Quiz 2

Question 1

What is the need for cells to have a selective barrier?

Answer 1

To separate themselves from the outside environment.

Question 2

Provide a definition for ‘lipid.’

Answer 2

Lipids are organic compounds that are hydrophobic or amphipathic in nature.

Question 3

Why is the electronegativity of carbon and hydrogen relevant to the behavior of lipids in water?

Answer 3

They share electrons equally in covalent bonds, affecting their interaction with water.

Question 4

Describe the general structure of a fatty acid.

Answer 4

A long hydrocarbon chain with a carboxylic acid group at one end.

Question 5

What is the difference in chemical bonding between saturated and unsaturated fatty acids?

Answer 5

Saturated fatty acids have single bonds, while unsaturated fatty acids have one or more double bonds.

Question 6

How does the saturation level of fatty acids affect melting temperatures?

Answer 6

More saturated fatty acids have higher melting temperatures due to stronger Van der Waals interactions.

Question 7

What is the primary biological role of fats?

Answer 7

Energy storage.

Question 8

What are the four components that make up a fat?

Answer 8

• Glycerol
• Fatty acids
• Ester bonds
• Hydrophobic properties

Question 9

How are fats different from phospholipids?

Answer 9

Fats are primarily for energy storage, while phospholipids form cell membranes.

Question 10

What are the five components that make up a phospholipid?

Answer 10

• Glycerol
• Two fatty acids
• Phosphate group
• Alcohol
• Amphipathic properties

Question 11

What does ‘amphipathic’ mean?

Answer 11

Having both hydrophilic and hydrophobic parts.

Question 12

Which components of a phospholipid interact with water?

Answer 12

The phosphate group and alcohol.

Question 13

Which components of a phospholipid do not interact with water?

Answer 13

The fatty acid tails.

Question 14

How does the hydrophobic effect lead to the formation of lipid bilayers?

Answer 14

Phospholipids spontaneously organize in water to minimize hydrophobic interactions.

Question 15

What drives the hydrophobic effect?

Answer 15

The entropy of water molecules.

Question 16

What types of molecules have high permeability through cell membranes?

Answer 16

• Small nonpolar molecules
• Hydrophobic molecules
• Uncharged polar molecules

Question 17

What types of molecules have low permeability through cell membranes?

Answer 17

• Large polar molecules
• Ions

Question 18

What is the relationship between fatty acid tail length and membrane permeability?

Answer 18

Longer and more saturated tails decrease permeability and fluidity.

Question 19

How does cholesterol affect membrane permeability?

Answer 19

Cholesterol fills gaps created by kinked lipid tails, reducing permeability.

Question 20

What is meant by membrane fluidity?

Answer 20

The ability of membrane components to move laterally within the layer.

Question 21

Does increasing temperature increase or decrease the fluidity of membranes?

Answer 21

Increase.

Question 22

What is diffusion?

Answer 22

The movement of solutes from an area of higher concentration to lower concentration, driven by entropy.

Question 23

In which direction will a solute move if there is a higher concentration outside the cell?

Answer 23

It will move inside the cell.

Question 24

Will there be net movement when solute concentrations are equal on both sides?

Answer 24

No, because the movement in both directions balances out.

Question 25

What is osmosis?

Answer 25

The movement of water across a semipermeable membrane driven by solute concentration.

Question 26

What does it mean for a cell to be in a hypertonic solution?

Answer 26

Water will move out of the cell, causing it to shrink.

Question 27

What does it mean for a cell to be in a hypotonic solution?

Answer 27

Water will move into the cell, causing it to swell.

Question 28

What does it mean for a cell to be in an isotonic solution?

Answer 28

Water movement is balanced, and the cell size remains constant.

Question 29

What is an integral membrane protein?

Answer 29

A protein that spans the membrane, with hydrophobic amino acids facing the lipid bilayer.

Question 30

What are peripheral membrane proteins?

Answer 30

Proteins that are attached to the exterior or interior surfaces of the membrane.

Question 31

Why are carbohydrates attached to proteins and lipids on the plasma membrane?

Answer 31

To identify cell types and serve as attachment sites for viruses.

Question 32

Explain the fluid mosaic model.

Answer 32

A model describing the structure of cell membranes as a mosaic of diverse protein molecules in a fluid phospholipid bilayer.

Question 33

How do detergents interact with membranes?

Answer 33

Detergents are amphipathic and can disrupt membranes and solubilize proteins.

Question 34

How can cells transport solutes that cannot cross membranes on their own?

Answer 34

Through transport proteins or channels.

Question 35

What is the difference between diffusion and facilitated diffusion?

Answer 35

Facilitated diffusion requires transport proteins, while diffusion does not.

Question 36

Describe the general structure of a channel protein.

Answer 36

A protein that forms a pore through the membrane, allowing specific solutes to pass.

Question 37

What types of amino acid properties are found on the membrane-facing side of a channel protein?

Answer 37

Hydrophobic properties.

Question 38

What types of amino acid properties are found on the channel-facing side of a channel protein?

Answer 38

Hydrophilic properties.

Question 39

What two features of a channel can make it selective for specific solutes?

Answer 39

* Size of the channel * Charge of the channel

Question 40

What is channel gating?

Answer 40

The process of opening or closing a channel in response to a signal.

Question 41

What is an example of something that can control channel gating?

Answer 41

Ligand binding.

Question 42

What does protein conformational change mean?

Answer 42

A change in the shape of a protein that can affect its function.

Question 43

How are protein conformational changes involved in the transport process of a carrier protein?

Answer 43

They allow the protein to transport solutes across the membrane.

Question 44

What is the sodium-potassium pump?

Answer 44

A primary active transporter that uses ATP to move sodium out and potassium into the cell.

Question 45

Describe the steps in the sodium-potassium pump process.

Answer 45

* ATP binds to the pump * Sodium is transported out * Conformational change occurs * Potassium is transported in

Question 46

What is the sodium-glucose symporter?

Answer 46

A secondary active transporter that uses the sodium gradient to transport glucose into the cell.

Question 47

What is the source of energy for secondary active transporters?

Answer 47

The electrochemical gradient established by primary active transport.

Question 48

How does active transport establish different concentrations of ions?

Answer 48

By pumping ions against their gradients, creating a potential for rapid ion movement.