Chapter 6: Lipids and Membranes

Question 1

Lipids are

Answer 1

not a polymer, they are not composed of the same building blocks. They are grouped together because they do not mix with water due to their structure, hydrophobic.

Question 2

What are the most biologically relevant lipids?

Answer 2

steroids, fats, and phospholipids.

Question 3

What are steroids characterized by?

Answer 3

a carbon skeletons with four fused rings. They are distinguished by the different chemical groups attached to the rings.

Question 4

Cholesterol is an example of?

Answer 4

a steroid. Cholesterol is an important component of cell membranes. It is also the precursor from which other steroids are synthesized like sex hormones.

Question 5

What are two types of cholesterol and what do they do?

Answer 5

low density lipoprotein (LDL) which is bad because it clogs arteries via forming plaque. High density lipoprotein (HDL) is considered good because it removes LDL from the bloodstream.

Question 6

What are fats constructed from?

Answer 6

glycerol and fatty acid. Commonly known as triglycerides.

Question 7

Saturated fats are

Answer 7

composed of no double bonds between carbon atoms, so the structure is saturated with hydrogen (has as many H atoms as possible).

Question 8

Unsaturated fats have

Answer 8

one or more double bonds between carbon atoms so there is one fewer H atom present on each double bonded carbon.

Question 9

Unsaturated fats can be

Answer 9

monounsaturated or polyunsaturated.

Question 10

Are saturated or unsaturated fats healthy?

Answer 10

Unsaturated fats are healthy, they are liquid at room temperature like fish oil. (Cold adapted organism will have more unsaturated hydrocarbon tails). Saturated fats lead to plaque build up which is bad and are solid at room temperature.

Question 11

What are trans fat?

Answer 11

they are man-made. It combines unsaturated fats and adds more hydrogen atoms (lose double bonds) which creates trans fats. This is because unsaturated fats are unstable and go bad faster. Trans fats are more solider at room temp which increases self stability.

Question 12

What are phospholipids composed of?

Answer 12

a hydrophilic head and hydrophobic tail. They are amphipathic and spontaneously form membranes.

Question 13

How does soap work?

Answer 13

hydrophobic tales react with dirt/oil as the hydrophilic tails interact with water and are then washed off.

Question 14

What is the plasma membrane made of?

Answer 14

lipids and proteins. Phospholipids which are fatty acids of different lengths and saturation influence membrane permeability. They easily form membranes because of they hydrophobic and hydrophilic components.

Question 15

What increases membrane permability?

Answer 15

unsaturated fatty acids and shorter hydrocarbon chains.

Question 16

2 major types of membrane proteins?

Answer 16

integral (transmembrane): span the membrane with segments both inside and outside the cell. (hydrophobic and hydrophilic). Peripheral: loosely bound to surface of membrane. (often inteact with exposed surface of integral proteins.

Question 17

Function of membrane proteins?

Answer 17

transport

Question 18

What can go through a selectively permeable membrane?

Answer 18

small nonpolar molecules (hydrocarbons, CO2, O2)

Question 19

Which ways do things move across the membrane with no energy needed?

Answer 19

diffusion and facilitated diffusion.

Question 20

What is diffusion (passive transport)?

Answer 20

movements of any molecule down its concentration gradient (from high to low). Unaffected by other substances. Spontaneous.

Question 21

What is osmosis?

Answer 21

diffusion of water across a semipermeable membrane. It is influenced by the concentration of solutes around it.

Question 22

Isotonic is

Answer 22

when the environment is the same as the cell. No net movement, cell is stable.

Question 23

Hypertonic is

Answer 23

when there is more solutes on the environment, outside the cell. Water moves out of the cell, cell shrivels = crenation.

Question 24

Hypotonic is

Answer 24

when there is less solutes in the environment so the water moves into the cell. The cell swells and may burst = hemolysis.

Question 25

What can speed up the process of osmosis?

Answer 25

the presence of aquaporins (proteins that form water channels in the membrane).

Question 26

What is facilitated diffusion?

Answer 26

when the composition of the membrane impedes the diffusion polar molecules and ions so transport proteins help them diffuse passively across the membrane. No energy required because it goes from high to low concentration.

Question 27

Two types of facilitated diffusion?

Answer 27

channel proteins which provide a doorway through the membrane. The second is carrier proteins which changes shape to shuttle molecules across the membrane.

Question 28

What is active transport?

Answer 28

movement of molecules against their concentration gradient which requires energy. This is done through ion pumps and secondary active transport (cotransport).

Question 29

How do ion pumps work?

Answer 29

move things based on difference of charge against gradient. Crucial for maintaining electrochemical gradients and membrane potential for nerve impulses.

Question 30

How do secondary active transport work?

Answer 30

uses the concentration gradient created by ATP-powered pump to power the transport of a molecule against its concentration gradient.

Question 31

What do DNA, proteins, and fats have in common?

Answer 31

they all contain carbonyl groups.