Question

part 1: plasma membrane
3.2 the plasma membrane is a double layer of ______________ with embedded proteins
a. membrane lipids form a bilayer, composed of two layers of ____________ (75%) with small amounts of __________ (5%), and ____________ (20%).

1. the tails of phospholipids are ____________ and line up facing each other in the interior of the bilayer, while the ____________ phospholipid heads to face the inner and outer surfaces of the membrane.
2. ______________ helps maintain the membrane stability of the plasma membrane.
3. ______________ are lipids with sugar groups located on the outer membrane surface.

b. cell junctions

1. ______________ are integral proteins that form an impermeable junction that prevents molecules from passing through the extracellular space between cells.

where do you find these in the body?

1. ______________ are anchoring junctions that are scattered along the sides of adjoining cells that prevent their separation and reduce the chance of tearing when a tissue is stressed.

where do you find these in the body?

Explanation:

1. The plasma membrane is a lipid - bilayer with embedded proteins. The lipid bilayer is mainly composed of phospholipids (75%), with small amounts of cholesterol (5%) and glycolipids (20%). Phospholipid tails are hydrophobic and face each other in the bilayer interior, while heads face the inner and outer membrane surfaces. Cholesterol helps maintain membrane stability. Glycolipids are lipids with sugar groups on the outer membrane surface.
2. Tight junctions are integral proteins forming an impermeable junction to prevent molecule passage between cells, found in the lining of the digestive tract (e.g., intestinal epithelium) to control absorption.
3. Desmosomes are anchoring junctions scattered along adjoining cell sides to prevent separation and reduce tearing when tissue is stressed, found in the skin and heart muscle.

Answer:

1. Phospholipids; cholesterol; glycolipids; hydrophobic; hydrophilic
2. Cholesterol
3. Glycolipids

B1. Tight junctions; lining of the digestive tract (e.g., intestinal epithelium)
B2. Desmosomes; skin and heart muscle