bio 100 first test

What is the relationship between acids, bases, and hydroxide ions?

-Acids contain relatively few hydroxide ions, whereas bases contain excess hydroxide ions.

Why are chloroplasts essential to the survival of many animals as well as plants?

-Animals do not have chloroplasts and must depend on organisms that can photosynthesize the energy they need.

How does the cell wall protect prokaryotic cells in a hypotonic solution?

-Because cells swell in a hypotonic environment, the bacterial cell wall counteracts the outward osmotic pressure and prevents the cell from bursting

You have identified an enzyme that breaks down a storage form of sugar in plants (starch) into simple sugars. How would this enzyme react with a storage form of sugar (glycogen) in humans

-Because enzymes are specific, the plant enzyme's active site would not bind to glycogen as a substrate.

How do prions cause disease?

-They cause properly folded proteins to fold incorrectly, creating more prions which collect in nerve tissue and cause brain damage.

How might lysosomes affect physical health? Select the TWO answers that are correct.

-Because lysosomes regulate lipid metabolism based on environmental cues, they might contribute to disorders such as obesity. -Because malfunctioning lysosomes result in accumulation of waste products in the cell, they might affect organismal longevity.

Which statements describe catabolic and anabolic reactions? Select the TWO answers that are correct.

-Catabolic reactions remove chemical bonds and result in larger substances being broken down into smaller ones. -Anabolic reactions add chemical bonds and result in smaller molecules being built up into larger ones.

Which statements describe cofactors and coenzymes? Select the TWO answers that are correct.

-Cofactors and coenzymes both facilitate the binding of enzymes to substrates. -Cofactors can be organic or inorganic molecules, whereas coenzymes are only organic.

How does the shape of an enzyme affect its function? Select the TWO answers that are correct.

-Enzyme shape determines what substrate the active site can bind. -When an enzyme binds a substrate, the enzyme's shape changes to facilitate a chemical reaction.

How are eukaryotic cells different from prokaryotic cells? Select the TWO answers that are correct.

-Eukaryotic cells have organelles, whereas prokaryotic cells do not. -Prokaryotic cells are generally smaller than eukaryotic cells.

Why are eukaryotic cells unaffected by streptomycin and similar antibiotics?

-Eukaryotic protein synthesis is not disrupted because these antibiotics do not disrupt eukaryotic ribosomal activity.

What makes ice less dense than liquid water?

-Hydrogen bonds between water molecules expand when solid.

Polar bears rely on Arctic ice sheets and icebergs on the surface of water as a part of their habitat. How would the habitat of polar bears be affected if solid water was more dense than liquid water?

-Ice would sink rather than float, so there would be no ice sheets or ice bergs.

Why is the phospholipid bilayer important to cell survival? Select the TWO answers that are correct.

-It acts as a barrier for some, but not all, molecules on either side of it. -It separates the cellular environment from the external environment.

When an atom loses an electron, what happens?

-It becomes positively charged.

Consuming excess amounts of the water-soluble vitamin C can lead to

-It is not possible to consume excess amounts of vitamin C.

How does an enzyme affect the activation energy of a reaction?

-It reduces the energy of activation, which makes the reaction it facilitates more likely to occur and speeds up the production of the chemical product.

How are lipids unique when compared to other macromolecule groups?

-Lipids do not contain monomers and they are comprised of compounds

What is the major difference between facilitated diffusion and simple diffusion?

-One requires membrane transport proteins and the other does not.

How do triglycerides and phospholipids differ? Select the TWO answers that are correct.

-Phospholipids have two fatty acid tails, whereas triglycerides have three. -Phospholipids have a hydrophilic phosphate group in place of one fatty acid tail.

Which of these statements is TRUE about prokaryotes and eukaryotes?

-Prokaryotes are smaller and lack the internal compartments that eukaryotes have.

How does the DNA of prokaryotic cells differ from the DNA of eukaryotic cells?

-Prokaryotic DNA is contained in the cytoplasm, whereas eukaryotic DNA is contained in the nucleus.

Why is the phospholipid bilayer considered semipermeable?

-The bilayer is a barrier to some, but not all, substances on either side of it.

You find a single-cell organism with a cell wall in the soil of a forest—can this organism be an animal? Which of the following characteristics would indicate that the organism is a bacterium and not a plant?

-The cell wall is made of peptidoglycan.

If the shape of an enzyme's active site were to change, what would happen to the reaction that the enzyme usually conducts?

-The conversion of substrate to products would decrease and the enzyme would no longer be able to bind to its substrate efficiently.

Which statements describe the structure of the cell membrane? Select the TWO answers that are correct.

