Topic 3 - Membranes

Question 1

What are membranes composed of?

Answer 1

They are composed of lipid bi-layers.

Question 2

What are lipids?

Answer 2

They are water in-soluble (hydrophobic) molecules. They are composed of mostly carbons and hydrogens, which are known as hydrocarbons.

Question 3

What are the three kinds of biological lipids?

Answer 3

Sterols (cholesterol), phospholipids, triglycerides.

Question 4

What are fatty acids?

Answer 4

They are a long chain of carbon atoms with a carboxyl group at the end of the chain. They are hydrophobic. They vary in the number of carbons in the chain, thus they differ in length, and vary in presence and number of bonds.

Question 5

What are saturated fatty acids?

Answer 5

They have no triple and double bonds. They are all single bonds. They are found in animals mostly.

Question 6

What are unsaturated fatty acids?

Answer 6

They have double and triple bonds. They are found in plants mostly.

Question 7

What are triglycerides?

Answer 7

Three fatty acids bound to a glycerol anchor. They are energy storage molecules, and any of the chain can be either saturated or unsaturated.

Question 8

What are phospholipids?

Answer 8

They are two fatty acids bound to a glycerol anchor. The paler head is bound to glycerol via a phosphate group. Because the tail is hydrophobic and its head is hydrophilic (polar), it is amphipathic.

Question 9

What do phospholipids do naturally when placed in water?

Answer 9

They naturally for bilayers in the water as its head is hydrophilic and its tail is hydrophobic. Three types known as micelle, liposome, and phospholipid bilayers.

Question 10

What is the viscous phospholipid like?

Answer 10

It is stiffer and shorter, it is composed of saturated fatty acids. They have a higher melting point.

Question 11

What is the fluid phospholipid like?

Answer 11

It is fluid and spacious often due to its kink in the tails. It is composed of unsaturated fatty acids. It has a lower melting point.

Question 12

Why are biological membranes essential?

Answer 12

They compartmentalize the cell, separate in from out, and they create additional cellular regions.

Question 13

Membranes are…..

Answer 13

They are selectively permeable membranes, and they are also scaffolds for communication/chemical reactions.

Question 14

What are the two different different types of proteins?

Answer 14

There is integral and peripheral proteins. Integral goes through entire membrane whilst peripheral does not go through entirely.

Question 15

What are the four protein functions?

Answer 15

1. Transport Proteins
2. Enzymatic Activity (ETC)
3. Signal Transduction
4. Attachment/recognition

Question 16

What do sterols do in animal cells?

Answer 16

Gets inserted to…

1. Prevent freezing by preventing tails from packing too tightly.
2. Preventing melting by filling in gaps between phospholipids.

Question 17

How does membrane fluidity affect membrane permeability?

Answer 17

A more fluid membrane becomes too leaky and enables more molecules to go through.
A viscous membrane acts like a barrier and fewer solutes will pass.

Question 18

What is the order of permeability?

Answer 18

1. Non-polar (CO2, N2, O2)
2. Small, uncharged polar molecules (H2O, glycerol)
3. Large uncharged polar molecules (glucose, sucrose)
4. Ions b/c they are charged (K+, Cl-, Na+)

Question 19

What are aquaporins?

Answer 19

They are voltage-gated channel proteins that only has water go through. They are integral.

Question 20

Why do cells have selective permeability?

Answer 20

1. Cells in dynamic conditions where conditions are always fluctuating.
2. Maintain homeostasis.
3. Allows for concentration inside of cells be different than outside of cell.
4. Movement of molecules across membrane is well-controlled.

Question 21

What are the different types of movement of molecules in passive transport (do not require energy like ATP, relies on concentration gradients as energy)?

Answer 21

There is diffusion - simple and facilitated. Then there is osmosis too, which is focused on tonicity.

Question 22

When does osmosis occur?

Answer 22

When solutes cannot pass membrane but water molecules can. Water moves to where there is a high {[ ] molecules.

Question 23

What is diffusion?

Answer 23

It is the tendency of molecules to evenly distribute themselves; they, go from areas of high [ ] to areas of low [ ] so equilibrium is reached. Only works if solute is free to pass through bi-layer.

Question 24

What occurs at equilibrium?

Answer 24

1. Lowest energy state.

2. [ ] gradient is eliminated.

Question 25

What is tonicity?

Answer 25

Relative solute concentration difference between the cell and solution.

Question 26

What are the three categories of tonicity? Explain them.

Answer 26

1. Hypertonic - solution’s [ ] is greater than the cell’s; the water will leave cell and go out via osmosis.
2. Hypotonic - solution’s [ ] is less than the cell’s; the water will enter cell via osmosis.
3. Solution and cell has same concentration.

Question 27

What is included in passive again?

Answer 27

Passive transport includes simple and facilitated diffusion. And osmosis.

Question 28

What is simple diffusion?

Answer 28

It is small, non-polar molecules diffusing directly across the phospholipid bi-layer.

Question 29

What is facilitated diffusion?

Answer 29

It is the diffusion of solutes with the help of a proteins shaped like a tunnel. These are solutes that are large and polar and need help.

Question 30

What are the two types of proteins used in facilitated diffusion?

Answer 30

1. Channel Proteins - integral, aquaporins, voltage-gated

2. Carrier Proteins - integral, have a binding site and high affinity for certain molecules.

Question 31

Why do cells actively generate concentration gradients?

Answer 31

They often live in dilute environments; they need to concentrate molecules. To establish a [ ] gradient, they move solutes against a [ ] gradient, and they do this using energy.

Question 32

What are the two types active membrane transport?

Answer 32

1. Primary Active Transport

1. Secondary Active Transport

Question 33

What his primary active transport?

Answer 33

It is highly specific carrier proteins moving solutes against the [ ] gradient powered by ATP.

Question 34

What is secondary active transport?

Answer 34

Like primary, it is the movement of highly specific molecules by carrier proteins against [ ] gradient. It is powered by the energy released as the different solutes move down its gradient.

Question 35

What are the two types of secondary active transport?

Answer 35

Symporters (cotransport) - both driving ion and solute move the same direction.
Antiporters - in different directions.