Chapter 6 Biology: Lipids, Membranes, and the First Cells

What are the attributes of a lipid?

1. Primarily carbon and hydrogen based compounds (hydrocarbons)
2. Largely nonpolar and hydrophobic (insoluble in water)

What are the two building blocks found in many lipids?

1. Fatty acid
2. Isoprene

What are the three most important types of lipids found in cells?

1. Fats (triglycerides)
2. Steroids
3. Phospholipids

What are the structures of fats?

A glycerol linked to 3 fatty acids (triglyceride) by an ester linkage

Compare saturated and unsaturated fatty acids.

Saturated fatty acid chains: single bonds (LINEAR)
Unsaturated fatty acids chains: 1 or more double bonds (KINKS)
*Saturation affects the physical characteristics of lipids*

What are some examples of highly saturated fats?

butter, lard, animal fat

What are some examples of highly unsaturated fats?

sesame seed oil, olive oil

What is a steroid?

A four-ring structure, differ by functional groups

What are three examples of steroids? Explain each.

1. cholesterol: a hydrophilic hydroxyl group attached to the top ring and an isoprenoid "tail" attached at the bottom
2. testosterone: male hormone
3. estradiol: female hormone used to regulate reproductive cycles

List and describe the 3 components of a phospholipid.

1. glycerol attached
2. 2 hydrophobic fatty acid "tails" (or isoprene tails)
3. Phosphate, and charged group "head"

Which component of a phospholipid interact with water?

The phospholipid head

What are the 2 structures that phospholipids can form upon contact with water?

1. Micelles: heads face the water and tails face each other
2. Phospholipid bilayer (lipid bilayer): two layers of phospholipid molecules align (hydrophilic heads face surrounding solution / the hydrophobic tails face one another

What are the 3 functions of a plasma/cell membrane?

1. Keep damaging materials out of the cell
2. Allow entry of materials needed by the cell
3. Facilitate the chemical reactions necessary for life

What is selective permeability in regards to
molecules?

The tendency to allow a given substance to pass across it

List and explain the 4 factors that influence the permeability of the cell membrane.

1. number of double bonds between the carbines in the phospholipid's hydrophobic tail
2. length of the tail
3. number of cholesterol molecules in the membrane
4. temperature

Do individual phospholipids move throughout the lipid bilayer more, or flip between layers?

Individual phospholipids can:
-move laterally throughout the lipid bilayer
-rarely flip between layers

List the 3 transport mechanisms.

1. passive transport
2. facilitated transport
3. active transport

Does passive transport require energy?

No

What is diffusion?

The random movement of molecules from a high concentration to a low concentration

Explain osmosis?

-the movement of water through a selectively permeable membrane leaving molecules on the other side
-water tends to equalize the concentration of solutes across a membrane
-water moved toward the higher concentration gradient

Define and explain isotonic, hypotonic, and hypertonic in reference to water movement
in/out of a cell.

1. isotonic: equal solute concentration inside cell as outside (No net movement of water)
2. Hypotonic: solution with a lower concentration of solutes, than inside of a cell (Water moves from solution, into cell by osmosis)
3. Hypertonic: solution with a higher concentration of solutes, than inside of a cell (Water moves from cell, into solution by osmosis)

Compare: integral, transmembrane, and peripheral proteins.

-transmembrane (integral) proteins are amphipathic and span the membrane facing the interior & exterior of a cell (involved in the transport of selected ions and molecules across the membrane / able to affect permeability)
-Peripheral proteins are found only on the side of the membrane (often attached to integral proteins)

Identify the location of the charged amino acids.

List and define the three types of transport proteins.

1. Channels: proteins selective in which molecules pass along a membrane
2. Carrier proteins or transporters: change shape during the transport process moving molecules down a concentration gradient
3. Pumps: membrane proteins that provide active transport molecules across the membrane against a concentration gradient and requires energy, ATP