Chapter 3: The Plasma Membrane

Question 1

What is the purpose of the plasma membrane?

Answer 1

The cell membrane acts as a barrier and is semi-permeable, meaning it allows some substances through.

Question 2

What cells have a plasma membrane?

Answer 2

All cells have a cell membrane however, plant, bacteria, fungal and most algae cells also have a cell wall. Animal cells only have a cell membrane.

Question 3

The fundamental structure of the membrane is…

Answer 3

the phospholipid bilayer, which forms a stable barrier between two aqueous environments.

Question 4

What is the lipid bilayer composed of?

Answer 4

Phospholipids which can be represented by a head and two tails

Question 5

The Phosphate Head

Answer 5

The phosphate head is hydrophilic meaning they can absorb and attract water

Question 6

The Fatty Acid Tails

Answer 6

The tails are hydrophobic meaning they avoid water and are unable to absorb water

Question 7

What happens when these molecules form a bilayer?

Answer 7

The fatty acid tails turn inwards and face each other

Question 8

Membrane protein types

Answer 8

Transport proteins
Recognition proteins
Receptor proteins

Question 9

What is the purpose of transport proteins?

Answer 9

They act as passageways to allow certain molecules to pass through the membrane

Question 10

What is the purpose of recognition proteins?

Answer 10

They allow cells to communicate with each other

Question 11

What is the purpose of receptor proteins?

Answer 11

They bind hormones and other substances that can vary the activities of a cell essentially enabling them to respond to certain signals

Question 12

What is the difference between active and passive transport?

Answer 12

Active transport requires energy whereas passive doesn’t

Question 13

What are the two types of passive transport?

Answer 13

Diffusion and osmosis

Question 14

What is diffusion?

Answer 14

Diffusion is the movement of particles from an area of high concentration to and area of low concentration

Question 15

Concentration gradient definition

Answer 15

The difference in particle concentration between two regions

Question 16

When does diffusion stop?

Answer 16

When an equilibrium is achieved between the two regions, diffusion will stop

Question 17

What is facilitated diffusion?

Answer 17

Facilitated diffusion is when molecules are too large to diffuse with the use of the initial three proteins and require the assistance of specialised proteins

Question 18

What are the proteins required for facilitated diffusion?

Answer 18

Channel and carrier proteins

Question 19

How do carrier proteins assist diffusion?

Answer 19

They bind to specific molecules on one side of the membrane, change its shape and release the substance on the other side

Question 20

How do channel proteins assist diffusion?

Answer 20

They create a narrow pathway for specific ions to pass through

Question 21

What is osmosis?

Answer 21

Osmosis is a specific type of diffusion that relates to water and is the movement of water through a semi permeable membrane from areas of high concentration to areas of low concentration

Question 22

Isotonic definition

Answer 22

Equal amount of solute in both regions

Question 23

Hypotonic definition

Answer 23

When cells are surrounded by a solution with less solute concentration

Question 24

Hypertonic definition

Answer 24

When cells are surrounded by a solution with higher solute concentration

Question 25

What is haemolysis?

Answer 25

Haemolysis occurs when an animal cell is put into pure water and the particles diffuse into the cell causing it to swell and burst

Question 26

What is crenation?

Answer 26

Crenation is the shrinkage of an animal cell when placed in a solution with a surrounding hypertonic solution in comparison to the cellular cytoplasm

Question 27

When does active transport occur?

Answer 27

Active transport occurs when particles are needed in the high concentration area and must move in the opposite direction

Question 28

What happens when molecules are too large for active transport?

Answer 28

The use of macromolecules come to play as vesicles to allow these molecules to pass through

Question 29

What are the two types of vesicle tranpsort?

Answer 29

Endocytosis and exocytosis

Question 30

Endocytosis

Answer 30

This is the process of capturing a substance in the cell membrane from outside the cell and creating a membrane-bound sac for the substance to then be moved into the cytosol within

Question 31

What are the two main types of endocytosis?

Answer 31

Phagocytosis (cellular eating) or pinocytosis (cellular drinking).

Question 32

Exocytosis

Answer 32

The process of fusing the plasma membrane to release the substance outside the cell. This occurs to remove waste or release a protein