Biological Membranes

Question 1

Give the three roles of membranes

Answer 1

• Act as partially/selectively permeable membrane
• Sites of chemical reaction
• Site of cell communication and signalling

Question 2

What 3 things does a membrane act as a membrane BETWEEN?

Answer 2

• Cell and its Environment
• Organelle and
  surrounding cytoplasm
• Within Organelles

Question 3

Give the 4 main components of the fluid mosaic model

Answer 3

• Phospholipids
• Cholesterol
• Proteins
• Glycoproteins

Question 4

What 3 types of proteins are present in the cell membrane?

Answer 4

• Intrinsic
• Extrinsic
• Cross-membrane channel
  proteins

Question 5

What effect does high temperature have on membrane structure?

Answer 5

High temp denatures proteins and glycoproteins, reducing their ability to control transport of molecules across membrane
- Membrane is more permeable

Question 6

In which 4 ways can substances move across the membrane by?

Answer 6

• Diffusion
• Osmosis
• Facilitated diffusion
• Active transport

Question 7

What is the definition of Diffusion?

Answer 7

Movement of molecules from an area of high concentration to an area of lower concentration

Question 8

At which point does diffusion stop?

Answer 8

When the concentrations of the two regions are equal

Question 9

Name 4 substances capable of diffusion across cell surface membranes

Answer 9

• Oxygen
• Carbon dioxide
• Steroids
• Glycerol

Question 10

What is the definition of Osmosis?

Answer 10

Diffusion of WATER MOLECULES from an area of HIGH WATER POTENTIAL to an area of LOW WATER POTENTIAL
(Through a partially permeable membranes)

Question 11

Give 3 molecules transported by facilitated diffusion?

Answer 11

• Glucose
• Fructose
• Many Ions

Question 12

Give the four steps involved in facilitated diffusion

Answer 12

• Glucose binds with transport proteins on cell surface
• Transport protein changes shape
• Glucose transported through membrane into cell
• Glucose detaches, protein reverts to original shape

Question 13

How does facilitated diffusion maintain a concentration gradient

Answer 13

• When glucose detaches from protein, glucose is immediately phosphorylated
• So glucose concentration remains low
• Concentration gradient maintained across membrane

Question 14

What is Active Transport?

Answer 14

Movement of ions/molecules against the concentration gradient

Question 15

What is the effect of placing cells in hyPOtonic solution?

Answer 15

• Water potential higher outside cell

- Water moves in by osmosis

Question 16

What is the effect of placing cells in Isotonic solution?

Answer 16

• Water potential in/outside of the cell are equal

- No net movement of water

Question 17

What is the effect of placing cells in hyPERtonic solution?

Answer 17

• Water potential lower outside cell
• Causes water to leave cell by osmosis
• Causes cell to become plasmolysed

Question 18

What is the role of Cholesterol in the membrane?

Answer 18

It gives the membrane stability