ANPS 019 Lab #1

B) mRNA (messenger RNA) The mRNA molecule is organized into groups of 3 nucleotides called codons. These codons pair up with tRNA molecules that contain the anti-codon that is complementary to the mRNA codon. The sequence of codons in the mRNA molecule specifies the sequence of amino acids that will be used to build the new polypeptide chain.

A molecule of _______________ contains all the codons needed to produce a particular polypeptide. A) tRNA (transfer RNA) B) mRNA (messenger RNA) C) rRNA (ribosomal RNA)

B) polar covalent bonds The unequal electron distribution produces a slight negative charge on the oxygen and a slight positive charge on the hydrogens. These slight charges give water many unique characteristics that make it ideal for many physiological processes.

A molecule of water (H2O) is formed by what type of bond? A) nonpolar covalent bonds B) polar covalent bonds C) ionic covalent bonds D) weak bonds

B) a codon During translation, each mRNA codon is matched with an anti-codon on a tRNA molecule that carries a specific amino acid.

A sequence of three nucleotides on mRNA is called: A) an amino acid B) a codon C) an exon D) an anti-codon

F) ribosome

What is G? A) centrioles B) golgi apparatus C) lysosome D) mitochondrion E) nucleus F) ribosome G) rough endoplasmic reticulum H) smooth endoplasmic reticulum

C) a charge of +1 If sodium loses an electron, it will become a positively charged ion (cation). Although not shown explicitly in the figure, the element sodium contains 11 protons within its nucleus. We know this because sodium had 11 electrons before it gave one up, and the number of protons in an atom equals the number of electrons. If sodium forms a cation containing 10 electrons (by giving one to chloride), it will have a charge of +1.

After the transfer of an electron, sodium will form an ion with __________. A) an atomic number of 18 B) a charge of -1 C) a charge of +1 D) an atomic number of 10

C) 8 protons, 8 electrons, and 10 neutrons The atomic number is the number of protons in an atom, and the atom will have the same number of electrons, to balance the electrical charge. Mass number is the number of protons plus the number of neutrons, so subtracting atomic number from mass number reveals the number of neutrons. The number of protons and electrons is constant for all atoms of any element, but the number of neutrons can vary. Atoms of the same element that differ in the number of neutrons are called isotopes. So, the correct answer is that the atom of oxygen described in this question has 8 protons, 8 electrons and 10 neutrons.

An atom of oxygen has an atomic number of 8 and a mass number of 18. How many of each type of subatomic particle does it contain? A) The atomic number and the mass number do not provide enough information to determine how many of each subatomic particle is present. B) 8 protons, 8 neutrons, and 8 electrons C) 8 protons, 8 electrons, and 10 neutrons D) 18 total subatomic particles

B) No, because the atoms have only 6 valence electrons, but need 8 for stability. To be stable, by the Octet Rule an atom must have 8 electrons in its outermost orbital. An atom of oxygen has a total of 8 electrons. 2 of the electrons reside in the first orbital (innermost), which leaves 6 electrons in the next or outermost orbital. With only 6 valence electrons, oxygen atoms are unstable and will seek ways to get or share two more electrons to become stable.

Atoms of oxygen have a total of 8 electrons. Are these atoms stable, and why or why not? A) Yes, because the Octet Rule says stable atoms have 8 electrons. B) No, because the atoms have only 6 valence electrons, but need 8 for stability. C) Yes, because oxygen is in the air we breathe and it doesn't hurt us. D) No, because only atoms with 2 valence electrons are stable.

B) The introns, or non-coding regions, must be removed from the pre-mRNA molecule. During mRNA processing, the introns, which are regions of the mRNA molecule that don't carry part of the recipe for the protein must be removed.

Before the mRNA transcribed from a gene can be used to create a protein, what must occur? A) The introns and exons must be spliced together. B) The introns, or non-coding regions, must be removed from the pre-mRNA molecule. C) The exons, or noncoding regions, must be removed from the pre-mRNA molecule.

B) single covalent bonds Each shared pair of electrons represents a single covalent bond

Bonds between carbon and hydrogen atoms (as depicted on the right side of the figure) are generally __________. A) hydrogen bonds B) single covalent bonds C) double covalent bonds D) ionic bonds

A) +2 With atomic number 20, calcium atoms have 20 positive protons. The question tells you that calcium forms ions with only 18 electrons, which means that it has given up 2 of its electrons, in order to have a stable or full outer valence shell. If a calcium ion has 20 positive protons, but only 18 negative electrons, the net charge of the calcium ion is +2. Calcium ions are essential for muscle contractions, nerve impulses, and bone maintenance.

Calcium's atomic number is 20. It forms ions with 18 electrons. What is the electrical charge of a calcium ion? A) +2 B) -1 C) +1 D) -2

D) Yes, because they can become more stable by doing so. Since Carbon only has 4 valence electrons, it will react with other atoms in an attempt to gain 4 more electrons (by the octet rule). Atoms react with other atoms to gain stability, typically by gaining, losing, or sharing electrons to attain a full outermost orbital. Atoms with full outermost electron orbitals are less likely to react and are referred to as being inert (i.e., the inert gases such as helium, argon and neon already have full valence shells).

Carbon atoms have four valence electrons. Are they likely to react with other atoms, and why or why not? A) No, because they do not have enough valence electrons. B) No, because they have an even number of valence electrons so they are already stable. C) Yes, but only with other stable atoms. D) Yes, because they can become more stable by doing so.

B) sugar Excellent! Both the sugar and the tea (powdered or leaf) are solutes.

Consider sweetened ice tea. Which of the following is a solute? A) water B) sugar C) ice D) the beverage itself

D) mRNA

What is A? A) amino acid B) anticodon C) large subunit of ribosome D) mRNA E) small subunit of ribosome F) tRNA

A) Lactated Ringer's solution or Normal saline solution Remember - Na+ is a critical component of body fluids and is necessary to maintain the correct water balance in the body. Lactated Ringer's solution and Normal saline solution are isotonic with the extracellular fluid in the body, so will not disrupt osmotic balance. You will learn more about tonicity of solutions when we talk about osmosis in a later lab exercise (cell transport processes).

Dehydration and fluid loss have several adverse effects on patient wellbeing. What type of IV fluids are commonly used in these circumstances? A) Lactated Ringer's solution or Normal saline solution B) Distilled water

1. U 2. C 3. G 4. A

Drag the correct labels onto the nucleotides in the RNA transcript. Not all labels will be used. 1. What is A? 2. What is B? 3. What is C? 4. What is D? Possible Answers: A C G T U

A) slightly different mRNA transcripts that code for different proteins. Because of alternative splicing, one mRNA transcript can be processed to slightly different versions of mRNA that code for different proteins.

