BIO1010 Reading Guide Module 10 Cell Membrane Structure
1.Define:
. Amphipathic:
A. Amphipathic molecules have both hydrophilic (water-attracting) and hydrophobic (water-
repelling) parts. In the context of cell membranes, phospholipids are amphipathic, with hydrophilic
heads and hydrophobic tails.
B. Cholesterol:
C. Cholesterol is a type of lipid found in the cell membrane of animal cells. It helps to modulate the
fluidity and stability of the membrane by preventing it from becoming too rigid or too fluid at varying
temperatures.
D. Transport protein:
E. Transport proteins are integral membrane proteins that facilitate the movement of substances
across the cell membrane. They can be involved in passive transport (e.g., channel proteins) or active
transport (e.g., carrier proteins).
F. Aquaporin:
G. Aquaporins are a type of channel protein that specifically facilitates the transport of water
molecules across the cell membrane, allowing for rapid and efficient water movement.
. Diagram how phospholipids form a bilayer when placed in water.
1. 1. Phospholipid Bilayer Formation:
2.
3. When placed in water, phospholipids form a bilayer with the hydrophilic (polar) heads
facing the water on both sides of the bilayer and the hydrophobic (nonpolar) tails facing each
other inside the bilayer. This structure forms the basic framework of cell membranes.
. Describe the fluid-mosaic model of membrane structure. Draw and label a phospholipid bilayer
with transmembrane proteins, peripheral membrane proteins, cholesterol, glycoproteins, and
glycolipids.
1.
2. • The fluid-mosaic model describes the cell membrane as a dynamic and flexible structure
with a mosaic of various proteins floating in or on the fluid lipid bilayer.
3. • Diagram: Draw a bilayer with the following components:
4. • Phospholipid Bilayer: Two layers of phospholipids with heads facing outward
and tails inward.
5. • Transmembrane Proteins: Proteins that span the entire membrane.
6. • Peripheral Membrane Proteins: Proteins attached to the surface of the
membrane.
7. • Cholesterol: Molecules interspersed within the phospholipid bilayer.
8. • Glycoproteins: Proteins with carbohydrate chains attached.
9. • Glycolipids: Lipids with carbohydrate chains attached.
. Explain the function of the oligosaccharides attached to glycoproteins and glycolipids on the cell
membrane.
1. Oligosaccharides attached to glycoproteins and glycolipids on the cell membrane play a crucial
role in cell-cell recognition, communication, and adhesion. They act as cellular “identification tags” that
are recognized by other cells.
. Describe the structure of channel proteins and carrier proteins.
1. • Channel Proteins: These proteins form pores in the cell membrane, allowing
specific molecules or ions to pass through via facilitated diffusion. They are often selective for particular
substances.
2. • Carrier Proteins: These proteins bind to specific molecules on one side of the
membrane, change shape, and release the molecules on the other side. They can be involved in passive
or active transport.
. Explain what it means that cell membranes are selectively permeable.
Selective permeability means that the cell membrane allows certain substances to pass through while
blocking others. This property is essential for maintaining homeostasis, as it controls the internal
environment of the cell by regulating the entry and exit of various substances.
