Biology test 1

How does the scanning electron microscope differ from the transmission electron microscope?

The SEM gives a three dimensional image of the object being studied.

DNA is associated with certain proteins, forming a complex called:

chromatin.

plasma membranes are made up of what?

phospholipids.

Which description illustrates an amphipathic molecule?

A phospholipid with both a hydrophobic end and a hydrophilic end.

A chlorine atom has 17 protons and 18 neutrons. What is its atomic mass?

35 amu.

What is the ultimate source of genetic variation within a population?

Mutations in DNA.

Which scenario best describes a double-blind study?

Neither the investigator or the subjects know if they are in the experimental or control group.

Information in living organisms is transmitted by which mechanism(s)?

genes, hormones, and neurotransmitters.

What are units of hereditary information?

genes.

Similar families of organisms are next grouped together in the same:

order.

What organic molecules is the primary structural component of cell membranes?

phospholipids.

What is one cellular characteristic found in all prokaryotic and eukaryotic cells?

plasma membrane.

Which carbohydrate is the most structurally complex?

polysaccharide.

What is the purpose of molecular chaperones?

To assist the folding of other molecular proteins.

Check My Work Which substance is an example of a very strong acid?

lemon juice.

Which pair matches the correct macromolecule with the bond that joins its subunits?

nucleic acid−phosphodiester linkage.

What is the purpose of a buffer?

To minimize the change in pH.

double covalent bonds share how many pairs of electrons?

Two. (four electrons)

You light a scented candle in the guest bathroom. Within a few minutes you can already smell the candle's scent throughout the hallway. What process is occurring?

simple diffusion.

What type of molecule can rapidly cross a plasma membrane?

small, hydrophobic molecules.

A glycoprotein destined for secretion from the cell would move through the Golgi complex which sequence?

cis face to medial region to trans face.

What type of protein accelerates the thousands of different chemical reactions that take place in an organism?

enzyme.

What carbohydrate energy storage molecule is found in animal liver and muscle cells?

glycogen.

What is the microtubule arrangement of a flagellum or cilium?

9 + 2 arrangement.

If tyrosine and isoleucine undergo condensation, where does the new bond form?

Between carbon of the carboxyl group and the nitrogen of the amino group.

What type of molecule carries the hereditary information of an organism?

DNA.

what is exocytosis?

a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.

What is an end product of cellular respiration?

carbon dioxide.

In exocytosis what substance would most likely be used to transport?

hormones.

Which of the following is responsible for the alpha-helical structure of proteins?

hydrogen bonds.

If a red blood cell is put into a solution and there is no change in the cell what type of solution is the cell in?

isotonic.

How can we identify a particular element?

By its number of protons.

description of van der Waal interactions.

They are attractive forces. They involve transient regions of positive and negative charges. They form between nonpolar molecules. They operate over very short distances.

During an experiment, what is the purpose of a control group?

To compare results to the experimental group with the variable being tested.

All of the members of the same species occupying the same area at the same time constitute a(n):

population.

What large molecules are essential in determining the structure and function of cells and tissues?

proteins.

Evidence that all living cells have a common origin is best illustrated by the:

basic similarities in cell structure and chemistry.

A transmembrane protein differs from other membrane proteins because it:

completely extends through the membrane.

amino acids have the same carboxyl group and amino group, how do they differ?

different side chains.

Which component becomes oxidized in the following chemical reaction? 4 Fe + 3 O2 → 2 Fe2O3

iron.

The primary purpose of homeostasis is to:

maintain a constant internal environment.

What is the difference between an electrically neutral atom and an ion?

An ion has an unequal number of protons and electrons, while a neutral atom has an equal number.

What differentiates an organic compound from an inorganic compound?

An organic compound contains carbon.

A patient who has had a severe hemorrhage accidentally receives a large transfusion of distilled water directly into a major blood vessel. What effect will this have on the patient?

It will have serious, perhaps fatal consequences because the red blood cells could swell and burst.

You want to determine the location of a specific protein in a cell using a colored stain. Which of the following is the best technique for this purpose?

fluorescence microscopy.

what is the form of cellular junction in exocytosis?

gap junctions

The overall structure of a complete protein, formed by interactions between two or more polypeptide chains is?

the quaternary structure of a protein.

Which statement best describes the cell theory?

All living organisms are composed of basic units called cells.

How many molecules are present in one mole of C6H12O6?

D. 6.02 × 1023 molecules

What type of cellular junction cements cells together that use cadherins as a belt around each cell?

adhering junctions

What represents the most basic level of chemical organization?

atom.

One of the conclusions drawn from Darwin's theory of evolution is that:

organisms living today descended with modifications from previously existing forms.

A hypothesis can best be described as a(n):

tentative explanation.

What is the OH− concentration of a solution having a pH of 2?

1 × 10−12

How do gap junctions differ from desmosomes?

A gap junction provides communication between cells.