During RNA processing, alternative splicing can result in A) slightly different mRNA transcripts that code for different proteins. B) identical mRNA transcripts that code for identical proteins. C) new DNA template strands that code for many different proteins.

A) the exons are joined back together Introns (non-coding regions) are removed and exons (coding regions) are spliced back together.

During splicing, A) the exons are joined back together B) a cap is added C) a poly(A) tail is added D) the introns are joined back together

D) chloride Yes, chloride is a major extracellular anion (negative ion). Chemically speaking, ionic compounds that dissociate easily into their respective ions when dissolved in water are called electrolytes. In this course, we also use the term electrolytes to refer to the charged particles or ions that result when ionic compounds, or salts are dissolved in water, because this is the common usage of the term in the health care profession.

Electrolytes are charged particles called ions that are dissolved in body fluids. Which of the following ions would be considered a major anion in the body? A) calcium B) potassium C) sodium D) chloride

D) C is the product of reaction 1 and a reactant for reaction 2. Excellent! In metabolic pathways, it is common for one reaction to produce something that then becomes a reactant for the next reaction.

Examine the following reactions, which occur in a series. For instance, Reaction 2 follows Reaction 1, Reaction 3 follows Reaction 2, and so on. Which of the following is true about compound C? A) C is a product for reaction 2 only. B) C is the reactant of reaction 1 and a product for reaction 2. C) C is a reactant for reaction 1 only. D) C is the product of reaction 1 and a reactant for reaction 2.

H) smooth endoplasmic reticulum

What is A? A) centrioles B) golgi apparatus C) lysosome D) mitochondrion E) nucleus F) ribosome G) rough endoplasmic reticulum H) smooth endoplasmic reticulum

C) Water acts as a reactant. Yes, water molecules are necessary for salivary amylase to hydrolyze starch to glucose in your mouth. Thus, water acts as an important reactant.

Foods are broken down into their building blocks by adding water in a chemical reaction called hydrolysis. This would be an example of which characteristic of water? A) Water acts as a lubricant. B) Water has a high heat of vaporization. C) Water acts as a reactant. D) Water acts as a cushion.

D) polar covalent bonds Hydrogen gets a slight positive charge from the unequal sharing of electrons in polar covalent bonds, and it bonds to another atom with a slightly negative charge, again resulting from unequal electron sharing due to a polar covalent bond.

Formation of hydrogen bonds requires hydrogen atoms and what else? A) oxygen B) water C) ionic bonds D) polar covalent bonds

D) Golgi apparatus The Golgi apparatus is responsible for final processing, sorting, and packaging of proteins.

From the rough endoplasmic reticulum, proteins are often sent to the ______________ for further posttranslational modification: A) mitochondrion B) Smooth Endoplasmic Reticulum C) ribosome D) Golgi apparatus

D) Sodium (Na+) In this course, you will learn that water follows Na+ (sodium) in and out of cells. In order to rehydrate your patients, you must ensure that IV fluids have the correct concentration of Na+.

Having the correct concentration of which chemical is most important in rehydrating your patients? A) Calcium (Ca++) B) Potassium (K+) C) Water (H2O) D) Sodium (Na+)

B) Ions of opposite electrical charges are attracted to each other to balance the charges. Ions of opposite charges are drawn together to balance out their charges. Once they bond, they form an ionic compound that can store and transport the ions, or dissociate (separate), releasing the ions, which can then be used by the body.

How do ions form ionic bonds? A) One atom swaps all of its negative electrons for all of the other atom's positive protons. B) Ions of opposite electrical charges are attracted to each other to balance the charges. C) Ions of the same type are drawn together because they are attracted to their own kind. D) Two atoms come together to share their electrons.

B) four Carbon has an atomic number of 6 and has four electrons in its outermost (valence) electron shell.

How many valence shell electrons does the element carbon have? A) two B) four C) six D) eight

C) The hydrogen atom has 1 proton and no neutrons. The mass number of an atom describes the number of protons plus the number of neutrons in that atom. In the case of hydrogen, with a mass number of 1, the number of protons plus neutrons equals 1. We know that the number of protons is 1, because the atomic number tells us how many protons hydrogen has. This means that hydrogen must not have any neutrons: 1 + 0 = 1. We also know that every atom has the same number of electrons and protons, so hydrogen also has one electron (since it has one proton).

If a hydrogen atom has an atomic number of 1, and a mass number of 1, what does this tell us about the hydrogen atom? A) The hydrogen atom has 1 proton and no electrons. B) The hydrogen atom has 1 proton, 1 neutron and 1 electron. C) The hydrogen atom has 1 proton and no neutrons. D) The hydrogen atom has 1 proton, 1 neutron and no electrons.

C) Atoms share one or more pairs of electrons. In covalent bonds, atoms share ("co") their valence electrons ("valent"). These bonds are strong because to maintain stability the atoms must stay close enough together to continue sharing their electrons.

In a covalent bond, A) Adjacent atoms share a single electron. B) An atom gains one or more electrons from another atom to gain stability. C) Atoms share one or more pairs of electrons. D) An atom loses electrons to another to gain stability.

C) a solute, specifically both a colloid and an electrolyte Yes, colloids are large particles dispersed in body fluids. Since most proteins have a negative charge, they are also considered to be electrolytes.

In plasma, a typical body fluid, protein floating around would be considered to be which of the following? A) a solvent B) a solute, specifically both a colloid and a nonelectrolyte C) a solute, specifically both a colloid and an electrolyte

1 = A 2 = D 3 = B 4 = C 5 = E

Match the events of RNA processing to the picture. A) A modified guanine nucleotide is added to the beginning of the RNA strand as a cap B) Extra adenine nucleotides are added to the end of the RNA strand, forming a tail C) Segments of the RNA strand that do not actually code for the protein are removed D) Segments of the RNA that do code for the protein are reconnected E) The completed messenger RNA (mRNA) leaves the nucleus

D) peptide Most hormones are short chains of amino acids called peptides. Peptides are chains of amino acids joined together by a peptide bond (a type of covalent bond) in a process called dehydration synthesis. In the process of dehydration synthesis, a water molecule is removed and two molecules are joined together to form a different molecule or product (in this case, a growing peptide - we'll learn more about protein synthesis in a later exercise).

Most hormones have which chemical structure? A) steroid B) lipid C) cholesterol D) peptide

C) nuclear pores mRNA (and other important molecules) are able to travel from the nucleus to the cytoplasm through nuclear pores.

