Bio 120 Chapter 6 Lipids, Membranes, and Cell Structure Overview

What is the primary function of the plasma membrane?

To separate the interior of the cell from the external environment and facilitate necessary chemical reactions.

What are lipids primarily characterized by?

They are carbon compounds that are largely nonpolar and hydrophobic.

What is the structure of a fatty acid?

A hydrocarbon chain bonded to a carboxyl (-COOH) functional group, typically containing 14-20 carbon atoms.

What distinguishes saturated hydrocarbon chains from unsaturated ones?

Saturated chains consist only of C-C bonds with maximum H bonds, while unsaturated chains have one or more C=C bonds, resulting in a 'kink'.

What are the three main types of lipids found in cells?

Steroids, fats, and phospholipids.

What is the primary role of phospholipids in cells?

To form cell membranes.

What is the structure of a triglyceride?

Three fatty acids linked to a glycerol.

What is the role of cholesterol in cell membranes?

Cholesterol is a component that helps maintain membrane fluidity and stability.

How do phospholipids arrange themselves in a bilayer?

Two sheets align with hydrophilic heads facing outward and hydrophobic tails facing inward.

What is an amphipathic molecule?

A molecule that has both hydrophilic and hydrophobic regions, such as phospholipids.

What happens to membrane permeability at low temperatures?

Membrane fluidity decreases, leading to reduced permeability.

How does the saturation of hydrocarbon tails affect membrane permeability?

Increased saturation leads to stronger hydrophobic interactions, resulting in lower permeability.

What are liposomes?

Artificial membrane-bound vesicles formed from phospholipid bilayers.

What is the significance of lipid bilayers in experiments?

They are used to measure the permeability of membranes to various substances.

What is the effect of cholesterol on membrane permeability?

Cholesterol increases the density of the hydrophobic section, which decreases membrane permeability.

What functional groups are associated with proteins?

Amino groups (-NH₂) and carboxyl groups (-COOH).

What functional groups are associated with carbohydrates?

Carbonyl groups (C=O) and hydroxyl groups (-OH).

What is the role of fats in biological systems?

They primarily serve as energy storage.

What is a key characteristic of steroids?

They have a bulky, four-ring structure and differ based on functional groups.

What is the relationship between hydrocarbon length and membrane permeability?

Longer hydrocarbon tails reduce membrane permeability.

What evidence supports the presence of lipids during chemical evolution?

Simple lipids, such as fatty acids, can be synthesized under early Earth conditions.

What are the hydrophilic components of phospholipids?

Glycerol, a negatively charged phosphate group, and a charged or polar group.

What is the significance of functional groups in lipids and proteins?

They determine the chemical properties and functions of the molecules.