Cell Membrane Structure and Function

The video explores the evolution of membrane models, starting with the outdated Davson-Danielli model, which proposed a bilayer of phospholipids with proteins on either side. New evidence led to the acceptance of the Singer-Nicholson model, known as the fluid mosaic model, which describes proteins interspersed within the membrane, allowing for fluidity and movement. The video highlights the nature of scientific progress and the importance of evidence in shaping our understanding of biological structures.

What was the primary reason for the initial acceptance of the Davson-Danielli model?

• It was supported by early evidence from red blood cell analysis.

• It was the only model available at the time.

• It was the first model proposed.

• It was simpler to understand.

What did the Davson-Danielli model propose about the structure of the cell membrane?

• A single layer of phospholipids with proteins scattered throughout.

• A double layer of phospholipids with proteins on either side.

• A single layer of proteins with phospholipids on either side.

• A triple layer of proteins with phospholipids in between.

Why did the Davson-Danielli model suggest a double layer of phospholipids?

• Because it was easier to visualize.

• Due to the presence of cholesterol in the membrane.

• Because proteins were found only on the outside.

• Due to the presence of more phospholipids than needed to surround a red blood cell once.

What is another name for the Singer-Nicholson model?

• Fluid Mosaic Model

• Dynamic Protein Model

• Static Mosaic Model

• Rigid Structure Model

What evidence supported the fluid mosaic model over the Davson-Danielli model?

• The presence of a single layer of phospholipids.

• The absence of proteins in the membrane.

• The discovery of proteins embedded within the membrane.

• The presence of cholesterol in the membrane.

What technique was used to demonstrate the presence of proteins within the membrane?

• Mass spectrometry

• Freeze fracturing

• Nuclear magnetic resonance

• X-ray crystallography

What did the fluorescent tagging experiments reveal about the cell membrane?

• Proteins can move within the membrane, indicating fluidity.

• Proteins are absent in the membrane.

• Proteins are only found on the outer layer.

• Proteins are static and do not move.

What property of proteins supports the fluid mosaic model?

• Proteins are entirely hydrophilic.

• Proteins are entirely hydrophobic.

• Proteins have both hydrophilic and hydrophobic regions.

• Proteins are only found on the surface of the membrane.

How do phospholipids contribute to the fluidity of the membrane?

• They are only found in the center of the membrane.

• They move around each other, allowing fluidity.

• They form a static barrier.

• They are rigid and do not move.

What is the significance of polar and non-polar amino acids in membrane proteins?

• They have no impact on the protein's function.

• They influence the protein's position and function within the membrane.

• They affect the protein's ability to bind to DNA.

• They determine the protein's color.