Biology Learning Catalytics

An atom with _______ has an atomic mass of 14.

7 neutrons and 7 protons

Select the statement about elements that is false.

A. An element contains only one kind of atom.
B. Carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur are the main elements found in living organisms.
C. Atoms of different elements can have the same number of protons.
D. Isotopes are variants of an element with additional neutrons in the nucleus.

C. Atoms of different elements can have the same number of protons.

What determines if a molecule is polar or nonpolar?

The differences in the electronegativities of the atoms

Which statement about water is false?

A. Water helps to prevent dramatic changes in body temperature because it has a high heat capacity.
B. Sweating cools the body because water has a high heat of vaporization.
C. bonds give water adhesion to the solid surface and help the plant overcome gravity in transporting water.
D. During a condensation reaction, the addition of water breaks a polymer into monomers.
E. Water molecules resist coming apart when placed under tension because hydrogen bonds give water cohesive strength.

D. During a condensation reaction, the addition of water breaks a polymer into monomers.

Molecules containing a large number of hydroxyl groups are

Soluble in water

Which of the following statements about an endergonic condensation reaction is true?

A. The reaction releases free energy.
B. The reaction requires the input of free energy.
C. The free energy of products is equal to the free energy of reactants.
D. The total amount of energy that are released is called the activation energy (Ea).
E. The reaction is a hydrolysis reaction and ΔG is negative.

B. The reaction requires the input of free energy.

Which statement(s) about lipids is(are) correct?

A. insoluble in water because of many nonpolar covalent bonds
B. They are a major component of cell membranes.
C. They store energy in C-O bonds.
D. Both a and b are correct.
E. All statements are correct.

D. Both a and b are correct.

Fats have higher melting temperature than oils because

fats contain more saturated fatty acids than oils

Starch and glycogen, which are both polysaccharides, differ structurally in that glycogen _______, whereas starch _______.

is highly branched; is moderately branched

Starch and glycogen, which are both polysaccharides, differ functionally in that glycogen _______, whereas starch _______.

is the main energy storage of animals; is the principle energy storage compound of plants

Which statement about phospholipids is false?

A. A phospholipid has two fatty acids, whereas a triglyceride has three fatty acids.
B. Phospholipids are amphipathic (i.e., they have two opposing chemical properties).
C. The phosphate functional group and glycerol form the hydrophobic head of a phospholipid.
D. The fatty acid chains form the tail of a phospholipid.
E. Biological membranes are characterized by a phospholipid bilayer structure.

C. The phosphate functional group and glycerol form the hydrophobic head of a phospholipid.

Nucleotides in DNA (or RNA) are connected to one another in the polynucleotide chain by

covalent bonds between sugar and phosphate.

In the double-stranded DNA molecule, base pairs are always between a purine base in one strand and a pyrimidine base in another strand, i.e. either A-T or G-C base pairing. Complementary base pairing between two strands are linked by __________.

hydrogen bonds

Consider the double-stranded DNA:
5'-TGCCATACGT-3'
3'-ACGGTATGCA-5'
If the lower strand is transcribed, which strand will result?

5'-UGCCAUACGU-3'

Consider the double-stranded DNA:
5'-AGCCAT-3'
3'-TCGGTA-5'
Which of the following sequence is the complementary DNA strand of 5'-AGCCAT-3' (the upper strand)?

5'-ATGGCT-3'

Which of the following sequence is the complementary DNA strand of 5'-ATTGCTAG-3' ?

5'-CTAGCAAT-3'

Which amino acid substitution for valine would least likely affect the three-dimensional shape of the resulting protein?

Isoleucine

Which amino acid is positively charged under physiological pH?

Lysine

Enzymes are proteins. Enzymes are highly sensitive to pH and temperature because

of their three-dimensional structure and side chains

In the biosynthetic pathway for folic acid, the compound PABA is the normal substrate for an enzyme in the pathway. The antibiotic sulfanilamide is very similar in structure to PABA and will act as a(n) _______ that competes with the substrate for active site on the enzyme.

Competitive inhibitor

A noncompetitive inhibitor of an enzyme-catalyzed reaction

binds to an allosteric site of enzyme and changes the shape of the active site.

Which type of membrane protein would likely be most easily removed in a laboratory experiment?

Peripheral proteins

A red blood cell with a 1% NaCl concentration is moved to a solution with 0.1% NaCl concentration. What will happen to the red blood cell in this new solution?

Water will move into the red blood cell, causing it to swell (and burst)

Ca+, a crucial ion for plant cell-to-cell signalling, moves across the membrane via facilitated diffusion. This requires:

a concentration gradient and a membrane protein only

Which of the following is a common feature of three types of endocytosis (phagocytosis, pinocytosis and receptor-mediated endocytosis)?

invagination (folding back) of the plasma membrane.

The diffusion of water across membranes (osmosis) relies on special membrane channels (aquaporins) and does not require energy from ATP. Therefore, osmosis is a

facilitated diffusion.

