Biology Cell Membranes: Transport, Osmosis & Tonicity

What is membrane transport?

The process by which substances move across the cell membrane.

What are the two main types of membrane transport?

Passive transport and active transport.

What is passive transport?

Movement of substances across the membrane without energy input, following concentration gradients.

What is active transport?

Movement of substances against their concentration gradient, requiring energy (ATP).

What is osmosis?

The diffusion of water across a selectively permeable membrane.

What is tonicity?

The ability of a solution to affect the shape of a cell by altering its internal water volume.

What is isotonic solution?

A solution with the same solute concentration as the cell, resulting in no net water movement.

What is hypertonic solution?

A solution with a higher solute concentration than the cell, causing the cell to lose water and shrink.

What is hypotonic solution?

A solution with a lower solute concentration than the cell, leading to water influx and cell swelling.

What is facilitated diffusion?

A type of passive transport that uses transport proteins to move substances across the membrane.

What role do channel proteins play in membrane transport?

They provide passageways for specific ions or molecules to cross the membrane.

What is the sodium-potassium pump?

An example of active transport that moves sodium ions out of the cell and potassium ions into the cell.

What is endocytosis?

A process by which cells engulf substances into a pouch that becomes a vesicle.

What is exocytosis?

The process of vesicles fusing with the plasma membrane to release their contents outside the cell.

What is the significance of the fluid mosaic model?

It describes the structure of cell membranes as flexible and composed of various proteins and lipids.

How does temperature affect membrane transport?

Higher temperatures generally increase the rate of diffusion and membrane fluidity.

What is the role of cholesterol in the cell membrane?

Cholesterol helps to stabilize membrane fluidity and integrity.

What is the concentration gradient?

The difference in the concentration of a substance across a space, driving diffusion.

What is osmotic pressure?

The pressure required to prevent the flow of water across a semipermeable membrane due to osmosis.

What are isotonic solutions?

Solutions with equal solute concentration inside and outside the cell, resulting in no net water movement.

What are hypotonic solutions?

Solutions with a lower solute concentration outside the cell, causing water to enter the cell and potentially leading to cell swelling or bursting.

What are hypertonic solutions?

Solutions with a higher solute concentration outside the cell, causing water to leave the cell and potentially leading to cell shrinkage.

What is an example of a substance transported by facilitated diffusion?

Glucose, which requires a transport protein to cross the membrane.

What is the significance of membrane fluidity?

Fluidity allows for the movement of proteins and lipids within the membrane, facilitating transport and communication.

What is the role of cholesterol in the plasma membrane?

Cholesterol helps to stabilize membrane fluidity, making it less permeable to very small water-soluble molecules that might otherwise pass freely through.

What is a concentration gradient?

A difference in the concentration of a substance across a space, which drives diffusion.

What is the difference between simple diffusion and facilitated diffusion?

Simple diffusion occurs directly through the membrane, while facilitated diffusion requires specific transport proteins.

What role do transport proteins play in membrane transport?

They facilitate the movement of substances across the membrane, especially for polar and charged molecules.

How does temperature affect membrane fluidity?

Higher temperatures increase fluidity, while lower temperatures decrease fluidity.

What is the fluid mosaic model?

A model describing the structure of the plasma membrane as a mosaic of various components that move fluidly.

Why is membrane fluidity important?

It allows for proper functioning of membrane proteins and the movement of materials in and out of the cell.

What is the significance of cholesterol in the membrane?

Cholesterol helps to stabilize membrane fluidity across varying temperatures.

What is the primary difference between passive and active transport?

Passive transport moves substances down their concentration gradient without energy, while active transport moves substances against their gradient using energy (ATP).

What are the types of passive transport?

Simple diffusion, facilitated diffusion, and osmosis.

What role do channel proteins play in transport?

Channel proteins form passages through the membrane that allow specific molecules or ions to pass through.

What is the function of carrier proteins?

Carrier proteins bind to specific substances and change shape to transport them across the membrane.

What happens to a cell in a hypertonic solution?

The cell loses water and shrinks due to the higher solute concentration outside the cell.

What happens to a cell in a hypotonic solution?

The cell gains water and may swell or burst due to the lower solute concentration outside the cell.

What is an example of primary active transport?

