Topic 3: Membranes

Question 1

What do biological membranes do?

Answer 1

serve the purpose of creating selectively permeable barriers, or structures, that allow for selection of what is able to move across the membrane as well as separating and defining discrete functional spaces

Question 2

What are the 3 main molecules of membranes?

Answer 2

1. Phospholipids
2. Cholesterol
3. Proteins

Question 3

What is the purpose of the phospholipid bilayer?

Answer 3

Separate the extracellular and intracellular space

Question 4

A sulfolipid is a molecule similar to a phospholipid, but with a negatively charge sulfur-containing group replacing the head portion of the phospholipid. If a sulfolipid was in a plasma membrane…

Answer 4

The sulfur group would face the water and the tails would face the interior of the membrane because the sulfur would act just as the phosphorus and the tails would remain hydrophobic.

Question 5

What is the purpose of cholesterol?

Answer 5

Functions to temper the fluidity of a biological membrane toward a “middle ground.”

Question 6

Define permeability

Answer 6

the ability of solute to move across a membrane

Question 7

Increased concentrations of cholesterol among and between fatty acid tails in a membrane ____ the intramembrane space that ___ ____-____ molecules might be able to slip through

Answer 7

plug; small lipid-based

Question 8

What is the purpose of membrane proteins?

Answer 8

To facilitate movement of hydrophilic molecules across membranes

Question 9

What is an integral protein?

Answer 9

protein that is thoroughly embedded in the membranes and cannot be removed without changing the membrane’s structure

Question 10

What is a peripheral protein?

Answer 10

Proteins easily removed from the membrane without changing the overall membrane structure

Question 11

What are receptor proteins?

Answer 11

Proteins that may receive and bind to select incoming signals carrying messages to the cell

Question 12

What do receptor proteins do for the rest of the body?

Answer 12

provide cell recognition so that other cells know they are not foreign

Question 13

What are transport proteins?

Answer 13

Proteins that assist with the movement of small, hydrophilic molecules and ions across the membrane

Question 14

What are Glycoprotiens?

Answer 14

proteins that have a carbohydrate molecule attached which extend into the extracellular matrix

Question 15

What is glycocalyx and what is its importance?

Answer 15

fuzzy coating on the outside of glycoproteins and other carbohydrates attached to it that give a person’s cells the “identity” of belonging to that person’s body so the body’s immune defense cells will not attack the other somatic cells

Question 16

What kind of molecules are most likely to pass through the cell membrane?

Answer 16

Uncharged, small molecules (less than 4 atoms)

Question 17

How does water pass through a membrane?

Answer 17

via aquaporins

Question 18

Fluidity refers to the ability of a membrane to change ___ due to the ____ ____ of the molecules within the membrane

Answer 18

shape; unfixed nature

Question 19

When the environment gets colder, the fluidity of the membrane becomes…

Answer 19

more viscous

Question 20

When the environment becomes warmer, the fluidity of the membrane becomes more…

Answer 20

fluid

Question 21

The number of saturated fatty acids goes down as the environment gets warmer because…

Answer 21

saturated fates make a membrane more viscous

Question 22

The number of unsaturated fatty acids goes up as it gets warmer because…

Answer 22

unsaturated fats make the membrane less viscous

Question 23

How could trout maintain constant fluidity of membranes as water temperatures go from warmer to colder?

Answer 23

Add phospholipids with more unsaturated fatty acids to the membrane because unsaturated fatty acids add fluidity to the cell.

Question 24

Organisms that exhibit simple multicellularity…

Answer 24

are colonies of similar cells that do not have specialized tissues

Question 25

An advantage of unicellular living is that…

Answer 25

each cell retains the full set of abilities to survive and does not depend on other cells

Question 26

In the human retina, it was discovered that ions and cytoplasm can move through channels in the membrane that connect two cells. What allows this to happen?

Answer 26

Gap junctions

Question 27

Single celled and small multicellular organisms use ____ for transport, larger multicellular organisms transport molecules by _____.

Answer 27

Diffusion; both bulk flow and diffusion

Question 28

By definition, ____ pressures pull up liquids.

Answer 28

Negative

Question 29

What is an example of positive feedback in the body?

Answer 29

the formation of a blood clot causes more blood to clot until a cut is sealed

Question 30

In the negative feedback pathway, the ____ represents the part of the body that carries out the response, to bring the body condition (variable) back within a normal range.

Answer 30

Effector

Question 31

A mouse strives to maintain stable calcium concentrations in its blood. If the blood calcium concentrations decrease below a normal range, what would be the next step in the negative feedback pathway?

Answer 31

A sensor would detect the low calcium concentrations and send that information to the integrator.

Question 32

An organism that is a regulator for calcium concentration rather than a conformer…

Answer 32

would expend energy to remove excess calcium from the body, if needed.

Question 33

All cell-to-cell receptors