What would be the ultimate effect on an ecosystem if decomposers were eliminated?

All life would eventually cease as nutrients would no longer be available.

____ are loosely associated with the phospholipid bilayer, whereas ____ are tightly bound to it.

Peripheral proteins; integral proteins.

Which process is most directly associated with the theory of evolution?

Populations changing over time.

Identify three of the five basic themes in biology:

The evolution of life, The interactions of living systems, The transmission of information.

What statement best describes "biology"?

The science of life.

phospholipids are:

They have two distinct regions, one strongly hydrophobic and the other strongly hydrophilic, They have cylindrical shapes that allow them to associate with water most easily as a bilayer structure., They are amphipathic molecules, They contain a polar organic group attached to a phosphate group.

Which best describes a result of sexual reproduction?

Two sex cells combine to form a fertilized cell.

An atom X contains 14 protons, 13 electrons, and 12 neutrons, and atom Y contains 14 protons, 14 electrons, and 12 neutrons. What can you conclude?

X and Y are atoms of the same element.

As a result of testing an experimental drip on a vertebrate cell, you notice that the cell cortex becomes more fluid, and although the cell remains strong, it loses its ability to move. Based on this evidence, you correctly conclude that the drug most directly affected:

actin filaments.

Which of the following would most likely form electrolytes in water?

an inorganic compound.

Since sodium-potassium pumps transport sodium ions out of a cell and potassium ions into a cell, what type of carrier proteins are they?

antiporters.

Which cellular structure is correctly matched to the role it plays within the cell?

centrosome−cell division.

What protects a cell and may help keep other cells at a distance?

glycocalyx.

During phagocytosis, what may fuse with the vacuole to further degrade the ingested material?

lysosome.

Plants lack organ systems for disposing of toxic metabolic waste products. Their cells' vacuoles are like what animal cell organelle?

lysosomes.

What two organelles are both responsible for converting energy into forms that can be used by cells?

mitochondria and chloroplasts.

What enzyme in the ER lumen catalyze the efficient folding of proteins into proper conformations?

molecular chaperones.

A liquid with a pH of 7 is considered a(n) ____ solution.

neutral.

A single cell in a smoker's lung has become cancerous. It doubles its DNA and divides much faster than a normal lung cell. The most likely change that would have caused this condition took place in the:

nucleus.

Unlike lipids, hydrophilic functional groups typically contain ____ atoms, which make them more soluble in water.

oxygen.

Which component is the oxidizing agent in the following chemical reaction? 4 Fe + 3 O2 → 2 Fe2O3

oxygen.

What type of bond is formed if one atom is more electronegative than the other atom?

polar covalent

If a toxin, such as a bacterial toxin, destroys ribosomes, what cellular activity will be affected first?

protein synthesis.

A base is defined as a(n) _____ acceptor.

proton.

Amyloplasts are organelles that store:

starch.

Which event illustrates evaporative cooling?

sweat evaporating from the skin.

Which description illustrates the tertiary structure of a protein molecule?

three-dimensional shape of an individual polypeptide chain.

Nitrogen has five electrons in its valence shell. How many electrons does it need to gain to complete its valence shell?

three.

The role of ATP in the sodium-potassium pump is to:

transfer protons to the outside of a cell.

What does the accompanying figure of two elemental structures with the same number of electrons but different number of protons and neutrons represent?

two isotopes of the same element.

What substance is removed during a condensation reaction?

water.

Which substance correctly identifies a reactant in the following chemical equation? CO2 + H2O ↔ H2CO3

water.

The cohesiveness between water molecules is due largely to:

hydrogen bonds.

What is the primary function of mitochondria?

transformation of energy.

In the experimental evaluation of a new drug, what is the purpose of a placebo?

A placebo removes the potential psychological bias of the patient in the study.

Why is it advantageous for cells to be small?

A small cell has a small volume relative to surface area, thereby increasing efficient transport.

What does an ABC transporter use to transport larger ions and molecules across the cell membrane?

ATP.

Which statement best describes autotrophic organisms?

Autotrophs synthesize complex molecules from CO2, water, and energy.

To which Phylum do humans belong?

Chordata.

Which statement best summarizes the differences between RNA and DNA?

DNA comprises the genes, while RNA is a direct participant in the process of protein synthesis.

What happens during the cotransport of glucose and sodium ions?

Glucose molecules are transported against their concentration gradient.

Proteins made on ribosomes may be further modified within which organelle?

Golgi complex.

Which organelle can be considered a sorting, processing and packaging center?

Golgi complex.

Why is ATP important in living organisms?

It can transfer some of its energy to other chemicals.

Which description best illustrates the product of a chemical reaction?

It is generally written on the right side and is the substance generated by the reaction.

What does the process of differential centrifugation achieve?

It separates components of the cell that have different densities.

Which statement best describes the activity of the sodium-potassium pump?

