Bio Chapter 6- Lipids, Membranes, and Early Cells

UH Biology w/ Rita Sharp

What kind of membranes did protocells may have had?

simple, permeable membranes

What defines a cell?

Membranes

Why do membranes assemble?

The chemical nature of the cell

What are lipids?

carbon containing compounds that’s insoluble in water

Why are lipids not soluble in water?

high proportion of non polar C-H and C-C bonds

What’re hydrocarbons?

non polar molecules that contain only carbon and hydrogen and that’s hydrophobic

How are electrons shared in hydrocarbons?

equally shared in C-H bonds

What is an isoprenoid?

A hydrocarbon chain

What’re the functions of isoprenoids?

• pigments

• scents

• vitamins

• sex hormone precursors

• building blocks for more complex lipids

What is a fatty acid?

A hydrocarbon chain bonded to a carboxyl (-COOH)

What’s a saturated fatty acid?

A fatty acid that contain single C-C bonds, with a straight structure

Are saturated fats solid or liquid at room temperature?

Solid

What’s a unsaturated fat?

A fat with at least one double C-C bond, which creates a kink that stops molecules from packing together tightly.

Are unsaturated fats solid or liquid at room temperature?

Liquid

What’re the three most important shapes found in lipids?

What makes steroids different from other lipids?

What makes steroids different from one another

What’re some examples of steroids?

What are fats composed of?

What are fats also called?

q

What is the role of fats?

Why do fats have so much energy?

What is an ester linkage?

What’re the functions of lipids?

• form membranes

What is an amphipathic lipid?

What’re the parts of amphipathic lipids and their interactions with water?

What’re the two types of amphipathic lipids?

What’s a micelle?

What’s a lipid bilayer?

What does this image represent?

Amphipathic lipids

What does this image show?

A lipid bilayer

What is a planar bilayer?

What kind of molecules cross a plasma membrane most easily?

small, non polar compounds

What distinguishes lipids from other macromolecules?

Is the lipid membrane polar or non polar?

non polar

Why do nonpolar molecules make it across the lipid bilayer?

Longer chain fatty acids _____ solute permeability, and saturated bonds ______ solute permeability.

Decrease, Decrease

Why do longer fatty acid chains decrease permeability and why do saturated bonds decrease permeability?

• Longer fatty acid tails make the bilayer thicker and harder to get through

• unsaturated bilayers have kinks and add space inside the membrane, making it easier to get through

What does cholesterol do the lipid bilayer?

Makes them more rigid + hard to pass

What is movement across membranes called?

Diffusion

• Facilitated diffusion

Active Transport

Osmosis

What is diffusion?

random movement that requires no energy and happens from high to low concentration

How does diffusion move?

High to low concentration

What is active transport?

Moving against the concentration gradient using energy

What is osmosis?

Water moving across the membrane to dilute a solute (that can’t move across the membrane itself) that takes no energy

Water moves to…

dilute solutes

Where are proteins in membranes?

embedded in

What is the Fluid-Mosaic model?

What region of an Amphipathic protein can be anchored into the lipid bilayer?

the hydrophobic region

What is a detergent?

What is an amphipathic molecule?

What’s the function of detergents?

SLIDE 38