Cell Membrane (PPT 5-7) (U1)

Question 1

About how thick is the plasma membrane?

Answer 1

• Around only 8nm thick

nm= nanometers

Question 2

The function of the cell membrane is too…

Answer 2

• Isolate the cytoplasm from the external environment.
• Control what moves in and out of the cell.
• Cell to cell recognition.

Question 3

What cells have a cell wall?

Answer 3

• Bacteria
• Fungi
• Plant

Question 4

What is the membranes structure?

Hint= Fluid mosaic model

Answer 4

A double layer of phospholipids which are arranged with the hydrophobic tails facing inwards.

The double layer is fluid, with proteins floating within it.
Glycoproteins, glycolipids and cholesterol are an integral part of the membrane structure.

Question 5

Define Hydrophobic and Hydrophilic?

Answer 5

Hydrophobic= Water hating end

Hydrophilic= Water loving end.

Question 6

Why is it fluid mosaic?

Answer 6

Fluid because the components can move

Mosaic because the proteins embedded create a mosaic tile look.

Question 7

Phospholipids create a —– to —— soluble ——-. (Fill in the blanks).

Answer 7

1- barrier
2- water
3- molecules

Question 8

What type of molecules will Phospholipids let through the membrane?

Answer 8

• Lipids (as they are soluble in lipids)

- Hydrophobic molecules. (Water hating)

Question 9

—— molecules like —– cannot cross. (fill in the blank)

Answer 9

1- Large

2- Proteins.

Question 10

Are phospholipids stationary?

Answer 10

No, they can move and do so frequently.

Question 11

It is the phospholipids ability to —- that makes the membrane fluid. This is crucial because ————? (Finish the sentence)

Answer 11

1- move

2- it allows the embedded proteins to move where they are required.

Question 12

What does semi-permeable mean?

Answer 12

Semi-permeable means they allow some things through, but not all.

Question 13

What are the two types of membrane proteins?

Answer 13

1- Integral proteins (transverse the membrane)

2- Peripheral proteins (stuck on the inside or outside of the membrane)

Question 14

What is the structure and function of Integral proteins?

Answer 14

S= Generally span both phospholipid layers.

F= Transport of molecules. 
Signal transduction 
Cell to cell communication 
Joining of cells 
Anchorage (attachment to cytoskeleton).

Question 15

Glycoproteins and glycolipids are a… (finish the sentence)

Answer 15

Short chain of carbohydrates attached to proteins and lipids on extracellular side of the membrane.

Question 16

What is the structure and function of Cholesterol molecules?

Answer 16

S= Within the phospholipid layers, providing stability without affecting its fluidity.

F= Increase strength. Increase flexibility, Increase the rigidity of the membrane.
Assist with changing temperatures.

Question 17

Membranes are also found ——- ———– cells as part of the ——- of membranous ———. (Fill in the blank)

Answer 17

1- within
2- eukaryotic
3- structure
4- organelles

Question 18

What are the two ways substances are moved across the plasma membrane?

Answer 18

• Passive (not requiring energy)

- Active (energy requiring)

Question 19

Give examples of passive transport.

Answer 19

• Diffusion
• Facilitated diffusion
• Osmosis

Question 20

Give examples of active transport.

Answer 20

• Ion pumps

- Cytosis

Question 21

What is diffusion?

Answer 21

• Diffusion is a passive transport process, does not require energy.
• The movement of molecules from high concentration to low concentration. (Across the concentration gradient).

Question 22

Each type of diffusing molecule moves across….

Answer 22

Its own concentration gradient. The bigger this concentration, the faster the diffusion.

Question 23

What is facilitated diffusion?

Answer 23

• When a substance is aided across a membrane by selective protein channels.

Question 24

What is the upside to facilitated diffusion?`

Answer 24

• Transport is quicker than diffusion.
• The channels are specific for particular molecules.
• Does not require energy.

Question 25

What is the downside to facilitated diffusion?

Answer 25

• The channels can become saturated as the concentrations of the transported substances increase
• Transport of one substance is stopped by another as they compete for a channel.

Question 26

What is Osmosis?

Answer 26

• The net movement of water molecules across a partially permeable membrane from high to low concentration.

Question 27

What does Isotonic mean? (hint, Osmosis)

Answer 27

• No net movement of water between the cell and environment because the water concentrations are equal.

Question 28

What does Hypertonic mean? (hint, Osmosis)

Answer 28

• The solution has a higher concentration, water will leave the cell and enter the solution.

Question 29

What does Hypotonic mean? (hint, Osmosis)

Answer 29

• The solution has a lower concentration, water will leave the solution and enter the cell.

Question 30

What factors affect the diffusion and osmosis?

Answer 30

• Concentration gradient
• The diffusion distance
• Surface area
• Physical barriers

Question 31

If animal cells are placed in a hypotonic solution, what is their ultimate fate?
How is this different to plant cells

Answer 31

Animal cells do not have a cell wall. Meaning if they take in too much water the cell membrane will rupture.

• Plant cells have a cell wall to stop the cell from rupturing.

Question 32

What are implications?

Answer 32

Implications are anything that come into or out of the cell across the cell membrane.

Question 33

A small organism has a —— surface are.

As the organism becomes —–, its ——– —– decreases. (Fill in the blanks)

Answer 33

1- Large
2- larger
3- surface area

Question 34

So the —- size is limited by the ——– capability. (Fill in the blanks)

Answer 34

1- Cell

2- Diffusion

Question 35

Which method of transport do cells prefer to use and why?

Answer 35

Passive because it does not cost them energy (ATP)

Question 36

If a substance is going to be brought in against the concentration gradient, what transport type must be used?

Answer 36

Active

Question 37

What is active transport?

Answer 37

-Active transport is when materials are moved against their concentration gradient, this is why it requires energy (ATP).

Question 38

What is cytosis and what does it involve?

Answer 38

Cytosis is a form of active transport that involves the formation of membrane-bound vesicles.

Question 39

What does Endocytosis mean?

Answer 39

The incorporation of substances from outside the cell to inside the cell as membrane bound vesicles. (Coming in)

Question 40

What does Exocytotosis mean?

Answer 40

The release of substances from inside the cell to outside the cell. (Going out)

Question 41

How does Endocytosis take place?

Answer 41

The membrane folds in around the molecules to be transported into the cell.

Question 42

What are the two types of Endocytosis? And what are their roles?

Answer 42

1- Phagocytosis (the engulfment of soils particles).

2- Plnocytosis (the engulfment of liquid particles).

Question 43

The plasma membrane —– the ——- of ——— into and out of the cell

Answer 43

1- regulates
2- movement
3- molecules

Question 44

What factors effect the transport of molecules to and from cells?

Answer 44

• Size of molecule
• Type of molecule
• Effected by surface area of membrane
• Membrane thickness
• Concentration gradient
• Available protein carrier molecules.