Movement of the mRNA molecule from the nucleus to the cytoplasm occurs through A) nucleoli B) transport proteins C) nuclear pores D) DNA transport channels

D) are the result of equal sharing of electrons between the atoms of the molecule. Nonpolar molecules are electrically balanced because of the equal sharing of electrons between the atoms that make up the molecule. Because the electrons are shared equally, nonpolar molecules are not charged. We will learn later that nonpolar molecules are lipid soluble and can pass easily through the lipid bilayer that makes up the cell membrane.

Nonpolar molecules A) are charged and are attracted to water. B) always result in slight electrical charges at different atoms. C) are the result of unequal sharing of electrons between the atoms of the molecule. D) are the result of equal sharing of electrons between the atoms of the molecule.

C) outermost electron shell The term valence shell refers to the outermost orbital shell that contains the electrons that are available for chemical bonding.

Part complete The valence shell is the ________________________. A) electron shell closest to the nucleus. B) innermost electron shell. C) outermost electron shell.

C) an electrical attraction between opposite charges The transfer of an electron results in ions with opposite charges that are electrically attracted to each other.

Part complete What holds the sodium and chloride ions together in a chemical bond? A) the attraction between their respective nuclei B) the sharing of a pair of electrons C) an electrical attraction between opposite charges D) the sharing of a pair of protons

C) on free ribosomes Proteins that are destined to spend their lives in the cytoplasm (i.e. cytoplasmic enzymes) or nucleus (i.e. histones) are usually synthesized entirely on free ribosomes within the cytoplasm. Proteins that are destined to be associated with membrane (i.e. either membrane proteins or proteins destined to be secreted in vesicles) finish their assembly in the rough endoplasmic reticulum. The golgi apparatus is where final packaging and modification of proteins (i.e. adding a carbohydrate) occurs.

Proteins that are destined to stay in the cytosol (for use by the cell) are synthesized entirely A) on ribosomes associated with the rough ER B) in the Golgi apparatus C) on free ribosomes D) in the nucleus

E) 3,1,6,2,5,4

Put the following steps of protein synthesis in the correct order: 1. mRNA is produced in the nucleus 2. Ribosome moves along mRNA 3. DNA uncoils for transcription 4. Polypeptide is produced 5. tRNA brings amino acids to ribosome 6. mRNA travels to ribosome A) 2,4,6,1,3,5 B) 3,4,6,1,2,5 C) 1,5,3,6,2,4 D) 2,1,5,4,3,6 E) 3,1,6,2,5,4

B) electron The subatomic particle with a negative charge is the electron. Protons are positively charged and neutrons are neutral - they have no charge.

The ______________ is the subatomic particle with the negative charge. A) proton B) electron C) neutron

A) protons By definition, the atomic number of an atom refers to the number of protons the atom has. Because each atom has the same number of electrons and protons, it would also tell you how many electrons the atom has. (i.e because a carbon atom has 6 protons, it also has 6 electrons, and its atomic number is 6).

The atomic number of an atom refers to the number of _________________ in an atom. A) protons B) protons plus electrons C) protons plus neutrons D) neutrons

D) RNA polymerase RNA polymerase synthesizes mRNA during transcription.

The enzyme that synthesizes the RNA strand during transcription is: A) DNA polymerase B) helicase C) transcription factor D) RNA polymerase

B) 8 The second orbital shell can hold up to 8 electrons. We will learn later that electrons in the outermost shell are involved in chemical bonding - atoms are most stable when they have 8 electrons in their outermost, or valence shell.

The first electron shell of an atom can hold two electrons, while the second shell can hold up to _____________ electrons. A) 1 B) 8 C) 4 D) 2

D) UAG UAG is the mRNA sequence that is complementary to the DNA sequence ATC. Remember, there is no T (thymine) base in RNA, so U is the mRNA base that is complementary to A (adenine) in DNA. G (guanosine) and C (cytosine) are complementary in either DNA or RNA molecules.

The mRNA sequence that is complementary to the sequence ATC on the DNA template strand is A) UTG B) TAG C) ATC D) UAG

A) tRNA (transfer RNA) Transfer RNA (tRNA) molecules carry the amino acids to the ribosomes.

The molecule that brings the proper amino acid into place at the ribosome for the elongation of a new polypeptide is called A) tRNA (transfer RNA) B) rRNA (ribosomal RNA) C) ssDNA (single-stranded DNA) D) mRNA (messenger RNA)

B) lemon juice Lemon juice, at pH 2.5, is the most acidic substance in the figure. The closer the pH is to 0, the more acidic is the substance, because there is a higher concentration of free hydrogen ions.

The most acidic substance in the above figure is __________. A) bleach B) lemon juice C) pure water D) milk

C) Golgi apparatus The golgi apparatus packages, modifies and segregates proteins for secretion from the cell, inclusion in lysosomes, or incorpation into the plasma membrane.

The organelle where cell proteins are modified and packaged is the A) ribosomes B) nucleus C) Golgi apparatus D) mitochondria

B) is selectively permeable.

The plasma membrane of a healthy cell A) is nonpermeable and does not let anything through. B) is selectively permeable. C) is fully permeable and lets anything across.

B) transcription The process in which a molecule of mRNA is created from the DNA template is called transcription.

The process of forming mRNA from DNA is called: A) duplication B) transcription C) translation D) replication

C) ribosomes in the cell cytoplasm. Translation occurs at ribosomes in the cell cytoplasm.

The site of translation is A) the Golgi apparatus. B) the plasma membrane. C) ribosomes in the cell cytoplasm. D) ribosomes in the cell nucleus. E) the cell nucleus.

C) inhibit translation Ricin inhibits protein synthesis by preventing translation, which occurs at the ribosome.

The toxin ricin rapidly and completely deactivates the ribosome. It is lethal to humans, because it will: A) inhibit transcription B) inhibit protein folding C) inhibit translation D) inhibit RNA processing after transcription

D) carbon, oxygen, hydrogen, and nitrogen. All matter, and therefore all of our body parts are made of atoms. Even though our bodies are quite complex, the vast majority of the atoms in our bodies come from just four of the more than 100 known elements. Atoms from the four elements carbon, oxygen, hydrogen, and nitrogen make up about 96% of our body weight; 20 others are also present in the body, some in trace amounts.

The vast majority of the atoms in our body come from which 4 elements? These 4 elements comprise approximately 96% of our body weight. A) carbon, oxygen, iron, and potassium B) carbon, oxygen, potassium, and sodium. C) carbon, oxygen, hydrogen, and potassium. D) carbon, oxygen, hydrogen, and nitrogen.

B) It contains 10% solute and 90% solvent. Excellent! In this example, the salt is the solute, and it is dissolved in some solvent. In our bodies, that solvent is always water. The solution is the mixture of the solute added to the solvent.

Think about a 10% saline solution (saline refers to salt.). Which of the following is a correct statement? A) It contains 10% solvent and 90% water. B) It contains 10% solute and 90% solvent. C) It contains 10% salt and 90% solution. D) It contains 10% solvent and 90% solute.

