GRE Subject Test: Biochemistry, Cell, and Molecular Biology › Cell Membrane and Cell Wall
Gram positive bacteria have __________ cell wall(s) and Gram negative bacteria have __________ cell wall(s).
one . . . one
one . . . two
two . . . one
two . . . two
Gram stain is a laboratory technique used to distinguish bacteria. Gram positive and Gram negative bacteria are distinguished based on their cell walls. Gram positive bacteria have a single thick cell wall (outside its cell membrane). Upon Gram staining, these bacteria will hold the Gram stain because of their thick cell wall. The Gram negative bacteria also have only one cell wall; however, it is a lot thinner and is sandwiched between two cell membranes. The thin nature of the cell wall makes it easier for the Gram stain to leak out of the bacterial cell.
Gram positive bacteria have __________ cell wall(s) and Gram negative bacteria have __________ cell wall(s).
one . . . one
one . . . two
two . . . one
two . . . two
Gram stain is a laboratory technique used to distinguish bacteria. Gram positive and Gram negative bacteria are distinguished based on their cell walls. Gram positive bacteria have a single thick cell wall (outside its cell membrane). Upon Gram staining, these bacteria will hold the Gram stain because of their thick cell wall. The Gram negative bacteria also have only one cell wall; however, it is a lot thinner and is sandwiched between two cell membranes. The thin nature of the cell wall makes it easier for the Gram stain to leak out of the bacterial cell.
Which of the following is false with regard to the LDL-receptor?
Once bound to cargo, it enters the cell via COPII-mediated endocytosis
It is shuttled back to the cell surface after it delivers its cargo
It releases its cargo in the low pH environment of the endosome
Its cargo is low density lipoprotein
The LDL-receptor enters the cell via clathrin-mediated endocytosis, not COPII. COPII is involved in budding off of the endoplasmic reticulum.
All of the other given answer options are true.
Which of the following is false with regard to the LDL-receptor?
Once bound to cargo, it enters the cell via COPII-mediated endocytosis
It is shuttled back to the cell surface after it delivers its cargo
It releases its cargo in the low pH environment of the endosome
Its cargo is low density lipoprotein
The LDL-receptor enters the cell via clathrin-mediated endocytosis, not COPII. COPII is involved in budding off of the endoplasmic reticulum.
All of the other given answer options are true.
A researcher observes that a molecule is brought inside the cell via membrane transporters. What can the researcher conclude about this type of transport?
None of these can be concluded
Cell expends energy to transport this molecule
Cell does not expend energy to transport this molecule
The molecule is found in higher concentration outside the cell
Membrane transporters are molecules found on plasma membranes that act as gateway for several molecules that enter and exit cells. These transporters are usually specific for one or two molecules and transport them across the cell membranes. The membrane transporters can transport ions/molecules along or against the concentration gradients; therefore, membrane transporters perform both passive and active transport. Transporters that move molecules along concentration gradient carry out a special type of passive transport called facilitated diffusion whereas transporters that move against concentration gradient carry out active transport (requires energy).
The question doesn’t state whether the molecule is brought along or against its concentration gradient; therefore, the membrane transporter could be a facilitated transporter or an active transporter.
A researcher observes that a molecule is brought inside the cell via membrane transporters. What can the researcher conclude about this type of transport?
None of these can be concluded
Cell expends energy to transport this molecule
Cell does not expend energy to transport this molecule
The molecule is found in higher concentration outside the cell
Membrane transporters are molecules found on plasma membranes that act as gateway for several molecules that enter and exit cells. These transporters are usually specific for one or two molecules and transport them across the cell membranes. The membrane transporters can transport ions/molecules along or against the concentration gradients; therefore, membrane transporters perform both passive and active transport. Transporters that move molecules along concentration gradient carry out a special type of passive transport called facilitated diffusion whereas transporters that move against concentration gradient carry out active transport (requires energy).
The question doesn’t state whether the molecule is brought along or against its concentration gradient; therefore, the membrane transporter could be a facilitated transporter or an active transporter.
How are glucose monomers linked in the cellulose polymers present in a plant cell wall?
Beta (1-4) linkages
Alpha (1-4) linkages
Beta (1-6) linkages
Alpha (1-4) linkages
Beta (1-3) linkages
Cellulose is a polymer of glucose linked by beta (1-4) linkages. Humans lack the enzyme that catalyzes the cleavage of this bond; thus cellulose (dietary fiber) is indigestible and passes through the digestive system unchanged.
How are glucose monomers linked in the cellulose polymers present in a plant cell wall?
Beta (1-4) linkages
Alpha (1-4) linkages
Beta (1-6) linkages
Alpha (1-4) linkages
Beta (1-3) linkages
Cellulose is a polymer of glucose linked by beta (1-4) linkages. Humans lack the enzyme that catalyzes the cleavage of this bond; thus cellulose (dietary fiber) is indigestible and passes through the digestive system unchanged.
Which of the following transport mechanisms requires ATP hydrolysis to move a molecule against its concentration gradient?
Active transport
Passive diffusion
Cotransport
Facilitated diffusion
Secondary active transport
Secondary active transport and cotransport are the same thing, and while solutes can be moved against their concentration gradient, ATP is not used. Passive and facilitated diffusion do not require ATP either. Active transport is the only transport mechanism that uses ATP to move molecules against their concentration gradient.
Which of the following transport mechanisms requires ATP hydrolysis to move a molecule against its concentration gradient?
Active transport
Passive diffusion
Cotransport
Facilitated diffusion
Secondary active transport
Secondary active transport and cotransport are the same thing, and while solutes can be moved against their concentration gradient, ATP is not used. Passive and facilitated diffusion do not require ATP either. Active transport is the only transport mechanism that uses ATP to move molecules against their concentration gradient.