Chapter 6, Lipids, Membranes, and the First Cells

Question 1

Plasma membrane (cell membrane)

Answer 1

thin membrane that surrounds every living cell.

Question 2

Function of cell membrane

Answer 2

selective barrier that keeps damaging substances out and allows needed substances in.

Question 3

Lipid

Answer 3

Any organic substances that do not dissolve in water but dissolve well in nonpolar organic solvents. Includes: fatty acids, fats, oils, waxes, steroids and phospholipids

Question 4

hydrocarbons

Answer 4

An organic nonpolar molecule that contains only hydrogen and carbon atoms

Question 5

isoprene

Answer 5

five-carbon compound that entirely consists of carbon atoms bonded to hydrogen atoms.

Question 6

Fatty acid

Answer 6

Consists of a hydrocarbon chain bonded at one end to a carboxyl group. Used as building blocks for other lipids. Used by many organisms to store chemical energy, a major component of animal and plant fats and phospholipids

Question 7

Saturated fatty acids

Answer 7

Hydrocarbon chains that consist of only single bonds between the carbons

Solid at room temperature

Question 8

Unsaturated fatty acids

Answer 8

If one or more double bonds exist in the hydrocarbon chains

Liquids at room temperature

Question 9

waxes

Answer 9

A class of lipid with extremely long, saturated hydrocarbon tails

Question 10

Oils

Answer 10

polyunsaturated fat that is liquid at room temperature.

Question 11

Three most important type of lipids found in cells

Answer 11

steroids, fats and phospholipids

Question 12

Steroids

Answer 12

lipid with characteristic four ring hydrocarbon chain structure.

Question 13

Fats (triacylglycerols or triglyceride)

Answer 13

nonpolar molecules composed of three fatty acid that is linked to glycerol (3 carbon molecule). Energy storage is the primary role of fats

Fats form when dehydration reactions occurs between a hydroxyl group of glycerol and the carboxyl group of a free fatty acid

Question 14

glycerol

Answer 14

three-carbon molecule that forms the backbone of phospholipids and most fats

Question 15

Primary role of fats

Answer 15

energy storage in organisms. Stores twice as much chemical energy per gram as carbohydrates due to having higher ratio of bonds with high potential energy to bonds with low potential energy

Question 16

Free fatty acid

Answer 16

Fatty acids that are not attached to other molecules

Question 17

Ester linkage

Answer 17

The covalent bond formed between condensation reaction between carboxyl group and hydroxyl group.

Join fatty acids to glycerol to form a fat or phospholipid

Occur when dehydration reactions connect glycerol to three fatty acids

Question 18

Phospholipids

Answer 18

Contain 2 fatty acid tails linked to a glycerol and it has a phosphate group linked to the glycerol
Cell membranes are made mostly of phospholipids

Question 19

Phospholipids with fatty acd tails

Answer 19

Found in domains bacteria and Eukarya

Question 20

Phospholipids with isoprenoid tails

Answer 20

Found in domain archaea

Question 21

amphipathic

Answer 21

Containing both hydrophilic and hydrophobic regions.

When amphipathic lipids are placed in water they become either micelles or lipid bilayers

Question 22

Micelles

Answer 22

Tiny spherical aggregates are created when the hydrophilic heads face outwards and interact with water, while the hydrophobic tails interact with each other in the interior

Form from free fatty acid or other amphipathic lipids with single hydrocarbon chains

Question 23

lipid bilayer

Answer 23

created when lipid molecules align in paired sheets. Hydrophilic heads in each layer face the surrounding solution and the hydrophobic tails face one another inside the bilayer

Phospholipids have bulkier nonpolar regions consisting of two hydrocarbon tails, so they form bilayers

Question 24

vesicles

Answer 24

small bubble-like structures consisting of lipid bilayers and surrounded by small amount of aqueous solution

Question 25

liposomes

Answer 25

An artificial vesicle formed by mixing amphipathic lipids such as phospholipids together in an aqueous solution

Question 26

Permeability

Answer 26

The tendency of a structure, such as a membrane, to allow a given substance to diffuse across it.

Question 27

Selective permeability

Answer 27

Some substances cross a membrane more easily than other substances do

Question 28

Factors that profoundly affect permability

Answer 28

lipid bilayers are more permeable when they contain many short, kinked, unsaturated hydrocarbon tails. Its less straight with long, saturated hydrocarbon tails.

Question 29

Effect of cholesterol molecules on membrane

Answer 29

adding cholesterol molecules to membranes reduces their permeability

Question 30

level of fludity in a membrane

Answer 30

membrane’s permability depends on its fluidity. When the temp drops, the permeability is low and molecules in the bilayer move more slowly

Question 31

Diffusion

Answer 31

Spontaneous movement of molecules and ions from high to low concentration is known as diffusion.