E) nonpolar tail of phospholipid molecule

What is A? A) cholesterol B) glycolipid C) glycoprotein D) integral proteins E) nonpolar tail of phospholipid molecule F) peripheral proteins G) polar head of phospholipid molecule

A) chromatin

What is A? A) chromatin B) cytosol C) intermediate filaments D) microtubule E) nuclear envelope F) nucleolus G) plasma membrane

D) RNA processing

What is B? A) DNA B) Polypeptide C) Pre-mRNA D) RNA processing E) Ribosome F) Transcription G) Translation H) mRNA

D) 100 times more concentrated First, because the pH of vinegar is 3, and the pH of coffee is 5, we know that vinegar has more hydrogen ions than coffee - a lower pH is more acidic, which means that the H+ concentration is higher. So now, how do we know how much higher the H+ concentration is? Each shift in pH unit represents a 10-fold shift in H+ concentration. Moving from pH 5 to pH 3 is considered two pH units, so each unit shift is a 10-fold shift (in this case, an increase) in H+ concentration. 10 X 10 = 100, so the H+ concentration in vinegar is 100 times more concentrated than in coffee. More detail and another example: The pH scale runs from 0 to 14 and is logarithmic. This means that each change of pH unit represents a 10 fold change in the concentration of hydrogen ions (H+). The pH scale is a negative logarithm of the hydrogen ion concentration in moles per liter. So for a solution that has a pH of 3, the H+ concentration is 10-3 M. For a solution of pH 7, the H+ concentration is 10-7 M, which means that the number of hydrogen ions is 10 X 10 X 10 X 10, or 10,000 times lower than the pH 3 solution, because pH 7 is less acidic than pH 3.

Vinegar, which has a pH of 3, has a H+ concentration that is __________________ than coffee, which has a pH of 5. A) 20 times less concentrated B) 20 times more concentrated C) 100 times less concentrated D) 100 times more concentrated E) 1000 times more concentrated

A) Water acts as a solvent because the partial negative charge on the oxygen in water attracts sodium, while the partial positive charge on hydrogen attracts chloride. This results in the separation of sodium from chloride, thus breaking the ionic bond. Yes, salt (NaCl) is an ionic compound that can be separated by the polar water molecule. Ionic compounds that dissociate easily into their respective ions when dissolved in water are called electrolytes. In this course, we also use the term electrolytes to refer to the charged particles or ions that result when ionic compounds, or salts are dissolved in water.

Water acts to dissolve molecules in the body. How does water dissolve the salt (NaCl) in your mouth from a salty pretzel? A) Water acts as a solvent because the partial negative charge on the oxygen in water attracts sodium, while the partial positive charge on hydrogen attracts chloride. This results in the separation of sodium from chloride, thus breaking the ionic bond. B) Water acts as a cofactor for enzymes that dissolve the salt. C) When water is added to the NaCl, NaCl is broken down by adding OH- to one element and H+ to the other. This is known as hydrolysis.

B) plasma membrane, cytoplasm and nucleus

What are the three main parts of a human cell? A) mitochondria, plasma membrane and nucleus B) plasma membrane, cytoplasm and nucleus C) cytoplasm, mitochondria and nucleus D) nucleus, nuclear membrane and cytoplasm

C) The cell has a great metabolic demand. Mitochondria are threadlike or lozenge-shaped membranous organelles. In living cells they squirm, elongate, and change shape almost continuously. They are the power plants of a cell, providing most of its ATP supply.

What can we infer if we see a large number of mitochondria in a cell? A) The cell builds a lot of cholesterol. B) The cell produces a great deal of protein. C) The cell has a great metabolic demand. D) The cell packages a great deal of proteins for secretion.

A) They all have an incomplete valence electron shell. The valence shell is the outermost electron energy level. Valence shell electrons determine the reactivity of an element.

What do these four elements have in common? A) They all have an incomplete valence electron shell. B) They would all be likely to form positive ions. C) They all have the same number of protons in their nuclei. D) They are all generally unreactive elements.

B) the formation of ions, followed by ionic bonding Ions are formed following the complete transfer of one or more electrons from one atom to another, then the electrical attraction between these ions can form an ionic bond.

What does this figure depict? A) nonpolar covalent bonding B) the formation of ions, followed by ionic bonding C) hydrogen bonding D) formation of a polar covalent bond

B) Oxygen atoms have a stronger pull on the electrons shared within a covalent bond formed between oxygen and hydrogen. Oxygen atoms are highly electronegative and pull electrons away from the electropositive hydrogen atom. Also, the nonbonding (lone) electron pairs on the oxygen, which are responsible for bending the molecule, are negative.

What explains the negative charge on the oxygen atom within the water molecule? A) Protons are transferred from oxygen to hydrogen during the formation of an ionic bond. B) Oxygen atoms have a stronger pull on the electrons shared within a covalent bond formed between oxygen and hydrogen. C) Hydrogen atoms have a stronger pull on the electrons shared within a covalent bond formed between oxygen and hydrogen. D) Electrons are transferred from hydrogen to oxygen during the formation of an ionic bond.

C) synthesis of proteins Structure A is the rough endoplasmic reticulum (ER). The figure illustrates how proteins are synthesized on ribosomes bound to the rough ER, sorted and modified in the Golgi apparatus, and delivered to the plasma membrane for secretion or packaged into lysosomes. Protein synthesis can also occur on free ribosomes in the cytoplasm.

What important cell function occurs at the structures indicated by A? A) replication of DNA B) digestion of ingested food C) synthesis of proteins D) production of most of the cell's ATP

B) amino acids

What is A? A) alpha helix B) amino acids C) beta-pleated sheets D) fibrous protein E) globular protein F) peptide bond G) primary structure H) quaternary structure I) secondary structure J) tertiary structure

F) Transcription

What is A? A) DNA B) Polypeptide C) Pre-mRNA D) RNA processing E) Ribosome F) Transcription G) Translation H) mRNA

F) peptide bond

What is B? A) alpha helix B) amino acids C) beta-pleated sheets D) fibrous protein E) globular protein F) peptide bond G) primary structure H) quaternary structure I) secondary structure J) tertiary structure

E) small subunit of ribosome

What is B? A) amino acid B) anticodon C) large subunit of ribosome D) mRNA E) small subunit of ribosome F) tRNA

D) mitochondrion

What is B? A) centrioles B) golgi apparatus C) lysosome D) mitochondrion E) nucleus F) ribosome G) rough endoplasmic reticulum H) smooth endoplasmic reticulum

