characterized by a variety of _______ and ______ groups, they all share the same defining characteristics (Name them). In other words, lipids are ______ and _____

What are the three roles lipids can play in organism

State the major groups of lipids (9)

Besides being lipids themselves, fatty acids are the building blocks for most, but not all, ______ _______. They act as _____ for the body and are components of the _______, _______, and ________ of cell membranes.

Fatty acids are composed of long chains of _______ truncated at one end by a ______ ______. They usually contain an _____ number of carbons. In humans, the maximum number of carbons in a fatty acid is ___. Fatty acids can be saturated or unsaturated, what is the main difference?

_______ of fatty acids liberates large amounts of chemical energy (short-term) for a cell. Conversely, fatty acids can be used for ______ _____ energy storage.

The high concentration of ______-______ bonds in fatty acids allows them to store more energy per gram than any other _________ in the body. Most fats reach the cell in the form of free fatty acids, meaning fatty acid chains not attached to a backbone, rather than as triacylglycerols.

Triacylglycerols, phospholipids, and glycolipids are sometimes referred to as _____ _____. Triacylglycerols (Latin: tri ~ three), commonly called _______ or _____ ______ and _____, are constructed from a _____ ______ backbone called ______, which is attached to ______ ______ ______ chains (as shown in Figure 1.3).

Their function in a cell is to _____ _____. They can also provide ______ ______ and _______ to an organism. Adipocytes (Latin: adips ~fat , Greek: kytos ~ cell), also called ____ cells, are specialized cells whose cytoplasm contains almost nothing but ________.

Phospholipids are lipids with a ______ group attached. For the purposes of the MCAT®, the most important phospholipids are ________. Like triglycerides, phosphoglycerides are built from a _______ backbone, but a ______ ______ group replaces one of the _____ _____.

The phosphate group lies on the opposite side of the ______ from the fatty acids, making the phospholipid _____ at the phosphate end and _______ at the fatty acid end. Molecules that have a polar and nonpolar end are referred to as _______ (Latin: ambo ~ both), and this quality makes phospholipids especially well suited as the major component of biological membranes.

When forming bilayer membranes, the _____ heads of phospholipids are able to face toward the ______ environment within and outside the cell, while the tails create a ______ _____ _____ with in the membrane, creating a barrier to ______ molecules that allows the ______ of their passage in and out of the cell.

Clycolipids (Greek: glucus ~sweet) are similar to phosphoglycerides, except that glycolipids have one or more ______ attached to the _____-_____ ______ backbone in stead of the ______ group. Glycolipids are also _______. They are found in abundance in the membrane of ______ cells in the human nervous system.

Sphingolipids are also similar to phosphoglycerides, in that they have a _____ _____ ______ acid and a _____ head group. However, rather than glycerol, the backbone molecule is an amino alcohol called a _______. (One type of sphingolipid, _______, has a phosphate group attached to the sphingosine backbone and is thus a _______, although it is not a phosphoglyceride.) Like phospholipids, glycolipids, and steroids, sphingolipids make up part of the ______ ______.

Steroids are four ringed structures. They include some ______, ______ and _______, an important membrane component.

Terpenes are a sixth class of lipids that are often part of ______ in the body. They include _______, which is important for vision.

Waxes are another type of lipid that are formed by an _____ linkage between a long-chain _____ and a long-chain _____ ____. They have a variety of functions in different types of organisms, determined by their characteristic _____-______ texture. _____ _____ is an example of a wax in the human body.

Another class of lipids (not shown in Figure 1.3 but often listed as a fatty acid) are the ____ ______ _______ (Greek: eikosi~twenty). Eicosanoids include ______, ________ and _______.

Eicosanoids are released from cell membrane as _____ ______ that regulate, among other things, ____ _____, ______ ______ and _____ ______ ______. ______is a commonly used inhibitor of the synthesis of prostaglandins.

Because lipids are ______ in aqueous solution, they are transported in the blood via _______. A lipoprotein contains a lipid core surrounded by ______ and ______. Thus the lipoprotein is able to dissolve lipids in its _______ core, and then move freely through the aqueous solution due to its _______ shell.

Lipoproteins are classified by their ______. The greater the ratio of _____ to _____, the lower the density. List the 4 major classes of lipoproteins in humans. (For more on lipoproteins, see the Digestive and Excretory Systems Lecture in Biology 2: Systems.)

Major functions of lipids (4)

The primary biological importance of carbohydrates lies with their usefulness in _______ ______ and providing easily accessible ______ to the body. As with fats, the high concentration of __-__ bonds in carbohydrates allows for the storage of a _____ amount of energy. Why don't carbohydrates store as much energy per gram as lipids?

The _______ structure of carbohydrates allows them to be easily stacked together in the cell , which contributes to their usefulness for energy storage.

The structure of carbohydrates also makes it possible for them to join together through a ________ reaction, forming long chains, _________, for ______ storage. The reverse _______ reaction allows the release of single sugar molecules, _________, that the tissues can use for ______.

Carbohydrates can be thought of as carbon and water in a fixed ____-to-____ ratio. For each carbon atom there exists ____ oxygen atom and ____ hydrogen atoms. What is the formula for carbohydrates?

