Cell Membrane Structure and Function – Study Guidance

Q1. What does the term “selective barrier” mean?

Background

Topic: Cell Membrane Function

This question is testing your understanding of how the cell membrane controls the movement of substances into and out of the cell, maintaining the internal environment.

Key Terms:

• Selective barrier: A structure that allows certain molecules or ions to pass through it by means of active or passive transport, but restricts others.

• Permeability: The property of a membrane that determines which substances can pass through it.

Step-by-Step Guidance

1. Consider what types of molecules the cell membrane allows to pass freely and which are restricted.

2. Think about the importance of maintaining different concentrations of ions and molecules inside versus outside the cell.

3. Reflect on how the structure of the membrane (phospholipid bilayer, proteins) contributes to its selective nature.

Try explaining the concept in your own words before checking the answer!

Q2. What does the term "Amphipathic” mean? How is a phospholipid amphipathic?

Background

Topic: Membrane Lipid Structure

This question is about the chemical properties of molecules that have both hydrophilic and hydrophobic regions, specifically phospholipids.

Key Terms:

• Amphipathic: A molecule that has both hydrophilic (water-loving) and hydrophobic (water-fearing) parts.

• Phospholipid: A lipid molecule with a hydrophilic head and two hydrophobic fatty acid tails.

Step-by-Step Guidance

1. Identify which part of a phospholipid is hydrophilic and which is hydrophobic.

2. Think about how this dual nature affects the behavior of phospholipids in water.

3. Consider why this property is important for membrane structure.

Try describing amphipathic molecules and their significance before revealing the answer!

Q3. Be familiar with the structures of a phospholipid, cholesterol, and a glycolipid. Be able to identify the hydrophilic and hydrophobic parts of each.

Background

Topic: Membrane Lipid Diversity

This question tests your ability to recognize and analyze the structural features of key membrane lipids and to distinguish their polar and nonpolar regions.

Key Terms:

• Phospholipid: Contains a phosphate group (hydrophilic head) and fatty acid tails (hydrophobic).

• Cholesterol: Has a small polar head (hydroxyl group) and a large nonpolar steroid ring structure with a hydrocarbon tail.

• Glycolipid: Lipid with a carbohydrate group attached, hydrophilic sugar head and hydrophobic tails.

Step-by-Step Guidance

1. Review diagrams of each molecule and label the hydrophilic and hydrophobic regions.

2. Compare the structural differences between the three types of lipids.

3. Think about how these differences affect their roles in the membrane.

Try sketching or labeling the structures before checking the answer!

Q4. How does a phospholipid differ from a triacylglycerol molecule? How does that difference in structure affect the nature of the molecule?

Background

Topic: Lipid Structure and Function

This question is about comparing the structures of two types of lipids and understanding how their differences influence their properties and functions.

Key Terms:

• Phospholipid: Contains a glycerol backbone, two fatty acid tails, and a phosphate group.

• Triacylglycerol (Triglyceride): Contains a glycerol backbone and three fatty acid tails, no phosphate group.

Step-by-Step Guidance

1. Draw or visualize the basic structure of each molecule.

2. Identify the key structural difference (number of fatty acid tails and presence/absence of phosphate group).

3. Consider how these differences affect solubility and function (e.g., membrane formation vs. energy storage).

Try explaining the structural and functional differences before revealing the answer!

Q5. Which phospholipid is the most common in plasma membranes? What is another name for this?

Background

Topic: Membrane Composition

This question is about identifying the predominant phospholipid in eukaryotic plasma membranes and knowing its alternative name.

Key Terms:

• Phosphatidylcholine: The most abundant phospholipid in many plasma membranes.

• Lecithin: Another name for phosphatidylcholine.

Step-by-Step Guidance

1. Recall the main classes of phospholipids found in plasma membranes.

2. Identify which one is most prevalent and its alternative/common name.

Try recalling the names before checking the answer!

Q6. Which membrane lipid is based on a change from glycerol to sphingosine?

Background

Topic: Membrane Lipid Diversity

This question is about recognizing the class of membrane lipids that use sphingosine instead of glycerol as their backbone.

Key Terms:

• Sphingolipids: Membrane lipids with a sphingosine backbone.

• Glycerolipids: Membrane lipids with a glycerol backbone.

Step-by-Step Guidance

1. Review the basic structures of glycerolipids and sphingolipids.

2. Identify which membrane lipid class is derived from sphingosine.

Try identifying the lipid class before revealing the answer!