-The hydrophilic head interacts with the external environment or the cytoplasm, and the hydrophobic tail interacts with other phospholipid tails within the cell membrane. -The cell membrane is composed of a bilayer of phospholipids, each of which contains a hydrophilic head and a hydrophobic tail.

Which of the following accurately describes why specific material uses a protein to cross the membrane?

-The hydrophobic core of a membrane will only allow hydrophobic (i.e., non-polar) substances to cross without a m

How does the molecular structure of a water molecule affect its polarity?

-The oxygen has a partial negative charge and the hydrogens have a partial positive charge, yielding a weakly polar water molecule that can form hydrogen bonds.

Why do some enzymes need a cofactor in order to function?

-The presence of a cofactor allows some enzymes to bind to their substrates. -

How do penicillin and similar antibiotics affect prokaryotic cells?

-These antibiotics disrupt the formation of the cell wall so it cannot counteract osmotic pressure in a hypotonic environment, resulting in cell lysis.

How do streptomycin and similar antibiotics affect prokaryotic cells?

-These antibiotics interfere with protein synthesis

Which of the following statements best explains why bacteria are considered living organisms?

-They are made of cells

Why are nucleic acids considered macromolecules but not macronutrients?

-They can be assembled into large molecules, but organisms need only small quantities of them in the diet.

What must happen to macromolecules before they can be absorbed by the body?

-They must be digested into their constituent subunits.

How does water dissolve table salt?

-Water is a polar molecule that disrupts ionic bonds between sodium and chloride.

Which of the following are most likely to dissolve in olive oil?

-a nonpolar molecule

Which statement describes a hydrogen bond between two water molecules?

-a weak bond between the slightly negative oxygen atom of one water molecule and the slightly positive hydrogen atoms of another water molecule

A(n) _____ reaction creates bonds between substrate units; a(n) _____ reaction breaks down bonds between substrate units.

-anabolic; catabolic

Which of these cellular components is(are) associated with all cells?

-cell membrane, ribosomes, and DNA

Enzymes speed up chemical reactions by _____

-decreasing the activation energy

Identify the long-established cellular function of lysosomes.

-digest deteriorated cellular structures, food particles, and foreign bacteria

Sugars are large, hydrophilic molecules that are important energy sources for cells. Sugars can enter cells from an environment with a very high concentration of sugar by

-facilitated diffusion.

to repair a cell membrane, which macronutrient would supply the needed building blocks?

-fats

Which of these is a sign of malnutrition?

-fluid buildup in the legs and feet

The "endosymbiotic hypothesis" is a concept that explains

-how eukaryotic cells might have evolved mitochondria and chloroplasts within their cells

In terms of bond strength, which of the following is the weakest?

-hydrogen

Which part of the cell membrane acts as a barrier to hydrophilic molecules entering the cell?

-hydrophobic tails

Which tasks do water vacuoles and cell walls both perform in plant cells? Select the TWO answers that are correct.

-keep plant upright -maintain cell shape

What are the four types of organic molecules that make up all living things on Earth?

-lipids, nucleic acids, carbohydrates, proteins

Which organelle would cause the most damage to cytoskeletal fibers in the cytoplasm if its contents were to leak into the cytoplasm?

-lysosome

What are prions?

-misfolded proteins that can cause disease and spread by causing normal proteins to misfold as well

Which of the following is not found in prokaryotic cells?

-mitochondria

If a solute is moving through a phospholipid bilayer from an area of higher concentration to an area of lower concentration without the assistance of a protein, the manner of transport must be

-simple diffusion

Which of the following types of transport are most closely related in terms of the energy requirements for moving material across a membrane?

-simple diffusion and facilitated diffusion

Current research has shown that lysosomes carry out more tasks than was previously thought. What new roles do we now know lysosomes perform? Select the TWO answers that are correct.

-stimulate digestion of energy reserves under fasting conditions -stimulate cellular growth and reproduction when resources are abundant

A macronutrient is a nutrient

-that is required in large amounts

What is activation energy?

-the energy necessary to initiate a chemical reaction

What functions do membrane proteins serve? Select the TWO answers that are correct.

-transport nutrients into the cell that cannot otherwise cross the phospholipid bilayer -transport wastes out of the cell that cannot otherwise cross the cell membrane

Why do salt crystals form in a pan of seawater from which the water has been evaporated?

In the absence of water, sodium and chloride form ionic bonds and aggregate into crystals.

How do RNA and DNA molecules differ? Select the TWO answers that are correct.

RNA is single-stranded, whereas DNA is double-stranded. Uracil is used in RNA, whereas thymine is used in DNA.

Which substances have an alkaline pH? Select the TWO answers that are correct.

drain cleaner, baking soda

The macronutrients include _

proteins and fats