1What is the main function of cell membranes?
To control what passes through them.
2What are eukaryotic cell organelles surrounded by?
Membranes.
3What is the role of cell-surface membranes?
They act as a barrier between the cell and its environment, controlling the movement of substances.
4What are membranes within cells important for?
Dividing the cell into different compartments for specific functions.
5What does "partially permeable" mean?
It means the membrane allows some substances to pass through but not others.
6What does the 'fluid mosaic' structure describe?
It describes the arrangement of molecules in the membrane.
7Why is the membrane described as "fluid"?
Because the phospholipids can move sideways.
8What makes the membrane "mosaic"?
Proteins scattered through the phospholipid bilayer.
9What is the function of cholesterol in the membrane?
It provides stability by fitting between phospholipids and making the membrane less fluid and more rigid.
10What do phospholipids form?
A barrier to dissolved substances.
11What are the two parts of a phospholipid molecule?
A hydrophilic head and a hydrophobic tail.
12What does hydrophilic mean?
Water-attracting.
13What does hydrophobic mean?
Water-repelling.
14How do phospholipids arrange themselves in the membrane?
They form a bilayer with heads facing water and tails facing inward.
15What type of substances cannot pass through the bilayer easily?
Water-soluble substances like ions.
16What are glycolipids?
Lipids with a polysaccharide chain attached.
17What affects the permeability of cell membranes?
Temperature, solvent concentration, and solvent type.
18What happens to membrane permeability as temperature increases?
It increases because the phospholipids move more and the structure breaks down.
19What happens to the membrane below 0°C?
Phospholipids don't move much, making the membrane more rigid but possibly leaky.
20What happens between 0°C and 45°C?
The phospholipids move more, increasing permeability slightly.
21What happens above 45°C?
The bilayer breaks down, proteins denature, and the membrane becomes highly permeable.
22What is the role of proteins in the membrane?
They control what enters and leaves the cell.
23What are receptor proteins?
Proteins that detect chemicals like hormones and signal the cell to respond.
24What is the main role of cholesterol in animal cells?
To provide stability and prevent the membrane from being too fluid.
25What is the 'fluid mosaic model'?
It is the model used to describe the dynamic and varied structure of cell membranes.
26What type of molecule is cholesterol?
A lipid.