D) integral proteins

What is B? A) cholesterol B) glycolipid C) glycoprotein D) integral proteins E) nonpolar tail of phospholipid molecule F) peripheral proteins G) polar head of phospholipid molecule

F) nucleolus

What is B? A) chromatin B) cytosol C) intermediate filaments D) microtubule E) nuclear envelope F) nucleolus G) plasma membrane

G) Translation

What is C? A) DNA B) Polypeptide C) Pre-mRNA D) RNA processing E) Ribosome F) Transcription G) Translation H) mRNA

G) primary structure

What is C? A) alpha helix B) amino acids C) beta-pleated sheets D) fibrous protein E) globular protein F) peptide bond G) primary structure H) quaternary structure I) secondary structure J) tertiary structure

C) large subunit of ribosome

What is C? A) amino acid B) anticodon C) large subunit of ribosome D) mRNA E) small subunit of ribosome F) tRNA

C) lysosome

What is C? A) centrioles B) golgi apparatus C) lysosome D) mitochondrion E) nucleus F) ribosome G) rough endoplasmic reticulum H) smooth endoplasmic reticulum

F) peripheral proteins

What is C? A) cholesterol B) glycolipid C) glycoprotein D) integral proteins E) nonpolar tail of phospholipid molecule F) peripheral proteins G) polar head of phospholipid molecule

B) cytosol

What is C? A) chromatin B) cytosol C) intermediate filaments D) microtubule E) nuclear envelope F) nucleolus G) plasma membrane

B) Polypeptide

What is D? A) DNA B) Polypeptide C) Pre-mRNA D) RNA processing E) Ribosome F) Transcription G) Translation H) mRNA

C) beta-pleated sheets

What is D? A) alpha helix B) amino acids C) beta-pleated sheets D) fibrous protein E) globular protein F) peptide bond G) primary structure H) quaternary structure I) secondary structure J) tertiary structure

A) amino acid

What is D? A) amino acid B) anticodon C) large subunit of ribosome D) mRNA E) small subunit of ribosome F) tRNA

A) centrioles

What is D? A) centrioles B) golgi apparatus C) lysosome D) mitochondrion E) nucleus F) ribosome G) rough endoplasmic reticulum H) smooth endoplasmic reticulum

C) glycoprotein

What is D? A) cholesterol B) glycolipid C) glycoprotein D) integral proteins E) nonpolar tail of phospholipid molecule F) peripheral proteins G) polar head of phospholipid molecule

D) microtubule

What is D? A) chromatin B) cytosol C) intermediate filaments D) microtubule E) nuclear envelope F) nucleolus G) plasma membrane

A) DNA

What is E? A) DNA B) Polypeptide C) Pre-mRNA D) RNA processing E) Ribosome F) Transcription G) Translation H) mRNA

A) alpha helix

What is E? A) alpha helix B) amino acids C) beta-pleated sheets D) fibrous protein E) globular protein F) peptide bond G) primary structure H) quaternary structure I) secondary structure J) tertiary structure

F) tRNA

What is E? A) amino acid B) anticodon C) large subunit of ribosome D) mRNA E) small subunit of ribosome F) tRNA

E) nucleus

What is E? A) centrioles B) golgi apparatus C) lysosome D) mitochondrion E) nucleus F) ribosome G) rough endoplasmic reticulum H) smooth endoplasmic reticulum

B) glycolipid

What is E? A) cholesterol B) glycolipid C) glycoprotein D) integral proteins E) nonpolar tail of phospholipid molecule F) peripheral proteins G) polar head of phospholipid molecule

C) intermediate filaments

What is E? A) chromatin B) cytosol C) intermediate filaments D) microtubule E) nuclear envelope F) nucleolus G) plasma membrane

C) Pre-mRNA

What is F? A) DNA B) Polypeptide C) Pre-mRNA D) RNA processing E) Ribosome F) Transcription G) Translation H) mRNA

I) secondary structure

What is F? A) alpha helix B) amino acids C) beta-pleated sheets D) fibrous protein E) globular protein F) peptide bond G) primary structure H) quaternary structure I) secondary structure J) tertiary structure

B) anticodon

What is F? A) amino acid B) anticodon C) large subunit of ribosome D) mRNA E) small subunit of ribosome F) tRNA

G) rough endoplasmic reticulum

What is F? A) centrioles B) golgi apparatus C) lysosome D) mitochondrion E) nucleus F) ribosome G) rough endoplasmic reticulum H) smooth endoplasmic reticulum

A) cholesterol

What is F? A) cholesterol B) glycolipid C) glycoprotein D) integral proteins E) nonpolar tail of phospholipid molecule F) peripheral proteins G) polar head of phospholipid molecule

E) nuclear envelope

What is F? A) chromatin B) cytosol C) intermediate filaments D) microtubule E) nuclear envelope F) nucleolus G) plasma membrane

H) mRNA

What is G? A) DNA B) Polypeptide C) Pre-mRNA D) RNA processing E) Ribosome F) Transcription G) Translation H) mRNA

E) globular protein

What is G? A) alpha helix B) amino acids C) beta-pleated sheets D) fibrous protein E) globular protein F) peptide bond G) primary structure H) quaternary structure I) secondary structure J) tertiary structure

G) polar head of phospholipid molecule

What is G? A) cholesterol B) glycolipid C) glycoprotein D) integral proteins E) nonpolar tail of phospholipid molecule F) peripheral proteins G) polar head of phospholipid molecule

G) plasma membrane

What is G? A) chromatin B) cytosol C) intermediate filaments D) microtubule E) nuclear envelope F) nucleolus G) plasma membrane

D) fibrous protein

What is H? A) alpha helix B) amino acids C) beta-pleated sheets D) fibrous protein E) globular protein F) peptide bond G) primary structure H) quaternary structure I) secondary structure J) tertiary structure

E) Ribosome

What is H? A) DNA B) Polypeptide C) Pre-mRNA D) RNA processing E) Ribosome F) Transcription G) Translation H) mRNA

B) golgi apparatus

What is H? A) centrioles B) golgi apparatus C) lysosome D) mitochondrion E) nucleus F) ribosome G) rough endoplasmic reticulum H) smooth endoplasmic reticulum

J) tertiary structure

What is I? A) alpha helix B) amino acids C) beta-pleated sheets D) fibrous protein E) globular protein F) peptide bond G) primary structure H) quaternary structure I) secondary structure J) tertiary structure

H) quaternary structure

What is J? A) alpha helix B) amino acids C) beta-pleated sheets D) fibrous protein E) globular protein F) peptide bond G) primary structure H) quaternary structure I) secondary structure J) tertiary structure

A) an atom that has either gained or lost electron(s) Ions form when atoms gain or lose electrons to attain a full valence shell, which gives them an electrical charge. Ions can be stored in the body, such as ions of calcium and phosphate that are stored in our bones, or can be available individually for many physiological processes. For example, Na+ is required for muscle contraction, nerve impulse conduction, and regulation of blood pressure.

