Week 4: Introduction To Organelles

Question 1

What are organelles?

Answer 1

Functionally distinct membrane-bound compartments within eukaryotic cells

Organelles include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, endosomes, and peroxisomes.

Question 2

What is the primary function of the nucleus?

Answer 2

DNA and RNA synthesis

Question 3

What is the role of mitochondria?

Answer 3

Energy production - ATP

Question 4

What are the main functions of the endoplasmic reticulum (ER)?

Answer 4

Protein synthesis, lipid production, Ca²⁺ storage

The ER is divided into rough ER (with ribosomes) and smooth ER (without ribosomes).

Question 5

What does the Golgi apparatus do?

Answer 5

Modifies proteins and lipids from the ER and transfers them to other organelles

Question 6

What is the function of lysosomes?

Answer 6

Digestion of unwanted cell organelles and other substances

Question 7

What are peroxisomes responsible for?

Answer 7

Oxidative reactions and breaking down toxins

Question 8

What is the role of the plasma membrane?

Answer 8

Maintains cell integrity and has distinct proteins and lipids

Question 9

Why do we have intracellular compartments?

Answer 9

To isolate distinct functions and chemistry, and allow for organization and sorting of materials

Question 10

How do proteins get targeted to organelles?

Answer 10

Using sorting signals, which are amino acid sequences that indicate where a protein should go

Question 11

What are the three types of transport for proteins between compartments?

Answer 11

• Gated
• Transmembrane
• Vesicular

Question 12

What is gated transport?

Answer 12

Transport between nucleus and cytosol through nuclear pore complexes

Question 13

What is transmembrane transport?

Answer 13

Transport of membrane-bound proteins from the cytosol across a membrane into the organelle

Question 14

What is vesicular transport?

Answer 14

Membrane-enclosed transport of proteins from one organelle to another

Question 15

What is co-translational import?

Answer 15

Import of proteins into the ER while they are still being synthesized in the cytosol

Question 16

What is post-translational import?

Answer 16

Import of proteins into the ER after they have been fully synthesized in the cytosol

Question 17

What is the function of signal recognition particle (SRP)?

Answer 17

Directs the mRNA/ribosome/protein complex to the rough ER membrane if a signaling motif is present

Question 18

What is glycosylation in the context of protein synthesis?

Answer 18

The addition of N-linked oligosaccharides to proteins, resulting in glycoproteins

Question 19

What is the importance of glycosylation?

Answer 19

Quality control and acting as ligands for certain receptors

Question 20

What are the protein translocators in mitochondria?

Answer 20

• TOM complex (outer membrane)
• TIM complexes (inner membrane)
• OXA complex

Question 21

What is the double membrane problem in mitochondria?

Answer 21

Proteins must cross one or both membranes to be imported into mitochondria

Question 22

What is the common theme in membrane spanning proteins?

Answer 22

Different types of signal sequences are involved in their insertion into membranes

Question 23

What is a stop-transfer sequence?

Answer 23

An internal sequence that stops the threading of a protein across a membrane

Question 24

Fill in the blank: Cellular compartments are called ______.

Answer 24

[organelles]

Question 25

True or False: All proteins destined for organelles are synthesized in the cytosol.

Answer 25

True