Bio 13 - Exam 1 - Practice Questions

What are the four classes of lipids and what is an example of each?

1. lipids like margarine 2. wax like the coating on feathers 3. phospholipids like cell membrane constituents 4. steroid like cholesterol

In what situation would the use of a light microscope be ideal? Why?

A light microscope is used to view the growth of cells during an experiment because light does not kill the cells.

Carbohydrates serve various functions in different animals. Arthropods like insects, crustaceans, and others, have an outer layer, called the exoskeleton, which protects their internal body parts. This exoskeleton is made mostly of chitin. Chitin is also a major component of the cell walls of fungi, the kingdom that includes molds and mushrooms. Chitin is a polysaccharide. What is the major difference between chitin and other types of polysaccharides?

Chitin is a nitrogen-containing polysaccharide, with repeating units of N-acetyl-β-D-glucosamine, a modified sugar.

What type of compound functions in hormone production, contributes to membrane flexibility, and is the starting molecule for bile salts?

Cholesterol, which is a lipid and also a steroid, functions here.

How do cilia and flagella differ?

Cilia are short. There can be many or few on the cell surface, whereas flagella are long and never numerous.

Which of the following organisms is a prokaryote? a) Amoeba b) Influenza A virus c) Charophyte algae d) E. coli

E. coli

Animals cannot digest cellulose due to the type of bonding between the glucose monomers. The glucose monomers are there for an energy source but are unattainable. Yet ruminants such as cows and sheep, and termites eat cellulose in the form of grasses and wood. How do they do it?

Specialized bacteria and protists are found in the digestive tracts of these animals making cellulase that result in cellulose breakdown.

Why can water be a good insulator within the body of endothermic (warm-blooded) animals?

Specific heat capacity

Which of these describe some of the similarities and differences between glycogen and starch?

Starch is less branched than glycogen and is found in plants.

Fiber is not really a nutrient, because it passes through our body undigested. Why can't fiber be digested and why is it important to our diet?

The enzymes required to digest cellulose are not produced in human body; undigested fiber adds bulk to the food easing bowel movements.

What type of evidence for life was most likely found in a 3.5 billion year old rock?

The fossil superficially resembles living microbial mats that exist today.

Dehydration is a word usually used to mean the removal of water. How does this apply to macromolecules?

The hydroxyl groups of two monomers are used to form a bond by removing a hydrogen from one monomer and a hydroxyl group from the second forming a molecule of water.

Inhibitors of microtubule assembly, vinblastine for example, are used for cancer chemotherapy. How does an inhibitor of microtubule assembly affect cancerous cells?

The inhibitors restrict the separation of chromosomes, thereby stopping cell division.

List the mass number and atomic number of carbon-12 and carbon-13, respectively.

The mass number and atomic number of carbon-13 is 13 and 66, while that of carbon-12 is 12 and 66, respectively.

Is the nuclear membrane part of the endomembrane system? Why or why not?

The nuclear membrane is part of the endomembrane system as it is continuous with the rough endoplasmic reticulum.

Describe the pH scale and how it relates to living systems. Give an example of how drastic pH changes are prevented in living systems.

The pH scale ranges from 0 to 14, where anything below 7 is acidic and above 7 is alkaline. The bicarbonate system in the human body buffers the blood.

How do phospholipids contribute flexibility to cell membrane structure?

The phospholipids containing unsaturated fatty acids cannot be tightly packed which provides membrane flexibility.

Why do long distance runners "carbo load" before a race?

They eat foods high in starch, a polysaccharide, because they can be broken down slowly into monosaccharide to provide long lasting energy.

Thiomargarita namibiensis is a large single cell organism, which can reach lengths of 700μm. The cell is classified as a bacterium. What is the main argument to justify the classification?

This organism does not show presence of any cell organelles, and thus is classified as a bacterium.

Which of the following statements is false? a) Molecules with the formulas CH3CH2COOHCH3CH2COOH and C3H6O2C3H6O2 could be structural isomers. b) Molecules must have a double bond to be cis-trans isomers. c) To be enantiomers, a molecule must have at least three different atoms or groups connected to a central carbon. Enantiomers are mirror images of each other. d) To be enantiomers, a molecule must have at least four different atoms or groups connected to a central carbon.

c) To be enantiomers, a molecule must have at least three different atoms or groups connected to a central carbon

Name the three functional groups in the compound pictured.

carbonyl, methyl and carboxyl

Which of the following is not an extracellular matrix role of carbohydrates? a) Protect an insect's internal organs from external trauma b) Prevent plant cells from lysing after the plant is watered c) Maintain the shape of a fungal spore d) Provide energy for muscle movement

d) Provide energy for muscle movement

You are making a poster of a generic bacterium for your class. Which of the following structures will you leave out of your poster? a) plasma membrane b) DNA c) nucleolus d) ribosome

nucleolus - A nucleolus is not found in bacteria. Only a nucleoid is present.

