1.
The function of a cell membrane is to .................... what enters and leaves a cell
Explanation
The cell membrane acts as a barrier that controls the movement of substances in and out of the cell. It regulates the entry and exit of molecules, ions, and other substances, allowing only specific materials to pass through while preventing the passage of others. This selective control is crucial for maintaining the internal environment of the cell and ensuring proper functioning.
2.
Membranes are made up of two layers of what?
Correct Answer
D. Phospholipids
Explanation
Membranes are composed of two layers of phospholipids. Phospholipids are a type of lipid that have a hydrophilic (water-loving) head and a hydrophobic (water-repelling) tail. In a membrane, the hydrophilic heads face outward towards the watery environment, while the hydrophobic tails are sandwiched in between, creating a barrier. This arrangement allows membranes to selectively control the movement of substances in and out of cells, making phospholipids a crucial component of cell membranes.
3.
The cell membrane is primarily composed of a bilayer of ______, which have a hydrophilic head and a hydrophobic tail.
Correct Answer
phospholipids, Phospholipids
Explanation
Phospholipids are a type of lipid molecule that forms the structural basis of the cell membrane. Their unique structure, with a water-loving (hydrophilic) head and a water-fearing (hydrophobic) tail, allows them to spontaneously arrange into a bilayer, creating a barrier that separates the cell's internal environment from the external environment.
4.
Hydrocarbon tails of phospholipids are said to be what?
Correct Answer
hydrophobic
Explanation
The hydrocarbon tails of phospholipids are hydrophobic, meaning they repel or do not mix well with water. This is because hydrocarbon chains are nonpolar and do not have any charged or polar groups that can interact with water molecules. Instead, they prefer to interact with other nonpolar molecules, such as other hydrocarbon chains, and form stable, lipid bilayers in aqueous environments.
5.
What model was proposed for the cell membrane?
Correct Answer
C. Fluid mosaic
Explanation
The correct answer is "fluid mosaic." This model was proposed for the cell membrane to describe its structure and behavior. According to this model, the cell membrane is composed of a fluid lipid bilayer in which various proteins are embedded, creating a mosaic-like pattern. The fluidity of the lipid bilayer allows for the movement of molecules and proteins within the membrane, while the mosaic arrangement emphasizes the diverse composition and organization of proteins.
6.
Intrinsic proteins span how far into the membrane?
Correct Answer
A. Width
Explanation
Intrinsic proteins span the width of the membrane.
7.
Extrinsic proteins span how far into the membrane?
Correct Answer(s)
D. Outer side
E. Inner side
Explanation
Extrinsic proteins are located on the outer and inner sides of the cell membrane. They span across the lipid bilayer to varying depths, with parts of the protein extending into the outer side of the membrane and other parts extending into the inner side. This allows extrinsic proteins to interact with both the external environment and the cytoplasmic side of the cell, playing important roles in cell signaling, transportation of molecules, and maintaining the structure of the membrane.
8.
Cell membranes have the following functions
Correct Answer(s)
A. Controlling the passage of materials in and out of cells
B. Recognition of other cells
C. Receptor sites for hormones and neurotransmitters
D. Transmission of nerve impulses
E. Insulation of nevers
Explanation
Cell membranes have multiple functions, including controlling the passage of materials in and out of cells, recognizing other cells, providing receptor sites for hormones and neurotransmitters, transmitting nerve impulses, and providing insulation for nerves. The cell membrane acts as a barrier, selectively allowing certain substances to enter or exit the cell. It also plays a crucial role in cell-cell communication and recognition, allowing cells to interact with each other. Additionally, the membrane contains receptor sites that bind to specific molecules, such as hormones and neurotransmitters, enabling cellular responses. Furthermore, the membrane is involved in transmitting nerve impulses, allowing for communication between different parts of the body. Lastly, the insulation provided by the cell membrane helps to protect and maintain the integrity of nerve cells.
9.
Molecules can move across membranes by?
Correct Answer(s)
Diffusion, Facilitated diffusion, Osmosis, Active transport, Bulk transport
Explanation
Molecules can move across membranes through various processes. Diffusion refers to the movement of molecules from an area of high concentration to an area of low concentration. Facilitated diffusion involves the assistance of specific transport proteins to move molecules across the membrane. Osmosis is the movement of water molecules across a membrane from an area of low solute concentration to an area of high solute concentration. Active transport requires the use of energy to move molecules against their concentration gradient. Bulk transport involves the transportation of large molecules or particles through the membrane via endocytosis or exocytosis.
10.
Diffusion occurs ................... no ATP
Correct Answer(s)
passively
Explanation
Diffusion is a process where molecules move from an area of higher concentration to an area of lower concentration. It does not require the input of energy, such as ATP, to occur. Therefore, the correct answer is "passively."
11.
Osmosis is the;
Correct Answer
B. Net movement of water across a ppm from an area of high concentration to an area of low concentration
Explanation
Osmosis is the net movement of water across a permeable membrane (ppm) from an area of high concentration to an area of low concentration. This means that water molecules move from an area where there is a higher concentration of solute (such as salt or sugar) to an area where there is a lower concentration of solute. This process occurs to equalize the concentration of solute on both sides of the membrane.
12.
Changes shape to help move molecules through the membrane
Correct Answer
Carrier protein
Explanation
Carrier proteins are integral membrane proteins that play a crucial role in facilitating the transport of molecules across the cell membrane. They bind to specific molecules on one side of the membrane and undergo conformational changes, which allows them to carry the molecules across the membrane and release them on the other side. This conformational change in shape helps the carrier protein to move the molecules through the membrane, making it the correct answer.
13.
Forms tunnels in the membrane for water soluble molecules to move through
Correct Answer
Explanation
This statement describes the function of channel proteins in the cell membrane. Channel proteins form tunnels or pores in the membrane that allow water soluble molecules to pass through. These channels provide a selective pathway for the movement of specific molecules, such as ions or small polar molecules, across the hydrophobic lipid bilayer of the membrane. This facilitates the transport of essential nutrients, ions, and signaling molecules into and out of the cell, maintaining cellular homeostasis and allowing for proper cell function.
14.
Active transport does the following
Correct Answer(s)
A. Uses ATP
C. Moves substances against a concentration gradient
Explanation
Active transport is a process that requires energy in the form of ATP to move substances across a cell membrane. Unlike passive processes, such as diffusion or facilitated diffusion, active transport moves substances against their concentration gradient, from an area of lower concentration to an area of higher concentration. This allows the cell to maintain or establish concentration gradients that are necessary for various cellular functions. Therefore, the correct answer is that active transport uses ATP and moves substances against a concentration gradient.
15.
Two forms of bulk transport are?
Correct Answer(s)
B. Endocytosis
D. Exocytosis
Explanation
Endocytosis and exocytosis are two forms of bulk transport. Endocytosis is the process by which cells take in materials by engulfing them with their cell membrane, forming a vesicle inside the cell. Exocytosis, on the other hand, is the process by which cells release materials from vesicles to the outside of the cell. These two processes play important roles in the transportation of substances into and out of cells, allowing for the uptake of nutrients and the secretion of waste or signaling molecules.