Chapter 6: Lipids, Membranes and the First Cells

Vocabulary flashcards covering lipid structures, functions, types, and properties of membranes from Chapter 6.

Plasma membrane

A selective barrier separating life from nonlife that allows entry to materials needed by the cell, keeps negative materials out, and facilitates chemical reactions by sequestering appropriate chemicals.

Lipids

Carbon-containing compounds that are insoluble with water due to a high proportion of nonpolar C-C and C-H bonds.

Hydrocarbons

Nonpolar, hydrophobic molecules containing only carbon and hydrogen, in which electrons are shared equally in C-H bonds.

Isoprenoid

A hydrocarbon chain that functions as pigments, scents, vitamins, and sex hormone precursors, serving as building blocks for more complex lipids.

Fatty acid

A simple lipid made of a hydrocarbon chain containing $14$ to $20$ carbon atoms bonded to a polar carboxyl functional group.

Saturated hydrocarbon chains

Hydrocarbon chains consisting of single bonds between carbons, containing the maximum number of hydrogen atoms.

Unsaturated hydrocarbon chains

Hydrocarbon chains containing $1$ or more double bonds formed by the removal of hydrogen atoms, creating a kink in the chain.

Polyunsaturated chains

Hydrocarbon chains that contain many double bonds.

Saturated lipids

Butter. Highly saturated are solid at room temperature

Saturated lipids with long hydrocarbon tail

Beeswax. Stiff solids at room temperatyre

Highly unsaturated lipids

Safflower oil. Liquid at room temperature

Steroids

A family of lipids distinguished by a bulky, $4$-ring structure, differing from one another by functional groups attached to carbon in rings (e.g., estrogen, testosterone, cholesterol).

Fats

Non-polymer lipids composed of $3$ fatty acids linked to glycerol (also called triacylglycerols or triglycerides) that store $2\times$ chemical energy compared to other molecules.

Fats are formed by what kind of dehydration reactions?

Hydroxyl group of glycerol, carboxyl group of free fatty acid.

Ester linkage

The linkage joining a glycerol and a fatty acid molecule, formed by a dehydration reaction between the hydroxyl group of glycerol and the carboxyl group of a free fatty acid.

Phospholipids

Lipids consisting of glycerol linked to a phosphate group and $2$ hydrocarbon chains (fatty acid tails in domain Bacteria and Eukarya; isoprenoid tails in domain Archaea) that function to form cell membranes.

The phospholipids with fatty acid tails are found in which domain?

Bacteria, Eukarya

Phospholipids with isoprenoid tails are found in which domain?

Archaea

Functions of lipids

• store chemical energy

• act as pigments that respond to sunlight

• signals between cells

• waterproof coatings on skin and cells

• act as vitamins in cellular processes

Amphipathic

Substances that possess both hydrophilic and hydrophobic properties, such as phospholipids and cholesterol.

Hydrophilic head

The region of a phospholipid composed of glycerol, a negatively charged phosphate group, and a charged or polar group that interacts with water. RESPONSIBLE FOR PLASMA MEMBRANE

Hydrophobic tail

The nonpolar region of a phospholipid consisting of hydrocarbon chains with which water molecules cannot form hydrogen bonds.