Pictured are two cells along with their radius. What does cell B likely have when compared to cell A? a) r= 5um b) r = 50 um

smaller surface area-to-volume ratio

Which structure or structures allow bacteria to move about?

Flagella only

The fluid mosaic model described the plasma membrane, seen here, as a mosaic of components. Why is it advantageous for the plasma membrane to be fluid in nature?

Fluidity allows greater flexibility to the cell and motion of membrane components required for transport.

An experiment was set up to determine the movement of molecules through a dialysis-tubing bag into water. A dialysis-tubing bag containing 5% lactose and 5% fructose was placed in a beaker of distilled water, as illustrated. After four hours, fructose is detected in the distilled water outside of the dialysis-tubing bag, but lactose is not. What conclusions can be made about the movement of molecules in this experiment?

Fructose, being a monosaccharide, diffused through the dialysis bag into the distilled water. However, lactose, being a disaccharide, could not diffuse through the dialysis bag.

Athletes consume large amounts of energy to meet the needs of their high activity level. Carbohydrates are an excellent choice for delivering calories that quickly fuel the body. Which of the following would be the best source of energy for an athlete?

Glucose (6 carbons)

Vesicles pinch off the rough endoplasmic reticulum. Where do they go from there?

Golgi apparatus

What role do electrons play in dehydration synthesis and hydrolysis?

H+ and OH− ions share electrons with the respective monomers in hydrolysis.

How can an unsaturated fat be made to function like a saturated one?

Hydrogen is bubbled through unsaturated fats to form saturated fats and incidentally trans fats.

Identify and explain two ways in which plasma membranes, composed of plasma molecules such as shown here, can remain fluid when the temperature drops.

Increasing the amount of unsaturated fatty acids and cholesterol allows the plasma membranes to remain fluid.

What makes ionic bonds differ from covalent bonds?

Ionic bond involves the transfer of electrons whereas covalent bond involves the sharing of electrons.

Both of the regular intravenous solutions administered in medicine, normal saline and lactated Ringer's solution, are isotonic, such as seen in the middle image here. Why is this important?

Isotonic solutions maintain equilibrium and avoid the exchange of materials to or from the blood.

What characteristic would you expect to find in an organism that appeared early in the history of Earth?

It can grow under extremely harsh conditions

What are three functions that lipids serve in plants and/or animals?

Lipids serve in the storage of energy, as a structural component of hormones, and also as signaling molecules.

Cells lining the intestine absorb a lot of nutrients. How did those cells adapt to their function?

Membrane folds called microvilli increase the surface area.

How are some microbes beneficial?

Microbes aid in digestion

Which organelle is responsible for the production of energy in all eukaryotic cells?

Mitochondria

Which organelles would be present in high numbers in the leg muscles of a marathon runner?

Mitochondria

Why do phospholipids tend to spontaneously orient themselves into something resembling a membrane such as the lipid-bilayer sphere, single-layer lipid sphere, and lipid-bilayer sheet?

Phospholipids are amphipathic molecules. The polar head faces towards water and the nonpolar fatty acid tails face towards other fatty acid tails.

How do phospholipids contribute to cell membrane structure?

Phospholipids orient their heads towards the polar molecules and tails in the interior of the membrane, thus forming a bilayer.

What are the differences in the way lipids are found or function in plants and animals?

Plants store starch and do not have bile salts whereas animals store triglycerides and have bile salts.

The word hydrolysis is defined as the lysis of water. How does this apply to polymers?

Polymers break by separating water into hydrogen and hydroxyl group that are added to the monomers.

You already know that ribosomes are abundant in red blood cells. In what other cells of the body would you find them in great abundance?

Ribosomes are abundant in muscle cells as they contain large amounts of protein-based filaments necessary for contractions.

What is a difference between saturated and unsaturated fats?

Saturated fats are solid at room temperature and unsaturated fats are liquid at room temperature

Compare and contrast saturated and unsaturated fats.

Saturated fats contain single bonds and are solids at room temperature, while unsaturated fats contain double bonds and are liquids at room temperature.

Sodium and potassium are necessary electrolytes. As a result, the human body uses a great deal of energy keeping these electrolytes in balance. Explain why the body needs to use energy for this process.

ATP is required to move sodium ions against their concentration gradient outside the cell.

Why can some insects walk on water?

Because of waters high surface tension

Discuss how buffers help prevent drastic swings in pH.

Buffers absorb excess hydrogen and hydroxide ions to prevent increases or decrease in pH. An example is the bicarbonate system in human body.

What property of carboxyl makes carboxyl containing molecules hydrophilic? Which macromolecules contain carboxyl?

Carboxyl groups release H+, making its parent molecule hydrophilic. It is found amino acids and fatty acids.

What is structurally different between starch and cellulose that gives them different physical properties?

Cellulose is formed by β-1,4 glycosidic linkages and crosslinks, making it rigid. Starch has α-1.4 and α-1.6 glycosidic linkages without the tight crosslinks of cellulose.

