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Example Question #85 : Cellular Biology
Which of the following are types of endocytosis?
pinocytosis
All of these
phagocytosis
receptor-mediated endocytosis
All of these
Endocytosis is the process by which the cell takes in macromolecules by creating new vesicles from the cell's plasma membrane. Phagocytosis, pinocytosis, and receptor-mediated endocytosis are all different types of endocytosis.
Example Question #52 : Understanding The Cell Membrane
In facilitated diffusion, what occurs in the cell?
Protein pumps use energy to pump molecules, such as glucose across the cell membrane.
Osmosis occurs.
Molecules, such as glucose, move through protein channels from an area of higher concentration to lower concentration.
Molecules, such as glucose move from an area of lower concentration to an area of higher concentration.
Molecules, such as glucose, move through protein channels from an area of higher concentration to lower concentration.
In facilitated diffusion, molecules, such as glucose move through protein channels from an area of higher concentration to an area of lower concentration. It is not active transport, using energy. Movement of molecules through the cell membrane without use of a protein is known as simple diffusion; osmosis is a type of simple diffusion.
Example Question #53 : Understanding The Cell Membrane
What occurs during endocytosis?
Osmosis occurs and water moves outside the cell.
The cell secretes substances outside the cell.
The cell takes in material from outside the cell by enveloping the meterial and ingesting it.
The cell uses protein pumps to ingest substances.
The cell takes in material from outside the cell by enveloping the meterial and ingesting it.
Endocytosis occurs when the cell engulfs an external substance and takes it into the cell by the infolding of the cell membrane. Exocytosis occurs when the cell secretes a substance outside the cell.
Example Question #54 : Understanding The Cell Membrane
Glycoproteins, often found on the external side of the cell membrane for signalling purposes, are made of protein and __________.
Lipids
Carbohydrates
RNA
Proteins
Carbohydrates
The glycolipids on the outside of the cell are made of proteins and carbohydrates. Proteins result from translation from DNA to RNA, and they are modified in the Golgi apparatus to form glycoproteins. "Glyco" refers to sugars, which are carbohydrates. Lipids are fat molecules that are not often used in cell signaling, but rather as stored energy sources.
Example Question #84 : Cell Structures
What occurs during exocytosis?
Foreign substances are engulfed by cells of the immune system.
The cell receptor is activated and substances move into the cell.
Water and salts are stored in the sarcoplasmic reticulum.
The membrane of the vacuole fuses with the cell membrane, forcing the contents out of the cell.
The membrane of the vacuole fuses with the cell membrane, forcing the contents out of the cell.
In exocytosis the membrane of a vacuole surrounding some material fuses with the cell membrane, forcing the contents out of the cell wall. The substance is secreted out of the cell. The process by which foreign matter is engulfed by immune cells is phagocytosis. Water and salts are stored in the sarcoplasmic reticulum in certain cell types (muscle) but this is not exocytosis, which involves the removal/expulsion of substances from the cell into the extracellular environment.
Example Question #85 : Cell Structures
The cell membrane regulates the passage of materials into and out of the cell. Much of the material transported across the cell membrane is via membrane-bound protein molecules, but this can be accomplished through various mechanisms.
When a substance is transported across the cell membrane across the concentrations gradient (from an area of low concentration to an area of high concentration), this is referred to as __________.
diffusion
co-transport
active transport
osmosis
passive transport
active transport
In order for a material to be transported across the cell membrane, against its concentration gradient, energy is required. For example, the sodium-potassium pump hydrolyzes one molecule of ATP to pump 3 sodium ions out of the cell and 2 potassium ions into the cell. Since the potassium levels are much higher inside the cell than outside, energy is required. This is known as active transport.
Example Question #57 : Understanding The Cell Membrane
What molecules are used in eukaryotic membranes to strengthen them against osmotic stress?
Integral membrane proteins
Polysaccharides
Peripheral membrane proteins
Sterols
Phospholipids
Sterols
In eukaryotes, sterol molecules are used to strengthen the plasma membrane. These molecules are able to pack very close together forming tight strucutres.
Example Question #61 : Understanding The Cell Membrane
In a lipid bilayer, lipid molecules either move laterally within their layer or flip transversely across the membrane. Which of the movements happens more readily?
None of these
Lateral movement
Flipping
Both happen at the same rate
Neither, no movement of lipids happens
Lateral movement
In lipid bilayers, lipids molecules readily drift around laterally, they rarely flip across the membrane. Recall that the lipid bilayer can be depicted via the fluid mosaic model, as phospholipids and integral proteins are free to move laterally throughout the membrane. A flip (phospholipid from the inner leaflet to outer leaflet, or vice-versa) is thermodynamically unfavorable and does not occur as often as lateral movements.
Example Question #62 : Understanding The Cell Membrane
Which of the following is not a major function of membrane proteins?
Signal transduction
Protein chaperones
Transport
Attachment to cytoskeleton
Cell-cell recognition
Protein chaperones
Chaperons are proteins that help other proteins fold properly. There are found in the interior of the cell, usually associated with ribosomes and not the cell membrane. All other functions listed are carried out by membrane proteins.
Example Question #63 : Understanding The Cell Membrane
Which of the following molecules cannot pass through the membrane spontaneously?
Glucose
Methane
Ethane
Molecular oxygen
Pentane
Glucose
Plasma membranes are selectively permeable. Small non polar molecules like molecular oxygen and hydrocarbons can pass through the membrane while larger charged molecules like glucose cannot, unless their transport is facilitated by a membrane protein.
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