#1 - Lipids

Question 1

What are Membrane lipids?

Answer 1

Membrane lipids are a group of compounds which form the double-layered surface of all cells
(lipid bilayer).

Question 2

What are the three major classes of membrane lipids?

Answer 2

• Phospholipids
• Glycolipids
• Cholestrol

Question 3

Describe the structure of membrane lipids:

Answer 3

they are structurally similar
to fats and oils, which are hydrophobic, soluble in organic
solvents. They are amphiphilic.

Question 4

what does the term amphiphilic mean?

Answer 4

A molecule with both hydrophilic (polar) and hydrophobic (nonpolar) regions.

Question 5

describe how membrane lipids are amphiphilic:

Answer 5

they have one end that is
soluble in water (‘polar’) and an ending that is soluble in fat
(‘nonpolar’).

Question 6

describe the structure of phospholipids:

Question 7

describe the structure of glycolipids:

Answer 7

glycolipids

Question 8

describe the structure of cholesterol:

Question 9

how can lipids form a bilayer?

Answer 9

By forming a double layer with the polar ends
pointing outwards and the nonpolar ends pointing inwards.

Question 10

what is the function of a lipid bilayer

Answer 10

it keeps the
watery interior of the cell/ cell membranes separate from the watery exterior.

Question 11

what are phospholipids?

Answer 11

Phospholipids are phosphate containing lipids, the head consists of a glycerol backbone and a phosphate group, the tails’ fatty acid

Question 12

What is the most common type of membrane lipid?

Answer 12

Phospholipids

Question 13

Name the two major classes of phospholipids

Answer 13

Sphingolipids and phosphoglycerides

Question 14

What are the components of phosphoglycerides?

Answer 14

Glycerol backbone, two fatty acid chains, a phosphate group, and an alcohol.

Question 15

What is the polar head portion of a phosphoglyceride comprised of?

Answer 15

The glycerol backbone and the phosphorylated alcohol.

Question 16

Describe the fatty acid “tails” in phospholipids.

Answer 16

hey usually have an even number of carbon atoms, averaging 14-24, with 16 and 18 being the most common numbers.

Question 17

What are the components of phospholipids?

Answer 17

Phospholipids are composed of a glycerol molecule, fatty acids (or diglyceride), a phosphate group, and a polar molecule such as serine, choline, or ethanolamine.

Question 18

What is a glycolipid?

Answer 18

A glycolipid is a lipid with a carbohydrate group attached to its hydrophilic head.

Question 19

Where are glycolipids predominantly found in the cell membrane?

Answer 19

Glycolipids are found exclusively on the extracellular side of the plasma membrane.

Question 20

What role does glycocalyx play, and where is it produced?

Answer 20

Glycocalyx, produced by glycolipids, is involved in toxin recognition. It is produced on the extracellular side of the plasma membrane.

Question 21

What forms the liquid matrix in the lipid bilayer?

Answer 21

The lipid bilayer forms a liquid (liquid-crystal) matrix.

Question 22

Where are the fatty acid tails of phospholipids located, and what phase do they form?

Answer 22

The fatty acid tails of phospholipids are located inside the bilayer and form the hydrophobic phase.

Question 23

How is cholesterol arranged in the lipid bilayer, and what role does it play in the plasma membrane?

Answer 23

Cholesterol is placed in the middle slice of the phospholipid bilayer, with its hydroxyl group directed toward the “heads” of amphiphatic phospholipids. It is an important component of the plasma membrane in animal cells and serves as a precursor to steroid hormones like estrogens.

Question 24

What gives phospholipids their amphipathic properties?

Answer 24

Phospholipids have amphipathic properties due to the existence of two different domains in their structure: a hydrophilic head and a hydrophobic tail consisting of fatty acid chains.

Question 25

What is the fundamental driving force for lipid bilayer formation?

Answer 25

The hydrophobic effect, resulting from the amphipathic nature of phospholipids, is the fundamental driving force for lipid bilayer formation.

Question 26

How do lipids typically behave when in contact with water, and what is this phenomenon called?

Answer 26

Lipids spontaneously form a lipid monolayer rapidly and without any catalysts when in contact with water. This phenomenon is known as the hydrophobic effect.

Question 27

What is a covalent bond, and how is it formed?

Answer 27

A covalent bond is a chemical bond formed when atoms share electron pairs. For example, the O-H bond in the water molecule structure and C-C, and CH bonds in biological molecules are covalent bonds.

Question 28

What is the energy range of covalent bonds, and why is it considered high?

Answer 28

Covalent bonds have a high energy range, typically ranging from 300 to 4000 kJ/Mol. This high energy is a result of the shared electron pairs between involved atoms.

Question 29

How does the concept of covalent bonds relate to the hydrophobic effect?

Answer 29

Understanding covalent bonds is essential for explaining the hydrophobic effect, as it sets the stage for understanding interactions between atoms and molecules in the context of hydrophobicity.

Question 30

How do non-covalent bonds compare to covalent bonds in terms of strength?

Answer 30

Non-covalent bonds are much weaker interactions, approximately 10-100 times weaker than covalent bonds, and they occur between atoms, molecules, molecular fragments, and ions.

Question 31

What are non-covalent bonds, and what distinguishes them from covalent bonds?

Answer 31

Non-covalent bonds refer to molecular interactions that do not involve the sharing of electrons, distinguishing them from covalent bonds.

Question 32

List three types of non-covalent bonds and provide examples.

Answer 32

Non-covalent bonds include electrostatic interactions, hydrogen bonds, and van der Waals forces, which collectively contribute to weaker molecular interactions.

Question 33

What characterizes electrostatic bonds, and what types of entities are involved in this interaction?

Answer 33

Electrostatic bonds are relatively strong non-covalent interactions between ions or charged molecules. Oppositely charged groups attract each other, while similarly charged groups repel each other.

Question 34

What defines a hydrogen bond, and which atoms are typically involved in this weak non-covalent force?

Answer 34

A hydrogen bond is a weak non-covalent force between a positively charged hydrogen atom and negatively charged atoms, such as oxygen, nitrogen, or fluorine, in other chemical groups.