Lecture 4: Plasma Membrane and Organelles

Question 1

What must a cell do?

Answer 1

Manufacture cellular materials
Obtain raw materials
Remove waste
Generate the required energy
Control all of the above

Question 2

What is an organelle?

Answer 2

Provide special conditions for specific processes.
Keep incompatible processes apart.
Allow specific substances to be concentrated
Form concentration gradients.
Package substances for transport or export.

Question 3

What organelles are only in plant cells?

Answer 3

Central Vacuole

Chloroplast

Question 4

What organelles are only in animal cells?

Answer 4

Lysosome

Question 5

What are all cellular membranes composed of?

Answer 5

Phospholipid Bilayer

Question 6

What stabilises membrane fluidity?

Answer 6

Cholesterol

Question 7

Passive Transport: Diffusion

Answer 7

Membranes are permeable to lipid soluble (hydrophobic) molecules such as steroid hormones and gasses.

They move down their concentration gradient and thus do not require energy

In contrast the membrane restricts movement of water soluble and charged molecules such as glucose ions and water

Question 8

Passive Transport: Facilitated Diffusion

Answer 8

Movement of hydrophilic molecules requires membrane proteins called channels and carriers

Aid the movement of specific substances down their concentration gradient

No energy required but some channels open or close in response to signals

Question 9

What are the channels called that help the movement of water across a cell membrane?

Answer 9

Aquaporins

Question 10

Movement from a high water (low solute) concentration to a low water (high solute) concentration is called?

Answer 10

Osmosis

Question 11

Active Transport:

Answer 11

Requires transport proteins which are carriers that use energy (ATP)

Move specific substances against
their concentration gradient.

Active transport allows a cell to
have an internal concentration of a
substance that is different from its
surroundings

May for example be higher inside
the cell than outside the cell

An example of this is the sodium potassium pump

Question 12

Movement across membranes: Co-transport

Answer 12

indirect active
transport

one substance
pumped across the
membrane

and its concentration
gradient used to
power the movement
of a second
substance against its
concentration
gradient

Question 13

What are the roles of membrane proteins? (4 Roles)

Answer 13

Signal Transduction
Cell Recognition
Intercellular Joining
Linking Cytoskeleton & Extracellular Matrix

Question 14

What is signal transduction?

Answer 14

Relay messages from the body (or environment) into the cell

“grow divide move make something die”

Question 15

What is cell recognition?

Answer 15

Often involves glycoproteins (proteins with added suagrs)

Question 16

What is intercellular joining?

Answer 16

some proteins form long lasting connections between cells

Question 17

what is linking cytoskeleton and extracellular matrix?

Answer 17

allows a cell to physically connect with protein structures outside the cell (extracellular matrix)

Question 18

Relaying messages from the external environment into the cell can be best described as:
A) cell recognition
B) intercellular joining
C) signal transduction
D) adhesion to ECM

Answer 18

c) signal tranduction