Cell Biology: Plasma Membrane Quiz

The outer boundary of a cell, also known as the plasmalemma. It's essential for maintaining the cell's integrity and interacting with the environment.

The fluid mosaic model describes the structure of the plasma membrane as a flexible layer of phospholipids with embedded proteins and cholesterol. Proteins can move laterally but this movement is controlled.

Lipid rafts are small, specialized areas within the cell membrane that are enriched in certain lipids and proteins. They act as signaling platforms and play a role in cell processes.

Cholesterol is a lipid molecule that regulates the fluidity of the cell membrane. It affects the packing of phospholipids, preventing the membrane from becoming too rigid or too fluid.

Transmembrane proteins are proteins that span the entire width of the cell membrane, with parts exposed both inside and outside the cell. They facilitate transport, signaling, and cell adhesion.

Transmembrane proteins can be categorized based on their functions, which include transport, signaling, anchoring, and enzymatic activity. These roles are crucial for cell communication and survival.

The glycocalyx is a carbohydrate-rich layer that coats the outer surface of the cell membrane. It plays a role in cell recognition, adhesion, and protection.

Endocytosis is the process of bringing materials into the cell by engulfing them in a vesicle. Exocytosis is the process of releasing materials from the cell by fusing a vesicle with the plasma membrane. Transcytosis involves both endocytosis and exocytosis, transporting materials across the cell.

Movement of substances across the cell membrane without energy expenditure. Occurs down the concentration gradient.

Movement of substances across the cell membrane that requires energy. Occurs against the concentration gradient.

Type of passive transport that uses proteins to move substances across the cell membrane. Highly selective and can involve conformational changes.

Type of passive transport that uses channels to move substances across the cell membrane. Regulated by factors like voltage, neurotransmitters, or mechanical stress.

The general term for vesicular transport where substances enter the cell. Important for nutrient uptake, signaling, and cell shape.

The general term for vesicular transport where substances leave the cell. Helps deliver plasma membrane to the cell surface.

Transport of macromolecules from one side of the cell to the other, involving endocytosis, vesicular trafficking, and exocytosis.

A type of endocytosis that takes in fluid and small molecules via small vesicles.

A type of endocytosis that takes in large particles via large vesicles.

A protein that helps pinch off vesicles from the plasma membrane during micropinocytosis. Requires GTP.

The plasma membrane is a thin structure that surrounds cells, similar in architecture to the plasma membrane. It's about 8-10 nanometers thick and requires specialized microscopy (TEM) to be visualized due to its small size.

Light microscopy (LM) lacks the resolution to view the intricate details of the plasma membrane. Higher resolution microscopy techniques like Transmission Electron Microscopy (TEM) are needed.

When viewed with TEM, the plasma membrane appears as two dark layers flanking a lighter layer. This is because the electron-dense phospholipid heads of the bilayer appear darker, while the less dense hydrophobic tails appear lighter.

The plasma membrane is composed of various molecules, with phospholipids being a major component. Phospholipids are unique for their dual nature, having a hydrophilic head and a hydrophobic tail. These molecules form a bilayer with their heads facing the outside and tails facing the inside, creating a hydrophobic barrier.

Lipid rafts play crucial roles in cell signaling, lymphocyte activation, and even viral entry. The unique composition of these regions allows them to concentrate signaling molecules, making them valuable targets.

Lipid rafts play a crucial role in the entry of several viruses, including HIV. These viruses can exploit rafts to facilitate their entry into cells.

Some bacteria like Shigella and Salmonella can hijack lipid rafts. They take advantage of the signaling pathways associated with rafts to enter cells.

A type of endocytosis where the cell engulfs large particles, like bacteria or cell debris. It's a nonselective process where the plasma membrane sends out pseudopodia to engulf the particle into a phagosome. This process is crucial for immune cells, which use it to engulf pathogens and clear cellular debris.