It transports 3 sodium ions out of the cell in exchange for 2 potassium ions.

What have studies of glucose transport in liposomes revealed?

The binding of glucose triggers a conformational change in the carrier protein.

Why are hydrocarbons considered hydrophobic?

The covalent bonds between hydrogen and carbon are nonpolar.

How do the phospholipids in vegetable oil differ from those of animal fat?

The fatty acid tails bend.

As water boils and turns to steam, what happens to the hydrogen bonds?

The hydrogen bonds break.

Which is a benefit of sexual reproduction over asexual reproduction?

The interaction of the genes from both parents brings about genetic variation.

Why can table salt (NaCl) dissolve easily in water?

The partial positive charge of the hydrogens in the water molecule can associate with the negative charge of the chloride ion, and the partial negative charge of the oxygen of the water molecule can associate with the positive charge of the sodium atom.

A person has a genetic disease that prevents the phospholipids in the plasma membrane of the white blood cells from freely fusing with the other membranes within the cell. How would this disease affect phagocytosis?

The phagocytic vacuole would not fuse with the lysosome.

If phospholipids form a spherical structure when placed in water, then which of the following is the most logical conclusion about those phospholipid molecules?

They are cone-shaped.

Centrioles are:

They are duplicated before cell division, They are thought to play a role in microtubule assembly, They are found in the centrosome, They are present in most animal cells but not most plant cells.

Which is a property of unsaturated fats?

They are generally liquid at room temperature.

In the experiment in which Frye and Edidin fused the plasma membranes of a mouse and a human cell, what happened to the membrane proteins?

They moved laterally across the cell surface.

What is the purpose of regulatory proteins?

To control the expression of specific genes.

When a small amount of hydrochloric acid (HCl) is added to a solution of Na2HPO4, the pH of the solution does not change markedly. The pH also does not change drastically when a small amount of sodium hydroxide (NaOH) is added to this same solution. Based on these observations, the compound Na2HPO4 is:

acting as a buffer.

Peripheral proteins are linked to either surface of the plasma membrane by:

bonding to integral proteins through noncovalent interactions.

What cellular structure is unique to plant cells and some photosynthetic fungi?

chloroplasts.

When we know what kinds of ____ are present in an organic compound, we can predict its chemical behavior.

functional groups.

Plasmodesmata of plant cells are functionally equivalent to the ____ of animal cells.

gap junctions.

Suppose a particular protein is produced in excess of the cell's needs. What kind of mechanism will intervene to stop production?

homeostatic.

The covalent bond between a hydrogen atom and the oxygen atom in water is formed when:

hydrogen and oxygen share an electron pair.

Which characteristic of water molecules directly contributes to water striders remarkable "water walking" success?

hydrogen bonds.

A wilted flower placed in a vase of water for several hours became stiff and stood erect. When it was placed in a salt solution, it wilted. From this information, we can say that the cells of the flower are:

hypertonic to fresh water but hypotonic to the salt solution.

Which organic compound is not only responsible for energy storage, but also can provide thermal insulation?

lipids.

DNA must transcribe its information into what type of molecule before leaving the nucleus and entering the cytoplasm?

mRNA.

Proteins that are destined to become associated with the inner surface of the plasma membrane are:

made on free ribosomes in the cytoplasm.

The ratio of the size of the image seen with the microscope to the actual size of the object is called:

magnification.

Using the Linnaean system of nomenclature, corn is named Zea mays. What is the specific epithet in this name?

mays.

In living organisms, chemical reactions responsible for growth, repair, and nutrition are collectively referred to as:

metabolism.

What is found between the primary walls of adjacent cells for cells to adhere tightly to one another?

middle lamella

During an infection, white blood cells travel to the infected site and phagocytize the pathogens. After phagocytosis, primary lysosomes fuse with the phagocytic vesicle to form a larger vesicle called a secondary lysosome. The purpose for this process is to:

mix the pathogens with strong hydrolytic enzymes and destroy them and coat the bacteria in lipids derived from the Golgi complex, which cover and smother them.

The term "fluid mosaic model" refers to the:

movement of lipids and integral proteins within the lipid bilayer.

an amino acid that has single straight bonds would make the side chain?

nonpolar.

A DNA molecule is made up of:

nucleotides.

Which molecule is least likely to cross a cellular membrane by simple diffusion?

potassium ion.

You discover an organism that is eukaryotic, unicellular, and photosynthetic. Based on this evidence, to which group would you assign this organism?

protist group.

What does the nucleolus, within the nucleus, synthesize?

ribosomal RNA.

the sharing of two electrons represents?

single covalent bond.

The representation H−O−H is known as a(n):

structural formula.

Which functional group forms bridges to help stabilize a protein's quaternary structure?

sulfhydryl.

What process halts the net movement of water from a hypotonic solution into a plant's cells and often provides the structural support to many plants?

turgur pressure.