All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Questions
Example Question #1 : Help With Lysosome Function
What are acid hydrolases?
Proteins designed to break apart acids using water
Proteins commonly found in lysosomes and designed to function at low pH
Protein designed to create acids
Proteins that break apart molecules using acid catalysts
Proteins commonly found in lysosomes and designed to function at low pH
Acid hydrolases are proteins that are specifically designed to function at acidic pH, particularly at levels that would typically denature other proteins. They are commonly found in lysosomes where they aid in the digestion of various cellular wastes and materials.
Though acid hydrolases use water to break apart molecules, acids are not used as reactants, products, or catalysts in these reactions.
Example Question #2 : Help With Lysosome Function
Which of the following organelles has an acidic internal pH?
Nucleus
Mitochondria
Golgi apparatus
Lysosomes
Lysosomes
An acidic environment is not suitable for the cell as a whole, so the low pH is sequestered in a specific organelle: the lysosome. This low pH in the lysosome activates the hydrolytic enzymes in the lysosome, and allows them to degrade macromolecules that enter the organelle.
Example Question #2 : Lysosomes
Which cell organelle is tasked with collecting and recycling cytoplasmic debris?
Endoplasmic reticulum
Mitochondria
Ribosomes
Lysosome
Nucleus
Lysosome
A lysosome is a cell organelle that is part of the intracellular digestive system. Inside its limiting membrane there are hydrolytic enzymes capable of breaking down proteins and carbohydrates. Lysosomal enzymes contribute to the digestion of pathogens phagocytosed by a cell, and also to the tissue damage that accompanies inflammation. In short, they swallow up dead cells and debris, breaking down these compounds and recycling their components.
The mitochondria are frequently referred to as "powerhouses" because they are the site of the reactions of anabolic metabolism and most ATP synthesis. The nucleus is considered the "brain" of the cell because it controls the cell and contains the cell's genetic material. The ribosomes and endoplasmic reticulum are the sites of protein synthesis; smooth endoplasmic reticulum also synthesizes lipids and digests toxins.
Example Question #3 : Lysosomes
Which of the following is not a function of the lysosome within the cell?
Contain an acidic, aqueous lumen for efficient destruction of components.
Degradation of cellular components that have become too old to function properly.
Degradation of RNA and DNA into monomeric subunits to be recycled.
Uptake of organelles through autophagy.
Detoxification of ethanol through oxidation reactions.
Detoxification of ethanol through oxidation reactions.
The lysosome can be considered the "garbage man" of the cell. Old cellular parts that are no longer very useful to the cell are taken up by lysosomes and broken down into more fundamental molecules. Each of the functions listed above has been associated with the lysosome, except for the detoxification of ethanol, which is a specific function of the peroxisome.
Example Question #61 : Cell Biology
Which of the following is true regarding muscle cell specialization?
I. Contraction is controlled by the presence or absence of calcium ions
II. Actin filaments are known as the "thick" filaments
III. Contraction is an ATP-independent process
IV. The basic functional unit of muscle contraction is called the sarcoplasmic reticulum
I only
II and III
II, III, and IV
I, III, and IV
I only
The only statement that is true of those presented is that muscle contraction is controlled by the release of calcium ions. Calcium ions expose the myosin binding sites on actin filaments by causing the protein troponin to move out of the way. Static interaction between troponin, tropomyosin, and the actin binding sites prevents involuntary contraction of skeletal muscle, only allowing contraction during stimulation and subsequent calcium release.
Actin is known as the "thin" filament and myosin is known as the "thick" filament. The contraction process is highly dependent on ATP, and without it contraction will not occur. The basic unit of contraction is the sarcomere; the sarcoplasmic reticulum houses the calcium ions that will be released when stimulated by the appropriate neural pathways.
Example Question #2 : Help With Muscle Specialization
Which of the following statements about cardiac muscle is not true?
Cardiac muscle has sarcomeres which contribute to its striated appearance.
There are significantly more T-tubules in cardiac muscle as compared to skeletal muscle
Cardiac muscle contraction requires extracellular calcium ions
The primary structural components of cardiac muscle are actin and myosin
Cardiac contractions are involuntary
There are significantly more T-tubules in cardiac muscle as compared to skeletal muscle
Skeletal muscle has more t-tubules than cardiac muscle. Cardiac muscle does have larger T-tubules than skeletal, but not as many. All the other statements regarding cardiac muscle are true.
Example Question #62 : Cellular Structures And Functions
Neurons transmit signals via transmission of an electrical signal called an action potential. Which integral membrane protein is crucial for the rising phase of an action potential?
Ligand gated sodium channels
Voltage-gated sodium channels
Voltage-gated potassium channels
Ligand gated calcium channels
Metabotropic glutamate receptors
Voltage-gated sodium channels
Voltage gated sodium channels allow the influx of sodium to quickly depolarize the neuron and generate the action potential. They are voltage gated, meaning they open in response to changes in membrane potential, thus providing the positive feedback required to get such a dramatic change in membrane potential once threshold has been reached. The other channels listed are not involved with the rising phase of the action potential.
Example Question #63 : Cellular Structures And Functions
In synaptic transmission, the __________ of the pre-synaptic cell can make either a chemical or electrical synapse with a __________ of the post-synaptic cell.
axon . . . nucleus
spine . . . dendrite
dendrite . . . axon
axon . . . dendrite
soma . . . dendrite
axon . . . dendrite
Of all the choices, axon and dendrite are the best answers to fill in the blanks because the axon is typically the pre-synaptic structure and the dendrite is the post-synaptic structure. In each of the other selections at least one of the choices does not make sense as a post/pre synaptic structure, or has nothing to do with synaptic transmission.
Example Question #1 : Signals, Communication, And Junctions
Adherens junctions are specialized cell junctions that form by linking the __________ to transmembrane proteins known as __________.
microtubule cytoskeleton . . . cadherins
actin cytoskeleton . . . cadherins
microtubule cytoskeleton . . . integrins
intermediate filament cytoskeleton . . . integrins
actin cytoskeleton . . . cadherins
Adherens junctions are formed by linking the actin cytoskeleton to transmembrane proteins known as cadherins. Cadherins are capable of interacting with other cadherins from neighboring cells on the exoplasmic face of the cell membrane. This interaction forms a physical link essentially connecting the actin cytoskeletons of the two adjacent cells, thus promoting force transduction.
Desmosomes are another type of cell junction that link the intermediate filaments of the cytoskeleton to cadherins.
Example Question #1 : Cellular Junctions
Which of the following cell junctions is involved with anchoring the extracellular matrix to the cell?
I. Adherens junctions
II. Desmosomes
III. Hemidesmosomes
IV. Gap junctions
III and IV
I, II, III, and IV
I and III
I, II, and III
I and III
Of the choices, only adherens junctions and hemidesmosomes are responsible for anchoring the extracellular matrix. This is accomplished by associating the actin cytoskeleton (for adherens junctions) or the intermediate filament cytoskeleton (for hemidesmosomes) with transmembrane proteins known as integrins. Integrins interact with the extracellular matrix.
Desmosomes are responsible for anchoring adjacent cells to one another by connecting their intermediate filament cytoskeletons with cadherins. Gap junctions connect the cytoplasm of adjacent cells and allow the free flow of small molecules between them.