The sodium-potassium pump, which moves sodium ions out of the cell and potassium ions into the cell against their concentration gradients.

What is secondary active transport?

Transport that uses the energy from the gradient created by primary active transport to move other substances against their gradients.

What is the main purpose of active transport?

To build and maintain concentration gradients across the cell membrane.

What is the difference between channel proteins and carrier proteins?

Channel proteins form open passages for molecules to flow through, while carrier proteins bind to substances and change shape to transport them.

What is the significance of concentration gradients in cellular processes?

Concentration gradients are crucial for processes such as nutrient uptake, electrical signaling, and waste removal.

What is the typical rate pattern for channel proteins?

Channel proteins can show approximately linear kinetics when moving substances down the gradient.

What is a key characteristic of carrier proteins?

Carrier proteins exhibit saturable kinetics, meaning they can become occupied and cannot transport indefinitely faster.

What is the role of ATP in active transport?

ATP provides the energy required for active transport mechanisms to move substances against their concentration gradients.

What is an example of a molecule that can cross the membrane via simple diffusion?

Oxygen or carbon dioxide.

What is the difference between isotonic, hypertonic, and hypotonic solutions?

Isotonic solutions have equal solute concentrations, hypertonic solutions have higher solute concentrations outside the cell, and hypotonic solutions have lower solute concentrations outside the cell.

What is the significance of membrane permeability?

Membrane permeability determines which substances can cross the membrane and affects the cell's internal environment.

What is a gated channel protein?

A channel protein that opens or closes in response to a signal, allowing or preventing the passage of specific ions or molecules.

What is the relationship between facilitated diffusion and membrane permeability?

Facilitated diffusion relies on the presence of specific transport proteins that increase membrane permeability for certain molecules.

What is the importance of the sodium-potassium pump?

It maintains the electrochemical gradient essential for nerve impulse transmission and muscle contraction.

What is the effect of a cell in an isotonic solution?

The cell remains the same size as the solute concentration is equal inside and outside the cell.

What direction does water move during osmosis?

Water moves toward the side with higher solute concentration when solutes cannot freely cross the membrane.

What is solute potential?

Describes the effect of solutes on water potential; becomes more negative as solute concentration increases.

What happens in an isotonic solution?

No net movement of water; solute concentration is equal inside and outside the cell.

What is the effect of a hypotonic solution on a cell?

Water enters the cell, causing it to swell and potentially burst (lysis).

What occurs in a hypertonic solution?

Water leaves the cell, leading to cell shrinkage.

What is the relationship between solute concentration and water concentration?

More dissolved solute generally means less free water.

What is a symporter?

A carrier that transports two substances in the same direction across a membrane.

What is an antiporter?

A carrier that transports two substances in opposite directions across a membrane.

What increases membrane fluidity?

More unsaturated and shorter fatty acid chains reduce tight packing.

What prevents excessive fluidity at high temperatures?

Cholesterol and more saturated or longer fatty acid chains limit phospholipid movement.

What is the blood-brain barrier (BBB)?

A specialized barrier that restricts many substances from entering brain tissue.

What is the medical challenge associated with the BBB?

Many medicines cannot readily cross the BBB, complicating treatment.

What is the significance of osmotic disruption of the BBB?

It can temporarily create space for substances to pass but must be carefully controlled.

What is the role of aquaporins?

Proteins that facilitate the movement of water across cell membranes.

What is the main difference between osmosis and simple diffusion?

Osmosis specifically refers to the movement of water, while simple diffusion involves permeable molecules.

Why are cells usually small?

To maintain a high surface-area-to-volume ratio for efficient exchange.

What is the net water movement in an isotonic solution?

There is no net movement; water molecules continue to move in both directions.

What is the primary function of the Golgi apparatus?

To sort and package proteins for secretion or delivery to other organelles.

What is the role of the rough endoplasmic reticulum (Rough ER)?

To synthesize proteins that are secreted or incorporated into membranes.

What is the significance of the nucleolus?

It assembles ribosomal subunits within the nucleus.

What is the function of lysosomes?

To digest cellular materials using digestive enzymes.

What is the primary characteristic of prokaryotic cells?

They lack a nucleus and have their DNA located in the nucleoid region.

What is the main difference between facilitated diffusion and active transport?

Facilitated diffusion does not require ATP, while active transport does.

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