What are the similarities and differences between the structures of centrioles and flagella?

Centrioles and flagella are made of microtubules but show different arrangements.

The unique properties of water are important in biological processes. For the following three properties of water, define the property and give one example of how the property affects living organisms: cohesion adhesion high heat of vaporization

Cohesion is the attraction between the water molecules, which helps create surface tension. Insects can walk on water because of cohesion. Adhesion is the attraction between water molecules and other molecules. Water moving up from the roots of plants to the leaves as a result of capillary action is because of adhesion. Heat of vaporization is the amount of energy required to convert liquid into gas. This property helps humans maintain homeostasis of body temperature by evaporation.

The following chemical reactants produce the ester ethyl ethanoate (C4H8O2): C2H6O + CH3COOH What type of reaction occurs to make ethyl ethanoate?

Condensation

The shape of hair proteins is maintained by a combination of hydrogen bonds and covalent, disulfide bonds. Heat is sufficient to break the hydrogen bonds, but harsh chemicals are required to break the disulfide bonds. Why is it harder to break the disulfide bonds than the hydrogen bonds?

Covalent bonds are stronger than hydrogen bonds.

With which cellular structure does the extracellular matrix interact?

Cytoskeleton

If a doctor injected a patient with what was labeled as an isotonic saline solution, but then the patient died, and an autopsy revealed that several of the patient's red blood cells had burst, such as in the image on the right, would it be true that the injected solution was really isotonic? Why or why not?

False, the solution was hypotonic

What are three examples of how the characteristics of water are important in maintaining life?

First, the lower density of water as a solid versus a liquid allows ice to float, forming an insulating surface layer for aquatic life. Second, the high specific heat capacity of water insulates aquatic life or bodily fluids from temperature changes. Third, the high heat of vaporization of water allows animals to cool themselves by sweating.

The sodium-potassium (Na+/K+)(Na+/K+) pump functions like an anti-porter transporting Na+ and K+ across membranes using ATP. This protein spans the membrane with intracellular and extracellular domains. It has a binding site for Na+, K+, and ATP. An experiment was conducted to determine the locations of these binding sites. Artificial cells were created and incubated in buffers containing ATP, ouabain (or oubain), Na+, and K+ in varying combinations inside and outside of the cell as indicated in the chart. The transport of Na+ and K+ was measured to determine activity of the Na+/K+ pump. Which of the following conclusions is supported by the data?

The ATP binding site of the Na+/K+ pump is located on the intracellular domain of the pump.

The Human Immunodeficiency Virus (HIV) infects and kills white blood cells. Over time, what affect does this have on the body's immune system?

The body's immune system would not be able to fight off pathogens like bacteria with fewer white blood cells. This can increase the risk of illness in HIV patients.

You are looking at a sample under a light microscope and observe a new type of cell. You come to the conclusion that it is a bacterium and not a eukaryotic cell. What would you observe to come to this conclusion?

The cell does not have a nucleus

A scientist compares the plasma membrane composition of an animal from the Mediterranean coast with one from the Mojave Desert. Which hypothesis is most likely to be correct?

The cells from the Mojave Desert animal will have a higher cholesterol concentration in the plasma membranes.

What happens to the proteins that are synthesized on free ribosomes in the cytoplasm? Do they go through the Golgi apparatus?

The proteins do not go through the Golgi apparatus and remain free in the cytosol.

How does the sodium-potassium pump contribute to the net negative charge of the interior of the cell?

The sodium-potassium pump forces out three (positive) Na+ ions for every two (positive) K+ ions it pumps in, thus the cell loses a net positive charge of one at every cycle of the pump.

Which of the following is true regarding the surface-to-volume ratios of the cube and the sphere when the diameter of the sphere is equal to the side of the cube?

The sphere will have a lower surface area-to-volume ratio than the cube.

Why does the structure of the cytoplasmic membrane point to a common ancestor of all life?

There is a similar arrangement of phospholipids and proteins in all branches of life.

Bacteria do not have organelles; yet, the same reactions that take place on the mitochondria inner membrane, the phosphorylation of ADP to ATP, and chloroplasts, photosynthesis, take place in bacteria. Where do these reactions take place?

These reactions occur on the plasma membrane of bacteria

Why have trans fats been banned from some restaurants? How are they created?

Trans fat is produced by the hydrogenation of oil that makes it more saturated and isomerized. It increases LDL amounts.

The fatty acids of triglycerides are classified as saturated, unsaturated, or trans fats. What is it about the structure of these compounds that distinguishes them from each other?

Trans fats are a type of unsaturated fat where the hydrogens around the double bond are not in the same plane.

When the temperature of liquid water is reduced, water freezes and becomes less dense. This is a property not seen in most other liquids. Ice floats on liquid water because it is less dense. What molecular property of water allows for this phenomenon?

When water cools, hydrogen bonds between hydrogen atoms push water molecules further apart.