Lecture 4 - Plasma Membrane and Organelles

Question 1

What is the tree of life?

Answer 1

A tree that shows how everything is connected

Question 2

What must a cell do?

Answer 2

• manufacture cellular materials
• obtain raw materials
• remove waste
• generate the required energy
• control all the above

Question 3

What are organelles and what do they do?

Answer 3

Organelles are seperate compartments in the cell. Organelles provide special conditions for the different processes in the cell and keep incompatible processes apart. It also allows certain substance to be concentrated and packages substances for transport and export.

Question 4

Why is it important to seperate internal and external environments?

Answer 4

So the two different environments don’t leech into one another

Question 5

What does the plasma membrane do?

Answer 5

The plasma membrane acts as a boundary for the cell and provides special conditions within the cell

Question 6

How many membranes does mitochondria have?

Answer 6

2

Question 7

What organelles are found in both plant and animal cells?

Answer 7

Endoplasmic reticulum (ER)
Mitochondrion
Golgi apparatus
Nucleus

Question 8

What are organelles unique to plants?

Answer 8

Central vacuole

Chloroplast

Question 9

What organelle is unique to animal cell?

Answer 9

Lysosome

Question 10

Why is the cells maximum size limited?

Answer 10

Due to the plasma membrane

Question 11

What is the membrane made of?

Answer 11

A very thin continuous phospholipid bilayer

Question 12

Why does the membrane have to have some fluidity to it?

Answer 12

So we can change things as is needed for the cell

Question 13

What makes a membrane more fluid or viscous?

Answer 13

It depends on how tightly the phospholipids are packed together

Question 14

Describe unsaturated vs saturated hydrocarbon tails

Answer 14

Unsaturated tails prevent packing -Fluid

Saturated tails pack together - viscous

Question 15

What is a saturated and unsaturated hydrocarbon?

Answer 15

Saturated: only single carbon bonds
Unsaturated: contains double or triple carbon bonds

Question 16

What is the role of cholesterol in animal cells?

Answer 16

To sit and fill in the spaces between unsaturated carbon tails. This helps stabilise membrane fluidity and strengthen membrane.

Question 17

What are the different ways substance moves across membrane?

Answer 17

Diffusion
Facilitated diffusion 
Osmosis
Active transport
Co-transport

Question 18

What is passive diffusion?

Answer 18

Transport with no energy required

Question 19

What is active diffusion?

Answer 19

Transport with energy used

Question 20

What are forms of passive transport?

Answer 20

Diffusion
Facilitated diffusion
Osmosis

Question 21

What are forms of active transport?

Answer 21

Active transport

Co-transport

Question 22

Describe diffusion

Answer 22

Small hydrophobic molecules that can travel down their concentration gradient through the membrane without energy
(Steroid hormones and gasses)

Question 23

Describe facilitated diffusion

Answer 23

The use of membrane proteins called channels and carriers to allow movement of bigger molecules and hydrophilic molecules through the membrane down their concentration gradients without energy.

Question 24

Describe osmosis

Answer 24

A type of facilitated diffusion but for the movement of water through aquaporins in the cell membrane.

Question 25

What is the purpose of osmoregulation in cells?

Answer 25

To prevent swelling or shrinking of the cell under various conditions

Question 26

Describe active transport

Answer 26

Where molecules need to move against their concentration gradient which requires the use of transport proteins (carrier proteins that use energy)

Question 27

Describe co-transport

Answer 27

Indirect active transport where one substance is following its concentration gradient and another substance uses the power of that movement to go through and a pump is then used to get rid of the first substance.

Question 28

What are the rolls of membrane proteins?

Answer 28

Transporters
Signal transduction 
Cell recognition 
Intercellular joining
Linking cytoskeleton and ECM