Biology: Cell Structure, Transport Mechanisms, and Exchange Surfaces

What is the fluid mosaic model?

A model describing the structure of the cell-surface membrane, where components are arranged like tiles in a mosaic.

What is diffusion?

The movement of a substance from a high concentration to a low concentration.

What is passive transport?

Transport of substances across a membrane without using energy from ATP, moving from high to low concentration.

What is facilitated diffusion?

A process where polar substances are transported across the membrane via channel or carrier proteins.

What is osmosis?

The facilitated diffusion of water from a high concentration of water molecules to a low concentration.

What is active transport?

The movement of substances from a low concentration to a high concentration using energy from ATP.

What is co-transport?

A type of facilitated diffusion where one substance is transported together with another substance.

How do small, non-polar molecules move across the cell membrane?

They can move through the phospholipid bilayer by simple diffusion.

What type of molecules cannot diffuse through the phospholipid bilayer?

Polar substances such as water, glucose, or ions.

What is the significance of the surface area to volume ratio in exchange mechanisms?

A large surface area to volume ratio is essential for efficient exchange of substances.

What happens to the rate of exchange as temperature increases?

The rate of exchange increases as the metabolic rate and demand for glucose and oxygen rise.

What is the role of channel proteins in facilitated diffusion?

Channel proteins help ions and polar molecules to diffuse across the cell membrane.

What is a partially permeable membrane?

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

What is the concentration gradient?

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

How does active transport differ from facilitated diffusion?

Active transport moves substances against the concentration gradient using energy, while facilitated diffusion moves them down the gradient without energy.

What is the role of sodium ions in glucose uptake in the small intestine?

Active transport of sodium ions creates a gradient that drives the uptake of glucose via co-transport.

What is the effect of a cube's surface area to volume ratio on the rate of exchange?

A higher surface area to volume ratio leads to a greater rate of exchange.

What is the primary function of the cell-surface membrane?

To regulate the movement of substances in and out of the cell.

What happens to glucose uptake when sodium ions are actively transported out of epithelial cells?

It creates a concentration gradient that facilitates glucose uptake through co-transport.