Active transport usually moves molecules

in a direction opposite to the one in which diffusion moves them.

Cilia and eukaryotic flagella

must have a motor protein that uses the energy of ATP hydrolysis to power the microtubule movement

Microfilaments are composed of monomers of

actin

The presence of _______ means that substances must pass through, rather than between, the epithelial cells that form the lining of the small intestine.

tight junctions

The electric signal for a contraction passes rapidly from one heart muscle cell to the next by way of

gap junctions.

Which of the following is NOT a feature of nucleus?

A. Nucleus contains most of the cell's DNA.
B. Nucleus is the site of DNA replication and RNA transcription.
C. Nuclear envelope has two membranes.
D. Nuclear pores regulate movement of substances.
E. Nucleus has many attached ribosomes where proteins are synthesized.

E. Nucleus has many attached ribosomes where proteins are synthesized.

In the Golgi, the proteins are further modified by the attachment of ________, which act as signals that direct the proteins to the correct location of the cell.

carbohydrate

The endomembrane system includes ______ and ________.

the endoplasmic reticulum and the Golgi apparatus

Which statement about the cells is false?

A. Plant cells have cell wall
B. Both animal and plant cells have large vacuoles
C. All the cells have plasma membrane (cell membrane).
D. Both animal and plant cell mitochondria have DNA
E. All the cells have cytoplasm.

B. Both animal and plant cells have large vacuoles

Which of the following cellular components is involved in energy conversions? (plants)

Chloroplast

What signals travel to distant cells?

Hormones

Caffeine is similar to the ligand ________, which causes drowsiness. Caffeine binds to receptors in the brain, preventing their binding by the ligand.

adenosine

Acetylcholine receptors are:

ligated-gated ion channel receptors

When the ligand binds the GPCR, the α subunit of G protein changes its binding molecule from ________ to ________, which activates an enzyme that initiates cellular responses.

GDP; GTP

Which of the following is/are allosteric regulation?

A.Ligand binding causes a protein kinase receptor to change its 3D shape and activate the enzyme (kinase).
B. Phosphorylation of an enzyme changes its conformation.
C. A noncompetitive inhibitor binds at a site distinct from the active site, causing change in shape and function.
D. All of above

D. All of above (no the???)

How does a protein kinase cascade amplify an intercellular signal?

One activated receptor kinase molecule can trigger the activation of thousands of proteins.

Second messenger is a small nonprotein molecule. What is the second messenger in the pathway stimulated by epinephrine in liver cells?

cyclic AMP (cAMP)

Which of the following would likely NOT be observed in a person injected with epinephrine?

A. Inactivation of glycogen synthase
B. Increased glucose concentration
C. Activation of G proteins
D. Activation of phosphorylase kinase
E. Decreased production of cAMP in liver cells

E. Decreased production of cAMP in liver cells

________ remove phosphate groups from target proteins, thus reversing phosphorylation.

Phosphatases

Which of the following processes represents integration of signaling pathways?

In the regulation of blood glucose levels, epinephrine, glucagon and insulin pathways can converge to the same target: cAMP.

An oxidative step is normally coupled to

the reduction of a molecule.

When NADH donates two electrons to ubiquinone during respiration, ubiquinone is

reduced

Chemiosmosis converts potential energy of ________ across a membrane into the chemical energy in ________.

a proton (H+) gradient; ATP

Glycolysis

A. takes place in the cytosol
B. takes place in the mitochondrion
C. produces 2 molecules of ATP per one molecule of glucose
D. reduces 2 molecules of NAD+ per one molecule of glucose
E. A, C and D

E. A, C and D

The chemiosmotic generation of ATP is driven by

the protein gradient.

Most of the free energy produced during the citric acid cycle is

used to reduce electron carriers.

The generation of a proton (H+) gradient across the mitochondrial inner membrane ________ energy that is provided by ________.

requires; oxidation-reduction reactions

What is the function of oxygen at the end of the electron transport chain?

the oxidizing agent and the final electron acceptor

In the absence of oxygen, cells capable of fermentation

oxidize NADH to produce NAD+.

Which of the following will NOT occur without oxygen?

A. glycolysis
B. lactic acid fermentation
C. alcoholic fermentation
D. oxidative phosphorylation

D. oxidative phosphorylation

The wavelength of X rays is shorter than the wavelength of infrared rays. Which of the following is true?

A. X rays have more energy per unit than infrared rays have.
B. X rays have less energy per unit than infrared rays have.
C. X rays and infrared waves have the same frequency.
D. Infrared waves are in the ground state, whereas X rays are in the excited state.

A. X rays have more energy per unit than infrared rays have.

When ________ gives the excited electron to an acceptor and becomes ________, light energy is converted to chemical energy.

chlorophyll; oxidized

During the Calvin cycle, the energy in ________ and ________ is used to fix CO2 and synthesize carbohydrates.

NADPH; ATP

The Calvin cycle requires ______ to produce glucose.

A. CO2
B. Rubisco
C. ATP
D. NADPH
E. All of the above

E. All of the above