membrane
Definition
In biology, a membrane is a thin layer of tissue that separates two parts of an organism. Membranes are made up of lipids and proteins. Lipids are molecules that are made up of fat and water. Proteins are molecules that are made up of amino acids.
The lipids in a membrane form a bilayer, which is two layers of lipids that are arranged back-to-back. The proteins in a membrane are embedded in the lipid bilayer.
The bilayer structure of a membrane allows it to be selective about what molecules can pass through it. This is because the lipids in the bilayer have different properties. Some lipids are more permeable to certain molecules than others.
The proteins in a membrane also play a role in regulating the movement of molecules. Some proteins act as channels that allow certain molecules to pass through the membrane. Other proteins act as pumps that move molecules across the membrane against a concentration gradient.
Membranes are important for many different functions in the body. They help to protect cells, transport molecules, and regulate the movement of fluids.
How can the word be used?
The mucous membrane lines the inside of the mouth and nose and helps to protect them from infection.
Different forms of the word
Noun: A thin, flexible sheet of tissue that covers or separates parts of an organism.
Adjective: Composed of or relating to a membrane.
Verb: To cover or separate with a membrane.
Etymology
The word "membrane" comes from the Latin word "membrana", which means "skin" or "parchment". The Latin word "membrana" is derived from the Proto-Indo-European root *mems-, which means "flesh".
Question
What is a membrane?
AQA Science Exam Question and Answer
Question:
Explain the role of a membrane in biological systems and provide examples of different types of membranes in living organisms. Discuss the functions of these membranes and how they contribute to the overall functioning of cells and organisms.
Answer:
In biological systems, a membrane refers to a thin, flexible layer that separates different compartments within cells or organisms. Membranes play a crucial role in maintaining the integrity and functionality of these compartments, regulating the passage of molecules and ions.
Cell membranes, also known as plasma membranes, encase cells and control the movement of substances in and out of the cell. They consist of a lipid bilayer with embedded proteins that facilitate selective transport and communication.
Organelles within cells, such as the nucleus, mitochondria, and endoplasmic reticulum, are also enclosed by membranes. These organelle membranes perform specific functions. The nuclear envelope protects the genetic material, the mitochondrial membrane produces energy, and the endoplasmic reticulum membrane is involved in protein synthesis and lipid metabolism.
In organisms, membranes are also found in structures like the skin, respiratory surfaces, and digestive tracts. These membranes facilitate gas exchange, nutrient absorption, and waste removal.
Overall, membranes are essential for compartmentalization, selective transport, protection, and communication within cells and organisms. They ensure the internal environment remains distinct from the external one, enabling efficient processes for growth, energy production, and maintenance of homeostasis.