B2.2 Organelles and Compartmentalization

Question 1

lol

Answer 1

Lol

Question 2

Which cell structures are not organelles?

Answer 2

Cell walls (extracellular), Cytoplasm (diverse functions), Cytoskeleton (extensive structure, not discrete)

Question 3

How does the nuclear membrane aid in protein synthesis in eukaryotic cells?

Answer 3

It ensures that post-transcriptional modification is completed before mRNA exits the nucleus for translation.

Question 4

What are the advantages of compartmentalization for lysosomes?

Answer 4

• Concentrated enzymes and substrates, faster enzyme activity.
• Ideal level of pH for organelle’s function
• Incompatible biochemical processes can be kept separate.

Question 5

What is an example of incompatible biochemical processes between lysosomes and cells?

Answer 5

Hydrolytic enzymes that digest proteins and other macromolecules would digest much of a cell if not confined within a membrane.

Question 6

What’s the size of mitochondria?

Answer 6

1-2 micrometers

Question 7

What does the outer mitochondrial membrane do?

Answer 7

It separates the content of the mitochondrion from the rest of the cell and maintains the ideal conditions for aerobic respiration.

Question 8

What does the inner mitochondrial membrane do?

Answer 8

Contains electron transport chains and ATP synthase, which together produce ATP by chemiosmosis.

Question 9

What do cristae, or projections in the inner mitochondrial membrane do?

Answer 9

Increase surface area available for ATP production.

Question 10

Mitochondrial inter membrane space function:

Answer 10

Its small space allows high proton concentration to rapidly develop when protons are pumped into electron transport chains.

Question 11

Mitochondrial matrix function:

Answer 11

Contains high concentrations of enzymes and substrates that allow the Krebs cycle and link reaction to take place.

Question 12

Mitochondrial naked DNA and 70s ribosomes function:

Answer 12

Allow the mitochondrion to carry out protein synthesis.

Question 13

List the structures of a chloroplast:

Answer 13

1) outer membrane
2) Inner membrane
3) stroma
4) Grana
5) Thylakoid membranes and spaces
6) Store of starch
7) Naked DNA Loop
8) 70s ribosomes

Question 14

What do thylakoid membranes do?

Answer 14

• Contains photosystems, electron carriers and ATP synthase needed for light-dependent reactions of photosynthesis.

Question 15

What are grana?

Answer 15

Stacks of thylakoids, give a total surface area of membrane for the light-dependent stage of respiration.

Question 16

Thylakoid spaces - Function:

Answer 16

• Very small volume creates a high proton concentration builds up after the few photons of light have been absorbed.

Question 17

DNA and 70s ribosomes allow mitochondrion to…

Answer 17

synthesize their own proteins

Question 18

Stroma - Function:

Answer 18

High concentration of rubisco/other enzymes and substrates for light-independent stage of photosynthesis (Calvin cycle).

Question 19

What does the chloroplast envelope (inner and outer membrane) do?

Answer 19

It creates a compartment with optimal conditions for photosynthesis.

Question 20

What advantages does a double nuclear membrane have?

Answer 20

1) nuclear pores can be formed by combining inner and outer membrane, needed for moving mRNA and ribosomes.
2) it can easily break up into vesicles during mitosis and meiosis, releasing the chromos so that they can move within the cell, they move to the poles where they are used to construct more nuclear membranes.

Question 21

Outline the structure of the Golgi apparatus:

Answer 21

A stack of flattened membrane-bound sacs in the cytoplasm of the cell.

Question 22

How are polypeptides modified and packaged in the Golgi apparatus?

Answer 22

1) Arrive in vesicles which fuse with the cisterna from the cis side.
2) Trafficked from cisterna to cisterna until they reach the trans side
3) Enzymes in each cisterna modify them by adding non-amino acid structures/cutting/crosslinking
4) Vesicles bud off from the cisterna on the trans side and carry the protein to the plasma membrane or elsewhere.

Question 23

What do free ribosomes do?

Answer 23

Synthesize proteins that are released into the cytoplasm, where they can perform their functions.

Question 24

What do ribosomes bound to the rER do?

Answer 24

Make proteins for transport to other organelles through modification by the Golgi apparatus then Exocytosis.

Question 25

Clathrin

Answer 25

A three legged protein that can be assembled to form a spherical cage.

Question 26

What are clathrin cages used for?

Answer 26

To pull a patch of membrane inwards from the plasma membrane until a vesicle is formed.