Biology Short Answers

List two mechanisms that enzymes use to lower the activation energy or speed up a reaction.

The activation site of an enzyme clutches the bound substrates. the activation site may also provide a microenvironment that is more conductive to a particular type of reaction. direct participation of the activation site in the chemical reaction, this can involve covalent bonding and the sidechain of amino acids.

If a Paramecium caudatum swims from a hypotonic to an isotonic environment, will its contractile vacuole become more active or less? Why?

The contractile vacuole would become less active. In a hypotonic solution, the concentration of solutes inside of the cell is higher than the solutes outside. Water enters the cell to regulate the concentration, causing the cell to expand. To prevent hemolysis, the contractile vacuole frequently pumps out water to counteract osmosis. In an isotonic solution, the rate of osmosis would be less, and so the contractile vacuole wouldn't need to be as active.

Differentiate between the primary, secondary, tertiary and quaternary structure of a protein. Identify the types of bonds/interactions and the relative stability of each interaction (compared to peptide bonds)

The primary structure of a protein is simply the straightened out sequence of amino acids that are held together by very stable peptide bonds. The secondary structure of a protein is used to describe how the protein folds itself via backbone interactions (H bonds between carboxyl and amine groups). Most commonly, proteins fold into alpha helices and beta sheets. Both the beta sheet and alpha helix are stabilized by hydrogen bonding. Tertiary structure refers to how the protein folds itself after the secondary structure. It is accomplished through H bonds, nonpolar interactions, hydrophobic interactions, London dispersion forces, and disulfide bridges. Quaternary structure describes how multiple polypeptide chains can bond with each other. The same interactions in tertiary structure stabilize the quaternary structure.

What is the fundamental basis for the differences between carbohydrates, protein, and nucleic acids?

Carbohydrates (glucose, fructose, and sugar) are the main source of energy for living organisms, and are made up of carbon, hydrogen, and oxygen. Proteins are the building blocks of life, made from amino acids. Proteins are made up of the linked series of carbon, nitrogen, and oxygen. Two well known nucleic acids include RNA and DNA, and they are made up of carbon sugar, a phosphate group and a nitrogenous base.

How are starch and cellulose different from each other? What role do starch and cellulose play in the human body?

Glucose comes in 2 forms: an alpha formation and a beta formation. While both starch and cellulose are made from glucose, starch is made out of the alpha formation and cellulose is made from beta glucose. In the digestive system, enzymes are able to break down alpha glucose, but not beta glucose. This is why the body can digest starch but not cellulose. Starch is used for energy storage since it can be broken down, but cellulose is used to make digestion easier, since it doesn't break down.

Suppose you eat a serving of fish. What reactions must occur for the amino acid monomers in the protein of the fish to be converted to new proteins in your body?

In order for the proteins in a fish to be digested, enzymes must break apart the chain of amino acids by catalyzing a hydrolysis reaction. The monomers are then joined together in peptide bonds via dehydration synthesis, forming new proteins.

Identify 3 macromolecules that make up the cell membrane and briefly explain the primary job that each performs as part of the cell membrane.

Lipids: These are arranged in a bilayer with a hydrophobic tail and a hydrophilic head, which makes them amphipathic. The hydrophilic end is exposed to water, and the hydrophobic part is protected. Carbs: Lipids:

Explain how the compartmental organization of a eukaryotic cell contributes to its biochemical functioning.

Organelles that interact with each other have the means to reach one another. This compartmentalization also allows the isolation and concentration of reactants, causing chemical reactions to potentially go faster.

Proteins are the most structurally and functionally diverse class of biological molecules. Explain the basis for this diversity.

Proteins are diverse for multiple reasons. First, proteins are made of amino acids, which all contain different types of R groups. The R groups contribute to the shape of the protein but also allow proteins to be very diverse, since the R group varies for each amino acid. Each protein is made with a specific order of amino acids, and a change in the order of the amino acids will result in a differently shaped protein. In addition to this, proteins maintain a specific shape by making complex interactions via H bonds, hydrophobic interactions, ionic interactions, and disulfide bridges. Multiple protein chains can also form interactions with each other creating large and complex multi-proteins. Between the amino acid order as well as intermolecular forces and bonds, the shape and function of proteins are extremely varied and diverse.

Describe the structural and functional distinctions between rough and smooth ER.

Rough ER -tend to be present in large numbers in protein producing cells -contains ribosomes attached to outside (membrane bound) Smooth ER -found near cytoplasm -tend to be present in large numbers in cells producing lipids and hormones -found near cell membrane

The soil immediately around hot springs is much warmer than that in neighboring regions. Two closely related species of native grasses are found, one in the warmer region and one in the cooler region. If you analyzed their membrane lipid compositions, what would you expect to find? Explain.

You would find that the grasses living in the cooler region would have more unsaturated fatty acids in their membranes because the unsaturated fats remain fluid at lower temperatures, helping the cell maintain a flexible membrane. In addition, the grass in colder regions may have higher levels of cholesterol in their membranes, because it allows the membrane to stay more fluid at lower temperatures.