A highly specific form of endocytosis where the cell takes in specific molecules using specialized receptors called cargo receptors. These receptors reside in specific regions of the cell membrane like lipid rafts. The process utilizes clathrin, which forms a coated pit, pulls the membrane inward, and ultimately creates a coated vesicle containing the target molecules. This is a highly regulated process, commonly seen in endocytosis of LDL.

A membrane-bound compartment found inside the cytoplasm, involved in endocytotic pathways. Early endosomes reside near the plasma membrane, while late endosomes are more deeply located and eventually mature into lysosomes. They act as sorting stations for the internalized molecules, directing them to their specific destinations.

Finger-like projections on the apical surface of cells. They contain a core of actin filaments and are abundant in absorptive cells like those in the intestines, gallbladder, and kidney tubules. They increase the surface area for absorption.

Hair-like appendages found on the apical surface of some epithelial cells, like those in the respiratory tract and the oviduct. They contain microtubules and are motile, aiding in the movement of fluids and particles.

Plasma membrane folds in absorptive cells, like those in the intestine and kidney tubules. These folds increase the surface area of the cell to enhance absorption of nutrients or other molecules.

A type of vesicle coated with the protein clathrin, which plays a role in receptor-mediated endocytosis and transport between the Golgi and other organelles. These vesicles are involved in the packaging and transport of specific molecules within the cell.

A specialized protein that functions in the formation of caveolae, small invaginations of the plasma membrane. These caveolae are involved in endocytosis, cellular signaling, and cholesterol transport.

Lipid rafts are specialized microdomains within the plasma membrane enriched in certain lipids and proteins. They are involved in various cellular processes, like signal transduction, protein sorting, and membrane trafficking.

Planar lipid rafts are flat microdomains within the plasma membrane enriched in cholesterol and sphingolipids. They often contain proteins involved in signaling pathways and membrane trafficking.

Caveolar rafts, also known as caveolae, are small, flask-shaped invaginations of the plasma membrane. They are rich in cholesterol and sphingolipids and contain the protein caveolin.

Flotillins are integral membrane proteins found in planar lipid rafts. They function in signaling pathways and recruit specific membrane proteins to the rafts.

Integral proteins are embedded within the lipid bilayer of the plasma membrane. They can be transmembrane proteins that span the entire membrane or partially lipid-anchored proteins attached to one side of the membrane.

Transmembrane proteins are integral proteins that span the entire lipid bilayer, meaning they have portions on both the inside and outside of the cell.

Single-pass transmembrane proteins cross the membrane only once. Multi-pass transmembrane proteins cross the membrane multiple times, forming loops within the membrane.

Partially lipid-anchored proteins are attached to the lipid bilayer on either the exterior or interior face of the membrane. They are held in place by a lipid group.

Peripheral proteins are not embedded within the lipid bilayer. They are located on the outer or inner surfaces of the membrane, held in place by interactions with integral proteins or phospholipid head groups.

Pumps are membrane proteins that use energy to move molecules across the membrane against their concentration gradient. They are vital for maintaining ion gradients and for transport of nutrients.

Channels are membrane proteins that create pores in the membrane, allowing the passage of small molecules like ions and water down their concentration gradient. They are important for maintaining cell volume and for signaling.

Receptors are membrane proteins that bind to specific ligands, such as hormones or neurotransmitters. They initiate cellular responses upon ligand binding, playing a crucial role in cell signaling.

Linker proteins are membrane proteins that connect the intracellular cytoskeleton to the extracellular matrix, providing structural support and enabling communication between the inside and outside of the cell.

Integrins are a class of transmembrane linker proteins that play a crucial role in cell adhesion and signaling. They bind to extracellular matrix proteins and link them to the cytoskeleton, allowing cells to interact with their environment.

Enzymes are membrane proteins that catalyze specific chemical reactions within the cell. They are involved in various metabolic processes, such as energy production, synthesis of molecules, and breakdown of substances.

Structural proteins are membrane proteins that provide shape and support to the cell and its components. They form junctions between cells and maintain the integrity of the cell membrane.