What is an ion? A) an atom that has either gained or lost electron(s) B) an atom that is sharing electrons with another atom C) an atom that has lost one or more neutrons D) an atom that loses all of its protons

B) modification and packaging of proteins This function is handled by the Golgi apparatus within the endomembrane system; it functions in the sorting and modifying of membrane-bound proteins being transported to various cellular locations.

What is the function of the organelle indicated by B? A) cellular division B) modification and packaging of proteins C) catabolism of fats and sugars D) synthesis of proteins from amino acids

B) to produce energy in the form of ATP Mitochondria are the power plants of the cell, providing most of its ATP supply.

What is the function of this organelle? A) to produce proteins B) to produce energy in the form of ATP C) to digest or break down components of the cell

B) the sharing of electron pairs between two atoms Covalent bonds are formed by the sharing of electrons between two reactive atoms.

What is the most significant factor in the formation of a covalent bond? A) the attraction of a hydrogen atom's nucleus to the nucleus of another atom B) the sharing of electron pairs between two atoms C) the transfer of one or more protons from one atom to another D) the complete transfer of one or more electrons from one atom to another

B) anti-codon The sequence of 3 nucleotides on the tRNA molecule that specifies a particular amino acid is called the "anti-codon". Anti-codons on tRNA are complementary to codons on mRNA molecules.

What is the name for the 3 nucleotide sequence on a tRNA molecule? A) amino acid B) anti-codon C) gene D) codon

A) Epithelial Cell

What kind of cell? A) Epithelial Cell B) Erythrocyte C) Fat Cell D) Fibroblast E) Macrophage F) Nerve Cell G) Skeletal Muscle Cell H) Smooth Muscle Cell I) Sperm

B) Erythrocyte

What kind of cell? A) Epithelial Cell B) Erythrocyte C) Fat Cell D) Fibroblast E) Macrophage F) Nerve Cell G) Skeletal Muscle Cell H) Smooth Muscle Cell I) Sperm

C) Fat Cell

What kind of cell? A) Epithelial Cell B) Erythrocyte C) Fat Cell D) Fibroblast E) Macrophage F) Nerve Cell G) Skeletal Muscle Cell H) Smooth Muscle Cell I) Sperm

D) Fibroblast

What kind of cell? A) Epithelial Cell B) Erythrocyte C) Fat Cell D) Fibroblast E) Macrophage F) Nerve Cell G) Skeletal Muscle Cell H) Smooth Muscle Cell I) Sperm

E) Macrophage

What kind of cell? A) Epithelial Cell B) Erythrocyte C) Fat Cell D) Fibroblast E) Macrophage F) Nerve Cell G) Skeletal Muscle Cell H) Smooth Muscle Cell I) Sperm

F) Nerve Cell

What kind of cell? A) Epithelial Cell B) Erythrocyte C) Fat Cell D) Fibroblast E) Macrophage F) Nerve Cell G) Skeletal Muscle Cell H) Smooth Muscle Cell I) Sperm

G) Skeletal Muscle Cell

What kind of cell? A) Epithelial Cell B) Erythrocyte C) Fat Cell D) Fibroblast E) Macrophage F) Nerve Cell G) Skeletal Muscle Cell H) Smooth Muscle Cell I) Sperm

H) Smooth Muscle Cell

What kind of cell? A) Epithelial Cell B) Erythrocyte C) Fat Cell D) Fibroblast E) Macrophage F) Nerve Cell G) Skeletal Muscle Cell H) Smooth Muscle Cell I) Sperm

I) Sperm

What kind of cell? A) Epithelial Cell B) Erythrocyte C) Fat Cell D) Fibroblast E) Macrophage F) Nerve Cell G) Skeletal Muscle Cell H) Smooth Muscle Cell I) Sperm

A) large polar molecules Polar molecules contain covalent bonds that share electrons unequally. This results in an unequal distribution of charges within the molecule, so portions of the molecule carry slight charges. Charged molecules are hydrophilic (attract water molecules) and therefore cannot cross the lipid bilayer of the cell membrane.

What kinds of molecules cannot easily pass through the lipid bilayer of the cell membrane? A) large polar molecules B) fat-soluble molecules C) small non-polar molecules D) lipids

A) The polypeptide chain must be folded into the final 3-dimensional shape. Proteins are only functional when they have been folded into their complex, 3 - dimensional shapes.

What must happen to the polypeptide chain before it becomes a functional protein? A) The polypeptide chain must be folded into the final 3-dimensional shape. B) The polypeptide chain must be unfolded so that all the amino acids are in a single line. C) The protein must be packaged into a vesicle and released from the cell. D) The peptide bonds must be removed.

D) RNA polymerase chooses nucleotides that are complementary to the DNA template strand and adds them one at a time, building the mRNA transcript. Transcription is composed of three basic phases: Initiation, Elongation and Termination. During initiation, the promotor sequence of nucleotides signals the starting point of the gene to be transcribed. Transcription factors and RNA polymerase bind to the promotor region and the enzyme helicase unwinds the DNA double helix. During elongation, RNA polymerase adds nucleotides that are complementary to the nucleotides on the DNA template strand, one at a time, building the mRNA transcript. During termination, RNA polymerase reaches a special base sequence called the termination signal which marks the end of the gene being transcribed.

What occurs during the elongation phase of transcription? A) RNA polymerase encounters a specific terminator sequence on the DNA that signals the end of the gene. The mRNA transcript is released. B) Transcription factors and RNA polymerase bind to the promotor region, a special sequence of nucleotides on the DNA strand that indicates the starting point for RNA synthesis. C) The enzyme helicase unwinds the DNA double helix and stabilizes the two strands of DNA. D) RNA polymerase chooses nucleotides that are complementary to the DNA template strand and adds them one at a time, building the mRNA transcript.

A) exocytosis of secretory proteins The event indicated by C includes the fusion of a secretory vesicle with the plasma membrane and the subsequent release of the vesicle contents to the extracellular space.

What process is indicated by C? A) exocytosis of secretory proteins B) exocytosis of ribosomes from the cell C) exocytosis of RNA from the cell D) digestion of food particles

D) hydrogen bond The attraction between the slightly negative oxygen atom of one molecule and the slightly positively charged hydrogen atom within a separate water molecule is the basis of hydrogen bond formation. It is a form of dipole-dipole interaction.

What type of bond is formed between the oxygen atom of one water molecule and the hydrogen atom of another water molecule? A) ionic bond B) nonpolar covalent bond C) polar covalent bond D) hydrogen bond

B) the outermost electrons In ionic bonding, the atoms' outermost electrons—the valence electrons—are closest to each other and will interact, which leads to bond formation.

