Mitochondria & Energy Storage

Question 1

What are the functions of the smooth endoplasmic reticulum?

Answer 1

Primarily synthesizes phospholipids and cholesterol, can make most lipids

Main calcium storage site in cell - regulates release into cytosol and recapture

Drug detox

Assists in glucose metabolism

Synthesizes steroid hormones

Question 2

What lipids are produced in the cytosol?

Answer 2

Synthesizes most fatty acids and triglycerides

Question 3

What lipids are produced in the mitochondria and peroxisomes?

Answer 3

Specific membrane lipids

Question 4

SER cisterns are ____ and branching and lack ____

Answer 4

Tubular
Ribosomes

Question 5

How does the SER synthesize membrane phospholipids?

Answer 5

Substrates in cytosol bind to lipid synthesizing enzymes in SER’s cytosolic monolayer

Newly made phospholipids are in cytosolic monolayer at first and then are moved to the lumen facing monolayer of SER

Question 6

Phospholipid Translocator Proteins that move phopholipids from cytosolic monolayer to the lumen facing monolayer of SER

Answer 6

Flippases and floppases

Question 7

What is the main flippase in SER?

Answer 7

Scramblase

Question 8

What phospholipids can scramblase move?

Answer 8

Choline-containing phospholipids

Question 9

Are the phospholipids symmetrical in SER membrane?

Answer 9

No! Asymmetry maintained after leaving SER

Question 10

How are phospholipids transferred from the SER to mitochondria or peroxisomes?

Answer 10

Phospholipid transfer proteins

Question 11

What phospholipids does mitochondria synthesize?

Answer 11

Cardiolipin

Question 12

What glycerolphospholipid do peroxisomes produce?

Answer 12

Plasmalogens

Question 13

What other lipids are assembled in SER? Where are they sent?

Answer 13

Glycolipids - send to cis-Golig in a vesicle

Cholesterol and ceramides sent to RER via lateral membrane transfer and then to Golgi via a vesicle

Question 13

What direction do lipids travel through the Golgi?

Answer 13

cis to trans direction

Question 14

Is the SER acidophilic or basophilic? Can you see it in LM?

Answer 14

Acidophilic. Cannot see it in LM but it contributes to acidophilic cytoplasm

Question 15

Glycogenolysis - SER function

Answer 15

Enzymatic breakdown of glycogen - enzyme on lumen side of SER

Question 16

Gluconeogenesis - SER function

Answer 16

Supplies glucose during fasting. Enzymes on lumen side of SER

Question 17

Why does SER function in drug detox?

Answer 17

Makes enzymes that metabolize ethanol and barbiturates on lumen side on SER

Question 18

Barbiturates

Answer 18

Depressant drug. Used to treat seizures, migraines, or insomnia.

Question 19

How does the SER participate in tolerance?

Answer 19

Prolonged alcohol or drug use can lead to tolerance, which increases SER volume.

More SER = more enzymes and faster metabolism of ethanol and barbiturates. Need more SER to get same effect

Question 20

How do cells create energy in the form of ATP? What are the main substrates?

Answer 20

Cellular Respiration. Substrates are simple sugars and lipids.

Question 21

What are the main functions of mitochondria?

Answer 21

Breakdown short, medium, and long fatty acids via Beta-oxidation

Produce most of cell’s ATP via aerobic cellular respiration

Decides whether cell lives or dies

Temporary storage, release, and recapture of calcium

Question 22

What are some characteristics of mitochondria? (location, number, changing?)

Answer 22

Located all throughout cell
Vary in number depending on the cell type
Number of mitochondria is always changing

Question 23

Describe the structure of mitochondria

Answer 23

Outer mitochondrial Membrane

Intermembranous membrane

Inner mitochondrial membrane

Matrix space

Question 24

What are the characteristics of the outer mitochondrial membrane?

Answer 24

High protein content Porins form channels that permit water soluble molecules to cross Has proteins that synthesize mitochondrion specific lipids, metabolize fatty acids, and act as receptors for proteins heading to intermembranous space

Question 25

What are the characteristics of the intermembranous space?

Answer 25

Contents are similar to cytosol Contains enzymes like cytochrome c

Question 26

Cytochrome c

Answer 26

Enzyme located in the intermembranous space of the mitochondria and triggers the caspase cascade during apoptosis

Question 27

What are characteristics of the inner mitochondrial membrane?

Answer 27

75% protein --> very active membrane Involves protein complexes involved in ATP synthesis Forms numerous cristae that increase surface area for ATP synthesis and electron transfer chain

Question 28

What is the inner mitochondrial membrane impermeable to? Why?

Answer 28

Charged particles! Cardiolipin decreases the permeability Allows inner mitochondrial membrane to make hairpin turns

Question 29

Why is it important that cardiolipin decreases permeability of charged particles into the inner mitochondrial membrane?

Answer 29

Proton leak - when protons re-enter matrix without contributing to ATP synthesis

Question 30

Why is a proton leak bad for cells? When is it nonpathological?

Answer 30

Problematic --> wastes energy and creates reactive oxidative species that damage mitochondria and cell Nonpath --> Brown fat cells initiate proton leak via thermogenin which drives non-shivering thermogenesis

Question 31

What are the characteristic of the matrix space?

Answer 31

Viscous gel Contains mitochondrial genome, ribosomes, and electron dense matrix granules

Question 32

What do matrix granules in the mitochondria do?

Answer 32

Bind calcium and regulate concentration in the mitochondria.

Question 33

Are mitochondria acidophilic or basophilic?

Answer 33

Acidophilic - contribute to acidophilia of cytoplasm

Question 34

What would we use to locate mitochondria specific proteins?

Answer 34

Immunohistochemistry

Question 35

How does glycogen stain in H&E and PAS?

Answer 35

Glycogen does not stain in H&E and is PAS+

Question 36

Where is glycogen located?

Answer 36

Normally in cytosol in electron dense clusters

Question 37

Clusters of glycogen

Answer 37

Glycogen rosettes

Question 38

How do lipids stain in H&E and osmium?

Answer 38

Do not stain in H&E Stained directly by osmium stains

Question 39

What type of phospholipid layer do lipid droplets have?

Answer 39

Singler monolayer