Membranes Structure and Function Flashcards
State 5 roles of membranes within cells and at the surface of cells.
- Membranes around organelles divide the cells into different compartments, acting as a barrier between the organelle and the cytoplasm.
- Membranes can form vesicles to transport substances between different areas of the cell.
- Membranes within cells are also partially permeable so they can control which substances enter and leave the organelle.
- Membranes within organelles act as barriers between the membrane contents and the rest of the organelle.
- Membranes within cells can be the site of chemical reactions, the membranes of some organelles are folded increasing their surface area and making chemical reactions more efficient.
Define the term “compartmentalisation” and explain why it is useful to the cells.
The formation of separate membrane bound areas in a cell is called compartmentalisation. It is vital to a cell as metabolism includes many different and often incompatible reactions. Containing reactions in separate parts of the cell allows the specific conditions required for cellular reactions.
Define the term “partially permeable”.
Membranes that allow some substances to cross but not others.
Define the term “cell signalling”.
A complex system of intercellular communication.
Define the term “phospholipid bilayer”.
It is an arrangement of phospholipids found in cell membranes, the hydrophilic phosphate heads form both the inner and outer surface of a membrane, sandwiching the fatty acid to form a hydrophobic core.
Explain what is meant by “fluid” and “mosaic” in the “fluid mosaic model of membrane structure”.
Fluid: all phospholipids and membrane proteins can move around because they are not bonded to eachother.
Mosaic: the phospholipids and the proteins form a pattern when viewed from above.
Fluid Mosaic model: model of the structure of a cell membrane in which phospholipids within in the phospholipid bi-layer are free to move and proteins of various shapes and sizes are embedded in various positions.
Define the term“glycoprotein”.
Extrinsic membrane proteins with attached carbohydrate molecules varying in lengths and shapes
Define the term “phospholipid”.
It is a modified triglyceride where one fatty is replaced by a phosphate group.
Define the term “cholesterol”.
A lipid containing a hydrocarbon tail attached to a hydrocarbon ring and a hydroxly group.
Define the term “glycolipid”.
Cell surface membrane lipids with attached carbohydrate molecules of varying lengths and shapes.
Define the term “channel protein”.
Intrinsic Membrane proteins that provide a hydrophilic channel through a membrane that allows passive movement of polar molecules and ions down the concentration gradient.
Define the term ‘‘carrier protein’’.
Membrane proteins that actively play a part in the transport of substances through a membrane using energy from ATP.
Define the term ‘‘intrinsic proteins’’.
Transmembrane proteins that are embedded through both layers of a membrane e.g. channel proteins or carrier proteins. They have amino acids with hydrophobic R-groups on their external surfaces which interact with the hydrophobic core of the membrane keeping them in place.
Define the term ‘‘extrinsic proteins’’.
Peripheral proteins that are present one side of the bi-layer only e.g. enzymes, proteins that bind cytoskeleto to membrane. They normaly have hydrophilic R-groups on their outer surfaces which interact with the polar heads of the phospholipids or with the intrinsic proteins.
Define the term ‘‘receptor protein’’.
Usually glycoproteins, they detect the presence of an extra cellular chemical and cause a response in the cell.