Question 32

concentration gradient

Answer 32

Difference across space in the concentration of a dissolved substance

Question 33

Passive transport

Answer 33

Movement of molecules from higher concentration to lower concentration and no amount of energy is required

Question 34

Osmosis

Answer 34

Diffusion of water across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration

Question 35

Hypertonic

Answer 35

If solution outside the vesicle has a higher concentration of solutes than the interior has. The water moves out of the vesicle and it shrinks

Question 36

Hypotonic

Answer 36

If solution outside the vesicle has a lower concentration of solutes than the interior has. Water moves into the vesicle via osmosis and it can cause the vesicle to swell or burst

Question 37

isotonic

Answer 37

If the solute concentrations are equal on both sides of the membrane, there is no movement of water and the vesicle stays the same.

Question 38

Phospholipid

Answer 38

Type of lipid molecule that is the main component of the cell membrane.

Made up of 2 fatty acids, a phosphate group and glycerol molecule.

Molecule has a hydrophilic head containing a phosphate group and two hydrophobic tails derived from fatty acids

Question 39

protocells

Answer 39

Simple vesicle-like structures that harbor nucleic acids

Question 40

Fluid mosaic model

Answer 40

Widely accepted hypothesis that cellular membranes consist of proteins embedded in a fluid phospholipid bilayer.

Question 41

Scanning electron microscope

Answer 41

A microscope that produces surface images by reflecting electrons off a speciman coated with a layer of metal atoms

Question 42

integral membrane proteins (transmembrane proteins)

Answer 42

Any membrane protein that spans the entire lipid bilayer

Question 43

Peripheral membrane proteins

Answer 43

Proteins that bind to membrane lipids or integral membrane proteins without passing through it

Question 44

ion channels

Answer 44

Type of channel protein that allows certain ions to diffuse across a plasma membrane down an electrochemical gradient

They form pores, or openings in a membrane and the ions diffuse through these pores from high to low concentration regions.

Question 45

Electrochemical gradient

Answer 45

combined effect of an ion’s concentration gradient and electrical gradient across a membrane that affects the diffusion of ions

Question 46

Channel proteins

Answer 46

transmembrane protein that forms a pore in a cell membrane which may open or close in response to a signal.

Question 47

aquaporin

Answer 47

type of channel protein that faciliates the movement of water (osmosis) across a plasma membrane

Question 48

gated channels

Answer 48

open or close in response to a signal

Question 49

carrier proteins

Answer 49

transmembrane protein that facilates diffusion of a small moleule across a membrane

Question 49

facilitated diffusion

Answer 49

Passive movement (diffusion) of a substance across a membrane with the assistance of transmembrane carrier proteins or channel proteins

Question 50

Difference between channel and carrier proteins

Answer 50

Channels allow movement through a selective pore, much like bridges allow people to cross back and forth over a river. In contrast, carrier proteins selectively pick up a solute on one side of the membrane, then drop it off on the other side.

Question 51

active transport

Answer 51

movement of ions or molecules from lower to higher concentration with the use of energy. Moves against the concentration gradient

Question 52

Pump

Answer 52

Any membrane protein that uses energy to change shape and power the active transport of a specific ion or molecule across a membrane in a single direction, against its gradient.

Question 53

Sodium-potassium pump

Answer 53

A transmembrane protein that uses the energy of ATP to move sodium ions out of the cell and potassium ions into the cell

Question 54

Most permeable membranes

Answer 54

unsaturated phospholipids
Temp
Cholesterol

Question 55

Membranes with some degree of permeability

Answer 55

small nonpolar like O2
Small polar/noncharged like H20

Question 56

Never permeable

Answer 56

ions

Question 57

Cholesterol

Answer 57

A type of steroid that has a polar hydrophilic hydroxyl group and a nonpolar isoprenoid tail at the bottom

Question 58

Isoprenoid

Answer 58

structural formula of a chain of linked isoprenes

Question 59

phospholipid bilayer

Answer 59

Lipid bilayers consisting of phospholipids

Question 60

Selective permeability of the lipid bilayer

Answer 60

High permeability: Small nonpolar molecules
Medium permeability: small uncharged polar molecules
Low permeability: Large, uncharged polar molecules
No permeability: Small ions

Question 61

What in the lipid structure effects membrane permeability

Answer 61

Temperature
Cholesterol: More cholesterol to membranes means lower permeability to glycerol
Saturation: An unsaturated membrane is more permeable while a saturated membrane is less permeable
Hydrocarbon tail length: Short hydrocarbon chains go through with higher permeability vs the long hydrocarbon chains