High School Biology : Understanding Cytoplasmic Proteins

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Understanding Cytoplasmic Proteins

In which cellular compartment does glycolysis take place?

Possible Answers:

Cytoplasm (Cytosol)

Golgi apparatus

Intermembrane space

Inner mitochondrial membrane

Mitochondrial matrix

Correct answer:

Cytoplasm (Cytosol)

Explanation:

Glycolysis (the process of breaking down glucose) takes place in the cytoplasm, or cytosol—the aqueous portion of the cytoplasm. It is in the cytoplasm where the enzymes required for glycolysis are found.

The citric acid cycle takes place in the mitochondrial matrix, and the electron transport chain takes place along the inner mitochondrial membrane in order to pump protons into the intermembrane space.

Example Question #11 : Transport And Signaling

What is the function of a kinase?

Possible Answers:

Change the structure of the ligand

Remove phosphates from ligands

Add ubiquitin to the ligand

Add phosphates to ligands

Correct answer:

Add phosphates to ligands

Explanation:

The addition and removal of phosphate groups can serve critical functions in the regulation of protein activity. The binding or uncoupling of phosphate groups frequently serves to activate or deactivate proteins.

A kinase is an enzyme that phosphorylates—or adds a phosphate group to—its ligand.

A phosphatase removes a phosphate group from its ligand.

Several different types of proteins can change the structure of a ligand, such as isomerases, and ubiquitin ligases add ubiquitin to their ligands.

Example Question #12 : Transport And Signaling

What is the function of a phosphatase?

Possible Answers:

Change the structure of its ligand

Add an ubiquitin to its ligand

Add a phosphate to its ligand

Remove a phosphate from its ligand

Correct answer:

Remove a phosphate from its ligand

Explanation:

The addition and removal of phosphate groups can serve critical functions in the regulation of protein activity. The binding or uncoupling of phosphate groups frequently serves to activate or deactivate proteins.

A phosphatase removes a phosphate group from its ligand.

A kinase is an enzyme that phosphorylates—or adds a phosphate group to—its ligand.

Several different types of proteins can change the structure of a ligand, such as isomerases, and ubiquitin ligases add ubiquitin to their ligands.

Example Question #13 : Transport And Signaling

What is the function of an ubiquitin ligase?

Possible Answers:

Add an ubiquitin to its ligand

Remove an ubiquitin from its ligand

Add a phosphate to its ligand

Remove a phosphate from its ligand

Correct answer:

Add an ubiquitin to its ligand

Explanation:

Ubiquitin ligases add ubiquitin to their ligands. The addition of ubiquitin acts as a signal that a protein has become ineffective and is ready for degradation. When multiple ubiquitin residues have been added to a protein molecule, it is transported to the lysosome in the cell to be digested.

A phosphatase removes a phosphate group from its ligand.

A kinase is an enzyme that phosphorylates—or adds a phosphate group to—its ligand.

The addition and removal of phosphate groups can serve critical functions in the regulation of protein activity. The binding or uncoupling of phosphate groups frequently serves to activate or deactivate proteins.

Several different types of proteins can change the structure of a ligand, such as isomerases.

Example Question #14 : Transport And Signaling

In regard to cellular membranes, what does it mean to be selectively permeable?

Possible Answers:

Molecules and ions can pass freely through the phospholipid bilayer

Molecules and ions are always kept to the exterior of the phospholipid bilayer

Polarization of the cell membrane allows for passive transport of all foreign molecules or ions

Molecules and ions outside the cell are selected to enter the cell via active or passive transport through the phospholipid bilayer

Polarization of the cell membrane allows for no entrance of foreign molecules or ions

Correct answer:

Molecules and ions outside the cell are selected to enter the cell via active or passive transport through the phospholipid bilayer

Explanation:

A cell must exchange molecules and ions with its surroundings.  This process is controlled by the selective permeability of the plasma membrane.  Passive transport requires no energy from the cell; molecules like water can diffuse into and out of the cell through the phospholipid bilayer freely by way of osmosis.  Other molecules and ions, like sodium, are actively transported across the phospholipid bilayer.  This requires ATP created by the cell.  Active transport moves solutes against their concentration gradients, which is why it requires energy. 

Example Question #41 : Cell Functions

Which of the following is NOT true of the cytoplasmic protein structures known as tonofibrils?

Possible Answers:

They converge at desmosomes and hemidesmosomes.

They are primarily found in endocrine tissues.

They are most typically anchored to the cytoskeleton.

They are primarily made of kertain tonofilaments.

The protein filaggrin is thought to hold them together.

Correct answer:

They are primarily found in endocrine tissues.

Explanation:

Tonofibrils are groups of keratin tonofilaments (intermediate filaments) most commonly found in the epithelial tissues, not endocrine tissues, and which play an important structural role in cell makeup.

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