Cell Biology: Organelles and Functions

Channels between plant cell walls that connect their cytoplasm, allowing transport of molecules.

Structures that allow cells to communicate and interact by direct contact.

Watertight seals between animal cells, preventing leakage.

Spot welds between animal cells, holding tissues together to withstand stretching.

Channels between animal cells allowing transport of small molecules and ions.

Platelets sticking to damaged blood vessel walls, triggered by tissue factor.

Narrowing of a blood vessel, triggered by smooth muscle cells.

Platelets producing components necessary for blood clotting, initiated by the platelets.

Specific molecules on the surface of host cells that viruses exploit to infect specific organs.

HIV targets specific white blood cells (T-helper cells and monocytes) and some cells of the central nervous system.

Hepatitis virus specifically infects liver cells.

Viruses mimic the molecules on the surface of host cells to gain entry.

Specific sites on a virus's surface interact with the immune system, causing the production of antibodies.

Antibodies are produced by the immune system to destroy or inhibit the activity of viruses.

HIV's genes encoding surface recognition sites change rapidly, making vaccine development challenging.

Changes in the viral surface markers decrease the effectiveness of the immune system in fighting the virus.

Molecules on the cell surface that allow cells to recognize each other, crucial for tissue and organ formation and immune response.

Binding sites on the cell surface that interact with specific substances, triggering changes within the cell.

Receptors activate internal processes within the cell, such as metabolic pathways, energy production, waste removal, and signal transduction.

Viruses exploit specific receptors on the cell surface to gain entry into the cell.

Describes the plasma membrane as a dynamic structure with components (phospholipids, cholesterol, proteins, carbohydrates) that can move freely.

The ability of membrane components to move laterally, crucial for membrane function, enzyme activity, and transport.

Phospholipid molecules can diffuse rapidly and laterally within the membrane.

Embedded proteins can also diffuse and move within the membrane, contributing to membrane fluidity.

The movement of water molecules across a selectively permeable membrane from an area of high water concentration to an area of low water concentration.

A substance that dissolves in a solvent to form a solution.

A substance that dissolves a solute to form a solution.

A membrane that allows certain substances to pass through while blocking others.

The relative concentration of solutes in two solutions, like the inside and outside of a cell.

A solution with a lower solute concentration than the inside of a cell.

A solution with a higher solute concentration than the inside of a cell.

A solution with the same solute concentration as the inside of a cell.

A passive process where a substance moves from a high concentration area to a low concentration area until it becomes evenly distributed.

The difference in concentration of a substance between two areas.

Diffusion is driven by the difference in concentration between two areas, causing the substance to move from high to low concentration.

The rate of diffusion is affected by the extent of the concentration gradient, the size of the molecules, and the temperature.

A greater difference in concentration leads to faster diffusion.

Smaller molecules diffuse faster.

Higher temperatures result in faster diffusion.

Diffusion can occur across the plasma membrane, allowing for the transport of small molecules like oxygen and carbon dioxide.

The rate of diffusion depends on how close the substance is to equilibrium, the molecular mass, the temperature, and the density of the solvent. Diffusion slows down as the substance gets closer to equilibrium, larger molecules diffuse slower, higher temperatures increase diffusion speed, and denser solvents slow down diffusion.

Facilitated diffusion is a type of passive transport where molecules move across a membrane with the help of transport proteins, going from a high concentration to a low concentration without using cell energy.

These proteins act as channels or carriers, assisting molecules in crossing the plasma membrane during facilitated diffusion.

Osmosis is the movement of water molecules across a semipermeable membrane from an area of high water concentration to an area of low water concentration.

Water moves across a semipermeable membrane to balance the concentration of solutes on both sides, aiming for equal solute concentrations.

Osmosis is influenced by the concentration gradient of water, the permeability of the membrane, and the pressure difference across the membrane.

Equilibrium is reached when the concentration of the substance or water is the same on both sides of the membrane, resulting in no net movement.