When an ionic bond forms, which part(s) of the atoms are directly involved? A) both the protons and the electrons B) the outermost electrons C) the neutrons D) the protons

B) in the DNA within the cell's nucleus The nucleus houses the DNA, which contains the genes. Genes determine what proteins the cell can make, which in turn determines what the cell can do.

Where in a typical eukaryotic cell would you expect to find genes? A) in the nucleolus within the nucleus B) in the DNA within the cell's nucleus C) in chromosomes within the cytosol D) in the chromatin within the cell's cytoplasm

A) a mitochondrion Mitochondria are characterized by an oblong shape with inner and outer membranes.

Which cellular organelle is seen in this figure? A) a mitochondrion B) the nucleus C) the Golgi apparatus D) a lysosome

B) lysosome Lysosomes use their enzymes to break down material, much as our digestive system breaks down the foods we consume. The root "lyse" means to loosen or separate, which is what the enzymes in lysosomes do to the chemical bonds in the items they digest.

Which of the following acts as the digestive system of the cell, breaking down materials? A) nucleus B) lysosome C) ribosome D) endoplasmic reticulum

D) all of these are found in membranes While a double layer of phospholipid molecules makes up the lipid bilayer structure of the membrane, proteins, cholesterol molecules and carbohydrates also contribute to the structure of the cell membrane.

Which of the following can be found in the cell membrane? A) cholesterol B) phospholipids C) proteins D) all of these are found in membranes

B) covalent, ionic, hydrogen In covalent bonds, electrons are shared between atoms; in ionic bonds electrons are lost or gained; but hydrogen bonds are not true chemical bonds—they are weak attractions due to slight electrical imbalances. No electrons are directly involved.

Which of the following correctly ranks the types of chemical bonds, in order, from strongest to weakest? A) ionic, hydrogen, covalent B) covalent, ionic, hydrogen C) hydrogen, covalent, ionic D) hydrogen, ionic, covalent

B) synthesis of proteins that will be associated with membrane The rough ER is the location for synthesis of all proteins secreted from the cell; it also functions as the cell's "membrane factory" because integral proteins and phospholipids that form part of all cellular membranes are manufactured there. If a protein is going to be surrounded by membrane, for example proteins that are secreted from the cell in vesicles, it is produced at the rough ER. Also, proteins that will be inserted into membranes, such as integral membrane proteins (protein transporters and protein channels) are also produced at the rough ER. Proteins that are not associated with membrane are produced on free ribosomes.

Which of the following correctly states the functions that occur at the rough endoplasmic reticulum? A) lipid metabolism, cholesterol synthesis, and synthesis of the lipid components of lipoproteins B) synthesis of proteins that will be associated with membrane C) storage of calcium ions D) absorption, synthesis, and transport of fats

D) Only hydrogen bonds can form between molecules. Because hydrogen bonds are not true bonds, they do not always join atoms together within a single molecule. In water, for example, hydrogen bonds link water molecules together. This is referred to as an intermolecular attraction—it is between different atoms.

Which of the following distinguishes hydrogen bonds from covalent bonds? A) Only ionic bonds can form within molecules. B) Only covalent bonds can form between molecules. C) Only hydrogen bonds can form within molecules. D) Only hydrogen bonds can form between molecules.

E) A molecule of RNA is formed based on the sequence of nucleotides in DNA. During transcription, RNA nucleotides line up with their complementary DNA partners, transcribing the information in DNA into RNA.

Which of the following events occurs during transcription? A) The message in mRNA is translated into a protein. B) Those segments of the RNA strand that do not actually code for the protein are removed. C) mRNA binds to a ribosome in the cytoplasm. D) A cap is added to the RNA molecule. E) A molecule of RNA is formed based on the sequence of nucleotides in DNA.

C) phospholipids The plasma (cell) membrane is a phospholipid bilayer, composed of two parallel sheets of phospholipid molecules lying tail to tail, with their polar heads exposed to water on either side of the membrane. Each lollipop-shaped phospholipid molecule has a polar "head" that is charged and is hydrophilic (hydro = water, philic = loving), and an uncharged, nonpolar "tail" that is made of two fatty acid chains and is hydrophobic. The hydrophobic portions of the phospholipid bilayer forms a chemical barrier that only allows certain substances across (semipermeable membrane).

Which of the following is a component of the plasma membrane that creates a chemical barrier between the inside and the outside of the cell? A) cholesterol B) water C) phospholipids D) proteins

B) mRNA moves from the nucleus to the cytoplasm following RNA processing. mRNA undergoes RNA processing in the nucleus and then moves to the cytoplasm for translation.

Which of the following is a correct statement about mRNA? A) mRNA is transcribed from DNA in the cytoplasm. B) mRNA moves from the nucleus to the cytoplasm following RNA processing. C) mRNA binds directly to amino acids during translation. D) Segments of mRNA that code for protein are removed before translation. E) mRNA includes a cap that consists of extra adenine nucleotides.

A) sucrose D) fructose Excellent! Glucose and fructose are the reactants here. Sucrose is produced, and water is released in the process.

Which of the following is a product in the following reaction? glucose + fructose → sucrose + H2O A) sucrose B) glucose C) oxygen (O2) D) fructose

D) glycosylation Glycosylation is the addition of a short carbohydrate chain to a protein during posttranslational modification.

Which of the following is an example of posttranslational modification? A) mutation B) complementary base pairing C) intron removal D) glycosylation

A) Two hydrogen atoms join together to form a molecule of hydrogen gas. Hydrogen bonds occur when there are polar covalent molecules present, but hydrogen atoms join with each other through nonpolar covalent bonds.

Which of the following is not a result of hydrogen bonds? A) Two hydrogen atoms join together to form a molecule of hydrogen gas. B) An enzyme has a unique shape that allows it to bond only with specific molecules. C) Some hair is straight, some wavy, and some very curly. D) Two strands of DNA are linked together taking a shape similar to a ladder.

D) carbohydrate Excellent! Carbohydrates are held together by covalent bonds, whereas electrolytes are held together by ionic bonds. Chemically speaking, ionic compounds that dissociate easily into their respective ions when dissolved in water are called electrolytes - as described in this animation. In this course, we also use the term electrolytes to refer to the charged particles or ions that result when ionic compounds, or salts are dissolved in water, because this is the common usage of the term in the health care profession.

Which of the following is not an electrolyte? A) salt B) base C) acid D) carbohydrate

D) atoms Atoms are the building blocks of all matter. Atoms react through chemical bonding to form larger structures. Chemical bonding begins with atoms; it does not produce them. All of the structures that we cover in A&P are made from atoms joining with other atoms through chemical bonding.

