Chapter 6: Lipids, Membranes, and Cell Structure

Exam 1 Mean

Average score before the curve is 65.

Exam 1 Median

Middle score before the curve is 67.

Curve

4 points added to final Exam 1 grade.

Plasma Membrane

Separates life from nonlife in cells.

Membrane Functions

Protects, allows entry, facilitates reactions.

Phospholipids

Main components of cell membranes.

Hydrophobic

Repellent to water; nonpolar.

Hydrophilic

Attracted to water; polar.

Fatty Acid

Hydrocarbon chain with a carboxyl group.

Saturated Fatty Acids

Only single C-C bonds; maximum H.

Unsaturated Fatty Acids

One or more double C=C bonds.

Polyunsaturated Fatty Acids

Multiple double bonds in hydrocarbon chain.

Lipid Types

Steroids, fats, phospholipids based on solubility.

Steroids

Lipids with bulky four-ring structure.

Cholesterol

Component of plasma membranes; steroid.

Fats (Triglycerides)

Three fatty acids linked to glycerol.

Ester Linkage

Bond between glycerol and fatty acid.

Phospholipid Structure

Two fatty acids, glycerol, phosphate group.

Amphipathic

Molecules with both hydrophobic and hydrophilic parts.

Lipid Bilayer

Two sheets of phospholipids forming membranes.

Liposomes

Artificial vesicles made of phospholipids.

Selective Permeability

Ability of membranes to control substance passage.

Diffusion

Movement of substances from high to low concentration.

Osmosis

Diffusion of water across a membrane.

Fluid-Mosaic Model

Describes membrane structure with proteins and lipids.

Transmembrane Proteins

Proteins spanning the membrane; involved in transport.

Channel Proteins

Facilitate passive transport of specific ions/molecules.

Gated Channels

Open/close in response to signals.

Aquaporins

Channel proteins allowing water passage.

Carrier Proteins

Change shape to transport larger molecules.

GLUT-1

Carrier protein increasing glucose permeability.

Active Transport

Moves substances against their gradient; requires energy.

Sodium-Potassium Pump

Transports Na+ out and K+ in using ATP.

Electrochemical Gradient

Concentration and charge difference across a membrane.

Membrane Fluidity

Influenced by saturation and temperature.

Low Temperature Effect

Decreases membrane fluidity and permeability.

Cholesterol Role

Increases hydrophobic density, reducing permeability.

Hydrophobic Interactions

Stronger with longer saturated tails; less permeable.

Vesicles

Small bubble-like structures surrounded by membranes.

Chemical Evolution Evidence

Lipids synthesized under early Earth conditions.

Hydrocarbon Structure

Only C and H; nonpolar and hydrophobic.

Functional Groups

Specific groups determining molecule properties.

Hydrocarbon Chain

Chain of carbon atoms in lipids.

Kink in Chain

Caused by double bonds in unsaturated fats.

Building Blocks

Complex lipids formed from fatty acids.

Membrane Proteins

Proteins that alter membrane structure and function.

Passive Transport

Movement without energy; includes diffusion.

Facilitated Diffusion

Passive transport via channel or carrier proteins.

Primary Active Transport

Directly uses ATP to move substances.

Secondary Active Transport

Uses electrochemical gradients to move substances.