Lecture 4

Question 1

What is a lipid composed of? (4•)

Answer 1

•Two fatty acid tails
•Glycerol backbone
•Phosphate
•Choline

Question 2

Lipids with bulky heads and a single hydrophobic fatty acid in a wedge shape form?

Answer 2

Spherical structures called micelles.

Question 3

What type of interactions do fatty acids form with each other?

Answer 3

Van der waals forces.

Question 4

Longer fatty acid tails implies?

Answer 4

More area that can have van der waals interactions and the phospholipids can be more mobile.

Question 5

Double bonding in fatty acids introduce? (2•)

Answer 5

•Bents in the fatty acid tails which •reduce tightness and enhance lipid mobility.

Question 6

What is the main role of cholesterol?

Answer 6

It controls the fluidity of the membrane depending on temperature.

Question 7

Integral membrane proteins?

Answer 7

Permanently associated with the cell membrane and cannot be separated without destroying the membrane.

Question 8

How does the cell remain homeostasis?

Answer 8

By being semipermeable.

Question 9

Semipermeability?

Answer 9

It means that the cell selects what goes in or out.

Question 10

How does permeability work?

Answer 10

•The hydrophobic interior of the lipid belayer prevents ions and charged polar molecules from moving across it.
•Small non-polar molecules and gasses (sometimes small uncharged polar molecules such as water) can freely move across the membrane.
•Protein channels and transporters can move ions, water, and nutrients that cannot cross the membrane alone.

Question 11

Passive transport?

Answer 11

It works by diffusion which is the net movement of molecules through the membrane depending on the concentration gradient. However, there are a few exceptions for this concentration phenomenon, like oxygen and carbon dioxide.

Question 12

Does the movement of molecules stop if there is no concentration gradient?

Answer 12

No, molecules still freely move.

Question 13

Facilitated diffusion?

Answer 13

When a molecule that requires a protein transporter to move across a concentration gradient, but its still random movement.

Question 14

a transporter channel?

Answer 14

An opening in which molecules can freely pass.

Question 15

Carrier transporter?

Answer 15

It binds to and then transports the specific molecule.

Question 16

Aquaporins?

Answer 16

Transporters for water molecules.

Question 17

Osmosis?

Answer 17

The net movement of a solvent inversely proportional to a solute across a semipermeable membrane.

Question 18

Osmotic pressure?

Answer 18

The pressure needed to halt osmosis.

Question 19

Active transport? (2•)

Answer 19

•The movement of molecules via ATP, molecules can go with or against a concentration gradient. The ATP “facilitated protein channel” called a pump.
•cells pump small ions to one side of the membrane resulting in a concentration gradient of charge.

Question 20

Electrical gradient?

Answer 20

A gradient with a change of energy across the membrane.

Question 21

Electrochemical gradient?

Answer 21

A gradient with a change of energy and concentration across a membrane.

Question 22

Secondary active transport?

Answer 22

Movement facilitated by protons, not ATP.

Question 23

Hypertonic solution?

Answer 23

A higher solute concentration outside than inside the cell; the cell shrinks.

Question 24

Hypotonic solution?

Answer 24

A lower solute concentration outside than inside the cell; the cell bursts.

Question 25

Isotonic?

Answer 25

The same solute and solvent concentrations.

Question 26

Turgor pressure?

Answer 26

Force exerted by water pressing against an object like the cell wall. It results by osmosis.

Question 27

What is the benefit of turgor pressure?

Answer 27

It can stop osmosis during a hypotonic solution as the cell wall increases that block the holes that facilitate permeability.

Question 28

In osmosis, water moves from a?

Answer 28

From a low solute concentration to a high solute concentration and from a high water concentration to a low water concentration.

Question 29

What would happen to the polar solvent if you add non-polar solute?

Answer 29

The non-polar solute would restrict rotation of the polar solvent because the non-polar solute would restrict PD bonds from occurring between polar solvent molecules.

Question 30

The hydrophobic effect?

Answer 30

Water molecules will loose entropy and will loose stability if hydrophobic molecules are more spread because the rotation of the water molecules will be more fixed.

Question 31

Why does water favour unsaturated lipids?

Answer 31

Because they are packed together less tightly making the membrane more fluid.

Question 32

What happens to free energy and entropy when the cell membrane begins forming?

Answer 32

Entropy of water increases while free energy decreases (is lost).

Question 33

What is the reason why ions have a hard time getting past the lipid bilayer?

Answer 33

Hydration shells: ions carry a huge quantity of water molecules that make them look so much bigger.