Which of the following is not produced through chemical bonding? A) the heart B) cells C) adipose (fat) tissue D) atoms

A) They are ionic compounds. Excellent! Electrolytes dissociate, or come apart, in water, releasing ions, which have electrical charges—hence the term "electrolyte." Chemically speaking, ionic compounds that dissociate easily into their respective ions when dissolved in water are called electrolytes - as described in this animation. In this course, we also use the term electrolytes to refer to the charged particles or ions that result when ionic compounds, or salts are dissolved in water, because this is the common usage of the term in the health care profession.

Which of the following is true of electrolytes? A) They are ionic compounds. B) They are produced from water. C) They do not dissolve in water. D) They are held together by covalent bonds.

C) The electrons are shared unequally. Because the electrons are shared unequally, they spend more time around one atom than the other, causing a slight negative charge where they tend to hang out the most, and a slight positive charge where they spend the least time. Polar molecules are the result of unequal sharing of electrons by atoms, and polar molecules have slight charges. Because polar molecules are charged, they are water soluble, not lipid soluble. Water soluble molecules cannot pass easily though the cell membrane and must pass through open pores or use transporters.

Which of the following is true of polar covalent bonds? A) The same number of electrons are gained by one atom as are lost by another. B) They are rather weak bonds. C) The electrons are shared unequally. D) Electrons are shared equally.

D) smooth endoplasmic reticulum: metabolism of lipids The smooth ER also plays a role in synthesizing steroid hormones, absorbing and transporting fats, detoxifying toxins, and breaking down glycogen.

Which of the following organelles is correctly paired with its function? A) Golgi apparatus: produce energy for the cell B) mitochondrion: packaging proteins and lipids C) lysosome: protein synthesis D) smooth endoplasmic reticulum: metabolism of lipids

C) Cells join together to form organelles, which then form our organs and organ systems. Organelles are the functional parts of cells—they are inside the cells, in the cytoplasm. Cells join to form tissues, and the tissues then join to form the organs that work together in organ systems.

Which of the following statements about cells is FALSE? A) Cells are the most basic units of life. B) Although human cells are diverse in size, shape, and function, they have essentially the same organelles and general structure. C) Cells join together to form organelles, which then form our organs and organ systems. D) The cells in our bodies collectively carry out all of the functions necessary for us to stay alive.

B) DNA DNA contains the instructions for making proteins, but these instructions are transcribed to RNA before translation occurs.

Which one of the following does not play a role in translation? A) Amino acids B) DNA C) tRNA D) Ribosomes E) Anticodon

B) ribosomes Proteins are synthesized at ribosomes. Free ribosomes float freely in the cytoplasm and produce soluble proteins that function in the cytosol, as well as those imported into mitochondria and some other organelles. Fixed ribosomes, which stud the rough endoplasmic reticulum, synthesize proteins destined either for incorporation into the cell membrane or lysosomes, or for export from the cell.

Which organelle is responsible for synthesizing proteins? A) smooth endoplasmic reticulum B) ribosomes C) rough endoplasmic reticulum D) Golgi apparatus

B) pH of 3 Yes, the lower the pH, the more acidic the fluid. pH is inversely related to the number of H+ ions. As the number of H+ ions increases (and thus the acidity increases), the pH decreases. Therefore, a pH of 3 is the most acidic of the three values given. The pH scale runs from 0 to 14 and is logarithmic. This means that each change of pH unit represents a 10 fold change in the concentration of hydrogen ions (H+). The pH scale is a negative logarithm of the hydrogen ion concentration in moles per liter. So for a solution that has a pH of 3, the H+ concentration is 10-3 M. For a solution of pH 7, the H+ concentration is 10-7 M, which means that the H+ concentration is 10 X 10 X 10 X 10, or 10,000 times lower than the pH 3 solution.

Which pH is more acidic, a pH of 3, a pH of 7, or a pH of 9? A) pH of 9 B) pH of 3 C) pH of 7

B) pH of 4 Yes, the lower the pH, the more acidic the fluid. pH is inversely related to the number of H+ ions. As the number of H+ ions increases (and thus the acidity increases), the pH decreases. Therefore, a pH of 4 is the most acidic of the three values given. The pH scale runs from 0 to 14 and is logarithmic. This means that each change of pH unit represents a 10 fold change in the concentration of hydrogen ions (H+). The pH scale is a negative logarithm of the hydrogen ion concentration in moles per liter. So for a solution that has a pH of 4, the H+ concentration is 10-4 M. For a solution of pH 7, the H+ concentration is 10-7 M, which means that the H+ concentration is 10 X 10 X 10, or 1,000 times lower than the pH 4 solution.

Which pH is more acidic, a pH of 4, a pH of 7, or a pH of 9? A) pH of 9 B) pH of 4 C) pH of 7

C) plasma membrane Because of its semipermeable nature, the plasma membrane is most important in maintaining cellular homeostasis. The plasma membrane allows beneficial substances to enter and remain in the cell, while preventing unwanted substances from entering and allows for the elimination of wastes.

Which part of the cell is most important for maintaining the homeostasis of the intracellular environment? A) nucleus B) cytoplasm C) plasma membrane

B) phosphate heads The phosphate heads of the phospholipid molecule are polar (charged) and are therefore hydrophilic. The polar phosphate heads are attracted to the watery fluids of the intracellular and extracellular compartments so they lie on both the inner and outer surfaces of the membrane. The uncharged, nonpolar fatty acid tails of the phospholipid molecule face inward and form the hydrophobic middle portion of the bilayer.

Which part of the phospholipid bilayer of the cell membrane is hydrophilic? A) fatty acid tails B) phosphate heads C) middle layer

B) valence electrons Only the outermost parts of atoms interact (react) with each other, and those are the valence electrons. If the outermost orbital is full, the atom is stable and is less likely to react with another atom.

Which parts of atoms can interact (react) to form chemical bonds? A) the orbitals B) valence electrons C) protons D) the nucleus of each atom

D Panel D shows recognition of one cell by another via the glycocalyx. Notice that there are two complete lipid bilayers, which suggests that there are two cell membranes, and therefore two cells.

Which set of membrane proteins in the figure depicts an interaction between two separate cells? A B C D

A Panel A shows both passive and active transport processes of solutes mediated by integral membrane proteins.

Which set of membrane proteins in the figure depicts the transport of solute molecules across the membrane? A B C D

D) protons and neutrons In a typical atom, the protons and neutrons "hang out" together in the center of the atom—the nucleus. Electrons are always found orbiting around the nucleus.

Which type(s) of subatomic particles can be located within the nucleus of an atom? A) protons and electrons B) neutrons only C) electrons only D) protons and neutrons