Cells Alive 2

Question 1

Describe the structure of the mitochondria

Answer 1

-Organelles bound by a double membrane - inner and outer
-Inner membrane space forms cristae
-Space between membranes is intermembrane space
-Inside of mitochondrion is mitochondrial matrix

Question 2

What happens when the amino group is removed?

Answer 2

Amino group becomes toxic therefore ammonia has to be converted and excreted:
*Ammonia converted to urea (in mammals, amphibians and sharks)
*Ammonia converted to uric acid (in birds, reptiles and insects)
* Ammonia is excreted directly (fish)

Question 3

How is an electrochemical gradient created during oxidative phosphorylation?

Answer 3

-Transfer of electrons from lower to higher affinity is energetically favourable
-The energy released is used to pump H+ into the inter-membrane space
-Pumping of H+ generates an electrochemical gradient across the inner mitochondrial membrane

Question 4

How does ATP store and release energy?

Answer 4

Energy is:
-Stored in the high-energy bonds between the three phosphate groups
-Released by hydrolysis of the phosphoanhydride bonds

Question 5

Where does glycolysis occur?

Answer 5

In the cytoplasm of the cell

Question 6

Where does β-oxidation occur?

Answer 6

In the mitochondrial matrix

Question 7

Where does the citric acid cycle occur?

Answer 7

In the mitochondrial matrix,

Question 8

Where is the electron transport chain and ATP Synthase found?

Answer 8

Located on the inner mitochondrial membrane

Question 9

Why do electrons pass down the ETC?

Answer 9

There are 4 complexes in the ETC
Each has a higher redox potential than the last (a greater affinity for electrons) therefore it is energetically favourable

Question 10

What is meant by an electrochemical gradient

Answer 10

The combined force driving ions across a cell membrane, resulting from both a difference in ion concentration (chemical gradient) and a difference in electrical charge (electrical gradient) on either side of the membrane

Energy released during the movement of electrons in the ETC is used to pump H+ into the intermembrane space
Pumping of H+ generates an electrochemical gradient

Question 11

In what way is the electrochemical gradient linked to ATP synthesis?

Answer 11

ATP synthase is the 5th protein complex in the inner membrane, electrons flow from complex IV into ATP synthase
Electrons flow through, enzymatic arm rotates, ATP is formed.

Question 12

How is the outer membrane adapted to the movement of molecules?

Answer 12

Contains large pores made of proteins called PORINS = permeable to certain sized molecules

Question 13

Are there any molecules that diffuse freely across membranes?

Answer 13

Gases such as oxygen and carbon dioxide, diffuse down their respective concentration gradients

Question 14

How is ATP transported/exported out of the matrix?

Answer 14

Co-transported in opposite direction to ADP, using the charge gradient and an antiporter

Question 15

What is an antiporter?

Answer 15

A membrane protein that moves two or more different molecules or ions across a cell membrane in OPPOSITE directions

Question 16

What is a symporter?

Answer 16

A membrane protein that transports two or more different molecules/ions across a cell membrane in the SAME direction

Question 17

Give two examples of molecules that are co-transported via a symporter

Answer 17

Pyruvate and inorganic phosphate, into the matrix

Question 18

What is endosymbiosis?

Answer 18

Mitochondria are believed to have evolved from an engulfed aerobic bacterium (specifically, an α-proteobacterium) that formed a symbiotic relationship with the host cell, eventually becoming a permanent organelle.

Question 19

What is the mitochondrial stress response (UPRmt)?

Answer 19

A protective cellular pathway that activates when mitochondria accumulate misfolded proteins or experience other stresses
Activates a cascade of protein-protein interactions within the cell
Involves communication between nucleus and mitochondria