ch 6 - lipids

Question 1

What is the function of the plasma membrane?

Answer 1

Regulates passage of molecules and concentrates reactants

Question 2

What created the first cell?

Answer 2

The development of plasma membrane round a self-replicator

Question 3

What are the building blocks of memberanes?

Answer 3

Lipids

Question 4

What is a lipid?

Answer 4

-Hydrophobic, nonpolar molecules
- Mostly hydrocarbon (C and H)
- Very diverse, defined by solubility
not by chemical structure
- Macromolecules but NOT
polymers

Question 5

What are the key building blocks of lipids?

Answer 5

Isoprene and fatty acids

Question 6

What are hydrophobic interactions?

Answer 6

Hold nonpolar molecules
together, more energetically
favorable

Question 7

What is the hydrophobic affect?

Answer 7

Tendency of nonpolar molecules to stay together

Question 8

What are the 3 important lipids found in cells?

Answer 8

1. Fats/oils: Glycerol +3 fatty acids
2. Phospholipids: Glycerol + 2 fatty acids + Phosphate group
3. Steroids: Four-ring structure

Question 9

Fats and oils are?

Answer 9

Triglycerides

Question 10

What is the primary role of fats and oils?

Answer 10

Energy storage

Question 11

What links fatty acids and glycerol?

Answer 11

Ester linkages

Question 12

What are saturated fats?

Answer 12

• No double bonds
• Solid at room temp
• Usually from animals
• Bad for health (if too much)

Question 13

What unsaturated fats (oils)?

Answer 13

• Contain one or more double bonds
• Liquid at room temp
• Usually from plants

Question 14

Saturated fats

Answer 14

• Tight packing of straight tails
• Solid at room temp
• No double bonds b/t carbon atoms; Fatty acid chains fit close together

Question 15

Unsaturated fats

Answer 15

• “Kinks” prevent tight packing of tails
• Liquid at room temperature

Question 16

How do fats store a great amount of energy?

Question 17

Why are fats
hydrophobic?

Question 18

What structure characterizes all steroids?

Answer 18

4 fused rings
- 3 six-sided and 1 five-sided

Question 19

What are some examples of steroids?

Answer 19

Cholesterol , testosterone, anabolic- androgenic steroids

Question 20

What is the structure of phospholipids? How is it different from triglycerides?

Answer 20

2 fatty acid tails, and a phosphate-linked head group; Triglycerides have 3 fatty acid tails

Question 21

Among the three lipids found in cells, which ones are amphipathic? Why?

Answer 21

Membrane lipids because they have both hydrophobic and hydrophilic areas in the molecule

Question 22

How are the phospholipids arranged in aqueous environment?

Answer 22

In lipid bilayers and micelles, where the hydrophilic heads interact with water and the hydrophobic tails interact with one another

Question 23

How do micelles and
phospholipid bilayers differ?

Answer 23

In their shape, micelles have one layer (monolayer) and phospholipid bilayers have two layers

Question 24

Why is this arrangement spontaneous?

Answer 24

Because they have one end that is polar and another that is non-polar

Question 25

What is the basic component of membranes?

Answer 25

Lipids, proteins, and carbohydrates

Question 26

What are the two membrane lipids? What characteristics do they both have?

Question 27

What is permeability?

Answer 27

tendency to allow a substance to pass across

Question 28

Why are membranes selectively permeable?

Answer 28

The hydrophobic interior only allows certain molecules to pass

Question 29

Why are membranes fluid?

Answer 29

The mosaic pattern of a membrane which helps in free movement

Question 30

What factors can affect the permeability and fluidity of plasma membrane?

Answer 30

• External factor: Temperature
• Internal factor:
  1. Fatty acid saturation (Number of double bonds)
  2. Length of fatty acid (if saturated)
  3. Presence of cholesterol - Buffer
  
  • lower fluidity

Question 31

Explain why the 3 factors affect permeability and the fluidity of the plasma membrane

Answer 31

1. Temperature -As temperature increases, so does phospholipid bilayer fluidity
2. The length of the fatty acid tail - Because the intermolecular interactions between the phospholipid tails add rigidity to the membrane
3. Cholesterol - Think of it is a buffer that helps keep membrane fluidity from getting too high or too low at high and low temperatures.