The carbohydrates most likely to appear on the MCAT® are ______ and ______. Both are six carbon carbohydrates called _______. Glucose (Greek: glucus ~ sweet) is the most commonly occurring ____ carbon carbohydrate.

The Fischer projections of fructose and glucose are shown in Figure 1.4. Glucose normally accounts for __% of the carbohydrates absorbed by humans. Almost all digested carbohydrates reaching body cells have been converted to ______ by the _____ or ________(intestinal cells). Draw the fischer projections for both glucose and fructose

The cell can oxidize glucose to transfer its chemical energy to a more readily usable form, ____. If the cell already has sufficient ATP, glucose is polymerized to the polysaccharide form, ______, or converted to ____.

Glycogen (define) is found in all ______ cells, but especially large amounts are found in ______ and ______ cells. The liver regulates the _____ _____ level, so liver cells are one of the few cell types capable of reforming glucose from ______ and releasing it back into the ________ when needed.

Only certain ______ cells in the ______ tract and the _____ ______ of the kidney are capable of absorbing glucose against a concentration gradient. This is done via a ______ ______ ______ mechanism down the concentration gradient of ______.

All other cells absorb glucose via ______ ______. Insulin increases the rate of ______ ______ for glucose and other __________. In the absence of insulin, only _____ and _____ cells are capable of absorbing sufficient amounts of glucose via the ______ _______ system.

Just like animals, plants join _______ molecules to form polysaccharides. Plants use _____ for long-term storage instead of glycogen. Starch comes in two forms: _______ and ______. Amylose may be ______ or ______ and has the same alpha linkages as _______. Amylopectin resembles _______ but has a different _______ structure.

Plants also use glucose molecules to form _______. It is used as a structural material rather than for energy storage, and in contrast to starch andglycogen, it is composed of _____ linkages.

Like most animals, humans have enzymes to digest the ______ linkages of ______ and ______ but do not have enzymes that can digest the ______ linkages of _______. Some animals such as cows have ______ in their digestive systems that release an enzyme to digest the _____ linkages in cellulose. Recent research suggests that certain insects do produce an enzyme to digest the ____ linkages of cellulose.

Nucleotides are an important class of molecules that are involved in the cell 's use of ______ as well as comprising the building blocks of every organism's ______ material. Name the three components that make them up:

The three components of nucleotides allow them to form the characteristic structure of ____, as described below. The highly stable _____, along with the ______ groups, are able to link together to form a stable and organized backbone. Both are polar and thus can face ______ into the watery solvent of the cell.

Meanwhile, the nitrogenous bases can form _____ _____ _____ with each other that stabilize the double-stranded structure of DNA but can also be separated to allow the ______ of genetic material.

A nucleoside consists of a _____ sugar attached to a ______ base. Nucleotides are formed by the addition of one or more _______ groups to a ______. Nucleotides form polymers to create the _____ _____, _____ and ____, which allow for the expression of genetic traits by specifying the production of ______ (see the Genetics Lecture).

In nucleic acids, nucleotides are joined together into long strands by _______ bonds between the ______ _____ of one nucleotide and the _____ carbon of the pentose sugar of the other nucleotide, forming a _____-______ _______.

By convention, a strand of nucleotides in a nucleic acid is written as a list of its _______ bases. A nucleotide attached to the number 3 carbon (3') of its neighbor follows that neighbor in the list. In other words, nucleotides are written in the ____ to ___ direction (__~__). By convention, DNA is written so that the top strand runs ___~___ and the bottom runs ___~___.

Four nitrogenous bases exist in DNA (deoxyribonucleic acid): adenine (A), guanine (G), cytosine (C), and thymine (T). Adenine and guanine are ____ ring structures called _____, while cytosine and thymine are ______ ring structures called _______.

DNA usually exists in a particular form described by the _____-_____ model, named for the scientists who are credited with first theorizing the structure of DNA. In this typical structure, also known as the ______, the two strands lie side by side in opposite 3'~ 5' directions (________) bound together by ______ bonds between nitrogenous bases, forming a double stranded structure. This ______ bonding is commonly referred to as base-pairing.

The length of a DNA strand is measured in base-pairs (bp). Under normal circumstances, the hydrogen bonds form only between specific _____-______ pairs; ______ forms 2 hydrogen bonds with _____ and _____ forms 3 hydrogen bonds with ______. Therefore, in order for two strands to bind together, their bases must match up in the correct order. Two strands that match in such a fashion are called _______ strands.

When complementary strands bind together, they curl into a _____ _____ (Figure 1.7). The double helix contains two distinct grooves called the major groove and the minor groove. Each groove spirals _____ around the double helix for every ____ base pairs. This structure of DNA is ______ in the cellular environment and allows for ______ of genetic material.

RNA (ribonucleic acid) is identical to DNA with three major differences. List them

Unlike DNA, RNA can move through the _____ _____ and is not confined to the ______. Three important types of RNA, which will be described further in the Genetics Lecture, are _____, _____, and ______. Also, notice the similarity in structure between ______ and _____. This is a common cause of _______ in DNA.

In addition to forming genetic material, nucleotides also serve other purposes in the cell. Name three such nucleotides