Block 1 Lecture 9

Question 1

what is homeostasis in cells

Answer 1

their fabric is continually replaced but the overall structure in unchanging

Question 2

what is fission

Answer 2

when mitochondria split in 2

Question 3

how can mitochondria synthesize new proteins

Answer 3

mtDNA

Question 4

what is autophagy

Answer 4

process where worn out mitochondria are broken down

Question 5

what breaks down mitochondria

Answer 5

lysosomes

Question 6

what is the mechanism of autophagy

Answer 6

ER wraps around mitochondria, hydrolytic enzymes are introduced by fusion with lysosomal vesicle, the inside becomes acidic and mitochondria are digested

Question 7

what do mitochondria have their own of

Answer 7

DNA, ribosomes, tRNA

Question 8

where is DNA found in mitochondria

Answer 8

in the matrix in nucleoids

Question 9

what do nucleoids contain

Answer 9

4-5 copies of mtDNA

Question 10

where do most proteins in mitochondria come from

Answer 10

most are synthesized in cytosol and transported into mitochondrion

Question 11

what are TOMs

Answer 11

translocon of outer membrane

Question 12

what are TIMs

Answer 12

translocon of inner membrane

Question 13

how do proteins enter the mitochondria

Answer 13

• signal sequence happens at recognition
• inserted into membrane by TOM complex
• translocated into matrix
• cleavage by signal peptidase

Question 14

why is mtDNA maternal

Answer 14

because sperm cell has 100 mitochondria and oocyte has 100,000

Question 15

what is heteroplasmy

Answer 15

where a cell or tissue contains more than one type of mitochondrial genome

Question 16

what are the roles of mitochondria

Answer 16

• apoptosis
• heat production
• generation of reactive oxygen species
• calcium store
• role in some diseases

Question 17

what is the mechanism of apoptosis

Answer 17

1. opening of the permeability transition pore lets cytochrome C exit
2. cytochrome c activates apaf 1
3. apaf 1 activates caspases
4. intracellular proteases degrade cellular components

Question 18

what is the role of mitochondria in pancreatic B cells

Answer 18

serves as fuel sensors that link glucose exposure to insulin release

Question 19

what is the mechanism of mitchondrias effects in a pancreatic b cell

Answer 19

1. GLUT2 transporters introduce glucose and mitochondria cause increase of ATP:ADP ratio
2. K+ gate closure causes depolarization
3. voltage sensitive Ca2+ channels open
4. exocytosis of insulin granules to bloodstream

Question 20

what are uncoupling proteins

Answer 20

transmembrane proteins that decrease the proton gradient generated in oxidative phosphorylation

Question 21

what does uncoupling protein 1 do

Answer 21

• diverts energy from ATP generation to adoptive thermogenesis (Heat release)
• thermogeneic uncoupling occurs in response to overeating and cold
• decrease in mitochondrial production of damaging ROS

Question 22

what does uncoupling protein 2 do

Answer 22

• plays role inn metabolic adaptation to fasting regardless of weight
• cuases nonthermogenic uncoupling
• negative regulation of insulin secretion in pancreatic beta cell contributing significantly to type 2 diabetes induced by superoxide generation

Question 23

how is the 3 person baby made

Answer 23

female with mutant mitochondria has mitochondria discarded. her nuclear genome is fused with healthy mitochondria from another female to make an oocyte. a Male sperm fertilizes with the oocyte.