Chapter 6: Lipids, Membranes, and the First Cells

This set of flashcards covers key concepts from Chapter 6 on lipids, membranes, and the first cells, including membrane structure, transport mechanisms, and the roles of various lipids and proteins.

What are the two main components of the plasma membrane?

Lipids and proteins.

What type of molecules spontaneously form bilayers in a biological membrane?

Lipids.

How do substances move across lipid bilayers?

Via diffusion and osmosis.

What is the primary role of phospholipids in cells?

To form cell membranes.

What type of fatty acids are composed only of single bonds between carbon atoms?

Saturated fatty acids.

What is the effect of unsaturated fatty acids on the structure of lipid membranes?

They introduce 'kinks' that affect fluidity and permeability.

How do cholesterol molecules affect membrane permeability?

They reduce membrane permeability and increase density.

What is the difference between passive transport and active transport?

Passive transport does not require energy, while active transport requires energy input.

What type of solution causes a cell to swell as water moves into it?

Hypotonic solution.

What is facilitated diffusion?

The passive transport of substances across a membrane aided by membrane proteins.

How does temperature affect membrane fluidity?

Membrane fluidity decreases as temperature drops.

What happens to lipids during osmosis?

Water moves from low to high solute concentrations.

What defines amphipathic molecules?

They have both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions.

What is the role of protein channels in cell membranes?

To facilitate the passage of ions and small molecules.

What is the sodium-potassium pump?

A membrane protein that actively transports sodium ions out of the cell and potassium ions into the cell.

What are protocells hypothesized to be?

Simple vesicle-like structures that may have led to the evolution of cells.

What did the fluid-mosaic model propose about membrane structure?

It suggests that some proteins span membranes and that membranes are a dynamic mosaic of phospholipids and proteins.

How do membrane proteins affect cell function?

By altering the structure and function of the membrane, enabling transport and communication.

What are micelles and bilayers?

Micelles are small spherical aggregates of lipids; bilayers are two layers of lipids forming membranes.

What is diffusion?

The spontaneous movement of molecules from areas of high concentration to areas of low concentration.