Transport Mechanisms and Osmosis in Cell Membranes

These flashcards cover key concepts about transport mechanisms across cell membranes, focusing on passive and active transport, osmosis, and related biological processes.

What is the role of membranes in biological systems?

Membranes are selectively permeable, allowing certain molecules to cross while restricting others.

What are the three types of transport mechanisms across a cell membrane?

Passive transport, active transport, and bulk transport.

Define passive transport.

The movement of molecules across a membrane without the use of energy, following the concentration gradient.

What defines active transport?

The movement of molecules against their concentration gradient, requiring energy in the form of ATP.

What distinguishes osmosis from other forms of transport?

Osmosis specifically refers to the passive transport of water molecules across a selectively permeable membrane.

Why can some molecules freely cross the cell membrane while others cannot?

It depends on the polarity and size of the molecules compared to the phospholipid bilayer.

What is the function of aquaporins in membranes?

Aquaporins are transporter proteins that facilitate the rapid transport of water across a cell membrane.

What is meant by the term 'selectively permeable'?

Selectively permeable means that a membrane allows certain substances to pass while blocking others.

What occurs during phagocytosis?

Phagocytosis is the process where a cell engulfs large particles or bacteria.

What can excessive water intake lead to?

Excessive water intake can lead to hyponatremia, a dangerous dilution of sodium in the blood.

What characterizes a solution as hypertonic?

A hypertonic solution has a higher concentration of solute compared to another solution.

What are endocrine disruptors, and give an example.

Chemicals that can interfere with endocrine (or hormonal) systems; an example is atrazine, a widely used herbicide.

How do ions typically cross a cell membrane?

Ions cannot cross freely and instead require specific ion channels or transport proteins for movement.

What could happen if glucose transporter proteins were absent in cells?

Without glucose transporter proteins, glucose would not enter cells, leading to high blood sugar (hyperglycemia).

What is the impact of 'like dissolves like' in membrane permeability?

This principle means that non-polar (hydrophobic) molecules can pass through the non-polar core of membranes, while polar molecules cannot.

How does the structure of a phospholipid bilayer affect solute transport?

The hydrophobic core of the bilayer repels polar molecules and ions, limiting their ability to pass through without assistance.

What are the functions of low-density lipoproteins (LDLs)?

LDLs transport fats to cells and are absorbed by cells via receptor-mediated endocytosis.