Biology Chapter 3 Test

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Lipids are...

hydrocarbons that are insoluble in water because they lack polar groups

fat provides...

insulation and energy storage in animals

phospholipids form...

plasma membranes

steroids are examples of

cell messengers

waxes do what in many organisms?

they have protective functions

Fats and oils contain what TWO molecular units

glycerol and fatty acids

Glycerol is a...

water-soluble compound with three hydroxyl groups

Triglycerides are...

glycerol joined to three fatty acids by dehydration reactions.

A fatty acid is...

A long hydrocarbon chain with a carboxylic acid group at one end

Most fatty acids in cell contain...

16 to 18 carbon atoms per molecule

Saturated fatty acids have no...

double bonds between their carbon atoms

Unsaturated fatty acids have...

double bonds in the carbon chain where there are less than two hydrogens per carbon atom

Difference between fats and oils?

Fats contain saturated fatty acids and are solid at room temperature, while oils contain unsaturated fatty acids and are liquid at room temperature.

What do animals use for long-term energy storage?

Fat rather than glycogen because fat stores more energy

How are phospholipids constructed?

They are constructed like neutral fats except that the third fatty acid is replaced by a polar (hydrophilic) phosphate group; the phosphate group usually bonds to another organic group (R)

What do the hydrocarbon chains of the fatty acids become?

They become the nonpolar (hydrophobic) tails.

How do phospholipids arrange themselves? And what does this allow phospholipids to create?

They arrange themselves in a double layer in water, so the polar heads face toward water molecules and nonpolar tails face toward one another, away from water molecules. ---- This allows phospholipids to create a separation between two solutions (the interior and exterior of a cell, for example); the plasma membrane is a phospholipid bilayer.

What are steroids made up of and what do those functional groups enable steroids to do?

Steroids have skeletons of four fused carbon rings and vary according to attached functional groups; these functional groups determine the biological functions of the various steroid molecules.

What does cholesterol do in general or generally act as?

It is a component of an animal cell's plasma membrane and is the precursor of the steroid hormone (aldosterone, testosterone, estrogen, calcitriol, etc.)

What are waxes composed of?

Long-chain fatty acids bonded to long-chain alcohols.

What do waxes do in general and in plants and animals?

They have a high melting point, are waterproof, and resist degradation. In plants, they form a protective covering in plants that retards water loss in leaves and fruits. In animals, waxes maintain animal skin and fur, trap dust and dirt, and form the honeycomb.

Carbon can do what...?

It can bond with as many as four other atoms, it can bond with itself to form both chains and rings.

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